tag:theconversation.com,2011:/global/topics/seti-4217/articlesSETI – The Conversation2024-03-28T12:50:48Ztag:theconversation.com,2011:article/2257712024-03-28T12:50:48Z2024-03-28T12:50:48ZNASA’s mission to an ice-covered moon will contain a message between water worlds<figure><img src="https://images.theconversation.com/files/584594/original/file-20240326-30-7p4fl7.jpg?ixlib=rb-1.1.0&rect=7%2C8%2C1191%2C1212&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An illustration of the Europa Clipper spacecraft, which will head to Jupiter's moon Europa. </span> <span class="attribution"><a class="source" href="https://europa.nasa.gov/resources/173/europa-clipper-journey-to-an-ocean-world-poster/">NASA/JPL-Caltech</a></span></figcaption></figure><p>NASA’s <a href="https://europa.nasa.gov/">Europa Clipper</a> spacecraft, <a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-two-missions-are-sending-spacecraft-to-see-if-these-moons-could-support-life-203207">headed to Jupiter’s ice-covered moon</a> Europa in October 2024, will carry <a href="https://europa.nasa.gov/spacecraft/vault-plate/">a laser-etched message</a> that celebrates humanity’s connection to water. The message pays homage to past NASA missions that carried similar messages. </p>
<p>As <a href="https://meti.org/en/board/douglas-vakoch">the president</a> of <a href="https://meti.org/mission">Messaging Extraterrestrial Intelligence, or METI, International</a>, I helped design the message on Clipper with two fellow members of our board of directors: linguists <a href="https://meti.org/en/board/sheri-wells-jensen">Sheri Wells-Jensen</a> and <a href="https://longnow.org/people/laura/">Laura Buszard-Welcher</a>. METI International is a scientific organization dedicated to transmitting powerful radio messages to extraterrestrial life.</p>
<p>We collected audio recordings in 103 languages, and we decided how to <a href="https://europa.nasa.gov/spacecraft/vault-plate/#otp_waveform_generator">convert these into waveforms</a> that show these sounds visually. Colleagues from NASA etched these waveforms into the metal plate that shields the spacecraft’s sensitive electronics from <a href="https://www.astronomy.com/science/what-is-the-source-of-jupiters-radiation/">Jupiter’s harsh radiation</a>. </p>
<p>I also designed another part of the message that visually depicts the wavelengths of water’s constituents, because water is so important to the search for intelligent life in the universe. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8coGQ9kvBas?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA’s design for the Clipper message heading to Jupiter’s moon Europa.</span></figcaption>
</figure>
<p>Etching messages into spacecraft isn’t a new practice, and Clipper’s message fits into a decades-old tradition started by <a href="https://www.britannica.com/biography/Carl-Sagan">astronomer Carl Sagan</a>.</p>
<p>In 1972 and 1973, two Pioneer spacecraft headed to Jupiter and Saturn carrying metal plaques engraved with scientific and pictorial messages. In 1977, two <a href="https://theconversation.com/what-the-voyager-space-probes-can-teach-humanity-about-immortality-and-legacy-as-they-sail-through-space-for-trillions-of-years-177513">Voyager spacecraft</a> headed to Jupiter, Saturn, Uranus and Nepture bearing <a href="https://theconversation.com/voyager-golden-records-40-years-later-real-audience-was-always-here-on-earth-79886">gold-plated copper phonograph records</a>. These records contained tutorials in mathematics and chemistry, as well as music, photos and sounds of Earth and greetings in 55 languages.</p>
<h2>Water words</h2>
<p>As water is essential for life on Earth, searching for its presence elsewhere has been key to many NASA missions. Astronomers <a href="https://science.nasa.gov/jupiter/moons/europa/">suspect that Europa</a>, where Clipper is headed, <a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-two-missions-are-sending-spacecraft-to-see-if-these-moons-could-support-life-203207">has an ocean underneath its icy surface</a>, making it a prime candidate for the search for life in the outer solar system.</p>
<p>Part of the Clipper message features the word for water in 103 languages. We started with audio files collected online, but we then needed to analyze those and find an output that could be engraved on a metal plate. I ended up going back to some of the techniques I used in some of my early psycholinguistic research, where I explored how <a href="https://doi.org/10.1121/1.408973">emotions are encoded in speech</a>.</p>
<p>The 103 spoken words we recorded represent a global snapshot of the diversity of Earth’s languages. The outward-facing side of the Clipper plate shows the words as waveforms that track the varying intensity of sound as each word is spoken. </p>
<p>Each person whom we recorded saying the word “water” for the waveform had a connection to water. For example, the lawyer who contributed the word for water in Uzbek – “suv” – organizes an annual music festival in Uzbekistan to raise awareness of the desertification of the Aral Sea. </p>
<p>The native speaker of the Catalan water word – “aigua” – hunts <a href="https://theconversation.com/nasas-tess-spacecraft-is-finding-hundreds-of-exoplanets-and-is-poised-to-find-thousands-more-122104">for exoplanets</a>, discovering potentially habitable planets that orbit other stars. </p>
<h2>The Drake Equation</h2>
<p>Clipper’s message also pays homage to <a href="https://www.seti.org/frank-drake">astronomer Frank Drake</a>, the father of SETI – <a href="https://www.seti.org/">the Search for Extraterrestrial Intelligence</a> – by bearing <a href="https://www.seti.org/drake-equation-index">the Drake Equation</a>, his namesake formula. By drawing on scientific data, as well as some best guess hunches, the Drake Equation estimates the number of extraterrestrial civilizations in the galaxy currently sending messages into the cosmos. </p>
<p>By one <a href="https://www.britannica.com/science/Drake-equation">widely quoted estimate</a>, there are a tenth as many of these extraterrestrial civilizations as one’s average lifetime in years. If civilizations survive for a million years, for example, there should be about 100,000 in the galaxy. If they last only a century on average, scientists would estimate that about 10 exist.</p>
<p>Radio astronomers study the universe by examining the radiation that chemical elements in space give off. They spend much of their time mapping the distribution of the most abundant chemical in the universe – hydrogen.</p>
<p>Hydrogen emits radiation at a certain frequency called the <a href="http://www.setileague.org/askdr/hydrogen.htm">hydrogen line</a>, which radio telescopes can detect. During <a href="https://www.seti.org/project-ozma">Project Ozma</a>, the first modern-day SETI experiment, Drake looked for artificial signals at the same frequency, because he figured scientists on other worlds might recognize hydrogen as universally significant and broadcast signals at that frequency.</p>
<h2>The water hole</h2>
<p>As our team developed our water words message, I realized that the message would only make sense if it were discovered by someone already familiar with the contents inscribed on the plate. The Drake Equation would only make sense if someone already knew what each of the terms in the equation stood for. </p>
<p>The Europa Clipper will crash into Jupiter or one of its other moons, with <a href="https://www.space.com/europa-clipper-might-crash-into-ganymede">Ganymede or Callisto the leading candidates</a>. But if for some reason the mission changes and it survives that fate, then humans far in the future with a radically different cultural background and different language conventions may retrieve it millennia from now as an ancient artifact.</p>
<p>To ensure we had at least one part of the message that a distant future scientist might be able to understand, I also designed a pictorial representation of the same frequency that Drake used for Project Ozma: the hydrogen line. We engraved this on the Clipper plate, along with a frequency called the hydroxyl line.</p>
<p>When hydrogen (H+) and <a href="https://www.sciencedirect.com/topics/chemistry/hydroxyl">hydroxyl (OH-)</a> combine, they form water. Scientists call the range of frequencies between these lines the “<a href="http://www.setileague.org/general/waterhol.htm">water hole</a>.” The water hole represents the part of the radio spectrum where astronomers conducted the first SETI experiments.</p>
<p>We displayed the hydrogen and hydroxyl lines using their wavelengths in the Clipper message. The metal plate also has diagrams showing what hydrogen and hydroxyl look like at the atomic level. </p>
<p>We’re hoping that future chemists would recognize these chemical components as the ingredients of water. If they do, we will have succeeded in communicating at least a few core scientific concepts across time, space and language. </p>
<p>Waveforms let our team tie the messages on the two sides of the Clipper plate together. On the water words side, over a hundred words are depicted by their waveforms. On the other side, the wavelengths of hydrogen and hydroxyl – the constituents of water – are etched into the plate.</p>
<p>METI International funded the collection and curation of the water words, as well as my design of the hydrogen and hydroxyl lines, providing these to NASA at no cost.</p>
<p>While designing the message for the Europa Clipper, we got to reflect on the importance of water on Earth, and think about why astronomers feel so compelled to search for it beneath the icy crust of Jupiter’s moon Europa. The spacecraft is scheduled to enter Jupiter’s orbit in April 2030.</p><img src="https://counter.theconversation.com/content/225771/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Douglas Vakoch does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Europa Clipper will contain a plaque that celebrates humanity’s relationship with water and a decades-old tradition of searching for life outside Earth.Douglas Vakoch, President, METI International; Professor Emeritus, California Institute of Integral StudiesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2193962024-01-21T23:31:52Z2024-01-21T23:31:52ZThe Solar System used to have nine planets. Maybe it still does? Here’s your catch-up on space today<figure><img src="https://images.theconversation.com/files/566534/original/file-20231219-25-4dyqky.jpg?ixlib=rb-1.1.0&rect=31%2C15%2C5161%2C3230&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Some of us remember August 24 2006 like it was yesterday. It was the day Pluto got booted from the exclusive “planets club”.</p>
<p>I (Sara) was 11 years old, and my entire class began lunch break by passionately chanting “Pluto is a planet” in protest of the information we’d just received. It was a touching display. At the time, 11-year-old me was outraged – even somewhat inconsolable. Now, a much older me wholeheartedly accepts: Pluto is not a planet. </p>
<p>Similar to Sara, I (Rebecca) vividly remember Pluto’s re-designation to dwarf status. For me, it wasn’t so much that the celestial body had been reclassified. That is science, after all, and things change with new knowledge. Rather, what got to me was how the astronomy community handled the PR. </p>
<p>Even popular astronomers known for their public persona stumbled through mostly <a href="https://www.npr.org/templates/story/story.php?storyId=100145890">unapologetic explanations</a>. It was a missed opportunity. What was poorly communicated as a demotion was actually the discovery of new exciting members of our Solar System, of which <a href="https://www.loc.gov/everyday-mysteries/astronomy/item/why-is-pluto-no-longer-a-planet/">Pluto was the first</a>. </p>
<p>The good news is astronomers have better media support now, and there’s a lot of amazing science to catch up on. Let’s go over what you might have missed.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566535/original/file-20231219-19-8m96pv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pluto didn’t meet the criteria of a fully fledged planet. But there may still be a 9th planet in our Solar System waiting to be found.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>A throwback to a shocking demotion</h2>
<p>Pluto’s fate was almost certainly sealed the day Eris was discovered in 2005. Like Pluto, Eris orbits in the outskirts of our Solar System. Although it has a smaller radius than Pluto, it has <a href="https://astronomy.swin.edu.au/cosmos/m/Mass">more mass</a>.</p>
<p>Astronomers concluded that discovering objects such as Pluto and Eris would only become more common as our telescopes became more powerful. They were right. Today there are five known <a href="https://theconversation.com/new-dwarf-planet-in-the-outer-solar-system-62354">dwarf planets</a> in the Solar System. </p>
<p>The conditions for what classifies a “planet” as opposed to a “dwarf planet” were <a href="https://science.nasa.gov/solar-system/planets/what-is-a-planet/">set by the International Astronomical Union</a>. To cut a long story short, Pluto wasn’t being targeted back in 2006. It just didn’t meet all three criteria for a fully fledged planet:</p>
<ol>
<li>it must orbit a star (in our Solar System this would be the Sun)</li>
<li>it must be big enough that gravity has forced it into a spherical shape</li>
<li>it must be big enough that its own gravity has cleared away any other objects of a similar size near its orbit.</li>
</ol>
<p>The third criterion was Pluto’s downfall. It hasn’t cleared its neighbouring region of other objects. </p>
<p>So is our Solar System fated to have just eight planets? Not necessarily. There may be another one waiting to be found. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ive-always-wondered-why-are-the-stars-planets-and-moons-round-when-comets-and-asteroids-arent-160541">I've always wondered: why are the stars, planets and moons round, when comets and asteroids aren't?</a>
</strong>
</em>
</p>
<hr>
<h2>Is there a Planet Nine out there?</h2>
<p>With the discovery of new and distant dwarf planets, astronomers eventually realised the dwarf planets’ motions around the Sun didn’t quite add up. </p>
<p>We can use complicated <a href="https://www.caltech.edu/about/news/caltech-researchers-find-evidence-real-ninth-planet-49523">simulations in supercomputers</a> to model how gravitational interactions would play out in a complex environment such as our Solar System. </p>
<p>In 2016, California Institute of Technology astronomers Konstantin Batygin and Mike Brown concluded – after modelling the dwarf planets and their observed paths – that mathematically there ought be a ninth planet out there.</p>
<p>Their <a href="https://www.caltech.edu/about/news/caltech-researchers-find-evidence-real-ninth-planet-49523">modelling</a> determined this planet would have to be about ten times the mass of Earth, and located some 90 billion kilometres away from the Sun (about 15 times farther then Pluto). It’s a pretty bold claim, and some remain sceptical.</p>
<p>One might assume it’s easy to determine whether such a planet exists. Just point a telescope towards where you think it is and look, right? If we can see galaxies billions of light years away, shouldn’t we be able to spot a ninth planet in our own Solar System?</p>
<p>Well, the issue lies in how (not) bright this theoretical planet would be. Best estimates suggest it sits at the depth limit of Earth’s largest telescopes. In other words, it could be 600 times fainter than Pluto.</p>
<p>The other issue is we don’t know exactly where to look. Our Solar System is <em>really</em> big, and it would take a significant amount of time to cover the entire sky region in which Planet Nine might be hiding. To further complicate things, there’s only a small window each year during which conditions are just right for this search. </p>
<p>That isn’t stopping us from looking, though. In 2021, a team using the Atacama Cosmology Telescope (a millimetre-wave radio telescope) published the results from their <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ac2307">search for a ninth planet’s</a> movement in the outskirts of the Solar System. </p>
<p>While they weren’t able to confirm its existence, they provided ten candidates for further follow-up. We may only be a few years from knowing what lurks in the outskirts of our planetary neighbourhood.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566540/original/file-20231219-17-8m96pv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ACT sits at an altitude of 5,190 meters in Chile’s Atacama desert. Here, the lack of atmospheric water vapour helps to increase its accuracy.</span>
<span class="attribution"><a class="source" href="https://www.nist.gov/measuring-cosmos/atacama-cosmology-telescope">NIST/ACT Collaboration</a></span>
</figcaption>
</figure>
<h2>Finding exoplanets</h2>
<p>Even though we have telescopes that can reveal galaxies from the universe’s earliest years, we still can’t easily directly image planets outside of our Solar System, also called exoplanets. </p>
<p>The reason can be found in fundamental physics. Planets emit very dim red wavelengths of light, so we can only see them clearly when they’re reflecting the light of their star. The farther away a planet is from its star, the harder it is to see. </p>
<p>Astronomers knew they’d have to find other ways to look for planets in foreign star systems. Before Pluto was reclassified they had already detected the <a href="https://exoplanets.nasa.gov/resources/2084/greetings-from-your-first-exoplanet.">first exoplanet</a>, 51 Pegasi B, using a <a href="https://www.planetary.org/articles/color-shifting-stars-the-radial-velocity-method">radial velocity method</a>. </p>
<p>This gas giant world is large enough, and close enough to its star, that the gravitational tug of war between the two can be detected all the way from Earth. However, this method of discovery is tedious and challenging from Earth’s surface. </p>
<p>So astronomers came up with another way to find exoplanets: the transit method. When Mercury or Venus pass in front of the Sun, they block a small amount of the Sun’s light. With powerful telescopes, we can look for this phenomenon in distant star systems as well. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=619&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=619&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=619&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=778&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=778&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566539/original/file-20231219-15-rhodbm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=778&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In August, the TESS telescope took this snapshot of the Large Magellanic Cloud (right) and the bright star R Doradus (left).</span>
<span class="attribution"><span class="source">NASA/MIT/TESS</span></span>
</figcaption>
</figure>
<p>We do this via the <a href="https://science.nasa.gov/mission/kepler">Kepler</a> space telescope and the Transiting Exoplanet Survey Satellite (<a href="https://science.nasa.gov/mission/tess">TESS</a>). Both have observed tens of thousands of stars and discovered thousands of new planets – dozens of which are about the same size as Earth. </p>
<p>But these observatories can only tell us a planet’s size and distance from its star. They can’t tell us if a planet <a href="https://theconversation.com/do-aliens-exist-we-asked-five-experts-161811">might be hosting life</a>. For that we’d need the James Webb Space Telescope.</p>
<h2>Looking for life</h2>
<p>The James Webb Space Telescope (JWST) has just wrapped up its first year and a half of science. Among its many achievements is the detection of molecules in the atmospheres of exoplanets, a feat made possible by the transit method. </p>
<p>One of these exoplanets, WASP-17, is also known as a “hot Jupiter”. It seems to have been plucked from a page in a sci-fi novel, with evidence for <a href="https://webbtelescope.org/contents/media/images/2023/140/01HC3B0DZNEMRQT3KQ6X4ZMNN2">quartz nanocrystals</a> in its clouds. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/10-times-this-year-the-webb-telescope-blew-us-away-with-new-images-of-our-stunning-universe-194739">10 times this year the Webb telescope blew us away with new images of our stunning universe</a>
</strong>
</em>
</p>
<hr>
<p>Meanwhile, the <a href="https://exoplanets.nasa.gov/what-is-an-exoplanet/planet-types/super-earth/">super-Earth</a> <a href="https://www.nasa.gov/universe/exoplanets/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18-b/">K2-18b</a> (a Kepler find) shows signs of methane and carbon dioxide. But while such discoveries are amazing, the magic ingredient <a href="https://www.nhm.ac.uk/discover/eight-ingredients-life-in-space.html#:%7E:text=Liquid%20water%20is%20an%20essential,substances%20than%20most%20other%20liquids.">necessary for life</a> still eludes us: water vapour.</p>
<p>The field of planetary studies is evolving and 2024 looks promising. Maybe JWST will finally produce signs of water vapour in an exoplanet atmosphere. Who knows, we might even have a ninth planet surprise us all, filling the void left by Pluto. </p>
<p>Stay tuned for exciting science to come.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566536/original/file-20231219-21-vpjm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Small bodies on the very fringes of our Solar System are essentially invisible to us – but advanced new techniques and technologies are changing this.</span>
<span class="attribution"><span class="source">NASA/Jasmin Moghbeli</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/219396/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When most of us left school there were still 9 planets – but we’ve come a long way since Pluto’s demotion. Here’s what’s next on the space agenda.Sara Webb, Lecturer, Centre for Astrophysics and Supercomputing, Swinburne University of TechnologyRebecca Allen, Coordinator Swinburne Astronomy Online | Program Lead of Microgravity Experimentation, Space Technology and Industry Institute, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2186582023-12-06T15:53:37Z2023-12-06T15:53:37ZUFOs: how astronomers are searching the sky for alien probes near Earth<p>There has been increased interest in unidentified flying objects (UFOs) ever since the Pentagon’s <a href="https://www.dni.gov/files/ODNI/documents/assessments/Prelimary-Assessment-UAP-20210625.pdf">2021 report</a> revealed what appears to be anomalous objects in US airspace, dubbed unidentified aerial phenomena (UAP). Fast forward to 2023, and Nasa <a href="https://www.nasa.gov/news-release/update-nasa-shares-uap-independent-study-report-names-director/">has already formed a panel</a> to investigate the reports and <a href="https://www.nytimes.com/2023/09/14/science/nasa-ufo-uap-report.html">appointed a director </a> for UAP research. </p>
<p>A <a href="https://www.aaro.mil/">newly founded Pentagon desk</a> has also released <a href="https://globalnews.ca/news/9746110/metallic-flying-orbs-nasa-pentagon-panel-ufos-uaps/">footage of mysterious metallic orbs</a>. What is perhaps most remarkable is that David Grusch, a former intelligence officer, testified under oath before the US Congress, stating that he had interviewed around 40 people involved <a href="https://thedebrief.org/intelligence-officials-say-u-s-has-retrieved-non-human-craft/">in secret programmes dealing with crashed UFOs</a>.</p>
<p>I am interested in searching the sky for alien, physical objects which may one day tell us whether we are alone in the galaxy. Consider this: within our own Milky Way galaxy, there are 40 billion Earth-sized, potentially habitable planets. </p>
<p>Human ingenuity has enabled us to engineer and launch probes like Voyager and Pioneer, capable of reaching the closest stars. We’ve initiated efforts such as the <a href="https://breakthroughinitiatives.org/initiative/3">Breakthrough Starshot programme</a> which aims to reach nearby star Alpha Centauri in just a few decades by exploring innovative propulsion methods. <a href="https://www.nature.com/articles/nature02884">Sending a probe may be more economical</a> than sending out radio or laser communication if there is no need to hurry.</p>
<p>If humans can send a probe to another star, why couldn’t another civilisation send a probe to our Solar System? Such a probe could make it to the <a href="https://arxiv.org/abs/1808.07024">main asteroid belt</a> and <a href="https://earthsky.org/space/alien-lurker-probes-co-orbital-asteroids-earth/">lurk on an asteroid</a>. </p>
<p>Or, it could make its way to the Earth, entering our atmosphere. If observed, it would be branded as a “UFO”. A civilisation capable of producing and sending probes could dispatch millions of them on exploratory missions throughout our galaxy.</p>
<p>Some may argue that such probes could only exist if they adhere to the laws of physics and engineering as we understand them today. However, humanity is a relatively young civilisation, and our knowledge is constantly evolving. </p>
<p>While humans have dreamt of flying for millennia as we gazed at the skies, it has only been 120 years since the Wright brothers achieved the first powered flight. That’s about as long ago as Albert Einstein published his theory of special relativity.</p>
<p>Is it really so difficult to imagine that a civilisation that is hundreds of thousands years older than ours might have learned more about the laws of physics or developed <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7514271/">a few more engineering tricks</a>?</p>
<p>If a civilisation <a href="https://theconversation.com/seti-why-extraterrestrial-intelligence-is-more-likely-to-be-artificial-than-biological-169966">were to evolve into artificial intelligence (AI)</a>, it might survive for millions of years. This could mean it would casually regard slow to a neighbouring star as nothing more than a leisurely stroll.</p>
<p>That said, few astronomers felt impressed by the <a href="https://www.youtube.com/watch?v=rO_M0hLlJ-Q">US Navy videos</a> or government reports. We need significantly better evidence and data than what has been presented so far.</p>
<h2>Unveiling UFOs</h2>
<p>How can we test whether there are extra terrestrial probes near Earth, and whether they can be tied to the possible UFO phenomenon? There are many options. Analysing materials from potentially crashed UFOs could give irrefutable proof. This <a href="https://www.sciencedirect.com/science/article/abs/pii/S0376042121000907?fr=RR-2&ref=pdf_download&rr=8303a873ba1235b9">would require state-of-the-art techniques</a> to determine if these wrecks exhibit exotic or distinctly different characteristics of manufacture.</p>
<p>Obtaining such exotic samples, if they indeed exist, may prove challenging – they are rumoured to be <a href="https://nypost.com/2021/04/30/former-sen-harry-reid-thinks-lockheed-martin-may-have-ufo-fragments/">in the hands of private companies</a>. But <a href="https://www.democrats.senate.gov/newsroom/press-releases/schumer-rounds-introduce-new-legislation-to-declassify-government-records-related-to-unidentified-anomalous-phenomena-and-ufos_modeled-after-jfk-assassination-records-collection-act--as-an-amendment-to-ndaa">newly proposed legislation</a> might offer a solution to that problem in United States by mandating that all artificial materials from any non-human intelligence be surrendered to the US government.</p>
<p>In the projects I lead, we are searching for artificial non-human objects by <a href="https://www.sciencedirect.com/science/article/pii/S0094576522000480">looking for short light flashes</a> in the night sky. Short flashes typically occur when a flat, highly reflective surface — such as a mirror or glass — reflects sunlight. It could, however, also result from an artificial object emitting its own internal light.</p>
<p>Such short light flashes sometimes repeat and follow a straight line as the object tumbles in space during its orbit around the Earth. This is why satellites often appear as repeating light flashes in images. </p>
<p>Historical photographic plates taken before the launch of Sputnik 1 in 1957 <a href="https://earthsky.org/space/9-weird-transients-palomar-observatory-1950/">have revealed</a> the presence of nine light sources (transients) that appear and vanish within an hour in a small image, defying <a href="https://www.nature.com/articles/s41598-021-92162-7">astronomical explanations</a>. In some cases, the transient light sources <a href="https://arxiv.org/abs/2204.06091">are even aligned</a>, just like when short flashes come from moving objects. </p>
<figure class="align-center ">
<img alt="Image of the three disappearing stars." src="https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=234&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=234&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=234&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=294&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=294&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=294&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The three disappearing stars.</span>
<span class="attribution"><a class="source" href="https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad3422/7457759">[Edited, higher-resolution version of Fig 2 in paper by Solano et al. (2023)(https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad3422/7457759)]</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The <a href="https://www.universetoday.com/163820/in-1952-a-group-of-three-stars-vanished-astronomers-still-cant-find-them/">most recent finding</a> of this kind shows three bright stars in an image dated July 19, 1952 (coincidentally, the same time as the famous <a href="https://en.wikipedia.org/wiki/1952_Washington,_D.C.,_UFO_incident">Washington UFO flyovers</a>). The three stars were never seen again.</p>
<p>Searching for alien probes in the modern night sky presents a serious but necessary challenge. A new research programme, <a href="https://thedebrief.org/a-new-era-of-optical-seti-the-search-for-artificial-objects-of-non-human-origin/">known as ExoProbe</a>, searches for short light flashes from potential alien objects with the help of multiple telescopes. </p>
<p>To verify the authenticity of each flash, it must be observed in at least two different telescopes. Since these telescopes are separated by hundreds of kilometres, any light flash caused by an object within the inner Solar System enables the measurement of parallax — the apparent shift in the position of an object as seen from two different points — and the calculation of the distance to the object. </p>
<p>The ExoProbe project also uses its own methods to filter out light flashes from the millions of space debris fragments and thousands of satellites cluttering the sky. By adding a telescope taking real-time spectra (the wavelength distributions of the light) of the objects in a wide field, you can analyse the transients before they vanish into nothingness.</p>
<p>Finally, increasing the number of telescopes further enhances accuracy in measuring parallax and determining the actual three dimensional location of the object. Ultimately, the goal is to identify any potential alien object and bring it back to Earth for further study. </p>
<p>Some 60 years of searches for extraterrestrial civilisations in the radio frequencies have yielded no candidates whatsoever. We find ourselves at a moment in time when new paths must be explored. That means we can finally focus our attention closer to home. Regardless of the outcome, this journey is certainly an homage to our insatiable curiosity.</p><img src="https://counter.theconversation.com/content/218658/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Beatriz Villarroel receives funding from a private donor for the ExoProbe project.</span></em></p>Several scientific projects are aiming to investigate UFO sightings.Beatriz Villarroel, Assistant professor of Physics, Stockholm UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2185062023-12-05T12:39:02Z2023-12-05T12:39:02ZSeti: how we’re searching for alien life at previously unexplored frequencies<figure><img src="https://images.theconversation.com/files/563420/original/file-20231204-30-rxc98b.png?ixlib=rb-1.1.0&rect=26%2C98%2C2000%2C1814&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>Is there life beyond Earth? The question has turned out to be one of the hardest to answer in science. Despite the seemingly boundless expanse of the universe, which implies there’s potential for abundant life, the vast distances between stars render the search akin to locating a needle in a cosmic haystack.</p>
<p>The <a href="http://seti.berkeley.edu/.">Search for Extraterrestrial Intelligence (Seti)</a> constitutes a branch of astronomy dedicated to finding extraterrestrial life by searching for unusual signals, dubbed technosignatures. The identification of a technosignature wouldn’t just signify the existence of life, but specifically point to the presence of intelligent life using advanced technology.</p>
<p>That said, 60 years of searches have so far come up short. But now my colleagues at <a href="https://breakthroughinitiatives.org/">Breakthrough Listen</a> and I have <a href="https://www.tcd.ie/physics/news-events/news/2022/astrophysicists-scan-the-galaxy-for-signs-of-life/">started investigating</a> a previously unexplored range of frequencies. </p>
<p>Seti makes the assumption that extraterrestrial civilisations might rely on technology in a similar way to people on Earth, such as using cell phones, satellites or radar.</p>
<p>Since a significant portion of such technology generates signals that are prominently detectable in radio frequencies, focusing on these wavelengths serves as a logical starting point in the quest for potential extraterrestrial intelligence. </p>
<p>Previous technosignature surveys have included only the radio frequency band above 600 MHz, leaving lower frequencies virtually unexplored. That’s despite the fact that everyday communication services such as air traffic control, marine emergency broadcasting and FM radio stations all emit this type of low-frequency radiation on Earth.</p>
<p>The reason it hasn’t been explored is that telescopes that operate at these frequencies are rather new. And lower-frequency radio waves have less energy, meaning they can be more challenging to detect.</p>
<p>In our <a href="https://iopscience.iop.org/article/10.3847/1538-3881/acf9f5">concluded survey</a>, we ventured into these frequencies for the first time ever.</p>
<p>The <a href="https://www.ucl.ac.uk/astrophysics/research/cosmology/lofar-low-frequency-array#:%7E:text=The%20LOw%20Frequency%20ARray%20is,for%20a%20multi%2Duser%20operation.">Low Frequency Array (Lofar)</a> is the world’s most sensitive low-frequency telescope, operating from 10-250 MHz. It’s composed of 52 radio telescopes with more on the way, spread across Europe. These telescopes can reach a high resolution when used in unison. </p>
<figure class="align-center ">
<img alt="Radio telescope at Birr, Ireland." src="https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&rect=114%2C76%2C4993%2C2711&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Radio telescope at Birr, Ireland.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Our survey, however, only made use of two of these stations: <a href="https://lofar.ie/">one situated in Birr</a>, Ireland, and <a href="https://www.chalmers.se/en/infrastructure/oso/telescopes-and-instruments/radio-astronomy-facilities/lofar/">the other</a> in Onsala, Sweden. We surveyed 44 planets orbiting other stars than our Sun that had been identified by Nasa’s <a href="https://tess.mit.edu/">Transiting Exoplanet Survey Satellite</a>. Over the course of two summers, we scanned these planets at 110 to 190 MHz with our two telescopes.</p>
<p>Initially, this doesn’t seem like a large amount of targets, but low-frequency observation boasts a major advantage in having large fields of view compared with their higher-frequency siblings. That’s because the area of the sky covered decreases with higher frequencies. </p>
<p>In the case of Lofar, we covered 5.27 square degrees of the sky for each pointing of our telescopes. This culminated in 36,000 targets per telecope pointing – or more than 1,600,000 targets in total, when you check what other stars are nearby and include their planets as well.</p>
<h2>Interfering signals</h2>
<p>Searching for technosignatures from space introduces a significant challenge — the same technosignatures are ubiquitous on Earth. This presents an obstacle as the telescopes in these searches boast sensitivity levels that can detect signals, such as a phone call, from halfway across the Solar System. </p>
<p>Consequently, the data collected is inundated with thousands of signals originating from Earth, posing a considerable difficulty in isolating and identifying signals that could be of extraterrestrial origin. The need to sift through this extensive and noisy dataset adds a layer of complexity to the search.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=502&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=502&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=502&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=631&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=631&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=631&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Overview of the stars searched for technosignatures by Lofar in our Milky Way.</span>
<span class="attribution"><span class="source">Owen Johnson</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>We came up with an innovative approach to mitigating such radio frequency interference, called the “coincidence rejection” method. This takes into account the local radio emissions at each of our telescopes. For example, if I am using the telephone close to the telescope in Ireland to call my supervisor, that same call won’t appear in the data in Sweden, and vice versa (mainly because the telescope isn’t pointing in our direction, it’s pointing at an exoplanet candidate).</p>
<p>So, we decided to only include signatures in the dataset if they exhibited a simultaneous presence at both stations, suggesting they come from outside Earth.</p>
<p>In this way, we whittled down thousands of candidate signals to zero. This means we didn’t find any signs of intelligent life with our search, but we have only just started – and there are likely to be an enormous number of Earth-like planets out there. Knowing that the coincidence rejection method works with a high success rate may be key to helping us discover life at one of these planets in the future.</p>
<p>There are many ways forward for technosignature searches at low frequencies. Currently, there is a <a href="https://nenufar.obs-nancay.fr/en/homepage-en/">sister survey (Nenufar)</a> being carried out on that operates at 30-85 MHz. Along with this, further Lofar observations will increase the volume of the survey by a factor of ten over the course of the coming year. The collected data is also used for investigating astronomical objects known as pulsars, fast radio bursts, radio exoplanets and more.</p>
<p>Thankfully, we’re only at the start of a long journey. I have no doubt that many wondrous things will be found. And if we’re lucky, we may reap the biggest reward of all: some company in the cosmos.</p><img src="https://counter.theconversation.com/content/218506/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Owen Johnson receives funding from the Breakthrough Prize Foundation. </span></em></p>Previous searches for extraterrestrial life have included only the radio band above 600 MHz, leaving lower frequencies virtually unexplored.Owen Johnson, PhD Candidate of Astrophysics, Trinity College DublinLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2109552023-08-04T12:30:01Z2023-08-04T12:30:01ZAre we alone in the universe? 4 essential reads on potential contact with aliens<figure><img src="https://images.theconversation.com/files/541095/original/file-20230803-27-wa23kr.jpg?ixlib=rb-1.1.0&rect=39%2C0%2C8694%2C5617&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">UFOs usually have non-extraterrestrial origins, but many have urged the government to be more transparent about UFO data. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/long-exposure-of-andromeda-galaxy-royalty-free-image/1455373371?phrase=space&adppopup=true">Westend61/Westend61 via Getty Images</a></span></figcaption></figure><p>The House subcommittee on National Security, the Border, and Foreign Affairs <a href="https://www.c-span.org/video/?529499-1/hearing-unidentified-aerial-phenomena">met in July 2023 to discuss</a> affairs so foreign that they may not even be of this world. During the meeting, several military officers testified that unidentified anomalous phenomena – the government’s name for UFOs – <a href="https://theconversation.com/whistleblower-calls-for-government-transparency-as-congress-digs-for-the-truth-about-ufos-210435">pose a threat</a> to national security. </p>
<p>Their testimony may have <a href="https://theconversation.com/whistleblower-calls-for-government-transparency-as-congress-digs-for-the-truth-about-ufos-210435">raised eyebrows in the chamber</a>, but there’s still no public physical evidence of extraterrestrial life. In fact, most UFO sightings <a href="https://theconversation.com/why-people-tend-to-believe-ufos-are-extraterrestrial-208403">have earthly explanations</a>, from tricks of the light to weather balloons. </p>
<p>Whether or not these testimonials hold any grains of truth, some scholars argue that simply by listening for signs of extraterrestrials, we’re already <a href="https://theconversation.com/first-contact-with-aliens-could-end-in-colonization-and-genocide-if-we-dont-learn-from-history-207793">engaging in the first phase of contact</a> with alien life. </p>
<p>These four articles from our archives dive into what went down during the subcommittee hearing, why perceived UFO sightings usually have human explanations, and how humanity can learn from history when it comes to engaging with extraterrestrials. </p>
<h2>1. Whistleblower allegations</h2>
<p>The most interesting testimony of the July 26 subcommittee hearing came from ex-Air Force Intelligence Officer David Grusch, who <a href="https://oversight.house.gov/wp-content/uploads/2023/07/Dave_G_HOC_Speech_FINAL_For_Trans.pdf">claimed that</a> the U.S. has nonhuman biological material recovered from a UFO crash site. The Pentagon has <a href="https://abcnews.go.com/Politics/house-oversight-plans-ufo-hearing-after-unconfirmed-claims/story?id=99899883">denied this claim</a>, and it has <a href="https://abcnews.go.com/Politics/house-oversight-plans-ufo-hearing-after-unconfirmed-claims/story?id=99899883">denied the existence of any program</a> designed to retrieve and reverse-engineer crashed UFOs. </p>
<p>All witnesses at the hearing advocated for more government transparency around reports of UFOs. Intelligence agencies and the Pentagon currently steward this data, most of which <a href="https://www.newsnationnow.com/space/ufo/pentagon-blocks-lawmakers-ufo-data-uap-hearing/">is not public</a>. While having access to more data may help understand what’s going on, as the University of Arizona’s <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">Chris Impey</a> put it, “the gold standard is physical evidence.”</p>
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<a href="https://theconversation.com/whistleblower-calls-for-government-transparency-as-congress-digs-for-the-truth-about-ufos-210435">Whistleblower calls for government transparency as Congress digs for the truth about UFOs</a>
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<h2>2. Sociological explanations</h2>
<p>Again, while no physical evidence has been made public, anyone surfing the internet can see plenty of alleged UFO videos, photos and stories. <a href="https://scholar.google.com/citations?user=ZEQu09wAAAAJ&hl=en">Barry Markovsky</a>, from the University of South Carolina, is a sociologist of shared beliefs and misconceptions who explained why UFOs seem to <a href="https://theconversation.com/why-people-tend-to-believe-ufos-are-extraterrestrial-208403">captivate the public</a> every few years.</p>
<p>People want explanations <a href="https://thedecisionlab.com/biases/ambiguity-effect">for ambiguous situations</a>, and they’re easily influenced by others. Social media enables a concept called <a href="https://doi.org/10.31269/triplec.v3i2.21">bottom-up social diffusion</a>. Say one user posts a blurry video claiming it depicts a UFO. It’s easy for that user’s network to see and repost the video and so on, until it goes viral. Then, when organized institutions like news outlets or government sources publish UFO-related information, that’s called <a href="https://doi.org/10.31269/triplec.v3i2.21">top-down social diffusion</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two circle-and-line graphics, the left showing several circles connected to one another with lines, while the right shows one circle at the top connecting several other circles" src="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=284&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=284&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=284&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=357&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=357&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=357&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The left image shows bottom-up diffusion, in which information spreads from person to person. The right shows top-down diffusion, in which information spreads from one authority.</span>
<span class="attribution"><span class="source">Barry Markovsky</span></span>
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<p>“Diffusion processes can combine into self-reinforcing loops. Mass media spreads UFO content and piques worldwide interest in UFOs. More people aim their cameras at the skies, creating more opportunities to capture and share odd-looking content,” Markovsky wrote. “Poorly documented UFO pics and videos spread on social media, leading media outlets to grab and republish the most intriguing. Whistleblowers emerge periodically, fanning the flames with claims of secret evidence.”</p>
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Read more:
<a href="https://theconversation.com/why-people-tend-to-believe-ufos-are-extraterrestrial-208403">Why people tend to believe UFOs are extraterrestrial</a>
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<h2>3. Signature detection</h2>
<p>While UFOs might have traction on social media, it’s likely that the first trace of extraterrestrial life won’t come from a crashed alien spaceship. Instead, scientists could potentially <a href="https://theconversation.com/signatures-of-alien-technology-could-be-how-humanity-first-finds-extraterrestrial-life-191054">pick up signals</a> like radio waves or pollution from some distant galaxy that might indicate extraterrestrial technology. </p>
<p>The <a href="https://www.seti.org/">Search for Extraterrestrial Intelligence</a> is a group of scientists all working on the search for extraterrestrial life. Part of what they do is listen for these “<a href="https://doi.org/10.1017/S1473550419000284">technosignatures</a>”.</p>
<p>As two astronomers who work on the Search for Extraterrestrial Intelligence, Penn State’s <a href="https://sites.psu.edu/macyhuston/">Macy Huston</a> and <a href="https://sites.psu.edu/astrowright/">Jason Wright</a> wrote about how humans often <a href="https://www.doi.org/10.1126/science.199.4327.377">unintentionally broadcast signals</a> like radio waves into space. In theory, extraterrestrial civilizations could be doing the same thing – and if scientists can pick up on these signals, they might have their first hints at alien life. </p>
<p>“However, this approach assumes that extraterrestrial civilizations <a href="https://www.universetoday.com/149513/beyond-fermis-paradox-xvii-what-is-the-seti-paradox-hypothesis/">want to communicate</a> with other technologically advanced life,” Huston and Wright explained. “Humans very rarely send targeted signals into space, and some scholars argue that intelligent species may <a href="https://theconversation.com/blasting-out-earths-location-with-the-hope-of-reaching-aliens-is-a-controversial-idea-two-teams-of-scientists-are-doing-it-anyway-182036">purposefully avoid broadcasting</a> out their locations. This search for signals that no one may be sending is called <a href="https://doi.org/10.48550/arXiv.physics/0611283">the SETI Paradox</a>.” </p>
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Read more:
<a href="https://theconversation.com/signatures-of-alien-technology-could-be-how-humanity-first-finds-extraterrestrial-life-191054">Signatures of alien technology could be how humanity first finds extraterrestrial life</a>
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<h2>4. Ethical considerations</h2>
<p>While the Search for Extraterrestrial Intelligence hasn’t yet detected any extraterrestrial technosignatures, a <a href="https://escholarship.org/uc/item/2sq6f3b0">working group of interdisciplinary scholars</a> in Indigenous studies argued that the act of listening for these signals may already count as engaging in first contact with extraterrestrial life.</p>
<p>The Indigenous studies working group argued that first contact may not be just one event – rather, you can think of it as a <a href="https://doi.org/10.1177/2514848619862191">long phase</a> that begins with listening and planning. Listening can be an act of surveillance, and with that comes ethical considerations. </p>
<p>But research groups like the Search for Extraterrestrial Intelligence don’t often include perspectives from the humanities, even though there are many histories of first contact between groups of people here on Earth to draw from. </p>
<p>James Cook’s 1768 voyage to Oceania, for example, was planned as scientific exploration. But its <a href="https://doi.org/10.17953/aicrj.45.1.lempert">legacy of genocide</a> still affects the Indigenous people of Australia and New Zealand today. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/5gZwLGrJQrM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This BBC video describes the modern ramifications of Captain James Cook’s colonial legacy in New Zealand.</span></figcaption>
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<p>“The initial domino of a public ET message, or recovered bodies or ships, could initiate <a href="https://doi.org/10.1098/rsta.2010.0236">cascading events</a>, including military actions, corporate resource mining and perhaps even geopolitical reorganizing,” wrote <a href="https://www.wacd.ucla.edu/people/faculty/david-shorter">David Shorter</a>, <a href="https://www.bowdoin.edu/profiles/faculty/wlempert/index.html">William Lempert</a> and <a href="https://kimtallbear.com/">Kim Tallbear</a>. “No one can know for sure <a href="https://theconversation.com/is-your-religion-ready-to-meet-et-32541">how engagement with extraterrestrials would go</a>, though it’s better to consider cautionary tales from Earth’s own history sooner rather than later.”</p>
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Read more:
<a href="https://theconversation.com/first-contact-with-aliens-could-end-in-colonization-and-genocide-if-we-dont-learn-from-history-207793">First contact with aliens could end in colonization and genocide if we don't learn from history</a>
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<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/210955/count.gif" alt="The Conversation" width="1" height="1" />
Whistleblower allegations that the government possesses UFOs may not be backed up by public physical evidence, but some argue that listening for extraterrestrial life is the first phase of contact.Mary Magnuson, Assistant Science EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2077932023-07-19T12:23:49Z2023-07-19T12:23:49ZFirst contact with aliens could end in colonization and genocide if we don’t learn from history<figure><img src="https://images.theconversation.com/files/536178/original/file-20230706-15-uc6ukv.jpg?ixlib=rb-1.1.0&rect=44%2C0%2C4928%2C3260&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">SETI has been listening for markers that may indicate alien life -- but is doing so ethical?</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/4TpL_oVkUcQ">Donald Giannati via Unsplash</a></span></figcaption></figure><p>We’re only halfway through 2023, and it feels already like the year of alien contact. </p>
<p>In February, President Joe Biden <a href="https://www.whitehouse.gov/briefing-room/speeches-remarks/2023/02/16/remarks-by-president-biden-on-the-united-states-response-to-recent-aerial-objects/">gave orders</a> to shoot down three unidentified aerial phenomena – NASA’s title for UFOs. Then, the alleged <a href="https://www.cnn.com/videos/business/2021/05/19/ufo-navy-video-jeremy-corbell-orig-jm.cnn">leaked footage</a> from a Navy pilot of a UFO, and then news of a <a href="https://www.theguardian.com/world/2023/jun/06/whistleblower-ufo-alien-tech-spacecraft">whistleblower’s report</a> on a possible U.S. government cover-up about UFO research. Most recently, an independent analysis <a href="https://douglasjohnson.ghost.io/senate-intelligence-bill-gives-holders-of-non-earth-origin-six-months/">published in June</a> suggests that UFOs might have been collected by a clandestine agency of the U.S. government.</p>
<p>If any actual evidence of extraterrestrial life emerges, whether from whistleblower testimony or an admission of a cover-up, humans would face a historic paradigm shift. </p>
<p>As members of an Indigenous studies working group who were asked to lend our disciplinary expertise to a workshop affiliated with the <a href="https://seti.berkeley.edu/">Berkeley SETI Research Center</a>, we have studied centuries of culture contacts and their outcomes from around the globe. Our collaborative preparations for the workshop drew from transdisciplinary research in Australia, New Zealand, Africa and across the Americas. </p>
<p>In its final form, our <a href="https://escholarship.org/uc/item/2sq6f3b0">group statement</a> illustrated the need for diverse perspectives on the ethics of listening for alien life and a broadening of <a href="https://doi.org/10.17953/aicrj.45.1.shorter">what defines “intelligence” and “life.”</a> Based on our findings, we consider first contact less as an event and more as a long process that has already begun. </p>
<h2>Who’s in charge of first contact</h2>
<p>The question of who is “in charge” of preparing for contact with alien life immediately comes to mind. The communities – and their interpretive lenses – most likely to engage in any contact scenario would be military, corporate and scientific. </p>
<p>By giving Americans the legal right to profit from space tourism and planetary resource extraction, the <a href="https://www.govinfo.gov/app/details/COMPS-15975">Commercial Space Launch Competitiveness Act of 2015</a> could mean that corporations will be the first to find signs of extraterrestrial societies. Otherwise, while detecting unidentified aerial phenomena is usually a military matter, and NASA takes the lead on <a href="https://theconversation.com/blasting-out-earths-location-with-the-hope-of-reaching-aliens-is-a-controversial-idea-two-teams-of-scientists-are-doing-it-anyway-182036">sending messages from Earth</a>, most activities around extraterrestrial communications and evidence fall to a program called <a href="https://www.seti.org/">SETI, or the search for extraterrestrial intelligence</a>. </p>
<p>SETI is a collection of scientists with a <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/project-seti">variety of research endeavors</a>, including Breakthrough Listen, which listens for “<a href="https://iopscience.iop.org/article/10.3847/1538-3881/abf649">technosignatures</a>,” or markers, like pollutants, <a href="https://theconversation.com/signatures-of-alien-technology-could-be-how-humanity-first-finds-extraterrestrial-life-191054">of a designed technology</a>. </p>
<p>SETI investigators are <a href="https://www.seti.org/become-pi-or-affiliate">virtually always STEM</a> – science, technology, engineering and math – scholars. Few in the social science and humanities fields have been afforded opportunities to contribute to concepts of and preparations for contact.</p>
<p>In a promising act of disciplinary inclusion, the <a href="https://seti.berkeley.edu/listen/">Berkeley SETI Research Center</a> in 2018 invited working groups – including our <a href="https://doi.org/10.17953/aicrj.45.1.atalay_etal">Indigenous studies working group</a> – from outside STEM fields to craft perspective papers for SETI scientists to consider.</p>
<h2>Ethics of listening</h2>
<p>Neither Breakthough Listen nor SETI’s site features a current <a href="https://doi.org/10.1002/9781119711186.ch13">statement of ethics</a> beyond a <a href="https://doi.org/10.1098/rsta.2010.0311">commitment to transparency</a>. Our working group was <a href="https://bis-space.com/shop/product/do-no-harm-cultural-imperialism-and-the-ethics-of-active-seti/">not the first</a> to raise this issue. And while the <a href="https://www.seti.org/event/seti-live-ethics-outer-space">SETI Institute</a> and <a href="https://www.pseti.psu.edu/seminar/">certain research centers</a> have included ethics in their event programming, it seems relevant to ask who NASA and SETI answer to, and what ethical guidelines they’re following for a potential first contact scenario. </p>
<p><a href="https://seti.wp.st-andrews.ac.uk/">SETI’s Post-Detection Hub</a> – another rare exception to SETI’s STEM-centrism – seems the most likely to develop a range of contact scenarios. The possible circumstances imagined include finding ET artifacts, detecting signals from thousands of light years away, dealing with linguistic incompatibility, finding microbial organisms in space or on other planets, and biological contamination of either their or our species. Whether the U.S. government or heads of military would heed these scenarios is another matter. </p>
<p>SETI-affiliated scholars <a href="https://youtu.be/1Op7AN0MeNw?t=1237">tend to reassure critics</a> that the intentions of those listening for technosignatures are benevolent, since “what harm could come from simply listening?” The chair emeritus of SETI Research, Jill Tarter, <a href="https://www.jstor.org/stable/j.ctt1814k0q">defended listening</a> because any ET civilization would perceive our listening techniques as immature or elementary. </p>
<p>But our working group drew upon the history of colonial contacts <a href="https://doi.org/10.17953/aicrj.45.1.shorter">to show the dangers</a> of thinking that whole civilizations are comparatively advanced or intelligent. For example, when Christopher Columbus and other European explorers came to the Americas, those relationships were shaped by <a href="https://doi.org/10.1163/9789004421882_011">the preconceived notion</a> that the “Indians” were less advanced due to <a href="https://www.nebraskapress.unl.edu/nebraska-paperback/9780803253445/">their lack of writing</a>. This led to decades of <a href="https://www.harpercollins.com/products/the-other-slavery-andres-resendez?variant=39936147849250">Indigenous servitude</a> in the Americas. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black and white engraving of a group of armed and armored men standing on the shore speaking to many naked men. Large ships sail in the background." src="https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537513/original/file-20230714-23-b71osm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This 16th century engraving shows Christopher Columbus landing in the Americas, where he and his explorers deemed the Indigenous people there as ‘primitive,’ as they had no writing system.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Columbus_landing_on_Hispaniola.JPG">Theodor de Bry/Wikimedia Commons</a></span>
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<p>The working group statement also suggested that the act of listening is itself already within a “<a href="https://doi.org/10.1177/2514848619862191">phase of contact</a>.” Like colonialism itself, contact might best be thought of as a series of events that starts with planning, rather than a singular event. Seen this way, isn’t listening potentially without permission just another form of surveillance? To listen intently but indiscriminately seemed to our working group like a <a href="https://doi.org/10.17953/aicrj.45.1.shorter_tallbear">type of eavesdropping</a>. </p>
<p>It seems contradictory that we begin our relations with aliens by listening in without their permission while actively working to stop other countries from <a href="https://www.youtube.com/watch?v=QI_rUsLT5Iw&ab_channel=WION">listening to certain U.S. communications</a>. If humans are initially perceived as disrespectful or careless, ET contact could more likely lead to <a href="https://theconversation.com/how-could-we-build-an-invisibility-cloak-to-hide-earth-from-an-alien-civilization-57092">their colonization of us</a>.</p>
<h2>Histories of contact</h2>
<p>Throughout histories of Western colonization, even in those few cases when contactees were intended to be protected, contact has led to brutal violence, pandemics, enslavement and genocide. </p>
<p>James Cook’s 1768 voyage on the HMS Endeavor was initiated by the <a href="https://doi.org/10.1098/rsnr.1969.0003">Royal Society</a>. This prestigious British academic society charged him with calculating the solar distance between the Earth and the Sun by measuring the visible movement of Venus across the Sun from Tahiti. The society strictly forbade him from any colonial engagements. </p>
<p>Though he achieved his scientific goals, Cook also <a href="https://doi.org/10.1017/S1743921305001262">received orders</a> from the Crown to map and claim as much territory as possible on the return voyage. Cook’s actions put into motion wide-scale colonization and Indigenous dispossession across Oceania, including the <a href="https://doi.org/10.17953/aicrj.45.1.lempert">violent conquests of Australia and New Zealand</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A painting showing five men, two dogs, and a statue of a woman standing in a clearing near the ocean shore. The center man, James Cook, is holding his hat out." src="https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537303/original/file-20230713-17-55wdsd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The 1768 voyage of British captain James Cook, center, put into motion wide-scale colonization and Indigenous dispossession across Oceania.</span>
<span class="attribution"><a class="source" href="https://nla.gov.au/nla.obj-135646842/view">John Hamilton Mortimer via the National Library of Australia</a></span>
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<p>The Royal Society gave Cook a “<a href="https://bigthink.com/thinking/star-trek-prime-directive/">prime directive</a>” of doing no harm and to only conduct research that would broadly benefit humanity. However, explorers are rarely independent from their funders, and their explorations reflect the political contexts of their time. </p>
<p>As scholars attuned to both research ethics and histories of colonialism, we wrote about Cook in our working group statement to showcase why SETI might want to explicitly disentangle their intentions <a href="https://www.govinfo.gov/app/details/COMPS-15975">from those of corporations, the military and the government</a>. </p>
<p>Although separated by vast time and space, both Cook’s voyage and SETI share key qualities, including their appeal to celestial science in the service of all humanity. They also share a mismatch between their ethical protocols and the likely long-term impacts of their success.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/5gZwLGrJQrM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This BBC video describes the modern ramifications of Captain James Cook’s colonial legacy in New Zealand.</span></figcaption>
</figure>
<p>The initial domino of a public ET message, or recovered bodies or ships, could initiate <a href="https://doi.org/10.1098/rsta.2010.0236">cascading events</a>, including military actions, corporate resource mining and perhaps even geopolitical reorganizing. The history of imperialism and colonialism on Earth illustrates that <a href="https://doi.org/10.1080/14623520601056240">not everyone benefits from colonization</a>. No one can know for sure <a href="https://theconversation.com/is-your-religion-ready-to-meet-et-32541">how engagement with extraterrestrials would go</a>, though it’s better to consider cautionary tales from Earth’s own history sooner rather than later.</p>
<p><em>This article has been updated to correct the date of James Cook’s voyage.</em></p><img src="https://counter.theconversation.com/content/207793/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Delgado Shorter has received funding from the National Science Foundation, the University of California, and the California Community Foundation. </span></em></p><p class="fine-print"><em><span>William Lempert has received funding from Bowdoin College, the Wenner-Gren Foundation for Anthropological Research, the Fulbright IIE US Scholar Program, the Lois Roth Endowment, the Andrew W. Mellon Foundation, and the American Council of Learned Societies.</span></em></p><p class="fine-print"><em><span>Kim TallBear does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Three Indigenous studies scholars draw from colonial histories and explain why listening for alien life can have ethical ramifications.David Delgado Shorter, Professor of World Arts and Cultures/Dance, University of California, Los AngelesKim TallBear, Professor of Native Studies, University of AlbertaWilliam Lempert, Assistant Professor of Anthropology, Bowdoin CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2060552023-07-12T12:39:24Z2023-07-12T12:39:24ZA new, thin-lensed telescope design could far surpass James Webb – goodbye mirrors, hello diffractive lenses<figure><img src="https://images.theconversation.com/files/536371/original/file-20230707-21-kxopc5.jpeg?ixlib=rb-1.1.0&rect=44%2C44%2C1209%2C599&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A light, cheap space telescope design would make it possible to put many individual units in space at once.</span> <span class="attribution"><span class="source">Katie Yung, Daniel Apai /University of Arizona and AllThingsSpace /SketchFab</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Astronomers have discovered more than <a href="https://exoplanets.nasa.gov/discovery/exoplanet-catalog/">5,000 planets outside of the solar system</a> to date. The grand question is whether <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">any of these planets are home to life</a>. To find the answer, astronomers will likely need <a href="https://nap.nationalacademies.org/catalog/26141/pathways-to-discovery-in-astronomy-and-astrophysics-for-the-2020s">more powerful telescopes</a> than exist today.</p>
<p>I am an <a href="https://scholar.google.com/citations?user=2SCIYjIAAAAJ&hl=en&oi=ao">astronomer who studies astrobiology</a> and planets around distant stars. For the last seven years, I have been co-leading a team that is developing a new kind of space telescope that could collect a hundred times more light than the <a href="https://theconversation.com/the-most-powerful-space-telescope-ever-built-will-look-back-in-time-to-the-dark-ages-of-the-universe-169603">James Webb Space Telescope</a>, the biggest space telescope ever built.</p>
<p>Almost all space telescopes, including Hubble and Webb, collect light using mirrors. Our proposed telescope, the <a href="https://nautilus-array.space/">Nautilus Space Observatory</a>, would replace large, heavy mirrors with a novel, thin lens that is much lighter, cheaper and easier to produce than mirrored telescopes. Because of these differences, it would be possible to launch many individual units into orbit and create a powerful network of telescopes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A blue planet with clouds." src="https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536355/original/file-20230707-21-3gvtcx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Exoplanets, like TOI-700d shown in this artist’s conception, are planets beyond our solar system and are prime candidates in the search for life.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/spaceimages/images/largesize/PIA23408_hires.jpg">NASA's Goddard Space Flight Center</a></span>
</figcaption>
</figure>
<h2>The need for larger telescopes</h2>
<p>Exoplanets – planets that orbit stars other than the Sun – are prime targets in the search for life. Astronomers need to use giant space telescopes that collect huge amounts of light to <a href="https://exoplanets.nasa.gov/discovery/missions/#first-planetary-disk-observed">study these faint and faraway objects</a>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A massive circular gold mirror with people standing in the foreground." src="https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536356/original/file-20230707-23-pdn1e5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The James Webb Space Telescope is just barely able to search exoplanets for signs of life.</span>
<span class="attribution"><a class="source" href="http://jwst.nasa.gov/multimedia.html">NASA</a></span>
</figcaption>
</figure>
<p>Existing telescopes can detect exoplanets as small as Earth. However, it takes a lot more sensitivity to begin to learn about the chemical composition of these planets. Even Webb is just barely powerful enough to search <a href="https://doi.org/10.3847/1538-3881/ab21e0">certain exoplanets for clues of life</a> – namely <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">gases in the atmosphere</a>. </p>
<p>The James Webb Space Telescope cost more than <a href="https://www.gao.gov/products/gao-18-273">US$8 billion and took over 20 years to build</a>. The next flagship telescope is not expected to fly before 2045 and is estimated to <a href="https://www.science.org/content/article/nasa-unveils-initial-plan-multibillion-dollar-telescope-find-life-alien-worlds">cost $11 billion</a>. These ambitious telescope projects are always expensive, laborious and produce a single powerful – but very specialized – observatory.</p>
<h2>A new kind of telescope</h2>
<p>In 2016, aerospace giant <a href="https://www.northropgrumman.com">Northrop Grumman</a> invited me and 14 other professors and NASA scientists – all experts on exoplanets and the search for extraterrestrial life – to Los Angeles to answer one question: What will exoplanet space telescopes look like in 50 years?</p>
<p>In our discussions, we realized that a major bottleneck preventing the construction of more powerful telescopes is the challenge of making larger mirrors and getting them into orbit. To bypass this bottleneck, a few of us came up with the idea of revisiting an old technology called diffractive lenses. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cross section of two lenses, with the one on the left showing a jagged surface and the one on the right a rounded surface." src="https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=897&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=897&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=897&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1127&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1127&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536361/original/file-20230707-29-i85svw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1127&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Diffractive lenses, left, are much thinner compared to similarly powerful refractive lenses, right.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Fresnel_lens#/media/File:Fresnel_lens.svg">Pko/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Conventional lenses use refraction to focus light. <a href="https://theconversation.com/can-rainbows-form-in-a-circle-fun-facts-on-the-physics-of-rainbows-202952">Refraction is when light changes direction</a> as it passes from one medium to another – it is the reason light bends when it enters water. In contrast, diffraction is when light bends around corners and obstacles. A cleverly arranged pattern of steps and angles on a glass surface can form a diffractive lens. </p>
<p>The first such lenses were invented by the French scientist Augustin-Jean Fresnel in 1819 to provide lightweight lenses for <a href="https://wwnorton.com/books/9780393350890">lighthouses</a>. Today, similar diffractive lenses can be found in many small-sized consumer optics – from <a href="https://global.canon/en/v-square/34.html">camera lenses</a> to <a href="https://doi.org/10.1889/1.2206112">virtual reality headsets</a>. </p>
<p>Thin, simple diffractive lenses are <a href="http://cplire.ru:8080/2902/1/OGRW_2014_Proceedings.pdf#page=77">notorious for their blurry images</a>, so they have never been used in astronomical observatories. But if you could improve their clarity, using diffractive lenses instead of mirrors or refractive lenses would allow a space telescope to be much cheaper, lighter and larger.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person holding a round, thin piece of glass." src="https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=488&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=488&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536359/original/file-20230707-17-kdihhg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=488&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the benefits of diffractive lenses is that they can remain thin while increasing in diameter.</span>
<span class="attribution"><span class="source">Daniel Apai/University of Arizona</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>A thin, high-resolution lens</h2>
<p>After the meeting, I returned to the University of Arizona and decided to explore whether modern technology could produce diffractive lenses with better image quality. Lucky for me, <a href="https://profiles.arizona.edu/person/milster">Thomas Milster</a> – one of the world’s leading experts on diffractive lens design – works in the building next to mine. We formed a team and got to work.</p>
<p>Over the following two years, our team invented a new type of diffractive lens that required new manufacturing technologies to etch a complex pattern of tiny grooves onto a piece of clear glass or plastic. The specific pattern and shape of the cuts focuses incoming light to a single point behind the lens. The new design produces a <a href="https://doi.org/10.1364/OSAC.410187">near-perfect quality image</a>, far better than previous diffractive lenses. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A triangular piece of glass with subtle etchings reflecting in the light." src="https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536358/original/file-20230707-25-gj9ryc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A diffractive lens bends light using etchings and patterns on its surface.</span>
<span class="attribution"><span class="source">Daniel Apai/University of Arizona</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Because it is the surface texture of the lens that does the focusing, not the thickness, you can easily make the lens bigger while <a href="https://doi.org/10.1364/FIO.2020.JTu7A.1">keeping it very thin and lightweight</a>. Bigger lenses collect more light, and low weight means <a href="https://doi.org/10.3847/1538-3881/ab2631">cheaper launches to orbit</a> – both great traits for a space telescope.</p>
<p>In August 2018, our team produced the first prototype, a 2-inch (5-centimeter) diameter lens. Over the next five years, we further improved the image quality and increased the size. We are now completing a 10-inch (24-cm) diameter lens that will be more than 10 times lighter than a conventional refractive lens would be.</p>
<h2>Power of a diffraction space telescope</h2>
<p>This new lens design makes it possible to rethink how a space telescope might be built. In 2019, our team published a concept called the <a href="https://doi.org/10.3847/1538-3881/ab2631">Nautilus Space Observatory</a>. </p>
<p>Using the new technology, our team thinks it is possible to build a 29.5-foot (8.5-meter) diameter lens that would be only about 0.2 inches (0.5 cm) thick. The lens and support structure of our new telescope could weigh around 1,100 pounds (500 kilograms). This is more than three times lighter than a Webb–style mirror of a similar size and would be bigger than Webb’s 21-foot (6.5-meter) diameter mirror. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A spherical object in space with a lens on one side." src="https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536353/original/file-20230707-21-pbljxz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The thin lens allowed the team to design a lighter, cheaper telescope, which they named the Nautilus Space Observatory.</span>
<span class="attribution"><span class="source">Daniel Apai/University of Arizona</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The lenses have other benefits, too. First, they are <a href="https://doi.org/10.1117/12.2633573">much easier and quicker</a> <a href="https://theconversation.com/how-do-you-build-a-mirror-for-one-of-the-worlds-biggest-telescopes-49927">to fabricate than mirrors</a> and can be made en masse. Second, lens-based telescopes work well even when not aligned perfectly, making these telescopes easier to <a href="https://doi.org/10.1117/12.2633760">assemble</a> and fly in space than mirror-based telescopes, which require extremely precise alignment.</p>
<p>Finally, since a single Nautilus unit would be light and relatively cheap to produce, it would be possible to put dozens of them into orbit. Our current design is in fact not a single telescope, but a constellation of 35 individual telescope units.</p>
<p>Each individual telescope would be an independent, highly sensitive observatory able to collect more light than Webb. But the real power of Nautilus would come from turning all the individual telescopes toward a single target. </p>
<p>By combining data from all the units, Nautilus’ light-collecting power would equal a telescope nearly 10 times larger than Webb. With this powerful telescope, astronomers could search hundreds of exoplanets for atmospheric gases that may <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">indicate extraterrestrial life</a>.</p>
<p>Although the Nautilus Space Observatory is still a long way from launch, our team has made a lot of progress. We have shown that all aspects of the technology work in small-scale prototypes and are now focusing on building a 3.3-foot (1-meter) diameter lens. Our next steps are to send a small version of the telescope to the edge of space on a high-altitude balloon.</p>
<p>With that, we will be ready to propose a revolutionary new space telescope to NASA and, hopefully, be on the way to exploring hundreds of worlds for signatures of life.</p><img src="https://counter.theconversation.com/content/206055/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Apai receives funding from NASA, NSF, and the Gordon and Betty Moore Foundation. He works for The University of Arizona.</span></em></p>Space telescopes are limited in size due to the difficulties and cost of getting into orbit. By revamping an old optical technology, researchers are working on a lightweight and thin telescope design.Daniel Apai, Associate Dean for Research and Professor of Astronomy and Planetary Sciences, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2051882023-05-15T11:47:09Z2023-05-15T11:47:09ZWhat would aliens learn if they observed the Earth? Our study provides an answer<figure><img src="https://images.theconversation.com/files/525346/original/file-20230510-21-a0x73r.jpeg?ixlib=rb-1.1.0&rect=424%2C154%2C4718%2C5150&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Earth seen from orbit around the Moon.</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>Are we alone in the universe? It’s a question that fascinates scientists and the public alike. In science, the focus tends to be on our <a href="https://breakthroughinitiatives.org/initiative/1">search for life elsewhere</a>. The idea that we might be watched by a distant alien civilisation, however, is usually <a href="https://www.goodreads.com/book/show/8909.The_War_of_the_Worlds">confined to the realm of science fiction</a>.</p>
<p>But if there are other technological civilisations out there, they would probably be significantly more developed than we are. After all, we have only just emerged as a fledgling technical (industrial) civilisation in the last 200 years - other technical civilisations could easily be 1,000 or 10,000 or even 100,000 years more advanced than we are.</p>
<p>And no one can deny that the <a href="https://en.wikipedia.org/wiki/Accelerating_change">pace of our own technological progress is accelerating</a>, in some areas at a blistering pace. To paraphrase science fiction author <a href="https://en.wikipedia.org/wiki/Clarke%27s_three_laws">Arthur C. Clarke’s third law</a> - an advanced civilisation would appear to us as capable of magic in terms of their technical prowess. </p>
<p>Over the last few years, my colleagues and I have started to think about whether an advanced civilisation could detect the technological signatures (<a href="https://astrobiology.nasa.gov/news/technosignatures-and-the-search-for-extraterrestrial-intelligence/">“techno-signatures”</a>), such as radio emissions, from Earth. And if so, what might they detect?</p>
<p>Our <a href="https://academic.oup.com/mnras/article/522/2/2393/7028804?login=false">latests study</a> provides a clue.</p>
<p>This isn’t the first time such research has been undertaken. But it’s now more than 50 years since the topic was <a href="https://ui.adsabs.harvard.edu/abs/1978Sci...199..377S/abstract">properly considered</a>. While a lot has changed since the mid-1970s, by far the biggest change has occurred in the last two decades with the advent of mobile phones. These <a href="https://www.simbase.com/learning/how-mobile-networks-work">devices and the towers that connect them</a> have created a new broadband radio emission techno-signature.</p>
<p>Although 4G mobile handsets and transmitting towers are relatively low power individually (0.1-200 watt), there are just so many of them – billions of phones and many millions of towers. And the accumulated radio emission from these is beginning to become quite significant. But would it be noticeable to an alien civilisation watching from afar? We wanted to find out.</p>
<p>It turns out to be rather difficult to find a public database that lists the location and transmitting characteristics of all the mobile towers around the world. But by using the <a href="https://opencellid.org/">OpenCellID database</a>, with data populated by crowdsourcing, we were able to build a simple model estimating the global distribution of mobile towers. </p>
<p>Our model is no doubt crude and incomplete, but it is our best estimate of the techno-signature mobile towers leak out into space. </p>
<p>Because the Earth rotates on its axis, an advanced civilisation located somewhere in our galaxy would measure the radio emission from mobile towers to rise and fall in intensity as different parts of the Earth rotate into view. </p>
<p>The model is complicated by the fact that the transmission of mobile towers is typically beamed towards the horizon. This means that at any given time, towers that are viewed to be setting or rising on the Earth’s horizon will contribute most to the measured signal. </p>
<h2>Alien conclusions?</h2>
<p>An advanced civilisation making many precise measurements of this radio leakage over time could probably conclude that our planet is mostly covered by water and is separated into several major land masses. The radio leakage typically come from the land masses rather than the water. </p>
<p>They might also be able to tell that while most of the mobile radio leakage is associated with land masses, the towers (and presumably their intelligent users) tend to be situated along the coastline. </p>
<p>They would also see that mobile tower networks are quite equitably distributed across the planet. That’s different to the traditional radio leakage previously recognised as major techno-signatures – in particular, radar and TV transmitters. </p>
<p>Our simulations show that significant contributions to the Earth’s mobile leakage radiation is being made by developing regions, such as Africa and Asia. This is no surprise given the <a href="https://toppandigital.com/translation-blog/mobile-technology-transforming-africa/">importance of mobile systems</a> in all aspects of society in developing countries. </p>
<p>We calculated the power emitted from Earth – which is about 4 gigawatt (GW) in total at its peak (one GW could power around 750,000 homes for an hour). We estimated the transmission as viewed from three different stars in our galaxy – <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Starlog/lalande.html">HD 95735</a>, <a href="https://earthsky.org/astronomy-essentials/barnards-star-closest-stars-famous-stars/">Barnard’s star,</a> and <a href="https://earthsky.org/brightest-stars/alpha-centauri-is-the-nearest-bright-star/">Alpha Centauri A</a>. </p>
<p>We worked out that an alien civilisation near these locations would, however, need much better telescopes than we have to detect the Earth’s mobile radio leakage. But that would be quite probable, given most technical civilisations are expected to be much more advanced than we are. </p>
<p>There are also other types of emissions they could see, such as military radar systems and deep space communication transmissions to distant spacecraft, such as the Voyager space probes. While these signals would be relatively rare events for an observing alien, they have the advantage of being extremely powerful. </p>
<figure class="align-center ">
<img alt="Radio telescope under the Milky Way." src="https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525581/original/file-20230511-23-ildy0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Do aliens have radio telescopes?</span>
<span class="attribution"><span class="source">zhengzaishuru/Shutterstock</span></span>
</figcaption>
</figure>
<p>Radio techno-signatures are probably the defining characteristic of our own civilisation’s existence, at least from an alien’s perspective. But an extraterrestrial species would also find leakage radiation across the electromagnetic spectrum (including visible light).</p>
<p>If we continue to increase our energy consumption at the current rate, <a href="https://energyeducation.ca/encyclopedia/Waste_heat">“waste-heat”</a> – an unavoidable end-product of energy usage – will also be discharged into space. There it would manifest itself as an anomalous excess at infra-red wavelengths – a telltale sign of an active technical civilisation. </p>
<p>Other techno-signatures including <a href="https://ui.adsabs.harvard.edu/abs/2021ApJ...908..164K/abstract">industrial pollutants</a> in the Earth’s atmosphere would also be noticeable to aliens equipped with powerful telescopes and spectral analysis systems (which break down light according to wavelength). An advanced alien civilisation could no doubt have a good guess at our particular phase of industrialisation and our energy consumption. </p>
<p>On Earth, we use the <a href="https://www.universetoday.com/153167/what-is-the-kardashev-scale/">Kardashev scale</a> for estimating the development of alien civilisations based on their energy usage - on that scale we’d appear as an emerging technical civilisation, not yet on the bottom rung of the ladder. </p>
<p>And even if an alien species failed to detect all this at the moment, they might do better very soon. We plan to extend this work to include traditional radio techno-signatures and other emerging sources of radio leakage radiation, including 5G systems, wifi, digital transmissions and deep space communications. </p>
<p>This would also include the cocoon of radio emission that will soon surround the Earth as the growth of huge <a href="https://www.iau.org/public/themes/satellite-constellations/">satellite constellations</a> such as Starlink and OneWeb provide global <a href="https://theconversation.com/starlink-amazon-and-others-are-racing-to-fill-the-sky-with-bigger-satellites-to-deliver-mobile-coverage-everywhere-on-earth-190237">wifi coverage</a>. </p>
<p>Who knows, it might even be possible for aliens to decode the complex modulation of our mobile communication systems. Ultimately, as the Earth becomes artificially brighter at all wavelengths, the chances that they detect us before we detect them, cannot be ruled out.</p><img src="https://counter.theconversation.com/content/205188/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Garrett does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The accumulated radio emission from mobile phones on Earth is beginning to become quite significant.Michael Garrett, Sir Bernard Lovell chair of Astrophysics and Director of Jodrell Bank Centre for Astrophysics, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2043512023-05-03T12:10:32Z2023-05-03T12:10:32ZAI is helping astronomers make new discoveries and learn about the universe faster than ever before<figure><img src="https://images.theconversation.com/files/523645/original/file-20230501-18-4e90m3.jpg?ixlib=rb-1.1.0&rect=0%2C299%2C4895%2C3031&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The sky is big and full of information that AI tools can help astronomers unlock. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/paul-wild-observatory-under-starry-sky-royalty-free-image/637273906?phrase=telescope+with+milky+way&adppopup=true">Yuga Kurita/Moment via Getty Images</a></span></figcaption></figure><p>The famous first image of a black hole <a href="https://doi.org/10.3847/2041-8213/acc32d">just got two times sharper</a>. A research team used artificial intelligence to dramatically improve upon <a href="https://doi.org/10.3847/2041-8213/ab0ec7">its first image</a> from 2019, which now shows the black hole at the center of the M87 galaxy as darker and bigger than the first image depicted.</p>
<p>I’m an <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">astronomer</a> who studies and has written about <a href="https://wwnorton.com/books/9780393343861">cosmology</a>, <a href="https://wwnorton.com/books/9780393357509">black holes</a> and <a href="https://www.penguinrandomhouse.com/books/718149/worlds-without-end-by-chris-impey/">exoplanets</a>. Astronomers have been using AI for decades. In fact, in 1990, astronomers from the University of Arizona, where I am a professor, were among the <a href="https://www.datasciencecentral.com/the-evolution-of-astronomical-ai/">first to use a type of AI called a neural network</a> to study the shapes of galaxies. </p>
<p>Since then, AI has spread into every field of astronomy. As the technology has become more powerful, AI algorithms have begun helping astronomers tame massive data sets and discover new knowledge about the universe.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A group of radio antennas pointed at the sky." src="https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/523641/original/file-20230501-18-3sjj1h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Astronomy is no longer limited to just optical images – radio telescopes produce huge amounts of data that researchers need to process.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/observatory-antenna-in-the-sunse-royalty-free-image/1309400138?phrase=astronomy+data&adppopup=true">Wenbin/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>Better telescopes, more data</h2>
<p>As long as astronomy has been a science, it has involved trying to make sense of the multitude of objects in the night sky. That was relatively simple when the only tools were the naked eye or a simple telescope, and all that could be seen were a few thousand stars and a handful of planets.</p>
<p>A hundred years ago, Edwin Hubble used newly built telescopes to show that the universe is filled with not just stars and clouds of gas, <a href="https://www.nasa.gov/content/about-story-edwin-hubble">but countless galaxies</a>. As telescopes have continued to improve, the sheer number of celestial objects humans can see and the <a href="https://events.asiaa.sinica.edu.tw/school/20170904/talk/djorgovski1.pdf">amount of data</a> astronomers need to sort through have both grown exponentially, too.</p>
<p>For example, the soon-to-be-completed <a href="https://www.lsst.org/about">Vera Rubin Observatory</a> in Chile will make images so large that it would take 1,500 high-definition TV screens to view each one in its entirety. Over 10 years it is expected to generate 0.5 exabytes of data – about 50,000 times the amount of information held in all of the books contained within the Library of Congress. </p>
<p>There are 20 telescopes with mirrors larger than 20 feet (6 meters) in diameter. AI algorithms are the only way astronomers could ever hope to work through all of the data available to them today. There are a number of ways AI is proving useful in processing this data.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sky filled with galaxies." src="https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/523642/original/file-20230501-292-iuhviz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the earliest uses of AI in astronomy was to pick out the multitude of faint galaxies hidden in the background of images.</span>
<span class="attribution"><a class="source" href="https://flickr.com/photos/nasawebbtelescope/52777397541/">ESA/Webb, NASA & CSA, J. Rigby</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Picking out patterns</h2>
<p>Astronomy often involves looking for needles in a haystack. About 99% of the pixels in an astronomical image contain background radiation, light from other sources or the blackness of space – only 1% have the subtle shapes of faint galaxies. </p>
<p>AI algorithms – in particular, neural networks that use many interconnected nodes and are able to learn to recognize patterns – are perfectly suited for picking out the patterns of galaxies. Astronomers began <a href="https://doi.org/10.1111/j.1365-2966.2010.16713.x">using neural networks to classify galaxies</a> in the early 2010s. Now the algorithms <a href="https://www.nao.ac.jp/en/news/science/2020/20200811-subaru.html">are so effective</a> that they can classify galaxies with an accuracy of 98%.</p>
<p>This story has been repeated in other areas of astronomy. Astronomers working on SETI, the Search for Extraterrestrial Intelligence, use radio telescopes to look for signals from distant civilizations. Early on, radio astronomers scanned charts by eye to <a href="https://earthsky.org/space/wow-signal-explained-comets-antonio-paris/">look for anomalies</a> that couldn’t be explained. More recently, researchers harnessed 150,000 personal computers and 1.8 million citizen scientists to look for artificial <a href="https://www.nytimes.com/2020/03/23/science/seti-at-home-aliens.html">radio signals</a>. Now, researchers are using AI to sift through reams of data much more quickly and thoroughly than people can. This has allowed SETI efforts to cover more ground while also greatly reducing the <a href="https://doi.org/10.1038/s41550-022-01872-z">number of false positive signals</a>.</p>
<p>Another example is the search for exoplanets. Astronomers discovered most of the <a href="https://exoplanets.nasa.gov/">5,300 known exoplanets</a> by measuring a dip in the amount of light coming from a star <a href="https://exoplanets.nasa.gov/resources/2338/exoplanet-detection-transit-method/">when a planet passes in front of it</a>. AI tools can now pick out the signs of an exoplanet with <a href="https://doi.org/10.48550/arXiv.2011.14135">96% accuracy</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A planet near a dim red star." src="https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/523643/original/file-20230501-16-xeiogk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">AI tools can help astronomers discover new exoplanets like TRAPPIST-1 b.</span>
<span class="attribution"><a class="source" href="https://flickr.com/photos/nasawebbtelescope/52775409328/">NASA, ESA, CSA, Joseph Olmsted (STScI)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Making new discoveries</h2>
<p>AI has proved itself to be excellent at identifying known objects – like galaxies or exoplanets – that astronomers tell it to look for. But it is also quite powerful at finding objects or phenomena that are theorized but have not yet been discovered in the real world.</p>
<p>Teams have used this approach to detect <a href="https://www.sciencedaily.com/releases/2023/02/230207144222.htm">new exoplanets</a>, learn about the <a href="https://www.quantamagazine.org/with-ai-astronomers-dig-up-the-stars-that-birthed-the-milky-way-20230328/">ancestral stars</a> that led to the formation and growth of the Milky Way, and predict the signatures of new types of <a href="https://cerncourier.com/a/gravitational-wave-astronomy-turns-to-ai/">gravitational waves</a>.</p>
<p>To do this, astronomers first use AI to convert theoretical models into observational signatures – including realistic levels of noise. They then use machine learning to sharpen the ability of AI to detect the predicted phenomena.</p>
<p>Finally, radio astronomers have also been using AI algorithms to sift through signals that don’t correspond to known phenomena. Recently a team from South Africa found a <a href="https://www.biznews.com/global-citizen/2023/04/06/machine-learnings-discovery-astronomy">unique object</a> that may be a remnant of the explosive merging of two supermassive black holes. If this proves to be true, the data will allow a new test of general relativity – Albert Einstein’s <a href="https://theconversation.com/why-does-gravity-pull-us-down-and-not-up-162141">description of space-time</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two side-by-side images of an orange circular haze around a dark center." src="https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/523644/original/file-20230501-22-dihfie.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The team that first imaged a black hole, at left, used AI to generate a sharper version of the image, at right, showing the black hole to be larger than originally thought.</span>
<span class="attribution"><a class="source" href="https://iopscience.iop.org/article/10.3847/1538-4357/acaa9a/meta">Medeiros et al 2023</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Making predictions and plugging holes</h2>
<p>As in many areas of life recently, generative AI and large language models like ChatGPT are also making waves in the astronomy world.</p>
<p>The team that created the first image of a black hole in 2019 used a <a href="https://doi.org/10.3847/2041-8213/acc32d">generative AI to produce its new image</a>. To do so, it first taught an AI how to recognize black holes by feeding it simulations of many kinds of black holes. Then, the team used the AI model it had built to fill in gaps in the massive amount of data collected by the radio telescopes on the black hole M87. </p>
<p>Using this simulated data, the team was able to create a new image that is two times sharper than the original and is fully consistent with the predictions of general relativity.</p>
<p>Astronomers are also turning to AI to help tame the complexity of modern research. A team from the Harvard-Smithsonian Center for Astrophysics created a <a href="https://doi.org/10.48550/arXiv.2212.00744">language model called astroBERT</a> to read and organize 15 million scientific papers on astronomy. Another team, based at NASA, has even proposed using AI to <a href="https://www.technologyreview.com/2021/09/20/1035890/ai-predict-astro2020-decadal-survey/">prioritize astronomy projects</a>, a process that astronomers engage in every 10 years.</p>
<p>As AI has progressed, it has become an essential tool for astronomers. As telescopes get better, as data sets get larger and as AIs continue to improve, it is likely that this technology will play a central role in future discoveries about the universe.</p><img src="https://counter.theconversation.com/content/204351/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation and Epic Games.</span></em></p>Artificial intelligence tools are making waves in almost every aspect of life, and astronomy is no different. An astronomer explains the history and future of AI in understanding the universe.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1982742023-03-08T13:41:07Z2023-03-08T13:41:07ZDistant star TOI-700 has two potentially habitable planets orbiting it – making it an excellent candidate in the search for life<figure><img src="https://images.theconversation.com/files/512978/original/file-20230301-18-2jg7dp.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1859%2C1034&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The TOI-700 star system is home to four planets, including two in its habitable zone that could host liquid water.</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/spaceimages/images/largesize/PIA23408_hires.jpg">NASA's Goddard Space Flight Center</a></span></figcaption></figure><p>NASA recently announced the <a href="https://doi.org/10.3847/2041-8213/acb599">discovery of a new, Earth-sized planet</a> in the habitable zone of a nearby star called TOI-700. <a href="https://sites.google.com/site/josepherodriguezjr/">We are</a> <a href="https://avanderburg.github.io/">two of</a> the astronomers who led the discovery of this planet, called TOI-700 e. TOI-700 e is just over 100 light years from Earth – too far away for humans to visit – but we do know that it is similar in size to the Earth, likely rocky in composition and could potentially support life.</p>
<p>You’ve probably heard about some of the <a href="https://exoplanets.nasa.gov/trappist1/">many</a> <a href="https://www.eso.org/public/news/eso1629/">other</a> <a href="https://www.nasa.gov/press-release/nasa-kepler-mission-discovers-bigger-older-cousin-to-earth">exoplanet</a> <a href="https://www.nasa.gov/image-feature/kepler-1649c-earth-size-habitable-zone-planet-hides-in-plain-sight">discoveries</a> in <a href="https://www.nasa.gov/mission_pages/kepler/news/kepscicon-briefing.html">recent</a> years. In fact, TOI-700 e is one of two potentially habitable planets just in the TOI-700 star system. </p>
<p>Habitable planets are those that are just the right distance from their star to have a surface temperature that could sustain liquid water. While it is always exciting to find a new, potentially habitable planet far from Earth, the focus of exoplanet research is shifting away from simply discovering more planets. Instead, researchers are focusing their efforts on finding and studying systems most likely to answer key questions about how planets form, how they evolve, and whether life might exist in the universe. TOI-700 e stands out from many of these other planet discoveries because it is well suited for future studies that could help answer big question about the conditions for life outside the solar system. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/xNeRqbw18Jk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Specific methods for detecting exoplanets, like the transit method, which looks for a dip in the light coming from a distant star as a planet passes in front of it, have led to an explosion in the number of known exoplanets.</span></figcaption>
</figure>
<h2>From 1 to 5,000</h2>
<p>Astronomers discovered the first exoplanet around a Sun-like star <a href="https://doi.org/10.1038/378355a0">in 1995</a>. The field of exoplanet discovery and research has been rapidly evolving ever since.</p>
<p>At first, astronomers were finding only a <a href="https://www.hughosborn.co.uk/2015/02/09/a-history-of-planet-detection-in-one-animation/">few exoplanets each year</a>, but the combination of new cutting-edge facilities focused on <a href="https://www.nasa.gov/tess-transiting-exoplanet-survey-satellite">exoplanet science</a> with improved detection sensitivity have led to astronomers’ discovering hundreds of exoplanets each year. As detection methods and tools have improved, the amount of information scientists can learn about these planets has increased. In 30 years, scientists have gone from barely being able to detect exoplanets to <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">characterizing key chemical clues in their atmospheres</a>, like water, using facilities like the James Webb Space Telescope.</p>
<p>Today, there are more than <a href="https://exoplanetarchive.ipac.caltech.edu/">5,000 known exoplanets</a>, ranging from gas giants to small rocky worlds. And perhaps most excitingly, astronomers have now found about a dozen exoplanets that are likely rocky and orbiting within the habitable zones of their respective stars.</p>
<p>Astronomers have even discovered a few systems – like TOI-700 – that have more than one planet orbiting in the habitable zone of their star. We call these keystone systems.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing a star with a green ring around it marking the habitable zone." src="https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=185&fit=crop&dpr=1 600w, https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=185&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=185&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=233&fit=crop&dpr=1 754w, https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=233&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/512975/original/file-20230301-24-8pqinb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=233&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The TOI-700 system has a large habitable zone, and the newly discovered TOI-700 e, not shown in this image, orbits the star along the inner edge of the habitable zone.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/spaceimages/images/largesize/PIA23407_hires.jpg">NASA's Goddard Space Flight Center</a></span>
</figcaption>
</figure>
<h2>A pair of habitable siblings</h2>
<p>TOI-700 first made headlines when our team announced the discovery of <a href="https://doi.org/10.3847/1538-3881/aba4b2">three small planets orbiting the star</a> in early 2020. Using a <a href="https://doi.org/10.3847/1538-3881/aba4b3">combination of observations</a> from NASA’s <a href="https://exoplanets.nasa.gov/tess/">Transiting Exoplanet Surveying Satellite</a> mission and the <a href="https://www.nasa.gov/mission_pages/spitzer/main/index.html">Spitzer Space Telescope</a> we discovered these planets by measuring small dips in the amount of light coming from TOI-700. These dips in light are caused by planets passing in front of the small, cool, red dwarf star at the center of the system.</p>
<p>By taking precise measurements of the changes in light, we were able to determine that at least three small planets are in the TOI-700 system, with hints of a possible fourth. We could also determine that the third planet from the star, TOI-700 d, orbits within its star’s habitable zone, where the temperature of the planet’s surface could allow for liquid water. </p>
<p>The Transiting Exoplanet Surveying Satellite observed TOI-700 for another year, from July 2020 through May 2021, and using these observations <a href="https://doi.org/10.3847/2041-8213/acb599">our team found the fourth planet, TOI-700 e</a>. TOI-700 e is 95% the size of the Earth and, much to our surprise, orbits on the inner edge of the star’s habitable zone, between planets c and d. Our discovery of this planet makes TOI-700 one of only a few known systems with two Earth-sized planets orbiting in the habitable zone of their star. The fact that it is relatively close to Earth also makes it one of the most accessible systems in terms of future characterization.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="James Webb Space Telescope against the backdrop of space." src="https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=586&fit=crop&dpr=1 754w, https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=586&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/512981/original/file-20230301-24-v7fzr8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=586&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">New tools, like the James Webb Space Telescope, can provide clues about life on distant planets, but with thousands of scientific questions to answer, efficient use of time is key.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:James_Webb_Space_Telescope.jpg#/media/File:James_Webb_Space_Telescope.jpg">Bricktop/Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>The bigger questions and tools to answer them</h2>
<p>With the successful launch of the James Webb Space Telescope, astronomers are now able to start <a href="https://www.nasa.gov/feature/goddard/2022/nasa-s-webb-reveals-an-exoplanet-atmosphere-as-never-seen-before">characterizing the atmospheric chemistry</a> of exoplanets and search for <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">clues about whether life exists</a> on them. In the near future, a number of massive, ground-based telescopes will also help reveal further details about the composition of planets far from the solar system. </p>
<p>But even with powerful new telescopes, collecting enough light to learn these details requires pointing the telescope at a system for a <a href="https://arxiv.org/abs/1708.04239">long period of time</a>. With thousands of <a href="https://www.stsci.edu/jwst/science-execution/approved-programs/cycle-1-go">valuable scientific questions to answer</a>, astronomers need to know where to look. And that is the goal of our team, to find the most interesting and promising exoplanets to study with the Webb telescope and future facilities.</p>
<p>Earth is currently the only data point in the search for life. It is possible alien life could be vastly different from life as we know it, but for now, places similar to the home of humanity with liquid water on the surface offer a good starting point. We believe that keystone systems with multiple planets that are likely candidates for hosting life – like TOI-700 – offer the best use of observation time. By further studying TOI-700, our team will be able to learn more about what makes a planet habitable, how rocky planets similar to Earth form and evolve, and the mechanisms that shaped the solar system. The more astronomers know about how star systems like TOI-700 and our own solar system work, the better the chances of detecting life out in the cosmos.</p><img src="https://counter.theconversation.com/content/198274/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joseph Rodriguez receives funding from the National Aeronautics and Space Administration and Michigan State University. </span></em></p><p class="fine-print"><em><span>Andrew Vanderburg receives funding from the National Aeronautics and Space Administration and the Massachusetts Institute of Technology. </span></em></p>With more than 5,000 known exoplanets, astronomers are shifting their focus from discovering additional distant worlds to identifying which are good candidates for further study.Joey Rodriguez, Assistant Professor of Physics and Astronomy, Michigan State UniversityAndrew Vanderburg, Assistant Professor of Physics, Massachusetts Institute of Technology (MIT)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1976212023-03-03T00:13:56Z2023-03-03T00:13:56ZHumans are still hunting for aliens. Here’s how astronomers are looking for life beyond Earth<figure><img src="https://images.theconversation.com/files/508029/original/file-20230203-12-uvmpl6.jpg?ixlib=rb-1.1.0&rect=302%2C315%2C4072%2C2733&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">zhengzaishuru/Shutterstock</span></span></figcaption></figure><p>We have long been fascinated with the idea of alien life. The earliest written record presenting the idea of “aliens” is seen in the satiric work of Assyrian writer <a href="https://blogs.scientificamerican.com/life-unbounded/the-first-alien/">Lucian of Samosata</a> dated to 200 AD.</p>
<p>In one novel, Lucian <a href="https://www.yorku.ca/inpar/lucian_true_tale.pdf">writes of a journey to the Moon</a> and the bizarre life he imagines living there – everything from three-headed vultures to fleas the size of elephants.</p>
<p>Now, 2,000 years later, we still write stories of epic adventures beyond Earth to meet otherworldly beings (<a href="https://www.britannica.com/topic/The-Hitchhikers-Guide-to-the-Galaxy-novel-by-Adams">Hitchhiker’s Guide</a>, anyone?). Stories like these entertain and inspire, and we are forever trying to find out if science fiction will become science fact.</p>
<h2>Not all alien life is the same</h2>
<p>When looking for life beyond Earth, we are faced with two possibilities. We might find basic microbial life hiding somewhere in our Solar System; or we will identify signals from intelligent life somewhere far away.</p>
<p>Unlike in <a href="https://www.britannica.com/topic/Star-Wars-film-series">Star Wars</a>, we’re not talking far, far away in another galaxy, but rather around other nearby stars. It is this second possibility which really excites me, and should excite you too. A detection of intelligent life would fundamentally change how we see ourselves in the Universe. </p>
<p>In the last 80 years, programs dedicated to the search for extraterrestrial intelligence (SETI) have worked tirelessly searching for cosmic “hellos” in the form of radio signals.</p>
<p>The reason we think any intelligent life would communicate via radio waves is due to the waves’ ability to travel vast distances through space, rarely interacting with the dust and gas in between stars. If anything out there is trying to communicate, it’s a pretty fair bet they would do it through radio waves. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=134&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=134&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=134&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=169&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=169&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=169&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The three radio facilities used in the Breakthrough Listen Initiative. Left to Right: 100m Robert C. Byrd Green Bank Telescope, 64m Murriyang (Parkes) Radio Telescope, 64-antenna MeerKAT array.</span>
<span class="attribution"><span class="source">NRAO, CSIRO, MeerKAT</span></span>
</figcaption>
</figure>
<h2>Listening to the stars</h2>
<p>One of the most exciting searches to date is <a href="https://breakthroughinitiatives.org/initiative/1">Breakthrough Listen</a>, the largest scientific research program dedicated to looking for evidence of intelligent life beyond Earth.</p>
<p>This is one of many projects funded by US-based Israeli entrepreneurs Julia and Yuri Milner, with some serious dollars attached. Over a ten-year period a total amount of <a href="https://breakthroughinitiatives.org/initiative/1">US$100 million</a> will be invested in this effort, and they have a mighty big task at hand. </p>
<p>Breakthrough Listen is currently targeting the closest one million stars in the hope of identifying any unnatural, alien-made radio signals. Using telescopes around the globe, from the 64-metre Murriyang Dish (Parkes) here in Australia, to the 64-antenna MeerKAT array in South Africa, the search is one of epic proportions. But it isn’t the only one. </p>
<p>Hiding away in the Cascade Mountains north of San Francisco sits the <a href="https://www.seti.org/ata">Allen Telescope Array</a>, the first radio telescope built from the ground up specifically for SETI use.</p>
<p>This unique facility is another exciting project, able to search for signals every day of the year. This project is currently upgrading the hardware and software on the original dish, including the ability to target several stars at once. This is a part of the non-profit research organisation, the SETI Institute.</p>
<h2>Space lasers!</h2>
<p>The SETI Institute is also looking for signals that would be best explained as “space lasers”.</p>
<p>Some astronomers hypothesise that intelligent beings might use massive lasers to communicate or even to propel spacecraft. This is because even here on Earth we’re investigating <a href="https://www.nasa.gov/feature/goddard/2022/the-future-of-laser-communications/">laser communication</a> and laser-propelled <a href="https://www.insidescience.org/news/new-light-sail-design-would-use-laser-beam-ride-space">light sails</a>.</p>
<p>To search for these mysterious flashes in the night sky, we need speciality instruments in locations around the globe, which are currently being developed and deployed. This is a research area I’m excited to watch progress and eagerly await results. </p>
<p>As of writing this article, sadly no alien laser signals have been found yet.</p>
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<strong>
Read more:
<a href="https://theconversation.com/do-aliens-exist-we-asked-five-experts-161811">Do aliens exist? We asked five experts</a>
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</em>
</p>
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<h2>Out there, somewhere</h2>
<p>It’s always interesting to ponder who or what might be living out in the Universe, but there is one problem we must overcome to meet or communicate with aliens. It’s the speed of light.</p>
<p>Everything we rely on to communicate via space requires light, and it can only travel so fast. This is where my optimism for finding intelligent life begins to fade. The Universe is big – <em>really</em> big.</p>
<p>To put it in perspective, humans started using radio waves to communicate across large distances in 1901. That <a href="https://ethw.org/Milestones:Reception_of_Transatlantic_Radio_Signals,_1901">first transatlantic signal</a> has only travelled 122 light years, reaching just 0.0000015% of the stars in our Milky Way.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of a spiral galaxy with a box on the lower right corner centred on a tiny blue dot" src="https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The little blue dot in the centre of the square is the current extent of human broadcasts just in our own galaxy.</span>
<span class="attribution"><a class="source" href="https://www.planetary.org/space-images/extent-of-human-radio-broadcasts">Adam Grossman/Nick Risinger</a></span>
</figcaption>
</figure>
<p>Did your optimism just fade too? That is okay, because here is the wonderful thing… we don’t have to find life to know it is out there, somewhere.</p>
<p>When we consider the <a href="https://theconversation.com/how-many-stars-are-there-in-space-165370">trillions of galaxies</a>, septillion of stars, and likely many more planets just in the observable Universe, it feels near impossible that we are alone.</p>
<p>We can’t fully constrain the parameters we need to estimate how many other lifeforms might be out there, as famously proposed by Frank Drake, but using our best estimates and <a href="https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/numerical-testbed-for-hypotheses-of-extraterrestrial-life-and-intelligence/0C97E7803EEB69323C3728F02BA31AFA">simulations</a> the current best answer to this is tens of thousands of possible civilisations out there. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/frank-drake-has-passed-away-but-his-equation-for-alien-intelligence-is-more-important-than-ever-189935">Frank Drake has passed away but his equation for alien intelligence is more important than ever</a>
</strong>
</em>
</p>
<hr>
<p>The Universe <a href="https://theconversation.com/is-space-infinite-we-asked-5-experts-165742">might even be infinite</a>, but that is too much for my brain to comprehend on a weekday.</p>
<h2>Don’t forget the tiny aliens</h2>
<p>So, despite keenly listening for signals, we might not find intelligent life in our lifetimes. But there is hope for aliens yet.</p>
<p>The ones hiding in plain sight, on the planetary bodies of our Solar System. In the coming decades we’ll explore the moons of Jupiter and Saturn like never before, with missions hunting to find traces of basic life.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Jupiter and the icy moon Europa. Concept art of the Europa Clipper mission currently under development.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<p>Mars will continue to be explored – eventually by humans – which could allow us to uncover and retrieve samples from new and unexplored regions.</p>
<p>Even if our future aliens are only tiny microbes, it would still be nice to know we have company in this Universe.</p>
<hr>
<p><em>Correction: this article has been amended to clarify that Julia and Yuri Milner are no longer Russian citizens.</em></p><img src="https://counter.theconversation.com/content/197621/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sara Webb does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>To date, we have not heard from any aliens. Nor have we seen any – but here are the fascinating projects working to change that.Sara Webb, Postdoctoral Research Fellow, Centre for Astrophysics and Supercomputing, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1986942023-02-01T12:08:35Z2023-02-01T12:08:35ZSeti: alien hunters get a boost as AI helps identify promising signals from space<figure><img src="https://images.theconversation.com/files/507097/original/file-20230130-12-qfen8v.jpg?ixlib=rb-1.1.0&rect=672%2C272%2C2956%2C1999&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The new study analysed data gathered at the Green Bank Observatory in West Virginia.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/green-bank-west-virginia-october-15-762059119">Shutterstock</a></span></figcaption></figure><p>An international team of researchers looking for signs of intelligent life in space have used artificial intelligence (AI) to reveal eight promising radio signals in data collected at a US observatory.</p>
<p>The results of their research, <a href="https://www.nature.com/articles/s41550-022-01872-z">published in Nature Astronomy</a> are remarkable. The team hasn’t yet carried out an exhaustive analysis, but the paper suggests the signals have many of the characteristics we would expect if they were artificially generated. In other words, they are the kinds of signals we might pick up from an extraterrestrial civilisation broadcasting into space.</p>
<p>A cursory review of the new paper suggest these are indeed promising signals. They’re much more compelling than what is perhaps the most famous Seti candidate, <a href="https://astronomy.com/news/2020/09/the-wow-signal-an-alien-missed-connectio">the “Wow!” signal</a>, radio emission bearing the hallmarks of an extraterrestrial origin that was collected by an Ohio telescope in 1977.</p>
<p>Realistically, it’s most likely that these eight new signals were generated by human technology. But the real story here is the effectiveness of AI and <a href="https://en.wikipedia.org/wiki/Deep_learning">the techniques used by the team to</a> dig out rare and interesting signals previously buried in the noise of human-generated <a href="https://public.nrao.edu/telescopes/radio-frequency-interference/">radio frequency interference,</a> such as mobile phones and GPS.</p>
<p>Astronomers working in the field of <a href="https://www.seti.org/primer-seti-seti-institute">Seti (the search for extraterrestrial intelligence)</a> must filter out interference produced by radio communications here on Earth.</p>
<p>In this case, Peter Ma from the University of Toronto and his colleagues unleashed a set of algorithms on a mountain of data collected by the <a href="https://greenbankobservatory.org">Green Bank Telescope in West Virginia</a>, US. The data was gathered through a Seti initiative called <a href="https://seti.berkeley.edu/listen/">Breakthrough Listen</a>, established in 2015 by the investor Yuri Milner and his wife Julia. </p>
<p>Here are the characteristics astronomers look for in signals that could be artificially-generated: firstly they are <a href="https://en.wikipedia.org/wiki/Narrowband">narrow-band</a>, which means that where the radio transmission is confined to only a few frequency channels. They also disappear as the telescope is moved to another direction in the sky, and they exhibit <a href="https://en.wikipedia.org/wiki/Doppler_effect">“Doppler drifting”</a>, where the frequency of the signal changes in a predictable way with time. We would expect Doppler drifting because both the transmitter — on a distant planet, for example — and the receiver, on Earth, are moving.</p>
<figure class="align-center ">
<img alt="Artist's impression of exoplanets" src="https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507060/original/file-20230130-22-kadncw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Any artificial signals from deep space need to be distinguished from radio interference here on Earth.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/planets-deep-space-cosmos-nebula-stars-2057080619">Shutterstock</a></span>
</figcaption>
</figure>
<h2>Buried in the noise</h2>
<p>The Breakthrough Listen project’s <a href="https://seti.berkeley.edu/blc1/">first candidate signal</a>, called BLC1, was first announced in 2020. But it was <a href="https://www.nature.com/articles/s41550-021-01508-8">later traced</a> to transmissions associated with cheap electronic devices on this planet. The application of AI techniques to the Breakthrough Listen observing programme, however, is a potential game changer for the field. Even seasoned Seti researchers are beginning to think that we might be on the cusp of a momentous scientific breakthrough.</p>
<p>This may explain renewed interest by groups around the world that are planning for Seti success. For example, a <a href="https://seti.wp.st-andrews.ac.uk">Seti post-detection hub</a> has been set up at the University of St Andrews in Scotland. This will study how humans should react if we discover we are not alone in the Universe.</p>
<p>The International Academy of Astronautics (IAA) <a href="https://iaaseti.org/en/">Seti permanent committee</a> oversees the <a href="https://iaaseti.org/en/protocols/">Seti post-detection protocols</a>, which outline what steps scientists should take in the event of detecting a genuine signal. The IAA has opted to update the text of the protocols sometime later this year.</p>
<p>But the new study highlights a problem with previous signals of interest. When the team took another look at the stars associated with the eight narrow-band transmissions, they could no longer detect the signals. </p>
<p>It would not be surprising if many, and perhaps the vast majority of bona-fide Seti signals, were isolated events. After all, what are the chances that we point our telescopes in exactly the right direction, at the right time and with the right frequency on multiple occasions?</p>
<h2>Missing ingredients</h2>
<p>As I <a href="https://theconversation.com/seti-new-signal-excites-alien-hunters-heres-how-we-could-find-out-if-its-real-152498">argued here</a> a few years ago, Seti surveys would greatly benefit from employing multiple radio telescopes, operating in a manner that’s known as a <a href="https://public.nrao.edu/ask/how-does-a-radio-interferometer-work/">classical interferometer network</a>. </p>
<p>These telescope arrays (groups of several antennas observing together) generate huge amounts of data. With AI onboard, the challenge is perhaps more manageable than previously thought. </p>
<p>Breakthrough Listen is already using telescope arrays such as <a href="https://www.sarao.ac.za/science/meerkat/about-meerkat/">MeerKAT in South Africa</a> for Seti searches. In Europe, researchers have been experimenting with <a href="https://www.evlbi.org">arrays that span the globe</a>.</p>
<p>This European approach would help us isolate signals from human-made interference, give us multiple independent detections of individual events, and permit us to localise signals to individual stars and possibly orbiting planets. </p>
<p>Among the future projects is the <a href="https://www.skao.int/en">Square Kilometre Array</a>, an international project to build the two largest telescope arrays in the world, which will be based in Australia and South Africa. Another upcoming project is the <a href="https://ngvla.nrao.edu">next generation VLA (ngVLA)</a>, a series of linked telescope facilities that will be spread across the United States. These radio telescope arrays will be even more sensitive than current instruments.</p>
<p>It’s my belief — and indeed hope — that somewhere out there intelligent beings are waiting to be discovered. The AI revolution might be the missing ingredient that previous endeavours have lacked. In particular, AI algorithms will eventually evolve into powerful tools that no longer suffer from <a href="https://www.nist.gov/news-events/news/2022/03/theres-more-ai-bias-biased-data-nist-report-highlights">human biases</a>. </p>
<p>Lord Martin Rees, chairman of the Breakthrough Listen advisory board and the astronomer royal, has proposed that if we do find aliens they are likely to be <a href="https://theconversation.com/seti-why-extraterrestrial-intelligence-is-more-likely-to-be-artificial-than-biological-169966">intelligent machines</a> operating in the depths of space, unconstrained by the biological limitations placed on humans. </p>
<p>If we ever do find a bona-fide signal, it could just be that it’s mediated by machines on Earth and in space.</p><img src="https://counter.theconversation.com/content/198694/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Garrett is on the advisory board of the Breakthrough Listen initiative and the Seti Institute.</span></em></p>Can artificial intelligence transform the search for alien intelligence?Michael Garrett, Sir Bernard Lovell chair of Astrophysics and Director of Jodrell Bank Centre for Astrophysics, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1987542023-01-30T19:12:02Z2023-01-30T19:12:02ZAI is helping us search for intelligent alien life – and we’ve found 8 strange new signals<figure><img src="https://images.theconversation.com/files/506973/original/file-20230130-19-jtv92r.png?ixlib=rb-1.1.0&rect=6%2C13%2C1477%2C974&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Midjourney</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Some 540 million years ago, diverse life forms suddenly began to emerge from the muddy ocean floors of planet Earth. This period is known as the Cambrian Explosion, and these aquatic critters are our ancient ancestors. </p>
<p>All complex life on Earth evolved from these underwater creatures. Scientists believe all it took was an ever-so-slight increase in ocean oxygen levels above a certain threshold.</p>
<p>We may now be in the midst of a Cambrian Explosion for artificial intelligence (AI). In the past few years, a burst of incredibly capable AI programs like <a href="https://www.midjourney.com">Midjourney</a>, <a href="https://openai.com/dall-e-2/">DALL-E 2</a> and <a href="https://openai.com/blog/chatgpt/">ChatGPT</a> have showcased the rapid progress we’ve made in machine learning. </p>
<p>AI is now used in virtually all areas of science to help researchers with routine classification tasks. It’s also helping our team of radio astronomers broaden the search for extraterrestrial life, and results so far have been promising.</p>
<h2>Discovering alien signals with AI</h2>
<p>As scientists searching for evidence of intelligent life beyond Earth, we have <a href="https://www.nature.com/articles/s41550-022-01872-z">built an AI system</a> that beats classical algorithms in signal detection tasks. Our AI was trained to search through data from radio telescopes for signals that couldn’t be generated by natural astrophysical processes. </p>
<p>When we fed our AI a previously studied dataset, it discovered eight signals of interest the classic algorithm missed. To be clear, these signals are probably not from extraterrestrial intelligence, and are more likely rare cases of radio interference. </p>
<p>Nonetheless, our findings – <a href="https://www.nature.com/articles/s41550-022-01872-z">published today</a> in Nature Astronomy – highlight how AI techniques are sure to play a continued role in the search for extraterrestrial intelligence.</p>
<figure class="align-center ">
<img alt="An AI-generated image signifying an AI entity searching for extraterrestrial life in space." src="https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/506972/original/file-20230130-217-ye6duz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">AI-based systems are being increasingly used to classify signals found in massive amounts of radio data, helping speed-up the search for alien life.</span>
<span class="attribution"><span class="source">Generated by DALL-E 2</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Not so intelligent</h2>
<p>AI algorithms do not “understand” or “think”. They do excel at pattern recognition, and have proven exceedingly useful for tasks such as classification – but they don’t have the ability to problem solve. They only do the specific tasks they were trained to do.</p>
<p>So although the idea of an AI detecting extraterrestrial intelligence sounds like the plot of an exciting science fiction novel, both terms are flawed: AI programs are not intelligent, and searches for extraterrestrial intelligence can’t find direct evidence of intelligence.</p>
<p>Instead, radio astronomers look for radio “technosignatures”. These hypothesised signals would indicate the presence of technology and, by proxy, the existence of a society with the capability to harness technology for communication.</p>
<p>For our research, we created an algorithm that uses AI methods to classify signals as being either radio interference, or a genuine technosignature candidate. And our algorithm is performing better than we’d hoped.</p>
<h2>What our AI algorithm does</h2>
<p>Technosignature searches have been likened to looking for a needle in a cosmic haystack. Radio telescopes produce huge volumes of data, and in it are huge amounts of interference from sources such as phones, WiFi and satellites. </p>
<p>Search algorithms need to be able to sift out real technosignatures from “false positives”, and do so quickly. Our AI classifier delivers on these requirements. </p>
<p>It was devised by Peter Ma, a University of Toronto student and the lead author on our paper. To create a set of training data, Peter inserted simulated signals into real data, and then used this dataset to train an AI algorithm called an autoencoder. As the autoencoder processed the data, it “learned” to identify salient features in the data.</p>
<p>In a second step, these features were fed to an algorithm called a random forest classifier. This classifier creates decision trees to decide if a signal is noteworthy, or just radio interference – essentially separating the technosignature “needles” from the haystack.</p>
<p>After training our AI algorithm, we fed it more than 150 terabytes of data (480 observing hours) from the Green Bank Telescope in West Virginia. It identified 20,515 signals of interest, which we then had to manually inspect. Of these, eight signals had the characteristics of technosignatures, and couldn’t be attributed to radio interference.</p>
<h2>Eight signals, no re-detections</h2>
<p>To try and verify these signals, we went back to the telescope to re-observe all eight signals of interest. Unfortunately, we were not able to re-detect any of them in our follow-up observations.</p>
<p>We’ve been in similar situations before. In 2020 <a href="https://theconversation.com/a-mysterious-signal-looked-like-a-sign-of-alien-technology-but-it-turned-out-to-be-radio-interference-170548">we detected</a> a signal that turned out to be pernicious radio interference. While we will monitor these eight new candidates, the most likely explanation is they were unusual manifestations of radio interference: not aliens.</p>
<p>Sadly the issue of radio interference isn’t going anywhere. But we will be better equipped to deal with it as new technologies emerge.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-mysterious-signal-looked-like-a-sign-of-alien-technology-but-it-turned-out-to-be-radio-interference-170548">A mysterious signal looked like a sign of alien technology — but it turned out to be radio interference</a>
</strong>
</em>
</p>
<hr>
<h2>Narrowing the search</h2>
<p>Our team recently deployed a <a href="https://breakthroughinitiatives.org/news/38">powerful signal processor</a> on the MeerKAT telescope in South Africa. MeerKAT uses a technique called interferometry to combine its 64 dishes to act as a single telescope. This technique is better able to pinpoint where in the sky a signal comes from, which will drastically reduce false positives from radio interference.</p>
<p>If astronomers do manage to detect a technosignature that can’t be explained away as interference, it would strongly suggest humans aren’t the sole creators of technology within the Galaxy. This would be one of the most profound discoveries imaginable.</p>
<p>At the same time, if we detect nothing, that doesn’t necessarily mean we’re the only technologically-capable “intelligent” species around. A non-detection could also mean we haven’t looked for the right type of signals, or our telescopes aren’t yet sensitive enough to detect faint transmissions from distant exoplanets. </p>
<p>We may need to cross a sensitivity threshold before a Cambrian Explosion of discoveries can be made. Alternatively, if we really are alone, we should reflect on the unique beauty and fragility of life here on Earth.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-asked-astronomers-are-we-alone-in-the-universe-the-answer-was-surprisingly-consistent-132088">We asked astronomers: are we alone in the Universe? The answer was surprisingly consistent</a>
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<hr>
<img src="https://counter.theconversation.com/content/198754/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Danny Price is a senior postdoctoral researcher at the International Centre for Radio Astronomy Research (ICRAR) at Curtin University. He is a member of the Breakthrough Listen initiative to search for intelligent life beyond Earth.</span></em></p>AI’s ability to identify ‘technosignatures’ missed by classical algorithms is an exciting step forward for radio astronomers.Danny C Price, Senior research fellow, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1910542022-10-21T12:38:07Z2022-10-21T12:38:07ZSignatures of alien technology could be how humanity first finds extraterrestrial life<figure><img src="https://images.theconversation.com/files/490943/original/file-20221020-21-mv2tjy.jpg?ixlib=rb-1.1.0&rect=80%2C477%2C3753%2C1678&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Astronomers have been looking for radio waves sent by a distant civilization for more than 60 years.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/illustration-of-signal-coming-out-the-deep-cosmos-royalty-free-image/1338115983?phrase=signal%20coming%20from%20planet%20space&adppopup=true">Rytis Bernotas/iStock via Getty Images</a></span></figcaption></figure><p>If an alien were to look at Earth, many human technologies – from cell towers to fluorescent light bulbs – could be a beacon signifying the presence of life. </p>
<p><a href="https://sites.psu.edu/macyhuston/">We are</a> two <a href="https://sites.psu.edu/astrowright">astronomers</a> <a href="https://scholar.google.com/citations?user=lEUxaaIAAAAJ&hl=en&oi=ao">who</a> work on the <a href="https://www.pseti.psu.edu/about/">search for extraterrestrial intelligence</a> – or SETI. In our research, we try to characterize and detect signs of technology originating from beyond Earth. These are called technosignatures. While scanning the sky for a TV broadcast of some extraterrestrial Olympics may sound straightforward, searching for signs of distant, advanced civilizations is a much more nuanced and difficult task than it might seem.</p>
<h2>Saying ‘hello’ with radios and lasers</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A laser shooting up from an observatory into a starry sky." src="https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=902&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=902&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=902&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490923/original/file-20221020-1663-tvwgzj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A laser – like the one seen here – or beam of radio waves pointed intentionally at Earth would be a strong sign of extraterrestrial life.</span>
<span class="attribution"><a class="source" href="http://www.eso.org/public/images/gerd_huedepohl_4/">G. Hüdepohl/ESO</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The modern scientific <a href="https://astrobites.org/2021/08/16/classic-paper-summary/">search for extraterrestrial intelligence began in 1959</a> when astronomers Giuseppe Cocconi and Philip Morrison showed that radio transmissions from Earth <a href="https://doi.org/10.4159/harvard.9780674366688.c9">could be detected</a> by radio telescopes at interstellar distances. The same year, <a href="https://theconversation.com/frank-drake-has-passed-away-but-his-equation-for-alien-intelligence-is-more-important-than-ever-189935">Frank Drake</a>, launched the first SETI search, <a href="https://www.seti.org/project-ozma">Project Ozma</a>, by pointing a large radio telescope at two nearby Sun-like stars to see if he could detect any radio signals coming from them. Following the invention of the laser in 1960, astronomers showed that visible light could also <a href="https://doi.org/10.1038/190205a0">be detected from distant planets</a>.</p>
<p>These first, foundational attempts to detect <a href="http://www.bigear.org/oldseti.htm">radio</a> or <a href="https://doi.org/110.1086/423300">laser</a> signals from another civilization were all looking for focused, powerful signals that would have been intentionally sent to the solar system and meant to be found. </p>
<p>Given the technological limitations of the 1960s, astronomers did not give serious thought to searching for broadcast signals – like television and radio broadcasts on Earth – that would leak into space. But a beam of a radio signal, with all of its power focused towards Earth, could be detectable from much farther away – just picture the difference between a laser and a weak light bulb.</p>
<p>The search for intentional radio and laser signals is still one of the most popular SETI strategies today. However, this approach <a href="https://www.universetoday.com/149513/beyond-fermis-paradox-xvii-what-is-the-seti-paradox-hypothesis/">assumes that extraterrestrial civilizations want to communicate</a> with other technologically advanced life. Humans very rarely send targeted signals into space, and some scholars argue that intelligent species may <a href="https://theconversation.com/blasting-out-earths-location-with-the-hope-of-reaching-aliens-is-a-controversial-idea-two-teams-of-scientists-are-doing-it-anyway-182036">purposefully avoid broadcasting out their locations</a>. This search for signals that no one may be sending is called <a href="https://doi.org/10.48550/arXiv.physics/0611283">the SETI Paradox</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial view of a desert with a huge number of satellite dishes." src="https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490932/original/file-20221020-1690-8mwnqz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This artist’s impression shows the Square Kilometer Array, a telescope array currently being built in both Australia and Africa that will be sensitive enough to detect the equivalent of radio broadcasts from distant planets.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:SKA_overview.jpg#/media/File:SKA_overview.jpg">SPDO/TDP/DRAO/Swinburne Astronomy Productions/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Leaking radio waves</h2>
<p>Though humans don’t transmit many intentional signals out to the cosmos, many technologies people use today produce a lot of radio transmissions that leak into space. Some of these signals would be detectable if they came from a nearby star.</p>
<p>The worldwide network of television towers constantly emits signals in many directions that leak into space and can <a href="https://doi.org/10.1126/science.199.4327.377">accumulate into a detectable, though relatively faint</a>, radio signal. Research is ongoing as to whether current emissions from cell towers in the radio frequency on Earth would be detectable using today’s telescopes, but the upcoming <a href="https://doi.org/10.1088/1475-7516/2007/01/020">Square Kilometer Array radio telescope will be able to detect</a> even fainter radio signals with <a href="https://theconversation.com/the-science-behind-the-square-kilometre-array-40870">50 times the sensitivity of current radio telescope arrays</a>. </p>
<p>Not all human-made signals are so unfocused, though. Astronomers and space agencies use beams of radio waves to communicate with <a href="https://www.nasa.gov/directorates/heo/scan/services/networks/deep_space_network/about">satellites and space craft</a> in the solar system. Some researchers also use radio waves for <a href="https://www.nasa.gov/feature/jpl/planetary-radar-observes-1000th-near-earth-asteroid-since-1968">radar to study asteroids</a>. In both of these cases, the radio signals are more focused and pointed out into space. Any extraterrestrial civilization that happened to be in the line of sight of these beams could likely detect these unambiguously artificial signals.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rendering of a massive set of rings around a star in space." src="https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490926/original/file-20221020-18-l76626.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A Dyson Sphere is a theoretical megastructure that would surround a star and collect its light to use as energy.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kevinmgill/29401385502/">Kevin Gill/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Finding megastructures</h2>
<p>Aside from finding an actual alien spacecraft, radio waves are the most common technosignatures featured in sci-fi movies and books. But they are not the only signals that could be out there.</p>
<p>In 1960, astronomer Freeman Dyson theorized that, since stars are by far the most powerful energy source in any planetary system, a technologically advanced civilization might <a href="https://doi.org/10.1088/10.1126/science.131.3414.1667">collect a significant portion of the star’s light as energy</a> with what would essentially be a massive solar panel. Many astronomers call these megastructures, and there are a few ways to detect them.</p>
<p>After using the energy in the captured light, the technology of an advanced society would <a href="https://stem.guide/topic/entropy-the-second-law-of-thermodynamics/">re-emit some of the energy as heat</a>. Astronomers have shown that this heat <a href="https://ui.adsabs.harvard.edu/abs/1966ApJ...144.1216S/abstract">could be detectable</a> as extra infrared radiation coming from a star system.</p>
<p>Another possible way to find a megastructure would be to <a href="https://theconversation.com/what-are-the-odds-of-an-alien-megastructure-blocking-light-from-a-distant-star-49311">measure its dimming effect on a star</a>. Specifically, large artificial satellites orbiting a star would periodically block some of its light. This would appear as dips in the star’s apparent brightness over time. Astronomers could detect this effect similarly to how <a href="https://theconversation.com/are-there-any-planets-outside-of-our-solar-system-164062">distant planets are discovered today</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's depiction of a planet covered in cities and with a chemically altered atmosphere." src="https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=495&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=495&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=495&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=622&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=622&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490924/original/file-20221020-13-90h06v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=622&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Advanced civilizations may produce a lot of pollution in the form of chemicals, light and heat that can be detected across the vast distances of space.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/press-release/goddard/2021/technosignature">NASA/Jay Freidlander</a></span>
</figcaption>
</figure>
<h2>A whole lot of pollution</h2>
<p>Another technosignature that astronomers have thought about is pollution.</p>
<p>Chemical pollutants – like <a href="https://www.nasa.gov/press-release/goddard/2021/technosignature">nitrogen dioxide</a> and <a href="https://doi.org/10.3847/PSJ/ac5404">chlorofluorocarbons</a> on Earth are almost exclusively produced by human industry. It is possible to detect these molecules in the <a href="https://theconversation.com/its-all-in-the-atmosphere-exploring-planets-orbiting-distant-stars-62034">atmospheres of exoplanets</a> with the same method the James Webb Space Telescope is using to <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">search distant planets for signs of biology</a>. If astronomers find a planet with an atmosphere filled with chemicals that can only be produced by technology, it may be a sign of life.</p>
<p>Finally, <a href="https://doi.org/10.1093/mnras/stac469">artificial light</a> or <a href="https://doi.org/10.1017/S1473550414000585">heat from cities and industry</a> could also be detectable with large optical and infrared telescopes, as would a large <a href="https://doi.org/10.3847/1538-4357/aaae66">number of satellites orbiting a planet</a>. But a civilization would need to produce far more heat, light and satellites than Earth does to be detectable across the vastness of space using technology humans currently possess.</p>
<h2>Which signal is best?</h2>
<p>No astronomer has ever found a confirmed technosignature, so it’s hard to say what will be the first sign of alien civilizations. While many astronomers have thought a lot about <a href="https://doi.org/10.1017/S1473550419000284">what might make for a good signal</a>,
ultimately, nobody knows what extraterrestrial technology might look like and what signals are out there in the Universe. </p>
<p>Some astronomers support a <a href="https://www.aspbooks.org/publications/213/519.pdf">generalized SETI</a> approach which searches for anything in space that current scientific knowledge cannot naturally explain. Some, like us, continue to search for both intentional and unintentional technosignatures. The bottom line is that there are many avenues for detecting distant life. Since no one knows what approach is likely to succeed first, there is still a lot of exciting work left to do.</p><img src="https://counter.theconversation.com/content/191054/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Wright does research supported by the Penn State Extraterrestrial Intelligence Center. He also does SETI research and runs conferences dedicated to SETI with funds from NASA and the NSF.</span></em></p><p class="fine-print"><em><span>Macy Huston does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The technology of an advanced alien civilization is likely to produce many signs that could be detected across the vastness of space. Two astronomers explain the search for technosignatures.Macy Huston, PhD Candidate in Astronomy and Astrophysics, Penn StateJason Wright, Professor of Astronomy and Astrophysics, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1899352022-09-05T13:47:40Z2022-09-05T13:47:40ZFrank Drake has passed away but his equation for alien intelligence is more important than ever<figure><img src="https://images.theconversation.com/files/482721/original/file-20220905-26-uhmq7a.jpg?ixlib=rb-1.1.0&rect=14%2C0%2C1977%2C1130&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The spiral galaxy M74 imaged by the NASA/ESA JWST.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasawebbtelescope/52324826014/in/album-72177720301006030/">ESA/Webb, NASA & CSA, J. Lee and the PHANGS-JWST Team.</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>How many intelligent civilisations should there be in our galaxy right now? In 1961, the US astrophysicist Frank Drake, who passed away on September 2 at the age of 92, came up with an <a href="https://theconversation.com/where-is-everybody-doing-the-maths-on-extraterrestrial-life-3390">equation to estimate this</a>. The Drake equation, dating from a stage in his career when he was “too naive to be nervous” (as he later put it), has become famous and bears his name.</p>
<p>This places Drake in the company of towering physicists with equations named after them including James Clerk Maxwell and Erwin Schrödinger. Unlike those, Drake’s equation does not encapsulate a law of nature. Instead it combines some poorly known probabilities into an informed estimate. </p>
<p>Whatever reasonable values you feed into the equation (see image below) it is hard to avoid the conclusion that we shouldn’t be alone in the galaxy. Drake remained a proponent and a supporter of the search for extraterrestrial life throughout his days, but has his equation really taught us anything?</p>
<figure class="align-center ">
<img alt="N = R∗ ⋅ fp ⋅ ne ⋅ fl ⋅ fi ⋅ fc ⋅ L" src="https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=242&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=242&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=242&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=304&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=304&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482606/original/file-20220903-13447-vjbyw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=304&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The expanded Drake equation.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Drake’s equation may look complicated, but its principles are really rather simple. It states that, in a galaxy as old as ours, the number of civilisations that are detectable by virtue of them broadcasting their presence must equate to the rate at which they arise, multiplied by their average lifetime.</p>
<p>Putting a value on the rate at which civilisations occur might seem to be guesswork, but Drake realised that it can be broken down into more tractable components.</p>
<p>He stated that the total rate is equal to the rate at which suitable stars are formed, multiplied by the fraction of those stars that have planets. This is then multiplied by the number of planets that are capable of bearing life per system, times the fraction of those planets where life gets started, multiplied by the fraction of those where life becomes intelligent, times the fraction of those that broadcast their presence.</p>
<h2>Tricky values</h2>
<figure class="align-right ">
<img alt="Frank Drake." src="https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=775&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=775&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=775&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=973&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=973&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482781/original/file-20220905-2133-j7iuee.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=973&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Frank Drake.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>When Drake first formulated his equation, the only term that was known with any confidence was the rate of star formation – about 30 per year. </p>
<p>As for the next term, back in the 1960s, we had no evidence that any other stars have planets, and one in ten may have seemed like an optimistic guess. However, observational discoveries of exoplanets (planets orbiting other stars) that began in the 1990s and <a href="https://theconversation.com/more-than-1-000-new-exoplanets-discovered-but-still-no-earth-twin-59274">have blossomed this century</a> now makes us confident that most stars have planets. </p>
<p>Common sense suggests that most systems of multiple planets would include one at the right distance from its star to be capable of supporting life. Earth is that planet in our solar system. In addition, Mars may have been suitable for abundant life in the past – and it <a href="https://theconversation.com/mars-mounting-evidence-for-subglacial-lakes-but-could-they-really-host-life-146732">could still be clinging on</a>. </p>
<p>Today we also realise that planets don’t need to be warm enough for liquid water to exist at the surface to support life. It can occur <a href="https://theconversation.com/nasa-considers-sending-swimming-robots-to-habitable-ocean-worlds-of-the-solar-system-186228">in the internal ocean of an ice-covered body</a>, supported by heat generated either by radioctivity or tides rather than sunlight. </p>
<p>There are several likely candidates among the moons of Jupiter and Saturn, for example. In fact, when we add moons as being capable of hosting life, the average number of habitable bodies per planetary system could easily exceed one. </p>
<p>The values of the terms towards the right hand side of the equation, however, remain more open to challenge. Some would hold that, given a few million years to play with, life will get started anywhere that is suitable.</p>
<p>That would be mean that the fraction of suitable bodies where life actually gets going is pretty much equal to one. Others say that we have as yet no proof of life starting anywhere other than Earth, and that the origin of life could actually be an exceedingly rare event.</p>
<p>Will life, once started, eventually evolve intelligence? It probably has to get past the microbial stage and become multicellular first. </p>
<p>There is evidence that <a href="https://www.nature.com/scitable/content/multicellularity-evolved-from-multiple-independent-origins-14458921/">multicellular life started more than once</a> on Earth, so becoming multicellular may not be a barrier. Others, however, point out that on Earth the <a href="https://theconversation.com/evolution-tells-us-we-might-be-the-only-intelligent-life-in-the-universe-124706">“right kind” of multicellular life</a>, which continued to evolve, appeared only once and could be rare on the galactic scale. </p>
<p>Intelligence may confer a competitive advantage over other species, meaning its evolution could be rather likely. But we don’t know for sure. </p>
<p>And will intelligent life develop technology to the stage where it (accidentally or deliberately) broadcasts its existence across space? Perhaps for surface-dwellers such as ourselves, but it might be rare for inhabitants of internal oceans of frozen worlds with no atmosphere.</p>
<h2>How long do civilisations last?</h2>
<p>What about the average lifetime of a detectable civilisation, <em>L</em>? Our TV transmissions began to make Earth detectable from afar in the 1950s, giving a minimum value for <em>L</em> of about 70 years in our own case. </p>
<p>In general though, <em>L</em> may be limited by the collapse of civilisation (what are the odds of our own lasting a further 100 years?) or by the near total demise of radio broadcasting in favour of the internet, or by a <a href="https://theconversation.com/blasting-out-earths-location-with-the-hope-of-reaching-aliens-is-a-controversial-idea-two-teams-of-scientists-are-doing-it-anyway-182036">deliberate choice to “go quiet”</a> for fear of hostile galactic inhabitants.</p>
<p>Play with the numbers yourself - it’s fun! You’ll find that if <em>L</em> is more than 1,000 years, <em>N</em> (the number of detectable civilisations) is likely to be greater than a hundred. In <a href="https://www.youtube.com/watch?v=_RcMrb9ve_k">an interview recorded in 2010</a>, Drake said his best guess at <em>N</em> was about 10,000.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/_RcMrb9ve_k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>We are learning more about exoplanets every year, and are entering an era when <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">measuring their atmospheric composition</a> to reveal evidence of life is becoming increasingly feasible. Within the next decade or two, we can hope for a much more soundly based estimate of the fraction of Earth-like planets where life gets started. </p>
<p>This won’t tell us about life in the internal oceans, but we can hope for insights into that from missions to the icy moons of <a href="https://theconversation.com/europa-there-may-be-life-on-jupiters-moon-and-two-new-missions-will-pave-the-way-for-finding-it-122551">Jupiter</a>, <a href="https://theconversation.com/nasa-saturn-moon-enceladus-is-able-to-host-life-its-time-for-a-new-mission-76102">Saturn</a> and <a href="https://theconversation.com/jupiter-saturn-uranus-neptune-why-our-next-visit-to-the-giant-planets-will-be-so-important-and-just-as-difficult-175918">Uranus</a>. And we could, of course, detect actual signals from extraterrestrial intelligence.</p>
<p>Either way, Frank Drake’s equation, which has stimulated so many lines of research, will continue to give us a thought-provoking sense of perspective. For that we should be grateful.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/seti-why-extraterrestrial-intelligence-is-more-likely-to-be-artificial-than-biological-169966">Seti: why extraterrestrial intelligence is more likely to be artificial than biological</a>
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<img src="https://counter.theconversation.com/content/189935/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Rothery is Professor of Planetary Geosciences at the Open University. He is co-leader of the European Space Agency's Mercury Surface and Composition Working Group, and a Co-Investigator on MIXS (Mercury Imaging X-ray Spectrometer) that is now on its way to Mercury on board the European Space Agency's Mercury orbiter BepiColombo. He has received funding from the UK Space Agency and the Science & Technology Facilities Council for work related to Mercury and BepiColombo, and from the European Commission under its Horizon 2020 programme for work on planetary geological mapping (776276 Planmap). He is author of Planet Mercury - from Pale Pink Dot to Dynamic World (Springer, 2015), Moons: A Very Short Introduction (Oxford University Press, 2015) and Planets: A Very Short Introduction (Oxford University Press, 2010). He is Educator on the Open University's free learning Badged Open Course (BOC) on Moons and its equivalent FutureLearn Moons MOOC, and chair of the Open University's level 2 course on Planetary Science and the Search for Life.</span></em></p>Research on exoplanets over the next couple of decades could help us more accurately estimate how many intelligent alien civilisations there are in our galaxy.David Rothery, Professor of Planetary Geosciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1851652022-06-16T04:37:39Z2022-06-16T04:37:39ZDid a giant radio telescope in China just discover aliens? Not so FAST…<blockquote>
<p>“Extraordinary claims require extraordinary evidence.”<br>
– <cite>Carl Sagan (Cosmos, 1980)</cite></p>
</blockquote>
<p>This phrase is the <a href="https://en.wikipedia.org/wiki/Sagan_standard">standard</a> that astronomers will be applying to a curious signal captured with China’s “Sky Eye” telescope that <em>might</em> be a transmission from alien technology. </p>
<p>An article reporting the signal was posted on the website of China’s state-backed Science and Technology Daily newspaper, <a href="https://www.bloomberg.com/news/articles/2022-06-15/china-says-it-may-have-detected-signals-from-alien-civilizations">but was later removed.</a> So have astronomers finally found evidence of intelligent found life beyond Earth? And is it being hushed up?</p>
<p>We should be intrigued, but not too excited (yet). An interesting signal has to go through a lot of tests to check whether it truly carries the signature of extraterrestrial technology or is just the result of an unexpected source of terrestrial interference. </p>
<p>And as for the deletion: media releases are normally timed for simultaneous release with peer-reviewed results – which are not yet available – so it was likely just released a bit early by mistake. </p>
<h2>An eye on the sky</h2>
<p>Sky Eye, which is offically known as the <a href="https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Spherical_Telescope">Five-hundred-meter Aperture Spherical Telescope (FAST)</a>, is the the largest and most sensitive single-dish radio telescope in the world. A engineering marvel, its gargantuan structure is built inside a natural basin in the mountains of <a href="https://goo.gl/maps/wd25oAxVWSV9Ddnf8">Guizhou, China</a>. </p>
<p>The telescope is so huge it can’t be physically tilted, but it can be pointed in a direction by thousands of actuators that deform the telescope’s reflective surface. By deforming the surface, the location of the telescope’s focal point changes, and the telescope can look at a different part of the sky.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/china-completes-worlds-largest-radio-telescope-raising-hopes-of-finding-new-worlds-and-alien-life-62237">China completes world's largest radio telescope – raising hopes of finding new worlds and alien life</a>
</strong>
</em>
</p>
<hr>
<p>FAST detects radiation at radio wavelengths (up to 10 cm) and is used for astronomical research in a wide range of areas. One area is the search for extraterrestrial intelligence, or SETI. </p>
<p>SETI observations are mainly done in “piggy-back” mode, which means they are taken while the telescope is also running its primary science programs. In this way, large swaths of the sky can be scanned for signs of alien technology – or “technosignatures” – without getting in the way of other science operations. For special targets like nearby exoplanets, dedicated SETI observations are still carried out.</p>
<h2>The hunt for alien technology</h2>
<p>Technosignature searches have been ongoing since the 1960s, when the American astronomer <a href="https://en.wikipedia.org/wiki/Frank_Drake">Frank Drake</a> pointed the <a href="https://public.nrao.edu/telescopes/tatel/">26-metre Tatel telescope</a> toward two nearby Sun-like stars and scanned them for signs of technology. </p>
<p>Over the years, technosignature searches have become far more rigorous and sensitive. The systems in place at FAST are also able to process billions of times more of the radio spectrum than Drake’s experiment. </p>
<p>Despite these advances, we haven’t yet found any evidence of life beyond Earth.</p>
<p>FAST sifts through enormous amounts of data. The telescope feeds 38 billion samples a second into a cluster of high-performance computers, which then produces exquisitely detailed charts of incoming radio signals. These charts are then searched for signals that look like technosignatures. </p>
<p>With such a large collecting area, FAST can pick up incredibly faint signals. It is about 20 times more sensitive than Australia’s Murriyang telescope at the Parkes Radio Observatory. FAST could easily detect a transmitter on a nearby exoplanet with a similar output power to radar systems we have here on Earth. </p>
<h2>The trouble with sensitivity</h2>
<p>The trouble with being so sensitive is that you can uncover radio interference that would otherwise be too faint to detect. We SETI researchers have had this problem before. </p>
<p>Last year, using Murriyang, we detected an extremely interesting signal we called <a href="https://theconversation.com/a-mysterious-signal-looked-like-a-sign-of-alien-technology-but-it-turned-out-to-be-radio-interference-170548">BLC1</a>. </p>
<p>However, it turned out to be very strange interference (not aliens). To uncover its true nature, we had to develop a <a href="https://seti.berkeley.edu/blc1/flowchart.html">new verification framework</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Technosignature verification flowchart" src="https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469059/original/file-20220615-3512-8jqevi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A flowchart for verifying candidate technosignatures, developed for BLC1.</span>
<span class="attribution"><span class="source">Sofia Sheikh (SETI Institute)</span></span>
</figcaption>
</figure>
<p>With BLC1, it took about a year from when it was initially reported to when peer-reviewed analysis was published. Similarly, we may need to wait a while for the FAST signal to be analysed in depth. </p>
<p>Professor Zhang Tongjie, chief scientist for the China Extraterrestrial Civilization Research Group, acknowledged this in the Science & Technology Daily report: </p>
<blockquote>
<p>The possibility that the suspicious signal is some kind of radio interference is also very high, and it needs to be further confirmed and ruled out. This may be a long process.</p>
</blockquote>
<p>And we may need to get used to a gap between finding candidate signals and verifying them. FAST and other telescopes are likely to find many more signals of interest. </p>
<p>Most of these will turn out to be interference, but some may be new astrophysical phenomena, and some may be <em>bona fide</em> technosignatures.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-mysterious-signal-looked-like-a-sign-of-alien-technology-but-it-turned-out-to-be-radio-interference-170548">A mysterious signal looked like a sign of alien technology — but it turned out to be radio interference</a>
</strong>
</em>
</p>
<hr>
<h2>Stay intrigued</h2>
<p>Will FAST’s extraordinary signals meet the burden of extraordinary evidence? Until their work is reviewed and published, it’s still too early to say, but it’s encouraging that their SETI search algorithms are finding curious signals. </p>
<p>Between FAST, the <a href="https://breakthroughinitiatives.org/initiative/1">Breakthrough Listen</a> initiative, and the SETI Institute’s <a href="https://www.seti.org/press-release/cosmic-all-antennas-very-large-array-ready-stream-data-technosignature-research">COSMIC</a> program, the SETI field is seeing a lot of interest and activity. And it’s not just radio waves: searches are also underway using <a href="https://oirlab.ucsd.edu/PANOSETI.html">optical and infrared light</a>. </p>
<p>As for right now: stay intrigued, but don’t get too excited.</p><img src="https://counter.theconversation.com/content/185165/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Danny C Price is Australian Project Scientist for the Breakthrough Listen initiative.</span></em></p>Have astronomers finally found evidence of intelligent found life beyond Earth?Danny C Price, Senior research fellow, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1834462022-05-23T03:33:48Z2022-05-23T03:33:48ZDid NASA find a mysterious doorway on Mars? No, but that’s no reason to stop looking<figure><img src="https://images.theconversation.com/files/464681/original/file-20220522-20-amoytm.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C1326%2C1174&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://mars.nasa.gov/raw_images/1064629/">NASA/JPL-Caltech/MSSS</a></span></figcaption></figure><p>For the past ten years, <a href="https://mars.nasa.gov/msl/home/">NASA’s Curiosity rover</a> has been trundling around the surface of Mars, taking photos in its quest to understand the history and geology of the red planet and perhaps even find signs of life. </p>
<p>Last week it took a photo which appeared to show a doorway carved into the rock. It’s the sort of thing that on Earth might indicate an underground bunker, such as an air-raid shelter. </p>
<h2>Seeing is not always believing</h2>
<p>At first sight, the picture is totally convincing. At second sight, maybe not. The passage seems to go in only a short way before the steeply descending roof meets the floor. </p>
<p>And then those killjoys at NASA tell us its only about 45 cm high. Still, who said Martians had to be the same height as us? But <em>then</em> <a href="https://mars.nasa.gov/resources/26754/door-shaped-fracture-spotted-by-curiosity-at-east-cliffs/">geologists point out</a> several straight-line fractures can be seen in this site, and the “doorway” is where they happen to intersect. </p>
<p>Such a pity. It would have been so exciting if it had been a real doorway. Instead it joins the <a href="https://en.wikipedia.org/wiki/Cydonia_(Mars)#%22Face_on_Mars%22">face on Mars</a>, the <a href="https://mars.nasa.gov/resources/7457/spooner-or-later/?site=msl">spoon on Mars</a>, the <a href="https://www.nytimes.com/2022/01/07/science/moon-cube-china-rover.html">cube on the Moon</a>, and all the other things seen in photos from space that turn out not to be as exciting as we thought. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=174&fit=crop&dpr=1 600w, https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=174&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=174&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=218&fit=crop&dpr=1 754w, https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=218&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/464683/original/file-20220522-56160-gdlrix.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=218&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The face on Mars, the spoon on Mars, and the cube on the Moon. On closer examination, each turned out to be a natural geological formation.</span>
<span class="attribution"><span class="source">NASA, NASA, CNSA</span></span>
</figcaption>
</figure>
<h2>Faces in the clouds</h2>
<p>Worse, the “doorway” joins the even longer list of wacky images like the <a href="https://www.theage.com.au/national/victoria/flaky-bidders-battle-over-corny-piece-of-australiana-20110909-1k0ka.html">cornflake that looks like Australia</a>, the <a href="https://en.wikipedia.org/wiki/Cats_That_Look_Like_Hitler">cats that look like Hitler</a>, and so on. And who hasn’t seen a face in the clouds?</p>
<p>The sad fact is that when presented with an unclear or unfamiliar image, humans try to turn it into a familiar-looking object. Scientists call our tendency to do this “<a href="https://en.wikipedia.org/wiki/Pareidolia">pareidolia</a>”. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/holy-grilled-cheese-sandwich-what-is-pareidolia-14170">Holy grilled cheese sandwich! What is pareidolia?</a>
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<p>It’s easy to understand why it happens. We <a href="https://newsroom.unsw.edu.au/news/science-tech/why-brain-programmed-see-faces-everyday-objects">likely evolved this tendency</a> because spotting important things like predators or faces, even when the light is poor or they are partly obscured, gave us an advantage. And getting false positives – seeing a predator where there is none – is better than not seeing a predator who then eats you.</p>
<h2>No signs of life</h2>
<p>Reasonable explanations won’t deter the <a href="https://www.telegraph.co.uk/news/2022/05/12/doorway-mars-leads-fresh-conspiracy-theories-scientists-quickly/">conspiracy theorists</a> who say the doorway really is evidence of life on Mars, and maintain that scientists are engaged in some sort of cover-up. </p>
<p>If I were trying to do a cover-up, I wouldn’t be releasing the photos! So a conspiracy doesn’t seem very likely.</p>
<p>But there’s also a lesson here for serious searchers for alien life. As astronomer <a href="https://en.wikipedia.org/wiki/Carl_Sagan">Carl Sagan</a> said, extraordinary claims require extraordinary evidence. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-search-for-et-has-been-going-on-for-years-so-what-do-we-know-so-far-44966">The search for ET has been going on for years: so what do we know so far?</a>
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<p>Following this maxim, scientists seeking evidence of extra-terrestrial life demand much stronger evidence, than, say, someone looking for a geological formation. And despite decades of searching for evidence of life on Mars, we have found nothing. </p>
<p>It is still possible there may once have been life on Mars. We may yet find some fossilised relics of ancient cellular life. But suddenly finding an artefact such as a doorway, or a spoon, seems unlikely. </p>
<h2>The bigger picture</h2>
<p>There’s a similar story with the broader <a href="https://en.wikipedia.org/wiki/Search_for_extraterrestrial_intelligence">search for extra-terrestrial intelligence (SETI)</a>. For years, SETI scientists have been searching the skies for signals from other civilisations, but so far we have found nothing. But nearly all our searches have been on the nearest few stars, and so in a sense the search has barely started. </p>
<p>Meanwhile, we continue to be bombarded with photos purporting to show UFOs (Unidentified Flying Objects) or <a href="https://theconversation.com/is-there-evidence-aliens-have-visited-earth-heres-whats-come-out-of-us-congress-hearings-on-unidentified-aerial-phenomena-183443">UAP (Unidentified Aerial Phenomena)</a>. </p>
<p>The vast majority of these photos are probably fakes, or mistaken photos of familiar objects such as weather balloons. But as scientists, we must keep an open mind. In among the rubbish, perhaps there may be one or two photos or videos that really could stretch our current knowledge. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-there-evidence-aliens-have-visited-earth-heres-whats-come-out-of-us-congress-hearings-on-unidentified-aerial-phenomena-183443">Is there evidence aliens have visited Earth? Here's what's come out of US congress hearings on 'unidentified aerial phenomena'</a>
</strong>
</em>
</p>
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<p>The problem is that if someone presents me with a photo purporting to show a flying saucer, I know that the odds overwhelmingly favour it being a fake, and so I’m likely to dismiss it rather than wasting my time examining it carefully. But supposing I’m wrong?</p>
<p>Similarly, when we see a doorway, or a face, or a spoon, on Mars, it’s all too easy to dismiss it out of hand. But we must remain alert to the possibility that one day we might find archaeological evidence of past life on Mars. </p>
<p>Admittedly, this seems very unlikely. But not impossible. It would be a terrible loss if, among all our careful searching through the data, we missed the thing we had been searching for because it was too easily dismissed as a trick of the light.</p><img src="https://counter.theconversation.com/content/183446/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ray Norris does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A photo of ‘doorway’ on Mars shows how ready our minds are to see significance and signs of life in the natural world.Ray Norris, Professor, School of Science, Western Sydney UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1820362022-04-29T12:25:25Z2022-04-29T12:25:25ZBlasting out Earth’s location with the hope of reaching aliens is a controversial idea – two teams of scientists are doing it anyway<figure><img src="https://images.theconversation.com/files/460137/original/file-20220427-22-fkbhja.jpg?ixlib=rb-1.1.0&rect=377%2C0%2C3616%2C1209&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists think there are 300 million habitable planets in the Milky Way, and some may be home to intelligent life.</span> <span class="attribution"><a class="source" href="http://www.eso.org/public/images/milkyway/">Bruno Gilli/ESO</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>If a person is lost in the wilderness, they have two options. They can search for civilization, or they could make themselves easy to spot by building a fire or writing HELP in big letters. For scientists interested in the question of whether intelligent aliens exist, the options are much the same.</p>
<hr>
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<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/uk/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<p>For over 70 years, astronomers have been scanning for radio or optical signals from other civilizations in the search for extraterrestrial intelligence, called <a href="https://www.seti.org/">SETI</a>. Most scientists are confident that life exists on many of the <a href="https://www.nasa.gov/feature/ames/kepler-occurrence-rate">300 million potentially habitable worlds</a> in the Milky Way galaxy. Astronomers also think there is a <a href="https://www.scientificamerican.com/article/how-many-aliens-are-in-the-milky-way-astronomers-turn-to-statistics-for-answers/">decent chance some life forms have developed intelligence and technology</a>. But no signals from another civilization have ever been detected, a mystery that is called “<a href="https://earthsky.org/space/meti-workshop-in-paris-fermis-paradox-great-silence/">The Great Silence</a>.” </p>
<p>While SETI has long been a part of mainstream science, <a href="http://meti.org/">METI</a>, or messaging extraterrestrial intelligence, has been less common.</p>
<p>I’m a <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">professor of astronomy</a> who has written extensively about the search for life in the universe. I also serve on the advisory council for a nonprofit research organization that’s <a href="http://meti.org/en/advisors">designing messages to send to extraterrestrial civilizations</a>.</p>
<p>In the coming months, two teams of astronomers are going to send messages into space in an attempt to <a href="https://www.universetoday.com/155061/astronomers-come-up-with-a-new-message-to-let-the-aliens-know-were-here/">communicate with any intelligent aliens</a> who may be out there listening.</p>
<p>These efforts are like building a big bonfire in the woods and hoping someone finds you. But some people question whether it is wise to do this at all.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A gold plaque with the shape of a man and a woman and some lines depicting the solar system." src="https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=472&fit=crop&dpr=1 600w, https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=472&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=472&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=593&fit=crop&dpr=1 754w, https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=593&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/460140/original/file-20220427-24-lnf43y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=593&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Pioneer 10 spacecraft carries this plaque, which describes some basic information about humans and the Earth.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Pioneer10-plaque_tilt.jpg#/media/File:Pioneer10-plaque_tilt.jpg">Carl Sagan, Frank Drake, Linda Salzman Sagan, NASA Ames Research Center via WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>The history of METI</h2>
<p>Early attempts to contact life off Earth were quixotic messages in a bottle. </p>
<p>In 1972, NASA launched the Pioneer 10 spacecraft toward Jupiter carrying a <a href="https://www.planetary.org/articles/0120-the-pioneer-plaque-science-as-a-universal-language">plaque with a line drawing of a man and a woman</a> and symbols to show where the craft originated. In 1977, NASA followed this up with the famous <a href="https://voyager.jpl.nasa.gov/golden-record/">Golden Record</a> attached to the <a href="https://theconversation.com/voyager-golden-records-40-years-later-real-audience-was-always-here-on-earth-79886">Voyager 1 spacecraft</a>.</p>
<p>These spacecraft – as well as their twins, Pioneer 11 and Voyager 2 – have now all <a href="https://www.space.com/43158-what-spacecraft-will-enter-interstellar-space-next.html">travelled well past the orbits of the outer planets</a>. But in the immensity of space, the odds that these or any other physical objects will be found are fantastically minuscule. </p>
<p>Electromagnetic radiation is a much more effective beacon.</p>
<p>Astronomers beamed the first radio message designed for alien ears from the <a href="https://www.naic.edu/ao/landing">Arecibo Observatory</a> in Puerto Rico in 1974. The <a href="http://www.naic.edu/challenge/about-message.html">series of 1s and 0s</a> was designed to convey simple information about humanity and biology and was sent toward the globular cluster M13. Since M13 is 25,000 light-years away, you shouldn’t hold your breath for a reply.</p>
<p>In addition to these purposeful attempts at sending a message to aliens, wayward signals from television and radio broadcasts have been leaking into space for nearly a century. This ever-expanding bubble of earthly babble has already reached millions of stars. But there is a big difference between a focused blast of radio waves from a giant telescope and diffuse leakage – the weak <a href="https://www.npr.org/sections/krulwich/2011/08/05/89700174/lucys-laugh-enlivens-the-solar-system">signal from a show like “I Love Lucy”</a> fades below the hum of radiation left over from the Big Bang soon after it leaves the solar system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A giant spherical dish-shaped telescope on the top of a mountain." src="https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/460135/original/file-20220427-17-yuvu1q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The new FAST telescope in China is the largest radio telescope ever built and will be used to send a message toward the center of the galaxy.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/march-31-2021-aerial-photo-taken-on-march-31-2021-shows-news-photo/1232035199?adppopup=true">Ou Dongqu/Xinhua via Getty Images</a></span>
</figcaption>
</figure>
<h2>Sending new messages</h2>
<p>Nearly half a century after the Arecibo message, two international teams of astronomers are planning new attempts at alien communication. One is using a giant new radio telescope, and the other is choosing a compelling new target.</p>
<p>One of these new messages will be sent from the <a href="https://fast.bao.ac.cn/">world’s largest radio telescope</a>, in China, sometime in 2023. The telescope, with a 1,640-foot (500-meter) diameter, will beam a series of radio pulses over a broad swath of sky. These on-off pulses are like the 1s and 0s of digital information. </p>
<p>The message is called “<a href="https://arxiv.org/abs/2203.04288">The Beacon in the Galaxy</a>” and includes prime numbers and mathematical operators, the biochemistry of life, human forms, the Earth’s location and a time stamp. The team is sending the message toward a group of millions of stars near the center of the Milky Way galaxy, about 10,000 to 20,000 light-years from Earth. While this maximizes the pool of potential aliens, it means it will be tens of thousands of years before Earth may get a reply.</p>
<p>The other attempt is targeting only a single star, but with the potential for a much quicker reply. On Oct. 4, 2022, a team from the Goonhilly Satellite Earth Station in England will beam a message toward the star <a href="https://www.newscientist.com/article/2315676-group-that-wants-to-contact-aliens-will-transmit-to-trappist-1-system/">TRAPPIST-1</a>. This star has seven planets, three of which <a href="https://theconversation.com/ultracool-dwarf-star-hosts-three-potentially-habitable-earth-sized-planets-just-40-light-years-away-58695">are Earth-like worlds in the so-called “Goldilocks zone</a>” – meaning they could be home to liquid and potentially life, too. TRAPPIST-1 is just 39 light-years away, so it could take as few as 78 years for intelligent life to receive the message and Earth to get the reply.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of a dense, bulbous, gas- and star-filled region of space." src="https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/460136/original/file-20220427-16-5v9rcq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The center of the Milky Way galaxy may be home to intelligent life, but some researchers think contacting aliens is a bad idea.</span>
<span class="attribution"><a class="source" href="http://photojournal.jpl.nasa.gov/catalog/PIA12348">NASA/JPL-Caltech/ESA/CXC/STScI</a></span>
</figcaption>
</figure>
<h2>Ethical questions</h2>
<p>The prospect of alien contact is ripe with ethical questions, and METI is no exception.</p>
<p>The first is: <a href="https://setiathome.berkeley.edu/meti_statement_0.html">Who speaks for Earth</a>? In the absence of any international consultation with the public, decisions about what message to send and where to send it are in the hands of a <a href="https://www.newyorker.com/books/joshua-rothman/the-man-who-speaks-for-earth">small group of interested scientists</a>. </p>
<p>But there is also a much deeper question. If you are lost in the woods, getting found is obviously a good thing. When it comes to whether humanity should be broadcasting a message to aliens, the answer is much less clear-cut.</p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://memberservices.theconversation.com/newsletters/?nl=science&source=inline-science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p>
<p>Before he died, iconic physicist <a href="https://www.space.com/34184-stephen-hawking-afraid-alien-civilizations.html">Stephen Hawking was outspoken about the danger</a> of contacting aliens with superior technology. He argued that they could be malign and if given Earth’s location, might destroy humanity. <a href="https://www.ibtimes.co.uk/meti-president-doug-vakoch-aliens-are-not-dangerous-we-could-make-contact-by-2035-1543965">Others see no extra risk</a>, since a truly advanced civilization would already know of our existence. And there is interest. Russian-Israeli billionaire Yuri Milner <a href="https://www.nbcnews.com/storyline/the-big-questions/why-these-scientists-fear-contact-space-aliens-n717271">has offered $1 million</a> for the best design of a new message and an effective way to transmit it. </p>
<p>To date, no international regulations govern METI, so the experiments will continue, despite concerns. </p>
<p>For now, intelligent aliens remain in the realm of science fiction. Books like “<a href="https://www.npr.org/2014/11/13/363123510/three-body-problem-asks-a-classic-sci-fi-question-in-chinese">The Three-Body Problem</a>” by Cixin Liu offer somber and thought-provoking perspectives on what the success of METI efforts might look like. It doesn’t end well for humanity in the books. If humans ever do make contact in real life, I hope the aliens come in peace.</p>
<p><em>This story has been updated to clarify where the Pioneer and Voyager spacecraft are in relation to the Solar System.</em></p><img src="https://counter.theconversation.com/content/182036/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation.</span></em></p>This year, two groups of astronomers plan to send messages containing information about humans and the location of Earth toward parts of space they think may be home to intelligent life.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1705482021-10-25T19:12:23Z2021-10-25T19:12:23ZA mysterious signal looked like a sign of alien technology — but it turned out to be radio interference<figure><img src="https://images.theconversation.com/files/428186/original/file-20211025-25-mb1aem.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2048%2C1367&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span></figcaption></figure><p>In December last year, the media reported <a href="https://www.theguardian.com/science/2020/dec/18/scientists-looking-for-aliens-investigate-radio-beam-from-nearby-star">an intriguing signal</a> we at the <a href="https://breakthroughinitiatives.org/initiative/1">Breakthrough Listen</a> project found in our radio telescope data. Dubbed BLC1, the signal didn’t appear to be the result of any recognisable astrophysical activity or any familiar Earth-based interference.</p>
<p>The trouble was, we weren’t ready to discuss it. When you’re searching for signs of extraterrestrial life, you want to be very careful about getting it right before you make any announcements. Last year we had only just started secondary verification tests, and there were too many unanswered questions. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/we-asked-astronomers-are-we-alone-in-the-universe-the-answer-was-surprisingly-consistent-132088">We asked astronomers: are we alone in the Universe? The answer was surprisingly consistent</a>
</strong>
</em>
</p>
<hr>
<p>Today we are ready to report that BLC1 is, sadly, not a signal from intelligent life beyond Earth. Rather, it is radio interference that closely mimics the type of signal we’ve been looking for. Our results are reported in <a href="https://www.nature.com/articles/s41550-021-01479-w">two</a> <a href="https://www.nature.com/articles/s41550-021-01508-8">papers</a> in Nature Astronomy.</p>
<h2>Searching for solar flares and signs of life</h2>
<p>The story of BLC1 starts in April 2019, when Andrew Zic, who at the time was a PhD student at the University of Sydney, began observing the nearby star Proxima Centauri with multiple telescopes to search for flare activity. At 4.22 light years away, Proxima Centauri is our nearest stellar neighbour, but it is too faint to see with the naked eye. </p>
<p>Flares from stars are bursts of energy and hot plasma that may impact (and likely destroy) the atmosphere of any planets in their path. Though the Sun produces flares, they are not strong or frequent enough to disrupt life on Earth. Understanding how and when a star flares teaches us a lot about whether those planets might be suitable for life. </p>
<p>Proxima Centauri hosts an Earth-sized exoplanet called Proxima Centauri b, and Andrew’s observations suggested the planet is <a href="https://theconversation.com/bad-space-weather-may-make-life-impossible-near-proxima-centauri-150979">buffeted by fierce “space weather”</a>. While bad space weather doesn’t rule out life existing in the Proxima Centauri system, it does mean the planet’s surface is likely to be inhospitable. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/bad-space-weather-may-make-life-impossible-near-proxima-centauri-150979">Bad space weather may make life impossible near Proxima Centauri</a>
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<p>Still, as our nearest neighbour, Proxima Centauri b remains a compelling target for the search for extraterrestrial intelligence (or SETI). Proxima Centauri is one of the only stars we could potentially ever visit in our lifetime. </p>
<p>At the speed of light, a two-way trip would take 8.4 years. We can’t send a spaceship that fast, but there is hope that <a href="https://theconversation.com/observing-the-universe-with-a-camera-traveling-near-the-speed-of-light-93994">a tiny camera on a light sail</a> could reach there in 50 years and beam back pictures. </p>
<p>Because of this, we joined forces with Andrew Zic and his collaborators, and used <a href="https://www.csiro.au/en/about/facilities-collections/atnf/parkes-radio-telescope">CSIRO’s Parkes telescope</a> (also known as Murriyang in the Wiradjuri language) to run SETI observations in parallel with the flare activity search. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/observing-the-universe-with-a-camera-traveling-near-the-speed-of-light-93994">Observing the universe with a camera traveling near the speed of light</a>
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<h2>An intriguing summer project</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=756&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=756&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=756&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=949&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=949&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428190/original/file-20211025-23-1q8jliz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=949&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The BLC1 signal. Each panel in the plot is an observation toward Proxima Centauri (‘on source’), or toward a reference source (‘off source’). BLC1 is the yellow drifting line, and is only present when the telescope is pointed at Proxima Centauri.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41550-021-01479-w">Smith et al., Nature Astronomy</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We thought searching these observations would be an excellent project for a summer student. In 2020, Shane Smith, an undergraduate student from Hillsdale College in Michigan, United States, joined the Berkeley SETI Research Experience for Undergraduates <a href="https://seti.berkeley.edu/Internship.html">program</a> and began sifting through the data. Toward the end of his project, BLC1 popped out.</p>
<p>The Breakthrough Listen team quickly became intrigued by BLC1. However, the burden of proof to claim a detection of life beyond Earth is exceedingly high, so we don’t let ourselves get too excited until we’ve applied every test we can think of. The analysis of BLC1 was spearheaded by Sofia Sheikh, at the time a PhD student at Penn State, who ran an exhaustive set of tests, many of which were new.</p>
<p>There was plenty of evidence pointing toward BLC1 being a genuine sign of extraterrestrial technology (or “technosignature”). BLC1 has many characteristics we expect from a technosignature:</p>
<ul>
<li><p>we only saw BLC1 when we were looking toward Proxima Centauri, and didn’t see it in when we looked elsewhere (in “off-source” observations). Interfering signals are commonly seen in all directions, as they “leak” into the telescope receiver</p></li>
<li><p>the signal only occupies one narrow band of frequencies, whereas signals from stars or other astrophysical sources occur over a much wider range </p></li>
<li><p>the signal slowly drifted in frequency over a 5-hour period. A frequency drift is expected for any transmitter not fixed to Earth’s surface, as its movement relative to us will cause a Doppler effect</p></li>
<li><p>the BLC1 signal persisted for several hours, making it unlike other interference from artificial satellites or aircraft that we have observed before.</p></li>
</ul>
<p>Nevertheless, Sofia’s analysis led us to conclude BLC1 is most likely radio interference from right here on Earth. Sofia was able to show this by searching across the entire frequency range of the Parkes receiver and finding “lookalike” signals, whose characteristics are mathematically related to BLC1. </p>
<p>Unlike BLC1, the lookalikes <em>do</em> appear in off-source observations. As such, BLC1 is guilty by association of being radio interference. </p>
<h2>Not the technosignature we were looking for</h2>
<p>We don’t know exactly where BLC1 was coming from, or why it wasn’t detected in off-source observations like the lookalike signals. Our best guess is that BLC1 and the lookalikes are generated by a process called <em>intermodulation</em>, where two frequencies mix together to create new interference. </p>
<p>If you’ve listened to blues or rock guitar, you are probably familiar with intermodulation. When a guitar amp is deliberately overdriven (when you turn it up to 11), intermodulation adds a pleasant-sounding distortion to the clean guitar signal. So BLC1 is – perhaps – just an unpleasant distortion from a device with an overdriven radio frequency amplifier.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/seti-why-extraterrestrial-intelligence-is-more-likely-to-be-artificial-than-biological-169966">Seti: why extraterrestrial intelligence is more likely to be artificial than biological</a>
</strong>
</em>
</p>
<hr>
<p>Regardless of what caused BLC1, it was not the technosignature we were looking for. It did, however, make for an excellent case study, and showed that our detection pipelines are working and picking up unusual signals. </p>
<p>Proxima Centauri is only one of many hundreds of billions of stars in the Milky Way. To search them all, we need to keep our momentum, to continue to improve our tools and verification tests, and to train the next generation of astronomers, like Shane and Sofia, who can continue the search with the next generation of telescopes.</p><img src="https://counter.theconversation.com/content/170548/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>In previous roles, Danny C Price has received funding from Breakthrough Listen. </span></em></p>Astronomers hunting extraterrestrials were excited to discover an intriguing signal, but closer inspection has revealed it wasn’t aliens.Danny C Price, Senior research fellow, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1699662021-10-18T14:27:21Z2021-10-18T14:27:21ZSeti: why extraterrestrial intelligence is more likely to be artificial than biological<figure><img src="https://images.theconversation.com/files/426669/original/file-20211015-21-tuqae2.jpg?ixlib=rb-1.1.0&rect=21%2C71%2C4779%2C3541&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Are we listening in vain?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/radio-telescope-view-night-milky-way-250870294">sdecoret/Shutterstock</a></span></figcaption></figure><p>Is there intelligent life elsewhere in the universe? It’s a question that has been debated for centuries, <a href="https://blogs.scientificamerican.com/life-unbounded/the-first-alien/">if not millenia</a>. But it is only recently that we’ve had an actual chance of finding out, with initiatives such as <a href="https://www.seti.org">Seti</a> (Search for Extraterrestrial Intelligence) using radio telescopes to actively listen for radio messages from alien civilisations. </p>
<p>What should we expect to detect if these searches succeed? My suspicion is that it is very unlikely to be little green men – something I speculated about at a talk at a <a href="https://seti.berkeley.edu/listen/">Breakthrough Listen</a> (a Seti project) conference.</p>
<p>Suppose there are other planets where life began and that it followed something like a Darwinian evolution (which needen’t be the case). Even then, it’s highly unlikely that the progression of intelligence and technology would happen at exactly the same pace as on Earth. If it lagged significantly behind, then that planet would plainly reveal no evidence of extraterrestrial life to our radio telescopes. But around a star older than the Sun, life could have had a head start of a billion years or more. </p>
<p>Human technological civilisation only dates back millennia (at most) – and it may be only one or two more centuries before humans, made up of organic materials such as carbon, <a href="https://www.theguardian.com/technology/2019/mar/28/can-we-stop-robots-outsmarting-humanity-artificial-intelligence-singularity">are overtaken or transcended by</a> inorganic intelligence, such as AI. Computer processing power is already increasing exponentially, meaning AI in the future may be able to use vastly more data than it does today. It seems to follow that it could then get exponentially smarter, surpassing human general intelligence. </p>
<p>Perhaps a starting point would be to enhance ourselves with genetic modification in combination with technology – creating cyborgs with partly organic and partly inorganic parts. This could be a transition to fully artificial intelligences.</p>
<p>AI may even be able to evolve, creating better and better versions of itself on a faster-than-Darwinian timescale for billions of years. Organic human-level intelligence would then be just a brief interlude in our “human history” before the machines take over. So if alien intelligence had evolved similarly, we’d be most unlikely to “catch” it in the brief sliver of time when it was still embodied in biological form. If we were to detect extraterrestrial life, it would be far more likely to be electronic than flesh and blood – and it may not even reside on planets.</p>
<p>We must therefore reinterpret <a href="https://theconversation.com/where-is-everybody-doing-the-maths-on-extraterrestrial-life-3390">the Drake equation,</a> which was established in 1960 to estimate the number of civilisations in the Milky Way with which we could potentially communicate. The equation includes various assumptions, such as how many planets there are, but also how long a civilisation is able to release signals into space, estimated to be between 1,000 and 100 million years.</p>
<p>But the lifetime of an organic civilisation may be millennia at most, while its electronic diaspora could continue for billions of years. If we include this in the equation, it seems there may be more civilisations out there than we thought, but that the majority of them would be artificial.</p>
<p>We may even want to rethink the term “alien civilisations”. A “civilisation” connotes a society of individuals. In contrast, extraterrestrials might be a single integrated intelligence.</p>
<h2>Decoding messages</h2>
<p>If Seti succeeded, it would therefore be unlikely to record decodable messages. Instead, it may spot a byproduct (or even a malfunction) of some super complex machine far beyond our comprehension. </p>
<p>Seti focuses on the radio part of the electromagnetic spectrum. But as we have no idea of what’s out there, we should clearly explore all wavebands, including the optical and X-ray parts. Rather than just listening for radio transmission, we should also be alert to other evidence of non-natural phenomena or activity. These include <a href="https://www.space.com/dyson-sphere.html">artificial structures built around stars</a> to absorb their energy (Dyson spheres) or artificially created molecules, such as <a href="https://gml.noaa.gov/hats/publictn/elkins/cfcs.html">chlorofluorocarbons</a> – nontoxic, nonflammable chemicals containing carbon, chlorine, and fluorine – in planet atmospheres. These chemicals are greenhouse gasses that can’t be created by natural processes, meaning they could be a sign of “<a href="https://theconversation.com/a-layer-of-aerogel-could-make-mars-habitable-and-even-enable-life-to-develop-there-but-heres-why-we-should-wait-120330">terraforming</a>” (changing a planet to make it more habitable) or industrial pollution. </p>
<figure class="align-center ">
<img alt="Artist's impression of a Dyson sphere." src="https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/426881/original/file-20211018-80042-1f7sdg3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Advanced extraterrestrials could build Dyson spheres.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/futuristic-scifi-city-on-ring-planet-1928570306">Eduard Muzhevskyi/Shutterstock</a></span>
</figcaption>
</figure>
<p>I’d argue it would even be worth looking for traces of aliens in our own solar system. While we can probably rule out visits by human-like species, there are other possibilities. An extraterrestrial civilisation that had mastered nanotechnology may have transferred its intelligence to tiny machines, for example. It could then invade other worlds, or even asteroid belts, with swarms of microscopic probes.</p>
<p>And even if we did receive a decodable radio message, how could we know what the intention of the super-intelligent sender would be? We have absolutely zero idea – think of the variety of bizarre motives (ideological, financial and religious) that have driven human endeavours in the past. They may be peaceful and inquisitive. Even less obtrusively, they may realise that it’s easier to think at low temperatures – getting far away from any star, or even hibernating for billions of years until it’s cooler. But they could be expansionist – and this seems the expectation of most who’ve thought about the future trajectory of civilisations.</p>
<h2>The future of intelligence</h2>
<p>As the universe evolves, intelligent species may get unfathomably clever.
Just take our own future. Eventually, stellar births and deaths in our galaxy will proceed gradually more slowly, until it gets jolted as the <a href="https://www.skyatnightmagazine.com/space-science/andromeda-milky-way-galaxy-collision/">Milky Way crashes with the Andromeda galaxy </a> in about billion years. The debris of our galaxy, Andromeda and their smaller companions within our local group of galaxies will thereafter clump together into one amorphous galaxy, while distant ones move away from us and eventually disappear. </p>
<p>But our remnant will continue for far longer – time enough, perhaps, for a civilisation to emerge that could be in possession of huge amounts of energy, even harnessing the entire mass of a galaxy.</p>
<p>This may be the culmination of the long-term trend for living systems to gain complexity. At this stage, all the atoms that were once in stars and gas could be transformed into a giant organism of galactic scale. Some science fiction authors envisage stellar-scale engineering to create black holes and <a href="https://theconversation.com/wormholes-may-be-lurking-in-the-universe-and-new-studies-are-proposing-ways-of-finding-them-153020">wormholes</a> – bridges connecting different points in spacetime, in theory providing shortcuts for space travellers. These
concepts are far beyond any technological capability that we can envisage, but not in violation of basic physical laws. </p>
<h2>Are we artificial?</h2>
<p>Post-human intelligences may also be able to build computers with enormous processing power. Humans are already able to model some quite complex phenomenon, such as the climate. More intelligent civilisations, however, may be able to simulate living things – with actual consciousnesses – or even entire worlds or universes.</p>
<figure class="align-center ">
<img alt="Image of a binary code background of matrix green." src="https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/426882/original/file-20211018-32522-1w0gnk4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=427&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Are we just characters in an alien computer game?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/binary-code-background-abstract-matrix-green-722889532">Mertsaloff/Shutterstock</a></span>
</figcaption>
</figure>
<p>How do we know that we aren’t <a href="https://theconversation.com/elon-musk-says-were-probably-living-in-a-computer-simulation-heres-the-science-60821">living in such a simulation</a> created by technologically superior aliens? Maybe we are no more than a bit of entertainment for some supreme being who is running such a model? Indeed, if life is destined to be able to create technologically advanced civilisations that can make computer programs, there may be more simulated universes our there than real ones out there – making it conceivable that we are in one of them. </p>
<p>This conjecture may sound outlandish, but it is all based on our current understanding of physics and cosmology. We should, however, surely be open-minded about the possibility that there’s much we don’t understand. Perhaps the laws we see and the constants we measure are only “local” and differ in other parts of the universe? That would lead to even more jaw-dropping possibilities. </p>
<p>Ultimately, physical reality could encompass complexities that neither our intellect nor our senses can grasp. Some electronic “brains” may simply have a quite different perception of reality. Nor can we predict or understand their motives. That’s why we can’t assess whether the current radio silence that Seti are experiencing signifies the absence of advanced alien civilisations, or simply their preference.</p>
<p><em>*This article is partly adapted from a speech given by the author at a Breakthrough Listen conference in 2018</em></p><img src="https://counter.theconversation.com/content/169966/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Rees does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Organic human-level intelligence may be just a brief interlude in human history before the machines take over.Martin Rees, Emeritus Professor of Cosmology and Astrophysics, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1652372021-07-29T05:02:20Z2021-07-29T05:02:20ZIs the truth out there? How the Harvard-based Galileo Project will search the skies for alien technology<figure><img src="https://images.theconversation.com/files/413552/original/file-20210728-17-2hy3t4.jpeg?ixlib=rb-1.1.0&rect=9%2C0%2C1268%2C751&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">ESO</span></span></figcaption></figure><p>Can we find alien technology? That is the ambitious goal of the <a href="https://projects.iq.harvard.edu/galileo">Galileo Project</a>, launched this week by Harvard astrophysicist Avi Loeb with substantial private financial backing. </p>
<p>The project is far from the first attempt to detect signs of civilisations beyond Earth. Loeb has been criticised in the past for his <a href="https://www.forbes.com/sites/startswithabang/2021/02/16/watch-harvard-astronomer-mansplains-seti-to-the-legend-who-inspired-carl-sagans-contact/?sh=ac97ad1620b8">dismissive approach</a> to previous efforts to find extraterrestrial life and his <a href="https://lrb.co.uk/the-paper/v43/n11/chris-lintott/flying-pancakes-from-space">argument</a> that an alien artefact passed through our solar system in 2017. </p>
<p>So why do Loeb and his collaborators think they have a chance of finding something where others have failed? There are three triggers that suggest they might.</p>
<h2>Exoplanets, ‘Oumuamua, and UFOs</h2>
<p>First, years of painstaking observations have shown that <a href="https://theconversation.com/nasas-planet-hunting-spacecraft-tess-is-now-on-its-mission-to-search-for-new-worlds-94291">many stars</a> host Earth-like planets. There is a real chance these “exoplanets” might be home to alien civilisations.</p>
<p>Second, five years ago, an interstellar visitor, dubbed 'Oumuamua, tumbled though our solar system. It was a skinny object about 400 metres long, and we know from its speed and trajectory that it arrived from outside our solar system. It was the first time we had ever seen an interstellar object enter our neighbourhood. </p>
<p>Unfortunately it caught us on the hop, and we didn’t notice it until it was on its way out. So we didn’t get a chance to have a really good look at it.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/no-sign-of-alien-life-so-far-on-the-mystery-visitor-from-space-but-were-still-looking-89223">No sign of alien life 'so far' on the mystery visitor from space, but we're still looking</a>
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<p>Scientists were divided on the question of what 'Oumuamua might be. Many thought it was simply an interstellar shard of rock, even though we had no idea how such a shard might be produced or slung our way. </p>
<p>Others, including Loeb, thought there was a chance it was a spacecraft from another civilisation. Some scientists felt such claims to be far-fetched. Others pointed out that science should be open-minded and, in the absence of a good explanation, we should examine all plausible solutions. </p>
<p>Today, the question is still hanging. We don’t know whether 'Oumuamua was a spaceship or merely an inert lump of rock.</p>
<p>The third trigger for the Galileo Project came from the US military. In June, the Office of the US Director of National Intelligence <a href="https://www.dni.gov/files/ODNI/documents/assessments/Prelimary-Assessment-UAP-20210625.pdf">announced</a> that some military <a href="https://theconversation.com/from-flying-boats-to-secret-soviet-weapons-to-alien-visitors-a-brief-cultural-history-of-ufos-164128">reports of UFOs</a>, or UAPs (Unidentified Aerial Phenomena) as they are now known, seem real. </p>
<p>Specifically, the report said some UAPs “probably do represent physical objects given that a majority of UAP were registered across multiple sensors” and there was no known explanation for them. </p>
<p>In other words, they aren’t meteorological phenomena, or faulty instruments, or weather balloons, or clandestine military experiments. So what are they? </p>
<p>Again, the question is left hanging. The report seems to rule out known technology, and suggests “advanced technology”, but stops short of suggesting it is the work of aliens. </p>
<h2>Science to the rescue</h2>
<p>Loeb takes the view that instead of debating whether either 'Oumuamua or UAPs provide evidence of alien intelligence, we should do what scientists are good at: get some reliable data. And, he argues, scientists are the people to do it, not politicians or military staff. As the US report says, the sensors used by the military “are not generally suited for identifying UAP”.</p>
<p>Few subjects divide scientists as much as the existence of aliens. On one hand, there are serious SETI (Search for Extra-terrestrial Intelligence) projects, such as <a href="https://www.seti.org/seti-institute/project/details/project-phoenix">Project Phoenix</a> and <a href="https://theconversation.com/curious-kids-what-has-the-search-for-extraterrestrial-life-actually-yielded-and-how-does-it-work-122454">Breakthrough Listen</a>, that use the world’s largest telescopes to search for signals from some extraterrestrial intelligence. </p>
<p>At the other extreme, few scientists are persuaded by the fuzzy photos and dubious eyewitness accounts that seem to <a href="https://theconversation.com/ufos-climate-change-and-missing-airliners-how-to-separate-fact-from-fiction-59587">characterise many UFO reports</a>.</p>
<p>The Galileo Project is very different from SETI searches or collections of UFO sightings. Instead, it will explicitly search for evidence of alien artefacts, either in space or on Earth. </p>
<h2>But is it science?</h2>
<p>Is this science? Loeb is convinced that it is. He argues the Galileo Project will bring scientific techniques and expertise to bear on one of the most important questions we can ask: are we alone? And the project will build purpose-designed equipment, optimised for the detection of alien artefacts. </p>
<p>Will it find anything? The odds are poor, as Loeb admits. In essence it’s a fishing expedition. But if there is a prima facie case for the existence of alien technology, then science has a duty to investigate it.</p>
<p>But suppose they do find something? Will we get to hear about it, or will it be locked up in some future <a href="https://theconversation.com/internet-jokesters-call-for-people-to-storm-area-51-to-find-aliens-heres-some-science-to-consider-120715">Area 51</a>? </p>
<p>The Galileo Project has promised all data will be made public, and all results will be published in peer-reviewed journals. Indeed, one of the reasons it will not use existing military data is because much of it is classified, which would restrict the project’s freedom to make the results public.</p>
<p>Or perhaps the project will find natural explanations for 'Oumuamua and UAPs. But even that will be a new scientific discovery, perhaps revealing new natural phenomena. </p>
<p>As Loeb <a href="https://www.youtube.com/watch?v=Q3NqRak2tjc">says</a>:</p>
<blockquote>
<p>Whenever we look at the sky in a new way, we find something new. We will find something exciting no matter what. </p>
</blockquote>
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Read more:
<a href="https://theconversation.com/wtf-newly-discovered-ghostly-circles-in-the-sky-cant-be-explained-by-current-theories-and-astronomers-are-excited-142812">'WTF?': newly discovered ghostly circles in the sky can't be explained by current theories, and astronomers are excited</a>
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<img src="https://counter.theconversation.com/content/165237/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ray Norris does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Can the Galileo Project find alien technology?Ray Norris, Professor, School of Science, Western Sydney UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1630592021-06-30T12:14:27Z2021-06-30T12:14:27ZUS intelligence report on UFOs: No aliens, but government transparency and desire for better data might bring science to the UFO world<figure><img src="https://images.theconversation.com/files/408956/original/file-20210629-23-49zsqh.png?ixlib=rb-1.1.0&rect=66%2C35%2C602%2C596&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The new government report describes 144 sightings of unidentified aerial phenomena.</span> <span class="attribution"><a class="source" href="https://www.navair.navy.mil/foia/documents">U.S. Navy</a></span></figcaption></figure><p>On June 25, 2021, the Office of the Director of National Intelligence released a much-anticipated <a href="https://www.dni.gov/files/ODNI/documents/assessments/Prelimary-Assessment-UAP-20210625.pdf">report on UFOs to Congress</a>. The military has rebranded unidentified flying objects as unidentified aerial phenomena – UAPs – in part to avoid the stigma that has been attached to claims of aliens visiting the Earth since the <a href="https://www.livescience.com/roswell-ufo-crash-what-really-happened.html">Roswell incident in 1947</a>. The report presents no convincing evidence that alien spacecraft have been spotted, but some of the data defy easy interpretation. </p>
<p>I’m a <a href="https://www.as.arizona.edu/people/faculty/chris-impey">professor of astronomy</a> who has written extensively on the <a href="https://www.cambridge.org/core/books/talking-about-life/696F47F802931AE9021CA72083313579">search for life</a> in the universe. I also teach a <a href="https://www.coursera.org/learn/astrobiology-exploring-other-worlds">free online class on astrobiology</a>. I do not believe that the new government report or any other sightings of UFOs in the past are proof of aliens visiting Earth. But the report is important because it opens the door for a serious look at UFOs. Specifically, it encourages the U.S. government to collect better data on UFOs, and I think the release of the report increases the chances that scientists will try to interpret that data. Historically, UFOs have felt off limits to mainstream science, but perhaps no more.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/rO_M0hLlJ-Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Three videos from the U.S. military sparked a recent surge in interest in UFOs.</span></figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/us-government-ufo-report-from-shrouded-history-to-a-data-driven-future-podcast-163675">US government UFO report: from shrouded history to a data–driven future – podcast</a>
</strong>
</em>
</p>
<hr>
<h2>What’s in the UFO report?</h2>
<p>The No. 1 thing the report focuses on is the lack of high-quality data. Here are the highlights from the <a href="https://www.dni.gov/files/ODNI/documents/assessments/Prelimary-Assessment-UAP-20210625.pdf">slender nine-page report</a>, covering a total of 144 UAP sightings from U.S. government sources between 2004 and 2021:</p>
<ul>
<li><p>“Limited data and inconsistent reporting are key challenges to evaluating UAP.” </p></li>
<li><p>Some observations “could be the result of sensor errors, spoofing, or observer misperception.”</p></li>
<li><p>“UAP clearly pose a safety of flight issue and may pose a challenge to U.S. national security.”</p></li>
<li><p>Of the 144 sightings, the task force was “able to identify one reported UAP with high confidence. In that case, we identified the object as a large, deflating balloon. The others remain unexplained.”</p></li>
<li><p>“Some UAP many be technologies deployed by China, Russia, another nation, or non-governmental entity.”</p></li>
</ul>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The front page of the report with a U.S. government logo and 'unclassified' listed at the top." src="https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=522&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=522&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=522&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=656&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=656&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408950/original/file-20210629-11592-6d5ji7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=656&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Office of the Director of National Intelligence prepared the report for the Congressional Intelligence and Armed Services Committees.</span>
<span class="attribution"><a class="source" href="https://www.dni.gov/files/ODNI/documents/assessments/Prelimary-Assessment-UAP-20210625.pdf">Office of the Director of National Intelligence</a></span>
</figcaption>
</figure>
<h2>UFOs are taboo among scientists</h2>
<p>UFO means unidentified flying object. Nothing more, nothing less. You’d think scientists would enjoy the challenge of solving this puzzle. Instead, UFOs have been taboo for academic scientists to investigate, and so unexplained reports have not received the scrutiny they deserve.</p>
<p>One reason is that most scientists think there is <a href="http://www.fraknoi.com/wp-content/uploads/2021/05/Responding-to-Claims-about-Alien-UFOs-2.pdf">less to most reports than meets the eye</a>, and the few who have dug deeply have mostly <a href="https://doi.org/10.2307/j.ctt2005r2h">debunked the phenomenon</a>. <a href="http://www.ianridpath.com/ufo/astroufo1.htm">Over half of sightings can be attributed</a> to meteors, fireballs and the planet Venus. </p>
<p>Another reason for the scientific hesitance is that UFOs have been co-opted by popular culture. They are part of a landscape of conspiracy theories that includes accounts of <a href="https://doi.org/10.1080/01463370600878545">abduction by aliens</a> and <a href="https://www.smithsonianmag.com/arts-culture/crop-circles-the-art-of-the-hoax-2524283/">crop circles</a>. Scientists worry about their professional reputations, and the association of UFOs with these supernatural stories causes most researchers to avoid the topic.</p>
<p>But some scientists have looked. In 1968, Edward U. Condon at the University of Colorado published the <a href="https://files.ncas.org/condon/">first major academic study of UFO sightings</a>. The Condon Report put a damper on further research when it found that “<a href="https://www.jstor.org/stable/1725090">nothing has come from the study of UFOs in the past 21 years</a> that has added to scientific knowledge.”</p>
<p>However, a <a href="https://news.stanford.edu/pr/98/980629ufostudy.html">review in 1998</a> by a panel led by Peter Sturrock, a professor of applied physics at Stanford University, concluded that some sightings are accompanied by physical evidence that deserves scientific study. Sturrock also <a href="https://www.scientificexploration.org/docs/8/jse_08_2_sturrock.pdf">surveyed professional astronomers</a> and found that nearly half thought UFOs were worthy of scientific study, with higher interest among younger and more well-informed astronomers.</p>
<p>If astronomers are intrigued by UFOs – and believe some cases deserve study with academic rigor – what’s holding them back? A <a href="https://doi.org/10.1177/0963662515617706">history of mistrust</a> between ufologists and scientists hasn’t helped. And while UFO research has employed <a href="https://doi.org/10.1023/B:QUAS.0000015542.28438.41">some of the tools of the scientific method</a>, it has not had the core of skeptical, evidence-based reasoning that demarcates science from <a href="https://www.scientificamerican.com/article/what-is-pseudoscience/">pseudoscience</a>.</p>
<p>A search of 90,000 recent and current <a href="https://www.nsf.gov/awardsearch/">grants awarded</a> by the National Science Foundation finds none addressing UFOs or related phenomena. I’ve served on review panels for 35 years, and can imagine the reaction if such a proposal came up for peer review: raised eyebrows and a quick vote not to fund.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A group of satellite dishes pointing in various directions." src="https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408955/original/file-20210629-28-ro64v4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Radio telescopes like the Allen Telescope Array seen here scan the sky looking for signs of intelligent life in the universe.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Allen_Telescope_Array_-_Flickr_-_brewbooks_(11).jpg#/media/File:Allen_Telescope_Array_-_Flickr_-_brewbooks_(11).jpg">Brewbooks/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>A decadeslong search for aliens</h2>
<p>While the scientific community has almost entirely avoided engaging with UFOs, a much more mainstream search for intelligent aliens and their technology has been going on for decades.</p>
<p>The search is motivated by the fact that astronomers have, to date, discovered <a href="https://exoplanetarchive.ipac.caltech.edu/">over 4,400 planets orbiting other stars</a>. Called exoplanets, some are close to the Earth’s mass and at just the right distance from their stars to potentially have water on their surfaces – meaning they might be habitable.</p>
<p>Astronomers estimate that there are <a href="https://www.cnn.com/2020/11/05/world/nasa-300-million-habitable-planets-intl-hnk-scli-scn/index.html">300 million habitable worlds</a> in the Milky Way galaxy alone, and each one is a <a href="https://www.seti.org/drake-equation-index">potential opportunity</a> for life to develop and for intelligence and technology to emerge. Indeed, most astronomers think it very unlikely that <a href="https://exoplanets.nasa.gov/news/1350/are-we-alone-in-the-universe-revisiting-the-drake-equation/">humans are the only or the first advanced civilization</a>. </p>
<p>This confidence has fueled an active <a href="https://www.seti.org/">search for extraterrestrial intelligence</a>, known as SETI. It has been unsuccessful so far. As a result, researchers have recast the question “Are we alone?” to “Where are the aliens?” The absence of evidence for intelligent aliens is called the <a href="https://www.seti.org/fermi-paradox-0">Fermi paradox</a>. First articulated by the physicist Enrico Fermi, it’s a paradox because advanced civilizations should be spread throughout the galaxy, yet we see no sign of their existence. </p>
<p>The SETI activity has not been immune from scientists’ <a href="https://doi.org/10.1038/461316a">criticism</a>. It was starved of federal funding for decades and recently has gotten most of its support from <a href="https://www.sciencemag.org/news/2020/09/how-big-money-powering-massive-hunt-alien-intelligence">private sources</a>. However, in 2020, NASA <a href="https://www.usatoday.com/story/news/nation/2020/06/20/nasa-funds-research-alien-technological-civilizations/3224063001/">resumed funding for SETI</a>, and the new NASA administrator wants researchers to <a href="https://www.cnn.com/2021/06/04/tech/ufos-nasa-study-scn/index.html">pursue the topic of UFOs</a>. </p>
<p>In this context, the intelligence report is welcome. The report draws <a href="https://apnews.com/article/technology-government-and-politics-f5f24502d97072fd4bef34b6fe36c81d">few concrete conclusions</a> about UFOs and avoids any reference to aliens or extraterrestrial spacecraft. However, it notes the importance of destigmatizing UFOs so that more pilots report what they see. It also sets a goal of moving from anecdotal observations to standardized and scientific data collection. Time will tell if this is enough to draw scientists into the effort, but the transparency to publish the report at all reverses a long history of <a href="https://www.nytimes.com/2017/12/16/us/politics/pentagon-program-ufo-harry-reid.html">secrecy surrounding U.S. government reports on UFOs</a>.</p>
<p>I don’t see any convincing evidence of alien spacecraft, but as a curious scientist, I hope the subset of UFO sightings that are truly unexplained gets closer study. Scientists are unlikely to weigh in if their skepticism generates attacks from “true believers” or they get ostracized by their colleagues. Meanwhile, the truth is still out there.</p>
<p><em>This article has been updated to clarify that the report was produced by the Office of the Director of National Intelligence.</em></p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/163059/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation. </span></em></p>A new nine-page report, requested by Congress, doesn’t say what the 144 UFO sightings from 2004 to 2021 are, but does say that the government wants to learn more.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1613662021-05-21T11:34:29Z2021-05-21T11:34:29ZMushrooms on Mars? Five unproven claims that alien life exists<figure><img src="https://images.theconversation.com/files/402108/original/file-20210521-13-11jz09l.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C746%2C511&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mushroom-like structures on Mars.</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>A <a href="https://www.researchgate.net/publication/351252619_Fungi_on_Mars_Evidence_of_Growth_and_Behavior_From_Sequential_Images">recent study</a> claims to have found evidence for mushroom-like life forms on the surface of Mars. As it happens, these particular features are well known and were discovered by cameras aboard Nasa’s Mars Exploration Rover <a href="https://www.jpl.nasa.gov/missions/mars-exploration-rover-opportunity-mer">Opportunity</a>, shortly after it landed in 2004. </p>
<p>They are not, in fact, living organisms at all, but “haematite concretions” – small sphere-shaped pieces of the mineral <a href="https://www.tandfonline.com/doi/pdf/10.1071/PVv2017n191p43">haematite</a>, and their exact origin is still debated by scientists. Haematite is a compound of iron and oxygen and is <a href="https://geology.com/minerals/hematite.shtml">commercially important on Earth</a>. The spherical rocks on Mars may have been created by the gradual accumulation of the material in slowly evaporating liquid water environments. They could also have been produced by <a href="https://www.sciencedirect.com/science/article/abs/pii/S0012821X05006382">volcanic activity</a>. </p>
<p>Either way, mushrooms they are not. The area around Opportunity’s landing site is littered with them – they can be seen all over the surface and were also found buried beneath the soil and even embedded within rocks.</p>
<h2>Fossilised worms</h2>
<p>These space “mushrooms” were not the first claim of alien life. On August 7, 1996, the then US president Bill Clinton stood on the White House lawn and <a href="https://www.youtube.com/watch?v=pHhZQWAtWyQ">announced</a> the possibility that scientists had <a href="https://science.sciencemag.org/content/273/5277/924">discovered</a> the ancient, fossilised remains of micro-organisms in a meteorite that had been recovered from Antarctica in 1984. </p>
<p>The meteorite, <a href="https://curator.jsc.nasa.gov/antmet/mmc/alh84001.pdf">ALH 84001</a>, is one of a handful of rocks we have from Mars. These were blasted off the surface of the planet by volcanic eruptions or meteorite impacts, drifted through space probably for millions of years, before ending up on Earth. </p>
<figure class="align-center ">
<img alt="Image of the tube-like structures in meteorite." src="https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402105/original/file-20210521-23-hldyo3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">High-resolution scanning electron microscope image of the structures.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>The tiny structures discovered within, using powerful microscopes, resemble microscopic worm-like organisms and are likely to be billions of years old. Debate over the true origins of these structures continues today – many scientists have pointed out that well known inorganic processes are quite capable of producing structures which resemble <a href="https://www.spiedigitallibrary.org/conference-proceedings-of-spie/3755/1/Morphological-behavior-of-inorganic-precipitation-systems/10.1117/12.375088.short?SSO=1">living organisms</a>. In other words, simply because something might look a bit like life (mushrooms or otherwise), that does not mean it is.</p>
<h2>Mystery gases</h2>
<p>In the 1970s Nasa’s <a href="https://www.nasa.gov/redplanet/viking.html">Viking</a> robotic landers carried a series of experiments designed to test the Martian soil for the presence of microorganisms.</p>
<p>The experiments chemically treated small samples of Martian soil in reaction chambers on board the landers. In <a href="https://pubmed.ncbi.nlm.nih.gov/17797094/">one of them</a>, nutrients containing radioactive carbon-14 were added to the soil samples. In theory, this should be absorbed by any growing and multiplying microbes. The carbon-14 would then increasingly be “breathed out” over time, showing a steady increase in concentration within the reaction chamber. </p>
<p>After the chemical analyses, each soil sample was steadily heated to hundreds of degrees to destroy any microbes, with the intention of seeing whether any such reactions in the soil ceased. Intriguingly, this particular experiment did show a steady increase in carbon-14 over time which was indeed terminated after heating to above the boiling point of water. Several inorganic chemical reactions have been proposed as an explanation. These results therefore remain inconclusive and are still <a href="https://www.liebertpub.com/doi/10.1089/ast.2015.1464">debated today</a>.</p>
<p>More recently, minute <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103504002222?via%3Dihub">quantities of methane</a> have been found in the Martian atmosphere. This is also intriguing as living organisms on Earth are known to release methane. Once again, however, it must be stressed that this not conclusive proof of life. Methane can also be produced by several inorganic processes, including <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005GL022691">by heated rocks</a>. </p>
<h2>Wow!</h2>
<p>In 1977, the <a href="http://www.bigear.org">Big Ear radio telescope </a> in the US detected <a href="https://www.npr.org/sections/krulwich/2010/05/28/126510251/aliens-found-in-ohio-the-wow-signal?t=1621518932396">an unusual radio signal</a> while scanning the sky. The signal lasted for just a couple of minutes, was very high powered and was detected over a narrow range of frequencies. These factors make it quite difficult to envisage a natural cause, as most natural radio sources can be detected across a wide range of frequencies.</p>
<p>The exact signal has not been detected again since, despite frequent radio surveys of the same part of the sky. The signal was so remarkable at the time that the astronomer on duty, <a href="https://www.universetoday.com/tag/jerry-ehman/">Jerry Ehman</a>, circled the print out of the signal with red pen and wrote “Wow!” next to it. </p>
<p>Various explanations have been proposed over the years including, recently, that the signal was generated by a <a href="https://www.popularmechanics.com/space/solar-system/a26767/wow-signal-mystery-solved/">passing comet</a>, or transmissions from an Earth-orbiting satellite. The exact origin of the Wow! signal is still not fully agreed upon today, and remains an intriguing mystery.</p>
<h2>Tabby’s Star</h2>
<p>A key tool of planet hunting is the dimming method – observing light from a star to see if it periodically dips in a regular fashion as an orbiting planet passes in front of it. In 2015, professional astronomers working with citizen scientists from the <a href="https://www.zooniverse.org/projects/nora-dot-eisner/planet-hunters-tess">Planet Hunters</a> project announced the discovery of a nearby star displaying unusually strong and consistent dimming over time. </p>
<figure class="align-center ">
<img alt="Artist's impression of an alien megastructure." src="https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=316&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=316&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=316&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=398&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=398&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402106/original/file-20210521-19-q8e8og.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=398&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Alien megastructure?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/hypothetic-alien-megastructure-dyson-swarm-sphere-1176074824">Droneandy/Shutterstock</a></span>
</figcaption>
</figure>
<p>Tabby’s Star is named after astronomer <a href="https://www.lsu.edu/physics/people/faculty/boyajian.php">Tabitha Boyajian</a> who was lead author on the <a href="https://academic.oup.com/mnras/article/457/4/3988/2589003">paper announcing the discovery</a>. Data from the <a href="https://exoplanets.nasa.gov/keplerscience/">Kepler Space Telescope</a> showed not just a regular dimming, as one might expect from a planetary orbit, but highly irregular dips in the light and, interestingly, a consistent decrease in light output over several years. </p>
<p>This highly unusual behaviour prompted numerous theories to explain the observations, including cometary dust or debris from a massive impact gradually spreading out to cover the face of the star. Some also speculated that these were signatures of an advanced alien species building a structure around the star. But further observations have found no corroborating evidence to support this possibility. For example, radio telescopes have <a href="https://iopscience.iop.org/article/10.3847/0004-637X/825/2/155">failed to detect</a> any unusual radio emissions from the star. Today, the scientists behind the discovery believe that the unusual dips in light are caused by clouds of cosmic dust <a href="https://www.nationalgeographic.com/science/article/mystery-of--alien-megastructure--star-has-been-cracked">passing across the face of the star</a>. </p>
<p>As exciting as they are, it is important to treat claims of alien life with a healthy dose of scepticism, and this is indeed what scientists do. No conclusive evidence that extraterrestrial life exists has been found … yet.</p><img src="https://counter.theconversation.com/content/161366/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gareth Dorrian does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>No conclusive evidence that extraterrestrial life exists has been found…yet.Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1603232021-05-12T11:28:14Z2021-05-12T11:28:14ZSeti: how microbes could communicate with alien species<figure><img src="https://images.theconversation.com/files/400296/original/file-20210512-21-1fpuk7e.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6500%2C3279&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Are microbes travelling around in the galaxy?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/landscape-milky-way-galaxy-sunrise-earth-1299679972">Nuttawut Uttamaharad</a></span></figcaption></figure><p>Are we alone in the universe? The famous Seti (Search for Extraterrestrial Intelligence) programme has been trying to answer this question since 1959. American astronomer Carl Sagan, and many others, believed that other human-like civilisations must exist, and that we could communicate with them. But sceptics are not convinced, arguing the lack of evidence for such civilisations suggests they are <a href="https://www.liebertpub.com/doi/10.1089/ast.2019.2149">exceedingly rare</a>. </p>
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<p>But if other human-like civilisations are unlikely to exist, could there exist other forms of life – perhaps better suited than us to spread in the cosmos? And would it be possible for such lifeforms to communicate with each other (non-human Seti)? Our new study, <a href="https://www.sciencedirect.com/science/article/pii/S0303264721000964?dgcid=author">published in Biosystems</a>, suggests it would. Microbes, such as bacteria, may be rulers of the cosmic life – and they are a lot more intelligent than we give them credit for. Indeed, we show how microbes could mimic the Seti programme without human interference.</p>
<p>To understand microbes, we need to challenge our anthropocentric prejudices. While many of us see microbes as single-cell organisms that cause diseases, the reality is different. Microbes are loosely organised multi-cellular entities. Bacteria, for example, live as member societies of several billion – colonies capable of “thinking” and decision-making. </p>
<p>A typical bacterial colony is a cybernetic entity – <a href="https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/j.1749-6632.2009.05022.x">a “superbrain”</a> that solves environmental problems. More importantly, all bacterial colonies on Earth are interconnected into a global bacterial supersystem dubbed the bacteriosphere. This <a href="https://link.springer.com/content/pdf/10.1007/s101230100015.pdf">“world-wide-web” of genetic information</a> has been regulating the flow of organic elements on Earth over the past three billion years, in a manner that will forever remain <a href="https://www.researchgate.net/publication/5794057_Bacteria_are_small_but_not_stupid_Cognition_natural_genetic_engineering_and_socio-bacteriology">beyond human capacities</a>. For example, they cycle important nutrients such as carbon, nitrogen and sulphur.</p>
<p>Even today, bacteria are the <a href="https://www.nature.com/articles/nmicrobiol201648">most dominant living beings on Earth</a>. Take bacteria out of the biosphere, and life will gradually collapse. Bacteria may therefore be far more suited for cosmic travel and communication than us. A <a href="https://www.frontiersin.org/articles/10.3389/fmicb.2020.02050/full">recent study</a> found that terrestrial bacteria can survive in space for at least three years, possibly more. Add to this the fact that bacteria can exist in a dormant state for <a href="https://www.nature.com/articles/s41467-020-17330-1?ftag=MSF0951a18">millions of years</a>, and it’s clear that microbes are very resilient.</p>
<p>Indeed, various versions of the <a href="https://ui.adsabs.harvard.edu/abs/2019asbi.book..419K/abstract">panspermia hypothesis</a> – which states that microbial life exists and travels throughout the universe – support this notion. Recent <a href="https://iopscience.iop.org/article/10.3847/2041-8213/aaef2d">mathematical models</a> have backed this by showing that microbial travel may be possible not only in our solar system, but throughout the galaxy. </p>
<h2>Microbial Seti</h2>
<p>How could the microbial Seti work? We believe that the bacteriosphere could potentially replicate all steps known from human Seti. Step one in human Seti is the capacity to read cosmic-scale information. For example, using radio telescopes we can analyse distant habitable planets. Step number two is to develop technologies and knowledge to assess whether habitable planets contain life. Step three is to advertise our presence on Earth to intelligent extraterrestrials and attempt to make a contact with them if they respond to initial signals.</p>
<p>Our version of microbial Seti is shown in the picture below. Microbes have a limited capacity to read the cosmic-scale information. For example, cyanobacteria can read the portion of the electromagnetic spectrum coming from the Sun in the form of visible light (step one). This biological phenomenon is called <a href="https://www.bbc.co.uk/bitesize/guides/zpt4xfr/revision/1">phototropism </a>and happens, for example, when a plant turn towards or away from the Sun or other light source.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/400097/original/file-20210511-24-p5k1tw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">microbial seti.</span>
</figcaption>
</figure>
<p>Step two was crucial to the development of life on Earth. <a href="https://www.cdc.gov/habs/pdf/cyanobacteria_faq.pdf">Cyanobacteria</a> developed a bio-technology in the form of photosynthesis (which turns water, sunlight, and carbon dioxide into oxygen and nutrients). This transformed the dead planet into a living one, or the bacteriosphere, over a long evolutionary period. Microbial life then got more complex, creating plants and animals in the past 600 million years. Yet bacteria remain the most dominant life form on the planet. Photosynthesis, as a form of bacterial technology, has always fuelled life on Earth.</p>
<p>Step three is all about attraction and communication between microbes with similar chemistries. Extraterrestrial microbes should be able to seamlessly integrate into the Earth’s bacteriosphere if they share carbon-based chemistry and metabolism, including DNA, proteins and other biomolecules. The opposite process is also possible. Microbes from Earth could travel into space on asteroids and seed life elsewhere in the cosmos. Alternatively, humans, as future cosmic travellers, could act as microbial vectors by virtue of the human microbiome.</p>
<p>To appreciate microbial Seti we need to understand the concept of intelligence in the evolutionary sense. This will enable us to evaluate better the bacterial intelligence, and its capacities in the context of human and microbial Seti. Some biologists argue that human intelligence is just a fragment in a wide spectrum of natural intelligence that includes microbes and plants.</p>
<p>We also need to reevaluate technological signatures as signs of intelligent civilisations. Technologically advanced civilisations, according to the physicist <a href="https://www.theguardian.com/science/2020/mar/01/freeman-dyson-obituary">Freeman Dyson</a>, must have huge energy demands. These demands may be achieved by building cosmic megastructures, dubbed Dyson spheres, around their planets that can capture the energy from their host star. Searching for such spheres by looking at whether light from stars is blocked could therefore be a way of finding them.</p>
<p>But, if human-like civilisations are indeed rare, there is no point in <a href="https://theconversation.com/what-are-the-odds-of-an-alien-megastructure-blocking-light-from-a-distant-star-49311">searching for such structures</a>. Instead, it may be more appropriate to search for biosignatures as signs of microbial life on habitable planets. </p>
<p>The way forward in the search for extraterrestrial life may be to look for <a href="https://www.sciencedirect.com/science/article/pii/0004698172900765?via%3Dihub">gases in atmosheres</a> of planets that signify life, such as oxygen methane or phosphine, which are all produced by microbes. The finding of phosphine in Venus’ atmosphere was a promising lead but it now <a href="https://www.washington.edu/news/2021/01/27/phosphine-venus-so2/">looks doubtful</a>, as a new study suggest the signal could have been sulfur dioxide rather than phosphine. Yet we have no choice but to keep trying. Luckily, the <a href="https://theconversation.com/how-hubbles-successor-will-give-us-a-glimpse-into-the-very-first-galaxies-45970">James Webb Space Telescope</a> should be able to scan the atmosphere of planets orbiting stars other than our Sun when it launches later this year.</p><img src="https://counter.theconversation.com/content/160323/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Predrag Slijepcevic received funding from various organisations including Department of Health, EU, Royal Society and British Council. </span></em></p><p class="fine-print"><em><span>Nalin Chandra Wickramasinghe does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new study argues we should search for microbial life rather than human-like aliens.Predrag Slijepcevic, Senior Lecturer in Biology, Brunel University LondonNalin Chandra Wickramasinghe, Honorary Professor, University of BuckinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1555092021-02-18T14:50:16Z2021-02-18T14:50:16ZHas Earth been visited by an alien spaceship? Harvard professor Avi Loeb vs everybody else<figure><img src="https://images.theconversation.com/files/384998/original/file-20210218-16-8c2xlv.jpg?ixlib=rb-1.1.0&rect=0%2C26%2C2522%2C1619&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's impression of 'Oumuamua.</span> <span class="attribution"><span class="source"> ESO/M. Kornmesser </span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>A highly unusual object <a href="http://www.ifa.hawaii.edu/info/press-releases/interstellar/">was spotted</a> travelling through the solar system in 2017. Given a Hawaiian name,ʻOumuamua, it was small and elongated – a few hundred metres by a few tens of meters, travelling at a speed fast enough to escape the Sun’s gravity and move into interstellar space.</p>
<p>I was at a meeting when the discovery of ʻOumuamua was announced, and a friend immediately said to me, “So how long before somebody claims it’s a spaceship?” It seems that whenever astronomers discover anything unusual, somebody claims it must be aliens.</p>
<p>Nearly all scientists believe that ʻOumuamua probably originates from outside the solar system. It is an <a href="https://theconversation.com/comet-or-asteroid-mysterious-oumuamua-shows-why-we-may-need-a-new-classification-system-99083">asteroid- or comet-like object</a> that has left another star and travelled through interstellar space - we saw it as it zipped by us. But not everyone agrees. <a href="https://www.cfa.harvard.edu/%7Eloeb/">Avi Loeb</a>, a Harvard professor of astronomy, <a href="https://www.scientificamerican.com/article/astronomer-avi-loeb-says-aliens-have-visited-and-hes-not-kidding1/">suggested in a recent book</a> that it is indeed an alien spaceship. But how feasible is this? And how come most scientists disagree with the claim?</p>
<p>Researchers estimate that the Milky Way should contain around 100 million billion billion comets and asteroids ejected from other planetary systems, and that one of these <a href="https://academic.oup.com/mnrasl/article/478/1/L49/4925005">should pass through our solar system</a> every year or so. So it makes sense that ‘Oumuamua could be one of these. We <a href="https://www.nasa.gov/feature/interstellar-comet-borisov-reveals-its-chemistry-and-possible-origins/">spotted another last year</a> – “Borisov” – which suggests they are as common as we predict.</p>
<p>What made ʻOumuamua particularly interesting was that it didn’t follow the orbit you would expect – its trajectory shows it has some extra “non-gravitational force” acting on it. This is not too unusual. The pressure of solar radiation or gas or particles driven out as an object warms up close to the Sun can give extra force, and <a href="https://ui.adsabs.harvard.edu/abs/2018Natur.559..223M/abstract">we see this with comets all the time</a>. </p>
<p>Experts on comets and the solar system <a href="https://theconversation.com/mysterious-alien-cigar-asteroid-is-actually-an-interstellar-lump-of-ice-not-a-space-ship-89322">have explored</a> various explanations for this. Given this was a small, dark object passing us very quickly before disappearing, the images we were able to get weren’t wonderful, and so it is difficult to be sure.</p>
<figure class="align-right ">
<img alt="Image of Avi Loeb." src="https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=769&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=769&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=769&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=966&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=966&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=966&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Avi Loeb.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Loeb, however, believes that ʻOumuamua is an alien spaceship, powered by a “light sail” – a method for propelling a spacecraft using radiation pressure exerted by the Sun on huge mirrors. He argues the non-gravitational acceleration is a sign of “deliberate” manoeuvring. This argument seems largely to be based on the fact that ʻOumuamua lacks a fuzzy envelope (“coma”) and a comet-like tail, which are usual signatures of comets undergoing non-gravitational acceleration (although jets from particular spots cannot be ruled out).</p>
<h2>Sanity checks</h2>
<p>He may or may not be right, and there is no way of proving or disproving this idea. But claims like this, especially from experienced scientists are disliked by the scientific community for many reasons.</p>
<p>If we decide that anything slightly odd that we don’t understand completely in astronomy could be aliens, then we have a lot of potential evidence for aliens – there is an awful lot <a href="https://theconversation.com/cosmology-is-in-crisis-but-not-for-the-reason-you-may-think-52349">we don’t understand</a>. To stop ourselves jumping to weird and wonderful conclusions every time we come across something strange, science has several sanity checks.</p>
<p>One is <a href="https://plato.stanford.edu/entries/simplicity/">Occam’s razor</a>, which tells us to look for the simplest solutions that raise the fewest new questions. Is this a natural object of the type that we suspect to be extremely common in the Milky Way, or is it aliens? Aliens raise a whole set of supplementary questions (who, why, from where?) which means Occam’s razor tells us to reject it, at least until all simpler explanations are exhausted. </p>
<p>Another sanity check is <a href="https://bigthink.com/personal-growth/how-the-sagan-standard-can-help-you-make-better-decisions?rebelltitem=1#rebelltitem1">the general rule</a> that “extraordinary claims require extraordinary evidence”. A not quite completely understood acceleration is not extraordinary evidence, as there are many plausible explanations for it.</p>
<p>Yet another check is the often sluggish but usually reliable peer-review system, in which scientists publish their findings in scientific journals where their claims can be assessed and critiqued by experts in their field.</p>
<h2>Alien research</h2>
<p>This doesn’t mean that we shouldn’t look for aliens. A lot of time and money is being devoted to researching them. For astronomers who are interested in the proper science of aliens, there is “astrobiology” – the science of looking for life outside Earth based on signs of biological activity. On February 18, Nasa’s Perseverance rover will land on Mars and look for molecules <a href="https://theconversation.com/perseverance-mars-rover-how-to-prove-whether-theres-life-on-the-red-planet-154982">which may include such signatures</a>, for example. Other interesting targets are the moons of Jupiter and Saturn.</p>
<figure class="align-center ">
<img alt="Image of Jupiter's moon Europa." src="https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Jupiter’s moon Europa may harbour simple life in its internal ocean.</span>
<span class="attribution"><span class="source">NASA/JPL/DLR</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In the next five years, we will also <a href="https://exoplanets.nasa.gov/search-for-life/can-we-find-life/">have the technology</a> to search for alien life on planets around other stars (exoplanets). Both the <a href="https://theconversation.com/how-hubbles-successor-will-give-us-a-glimpse-into-the-very-first-galaxies-45970">James Webb Space Telescope</a> (due to launch in 2021), and the <a href="https://www.eso.org/sci/facilities/eelt/">European Extremely Large Telescope</a> (due for first light in 2025) will analyse exoplanet atmospheres in detail, searching for signs of life. For example, the oxygen in the Earth’s atmosphere is there because life constantly produces it. Meanwhile, <a href="https://theconversation.com/seti-new-signal-excites-alien-hunters-heres-how-we-could-find-out-if-its-real-152498">the Search for Extraterrestrial Intelligence (Seti)</a> initiative has been scanning the skies with radio telescopes for decades in search of messages from intelligent aliens. </p>
<p>Signs of alien life would be an amazing discovery. But when we do find such evidence, we want to be sure it is good. To be as sure as we can be, we need to present our arguments to other experts in the field to examine and critique, follow the scientific method which, in its slow and plodding way, gets us there in the end. </p>
<p>This would give us much more reliable evidence than claims from somebody with a book to sell. It is quite possible, in the next five to ten years, that somebody will announce that they have found good evidence for alien life. But rest assured this isn’t it.</p><img src="https://counter.theconversation.com/content/155509/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Goodwin does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There’s a good reason why so many scientists disagree with claims that Earth has been visited by aliens.Simon Goodwin, Professor of Theoretical Astrophysics, University of SheffieldLicensed as Creative Commons – attribution, no derivatives.