tag:theconversation.com,2011:/fr/topics/galileo-2604/articles
Galileo – The Conversation
2023-12-28T19:34:18Z
tag:theconversation.com,2011:article/219183
2023-12-28T19:34:18Z
2023-12-28T19:34:18Z
Larger and more frequent solar storms will make for potential disruptions and spectacular auroras on Earth
<figure><img src="https://images.theconversation.com/files/564592/original/file-20231208-29-521tjc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1669%2C1669&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A sunspot emitting a flare on the surface of the sun. </span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details/PIA22645">(NASA/GSFC/Solar Dynamics Observatory)</a></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/larger-and-more-frequent-solar-storms-will-make-for-potential-disruptions-and-spectacular-auroras-on-earth" width="100%" height="400"></iframe>
<p>Bright auroras, with dancing lights in the sky, characterize the clear winter nights of northern Canada. Longer nights during the fall and winter also favour seeing more auroras, but the show is best outside of light-polluted cities. Impressive auroral events allowed bright auroras to be seen <a href="https://spaceweathergallery2.com/indiv_upload.php?upload_id=202170">as far south as the United States recently</a>. </p>
<p>Auroras are produced through the sun’s interaction with the Earth’s magnetic field. The number of auroras is increasing as <a href="https://www.swpc.noaa.gov/products/solar-cycle-progression">the sun’s activity becomes stronger</a>, approaching a solar maximum. </p>
<p>Perhaps surprisingly, the same space disturbances that cause auroras can affect our technologies.</p>
<p>In 1859, a geomagnetic storm — the largest in recorded history — disrupted technological systems, such as they were at the time, on Earth. Referred to as the “<a href="https://www.space.com/the-carrington-event">Carrington Event</a>” after Richard Carrington, the amateur astronomer who made the connection between a bright solar flare and subsequent auroral and magnetic effects. </p>
<p>That Sun-Earth link was slow to be accepted, but we now know that the Sun can trigger disturbances in near-Earth space, although it seems that events as large as that of 1859 are rare. </p>
<h2>Night visions</h2>
<p>Space is filled with thin hot gas called plasma that <a href="https://svs.gsfc.nasa.gov/14299/">carries magnetic fields</a>. The Earth, in the sun’s outer atmosphere, is surrounded by hot magnetic plasma which rushes past us at speeds of several hundred kilometres per second <a href="https://www.nasa.gov/solar-system/parker-solar-probe-and-the-birth-of-the-solar-wind/">in a flow called the solar wind</a>.</p>
<p>The sun is so massive that loss of the solar wind has a negligible effect on it, but Earth by comparison is a mere speck, three parts in a million as massive. <a href="https://www.nasa.gov/image-article/earths-magnetosphere-3/">Earth has a magnetic field</a>, which protects us from the solar onslaught, but is pushed back by it as well.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a blue ball of light" src="https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/564595/original/file-20231209-17-dta2j1.gif?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">These active regions may dramatically flare up in X-ray intensity, affecting Earth’s upper atmosphere and making a hazard for astronauts.</span>
<span class="attribution"><span class="source">(Solar Dynamics Observatory/NASA)</span></span>
</figcaption>
</figure>
<p>Under certain conditions, energy can flow into the near-Earth region from the solar wind, largely building up on the opposite side from the sun in a comet-like “<a href="https://www.jstor.org/stable/24975910">magnetotail</a>.”</p>
<p>This can become unstable if too much energy builds up, blasting particles into the nightside atmosphere to light up auroras. This explains why auroras are seen at night: not only is it dark, but the sun’s energy takes an indirect route by first being stored in the magnetotail.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/o4FSg-90XlA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A NASA video explaining the magnetosphere.</span></figcaption>
</figure>
<p>The dancing auroras can also generate magnetic fields, which are strong enough to be detected by a compass, as discovered nearly 300 years ago by <a href="https://www.britannica.com/biography/Anders-Celsius">Swedish astronomer Anders Celsius</a>.</p>
<p>If the magnetic fields change rapidly, they can affect large regions of the Earth, building up to cause problems for power networks. This notably happened in North America in 1989, on the “<a href="https://spaceweatherarchive.com/2021/03/12/the-great-quebec-blackout">day the sun brought darkness</a>.”</p>
<h2>Solar cycles</h2>
<p>Italian astronomer Galileo studied sunspots in a systematic way in <a href="http://galileo.rice.edu/sci/observations/sunspots.html">the early 1600s</a>. About 300 years later, American astronomer George Hale showed that sunspots had intense magnetic fields, <a href="https://www2.hao.ucar.edu/education/scientists/george-ellery-hale-1868-1938">several thousand times stronger than Earth’s</a>. </p>
<p>In the 400 years since Galileo’s observations, we have found that the number of sunspots varies dramatically over <a href="https://www.swpc.noaa.gov/phenomena/sunspotssolar-cycle">an 11-year long cycle</a>. But it is only recently, in the Space Age, that we can relate its effects on Earth.</p>
<h2>Energy storage</h2>
<p>Magnetic fields store energy, and sometimes, as in Earth’s magnetotail or near sunspots, this energy can be changed to other forms. In the strong fields of sunspots, it can be released as X-rays in <a href="https://www.youtube.com/watch?v=64CTIrWBGTc">rapid, unpredictable flares</a>. </p>
<p>Sunspots and flares are near the surface or light-emitting layer of the sun, but <a href="https://www.swpc.noaa.gov/news/strongest-solar-flare-solar-cycle-25">material can escape from the sun’s strong gravity field</a>. Blobs of gas — <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejections</a> — can be hurtled into space. Some small fraction of these are shot out toward Earth, and auroras and their magnetic effects occur when they reach Earth’s atmosphere. They can also cause intensification of our radiation belts in ways that <a href="https://doi.org/10.1511/2014.110.374">can damage satellites</a>.</p>
<p>Counting sunspots on the sun’s surface allows us to get a general idea of what space disturbances may occur as the solar cycle progresses. Similarly, on Earth we can follow the seasons and have a general idea of what storms are likely. In both cases, however, exact prediction is difficult.</p>
<h2>Space weather forecasts</h2>
<p>From long-term trends, it was expected that the upcoming solar maximum would be small, as indeed <a href="https://doi.org/10.1051/swsc/2020060">the one that peaked in 2014 was</a>. However, in this, <a href="https://www.nasa.gov/news-release/solar-cycle-25-is-here-nasa-noaa-scientists-explain-what-that-means/">the following solar cycle</a>, we have already exceeded predicted numbers of sunspots and had large magnetic storms, so predictions may need to be revised upward. </p>
<p>Although direct measurement of incoming disturbances by satellites in the solar wind gives us only about an hour’s warning of stormy space weather, we can also predict a bit further in advance by watching sunspots rotate into view as the sun turns. </p>
<p>One solar rotation takes about as long as it does for the moon to go around Earth, that is to say, a month. So if a particular sunspot brings lots of activity, it likely will repeat in about a month.</p>
<h2>Rare storms</h2>
<p>The strongest flare of <a href="https://www.swpc.noaa.gov/news/sunspot-region-produces-x28-flare-largest-sep-10-2017">Solar Cycle 25 so far occurred on Dec. 14</a>, and was the most powerful eruption the sun has produced <a href="https://www.nasa.gov/missions/goes/september-2017s-intense-solar-activity-viewed-from-space">since the great storms of September 2017</a>.</p>
<p>Large solar storms are rare, but we must calmly prepare for possible space weather impacts that should maximize in a few years. We must be creative, since space weather effects can bring surprises. In 2022, unexpected heating of the atmosphere caused <a href="https://www.space.com/spacex-starlink-satellite-loss-space-weather-forecast">multiple satellite losses</a>. </p>
<p>As our knowledge of space physics steadily improves, so too will the new science of space weather prediction, allowing us to protect our technological assets. </p>
<p>In the meantime, we can look forward to spectacular auroras that should come as we near the 2025 solar maximum, with only measured and reasonable amounts of worry about the potential impacts of space weather.</p><img src="https://counter.theconversation.com/content/219183/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Gerard Connors receives funding from Canada's NSERC. </span></em></p>
The sun is expected to reach its solar maximum in 2025. Recent auroras suggest that the maximum may be bigger than predicted.
Martin Connors, Professor of Space Science and Physics, Athabasca University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/212317
2023-12-01T13:39:03Z
2023-12-01T13:39:03Z
Bringing classical physics into the modern world with Galileo’s Leaning Tower of Pisa experiment
<figure><img src="https://images.theconversation.com/files/549591/original/file-20230921-26-bwlj7n.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C1024%2C768&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Galileo, holding two balls, about to perform his legendary experiment. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/italian-astronomer-and-scientist-galileo-galilei-performs-news-photo/50965500?adppopup=true">Hulton Archive/Stringer via Getty Images</a></span></figcaption></figure><p>If you drop a light object and a heavy object from a tower, which one reaches the ground first? As you may recall from high school physics, this is a trick question. Neglecting air resistance, they both fall the same way and reach the ground at the same time – gravity means that their speeds increase at 9.8 meters per second squared, no matter what their mass. </p>
<p>That’s the premise behind <a href="https://www.britannica.com/biography/Galileo-Galilei">Galileo Galilei’s</a> Leaning Tower of Pisa experiment, a classic thought experiment in the field of dynamics.</p>
<p>Dynamics is the physics specialization that studies motion and force. A “dynamicist,” one who studies dynamics, can do everything from improve a basketball player’s <a href="https://theconversation.com/the-math-behind-the-perfect-free-throw-91727">free throw</a> to help design spacecraft for <a href="https://doi.org/10.2514/1.A35684">interstellar travel</a>. </p>
<p>As a <a href="https://www.mae.ncsu.edu/people/lmsilver/">dynamicist</a>, I’ve spent much of my career helping students make sense of modern dynamics. The <a href="https://www.youtube.com/watch?v=E43-CfukEgs&t=170s">Leaning Tower of Pisa experiment</a> is one good way to do this. It can explain how classical mechanics – the field that engineers and educators employ every day – was brought into the modern world.</p>
<h2>Galileo’s Leaning Tower of Pisa experiment</h2>
<p>The Leaning Tower of Pisa experiment led to the curious realization that objects fall with the same accelerations regardless of their mass. But what happens when you place objects of different masses on a smooth table and push each of them with the same force? </p>
<p><a href="https://www.britannica.com/science/tribology">Even without accounting for friction</a>, the objects’ accelerations are now different. The lighter objects accelerate more than the heavy ones. When falling, their accelerations are the same, yet when sliding, they’re different. </p>
<p>Let’s now place the two objects <a href="https://education.nationalgeographic.org/resource/orbit/">in orbit</a>. Imagine one of them is the Sun and the other is the Earth. In classical mechanics, the Sun exerts a force on the Earth equal in magnitude to the force that the Earth exerts back on the Sun. </p>
<p>But <a href="https://www.space.com/17001-how-big-is-the-sun-size-of-the-sun.html">the Sun is huge compared with the Earth</a>. Shouldn’t the magnitude of the larger object’s force be larger? And while we’re at it, how would the magnitude of the Sun’s force on the Earth come to be equal to the magnitude of the Earth’s force on the Sun? </p>
<p>Heavy and light objects have equal accelerations when falling but different accelerations when sliding, and objects in space exert equal gravitational forces on each other despite having different masses. This all seems inconsistent, and a little confusing, right?</p>
<h2>Modern mechanics</h2>
<p>The problems above came from an ambiguity in the concept of force in classical mechanics. In classical mechanics, the <a href="https://doi.org/10.2514/1.A35684">force is an interaction</a> between two objects, involving both objects. The magnitudes of the gravitational forces by the Sun and by the Earth depend on the masses of both bodies. The force was never just by the Sun or just by the Earth without regard to the other.</p>
<p>But <a href="http://labman.phys.utk.edu/phys222core/modules/m10/modern_physics.html">modern mechanics</a> – the physics of light, atoms, quantum mechanics and curved space-time – changed this concept of force. The modern force by the Sun and the modern force by the Earth are two separate forces, and they depend only on their own masses, excluding <a href="https://www.ingentaconnect.com/contentone/pe/pe/2021/00000034/00000004/art00015?crawler=true">relativistic effects</a>.</p>
<p>In modern mechanics, the force is now an <a href="https://doi.org/10.2514/1.A35684">action by an object</a>, not an interaction between them. It is viewed as a <a href="https://galileo.phys.virginia.edu/classes/152.mf1i.spring02/GravField.htm">force field</a> that radiates outward from its source, whose magnitude grows smaller the farther it is from its source. Modern mechanics is a <a href="https://doi.org/10.2514/1.A35684">field theory</a> – it deals with objects and the accelerations their force fields create. </p>
<p>So, what happened to the interaction force? Was it discarded? The answer is no, but it is no longer the most fundamental definition of force, either. In modern mechanics, the interaction force, represented by the letter F, is defined in terms of the action force field, represented by the letter P. The interaction force is now the <a href="https://cdn.theconversation.com/static_files/files/2945/2023-11-24_figure_of_modern_to_classical.pdf?1700836147">action force</a> P times the mass m on which P acts, so F = mP.</p>
<p>Newton’s <a href="https://maa.org/press/periodicals/convergence/mathematical-treasure-english-translation-of-newton-s-principia-mathematica">second law of motion</a>, a fundamental part of classical mechanics, sets the interaction force F by an object equal to the mass m on which the object acts multiplied by its acceleration, so F = ma. The modern version sets the action force P by an object equal to the other object’s acceleration, so P = a. When multiplying P = a by m we get back F = ma. </p>
<p>Notice it was not about the math in classical mechanics being wrong – but more about the fundamental force being an action force and not an interaction force. </p>
<h2>The modern thinking</h2>
<p>The modern thinking reinterprets Galileo’s <a href="https://www.youtube.com/watch?v=E43-CfukEgs&t=170s">Leaning Tower of Pisa experiment</a>, the sliding blocks, the orbiting of the Earth around the Sun – and interactions in general. </p>
<p>In Galileo’s Leaning Tower of Pisa experiment, the light and heavy objects were falling due to the Earth’s action force, which does not depend on the masses of the falling objects, so their accelerations are naturally the same. </p>
<p>The light and heavy objects sliding on the smooth table were acted on by the same interaction forces. But the fundamental forces – the action forces – are different, so their accelerations are naturally different, too. </p>
<p>In the orbiting of the Earth around the Sun, the action forces by the Sun and by the Earth are no longer equal. The action force by the Sun, with its huge mass, is proportionally larger than the force by the Earth – as intuition suggests. </p>
<p>Science takes many years to evolve as it edges closer to revealing the nature of reality. One sees this in the evolution that led to modern mechanics – where scientists now embrace a theory of force fields that predicts the dynamics of objects, despite it being almost against common sense.</p><img src="https://counter.theconversation.com/content/212317/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Larry M. Silverberg 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>
A centuries-old experiment shows the differences between classical and modern physics. Physicists use thought experiments like this to think about how objects move both on Earth and in the stars.
Larry M. Silverberg, Professor of Mechanical and Aerospace Engineering, North Carolina State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/197189
2023-03-20T12:45:51Z
2023-03-20T12:45:51Z
Why does time change when traveling close to the speed of light? A physicist explains
<figure><img src="https://images.theconversation.com/files/514967/original/file-20230313-19-rrsoxs.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Time gets a little strange as you approach the speed of light.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/stars-light-motion-in-space-royalty-free-image/510216640">ikonacolor/iStock via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Why does time change when traveling close to the speed of light? – Timothy, age 11, Shoreview, Minnesota</strong></p>
</blockquote>
<hr>
<p>Imagine you’re in a car driving across the country watching the landscape. A tree in the distance gets closer to your car, passes right by you, then moves off again in the distance behind you.</p>
<p>Of course, you know that tree isn’t actually getting up and walking toward or away from you. It’s you in the car who’s moving toward the tree. The tree is moving only in comparison, or relative, to you – that’s what <a href="https://scholar.google.com/citations?user=QyArIUgAAAAJ&hl=en">we physicists</a> call <a href="https://www.amnh.org/exhibitions/einstein/time/its-all-relative">relativity</a>. If you had a friend standing by the tree, they would see you moving toward them at the same speed that you see them moving toward you.</p>
<p>In his 1632 book “<a href="https://www.loc.gov/item/12018406/">Dialogue Concerning the Two Chief World Systems</a>,” the astronomer Galileo Galilei first described the <a href="https://www.phys.unsw.edu.au/einsteinlight/jw/module1_Galileo_and_Newton.htm">principle of relativity</a> – the idea that the universe should behave the same way at all times, even if two people experience an event differently because one is moving in respect to the other.</p>
<p>If you are in a car and toss a ball up in the air, the physical laws acting on it, such as the force of gravity, should be the same as the ones acting on an observer watching from the side of the road. However, while you see the ball as moving up and back down, someone on the side of the road will see it moving toward or away from them as well as up and down.</p>
<h2>Special relativity and the speed of light</h2>
<p>Albert Einstein much later proposed the idea of what’s now known as <a href="https://futurism.com/special-relativity-simplified">special relativity</a> to explain some confusing observations that didn’t have an intuitive explanation at the time. Einstein used the work of many physicists and astronomers in the late 1800s to put together his theory in 1905, starting with two key ingredients: the principle of relativity and the strange observation that the speed of light is the same for every observer and nothing can move faster. Everyone measuring the speed of light will get the same result, no matter where they are or how fast they are moving. </p>
<p>Let’s say you’re in the car driving at 60 miles per hour and your friend is standing by the tree. When they throw a ball toward you at a speed of what they perceive to be 60 miles per hour, you might logically think that you would observe your friend and the tree moving toward you at 60 miles per hour and the ball moving toward you at 120 miles per hour. While that’s really close to the correct value, it’s actually slightly wrong. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/GguAN1_JouQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The experience of time is dependent on motion.</span></figcaption>
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<p>This discrepancy between what you might expect by adding the two numbers and the true answer grows as one or both of you move closer to the speed of light. If you were traveling in a rocket moving at 75% of the speed of light and your friend throws the ball at the same speed, you would not see the ball moving toward you at 150% of the speed of light. This is because nothing can move faster than light – the ball would still appear to be moving toward you at less than the speed of light. While this all may seem very strange, there is <a href="https://galileo.phys.virginia.edu/classes/252/adding_vels.html">lots of experimental evidence</a> to back up these observations.</p>
<h2>Time dilation and the twin paradox</h2>
<p>Speed is not the only factor that changes relative to who is making the observation. Another consequence of relativity is the concept of <a href="https://www.technologyreview.com/2019/12/07/65014/how-does-time-dilation-affect-aging-during-high-speed-space-travel/">time dilation</a>, whereby people measure different amounts of time passing depending on how fast they move relative to one another.</p>
<p>Each person experiences time normally relative to themselves. But the person moving faster experiences less time passing for them than the person moving slower. It’s only when they reconnect and compare their watches that they realize that one watch says less time has passed while the other says more.</p>
<p>This leads to one of the strangest results of relativity – the <a href="https://www.britannica.com/science/twin-paradox">twin paradox</a>, which says that if one of a pair of twins makes a trip into space on a high-speed rocket, they will return to Earth to find their twin has aged faster than they have. It’s important to note that time behaves “normally” as perceived by each twin (exactly as you are experiencing time now), even if their measurements disagree.</p>
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<figcaption><span class="caption">The twin paradox isn’t actually a paradox.</span></figcaption>
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<p>You might be wondering: If each twin sees themselves as stationary and the other as moving toward them, wouldn’t they each measure the other as aging faster? The answer is no, because they can’t both be older relative to the other twin. </p>
<p>The twin on the spaceship is not only moving at a particular speed where the frame of references stay the same but also accelerating compared with the twin on Earth. Unlike speeds that are relative to the observer, accelerations are absolute. If you step on a scale, the weight you are measuring is actually your acceleration due to gravity. This measurement stays the same regardless of the speed at which the Earth is moving through the solar system, or the solar system is moving through the galaxy or the galaxy through the universe. </p>
<p>Neither twin experiences any strangeness with their watches as one moves closer to the speed of light – they both experience time as normally as you or I do. It’s only when they meet up and compare their observations that they will see a difference – one that is perfectly defined by the mathematics of relativity.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/197189/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Lam 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>
Your experience of time is relative because it depends on motion – more specifically, your speed and acceleration.
Michael Lam, Assistant Professor of Physics and Astronomy, Rochester Institute of Technology
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/175813
2022-04-10T13:09:42Z
2022-04-10T13:09:42Z
A universe without mathematics is beyond the scope of our imagination
<figure><img src="https://images.theconversation.com/files/454642/original/file-20220328-19-eidckf.jpg?ixlib=rb-1.1.0&rect=0%2C16%2C5615%2C3135&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mathematics is the language of the universe. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Almost 400 years ago, in <em>The Assayer</em>, Galileo wrote: “<a href="https://web.stanford.edu/%7Ejsabol/certainty/readings/Galileo-Assayer.pdf">Philosophy is written in this grand book, the universe … [But the book] is written in the language of mathematics</a>.” He was much more than an astronomer, and this can almost be thought of as the first writing on the scientific method.</p>
<p>We do not know who first started applying mathematics to scientific study, but it is plausible that it was the <a href="https://www.wiley.com/en-ca/A+History+of+Mathematics%2C+3rd+Edition-p-9780470630563">Babylonians, who used it to discover the pattern underlying eclipses</a>, nearly 3,000 years ago. But it took 2,500 years and the invention of calculus and <a href="https://plato.stanford.edu/entries/newton-principia/">Newtonian physics</a> to explain the patterns.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Rx-5dCXx1SI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption"><em>Science Magazine</em> looks at Babylonian clay tablets that contained mathematical formulas that are a precursor to calculus.</span></figcaption>
</figure>
<p>Since then, probably every single major scientific discovery has used mathematics in some form, simply because it is far more powerful than any other human language. It is not surprising that this has led many people to claim that <a href="https://www.maths.ed.ac.uk/%7Ev1ranick/papers/wigner.pdf">mathematics is much more</a>: that the universe is <a href="https://www.scientificamerican.com/article/is-the-universe-made-of-math-excerpt/">created by a mathematician</a>. </p>
<p>So could we imagine a universe in which mathematics does not work?</p>
<h2>The language of mathematics</h2>
<p>The <a href="https://www.sciencedirect.com/topics/psychology/sapir-whorf-hypothesis">Sapir-Whorf hypothesis</a> asserts that you cannot discuss a concept unless you have the language to describe it.</p>
<p>In any science, and physics in particular, we need to describe concepts that do not map well on to any human language. One can describe an electron, but the moment we start asking questions like “What colour is it?” we start to realize the inadequacies of English. </p>
<p>The colour of an object depends on the wavelengths of light reflected by it, so an electron has no colour, or more accurately, all colours. The question itself is meaningless. But ask “How does an electron behave?” and the answer is, in principle, simple. In 1928, Paul A.M. Dirac wrote down <a href="https://www.sciencedirect.com/topics/physics-and-astronomy/dirac-equation">an equation</a> that describes the behaviour of an electron almost perfectly under all circumstances. This does not mean it is simple when we look at the details. </p>
<p>For example, an electron behaves as a tiny magnet. The magnitude can be calculated, but the <a href="https://arxiv.org/pdf/1704.06996.pdf">calculation is horrendously complicated</a>. Explaining an aurora, for example, requires us to understand orbital mechanics, magnetic fields and atomic physics, but at heart, these are just more mathematics. </p>
<p>But it is when we think of the individual that we realize that a human commitment to logical, mathematical thinking goes much deeper. The decision to overtake a slow-moving car does not involve the explicit integration of the equations of motion, but we certainly do it implicitly. A Tesla on autopilot will actually solve them explicitly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="view from the cockpit of a tesla with another car ahead and the driver working on their devices" src="https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/456989/original/file-20220407-22-misq8y.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"></a>
<figcaption>
<span class="caption">When overtaking a car, a Tesla will explicitly calculate what a human driver processes implicitly.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Predicting chaos</h2>
<p>So we really should not be surprised that mathematics is not just a language for describing the external world, but in many ways the only one. But just because something can be described mathematically does not mean it can be predicted. </p>
<p>One of the more remarkable discoveries of the last 50 years has been the discovery of “<a href="https://www.stsci.edu/%7Elbradley/seminar/chaos.html">chaotic systems</a>.” These can be apparently simple mathematical systems that cannot be solved precisely. It turns out that many systems are chaotic in this sense. Hurricane tracks in the Caribbean are superficially similar to eclipse tracks, but we cannot predict them precisely with all the power of modern computers. </p>
<p>However, we understand why: the equations that describe weather are intrinsically chaotic, so we can make accurate predictions in the short term, (about 24 hours), but these become increasingly unreliable over days. Similarly, quantum mechanics provides a theory where we know precisely what predictions cannot be made precisely. One can calculate the properties of an electron very accurately, but we cannot predict what an <a href="https://doi.org/10.1038/d41586-018-05892-6">individual one will do</a>.</p>
<p>Hurricanes are obviously intermittent events, and we cannot predict when one will happen in advance. But the mere fact that we cannot predict an event precisely does not mean we cannot describe it when it happens. We can even handle one-off events: it is generally accepted that the universe was created in the Big Bang and we have a remarkably <a href="https://www.nationalgeographic.com/science/article/origins-of-the-universe">precise theory of that</a>.</p>
<h2>Designing social systems</h2>
<p>A whole host of social phenomena, from the <a href="https://www.science.org/content/article/stock-market-using-mathematics-finance">stock market</a> to <a href="https://uwspace.uwaterloo.ca/handle/10012/10627">revolutions</a>, lack good predictive mathematics, but we can describe what has happened and to some extent construct model systems. </p>
<p>So how about personal relationships? Love may be blind, but relationships are certainly predictable. The vast majority of us choose partners inside our social class and linguistic group, so there is absolutely no doubt that is true in the statistical sense. But it is also true in the local sense. A host of dating sites make their money by algorithms that at least make some pretence at matching you to your ideal mate. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/d6wG_sAdP0U?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In a TED talk, futurist Amy Webb shows that mathematics actually works in dating algorithms.</span></figcaption>
</figure>
<p>A universe that could not be described mathematically would need to be fundamentally irrational and not merely unpredictable. Just because a theory is implausible does not mean we could not describe it mathematically. </p>
<p>But I do not think we live in that universe, and I suspect we cannot imagine a non-mathematical universe.</p><img src="https://counter.theconversation.com/content/175813/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Watson received funding from NSERC.</span></em></p>
In the absence of mathematical explanations, the universe would be irrational rather than unpredictable.
Peter Watson, Emeritus professor, Physics, Carleton University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/163167
2021-07-01T19:52:43Z
2021-07-01T19:52:43Z
The scientific genius who eschewed fame: remembering Thomas Harriot, 400 years on
<figure><img src="https://images.theconversation.com/files/409214/original/file-20210701-21065-1n6x87b.JPG?ixlib=rb-1.1.0&rect=3%2C0%2C2584%2C3237&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Harriot_at_Syon_Park.JPG">Rita Greer</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span></figcaption></figure><p>Four hundred years ago, on July 2 1621, a remarkable Englishman named Thomas Harriot died in London. He left behind some 8,000 pages of scientific research, but it is only in recent decades that scholars have uncovered their treasures. </p>
<p>And what they show is that Harriot independently made many significant discoveries now attributed to other, more famous scientists. Some scholars have called him “the English Galileo” and “the greatest British mathematical scientist before Newton”. </p>
<p>Yet Harriot died without publishing a single word of this extraordinary output. His tale reminds us that, while we may sometimes think science progresses through a series of famous pioneers who single-handedly overturn entrenched beliefs, the story is rarely so simple.</p>
<h2>What did Harriot discover?</h2>
<p>For instance, we learn in school that Galileo Galilei initiated telescopic astronomy and discovered the law of falling motion. But Harriot independently did both of these things. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pen and ink drawing of the surface of the Moon." src="https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=585&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=585&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=585&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=735&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=735&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409209/original/file-20210701-21056-104m7cb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=735&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Thomas Harriot’s 1609 map of the Moon, drawn by observing through a telescope.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Thomas_Harriot#/media/File:Harriot_Lunar_Map.jpg">Wikimedia</a></span>
</figcaption>
</figure>
<p>He also deduced fledgling general laws governing the motion of everyday objects, again independently of Galileo, and before René Descartes. (Half a century later, Isaac Newton developed the definitive laws of motion.)</p>
<p>Harriot studied light, too, discovering the secret of colour and the nature of the rainbow before Newton, and finding the law of refraction (which we know today as Snell’s law) before the Dutch astronomer Willebrord Snell.</p>
<p>He also made a mathematical study of population growth before Thomas Malthus, developed a <a href="https://www.ems-ph.org/books/book.php?proj_nr=94&srch=series%7Chem">completely symbolic</a> form of sophisticated <a href="https://www.springer.com/gp/book/9780387495118">algebra</a> before Descartes, discovered binary arithmetic before Gottfried Leibniz, and took
steps on the road to calculus with his work on infinite series. </p>
<h2>The law of falling bodies</h2>
<p>It wasn’t until 2008 that Harriot’s work on gravity was <a href="https://www.springer.com/gp/book/9781402054983">fully reconstructed</a>, by the German scholar Matthias Schemmel. </p>
<p>As Schemmel pointed out, Harriot and his contemporary Galileo were heirs to essentially the same body of knowledge. It’s perhaps not so surprising, then, that they made some of the same breakthroughs. There are plenty of examples of independent co-discoveries in history, most famously that of calculus by Newton and Leibniz.</p>
<p>The law of falling motion says that without air resistance all objects, no matter their size or mass, fall from the same height at the same rate. </p>
<p>Legend has it Galileo dropped balls from the Leaning Tower of Pisa to study how they fell. Nobody knows if this is true, but Harriot had the same idea: he recorded the time, in pulse beats, that it took for different objects falling from as high as 55½ feet (about 17 metres) to reach the ground. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/copernicus-revolution-and-galileos-vision-our-changing-view-of-the-universe-in-pictures-60103">Copernicus' revolution and Galileo's vision: our changing view of the universe in pictures</a>
</strong>
</em>
</p>
<hr>
<p>Both Harriot and Galileo devised more accurate experiments, however, from which they derived a mathematical understanding of how things fall. </p>
<p>This combination of experiment and mathematics is now the accepted way to derive a law of nature. Quantifying observations means others can test the results, and use them to make useful predictions. </p>
<p>Harriot and Galileo were not the first to understand the role of observation and mathematics in this context, of course. But they were among the most successful of the pre-Newtonian pioneers.</p>
<p>Galileo didn’t publish his work on gravity until after Harriot had died, and there’s no evidence that the two men ever met or corresponded.</p>
<h2>The law of refraction and the shape of the rainbow</h2>
<p>The German astronomer Johannes Kepler, however, did correspond briefly with Harriot. Kepler had been working on the nature of light and vision when word reached him that Harriot had unravelled two mysteries: the law of refraction, and why the rainbow has its magical colours and its unique shape.</p>
<p>The law of refraction describes how light bends when it passes from one medium into another, which explains how an image can be focused by a glass lens or why your leg looks wobbly when you dip it in a swimming pool. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=864&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=864&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=864&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1086&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1086&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409217/original/file-20210701-21135-wg5m9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1086&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 diagram from Ibn Sahl’s 10th-century treatise on optics showing the path of light refracted by a lens.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Ibn_Sahl_manuscript.jpg">Wikimedia</a></span>
</figcaption>
</figure>
<p>Harriot derived this law 20 years before Snell, but there’s a popular belief that the 10th-century Baghdad-based scholar Abū Saʿd al-ʿAlāʾ ibn Sahl beat even Harriot. This is not quite right: Ibn Sahl is a notable pioneer whose geometrical diagram of light focussed by a lens gives, in hindsight, the correct refractive path. But there’s no evidence he deduced his result from experiment, or that he understood the general properties of refraction.</p>
<p>Judging from his surviving papers even Snell failed to generalise his result, which he, like Ibn Sahl, never wrote as the neat trigonometric equation we use today. Harriot, by contrast, did: his derivation of the general law of refraction is another example of his rigorous blend of experiment and mathematics.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-rainbows-round-81187">Curious Kids: Why are rainbows round?</a>
</strong>
</em>
</p>
<hr>
<h2>Harriot’s other adventures</h2>
<p>If only Harriot had published! In the early stage of his career, though, he was bound by commercial secrecy, for his first patron was the controversial statesman and entrepreneur Sir Walter Raleigh. Harriot was also busy dodging heretic hunters and sailing the high seas as Raleigh’s navigational advisor. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A heavily decorated title page reading 'A briefe and true report of the new found land of Virginia'." src="https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=805&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=805&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=805&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1011&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1011&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409210/original/file-20210701-21296-xaa1cu.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1011&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Thomas Harriot published only one work in his lifetime: a report on his stay in North America in the 1580s.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:English_title_page,_A_Briefe_and_True_Report_of_the_Newfound_Land_of_Virginia.JPG">Wikimedia</a></span>
</figcaption>
</figure>
<p>Raleigh had delusions of empire and glory, and wanted to establish a trading colony in today’s USA before the Spanish beat him to it. The one work Harriot did publish in his lifetime was “a brief and true report” on the economic potential of Raleigh’s chosen American site.</p>
<p>Harriot’s contribution to colonialism has justly attracted its share of criticism. Nonetheless, his report is still widely praised for its sympathetic depiction of the way of life of the North Carolina Algonquian people, as it was when Europeans first set foot on their land. Harriot learned the local language, and enjoyed much about the year he spent living with the Algonquians.</p>
<p>What he loved doing most, though, was mathematics and physics. He was neither flamboyant nor ambitious, and when he was wrongfully imprisoned through an unlucky connection with the Gunpowder Plot (a failed attempt to assassinate King James I), he told his jailers he just wanted</p>
<blockquote>
<p>to live a private life for the love of learning that I might study freely. </p>
</blockquote>
<h2>Conclusion</h2>
<p>In the late 1590s Harriot had found a second patron, Henry Percy, the ninth earl of Northumberland. It was then that he was able to study the mysteries of nature and the marvels of mathematics for their own sakes, rather than the “applied” work he had done for Raleigh.</p>
<p>Having two generous patrons meant Harriot did not need to publicise his discoveries to attract funding, the way Galileo did. Nor did he care about fame, despite being urged by friends to claim his priority. His manuscripts do contain several almost finished treatises, but it seems he was so busy doing science that he never managed to put his results together for the printer.</p>
<p>After his death, well-meaning scholars carved up his manuscripts in an attempt to study and publish them. In the process, however, all the papers disappeared, seemingly lost forever. Then, 150 years later, the Hungarian astronomer Franz Xaver Zach discovered them, locked safely away in Northumberland’s castle.</p>
<p>Most of the papers were then given to the British Museum. They are now in the British Library, where I had the privilege of studying them. (They’re also available <a href="https://echo.mpiwg-berlin.mpg.de/content/scientific_revolution/harriot">online</a>.)</p>
<p>As for Harriot, no-one knows much about him as a person – not even his birthday. Nevertheless, he has fascinated scholars for the past half century (as I discovered some years ago when I set out to bring his story to a <a href="https://global.oup.com/academic/product/thomas-harriot-9780190271855?cc=us&lang=en&#">wider, non-specialist</a> readership). </p>
<p>That’s because despite the lack of biographical data, those precious manuscripts show that what mattered most to Harriot himself was mathematics and science. Four hundred years on, his mix of genius and dedication is something to honour.</p><img src="https://counter.theconversation.com/content/163167/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robyn Arianrhod 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 English astronomer and navigator Thomas Harriot died in 1621, leaving behind 8,000 pages of notes containing a trove of unpublished scientific discoveries.
Robyn Arianrhod, Affiliate, School of Mathematics, Monash University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/156773
2021-03-25T16:59:34Z
2021-03-25T16:59:34Z
Doctors only started measuring body temperature 200 years ago – here’s why
<figure><img src="https://images.theconversation.com/files/389818/original/file-20210316-20-19zgb9o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/04HE-456KIg">Dony Wardhana/Unsplash</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span></figcaption></figure><p>Over the past year, fever thermometers have become omnipresent. Body temperature is taken in front of shops, at airports, even before visiting a museum – often with ultra-modern devices. So-called fever cameras or fever scanners can determine the body temperature even without contact. It might now seem obvious that fevers are connected to a high body temperature – in many cultures, the question “do you have a temperature?” is clear evidence of that – but this hasn’t always been the case. </p>
<figure class="align-left ">
<img alt="Black and white historic portrait of a bearded man." src="https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=889&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=889&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=889&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1117&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1117&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389820/original/file-20210316-14-6xvzx4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1117&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sanctorio Sanctorius, 1609.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Sanctorius.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>The beginnings of measuring fever go back more than 400 years. At the turn of the 17th century, several scholars dealt with the development of thermometers. In London, Robert Fludd worked on an instrument to measure temperature. On the Italian peninsula, Galileo Galilei and his close friend Giovanni Francesco Sagredo were engaged in the same activity. So it cannot be clearly determined <a href="https://www.springer.com/de/book/9789048186440">who invented the thermometer</a>. </p>
<p><a href="https://www.jstor.org/stable/10.1086/667970?seq=1#metadata_info_tab_contents">But historians agree</a> that a particular member of Galileo’s Venetian circle of friends was the first to apply the instrument to medicine. This was the Venetian physician <a href="https://www.mpiwg-berlin.mpg.de/research/projects/emergence-iatromechanical-medicine">Sanctorio Sanctorius (1561 – 1636)</a>, who developed the first fever thermometers to determine his patients’ body heat. </p>
<p>This was a novelty. While today we trust in numbers and measurements, especially regarding medical issues, in Sanctorius’ times it was not thought that phenomena like health or disease could be recorded by numbers, let alone be measured. Rather, people relied on the experience of their physicians. Through regularly touching the foreheads of their patients, they gauged what kind and how bad the fever was.</p>
<h2>The first body thermometer</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Black and white illustration of a historic thermometer." src="https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1463&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1463&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1463&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1838&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1838&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390438/original/file-20210318-23-1cb4hk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1838&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An illustration of Sanctorius’ thermoscope (on the right), a thermometer without a scale, 1626.</span>
<span class="attribution"><a class="source" href="https://wellcomecollection.org/works/c8vwha2p/items?langCode=false&canvas=1">© Wellcome Collection</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Sanctorius’ measurement and notion of fever did not tally with modern understandings. The Venetian physician made use of the thermal expansion of air in his thermometers, rather than liquids, which is what tends to be used in today’s traditional fever thermometers. </p>
<p>Since air does not expand and contract only due to changes in temperature, but also in atmospheric pressure, Sanctorius’ unsealed thermometers were sensitive to both. Therefore, any measurement of body heat with an instrument of Sanctorius’ type would be distorted by the influence of atmospheric pressure. This was realised a short time later. To avoid its influence, in later thermometers, air was replaced with a liquid sealed in a glass tube.</p>
<p>Sanctorius seems to have used his non-sealed air thermometers anyway. Galileo and Sagredo, who worked with similar types of thermometers outside of a medical context, realised that there were irregularities, but the phenomenon of atmospheric pressure and its effect was still unknown to them. From today’s perspective, such thermometers might seem not very helpful, but at the time these were the first instruments that could be used to obtain information about degrees of hot and cold without appealing to the human senses.</p>
<p>And although Sanctorius used the Latin term <em>temperamentum</em>, <a href="https://brill.com/view/book/edcoll/9789047442318/Bej.9789004170506.i-582_005.xml">his concept of a “temperature”</a> was very different from today’s. He adhered to the medical theory of the four humours, which assumed that human health depended on a balanced proportion of the four humours: blood, phlegm, yellow, and black bile. These humours were assigned to so-called primary qualities: hot, cold, moist and dry. Here, too, balance was crucial: if one of the primary qualities was too strong or too weak, it could cause diseases.</p>
<figure class="align-left ">
<img alt="Diagram illustrating the associations of the four humours." src="https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=756&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=756&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389822/original/file-20210316-17-1w5vryx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=756&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Diagram illustrating the four humours.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Humorism.svg">Tom Lemmens</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>So when Sanctorius used his fever thermometers, what he was trying to measure was certain degrees of hot and cold in his patients’ complexions, which he believed would reveal their individual mixtures of the four humours. In doing so, he wanted to determine “the quantity of diseases”, by which he meant the deviation of the body from its balanced, healthy state.</p>
<p>For a long time, the “quantity” of heat was considered to be only <a href="https://jhupbooks.press.jhu.edu/title/more-hot">one of several parameters</a> that allowed the physician to differentiate between healthy body heat and <a href="https://www.cambridge.org/core/journals/medical-history/article/fever-pathology-in-the-sixteenth-century-tradition-and-innovation/652A82CDFDB5FAD191D5E0C969FCA632">febrile heat</a>. The latter was also characterised by qualitative aspects and could, for example, be “sharp” or “biting”. Not only the degree of heat was important but also its kind. What’s more, besides body heat, the pulse, respiration, the skin, and urine were all thought to indicate a fever’s character.</p>
<h2>Thermometers in use</h2>
<p>And so although the diagnosis and treatment of fever was a central preoccupation of the physicians of the Renaissance, Sanctorius’ thermometers did not find considerable application in daily medical practice because heightened temperature simply wasn’t considered the main determinant of a fever. To physicians at the time, the measurement of body heat was of secondary interest.</p>
<p>It was <a href="https://www.faz.net/aktuell/feuilleton/buecher/rezension-sachbuch-die-skala-des-fortschritts-11305207.html">only in the 19th century</a> that the fever thermometer came into general clinical use and found its way into the household. Today, fever is defined as elevated body temperature and seen as a symptom that can occur in different diseases.</p>
<figure class="align-center ">
<img alt="Thermometer with red liquid interior on a neutral background." src="https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390358/original/file-20210318-13-b5wwks.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">A modern liquid thermometer, which works by the change in volume of a thermometric fluid, mostly coloured alcohol.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/glass-alcohol-thermometer-degrees-celsius-measuring-1608223156">MZinchenko/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>As different as Sanctorius’ thermometers and his notions of fever are to our modern devices and our understanding of increased body temperature, they still give an important insight into the long path that preceded our modern fever measuring devices – devices that are icons of the current pandemic like hardly any others.</p><img src="https://counter.theconversation.com/content/156773/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Teresa Hollerbach 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 beginnings of measuring fever go back more than 400 years.
Teresa Hollerbach, Research Scholar, Max Planck Institute for the History of Science
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/128818
2020-01-24T13:39:36Z
2020-01-24T13:39:36Z
Why your zodiac sign is probably wrong
<figure><img src="https://images.theconversation.com/files/309355/original/file-20200109-80169-1wreuwe.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1991%2C1476&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As the Earth orbits the Sun, the Sun appears to move through the ancient constellations of the zodiac.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ecliptic_path.jpg">Tauʻolunga/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>I was born a Capricorn (please don’t judge me), but the Sun was in the middle of Sagittarius when I was born. </p>
<p>As a <a href="http://stars.astro.illinois.edu/">professor emeritus of astronomy</a>, I am often asked about the difference between astrology and astronomy. The practice of astrology, which predicts one’s fate and fortune based on the positions of the Sun, Moon, stars and planets, dates back to ancient times. It was intermingled with the science of astronomy back then – in fact, many astronomers of old made scientific observations that are valuable even today. But once Copernicus, Kepler and Galileo realized the planets orbit the Sun, rather than the Earth, and Newton discovered the physical laws behind their behavior, astrology and astronomy split, never to be reunited. </p>
<p>The science of astronomy is now at odds with one of the basic organizing principles in astrology – the dates of the zodiac.</p>
<h2>The constellations of the zodiac</h2>
<p>Over the course of a year, the Sun appears to pass through a belt of sky containing 12 ancient constellations, or groupings, of stars. They are collectively called the zodiac and consist almost entirely of animal figures, like the ram (Aries), crab (Cancer) and lion (Leo). It is a disappointment to many that the constellations only rarely look like what they represent. How could they, since they are truly random scatterings of stars? They are meant to represent, not to portray.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=509&fit=crop&dpr=1 600w, https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=509&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=509&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=640&fit=crop&dpr=1 754w, https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=640&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/309733/original/file-20200113-103974-7f1x7p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=640&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The word ‘zodiac’ comes from a Greek phrase that means ‘circle of animals’.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/zodiac-constellations-zodiacal-calendar-dates-astrological-1562183209">Tartila/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Although the constellations of the zodiac, which date back to Mesopotamia or before, may seem definitive, they are only one example of those produced by the various cultures of the world, all of which had their own, frequently very different, notions of how the sky is constructed. The Incas, for example, made constellations not from stars, but from the <a href="https://www.thoughtco.com/inca-star-worship-and-constellations-2136315">dark patches in the Milky Way</a>. </p>
<p>The number of constellations in the Western zodiac comes from the cycles of the Moon, which orbits the Earth 12.4 times a year. Roughly speaking, the Sun appears against a different constellation every new Moon, the stars forming a distant backdrop to the Sun. Though the stars are not visible during daytime, you can know what constellation the Sun is in by looking at the nighttime sky. There you will see the opposite constellation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=435&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=435&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310567/original/file-20200116-181617-c3nx4x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=435&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 Sun is in Leo here, which means at night, you’d see Aquarius.</span>
<span class="attribution"><a class="source" href="https://www.pngguru.com/free-transparent-background-png-clipart-gmeeu">PNGGuru</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Astrology suggests that each sign of the zodiac fits neatly into a 30-degree slice of sky – which multiplied by 12 adds up to 360 degrees. In actuality, this is not the case, as the constellations vary a great deal in shape and size. For example, the Sun passes through the constellation Scorpio in just five days, but takes 38 days to pass through Taurus. This is one of the reasons astrological signs do not line up with the constellations of the zodiac.</p>
<h2>Precession of the equinoxes</h2>
<p>The main reason astrological signs fail to line up with the zodiac, though, is a wobble in the Earth’s rotational axis called <a href="https://www.britannica.com/science/precession">precession</a>. As a result of its rotation, the Earth bulges slightly at the equator, not unlike how a skater’s skirt fans out as she spins. The gravity of the Moon and Sun pull on the bulge, which causes the Earth to wobble like a top. The wobble causes the Earth’s axis, which is the center line around which it rotates, to swing in a slow circle over the course of 25,800 years.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qlVgEoZDjok?wmode=transparent&start=39" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A wobbling Earth causes the dates of the zodiac to shift from those established in ancient times.</span></figcaption>
</figure>
<p>This movement alters the view of the zodiac from Earth, making the constellations appear to slide to the east, roughly a degree per human lifetime. Though slow, precession was discovered with the naked eye by <a href="http://abyss.uoregon.edu/%7Ejs/glossary/hipparchus.html">Hipparchus of Nicaea</a> around 150 B.C.</p>
<p>In ancient times, the vernal equinox – or the first day of spring – was in Aries. Due to precession, it moved into Pisces <a href="http://stars.astro.illinois.edu/books.html#sky">around 100 B.C., where it is now and will remain until A.D. 2700</a>, when it will move into Aquarius and so on. Over the course of 25,800 years, it will eventually return to Aries and the cycle will begin again.</p>
<p><iframe id="x0CHI" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/x0CHI/3/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>As a game, astrology and its predictions of fate and personality can be fun. However the subject has no basis in science. It is to science what the game “Monopoly” is to the real estate market. </p>
<p>Astrology diverts attention away from the very real influences of the planets, primarily their gravitational effects on one another that cause real changes in the shapes, sizes and tilts of their orbits. On Earth, <a href="https://doi.org/10.1038/nature07867">such changes likely caused past ice ages</a>. Direct collisions between Earth and celestial bodies can cause very rapid changes, such as the impact of an asteroid off the Yucatan Peninsula <a href="https://www.smithsonianmag.com/science-nature/dinosaur-killing-asteroid-impact-chicxulub-crater-timeline-destruction-180973075/">66 million years ago that had global effects</a> including the disappearance of dinosaurs and the rise of mammals.</p>
<p>Astronomical studies will eventually allow the prediction of such events, while astrological predictions will get you absolutely nowhere.</p>
<hr>
<p><em>This story has been updated to correct the animal that Aries represents. The chart has been updated to include Oct. 31 under Virgo, where it falls most years.</em></p><img src="https://counter.theconversation.com/content/128818/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James B. Kaler 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>
Astronomy and astrology do not agree on the dates of the zodiac constellations.
James B. Kaler, Professor Emeritus of Astronomy, University of Illinois at Urbana-Champaign
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/120945
2019-08-14T12:32:30Z
2019-08-14T12:32:30Z
A brief astronomical history of Saturn’s amazing rings
<figure><img src="https://images.theconversation.com/files/287419/original/file-20190808-144892-1u8fsji.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">With giant Saturn hanging in the blackness and sheltering Cassini from the Sun's blinding glare, the spacecraft viewed the rings as never before.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/multimedia/imagegallery/image_feature_1202.html">NASA/JPL/Space Science Institute</a></span></figcaption></figure><p>Many dream of what they would do had they a time machine. Some would travel 100 million years back in time, when dinosaurs roamed the Earth. Not many, though, would think of taking a telescope with them, and if, having done so, observe Saturn and its rings.</p>
<p>Whether our time-traveling astronomer would be able to observe Saturn’s rings is debatable. Have the rings, in some shape or form, existed since the beginnings of the solar system, 4.6 billion years ago, or are they a more recent addition? Had the rings even formed when the <a href="https://theconversation.com/more-bad-news-for-dinosaurs-chicxulub-meteorite-impact-triggered-global-volcanic-eruptions-on-the-ocean-floor-91053">Chicxulub asteroid</a> wiped out the dinosaurs?</p>
<p><a href="https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1063926">I am a space scientist</a> with a passion for teaching physics and astronomy, and Saturn’s rings have always fascinated me as they tell the story of how the eyes of humanity were opened to the wonders of our solar system and the cosmos.</p>
<h2>Our view of Saturn evolves</h2>
<p>When Galileo first observed Saturn through his telescope in 1610, he was still basking in the fame of <a href="https://www.forbes.com/sites/briankoberlein/2016/01/07/galileos-discovery-of-jupiters-moons-and-how-it-changed-the-world/#dd6cc0f46f07">discovering the four moons of Jupiter</a>. But Saturn perplexed him. Peering at the planet through his telescope, it first looked to him as a planet with two very large moons, then as a lone planet, and then again through his newer telescope, in 1616, as a planet with arms or handles.</p>
<p>Four decades later, <a href="https://www.britannica.com/biography/Christiaan-Huygens">Christiaan Huygens</a> first suggested that Saturn was a ringed planet, and what Galileo had seen were different views of Saturn’s rings. Because of the 27 degrees in the tilt of Saturn’s rotation axis relative to the plane of its orbit, the rings appear to tilt toward and away from Earth with the 29-year cycle of Saturn’s revolution about the Sun, giving humanity an ever-changing view of the rings.</p>
<p>But what were the rings made of? Were they solid disks as some suggested? Or were they made up of smaller particles? As more structure became apparent in the rings, as more gaps were found, and as the motion of the rings about Saturn was observed, astronomers realized that the rings were not solid, and were perhaps made up of a large number of moonlets, or small moons. At the same time, estimates for the thickness of the rings went from Sir William Herschel’s 300 miles in 1789, to Audouin Dollfus’ much more precise <a href="http://solarviews.com/eng/saturnbg.htm">estimate of less than two miles</a> in 1966. </p>
<p>Astronomers understanding of the rings changed dramatically with the <a href="https://solarsystem.nasa.gov/missions/pioneer-11/in-depth/">Pioneer 11</a> and twin Voyager missions to Saturn. <a href="https://voyager.jpl.nasa.gov/assets/images/galleries/images-voyager-took/saturn/6bg.jpg">Voyager’s now famous photograph of the rings</a>, backlit by the Sun, showed for the first time that what appeared as the vast A, B and C rings in fact comprised millions of smaller ringlets. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287555/original/file-20190809-144868-1oi82mi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Voyager 2 false color image of Saturn’s B and C rings showing many ringlets.</span>
<span class="attribution"><a class="source" href="https://voyager.jpl.nasa.gov/assets/images/galleries/images-voyager-took/saturn/6bg.jpg">NASA</a></span>
</figcaption>
</figure>
<p>The Cassini mission to Saturn, having spent over a decade orbiting the ringed giant, gave planetary scientists even more spectacular and surprising views. The magnificent ring system of Saturn is between 10 meters and one kilometer thick. The combined mass of its particles, which are 99.8% ice and most of which are less than one meter in size, is about 16 quadrillion tons, less than 0.02% the mass of Earth’s Moon, and less than half the mass of Saturn’s moon <a href="https://doi.org/10.1126/science.aat2965">Mimas</a>. This has led some scientists to speculate whether the rings are a result of the breakup of one of Saturn’s moons or the capture and breakup of a stray comet. </p>
<h2>The dynamic rings</h2>
<p>In the four centuries since the invention of the telescope, rings have also been discovered around <a href="https://doi.org/10.1007/978-0-387-73981-6_4">Jupiter</a>, <a href="https://www.universetoday.com/19288/uranus-rings/">Uranus</a> and <a href="https://www.universetoday.com/21635/rings-of-neptune/">Neptune</a>, the giant planets of our solar system. The reason why the giant planets are adorned with rings and Earth and the other rocky planets are not was first proposed by Eduard Roche, a French astronomer in 1849. </p>
<p>A moon and its planet are always in a gravitational dance. Earth’s moon, by pulling on opposite sides of the Earth, causes the ocean tides. Tidal forces also affect planetary moons. If a moon ventures too close to a planet, these forces can overcome the gravitational “glue” holding the moon together and tear it apart.
This causes the moon to break up and spread along its original orbit, forming a ring. </p>
<p>The <a href="https://www.britannica.com/science/Roche-limit">Roche limit</a>, the minimum safe distance for a moon’s orbit, is approximately 2.5 times the planet’s radius from the planet’s center. For enormous Saturn, this is a distance of 87,000 kilometers above its cloud tops and matches the location of Saturn’s outer F ring. For Earth, this distance is less than 10,000 kilometers above its surface. An asteroid or comet would have to venture very close to the Earth to be torn apart by tidal forces and form a ring around the Earth. Our own Moon is a very safe 380,000 kilometers away.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=253&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=253&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=253&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=318&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=318&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287560/original/file-20190809-144873-yojp3b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=318&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">NASA’s Cassini spacecraft about to make one of its dives between Saturn and its innermost rings as part of the mission’s grand finale.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/illustration-of-cassini-spacecrafts-grand-finale-dive">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<p>The thinness of planetary rings is caused by their ever-changing nature. A ring particle whose orbit is tilted with respect to the rest of the ring will eventually collide with other ring particles. In doing so, it will lose energy and settle into the plane of the ring. Over millions of years, all such errant particles either fall away or get in line, leaving only the very thin ring system people observe today.</p>
<p>During the last year of its mission, the Cassini spacecraft dived repeatedly through the 7,000 kilometer gap between the clouds of Saturn and its inner rings. These unprecedented observations made one fact very clear: <a href="https://doi.org/10.1126/science.aat3760">The rings are constantly changing</a>. Individual particles in the rings are continually jostled by each other. Ring particles are steadily raining down onto Saturn.</p>
<p>The shepherd moons Pan, Daphnis, Atlas, Pandora and Prometheus, measuring between eight and 130 kilometers across, quite literally shepherd the ring particles, <a href="https://doi.org/10.1126/science.aat2349">keeping them in their present orbits</a>. Density waves, caused by the motion of shepherd moons within the rings, jostle and reshape the rings. Small moonlets are forming from ring particles that coalesce together. All this indicates that the rings are ephemeral. Every second <a href="https://doi.org/10.1126/science.aat2382">up to 40 tons of ice from the rings</a> rain down on Saturn’s atmosphere. That means the rings may last only several tens to hundreds of millions of years. </p>
<p>Could a time-traveling astronomer have seen the rings 100 million years ago? One indicator for the age of the rings is their dustiness. Objects exposed to the dust permeating our solar system for long periods of time grow dustier and darker. </p>
<p>Saturn’s rings are extremely bright and dust-free, seeming to indicate that they <a href="https://www.scientificamerican.com/article/how-old-are-saturns-rings-the-debate-rages-on/">formed anywhere from 10 to 100 million years ago</a>, if astronomers’ understanding of how icy particles gather dust is correct. One thing is for certain. The rings our time-traveling astronaut would have seen would have looked very different from the way they do today. </p>
<p><em>This story has been corrected to reflect that it was Christiaan Huygens, not Giovanni Cassini, who first suggested that Saturn had rings.</em></p>
<p>[ <em>Like what you’ve read? Want more?</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=likethis">Sign up for The Conversation’s daily newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/120945/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vahe Peroomian 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>
Although the rings of Saturn may look like a permanent fixture of the planet, they are ever-changing. New analyses of the rings reveal how and when they were made, from what and whether they’ll last.
Vahe Peroomian, Associate Professor of Physics and Astronomy, USC Dornsife College of Letters, Arts and Sciences
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/102272
2018-08-29T16:36:07Z
2018-08-29T16:36:07Z
Anish Kapoor’s “Cloud Gate”: playing with light and returning to Earth, our finite world
<figure><img src="https://images.theconversation.com/files/233825/original/file-20180828-75993-1hc8e30.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C1488%2C750&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Anish Kapoor, _Cloud Gate_, 2004. Stainless steel, 1,006 x 2,012 x 1,280 cm.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/--mike--/6143335396/">Mike Warot/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Every day thousands of people play with Anish Kapoor’s <a href="http://anishkapoor.com/210/cloud-gate"><em>Cloud Gate</em></a> in Chicago’s Millennium Park. Affectionately nicknamed “the bean” for obvious reasons, the immense mirrored sculpture is made up of 168 stainless steel plates welded together and placed on the ground. It’s about 10 meters tall, with a base of about 20 by 13 meters. That’s what it takes – smaller is not possible. Such an impressive size is needed for the sculpture to impose itself in the Millennium Park and to achieve the ambition of the project, to play with the light and mix all the reflections of Chicago and its environment, day and night.</p>
<p>It’s striking: the city of Chicago is the right place for <em>Cloud Gate</em>, with a very simple surrounding geography. On one side is the Midwest, the flat American plain over seemingly infinite distances. Unlike France, where the landscape can change completely within just a few kilometres, in the Midwest, you can drive for hours and nothing will change. On the other side of <em>Cloud Gate</em> is Lake Michigan, its surface equivalent to 10% of the area of France. Water goes to the horizon on one side and endless cornfields are on the other. In this flat world, the city’s skyscrapers point to the sky. More than 100 culminate at more than 150 meters, with 442 meters for the highest. At night, it’s just magical.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/GBHrpd26JIw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p><em>Cloud Gate</em> is in Millennium Park, between downtown Chicago and Lake Michigan. Depending on the position you take, <em>Cloud Gate</em> is the mirror you choose for yourself. You can mix the elements as you wish: the sky, the city, the space above the lake and, and of course, the skyscrapers. It is gorgeous night or day, when weather is good and when it is not. You can be in the image you construct or not. If you want, you can even walk underneath to hide everything. Thousands of photos on the Web show all the possibilities.</p>
<h2>Geometric optics, rules the game with light</h2>
<p>Mirrors and lenses are two pillars of geometric optics, the basic tools for changing the direction of light rays. <em>Transmission</em>, <em>reflection</em> and <em>refraction</em> are the associated words. What we want to look at and how we observe determine how we build and assemble these optical elements. Professionals of this game are astronomers and microscopists. Anish Kapoor does the very same thing with <em>Cloud Gate</em>. But anyone who plays with light does not do so without consequences. Light brings into our eyes pictorial information about the world at the speed… of light. Having this information, seeing it, determines our lives. Nothing less.</p>
<p>Mirrors and lenses allow us to see at different scales: from the infinitely large with the <a href="http://hubblesite.org/">Hubble Space Telescope</a> to the invisibly small all around us with optical microscopes. Imaging at different scales has always been one of the major issues in science. Anish Kapoor approached sculpture with this idea, so he ended up building curved mirrors. This is no surprise for a physicist, but what Kapoor does with it artistically is amazing. Say why with a physicist’s eyes is the subject of this article.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=839&fit=crop&dpr=1 600w, https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=839&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=839&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1054&fit=crop&dpr=1 754w, https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1054&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/228084/original/file-20180717-44103-k75w16.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1054&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Moon phases drawn by Galileo in 1616. (Wikimedia).</span>
</figcaption>
</figure>
<h2>Galileo’s telescope changes the view of the universe</h2>
<p>The most famous example of this game, in which one looks beyond the visible with an optical instrument, is the observation of the surface of the Moon with a telescope by Galileo in 1609. Two references help to situate the importance of the event. First of all, in the 1610 treatise <a href="https://en.wikipedia.org/wiki/Sidereus_Nuncius">“Sidereus Nuncius”</a> (Messenger of the Stars), Galileo makes it evident at the very first page:</p>
<blockquote>
<p>“Great, certainly, are the subjects that in this thin treatise I propose to each of those who observe Nature, so that they examine and contemplate them. Great, I say, first because of the importance of matter itself, then because of its unprecedented novelty over the centuries, finally, also because of the Instrument through which these subjects have offered themselves to our perception.”</p>
</blockquote>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=725&fit=crop&dpr=1 600w, https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=725&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=725&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=911&fit=crop&dpr=1 754w, https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=911&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/228085/original/file-20180717-44079-1kwhkub.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=911&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Y’a quelqu’un ?</em> Painting by Pierre Rouillon 2013 (image with permission of artist).</span>
</figcaption>
</figure>
<p>As an experimental physicist, I particularly appreciate the capital I of the word <em>instrument</em>. As a teacher, I have always noted the phrase “are offered to our perception”. The result of the observation, in other words, is that any viewer in Galileo’s time, even one previously convinced that the Moon is an ideal celestial sphere, would see it like the Earth, “covered on all sides with enormous protuberances, deep hollows, and sinuosities”. Too late, you should not have looked… Believe what you may, but with one look at the Moon with a telescope, and it will immediately lose its status as the ideal sphere to become like the Earth itself. Your vision of the world and the universe will be irremediably transformed, as Galileo emphasised in his book.</p>
<p>The philosopher Hannah Arendt, in <a href="https://en.wikipedia.org/wiki/The_Human_Condition_(book)"><em>The Human Condition</em></a>, underlines the radical break that this Galileo experience introduces. For her, three events founded modernity: the discovery by Europeans of the New World, the Reformation and the invention of the astronomical telescope:</p>
<blockquote>
<p>“What Galileo did and what nobody had done before was to use the telescope in such a way that the secrets of the universe were delivered to human cognition ‘with the certainty of sense-perception’, that is, he put within the grasp of an earth-bound creature and its body-bound senses what had seemed forever beyond his reach, at best open to the uncertainties of speculation and imagination.”</p>
</blockquote>
<p>We do not play with light with impunity – it opens doors and transports us far away. Today, the images of the Hubble telescope show us the incredible diversity of deep space.</p>
<h2>With <em>Cloud Gate</em> of Anish Kapoor, a return to Earth</h2>
<p>In this context, which combines the technical capacity of observation and its overwhelming implications for our vision of our situation on Earth and in the universe, how can Anish Kapoor’s mirror sculpture be approached? In <a href="http://the-talks.com/interview/anish-kapoor/">“I have nothing to say”</a>, Anish Kapoor insists on the link between his mirrors and their place of installation, the space they open by deciphering the world around them.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/228086/original/file-20180717-44079-sdd6gs.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Cloud Gate</em> at night (Dave Wilson).</span>
</figcaption>
</figure>
<p>Chicago, with its elementary geography of an immense plain, lake and magnificent man-made urban landscape, is made for <em>Cloud Gate</em>. The sculpture, in a dialogue with the skyscrapers that create verticality in this flat space, is an instrument that allows everyone to play with light to propose all the mixtures, all the distortions, all the reconstructions of this landscape. It is a new scope, which, by distortion and dilatation, changes how we see us in the world. This sculpture processes the elements of the landscape around the viewer, and changes his or her perception. The Skyline is now in front of us. We are in immediate proximity with the massive buildings behind Michigan Avenue. This new kind of scale focuses our attention on what is immediately around us.</p>
<p>The contrast with Hannah Arendt’s analysis of Galileo’s observation of the Moon and its bezel is radical:</p>
<blockquote>
<p>“We always handle nature from a point in the universe outside the earth. Without actually standing where Archimedes wished to stand, still bound to the earth through the human condition, we have found a way to act on the earth and within terrestrial nature as though we dispose of it from outside, from the Archimedean point. And even at the risk of endangering the natural life process we expose the earth to universal, cosmic forces alien to nature’s household.”</p>
</blockquote>
<p>You don’t play with light without consequences…</p>
<p>We’re now back on Earth, but times have changed. With the exception of Elon Musk, perhaps, we all now know our planet is a finite one and the only one.</p>
<h2>Sculpting one’s environment</h2>
<p>In its simplicity, <em>Cloud Gate</em> is just a giant mirror, after all. Its curved shape provides all kinds of mirrors with different curves and viewing angles. This is how everyone builds their own image of Chicago. Unlike Galileo’s telescope, the viewer sets up his or her own presence, choosing a place and that of others during the construction of the image. For a moment, we all becomes sculptors of our own environment and its ephemeral representation. And one day I will have to write how the discovery of exoplanets is again changing everything… after an artist seizes it.</p><img src="https://counter.theconversation.com/content/102272/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joël Chevrier ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>
Anish Kapoor made “Cloud Gate”, a giant bean-shaped mirror in Chicago. Visitors play with the light in the city and its surroundings, where our future lays.
Joël Chevrier, Professeur de physique, Université Grenoble Alpes (UGA)
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/96495
2018-05-18T11:00:48Z
2018-05-18T11:00:48Z
Galileo row: Brexit will bar UK from EU sat-nav programme, but Britain could build its own
<figure><img src="https://images.theconversation.com/files/219197/original/file-20180516-155569-fu5hd2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.esa.int/spaceinimages/Images/2014/07/Galileo_satellite_in_orbit">ESA/P. Carril</a></span></figcaption></figure><p>How did satellites become political footballs? The UK government is considering <a href="http://www.bbc.co.uk/news/uk-politics-43891933">building its own satellite navigation</a> system after <a href="http://www.bbc.co.uk/news/science-environment-44116085">the EU announced</a> the UK wouldn’t be allowed full access to Galileo, the European equivalent of GPS, after Brexit. British-based firms will also be prevented from bidding for contracts to help build Galileo.</p>
<p>This isn’t just grandstanding. As well as general open location data, Galileo provides a more secure “Public Regulated Service” (PRS) for organisations such as the police, coastguard and customs officers. This includes sensitive information that cannot currently be shared with non-EU members. So to gain access to Galileo’s full service, the UK government would have to reach another difficult agreement with the EU on top of everything else it hopes to negotiate.</p>
<p>The UK is very keen to grow its space industry, and the sector already has much of the needed capability to develop a new global navigation satellite system (GNSS). So, if full UK participation in Galileo is no longer allowed after Brexit, a UK GNSS would both be feasible and provide a much-needed boost for the country’s space sector. But, of course, this will come with a significant cost for the UK government.</p>
<p>The average British person interacts with satellites approximately 30 times a day and this is set to increase tenfold <a href="http://www.montfort.london/attachments/articles/a10148_Seraphim%20Press%20Release%20(FINAL).pdf">over the next five years</a>. We all know how sat-nav geolocation services help us travel, but other aspects of the business world such as financial services also rely heavily on GNSS data. This is because the satellites contain <a href="https://www.gps.gov/applications/timing/">highly accurate clocks</a> that enable electronic sales transactions, stock market trading and ATMs.</p>
<p>Once it has left the EU, the UK won’t be entirely excluded from access to Galileo services, just as it can access data from the US’s GPS system. But the reason Galileo was built in the first place was to provide a reliable, secure alternative that European governments had some control over. </p>
<p>There have been times when GPS has failed or has been closed to outside countries. For example, the service <a href="https://www.theatlantic.com/technology/archive/2016/06/what-happens-if-gps-fails/486824">briefly failed</a> in 2015 due to the upload of an incorrect time, and the impact was felt globally on emergency services, digital radio and even electrical grids. The US also denied GPS access to India during the 1999 Kargil War <a href="https://timesofindia.indiatimes.com/home/science/How-Kargil-spurred-India-to-design-own-GPS/articleshow/33254691.cms">for military reasons</a> and, in theory, could do so again to other countries.</p>
<p>So a dedicated British GNSS would give the UK government guaranteed secure access to a satellite service over which they had full control. It would also avoid the need to negotiate privileged access to Galileo’s special PRS signal for security services, which other non-EU European countries such as Norway and Switzerland have so far <a href="http://blogs.lse.ac.uk/brexit/2018/04/25/galileo-satellites-illuminate-eu-uk-divorce-tensions-over-essential-business-and-regulatory-frameworks/">failed to do</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219198/original/file-20180516-155558-1khluub.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">The UK helped build Galileo’s satellites.</span>
<span class="attribution"><a class="source" href="https://www.sstl.co.uk/Press/Lift-off-for-4-Galileo-satellites-as-SSTL-celebrat">SSTL</a></span>
</figcaption>
</figure>
<p>The UK is also very keen to grow its domestic space industry, and has ambitions for it to be worth <a href="http://www.ukspace.org/wp-content/uploads/2018/05/Prosperity-from-Space-strategy_2May2018.pdf">£40 billion by 2030</a>. This is on the back of a robust and ambitious satellite manufacturing sector that already significantly contributes to <a href="https://www.parliament.uk/documents/commons-committees/Exiting-the-European-Union/17-19/Sectoral%20Analyses/34-Space-Report.pdf">around a quarter</a> of all large communication satellites in the world. The UK is also a <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/447284/Draft_Cubesat_regulation_recommendations.pdf">recognised leader</a> in the development and manufacture of smaller satellites such as miniaturised “cubesats”.</p>
<p>The <a href="http://www.ukspace.org/wp-content/uploads/2018/05/Prosperity-from-Space-strategy_2May2018.pdf">latest publication</a> from industry organisation the Space Growth Partnership states that the “the decision to leave the EU creates particular need to raise our game and avoid complacency”. But it also stresses the need to develop the UK’s own capabilities and for the government to become a key customer of the space sector in order to drive further investment. </p>
<p>The main satellite-maker in the UK, the pan-European firm Airbus has already <a href="http://www.bbc.co.uk/news/uk-politics-43891933">reportedly said</a> it has the skills and expertise to lead development of any UK alternative to Galileo. The UK government has also heavily invested in research and development for space robotics, such as through the £29m <a href="https://www.fairspacehub.org/">FAIR-SPACE Hub</a> at the University of Surrey. Couple this with plans to make the UK a viable launchpad for smaller satellites by 2020 made possible by a <a href="https://www.gov.uk/government/news/new-laws-unlock-exciting-space-era-for-uk">recent change to the law</a>, and there is a distinct possibility that the UK space sector could respond well to the challenge to develop a UK GNSS.</p>
<h2>High costs</h2>
<p>The UK has already contributed <a href="https://www.ft.com/content/f2440686-47ce-11e8-8ae9-4b5ddcca99b3">€1.4 billion (£1.2 billion)</a> to the estimated €10 billion euros (£8.5 billion) <a href="https://www.telegraph.co.uk/news/2017/04/13/eu-working-push-british-companies-galileo-satellite-space-contracts/">cost of Galileo</a>. Rough estimates for the UK to build its own GNSS currently sit at <a href="https://www.theguardian.com/business/2018/may/09/airbus-space-contract-will-move-from-uk-to-continent-because-of-brexit">£5 billion</a>. But a more realistic estimate would require a long investigation, and other GNSS systems <a href="https://www.telegraph.co.uk/news/worldnews/europe/eu/8048641/Galileo-satellite-device-over-budget-running-later-and-unprofitable.html">including Galileo</a> <a href="https://www.defenseone.com/business/2016/05/gps-upgrades-are-late-and-over-budget-heres-why-we-should-stay-course/128178/">and GPS</a> have gone over their original budgets.</p>
<p>Yet while it may be difficult to claw back the money spent on Galileo, or justify such a large project in response to Brexit, secure access to a GNSS is vital for modern society. The UK and its space sector in particular should undoubtedly be deeply concerned about losing access to Galileo and other European space programmes after Brexit. </p>
<p>So perhaps now, more than ever, a UK GNSS would be seen as a welcome endorsement of the strengths of the UK space sector. As Richard Peckham, the chair of the UKSpace trade association who has worked on the Galileo project himself, is <a href="http://www.bbc.co.uk/news/science-environment-44002900">quoted as saying</a>, “a British sat-nav would be a fantastic shot in the arm”.</p><img src="https://counter.theconversation.com/content/96495/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ann Swift receives funding from the Satellite Applications Catapult and the UK Space Agency through her work in the South Coast Centre of Excellence in Satellite Applications, which is hosted at the University of Portsmouth where she is employed as an Innovation Fellow.</span></em></p>
British space firms would get a shot in the arm from building a new GPS-style system if the UK is shut out of the EU’s programme.
Ann Swift, Innovation Fellow, University of Portsmouth
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/94958
2018-04-17T10:43:20Z
2018-04-17T10:43:20Z
Pope Francis’ apology for abuse in Chile would once have been unthinkable
<figure><img src="https://images.theconversation.com/files/214606/original/file-20180412-540-1p1g5r9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What does it mean for a pope to apologize?</span> <span class="attribution"><span class="source">AP Photo/Andrew Medichini)</span></span></figcaption></figure><p>In a letter on April 11 to the bishops of Chile, Pope Francis <a href="https://cruxnow.com/global-church/2018/04/11/pope-says-he-incurred-in-serious-errors-in-situation-of-chilean-bishop-accused-of-cover-up/">asked forgiveness</a> for his “serious errors of assessment and perception.” His apologies were directed to the victims of Fr. Fernando Karadima, whose abuse of at least <a href="https://www.ncronline.org/news/accountability/francis-chilean-critics-welcome-apology-hope-action-abuse-cover">three men</a> when they were children was witnessed and covered up by Chilean Bishop Juan Barros. Until recently, Pope Francis had maintained that Bishop Barros was actually the victim of “<a href="https://www.theguardian.com/world/2018/jan/19/pope-francis-victims-church-sexual-abuse-slander-chile">slander</a>.” In 2011, the then 80-year-old Fr. Karadina was found guilty by a Vatican tribunal, and sentenced to a life of “<a href="https://www.nytimes.com/2011/02/19/world/americas/19chile.html?mtrref=www.google.com&gwh=BCF6BA39DA302F3A7D15403C6F789C04&gwt=pay">prayer and penance</a>.”</p>
<p>In times past, a personal apology from the pope would have been close to unthinkable. </p>
<h2>Popes can make mistakes</h2>
<p>Catholics believe the pope is the successor to the Apostle Peter, one of the first followers of Jesus. But Peter was a flawed human being: When confronted by a crowd, he denied his association with Jesus three times. Afterwards, according to the <a href="http://biblehub.com/matthew/">Gospel of Matthew</a>, Peter “<a href="http://biblehub.com/matthew/26-75.htm">wept bitterly</a>.”</p>
<p>For Catholics, Peter’s experience shows that even those specially chosen by God have deep-seated weaknesses for which they must show sorrow. </p>
<p>Popes are not always right in what they do, but their errors have been admitted only years – sometimes centuries – later. In 1992, for example, John Paul II apologized for the Catholic Church’s <a href="http://www.vaticanobservatory.va/content/specolavaticana/en/research/history-of-astronomy/the-galileo-affair.html">condemnation of Galileo</a> that happened over 350 years earlier.</p>
<p>Once rare, papal apologies increased under the reign of John Paul II. While those apologies admitted that the Church made mistakes, they did not ask for forgiveness for past popes. </p>
<h2>Church history on apology</h2>
<p>In the middle ages, popes were not inclined to apologize at all, or even accept apologies. Most famously, in 1077 A.D., Pope Gregory VII initially rejected <a href="https://www.biography.com/people/henry-iv-9335166">King Henry IV’s</a> apology concerning a dispute over who had the power to appoint local bishops. The pope forced Henry, then the king of the <a href="https://www.metmuseum.org/toah/hd/habs/hd_habs.htm">Holy Roman Empire</a>, to wait in a blizzard for three days before accepting him back into the Catholic Church.</p>
<p>This dismissive attitude gave way to soul-searching during <a href="https://www.npr.org/2012/10/10/162573716/why-is-vatican-ii-so-important">the Second Vatican Council,</a> a seminal meeting that modernized the Church, held in Rome from 1962-65. One of the most important issues Catholicism had to confront was its historical persecution of Jews. <a href="http://www.jewishvirtuallibrary.org/the-crusades">Thousands of Jews were killed</a> as Crusaders made their way to Jerusalem. Jews were expelled from <a href="http://www.jewishvirtuallibrary.org/the-spanish-expulsion-1492">Catholic Spain</a> in 1492. And most horrible was the <a href="http://www.yadvashem.org/holocaust/about.html">Holocaust</a>, or “<a href="http://www.jewishvirtuallibrary.org/yom-ha-shoah-holocaust-memorial-day">Shoah</a>,” the organized slaughter of over 6 million Jews, which occurred in Christian-majority nations during the Second World War.</p>
<p>In one of the council’s most important documents, <a href="http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_decl_19651028_nostra-aetate_en.html">Nostra Aetate</a>, the Catholic Church rejected the idea that Jews were responsible for the crucifixion of Jesus Christ. Nostra Aetate also established a foundation for a more <a href="https://www.americamagazine.org/issue/100/jews-and-vatican-ii">cooperative and respectful relationship</a> between <a href="https://crossworks.holycross.edu/rel_faculty_pub/6/">Christians and Jews</a>.</p>
<p>In 1966, the Church moved to apologize for centuries of distrust between Catholics and Protestants, when Pope Paul VI gave his <a href="https://www.telegraph.co.uk/opinion/2016/04/01/sacred-mysteries-the-ring-that-rome-gave-to-canterbury/">ring</a> to Michael Ramsey, the head of the Anglican church – the 100th <a href="https://www.archbishopofcanterbury.org/">archbishop of Canterbury</a> – as an offering of reconciliation.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/214607/original/file-20180412-554-rvx5zi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Pope John Paul II.</span>
<span class="attribution"><span class="source">AP Photo/Alik Keplicz-file</span></span>
</figcaption>
</figure>
<p>Pope John Paul II gave many apologies, but usually on behalf of the Church for what was done centuries ago. Most notable was the “<a href="https://w2.vatican.va/content/john-paul-ii/en/homilies/2000/documents/hf_jp-ii_hom_20000312_pardon.html">Day for Pardon</a>” in March 2000, that asked forgiveness for a series of sins, <a href="http://www.vatican.va/news_services/liturgy/documents/ns_lit_doc_20000312_presentation-day-pardon_en.html">including</a> those “against the dignity of women and the unity of the human race” and “actions against love, peace, the rights of peoples, and respect for cultures and religions.” </p>
<p>But many remember how Pope John Paul II remained largely silent on the issue of clerical abuse because it “did not fit with his image of the Church,” according to Australian bishop <a href="http://www.abc.net.au/news/2015-08-24/former-pope-john-paul-handled-sex-abuse-claims-poorly-inquiry/6719402">Geoffrey Robinson</a>. In a <a href="http://w2.vatican.va/content/john-paul-ii/en/speeches/2002/april/documents/hf_jp-ii_spe_20020423_usa-cardinals.html">2002 address to American cardinals</a>, John Paul II did say he was “greatly grieved” that priests “had caused such suffering and scandal to the young,” but he stopped short of offering a personal plea for forgiveness.</p>
<p>Following John Paul’s example, Pope Benedict XVI stated <a href="https://www.metmuseum.org/toah/hd/habs/hd_habs.htm">in a 2010 letter</a> that he was “sorry” that Catholics of Ireland had “suffered grievously” because of the “abuse of children and vulnerable young people.” But he did not apologize for lack of Vatican oversight over Irish bishops and priests.</p>
<p>Perhaps the closest parallel to Pope Francis’ apology was <a href="https://w2.vatican.va/content/benedict-xvi/en.html">Pope Benedict’s</a> <a href="https://www.nytimes.com/2006/09/17/world/europe/17pope.html?mtrref=www.google.com&gwh=508EBEE41B1FE656E5EDC17DA9BEF1C8&gwt=pay">expression of regret</a> over “reactions” to his <a href="https://www.benedictine.edu/press-room/work/regensburg-address">address</a> in 2006 at the <a href="https://www.uni-regensburg.de/index.html.en">University of Regensburg</a>, Germany, where he seemed to criticize Islam. </p>
<h2>What is Pope Francis doing?</h2>
<p>Fully accepting that the pope is a fallible human being can be somewhat of an emotional struggle for Catholics. While the pope – also called “The Vicar of Christ” – is considered to be <a href="http://www.newadvent.org/cathen/07790a.htm#IIIB">infallible</a> when he formally makes a statement about Catholic doctrine concerning “faith and morals,” the pope certainly makes mistakes in his priestly service and personal life.</p>
<p>Francis, however, is not shy about admitting his own fallibility as a pope and as a person. In fact, he <a href="https://www.americamagazine.org/issue/%E2%80%98i-am-sinner%E2%80%99">said in a 2013 interview</a>: </p>
<blockquote>
<p>“I am a sinner. This the most accurate definition. It is not a figure of speech, a literary genre. I am a sinner.” </p>
</blockquote>
<p>With that statement, Pope Francis was saying that he – a leader of 1 billion people – needs forgiveness and mercy too. And <a href="https://theconversation.com/what-is-the-true-meaning-of-mercy-72461">mercy and forgiveness</a> have been the central themes of his pontificate. </p>
<p>Of the many responsibilities of a pope, chief among them is being a teacher. And when Francis apologized to the people of Chile and to victims of sexual abuse, he also was teaching the rest of us how to admit our sins as a first step in making things right.</p><img src="https://counter.theconversation.com/content/94958/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Schmalz 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>
Popes are not infallible, yet apologies are rare.
Mathew Schmalz, Associate Professor of Religion, College of the Holy Cross
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/76315
2017-04-20T19:55:14Z
2017-04-20T19:55:14Z
Water, water, everywhere in our Solar system but what does that mean for life?
<figure><img src="https://images.theconversation.com/files/166015/original/file-20170420-2410-85mztt.jpg?ixlib=rb-1.1.0&rect=642%2C0%2C1827%2C1266&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">This illustration shows Cassini diving through geyser plumes on Saturn's the ocean world
moon of Enceladus.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/press-release/nasa-missions-provide-new-insights-into-ocean-worlds-in-our-solar-system">NASA/JPL-Caltech</a></span></figcaption></figure><p>There was much excitement when NASA recently <a href="https://www.nasa.gov/press-release/nasa-missions-provide-new-insights-into-ocean-worlds-in-our-solar-system">revealed new details</a> about the oceans that lurk beneath the surface of Saturn’s tiny moon <a href="https://solarsystem.nasa.gov/planets/enceladus">Enceladus</a> and Jupiter’s <a href="https://solarsystem.nasa.gov/planets/europa">Europa</a>.</p>
<p>Why the excitement? Well, here on Earth, where you have water, energy and nutrients, you have life. So why not life on these other worlds?</p>
<p>Thanks to measurements made by the Cassini spacecraft, we already knew that <a href="https://theconversation.com/waterworld-cassini-spots-the-motion-of-enceladuss-ocean-25069">Enceladus has an ocean</a> buried deep beneath its surface. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=867&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=867&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=867&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1089&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1089&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165591/original/image-20170418-32703-12pxuua.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1089&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Enceladus, just 500km across, is now known to host a buried ocean of liquid water.</span>
<span class="attribution"><span class="source">NASA/JPL/Space Science Institute</span></span>
</figcaption>
</figure>
<p>From the new research, <a href="http://science.sciencemag.org/content/356/6334/155">published in Science this month</a>, it now seems highly likely that at the base of that ocean, hydrothermal vents are <a href="https://theconversation.com/nasa-saturn-moon-enceladus-is-able-to-host-life-its-time-for-a-new-mission-76102">actively spewing nutrients and energy</a> into the dark ocean depths. </p>
<p>The vented material drives chemical reactions, deep in the ocean, releasing molecular hydrogen that is eventually carried away from the moon in the <a href="https://www.nasa.gov/mission_pages/cassini/media/cassini-083005.html">giant geysers</a> we observe. </p>
<p>Jupiter’s icy moon Europa has also long been known to host a sub-surface ocean that contains more liquid water than is present on the entire planet Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165603/original/image-20170418-32689-kmdefw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Jupiter’s icy moon Europa. Beneath the icy surface lurks a vast ocean, containing more water than can found on our whole planet.</span>
<span class="attribution"><span class="source">NASA/Jet Propulsion Lab-Caltech/SETI Institute</span></span>
</figcaption>
</figure>
<p>Like Enceladus, it is thought that the base of Europa’s ocean might feature hydrothermal activity, and <a href="https://theconversation.com/the-search-for-life-beneath-the-ice-why-were-going-back-to-europa-43846">hence that it might be a suitable place for life to develop and thrive</a>.</p>
<p>This month’s results tie Europa and Enceladus more closely together than ever. Observations of Europa with the <a href="http://hubblesite.org/">Hubble Space Telescope</a> <a href="http://hubblesite.org/news_release/news/2017-17">revealed two episodes of geyser-like eruptions</a> showed water being ejected to an altitude of 50km above the moon’s surface in 2014, and 100km in 2016. </p>
<h2>Water, water everywhere</h2>
<p>When we look at other planets we see no oceans, no lakes and no rivers. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166020/original/file-20170420-2408-8pauc6.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">Mars, Earth’s closest planetary neighbour, is a beautiful planet but is currently far from ‘Earth-like’.</span>
<span class="attribution"><span class="source">NASA/USGS</span></span>
</figcaption>
</figure>
<p>In the past we tended to imagine that water was a scarce and precious resource. But as we learn more about our place in the Universe, we are becoming ever more aware that <a href="https://www.nasa.gov/jpl/the-solar-system-and-beyond-is-awash-in-water">water is everywhere</a>. </p>
<p><a href="http://chandra.harvard.edu/graphics/resources/illustrations/pieA_sizedB.jpg">Around 75% of all atoms in our galaxy are hydrogen</a>, and it is the most common element in the Universe. Oxygen is the third most common element in space, albeit making up only about 1% of the total sum of all the atoms that are out there. </p>
<p>Water (H<sub>2</sub>O) is made of two hydrogen atoms and one oxygen atom. So it should be no surprise that water is everywhere, nor that it played a key role in the formation and evolution of our planetary system.</p>
<h2>Make me a planet</h2>
<p>When our Sun was forming, the planets and other debris of the Solar system grew around it from a disk of dust, ice and gas. The material closest to the proto-Sun was so hot that only the most refractory elements and compounds (those with the highest melting and boiling points) were solid. </p>
<p>At greater distances, the temperature was lower and more material could freeze, adding to the mass of solid material floating around in what is known as a <a href="http://www.almaobservatory.org/press-room/press-releases/937-almas-best-image-yet-of-a-protoplanetary-disk">protoplanetary disk</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166024/original/file-20170420-2401-bfgc85.jpg?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">An artist’s impression of a protoplanetary disk around a young star, in which planets are being born.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech</span></span>
</figcaption>
</figure>
<p>Eventually, at distances several times farther from the Sun than the Earth, the temperature was cold enough for water to be solid, a point called the “ice line” or “<a href="https://www.cfa.harvard.edu/news/su201326">snow line</a>”. Beyond this, water ice made up the great bulk of solid material. With more solid material, the distant planets grew far more rapidly than their terrestrial cousins.</p>
<p>At the heart of Saturn, Uranus and Neptune, and <a href="https://www.missionjuno.swri.edu/origin?show=hs_origin_story_whats-in-jupiters-core">probably at Jupiter’s core</a>, lie the seeds around which those planets’ gaseous atmospheres were gathered. Dust and gas in the disk gradually stuck together, growing to form larger and larger cores. </p>
<p>Eventually, a critical mass was reached, at which point the growing proto-planets’ gravity could feed from the gas around them in the disk, swelling them into the giants we see today. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=514&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=514&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=514&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=646&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=646&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166027/original/file-20170420-2392-96uvdu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=646&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Solar system’s largest planet, Jupiter, dwarfs the Earth, with this composite picture showing the two side-by-side for comparison.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Those cores remain, behemoths of ice and rock ten times the mass of Earth, shrouded in vast atmospheres.</p>
<p>That leads to an interesting possibility. Far beneath the clouds of Uranus and Neptune, it seems likely that temperatures and pressures will have allowed the material of the cores to differentiate, with the heaviest materials (the metals) sinking to the centre, to be surrounded by a mantle of volatile material - primarily water and ammonia.</p>
<p>Just like Earth’s mantle, that material is likely molten - not an ocean as we imagine it, but certainly not hard, solid rock.</p>
<h2>Icy debris in the Solar system’s depths</h2>
<p>The vast amounts of ice in the young Solar system was not all devoured by the giant planets. Each of those worlds (Jupiter, Saturn, Uranus and Neptune) is accompanied by a swarm of dozens of satellites, ranging in size from <a href="https://solarsystem.nasa.gov/planets/ganymede">bodies larger than our Moon</a> to objects just metres or a few kilometres across.</p>
<p>Most of those moons are more water than anything else. </p>
<p>For many years, it was assumed that the icy moons were just that - frozen husks, solid to their core. But in recent years that idea has gradually been replaced by a newer, more exciting paradigm. The water at the surface of those moons is solid - as hard as granite in many cases. But deep below, in their interiors, lurk buried oceans.</p>
<p>The first such ocean identified was the one beneath the ice of Jupiter’s moon <a href="https://solarsystem.nasa.gov/planets/europa">Europa</a>, a world about the size of our Moon. But Europa is not alone. </p>
<p>Results from the <a href="https://www.jpl.nasa.gov/missions/galileo/">Galileo spacecraft</a>, which orbited Jupiter for eight years in the late 1990s and early 2000s, found tantalising hints that two of Jupiter’s other large moons, <a href="https://solarsystem.nasa.gov/planets/ganymede">Ganymede</a> and <a href="https://solarsystem.nasa.gov/planets/callisto">Callisto</a>, may also house <a href="https://www.nasa.gov/vision/universe/solarsystem/galileo_end.html">deeply buried oceans</a>.</p>
<p>Then came the <a href="https://saturn.jpl.nasa.gov/mission/about-the-mission/quick-facts/">Cassini mission to Saturn</a>. Saturn’s largest moon, <a href="https://solarsystem.nasa.gov/planets/titan">Titan</a>, has a thick atmosphere, and Cassini deployed the <a href="https://saturn.jpl.nasa.gov/mission/spacecraft/huygens-probe/">Huygens lander</a> on its arrival in the system, to parachute through the clouds and see what lurks beneath.</p>
<p>The answer is lakes, rivers and rain. But not liquid water. The ice on frigid Titan’s surface is harder than granite. Instead, Titan’s surface features <a href="https://www.nasa.gov/feature/jpl/cassini-explores-a-methane-sea-on-titan">liquid methane and ethane</a> and large, slow-falling <a href="https://www.nasa.gov/centers/ames/news/releases/2006/06_57AR.html">raindrops of methane</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166029/original/file-20170420-2414-19pnni4.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"></a>
<figcaption>
<span class="caption">Lakes, seas, and rivers of methane and ethane on the surface of Saturn’s largest moon, Titan.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/Agenzia Spaziale Italiana/USGS</span></span>
</figcaption>
</figure>
<p>More recently, Cassini measurements have suggested that the ethane and methane oceans on Titan might not be the only liquid there. Just like Europa, there is <a href="https://www.jpl.nasa.gov/news/news.php?release=2014-217">evidence of a saltwater ocean</a> buried deep beneath the moon’s surface.</p>
<p>Far from liquid water being scarce beyond Earth, it is becoming ever more apparent that it might be common throughout the Solar system.</p>
<p>It isn’t just moons in the outer Solar system that seem to host liquid water. Recent research has suggested that the largest asteroid, Ceres, might have <a href="https://www.newscientist.com/article/mg22530143-800-dwarf-planet-ceres-might-have-right-stuff-for-life/">just such an ocean</a>, as might <a href="http://www.space.com/34737-pluto-wandering-heart-subsurface-ocean.html">Pluto</a>.</p>
<p>And there are still millions of other icy bodies out there, just waiting to be explored.</p>
<h2>Water in the inner Solar system</h2>
<p>All that brings us closer to home, to the inner Solar system. We know that <a href="https://water.usgs.gov/edu/earthhowmuch.html">Earth has water</a>, although it is a far drier world than the objects we have discussed so far. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166037/original/file-20170420-2410-1w6twtf.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">
<figcaption>
<span class="caption">The Hawaiian islands, seen from the International Space Station, make Earth look like a watery world.</span>
<span class="attribution"><a class="source" href="https://eol.jsc.nasa.gov/SearchPhotos/photo.pl?mission=ISS042&roll=E&frame=281151">NASA</a></span>
</figcaption>
</figure>
<p>This isn’t actually a surprise. Earth formed in the warm part of the protoplanetary disk, at a location well within the “snow line”. In fact, the origin of Earth’s water has been a puzzle to astronomers for many years. </p>
<p>It seems most likely that Earth’s water was <a href="https://theconversation.com/giant-impacts-planet-formation-and-the-search-for-life-elsewhere-33478">delivered from the colder reaches of the Solar system through impacts</a>, most likely from the outer reaches of the asteroid belt. That delivery through bombardment would also have targeted Mars and Venus.</p>
<p>There is growing evidence that both <a href="https://www.nasa.gov/press/2015/march/nasa-research-suggests-mars-once-had-more-water-than-earth-s-arctic-ocean">Mars</a> and <a href="https://climate.nasa.gov/news/2475/nasa-climate-modeling-suggests-venus-may-have-been-habitable/">Venus</a> once had oceans much like Earth’s - until the vagaries of time took their toll. </p>
<p>In the 4.5 billion years since the Solar system’s formation, the Sun has grown markedly more luminous. As a result, Venus grew ever warmer until its oceans boiled, hundreds of millions of years ago. </p>
<p>Mars, by contrast, has gradually frozen, <a href="https://theconversation.com/what-makes-one-earth-like-planet-more-habitable-than-another-33479">losing its atmosphere</a> under the combined influence of chemical weathering at the planet’s surface, and the stripping action of the Solar wind and radiation. The water is still there, but no longer in the form of planet-girding oceans.</p>
<h2>Habitable worlds</h2>
<p>So back to Europa, Titan and Enceladus with their oceans buried beneath tens or hundreds of kilometres of ice. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166018/original/file-20170420-2398-hrooma.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">Comparison of the liquid water volume of Earth, Europa and Titan to scale. Only liquid water is considered in these estimates but water ice is also significantly present in Europa and Titan.</span>
<span class="attribution"><a class="source" href="http://phl.upr.edu/library/media/liquidwaterinthesolarsystem">Planetary Habitability Laboratory @ University of Puerto Rico, Arecibo, NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>Could those worlds be habitable? Definitely. With every year that passes, we gather ever more evidence that points in that direction.</p>
<p>Could there be life there? Again, it is possible, but herein lies the catch. </p>
<p>All those locations are right on our doorstep, and yet any life upon them is buried so deeply that we cannot find it. To do so will almost certainly require landers, to drill through the ice to the oceans beneath - an incredibly challenging task.</p>
<p>What does this mean for life elsewhere? Well, if our Solar system tells us anything, it is that our universe is drenched in water. Quite literally, there’s water everywhere. Maybe, just maybe, that’s a hint that we might not be as alone as we think.</p><img src="https://counter.theconversation.com/content/76315/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonti Horner 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>
Earth is a relatively dry planet compared to some of the other ocean worlds in our Solar system. Life needs water so what about life on these other places?
Jonti Horner, Vice Chancellor's Senior Research Fellow, University of Southern Queensland
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/66360
2016-10-04T11:03:04Z
2016-10-04T11:03:04Z
Before Nobels: Gifts to and from rich patrons were early science’s currency
<figure><img src="https://images.theconversation.com/files/140176/original/image-20161003-20230-1y2fuw5.jpg?ixlib=rb-1.1.0&rect=12%2C97%2C724%2C549&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Galileo demonstrates a telescope to the doge of Venice. </span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bertini_fresco_of_Galileo_Galilei_and_Doge_of_Venice.jpg">Giuseppe Bertini</a></span></figcaption></figure><p>While the first <a href="http://www.nobelprize.org">Nobel Prizes</a> were handed out in 1901, rewards for scientific achievement have been around much longer. As early as the 17th century, at the very origins of modern experimental science, promoters of science realized the need for some system of recognition and reward that would provide incentive for advances in the field.</p>
<p>Before the prize, <a href="https://www.amazon.com/Patronage-Institutions-Technology-Medicine-1500-1750/dp/0851152856">it was the gift that reigned in science</a>. Precursors to modern scientists – the early astronomers, philosophers, physicians, alchemists and engineers – offered wonderful achievements, discoveries, inventions and works of literature or art as gifts to powerful patrons, often royalty. Authors prefaced their publications with extravagant letters of dedication; they might, or they might not, be rewarded with a gift in return. Many of these practitioners worked outside of academe; even those who enjoyed a modest academic salary lacked today’s large institutional funders, <a href="http://www.hup.harvard.edu/catalog.php?isbn=9780674005365">beyond the Catholic Church</a>. Gifts from patrons offered a crucial means of support, yet they came with many strings attached. </p>
<p>Eventually, different kinds of incentives, including prizes and awards, as well as new, salaried academic positions, became more common and the favor of particular wealthy patrons diminished in importance. But at the height of the Renaissance, scientific precursors relied on gifts from powerful princes <a href="http://dx.doi.org/10.2202/1932-0213.1040">to compensate and advertise their efforts</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=275&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=275&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=275&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=345&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=345&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140181/original/image-20161003-30459-15ika1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=345&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Galileo presents an experiment to a Medici patron.</span>
<span class="attribution"><a class="source" href="http://einstein.stanford.edu/Library/images/Galileo-incline-expt.jpg">Giuseppe Bezzuoli</a></span>
</figcaption>
</figure>
<h2>Presented to please a patron</h2>
<p>With courtiers all vying for a patron’s attention, gifts had to be presented with drama and flair. <a href="http://press.uchicago.edu/ucp/books/book/chicago/G/bo3640574.html">Galileo Galilei (1564-1642) presented his newly discovered moons</a> of Jupiter to the Medici dukes as a “gift” that was literally out of this world. In return, Prince Cosimo “ennobled” Galileo with the title and position of court philosopher and mathematician.</p>
<p>If a gift succeeded, the gift-giver might, like Galileo in this case, be fortunate enough to receive a gift in return. Gift-givers could not, however, predict what form it would take, and they might find themselves burdened with offers they couldn’t refuse. Tycho Brahe (1546-1601), the great Danish Renaissance astronomer, received everything from cash to chemical secrets, exotic animals and islands <a href="http://www.cambridge.org/us/academic/subjects/history/history-science-and-technology/tychos-island-tycho-brahe-and-his-assistants-15701601?format=HB&isbn=9780521650816">in return for his discoveries</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=590&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=590&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=590&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=742&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=742&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140021/original/image-20161003-9475-8gkdmg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=742&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Swedish inventor Alfred Nobel’s profile is on the medals awarded to the recipients of the prizes he established.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Nobel_Prize.png">Erik Lindberg</a></span>
</figcaption>
</figure>
<p>Patrons often bestowed <a href="http://www.ucpress.edu/book.php?isbn=9780520205086">gold portrait medals with their own images</a>, a form that survives in the Nobel medal to this day. The medal usually came on a chain that could be sold, but the recipient could not cash in on patron’s image itself without offense.</p>
<p>Regifting was to be expected. Once a patron had received a work he or she was quick to use the new knowledge and technology in their own gift-giving power plays, to impress and overwhelm rivals. King James I of England planned to sail a shipful of delightful automata (essentially early robots) to India to “court” and “please” royalty there, and to offer the Mughal Emperor Jahangir the <a href="http://dx.doi.org/10.1353/con.2013.0023">art of “cooling and refreshing” the air in his palace</a>, a technique recently developed by James’ court engineer Cornelis Drebbel (1572-1633). <a href="http://texty.citanka.cz/hyzrle/z1-14.html">Drebbel had won his own position</a> years earlier by showing up unannounced at court, falling to his knees, and presenting the king with a marvelous automaton.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=456&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=456&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=456&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=573&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=573&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140269/original/image-20161004-20239-10dqieb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=573&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 version of Drebbel’s automaton sits on the table by the window in this scene of a collection.</span>
<span class="attribution"><a class="source" href="http://art.thewalters.org/detail/14623/the-archdukes-albert-and-isabella-visiting-a-collectors-cabinet/">Hieronymous Francken II and Brueghel the Elder</a></span>
</figcaption>
</figure>
<h2>Searching for better incentive structures</h2>
<p>Gifts were unpredictable and sometimes undesired. They could go terribly wrong, <a href="https://uwpress.wisc.edu/books/3152.htm">especially across cultural divides</a>. And they required the giver to inflate the dramatic aspects of their work, not unlike the modern critique that journals favor the most surprising or flashy research leaving negative results to molder. With personal tastes and honor at stake, the gift could easily go awry. </p>
<p>Scientific promoters already realized in the early 17th century that gift-giving was ill-suited to encouraging experimental science. Experimentation required many individuals to collect data in many places across long periods of time. Gifts emphasized competitive individualism at a time when scientific collaboration and the often humdrum work of empirical observation was paramount. </p>
<p>While some competitive rivalry could help inspire and advance science, too much could lead to the ostentation and secrecy that too often plagued courtly gift-giving. Most of all, scientific reformers feared an individual would not tackle a problem that couldn’t be finished and presented to a patron in his or her lifetime – or even if they did, their incomplete discoveries might die with them.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=968&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=968&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=968&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1217&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1217&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140184/original/image-20161003-20221-uhjg2v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1217&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Francis Bacon saw the need for better incentive systems in science.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Lord_Bacon.jpg">Frontispiece of Sylva sylvarum</a></span>
</figcaption>
</figure>
<p>For these reasons, promoters of experimental science saw the reform of rewards as integral to radical changes in the pace and scale of scientific discovery. For example, Sir Francis Bacon (1561-1626), lord chancellor of England and an influential booster of experimental science, emphasized the importance even of “approximations” or incomplete attempts at reaching a particular goal. Instead of dissipating their efforts attempting to appease patrons, many researchers, he hoped, could be stimulated to work toward the same ends <a href="http://www.cambridge.org/us/academic/subjects/history/history-ideas-and-intellectual-history/knowledge-and-public-interest-15751725?format=HB">via a well-publicized research wish list</a>. </p>
<p>Bacon coined the term “desiderata,” <a href="http://dx.doi.org/10.2514/6.2010-2514">still used by researchers today</a> to denote widespread <a href="http://theappendix.net/issues/2014/7/perchance-to-dream-science-and-the-future">research goals</a>. Bacon also suggested many ingenious ways to advance discovery by stimulating the human hunger for fame; a row of statues celebrating famous inventors of the past, for example, could be paired with a row of empty plinths upon which researchers might imagine their own busts one day resting.</p>
<p>Bacon’s techniques inspired <a href="https://www.hrionline.ac.uk/hartlib/context">one of his chief admirers, the reformer Samuel Hartlib</a> (circa 1600-1662) to collect many schemes for reforming the system of recognition. One urged that rewards should go not only “to such as exactly hit the marke, but even to those that probably misse it,” because their errors would stimulate others and make “active braines to beate about for New Inventions.” Hartlib planned a centralized office systematizing rewards for those who “expect Rewards for Services done to the King or State, and know not where to pitch and what to desire.”</p>
<h2>Moving toward a more modern mode</h2>
<p>Collaborative scientific societies, beginning in the mid-17th century, distanced rewards from the whims and demands of individual patrons. The periodicals that many new scientific societies started publishing offered a new medium that allowed authors to tackle ambitious research problems that might not individually produce a complete publication pleasing to a dedicatee. </p>
<p>For example, artificial sources of luminescence were exciting chemical discoveries of the 17th century that made pleasing gifts. A lawyer who pursued alchemy in his spare time, Christian Adolph Balduin (1632-1682), presented the particular glowing chemicals he discovered in spectacular forms, such as an imperial orb that shone with the name “Leopold” for the Habsburg emperor. </p>
<p>Many were not satisfied, however, with Balduin’s explanations of why these chemicals glowed. The journals of the period feature many attempts to <a href="http://dx.doi.org/10.1179/1745823414Y.0000000003">experiment upon or question the causes</a> of such luminescence. They provided an outlet for more workaday investigations into how these showy displays actually worked. </p>
<p>The societies themselves saw their journals as a means to entice discovery by offering credit. Today’s <a href="https://www.leopoldina.org/en/about-us/about-the-leopoldina/about-the-leopoldina/">Leopoldina</a>, the German national scientific society, founded its journal in 1670. According to its official bylaws, those who might not otherwise publish their findings could see them “<a href="http://www.zvab.com/Gr%C3%BCndung-Leopoldina-Academia-Naturae-Curiosorum-historischen/10921834363/buch">exhibited to the world</a> in the journal to their credit and with the praiseworthy mention of their name,” an important step on the way to standardizing scientific citation and norms of establishing priority.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=433&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=433&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140187/original/image-20161003-20217-4hp8gq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=433&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Louis XIV surveys the members of the Royal Academy of Sciences in 1667.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Colbert_Presenting_the_Members_of_the_Royal_Academy_of_Sciences_to_Louis_XIV_in_1667.PNG">Henri Testelin</a></span>
</figcaption>
</figure>
<p>Beyond the satisfaction of seeing one’s name in print, academies also began offering essay prizes upon particular topics, a practice which continues to this day. Historian Jeremy Caradonna <a href="http://www.cornellpress.cornell.edu/book/?GCOI=80140100395520">estimates 15,000 participants in such competitions</a> in France between 1670, when the Royal Academy of Sciences began awarding prizes, and 1794. These were often funded by many of the same individuals, such as royalty and nobility, who in former times would have functioned as direct patrons, but now did so through the intermediary of the society. </p>
<p>States might also offer rewards for solutions to desired problems, most famously in the case of the prizes offered by the English <a href="https://cudl.lib.cam.ac.uk/collections/longitude">Board of Longitude</a> beginning in 1714 for figuring out how to determine longitude at sea. Some in the 17th century likened this long-sought discovery to the philosophers’ stone. The idea of using a prize to focus attention on a particular problem is alive and well today. In fact, some contemporary scientific prizes, such as the Simons Foundation’s “<a href="https://www.simonsfoundation.org/mathematics-and-physical-science/news-announcements/new-simons-collaboration-cracking-the-glass-problem/">Cracking the Glass Problem</a>,” set forth specific questions to resolve that were already frequent topics of research in the 17th century.</p>
<p>The shift from gift-giving to prize-giving transformed the rules of engagement in scientific discovery. Of course, the need for monetary support hasn’t gone away. The scramble for funding can still be a sizable part of what it takes to get science done today. Succeeding in grant competitions might seem mystifyng and winning a career-changing Nobel might feel like a bolt out of the blue. But researchers can take comfort that they no longer have to present their innovations on bended knee as wondrous gifts to satisfy the whims of individual patrons.</p><img src="https://counter.theconversation.com/content/66360/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vera Keller 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>
People have always known science would advance faster with various incentives and rewards. As modern experimental science took off, these took the form of gifts and favors to and from wealthy elites.
Vera Keller, Associate Professor of History, University of Oregon
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/63719
2016-08-10T20:05:10Z
2016-08-10T20:05:10Z
The Galileo gambit and other stories: the three main tactics of climate denial
<figure><img src="https://images.theconversation.com/files/133635/original/image-20160810-11853-deh1ua.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Galileo was right, but that doesn't mean his fans are.</span> <span class="attribution"><span class="source">Justus Sustermans/Wikimedia Commons</span></span></figcaption></figure><p>The recently elected One Nation senator from Queensland, Malcolm Roberts, fervently rejects the established scientific fact that human greenhouse gas emissions cause climate change, invoking a <a href="https://theconversation.com/one-nation-climate-denial-and-those-jewish-bankers-62176">fairly familiar trope of paranoid theories</a> to propound this belief. </p>
<p>Roberts <a href="https://www.theguardian.com/environment/planet-oz/2016/aug/09/why-one-nation-senator-malcolm-roberts-demand-for-empirical-evidence-on-climate-change-is-misleading-bunk">variously claims</a> that the United Nations is trying to impose world government on us through climate policy, and that CSIRO and the Bureau of Meteorology are corrupt institutions that, one presumes, have fabricated the <a href="https://theconversation.com/state-of-the-climate-2015-global-warming-and-el-nino-sent-records-tumbling-63511">climate extremes</a> that we increasingly observe all over the world.</p>
<p>In the world of Malcolm Roberts, these agencies are marionettes of a “cabal” of “the major banking families in the world”. Given the parallels with <a href="http://rationalwiki.org/wiki/International_Jewish_conspiracy">certain strands of anti-Jewish sentiment</a>, it’s perhaps an unfortunate coincidence that Roberts has <a href="http://www.smh.com.au/federal-politics/political-news/one-nation-senatorelect-malcolm-roberts-wrote-bizarre-sovereign-citizen-letter-to-julia-gillard-20160804-gqlesa.html">reportedly relied on a notorious Holocaust denier</a> to support this theory.</p>
<p>It might be tempting to dismiss his utterances as conspiratorial ramblings. But they can teach us a great deal about the psychology of science denial. They also provide us with a broad spectrum of diagnostics to spot pseudoscience posing as science.</p>
<h2>The necessity of conspiracism</h2>
<p>First, the appeal to a conspiracy among scientists, bankers and governments is never just a slip of the tongue but a pervasive and necessary ingredient of the denial of well-established science. The tobacco industry <a href="https://www.industrydocumentslibrary.ucsf.edu/tobacco/docs/#id=pyfy0144">referred to medical research on lung cancer</a> as being conducted by an “oligopolistic cartel” that “manufactures alleged evidence”. Some people accuse the US Central Intelligence Agency (CIA) of <a href="http://content.time.com/time/specials/packages/article/0,28804,1860871_1860876_1861031,00.html">creating and spreading AIDS</a>, and much anti-vaccination content on the web is suffused with <a href="http://www.naturalnews.com/048605_vaccine_hysteria_totalitarian_nightmare_medical_fascism.html">conspiratorial allegations</a> of totalitarianism.</p>
<p>This conspiratorial mumbo jumbo inevitably arises when people deny facts that are supported by an overwhelming body of evidence and are no longer the subject of genuine debate in the scientific community, having already been tested thoroughly. As evidence mounts, there comes a point at which inconvenient scientific findings can only be explained away by recourse to huge, nebulous and nefarious agendas such as the World Government or Stalinism.</p>
<p>If you are addicted to nicotine but terrified of the effort required to give up smoking, it might be comforting instead to accuse medical researchers of being oligopolists (whatever that means). </p>
<p>Likewise, if you are a former coal miner, <a href="http://www.onenation.com.au/team/malcolmroberts">like Malcolm Roberts</a>, it is perhaps easier to accuse climate scientists of colluding to create a world government (whatever that is) than to accept the need to take coal out of our economy.</p>
<p>There is now <a href="http://dx.doi.org/10.5964/jspp.v3i1.443">ample research</a> showing the link between science denial and conspiracism. This link is supported by <a href="http://dx.doi.org/10.1111/j.1539-6924.2012.01801.x">independent studies</a> from around the world.</p>
<p>Indeed, the link is so established that conspiracist language is one of the <a href="https://theconversation.com/one-nations-malcolm-roberts-is-in-denial-about-the-facts-of-climate-change-63581">best diagnostic tools</a> you can use to spot pseudoscience and science denial.</p>
<h2>The Galileo gambit</h2>
<p>How else can science dissenters attempt to justify their contrarian position? Another tactic is to appeal to heroic historical dissenters, the usual hero of choice being <a href="https://en.wikipedia.org/wiki/Galileo_Galilei">Galileo Galilei</a>, who overturned the orthodoxy that everything revolves around the Earth. </p>
<p>This appeal is so common in pseudoscientific quackery that it is known as the <a href="http://rationalwiki.org/wiki/Galileo_gambit">Galileo gambit</a>. The essence of this argument is:</p>
<blockquote>
<p>They laughed at Galileo, and he was right.</p>
<p>They laugh at me, therefore I am right.</p>
</blockquote>
<p>A primary logical difficulty with this argument is that plenty of people are laughed at <a href="http://www.skepdic.com/rumpology.html">because their positions are absurd</a>. Being dismissed by scientists doesn’t automatically entitle you to a Nobel Prize.</p>
<p>Another logical difficulty with this argument is that it implies that no scientific opinion can ever be valid unless it is rejected by the vast majority of scientists. Earth must be flat because no scientist other than a Googling Galileo in Gnowangerup says so. Tobacco must be good for you because only tobacco-industry operatives believe it. And climate change must be a hoax because only the heroic Malcolm Roberts and his <a href="http://www.galileomovement.com.au/galileo_movement.php">Galileo Movement</a> have seen through the conspiracy.</p>
<p>Yes, Senator-elect Roberts is the project leader of the Galileo Movement, which denies the scientific consensus on climate change, favouring instead the opinions of <a href="http://www.galileomovement.com.au/who_we_are.php">a pair of retired engineers and the radio personality Alan Jones</a>.</p>
<p>Any invocation of Galileo’s name in the context of purported scientific dissent is a red flag that you’re being fed pseudoscience and denial.</p>
<h2>The sounds of science</h2>
<p>The rejection of well-established science is often couched in sciency-sounding terms. The word “evidence” has assumed a particular prominence in pseudoscientific circles, perhaps because it sounds respectable and evokes images of <a href="https://en.wikipedia.org/wiki/Hercule_Poirot">Hercule Poirot</a> tenaciously investigating dastardly deeds.</p>
<p>Since being elected, Roberts has again aired his <a href="https://www.theguardian.com/environment/planet-oz/2016/aug/09/why-one-nation-senator-malcolm-roberts-demand-for-empirical-evidence-on-climate-change-is-misleading-bunk">claim</a> that there is “no empirical evidence” for climate change. </p>
<p>But “show us the evidence” has become the war cry of all forms of science denial, from <a href="https://www.google.co.uk/search?num=100&newwindow=1&client=firefox-b&q=%22show+us+the+evidence%22+vaccinations&oq=%22show+us+the+evidence%22+vaccinations&gs_l=serp.3...143936.145654.0.146005.12.5.0.0.0.0.441.441.4-1.1.0....0...1c.1.64.serp..11.0.0.S-Nkz3umzM4">anti-vaccination activists</a> to <a href="http://www.abovetopsecret.com/forum/thread1080905/pg1">creationists</a>, despite the existence of abundant evidence already.</p>
<p>This co-opting of the language of science is a useful rhetorical device. Appealing to evidence (or a lack thereof) seems reasonable enough at first glance. Who wouldn’t want evidence, after all? </p>
<p>It is only once you know the genuine state of the science that such appeals are revealed to be specious. <a href="https://theconversation.com/one-nations-malcolm-roberts-is-in-denial-about-the-facts-of-climate-change-63581">Literally thousands of peer-reviewed scientific articles and the national scientific academies of 80 countries</a> support the pervasive scientific consensus on climate change. Or, as the environmental writer <a href="https://www.theguardian.com/environment/2005/may/10/environment.columnists">George Monbiot has put it</a>: </p>
<blockquote>
<p>It is hard to convey just how selective you have to be to dismiss the evidence for climate change. You must climb over a mountain of evidence to pick up a crumb: a crumb which then disintegrates in the palm of your hand. You must ignore an entire canon of science, the statements of the world’s most eminent scientific institutions and thousands of papers published in the foremost scientific journals.</p>
</blockquote>
<p>Accordingly, <a href="http://www.shapingtomorrowsworld.org/lewandowskyGEC16.html">my colleagues and I recently showed that in a blind test</a> – the gold standard of experimental research – contrarian talking points about climate indicators were uniformly judged to be misleading and fraudulent by expert statisticians and data analysts.</p>
<p>Conspiracism, the Galileo gambit and the use of sciency-sounding language to mislead are the three principal characteristics of science denial. Whenever one or more of them is present, you can be confident you’re listening to a debate about politics or ideology, not science.</p><img src="https://counter.theconversation.com/content/63719/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephan Lewandowsky receives funding from the Australian Research Council, the Royal Society, and the Psychonomic Society.</span></em></p>
One Nation Senator-elect Malcolm Roberts lauds Galileo as a hero who turned scientific consensus on its head. But the ‘Galileo gambit’ is just one weapon in the climate conspiracists’ arsenal.
Stephan Lewandowsky, Chair of Cognitive Psychology, University of Bristol
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/60103
2016-05-30T20:20:29Z
2016-05-30T20:20:29Z
Copernicus’ revolution and Galileo’s vision: our changing view of the universe in pictures
<figure><img src="https://images.theconversation.com/files/124244/original/image-20160527-22063-xrogic.png?ixlib=rb-1.1.0&rect=0%2C991%2C2200%2C2025&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Galileo's sketches of the moon, showing its phases.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Galileo%27s_sketches_of_the_moon.png">Wikimedia/Galileo</a></span></figcaption></figure><p>It’s not a stretch to say the Copernican revolution fundamentally changed the way we think about our place in the universe. In antiquity people believed the Earth was the centre of the solar system and the universe, whereas now we know we are on just one of many planets orbiting the sun.</p>
<p>But this shift in view didn’t happen overnight. Rather, it took almost a century of new theory and careful observations, often using simple mathematics and rudimentary instruments, to reveal our true position in the heavens.</p>
<p>We can gain insights into how this profound shift unfolded by looking at the actual notes left by the astronomers who contributed to it. These notes give us a clue to the labour, insights and genius that drove the Copernican revolution. </p>
<h2>Wandering stars</h2>
<p>Imagine you’re an astronomer from antiquity, exploring the night sky without the aid of a telescope. At first the planets don’t really distinguish themselves from the stars. They’re a bit brighter than most stars and twinkle less, but otherwise look like stars. </p>
<p>In antiquity, what really distinguished planets from stars was their motion through the sky. From night to night, the planets gradually moved with respect to the stars. Indeed “planet” is derived from the Ancient Greek for “wandering star”. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/5-bJGzLAq58?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The motion of Mars over many weeks.</span></figcaption>
</figure>
<p>And planetary motion isn’t simple. Planets appear to speed up and slow down as they cross the sky. Planets even temporarily reverse direction, exhibiting “<a href="http://www.esa.int/spaceinvideos/Videos/2014/09/ESA_Studio_Retrograde_Motion_No_Dates">retrograde motion</a>”. How can this be explained?</p>
<h2>Ptolemy epicycles</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=391&fit=crop&dpr=1 600w, https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=391&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=391&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/117852/original/image-20160407-16263-18tv9uv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A page of an Arabic copy of Ptolemy’s Almagest, illustrating the Ptolemaic model for a planet moving around the Earth.</span>
<span class="attribution"><span class="source">Qatar National Library</span></span>
</figcaption>
</figure>
<p>Ancient Greek astronomers produced geocentric (Earth-centred) models of the solar system, which reached their pinnacle with the work of <a href="http://www.britannica.com/biography/Ptolemy">Ptolemy</a>. This model, from an Arabic copy of Ptolemy’s <a href="http://www.qdl.qa/en/archive/81055/vdc_100000004884.0x000001">Almagest</a>, is illustrated above. </p>
<p>Ptolemy explained planetary motion using the superposition of two circular motions, a large “<a href="http://www.mathpages.com/home/kmath639/kmath639.htm">deferent</a>” circle combined with a smaller “<a href="http://www.mathpages.com/home/kmath639/kmath639.htm">epicycle</a>” circle. </p>
<p>Furthermore, each planet’s deferent could be offset from the position of the Earth and the steady (angular) motion around the deferent could be defined using a position know as an <a href="http://www2.ups.edu/faculty/jcevans/Equant.pdf">equant</a>, rather than the position of the Earth or the centre of the deferent. Got that? </p>
<p>It is rather complex. But, to his credit, Ptolemy’s model predicted the positions of planets in the night sky with an accuracy of a few degrees (sometimes better). And it thus became the primary means of explaining planetary motion for over a millennium. </p>
<h2>Copernicus’ shift</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=685&fit=crop&dpr=1 600w, https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=685&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=685&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=861&fit=crop&dpr=1 754w, https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=861&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/117916/original/image-20160408-23929-w6ijzp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=861&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Copernican Revolution placed the sun at the centre of our solar system.</span>
<span class="attribution"><span class="source">Library of the Congress</span></span>
</figcaption>
</figure>
<p>In 1543, the year of his death, <a href="http://www.space.com/15684-nicolaus-copernicus.html">Nicolaus Copernicus</a> started his eponymous revolution with the publication of <a href="https://www.loc.gov/item/46031925">De revolutionibus orbium coelestium</a> (On the Revolutions of the Celestial Spheres). Copernicus’ model for the solar system is heliocentric, with the planets circling the sun rather than Earth. </p>
<p>Perhaps the most elegant piece of the Copernican model is its natural explanation of the changing apparent motion of the planets. The retrograde motion of planets such as Mars is merely <a href="http://www.esa.int/spaceinvideos/Videos/2014/09/ESA_Studio_Retrograde_Motion_Explanation">an illusion</a>, caused by the Earth “overtaking” Mars as they both orbit the sun.</p>
<h2>Ptolemaic baggage</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/117906/original/image-20160407-16293-2s401q.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">The original Copernican model has similarities to Ptolemaic models, including circular motions and epicycles.</span>
<span class="attribution"><span class="source">Library of the Congress</span></span>
</figcaption>
</figure>
<p>Unfortunately, the original Copernican model was loaded the Ptolemaic baggage. The Copernican planets still travelled around the solar system using motions described by the superposition of circular motions. Copernicus disposed of the equant, which he <a href="https://books.google.com.au/books?id=RbT1CAAAQBAJ&pg=PA78#v=onepage&q&f=false">despised</a>, but replaced it with the mathematically equivalent epicyclet. </p>
<p>Astronomer-historian <a href="http://owengingerich.com/">Owen Gingerich</a> and his colleagues calculated planetary coordinates using Ptolemaic and Copernican models of the era, and found that <a href="https://dash.harvard.edu/handle/1/4258973">both had comparable errors</a>. In some cases the position of Mars is in error by 2 degrees or more (far larger than the diameter of the moon). Furthermore, the original Copernican model was no simpler than the earlier Ptolemaic model.</p>
<p>As 16th Century astronomers did not have access to telescopes, Newtonian physics, and statistics, it wasn’t obvious to them that the Copernican model was superior to the Ptolemaic model, even though it correctly placed the sun in the centre of the solar system.</p>
<h2>Along comes Galileo</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=426&fit=crop&dpr=1 600w, https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=426&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=426&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=536&fit=crop&dpr=1 754w, https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=536&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/117921/original/image-20160408-23938-1eiukl2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=536&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Galileo’s telescopic observations of the planets, including the phases of Venus, demonstrated that planets travel around the Sun.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>From 1609, Galileo Galilei used the recently invented telescope to observe the sun, moon and planets. He saw the <a href="http://www.loc.gov/exhibits/world/heavens.html#obj75">mountains and craters</a> of the moon, and for the first time revealed the planets to be worlds in their own right. Galileo also provided strong observational evidence that planets orbited the sun. </p>
<p>Galileo’s observations of Venus were particularly compelling. In Ptolemaic models, Venus remains between the Earth and the sun at all times, so we should mostly view the night side of Venus. But Galileo was able to observe the day-lit side of Venus, indicating that Venus can be on the opposite side of the sun from the Earth.</p>
<h2>Kepler’s war with Mars</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=254&fit=crop&dpr=1 600w, https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=254&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=254&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=320&fit=crop&dpr=1 754w, https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=320&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/117926/original/image-20160408-23929-jox17r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=320&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Johannes Kepler triangulated the position of Mars by using observations of Mars when it returned to the same position in its orbit.</span>
<span class="attribution"><span class="source">University of Sydney</span></span>
</figcaption>
</figure>
<p>The circular motions of Ptolemaic and Copernican models resulted in large errors, particularly for Mars, whose predicted position could be in error by several degrees. <a href="http://kepler.nasa.gov/Mission/JohannesKepler/">Johannes Kepler</a> devoted years of his life to understanding the motion of Mars, and he cracked this problem with a most ingenious weapon. </p>
<p>Planets (approximately) repeat the same path as they orbit the sun, so they return to the same position in space once every orbital period. For example, Mars returns to the same position in its orbit every 687 days. </p>
<p>As Kepler knew the dates when a planet would be at the same position in space, he could use the different positions of the Earth along its own orbit to triangulate the planets’ positions, as illustrated above. Kepler, using astronomer <a href="http://galileo.rice.edu/sci/brahe.html">Tycho Brahe’s</a> <a href="https://www.princeton.edu/%7Ehis291/Mural_Quadrant.html">pre-telescopic observations</a>, was able to trace out the elliptical paths of the planets as they orbited the sun. </p>
<p>This allowed Kepler to formulate his <a href="http://astro.unl.edu/naap/pos/pos_background1.html">three laws of planetary motion</a> and predict planetary positions with <a href="http://scitation.aip.org/content/aip/magazine/physicstoday/article/64/9/10.1063/PT.3.1259">far greater precision</a> than previously possible. He thus laid the groundwork for the Newtonian physics of the late 17th century, and the remarkable science that followed. </p>
<p>Kepler himself <a href="https://books.google.com.au/books?id=774fAQAAIAAJ&dq=kepler+nova+astronomia&focus=searchwithinvolume&q=inhabited">captured</a> the new world view and its broader significance in 1609’s <a href="https://www.library.usyd.edu.au/libraries/rare/modernity/kepler4.html">Astronomia nova</a> (New Astronomy):</p>
<blockquote>
<p>To me, however the truth is more pious still, and (with all due respect to the Doctors of the Church) I prove philosophically not only that the earth is round, not only that it is inhabited all the way around at the antipodes, not only that is it contemptibly small, but also that it is carried along among the stars.</p>
</blockquote><img src="https://counter.theconversation.com/content/60103/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael J. I. Brown receives research funding from the Australian Research Council and Monash University, and has developed space-related titles for Monash University's MWorld educational app.</span></em></p>
We take our understanding of the solar system for granted, but it took centuries to figure out. The original writings of Ptolemy, Copernicus, Galileo and others show how they sparked a revolution.
Michael J. I. Brown, Associate professor, Monash University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/54935
2016-02-25T14:53:26Z
2016-02-25T14:53:26Z
Four centuries after Galileo was silenced, UK students are still curbing free speech
<figure><img src="https://images.theconversation.com/files/112925/original/image-20160225-15150-1115yls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Galileo Galilei was imprisoned for his 'heretical' views.</span> <span class="attribution"><span class="source">Wellcome Images</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>It’s 400 years since the Catholic Church censored Galileo and denied him a platform for his arguments for the motion of the Earth – a theory now considered entirely uncontroversial and, indeed, part of our understanding of life, the universe and everything. But in those days, with the Inquisition at the height of its powers, heterodoxy was seen as threatening the very fabric of the Church.</p>
<p>I was reminded of the “Galileo Affair” last year, when controversy erupted over <a href="http://manchesterstudentsunion.com/articles/updated-statement-from-the-students-union-05-10-2015">the “No Platform” decision</a> by the executive committee of Manchester University’s Students’ Union to ban the lesbian feminist writer Julie Bindel. She was prevented from speaking at an event on campus called: “From liberation to censorship: does modern feminism have a problem with free speech?” </p>
<p>Bindel’s views on transsexuals – for example in <a href="http://www.theguardian.com/world/2004/jan/31/gender.weekend7">this Guardian column</a> – which included referring to a male-to-female transsexual as a “man in a dress”, led the Manchester students’ union to ban her (along with her fellow invitee, Milo Yiannopoulos) on the grounds that her presence would: “incite hatred towards and exclusion of our trans students”. </p>
<p>As Europe lurched towards the <a href="http://www.britannica.com/event/Thirty-Years-War">Thirty Years’ War</a>, the Roman Church certainly had a problem with free speech. On February 26, 1616 Galileo was informed by the pope that the Church had decided that his theory of the Earth’s motion “was formally heretical since it explicitly contradicts in many places the sense of Holy Scripture.” He was ordered “to abstain completely from teaching or defending this doctrine and opinion or from discussing it”.</p>
<p>Galileo later complied with a requirement to abjure his opinion. It did not help him much, and he spent the rest of his life under house arrest. Julie Bindel also <a href="http://www.divamag.co.uk/category/news/protesters-picket-diversity-awards.aspx">made a public apology in 2011</a>, for the “tone and content” of her 2004 article in The Guardian in which she wrote that “men disposing of their genitals does not make them women”.</p>
<p>People in all ages have accepted that there are limits to public discourse. There is no unfettered freedom of expression, no right knowingly to utter a false statement, to slander, perjure or shout “fire!” in a crowded theatre. What changes over time and place is what those limits are, who sets them, on what authority and why.</p>
<h2>No platform</h2>
<p>The No Platform policy of the National Union of Students (NUS) is a recent example that has come in for criticism. It applied traditionally to individuals or organisations which the NUS identified as racist or fascist, such as the English Defence League or Hizb-ut-Tahrir, but the application is spreading. Few would defend platforms in British universities for hate speech, incitement to violence, or holocaust deniers such as David Irving, but now Julie Bindel is banned as transphobic and George Galloway as a rape apologist.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"652424249232203776"}"></div></p>
<p>Bindel’s ban was justified by the <a href="http://www.nus.org.uk/en/take-action/liberation-campaigns/">NUS’s LGBTQ Liberation Campaign</a>. Her invitation was <a href="http://manchesterstudentsunion.com/articles/updated-statement-from-the-students-union-05-10-2015">flagged by Manchester’s Student Union</a> executive committee “as potentially in breach of our safe space policy” and refused “based on Bindel’s views and comments towards trans people, which we believe could incite hatred towards and exclusion of our trans students”. Controversy continues as to whether the ban conformed to the <a href="http://s3-eu-west-1.amazonaws.com/nusdigital/document/documents/17915/2474048df1f844083a5a1a91da3dc5bd/Safe%20Space%20Policy%20ws.pdf">union’s policy</a> and Manchester University’s <a href="http://documents.manchester.ac.uk/display.aspx?DocID=11846">Code of Practice on Freedom of Speech</a>.</p>
<h2>Dogma vs debate</h2>
<p>In the case of Galileo’s ban, the traditional thesis of conflict between science and religion regards it as a clear example of open-minded scientists suffering at the hands of dogmatic and authoritarian churchmen. More recently, revisionist historians have argued that the Catholic Church had some justification. </p>
<p>Catholicism had to maintain its authority to interpret scripture as many embraced the Protestant “heresy”. The reformist Pope Urban VIII (like Gorbachev in the last years of the USSR) was under pressure from ideological hardliners, and his theologians and inquisitors were empowered to counter deviance. </p>
<p>Moreover, Galileo repeatedly pushed his luck: his <a href="http://www.webexhibits.org/calendars/year-text-Galileo.html">Dialogue Concerning the Two Chief World Systems</a> of 1632, which precipitated his trial, signally failed to fulfil his promise to put both sides fairly. Given the sectarian divisions and religiously motivated violence that broke out during the English Civil War, we might conclude that Rome was right. Censorship can close down incitements to violence and hatred.</p>
<h2>Beyond freedom and dignity</h2>
<p>What are the parallels today? Will students’ understanding of gender be advanced or retarded if radical opinions (abrasively expressed to be sure) are censored? Should sabbatical officers of student unions have the power to decide who speaks? How much authority does the NUS LGBTQ liberation agenda possess? Above all, why is the NUS expanding its restrictions on free speech and what are the dangers that justify it? </p>
<p>Several student unions <a href="http://www.exeterguild.org/change/ideas/idea390-stopsafespace/">have rejected</a> “No Platform” – and a transgender student whom I know well would prefer a space to engage with Bindel to a space where they are saved from her by the NUS.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"698869926111682564"}"></div></p>
<p>If the Galileo and Bindel affairs are analogous, then history suggests a lesson. I side with historians who conclude that the Catholic Church’s censorship of Copernicanism (and other scientific theories) resulted in <a href="https://books.google.co.uk/books?id=hs2edDIGCqEC&pg=PA153&lpg=PA153&dq=Cosmological+discussion+ceased+except+among+the+Jesuits&source=bl&ots=bt0H0RhXYT&sig=dKHtl_YiOuiWIwzMgajwwfCvspU&hl=en&sa=X&ved=0ahUKEwil3cSYhpPLAhUDwBQKHaqWD9UQ6AEIITAB#v=onepage&q=Cosmological%20discussion%20ceased%20except%20among%20the%20Jesuits&f=false">northern and Protestant Europe overtaking Italy</a> as the centre of innovation in astronomy and physics. </p>
<p>Of course, a lot is at stake in transgender politics today – but so was there back in 1616 concerning the motion of the Earth.</p><img src="https://counter.theconversation.com/content/54935/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Pumfrey 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 ‘No Platform’ campaign from the National Union of Students is stifling debate on university campuses.
Stephen Pumfrey, Senior Lecturer, Lancaster University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/43845
2015-06-25T04:37:50Z
2015-06-25T04:37:50Z
Europa: attempt no landing here, but a fly-by is fine!
<figure><img src="https://images.theconversation.com/files/86343/original/image-20150625-12998-ehiuwn.jpg?ixlib=rb-1.1.0&rect=0%2C72%2C2300%2C1425&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What mysteries lie beneath your icy crust, Europa?</span> <span class="attribution"><span class="source">NASA/JPL-Caltech/SETI Institute</span></span></figcaption></figure><p>NASA has now formally started to pack its bags for the next big discovery mission, this time heading to Jupiter’s icy moon <a href="https://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Europa">Europa</a>. Last month NASA announced <a href="http://www.nasa.gov/press-release/nasa-s-europa-mission-begins-with-selection-of-science-instruments">the instruments</a> that will fly on this trip and now has formally moved it from <a href="http://www.jpl.nasa.gov/missions/europa/">“concept” to “development”</a> stage. </p>
<p>Formally known as Europa Clipper, the mission will be known as <a href="http://solarsystem.nasa.gov/missions/profile.cfm?MCode=EuropaFlyby">Europa Multiple Flyby Mission</a>, at least until a more glamorous name is picked. It’s slated for a possible launch in 2025 and will arrive hot on the heels of the European Space Agency’s (ESA) Jupiter Icy Moons Explorer (<a href="https://theconversation.com/the-anticipation-of-some-freshly-squeezed-results-6991">JUICE</a>) mission, which will be well into its investigation of Europa’s neighbour <a href="https://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Ganymede">Ganymede</a> by then. </p>
<p>It has not been an easy journey to get the mission to this stage. It is to the credit of a massive team of scientists, engineers and science communicators engaging with policy makers that <a href="https://theconversation.com/us-plans-to-answer-the-lure-of-europa-33990">this has happened at all</a>. </p>
<h2>The lure of Europa</h2>
<p>We’re still sifting through the massive amount of data that the <a href="http://science.nasa.gov/missions/galileo/">Galileo spacecraft</a> has beamed back from the Jupiter system, so why go back? </p>
<p>It is actually the tentative peek that Galileo gave us into the mysterious icy moon that is a prime motivator for a return trip. Of all the discoveries that this (<a href="http://www.space.com/18632-galileo-spacecraft.html">at times struggling</a>) spacecraft made, the most famous was the evidence it collected for a moon-wide ocean beneath Europa’s icy crust.</p>
<p>Based on data from Galileo, and follow up measurements from the Hubble Space Telescope, we have gathered clues that any ocean under the ice would be a rather cosy place to be. It might even be the best place for life in our solar system, apart from our own home.</p>
<p>But the presence of an ocean is still only one theory of many as to Europa’s inner makeup. To help settle the matter, NASA’s new mission will fly with an <a href="http://www.astrobio.net/topic/solar-system/jupiter/europa/radar-techniques-used-in-antarctica-will-scour-europa-for-life-supporting-environments/">ice-penetrating radar</a>, built by the University of Austin in Texas, which will work with a number of other instruments to gain a better picture of what may lie beneath the cold crust. </p>
<p>Those follow-up measurement by the Hubble Space telescope <a href="https://theconversation.com/europa-the-new-spa-destination-of-the-solar-system-21460">spotted potential geysers from Europa’s surface</a>. So to map these out, the new mission will also carry a thermal imaging camera, with the hope of discovering features like the “<a href="http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=1889">tiger stripes</a>” of Saturn’s moon Enceladus. </p>
<h2>State of the art snaps</h2>
<p>Also, the Galileo mission ended dramatically in 2003 (with the probe <a href="http://www.nasa.gov/missions/solarsystem/galileo_impact.html">hurling itself</a> into the depths of Jupiter). The mission was launched in 1989, and although it would have flown with state-of-the-art equipment for the time, can you recall state-of-the-art what was in the 1980’s?</p>
<p>Just imagining the fantastic pictures this new Europa mission will yield brings me out in goose bumps. And capturing high resolution is exactly the plan, with this mission flying an instrument, Europa Imaging System (EIS), that will resolve the icy surface down to a resolution of 50 metres. </p>
<p>Preparations are already well underway for us to interpret the data that the mission will send back. In fact, there have been a few leaps in our understanding of Europa this year already. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=265&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=265&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=265&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=333&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=333&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86342/original/image-20150625-12990-w9t3bq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=333&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bizarre features on Europa’s icy surface suggest a warm interior.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech</span></span>
</figcaption>
</figure>
<h2>What else is there?</h2>
<p>Although we refer to Europa and its companions, Ganymede and Callisto, as being “icy”, it’s pretty well understood that there’s a significant fraction of other “stuff” on these moons. There are a number of candidates as to what this is, such as magnesium sulfate and sulfuric acid, but a new possibility was outlined earlier this year: humble table salt.</p>
<p>While the optical properties of salt as we know it don’t fit with what we’ve seen from Europa, NASA scientists discovered that <a href="http://mashable.com/2015/05/12/europa-jupiter-moon-salt-ocean/">radiation-damaged salt does</a>. That’s pertinent, because the radiation on the top of Europa’s surface – mainly coming from Jupiter – is actually very high. So salt that seeps there could be damaged and create the “dirty ice” that we see on the surface. </p>
<p>More analysis of the light reflected off Europa by the new spacecraft could very well show if this radiation-damaged salt – or indeed any of the other candidates – are there on Europa. </p>
<h2>What lies under the ice?</h2>
<p>At the same time, researchers have been out in the field, investigating places that are rather like Europa here on Earth. In 2014 a group tested how effective a <a href="http://spie.org/x113852.xml">small robot</a> was at burrowing though the ice on the <a href="http://www.antarcticglaciers.org/antarctica/photographs/mcmurdo/">McMurdo ice shelf</a> in Antarctica. </p>
<p>Hopefully we’ll see more of the use of these types of probes to study the <a href="https://theconversation.com/life-in-lake-vostok-the-link-between-antarctica-and-extra-terrestrials-5334">lakes trapped in the Antarctic ice</a>. Aside from the knowledge we might gain about our own polar environment, we’ll learn more about how to control these robots when they are 628 million kilometres away on one of Jupiter’s moons. </p>
<p>With all going well through the design phase, this new Europa mission will be on its way in 2025 and be sending us data from the enigmatic moon in the 2030s. Initially it looks like it will fly-by Europa 45 times, but hopefully a mission extension will be on the cards too. Perhaps by then we’ll have a plan to land on the ice and burrow into any potential ocean on the way. </p>
<p>I hope Arthur C Clarke wouldn’t have been too cross.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/38EDhpxzn2g?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Final scene from 2010: The Year We Make Contact, including the haunting words from the makers of the monoliths.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/43845/count.gif" alt="The Conversation" width="1" height="1" />
NASA has now formally started to pack its bags for the next big discovery mission, this time heading to Jupiter’s icy moon Europa. Last month NASA announced the instruments that will fly on this trip and…
Helen Maynard-Casely, Instrument Scientist, Australian Nuclear Science and Technology Organisation
Licensed as Creative Commons – attribution, no derivatives.