tag:theconversation.com,2011:/ca/topics/big-bang-470/articlesBig Bang – The Conversation2023-11-15T13:21:33Ztag:theconversation.com,2011:article/2154142023-11-15T13:21:33Z2023-11-15T13:21:33ZThe universe is expanding faster than theory predicts – physicists are searching for new ideas that might explain the mismatch<figure><img src="https://images.theconversation.com/files/559383/original/file-20231114-23-g88npv.png?ixlib=rb-1.1.0&rect=8%2C7%2C1189%2C1210&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The James Webb Space Telescope's deep field image shows a universe full of sparkling galaxies.</span> <span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2022/038/01G7JGTH21B5GN9VCYAHBXKSD1?news=true">NASA/STScI</a></span></figcaption></figure><p>Astronomers have known for decades that the universe is expanding. When they use telescopes to observe faraway galaxies, they see that these <a href="https://theconversation.com/explainer-the-mysterious-dark-energy-that-speeds-the-universes-rate-of-expansion-40224">galaxies are moving away</a> from Earth.</p>
<p>To astronomers, the wavelength of light a galaxy emits is longer the faster the galaxy is moving away from us. The farther away the galaxy is, the more its light has shifted toward the longer wavelengths on the red side of the spectrum – so the higher the “redshift.”</p>
<p>Because the speed of light is finite, fast, but not infinitely fast, seeing something far away means we’re looking at the thing how it looked in the past. With distant, high-redshift galaxies, we’re <a href="https://theconversation.com/looking-back-toward-cosmic-dawn-astronomers-confirm-the-faintest-galaxy-ever-seen-207602">seeing the galaxy</a> when the universe was in a younger state. So “high redshift” corresponds to the early times in the universe, and “low redshift” corresponds to the late times in the universe. </p>
<p>But as astronomers have studied these distances, they’ve learned that the universe is not just expanding – its rate of expansion is accelerating. And that expansion rate is even faster than the leading theory predicts it should be, leaving <a href="https://rekeeley.github.io/">cosmologists like me</a> puzzled and looking for new explanations. </p>
<h2>Dark energy and a cosmological constant</h2>
<p>Scientists call the source of this acceleration <a href="https://theconversation.com/dark-energy-map-gives-clue-about-what-it-is-but-deepens-dispute-about-the-cosmic-expansion-rate-143200">dark energy</a>. We’re not quite sure what drives dark energy or how it works, but we think its behavior could be explained by <a href="https://doi.org/10.1086/300499">a cosmological constant</a>, which is a <a href="https://doi.org/10.1038/d41586-018-05095-z">property of spacetime</a> that contributes to the expansion of the universe. </p>
<p>Albert Einstein originally came up with this constant – he marked it with a lambda in his theory of <a href="https://theconversation.com/why-does-gravity-pull-us-down-and-not-up-162141">general relativity</a>. With a <a href="https://www.livescience.com/cosmological-constant.html">cosmological constant</a>, as the universe expands, the energy density of the cosmological constant stays the same.</p>
<p>Imagine a box full of particles. If the volume of the box increases, the density of particles would decrease as they spread out to take up all the space in the box. Now imagine the same box, but as the volume increases, the density of the particles stays the same. </p>
<p>It doesn’t seem intuitive, right? That the energy density of the cosmological constant does not decrease as the universe expands is, of course, very weird, but this property helps explain the accelerating universe.</p>
<h2>A standard model of cosmology</h2>
<p>Right now, the leading theory, or standard model, of cosmology is <a href="https://lambda.gsfc.nasa.gov/education/graphic_history/univ_evol.html">called “Lambda CDM</a>.” Lambda denotes the cosmological constant describing dark energy, and CDM stands for cold dark matter. This model describes both the acceleration of the universe in its late stages as well as the expansion rate in its early days.</p>
<p>Specifically, the Lambda CDM explains observations of the cosmic microwave background, which is the afterglow of microwave radiation from when the universe <a href="https://doi.org/10.1051/0004-6361/201833910">was in a “hot, dense state</a>” about 300,000 years after the Big Bang. Observations using the <a href="https://www.esa.int/Enabling_Support/Operations/Planck">Planck satellite</a>, which measures the <a href="https://www.esa.int/Science_Exploration/Space_Science/Herschel/Cosmic_Microwave_Background_CMB_radiation">cosmic microwave background</a>, led scientists to create the Lambda CDM model. </p>
<p>Fitting the Lambda CDM model to the cosmic microwave background allows physicists to predict the value of the <a href="https://news.uchicago.edu/explainer/hubble-constant-explained">Hubble constant</a>, which isn’t actually a constant but a measurement describing the universe’s current expansion rate. </p>
<p>But the Lambda CDM model isn’t perfect. The expansion rate scientists have calculated by measuring distances to galaxies, and the expansion rate as described in Lambda CDM using <a href="https://doi.org/10.3847/2041-8213/ac5c5b">observations of the cosmic microwave background</a>, don’t line up. Astrophysicists call that disagreement the Hubble tension.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration showing the progression of the Universe's expansion after the Big Bang. The Universe is depicted as a cylindrical funnel with labels along the bottom showing the first stars, the development of planets, and now the dark energy acceleration" src="https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553089/original/file-20231010-21-bzoffm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&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 universe is expanding faster than predicted by popular models in cosmology.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/infographics/the-big-bang-and-expansion-of-the-universe">NASA</a></span>
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<h2>The Hubble tension</h2>
<p>Over the past few years, I’ve been <a href="https://doi.org/10.1103/PhysRevLett.131.111002">researching ways</a> to explain this Hubble tension. The tension may be indicating that the Lambda CDM model is incomplete and physicists should modify their model, or it could indicate that it’s time for researchers to come up with new ideas about how the universe works. And new ideas are always the most exciting things for a physicist.</p>
<p>One way to explain the Hubble tension is to modify the Lambda CDM model by changing the expansion rate at low redshift, at late times in the universe. Modifying the model like this can help physicists predict what sort of physical phenomena might be causing the Hubble tension. </p>
<p>For instance, maybe dark energy is not a cosmological constant but instead the result of gravity working in new ways. If this is the case, dark energy would evolve as the universe expands – and the cosmic microwave background, which shows what the universe looked like only a few years after its creation, would have a different prediction for the Hubble constant. </p>
<p>But, <a href="https://doi.org/10.1103/PhysRevLett.131.111002">my team’s latest research</a> has found that physicists can’t explain the Hubble tension just by changing the expansion rate in the late universe – this whole class of solutions falls short.</p>
<h2>Developing new models</h2>
<p>To study what types of solutions could explain the Hubble tension, we <a href="https://doi.org/10.1103/PhysRevLett.131.111002">developed statistical tools</a> that enabled us to test the viability of the entire class of models that change the expansion rate in the late universe. These statistical tools are very flexible, and we used them to match or mimic different models that could potentially fit observations of the universe’s expansion rate and might offer a solution to the Hubble tension.</p>
<p>The models we tested include evolving dark energy models, where dark energy acts differently at different times in the universe. We also tested interacting dark energy-dark matter models, where dark energy interacts with dark matter, and modified gravity models, where gravity acts differently at different times in the universe. </p>
<p>But none of these could fully explain the Hubble tension. These results suggest that physicists should study the early universe to understand the source of the tension.</p><img src="https://counter.theconversation.com/content/215414/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ryan Keeley does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The universe is expanding faster than physicists would expect. To figure out what processes underlie this fast expansion rate, some researchers are first trying to rule out what processes can’t.Ryan Keeley, Postdoctoral Scholar in Physics, University of California, MercedLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2110672023-09-24T12:10:23Z2023-09-24T12:10:23ZWhy Einstein must be wrong: In search of the theory of gravity<figure><img src="https://images.theconversation.com/files/548379/original/file-20230914-27-fu6fow.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C2497&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As new and powerful telescopes gather new data about the universe, they reveal the limits of older theories.</span> <span class="attribution"><span class="source">(Shutterstock)</span></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/why-einstein-must-be-wrong-in-search-of-the-theory-of-gravity" width="100%" height="400"></iframe>
<p>Einstein’s theory of gravity — <a href="https://www.space.com/17661-theory-general-relativity.html">general relativity</a> — has been very successful for more than a century. However, it has theoretical shortcomings. This is not surprising: the theory predicts its own failure at spacetime singularities inside black holes — and the <a href="https://www.einstein-online.info/en/spotlight/avoiding_the_big_bang/">Big Bang itself</a>. </p>
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Read more:
<a href="https://theconversation.com/our-understanding-of-black-holes-has-changed-over-time-172816">Our understanding of black holes has changed over time</a>
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<p>Unlike physical theories describing the other three fundamental forces in physics — the electromagnetic and the strong and weak nuclear interactions — the general theory of relativity has only been tested in weak gravity. </p>
<p>Deviations of gravity from general relativity are by no means excluded nor tested everywhere <a href="https://doi.org/10.1038/s41550-022-01808-7">in the universe</a>. And, according to theoretical physicists, deviation must happen.</p>
<h2>Deviations and quantum mechanics</h2>
<p>According to Einstein, our universe originated in a Big Bang. Other singularities hide inside black holes: Space and time cease to have meaning there, while quantities such as energy density and pressure become infinite. These signal that Einstein’s theory is failing there and must be replaced with a more fundamental one.</p>
<p>Naively, spacetime singularities should be resolved by quantum mechanics, which apply at very small scales.</p>
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Read more:
<a href="https://theconversation.com/will-we-have-to-rewrite-einsteins-theory-of-general-relativity-50057">Will we have to rewrite Einstein's theory of general relativity?</a>
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<p>Quantum physics relies on two simple ideas: <a href="https://www.quantamagazine.org/what-is-a-particle-20201112/">point particles</a> make no sense; and the <a href="https://theconversation.com/explainer-heisenbergs-uncertainty-principle-7512">Heisenberg uncertainty principle</a>, which states that one can never know the value of certain pairs of quantities with absolute precision — for example, the position and velocity of a particle. This is because particles should not be thought of as points but as waves; at small scales they behave as waves of matter.</p>
<p>This is enough to understand that a theory that embraces both general relativity and quantum physics should be free of such pathologies. However, all attempts to blend general relativity and quantum physics necessarily introduce deviations from Einstein’s theory. </p>
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<a href="https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a black circle surrounded with a ring of light" src="https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=358&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=358&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=358&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=450&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=450&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548820/original/file-20230918-27-exi2b0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=450&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 photo of the 1919 complete solar eclipse.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1098/rsta.1920.0009">(Arthur Eddington/Philosophical Transactions of the Royal Society)</a></span>
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</figure>
<p>Therefore, Einstein’s gravity cannot be the ultimate theory of gravity. Indeed, it was not long after the introduction of general relativity by Einstein in 1915 that Arthur Eddington, best known for verifying this theory in the <a href="https://doi.org/10.1098/rsnr.2020.0040">1919 solar eclipse</a>, started searching for alternatives just to see how things could be different. </p>
<p>Einstein’s theory has survived all tests to date, accurately predicting various results from the <a href="https://doi.org/10.12942/lrr-2014-4">precession of Mercury’s orbit to the existence of gravitational waves</a>. So, where are these deviations from general relativity hiding?</p>
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Read more:
<a href="https://theconversation.com/gravitational-waves-discovered-top-scientists-respond-53956">Gravitational waves discovered: top scientists respond</a>
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<h2>Cosmology matters</h2>
<p>A century of research has given us the standard model of cosmology known as the Λ-Cold Dark Matter <a href="https://lambda.gsfc.nasa.gov/education/graphic_history/univ_evol.html">(ΛCDM) model</a>. Here, Λ stands for either Einstein’s famous cosmological constant or a mysterious dark energy with similar properties. </p>
<p>Dark energy was introduced ad hoc by astronomers to explain the <a href="https://doi.org/10.1103/RevModPhys.75.559">acceleration of the cosmic expansion</a>. Despite fitting cosmological data extremely well until recently, the ΛCDM model is spectacularly incomplete and unsatisfactory from the theoretical point of view. </p>
<p>In the past five years, it has also faced severe <a href="https://doi.org/10.1088/1361-6382/ac086d">observational tensions</a>. The Hubble constant, which determines the age and the distance scale in the universe, can be measured in the early universe using the cosmic microwave background and in the late universe using supernovae as standard candles. </p>
<p>These two measurements give <a href="https://doi.org/10.1088/1361-6382/ac086d">incompatible results</a>. Even more important, the nature of the main ingredients of the ΛCDM model — <a href="https://theconversation.com/the-experiments-trying-to-crack-physics-biggest-question-what-is-dark-energy-52917">dark energy</a>, <a href="https://theconversation.com/why-do-astronomers-believe-in-dark-matter-122864">dark matter</a> and the field driving early universe <a href="https://www.newscientist.com/definition/cosmic-inflation/">inflation</a> (a very brief period of extremely fast expansion originating the seeds for galaxies and galaxy clusters) — remains a mystery.</p>
<p>From the observational point of view, the most compelling motivation for modified gravity is the acceleration of the universe discovered in 1998 with <a href="https://doi.org/10.1086/307221">Type Ia supernovae</a>, whose luminosity is dimmed by this acceleration. The ΛCDM model based on general relativity postulates an extremely exotic dark energy with negative pressure permeating the universe. </p>
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<a href="https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="eight bright circles in a dark sky" src="https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548822/original/file-20230918-27-jr07hx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Type Ia supernovae were discovered in 1998, and revealed more about the rate of the universe’s acceleration.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/jpl/galex/pia18929/after-the-explosion-investigating-supernova-sites">(Sloan Digital Sky Survey/NASA)</a></span>
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<p>Problem is, this dark energy has no physical justification. Its nature is completely unknown, although a <a href="https://doi.org/10.1142/S0219887807001928">plethora of models</a> has been proposed. The proposed alternative to dark energy is a cosmological constant Λ which, according to quantum-mechanical <a href="https://doi.org/10.1103/RevModPhys.61.1">back-of-the-envelope (but questionable) calculations</a>, should be huge. </p>
<p>However, Λ must instead be incredibly fine-tuned to a tiny value to fit the cosmological observations. If dark energy exists, our ignorance of its nature is deeply troubling.</p>
<h2>Alternatives to Einstein’s theory</h2>
<p>Could it be that troubles arise, instead, from wrongly trying to fit the cosmological observations into general relativity, like fitting a person into a pair of trousers that are too small? That we are observing the first deviations from general relativity while the mysterious dark energy simply does not exist? </p>
<p>This idea, <a href="https://doi.org/10.1142/S0218271802002025">first proposed</a> by researchers at the University of Naples, has gained tremendous popularity while the contending dark energy camp remains vigorous. </p>
<p>How can we tell? Deviations from Einstein gravity are <a href="https://doi.org/10.12942/lrr-2014-4">constrained by solar system experiments</a>, the recent observations of <a href="https://doi.org/10.1103/PhysRevLett.116.061102">gravitational waves</a> and the <a href="https://doi.org/10.3847/2041-8213/ab0ec7">near-horizon images of black holes</a>.</p>
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Read more:
<a href="https://theconversation.com/say-hello-to-sagittarius-a-the-black-hole-at-the-center-of-the-milky-way-galaxy-183008">Say hello to Sagittarius A*, the black hole at the center of the Milky Way galaxy</a>
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<p>There is now a <a href="https://doi.org/10.1103/RevModPhys.82.451">large literature</a> on theories of gravity alternative to general relativity, going back to Eddington’s 1923 early investigations. A very popular class of alternatives is the so-called scalar-tensor gravity. It is conceptually very simple since it only introduces one additional ingredient (a scalar field corresponding to the simplest, spinless, particle) to Einstein’s geometric description of gravity. </p>
<p>The consequences of this program, however, are far from trivial. A striking phenomenon is the “<a href="https://doi.org/10.1007/s41114-018-0011-x">chameleon effect</a>,” consisting of the fact that these theories can disguise themselves as general relativity in high-density environments (such as in stars or in the solar system) while deviating strongly from it in the low-density environment of cosmology.</p>
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Read more:
<a href="https://theconversation.com/the-search-for-dark-matter-and-dark-energy-just-got-interesting-46422">The search for 'dark matter' and 'dark energy' just got interesting</a>
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<p>As a result, the extra (gravitational) field is effectively absent in the first type of systems, disguising itself as a chameleon does, and is felt only at the largest (cosmological) scales.</p>
<h2>The current situation</h2>
<p>Nowadays the spectrum of alternatives to Einstein gravity has widened dramatically. Even adding a single massive scalar excitation (namely, a spin-zero particle) to Einstein gravity —and keeping the resulting equations “simple” to avoid some known fatal instabilities — has resulted in the much wider class of <a href="https://doi.org/10.1142/S0218271819420069">Horndeski theories</a>, and subsequent generalizations. </p>
<p>Theorists have spent the last decade extracting physical consequences from these theories. The recent detections of <a href="https://doi.org/10.1103/PhysRevLett.116.061102">gravitational waves</a> have provided a way to <a href="https://doi.org/10.1103/PhysRevD.95.084029">constrain the physical class of modifications</a> of Einstein gravity allowed.</p>
<p>However, much work still needs to be done, with the hope that future advances in <a href="https://www.nature.com/articles/s42254-019-0101-z">multi-messenger astronomy</a> lead to discovering modifications of general relativity where gravity is extremely strong.</p><img src="https://counter.theconversation.com/content/211067/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Valerio Faraoni receives funding from the Natural Sciences and Engineering Research Council of Canada.</span></em></p><p class="fine-print"><em><span>Andrea Giusti received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Actions (grant agreement No. 895648). </span></em></p>Einstein’s theory of general relativity suggests that our universe originated in a Big Bang. But black holes, and their gravitational forces, challenge the limits of Einstein’s work.Valerio Faraoni, Professor, Physics & Astronomy, Bishop's UniversityAndrea Giusti, Postdoctoral fellow, Swiss Federal Institute of Technology ZurichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2136902023-09-18T12:19:43Z2023-09-18T12:19:43Z‘Big Bang of Numbers’ – The Conversation’s book club explores how math alone could create the universe with author Manil Suri<figure><img src="https://images.theconversation.com/files/548584/original/file-20230915-21-llxf3v.jpg?ixlib=rb-1.1.0&rect=30%2C36%2C4059%2C2955&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fractals emerge on Day 4 of Suri's playful Genesis-inspired narrative about math's role in creation.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/abstract-glowing-swirl-backgrounds-royalty-free-image/1129644961">oxygen/Moment via Getty Images</a></span></figcaption></figure><p><em>The Conversation U.S. launched its new book club with a bang – talking to mathematician <a href="https://scholar.google.com/citations?user=lFWFsSkAAAAJ&hl=en&oi=ao">Manil Suri</a> about his nonfiction work “<a href="https://wwnorton.com/books/9781324007036">The Big Bang of Numbers: How to Build the Universe Using Only Math</a>.” Suri, <a href="https://theconversation.com/pi-gets-all-the-fanfare-but-other-numbers-also-deserve-their-own-math-holidays-200046">a previous</a> <a href="https://theconversation.com/want-to-fix-gerrymandering-then-the-supreme-court-needs-to-listen-to-mathematicians-114345">author in</a> <a href="https://theconversation.com/declines-in-math-readiness-underscore-the-urgency-of-math-awareness-202691">The Conversation</a>, has also written an award-winning <a href="https://www.manilsuri.com/books">fiction trilogy</a>, in addition to being a professor of mathematics and statistics at the University of Maryland, Baltimore County.</em></p>
<p><em>Below is an edited excerpt from the book club discussion. You’re welcome to keep the conversation flowing by adding your own questions for Suri to the comments.</em></p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/7_GDfXBUsS8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Watch the full book club meeting and leave your own question in the comments at the bottom of this article.</span></figcaption>
</figure>
<hr>
<p><strong>What is the Big Bang of numbers and where do you go from there in the book?</strong></p>
<p>I think the story for me started way back when I was an undergraduate in Bombay. My algebra professor told us this very famous saying by <a href="https://www.britannica.com/biography/Leopold-Kronecker">Leopold Kronecker</a>, the famous mathematician, that God gave us the integers and all the rest is the work of human beings. What he meant was that once you have the whole numbers – 1, 2, 3, 4 – which are somehow coming from heaven, then you can build up the rest of mathematics from it.</p>
<p>And then he went on and said, Hey, I can actually do better. I don’t need God. I can actually, as a mathematician, create the numbers out of nothing. And he showed us this marvelous, almost magic trick, where you start with something called the empty set and then you start building the numbers.</p>
<p>It was the closest I’ve been to a religious experience, almost like the walls just dissolved and suddenly there were numbers everywhere. </p>
<p>Once I started writing my novels, I was meeting a lot of people who were artists and writers. And they would always say, you know, we used to love math when we were in school, but afterward we never had a chance to really pursue it. And can you tell us something about your mathematics?</p>
<p>So, I started building a kind of talk, which started with this big bang, as I call it, building the numbers out of nothing. I finally decided I should write a math book, and it would be aimed at a wide audience.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="black and white photo of a sea shell with light triangles of various sizes" src="https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548579/original/file-20230915-29605-ileohl.jpeg?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">Patterns in nature, like the triangles on this shell, can be explained by simple mathematical rules.</span>
<span class="attribution"><a class="source" href="https://wwnorton.com/books/9781324007036">Larry Cole</a></span>
</figcaption>
</figure>
<p>And I said, well, can you go further? You can create the numbers, but can you actually start building everything, including the whole universe from that? So that was a way to try to lay out mathematics almost as a story where one thing follows from the other and everything is embedded in one narrative.</p>
<p><strong>Who were you imagining to be your readers as you were writing the book?</strong></p>
<p>There’s just so much joy to be had out of mathematics, so many things that you don’t really see in normal courses where the emphasis is always on doing the calculations, finding the right answer. So this book is written for people who want to really engage with mathematics on the level of ideas rather than get into computations and calculations.</p>
<p><strong>After you set off your Big Bang of numbers, you dig in to some of life’s big questions. What do you see as math’s role in grappling with those big thoughts, like where the universe came from, why we even exist and so on?</strong></p>
<p>Once you start talking about the Big Bang, what comes into your mind is creation. There is a doctrine called <em>creatio ex nihilo</em>, which is basically creating everything out of nothing. </p>
<p>That’s a cornerstone of many religions where God creates the universe out of nothing. It’s also in some sense being explored by physicists, where you have some sort of singularity and from that, everything emerges in the Big Bang.</p>
<p>So my thought was, both these areas, religion and physics, are in the public’s imagination much more than mathematics is. Is there a way to posit math as the creative force of everything?</p>
<p>Physicist <a href="https://www.nobelprize.org/prizes/physics/1963/wigner/biographical/">Eugene Wigner</a>, who was a Nobel laureate, talked about the “unreasonable effectiveness” of mathematics at describing everything in our physical universe. It’s so good at modeling physics and what have you. Could it be that math is really the true driving force of the universe? Rather than us just inventing it and using it to describe the universe, could the universe really be describing mathematics? Then the universe is just a physical manifestation, an approximation, if you will, of those mathematical ideas. It’s a completely different view of math.</p>
<p><strong>There’s an ongoing debate over whether math is something that people invented or whether it’s something that exists independently of us. In the book, you say that perhaps the deepest insight that math can offer us is that it’s both of those things.</strong></p>
<p>So the glib answer to your question whether math’s invented or discovered is that you have to create a new word. Instead of discovered or invented it’s “disvented.”</p>
<p>What I mean by that is simply that there are some questions we really can’t get to any kind of logical or supportable answer. One is the question of our own existence – people might believe one thing or the other, but it always comes down to: Is there some real purpose to our lives, or is our creation just something that happened randomly – you know, molecules getting together?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="silhouette of a head with lots of math notations exploding out" src="https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=296&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=296&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=296&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=372&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=372&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548576/original/file-20230915-19-czqnre.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=372&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Is math something that is born from the human mind?</span>
<span class="attribution"><a class="source" href="https://wwnorton.com/books/9781324007036">'The Big Bang of Numbers'</a></span>
</figcaption>
</figure>
<p>Now if we invent mathematics, then we’re inventing it for a purpose. If it just generates by itself, starting with emptiness, building around numbers in some strange realm that we don’t know about, then it’s just wafting around, purposeless.</p>
<p>Math has that duality that can’t be resolved. So it’s a metaphor, telling us, hey, you can’t decide for math, and you’ll never be able to decide for yourself about your own existence. </p>
<p><strong>Can you tell us a bit about your previous books, the Indian novels?</strong></p>
<p>The first one was called “<a href="https://wwnorton.com/books/9780393342826">The Death of Vishnu</a>.” I went back to visit my parents in Mumbai in around 1995, and this man Vishnu, who used to live in our building and do errands, was dying on our steps. I started writing this as a short story.</p>
<p>It started going into a more philosophical realm when a writing teacher said, you know, Vishnu is also the name of the caretaker of the universe in Hindu mythology. So if you name somebody Vishnu, you need to somehow explore that. So that’s what opened up this whole new world for me.</p>
<p>The second book was “<a href="https://wwnorton.com/books/9780393333633">The Age of Shiva</a>.” That one’s the journey of a woman right after India’s independence in 1947. She’s making her way in a very male-dominated world, and she’s not perfect.</p>
<p>Then the third one, I decided, OK, I need to put in some science and math characters. So “<a href="https://wwnorton.co.uk/books/9780393346817-the-city-of-devi-77f37252-adcc-41f0-9b53-383405f76cab">The City of Devi</a>” actually has both a physicist and a statistician. Again it’s in Mumbai, set in the future with the threat of a nuclear war with Pakistan and a love triangle unfolding in front of that. </p>
<p>It’s kind of interesting. I thought that I was done with this mythical “where do we come from?” kind of philosophy that I had in the three books, but apparently not, because now “<a href="https://wwnorton.com/books/9781324007036">The Big Bang of Numbers</a>” looks at it from a mathematical perspective.</p><img src="https://counter.theconversation.com/content/213690/count.gif" alt="The Conversation" width="1" height="1" />
A book-length thought experiment uses math to investigate some of life’s big questions.Maggie Villiger, Senior Science + Technology EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2076022023-08-08T12:29:39Z2023-08-08T12:29:39ZLooking back toward cosmic dawn − astronomers confirm the faintest galaxy ever seen<figure><img src="https://images.theconversation.com/files/540179/original/file-20230731-16129-x8ubg4.jpg?ixlib=rb-1.1.0&rect=10%2C12%2C1012%2C1019&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A phenomenon called gravitational lensing can help astronomers observe faint, hard-to-see galaxies. </span> <span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/chandra/images/abell-2744.html">NASA/STScI</a></span></figcaption></figure><p>The universe we live in is a transparent one, where light from stars and galaxies shines bright against a clear, dark backdrop. But this wasn’t always the case – in its early years, the universe was filled with a fog of hydrogen atoms that obscured light from the earliest stars and galaxies. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Clouds interrupted by bright spots" src="https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=477&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=477&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=477&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=599&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=599&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541497/original/file-20230807-25-kgcqd9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=599&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 early universe was filled with a fog made up of hydrogen atoms until the first stars and galaxies burned it away.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/spitzer/multimedia/firststars-blue-20061218.html">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The intense ultraviolet light from the first generations of stars and galaxies is thought to have burned through the hydrogen fog, transforming the universe into what we see today. While previous generations of telescopes lacked the ability to study those early cosmic objects, astronomers are now using the <a href="https://webb.nasa.gov/">James Webb Space Telescope</a>’s superior technology to study the stars and galaxies that formed in the immediate aftermath of the Big Bang.</p>
<p>I’m an <a href="https://www.robertsborsani.com/">astronomer who studies the farthest galaxies</a> in the universe using the world’s foremost ground- and space-based telescopes. Using new observations from the Webb telescope and a phenomenon called gravitational lensing, my team <a href="https://doi.org/10.1038/s41586-023-05994-w">confirmed the existence</a> of the faintest galaxy currently known in the early universe. The galaxy, called JD1, is seen as it was when the universe was only 480 million years old, or 4% of its present age.</p>
<h2>A brief history of the early universe</h2>
<p>The first billion years of the universe’s life were a <a href="https://doi.org/10.1038/nature09527">crucial period in its evolution</a>. In the first moments after the Big Bang, matter and light were bound to each other in a hot, dense “soup” of <a href="https://theconversation.com/explainer-what-are-fundamental-particles-38339">fundamental particles</a>.</p>
<p>However, a fraction of a second after the Big Bang, the universe <a href="https://doi.org/10.1051/0004-6361/201833887">expanded extremely rapidly</a>. This expansion eventually allowed the universe to cool enough for light and matter to separate out of their “soup” and – some 380,000 years later – form hydrogen atoms. The hydrogen atoms appeared as an intergalactic fog, and with no light from stars and galaxies, the universe was dark. This period is known as the <a href="https://doi.org/10.1126/science.1085325">cosmic dark ages</a>.</p>
<p>The arrival of the first generations of stars and galaxies several hundred million years after the Big Bang bathed the universe in extremely hot UV light, which <a href="https://www.youtube.com/watch?v=dgXfTx2e2MA&ab_channel=djxatlanta">burned – or ionized – the hydrogen fog</a>. <a href="https://theconversation.com/after-our-universes-cosmic-dawn-what-happened-to-all-its-original-hydrogen-65527">This process</a> yielded the transparent, complex and beautiful universe we see today.</p>
<p>Astronomers like me call the first billion years of the universe – when this hydrogen fog was burning away – the <a href="https://doi.org/10.1038/nature09527">epoch of reionization</a>. To fully understand this time period, we study when the first stars and galaxies formed, what their main properties were and whether they were able to produce enough UV light to burn through all the hydrogen.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/dgXfTx2e2MA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A visual model showing the burning of hydrogen fog by UV light in the ‘reionization’ era. Ionized, or burned, regions are blue and translucent. Ionization fronts are red and white, and neutral regions are dark and opaque. Via djxatlanta on Youtube.</span></figcaption>
</figure>
<h2>The search for faint galaxies in the early universe</h2>
<p>The first step toward understanding the epoch of reionization is finding and confirming the distances to galaxies that astronomers think might be responsible for this process. Since light travels at a finite speed, it takes time to arrive to our telescopes, so astronomers <a href="https://theconversation.com/the-most-powerful-space-telescope-ever-built-will-look-back-in-time-to-the-dark-ages-of-the-universe-169603">see objects as they were in the past</a>.</p>
<p>For example, light from the center of our galaxy, the Milky Way, takes about 27,000 years to reach us on Earth, so we see it as it was 27,000 years in the past. That means that if we want to see back to the very first instants after the Big Bang (the universe is 13.8 billion years old), we have to look for objects at extreme distances.</p>
<p>Because galaxies residing in this time period are so far away, they appear extremely <a href="https://doi.org/10.1038/s41586-023-05994-w">faint and small</a> to our telescopes and emit most of their light in the infrared. This means astronomers need powerful infrared telescopes like Webb to find them. Prior to Webb, virtually all of the distant galaxies found by astronomers were exceptionally bright and large, simply because our telescopes weren’t sensitive enough to see the fainter, smaller galaxies. </p>
<p>However, it’s the latter population that are far more numerous, representative and likely to be the main drivers to the reionization process, not the bright ones. So, these faint galaxies are the ones astronomers need to study in greater detail. It’s like trying to understand the evolution of humans by studying entire populations rather than a few very tall people. By allowing us to see faint galaxies, Webb is opening a new window into studying the early universe.</p>
<h2>A typical early galaxy</h2>
<p>JD1 is one such “typical” faint galaxy. It was <a href="https://doi.org/10.1088/2041-8205/793/1/L12">discovered in 2014 with the Hubble Space Telescope</a> as a suspect distant galaxy. But Hubble didn’t have the capabilities or sensitivity to confirm its distance – it could make only an educated guess.</p>
<p>Small and faint nearby <a href="https://doi.org/10.48550/arXiv.2303.15431">galaxies can sometimes be mistaken as distant ones</a>, so astronomers need to be sure of their distances before we can make claims about their properties. Distant galaxies therefore remain “candidates” until they are confirmed. The Webb telescope finally has the capabilities to confirm these, and JD1 was one of the first major confirmations by Webb of an extremely distant galaxy candidate found by Hubble. This confirmation ranks it as <a href="https://doi.org/10.1038/s41586-023-05994-w">the faintest galaxy yet seen in the early universe</a>.</p>
<p>To confirm JD1, an international team of astronomers and I used Webb’s near-infrared spectrograph, <a href="https://jwst.nasa.gov/content/observatory/instruments/nirspec.html">NIRSpec</a>, to obtain an infrared spectrum of the galaxy. The spectrum allowed us to pinpoint the distance from Earth and determine its age, the number of young stars it formed and the amount of dust and heavy elements that it produced.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bright lights (galaxies and a few stars) against a dark backdrop of sky. One faint galaxy is shown in a magnified box as a dim smudge." src="https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=755&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=755&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536357/original/file-20230707-23-dlm4qh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=755&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 sky full of galaxies and a few stars. JD1, pictured in a zoomed-in box, is the faintest galaxy yet found in the early universe.</span>
<span class="attribution"><span class="source">Guido Roberts-Borsani/UCLA; original images: NASA, ESA, CSA, Swinburne University of Technology, University of Pittsburgh, STScI</span></span>
</figcaption>
</figure>
<h2>Gravitational lensing, nature’s magnifying glass</h2>
<p>Even for Webb, JD1 would be impossible to see without a helping hand from nature. JD1 is located behind a large cluster of nearby galaxies, called <a href="https://webbtelescope.org/contents/media/images/2019/20/4376-Image">Abell 2744</a>, whose combined gravitational strength bends and amplifies the light from JD1. This effect, known as gravitational lensing, makes JD1 appear larger and 13 times brighter than it ordinarily would. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Rsx0AGQhQvs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Large galaxies can warp and distort light traveling around them. This video shows how this process, called gravitational lensing, works.</span></figcaption>
</figure>
<p>Without gravitational lensing, astronomers would not have seen JD1, even with Webb. The combination of JD1’s gravitational magnification and new images from another one of Webb’s near-infrared instruments, <a href="https://webb.nasa.gov/content/observatory/instruments/nircam.html">NIRCam</a>, made it possible for our team to study the galaxy’s structure in unprecedented detail and resolution. </p>
<p>Not only does this mean we as astronomers can study the inner regions of early galaxies, it also means we can start determining whether such early galaxies were small, compact and isolated sources, or if they were merging and interacting with nearby galaxies. By studying these galaxies, we are tracing back to the building blocks that shaped the universe and gave rise to our cosmic home.</p><img src="https://counter.theconversation.com/content/207602/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program JWST-ERS-1324, and the authors acknowledge financial support from NASA through grant JWST-ERS-1324.</span></em></p>The universe used to be filled with a hydrogen fog, before early stars and galaxies burned through the haze. Astronomers are studying galaxies that tell them about this period in the early universe.Guido Roberts-Borsani, Postdoctoral Researcher in Astrophysics, University of California, Los AngelesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2058912023-07-26T12:15:06Z2023-07-26T12:15:06ZMeasuring helium in distant galaxies may give physicists insight into why the universe exists<figure><img src="https://images.theconversation.com/files/537554/original/file-20230714-21948-g2t785.jpg?ixlib=rb-1.1.0&rect=60%2C0%2C6698%2C4489&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">New measurements from Japan's Subaru telescope have helped researchers study the matter-antimatter asymmetry problem. </span> <span class="attribution"><a class="source" href="https://media.gettyimages.com/id/1335056886/photo/andromeda-galaxy-surrounded-by-stars.jpg?s=612x612&w=0&k=20&c=yhgVDZmt3gODQx_vm9nzfweVT8-WzwwOpxJehbnynrI=">Javier Zayas Photography/Moment via Getty</a></span></figcaption></figure><p>When theoretical physicists like myself say that we’re studying why the universe exists, we sound like philosophers. But new data collected by researchers using Japan’s <a href="https://subarutelescope.org/en/">Subaru telescope</a> has revealed insights into that very question.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cylindrical building sitting on a cliff overlooking a sunset." src="https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/538069/original/file-20230718-7668-yp1ts1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Japan’s Subaru telescope, located on Mauna Kea in Hawaii.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Subaru_Telescope._Mauna_Kea_Summit_-_panoramio.jpg">Panoramio/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><a href="https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang">The Big Bang</a> <a href="https://theconversation.com/how-could-an-explosive-big-bang-be-the-birth-of-our-universe-128430">kick-started the universe</a> as we know it 13.8 billion years ago. <a href="https://www.slac.stanford.edu/pubs/beamline/26/1/26-1-sather.pdf">Many theories</a> in particle physics suggest that for all the matter created at the universe’s conception, an equal amount of antimatter should have been created alongside it. Antimatter, like matter, has mass and takes up space. However, antimatter particles exhibit the opposite properties of their corresponding matter particles. </p>
<p>When pieces of matter and antimatter collide, they <a href="https://home.cern/science/physics/matter-antimatter-asymmetry-problem">annihilate each other in a powerful explosion</a>, leaving behind only energy. The puzzling thing about theories that predict the creation of an equal balance of matter and antimatter is that if they were true, the two would have totally annihilated each other, leaving the universe empty. So there must have been more matter than antimatter at the birth of the universe, because the universe isn’t empty – it’s full of stuff that’s made of matter like galaxies, stars and planets. A little bit of antimatter <a href="https://www.energy.gov/science/doe-explainsantimatter">exists around us</a>, but it is very rare. </p>
<p>As a <a href="https://inspirehep.net/authors/2064347">physicist working on Subaru data</a>, I’m interested in this so-called <a href="https://home.cern/science/physics/matter-antimatter-asymmetry-problem">matter-antimatter asymmetry problem</a>. In our <a href="https://doi.org/10.1103/PhysRevLett.130.131001">recent study</a>, my collaborators and I found that the telescope’s new measurement of the amount and type of helium in faraway galaxies may offer a solution to this long-standing mystery.</p>
<h2>After the Big Bang</h2>
<p>In the first milliseconds after the Big Bang, the universe was hot, dense and full of elementary particles like protons, neutrons and electrons <a href="https://www.space.com/25126-big-bang-theory.html">swimming around in a plasma</a>. Also present in this pool of particles were <a href="https://theconversation.com/explainer-the-elusive-neutrino-431">neutrinos</a>, which are very tiny, weakly interacting particles, and antineutrinos, their antimatter counterparts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image showing a burst of light and color against black space and stars." src="https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537553/original/file-20230714-27-ymcvpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Big Bang created fundamental particles that make up other particles like protons and neutrons. Neutrinos are another type of fundamental particle.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/big-bang-conceptual-image-royalty-free-illustration/639549057?phrase=the%20big%20bang">Alfred Pasieka/Science Photo Library via Getty Images</a></span>
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<p>Physicists believe that just one second after the Big Bang, the nuclei of light <a href="https://theconversation.com/after-our-universes-cosmic-dawn-what-happened-to-all-its-original-hydrogen-65527">elements like hydrogen</a> and helium began to form. This process is known as <a href="https://w.astro.berkeley.edu/%7Emwhite/darkmatter/bbn.html">Big Bang Nucleosynthesis</a>. The nuclei formed were about <a href="https://science.howstuffworks.com/dictionary/astronomy-terms/big-bang-theory5.htm">75% hydrogen nuclei and 24% helium nuclei</a>, plus small amounts of heavier nuclei. </p>
<p>The physics community’s <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/bbnuc.html">most widely accepted theory</a> on the formation of these nuclei tells us that neutrinos and antineutrinos played a fundamental role in the creation of, in particular, helium nuclei. </p>
<p>Helium creation in the early universe happened in a two-step process. First, neutrons and protons converted from one to the other in a <a href="https://ned.ipac.caltech.edu/level5/March04/Steigman3/Steigman2.html">series of processes</a> involving neutrinos and antineutrinos. As the universe cooled, these processes stopped and the <a href="https://ned.ipac.caltech.edu/level5/March04/Steigman3/Steigman2.html">ratio of protons to neutrons was set</a>. </p>
<p>As theoretical physicists, we can create models to test how the ratio of protons to neutrons depends on the relative number of neutrinos and antineutrinos in the early universe. If <a href="https://doi.org/10.1103/PhysRevLett.130.131001">more neutrinos were present</a>, then our models show more protons and fewer neutrons would exist as a result. </p>
<p>As the universe cooled, hydrogen, helium and other elements <a href="https://ned.ipac.caltech.edu/level5/March04/Steigman3/Steigman2.html">formed from these protons and neutrons</a>. Helium is made up of two protons and two neutrons, and hydrogen is just one proton and no neutrons. So the fewer the neutrons available in the early universe, the less helium would be produced.</p>
<p>Because the nuclei formed during Big Bang Nucleosynthesis <a href="https://doi.org/10.1103/PhysRevLett.130.131001">can still be observed today</a>, scientists can infer how many neutrinos and antineutrinos were present during the early universe. They do this by looking specifically at galaxies that are rich in light elements like hydrogen and helium.</p>
<figure class="align-center ">
<img alt="A diagram showing how protons and neutrons form helium atoms." src="https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537555/original/file-20230714-25-rbf648.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In a series of high-energy particle collisions, elements like helium are formed in the early universe. Here, D stands for deuterium, an isotope of hydrogen with one proton and one neutron, and γ stands for photons, or light particles. In the series of chain reactions shown, protons and neutrons fuse to form deuterium, then these deuterium nuclei fuse to form helium nuclei.</span>
<span class="attribution"><span class="source">Anne-Katherine Burns</span></span>
</figcaption>
</figure>
<h2>A clue in helium</h2>
<p>Last year, the Subaru Collaboration – a group of Japanese scientists working on the Subaru telescope – released data on <a href="https://doi.org/10.3847/1538-4357/ac9ea1">10 galaxies</a> far outside of our own that are almost exclusively made up of hydrogen and helium. </p>
<p>Using a technique that allows researchers to distinguish different elements from one another <a href="https://theconversation.com/explainer-seeing-the-universe-through-spectroscopic-eyes-37759">based on the wavelengths of light</a> observed in the telescope, the Subaru scientists determined exactly how much helium exists in each of these 10 galaxies. Importantly, they found less helium than the previously accepted theory predicted. </p>
<p>With this new result, my collaborators and I worked backward to find the <a href="https://doi.org/10.1103/PhysRevLett.130.131001">number of neutrinos and antineutrinos</a> necessary to produce the helium abundance found in the data. Think back to your ninth grade math class when you were asked to solve for “X” in an equation. What my team did was essentially the more sophisticated version of that, where our “X” was the number of neutrinos or antineutrinos.</p>
<p>The previously accepted theory predicted that there should be the same number of neutrinos and antineutrinos in the early universe. However, when we tweaked this theory to give us a prediction that matched the new data set, <a href="https://doi.org/10.1103/PhysRevLett.130.131001">we found that</a> the number of neutrinos was greater than the number of antineutrinos.</p>
<h2>What does it all mean?</h2>
<p>This analysis of new helium-rich galaxy data has a far-reaching consequence – it can be used to explain the asymmetry between matter and antimatter. The Subaru data points us directly to a source for that imbalance: neutrinos. In this study, my collaborators and I proved that this new measurement of helium is consistent with there being more neutrinos then antineutrinos in the early universe. Through <a href="https://doi.org/10.1103/PhysRevLett.130.131001">known and likely particle physics processes</a>, the asymmetry in the neutrinos could propagate into an asymmetry in all matter. </p>
<p>The result of our study is a common type of result in the theoretical physics world. Basically, we discovered a viable way in which the matter-antimatter asymmetry could have been produced, but that doesn’t mean it definitely was produced in that way. The fact that the data fits with our theory is a hint that the theory we’ve proposed might be the correct one, but this fact alone doesn’t mean that it is. </p>
<p>So, are these tiny little neutrinos the key to answering the age old question, “Why does anything exist?” According to this new research, they just might be.</p><img src="https://counter.theconversation.com/content/205891/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anne-Katherine Burns does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The way particles interacted while the universe was forming seconds after the Big Bang could explain why the universe exists the way it does – a physicist explains matter-antimatter asymmetry.Anne-Katherine Burns, Ph.D. Candidate in Theoretical Particle Physics, University of California, IrvineLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2086212023-07-03T20:07:29Z2023-07-03T20:07:29ZAstronomers see ancient galaxies flickering in slow motion due to expanding space<figure><img src="https://images.theconversation.com/files/535172/original/file-20230702-177413-sljzpk.png?ixlib=rb-1.1.0&rect=0%2C22%2C3840%2C2132&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA / ESA / J. Olmsted (STScI)</span></span></figcaption></figure><p>According to our best understanding of physics, the fact space is expanding should influence the apparent flow of time, with the distant Universe appearing to run in slow motion.</p>
<p>But observations of highly luminous and variable galaxies, known as quasars, have failed to reveal this cosmic time dilation – until now. </p>
<p>In a <a href="https://doi.org/10.1038/s41550-023-02029-2">new study</a> published in Nature Astronomy, we use two decades of observation to untangle the complex flickering of almost 200 quasars. Buried within this flickering is the imprint of expanding space, with the Universe appearing to be ticking five times slower when it was only a billion years old. </p>
<p>This shows quasars obey the rules of the cosmos, putting to bed the idea they represented a <a href="https://phys.org/news/2010-04-discovery-quasars-dont-dilation-mystifies.html">challenge to modern cosmology</a>. </p>
<h2>Time is a funny thing</h2>
<p>In 1905, Albert Einstein, through his special theory of relativity, told us the speed of clocks’ ticking is relative, dependent on how the clocks are moving. In his 1915 general theory, he told us gravity too can influence the relative rates of clock ticks.</p>
<p><a href="https://articles.adsabs.harvard.edu/pdf/1939ApJ....90..634W">By the 1930s</a>, physicists realised the expanding space of the cosmos, which is described in the language of Einstein’s general relativity, also influences the universe of ticks and tocks.</p>
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Read more:
<a href="https://theconversation.com/timeline-the-history-of-gravity-54528">Timeline: the history of gravity</a>
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<p>Due to the finite speed of light, as we look through our telescopes, we are peering into the past. The further we look, the further back into the life of the Universe we see. But in our expanding Universe, the further back we look, the more time space has had to stretch, and the more the relative nature of clock ticks grows.</p>
<p>The prediction of Einstein’s mathematics is clear: we should see the distant universe playing out in slow motion.</p>
<h2>Tick-tock supernova clock</h2>
<p>Measuring this slow-motion universe is difficult, as nature does not provide standard clocks across the cosmos whose relative ticks could be compared. </p>
<p>It took until the 1990s for astronomers to discover and understand the tick of <a href="https://arxiv.org/pdf/astro-ph/9707260.pdf">suitable clocks</a>: a particular kind of exploding star, a supernova. Each supernova explosion was surprisingly similar, brightening rapidly and then fading away over a matter of weeks. </p>
<p>Supernovae are similar, but not identical, meaning their rate of brightening and fading was not a standard clock. But by the close of the 20th century, astronomers were taking another look at these exploding stars, using them <a href="https://supernova.lbl.gov">to chart the expansion of the Universe</a>. (This expansion turned out to be accelerating, leading to the <a href="https://www.nobelprize.org/prizes/physics/2011/press-release/">unexpected discovery of dark energy</a>.)</p>
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Read more:
<a href="https://theconversation.com/from-dark-gravity-to-phantom-energy-whats-driving-the-expansion-of-the-universe-60433">From dark gravity to phantom energy: what's driving the expansion of the universe?</a>
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<p>To achieve this goal, astronomers had to iron out peculiarities of each supernova, putting them on an equal footing, matching them to a standard intrinsic brightness and a standard clock. </p>
<p>They found the flash of more distant supernovae was stretched precisely in line with Einstein’s predictions. The most distant observed supernovae, exploding when the Universe was half its present age, brightened and faded <a href="https://arxiv.org/pdf/0804.3595.pdf">twice as slowly as more recent supernovae</a>.</p>
<h2>The trouble with quasars</h2>
<p>Supernovae are not the only variable objects in the cosmos. </p>
<p><a href="https://www.wired.com/2010/08/0805first-quasar-located/">Quasars were discovered in the 1960s</a>, and are thought to be supermassive black holes, some many billions of times more massive than the Sun, lurking at the hearts of galaxies. Matter swirls around these black holes on its journey to oblivion inside, heating up and glowing brightly as it does so.</p>
<p>Quasars are <a href="https://phys.org/news/2023-05-astronomers-explore-luminous-quasar.html#:%7E:text=J1144%20was%20detected%20in%20June,a%20redshift%20greater%20than%200.4.">extremely bright</a>, some burning furiously when the <a href="https://phys.org/news/2023-02-hundreds-high-redshift-quasars.html">Universe was an infant</a>. Quasars are also variable, varying in luminosity as matter turbulently tumbles on its way to destruction. </p>
<p>Because quasars are so bright, we can see them at much greater distances than supernovae. So the impact of expanding space and time dilation should be more pronounced.</p>
<p>However, searches for the expected signal have turned up blank. Samples of hundreds of quasars observed over decades definitely varied, but it seemed that the variations of those nearby and those far away were identical. </p>
<p>Some suggested that this demonstrated that the variability of quasars is not intrinsic but is instead due to black holes scattered through the Universe, <a href="https://arxiv.org/pdf/2204.09143.pdf">magnifying some quasars</a> by the action of gravity. More outlandishly, others have claimed that the lack of the expected cosmological signal is a clear sign that we have <a href="https://www.mdpi.com/2218-1997/1/3/307">cosmology all wrong</a> and need to go back to the drawing board. </p>
<h2>New data, new approaches</h2>
<p>In 2023, a new set of quasar data was <a href="https://arxiv.org/pdf/2201.02762.pdf">published</a>. This presented 190 quasars originally identified in the highly successful Sloan Digital Sky Survey but observed over two decades in multiple colours – green, red and infrared light. </p>
<p>The data sampling was mixed, with lots of observations over some times, and less over others. But the wealth of this data meant the astronomers, led by graduate student <a href="https://astro.illinois.edu/directory/profile/stone28">Zachary Stone at the University of Illinois</a>, could statistically characterise each quasar’s variability as what is known as a “<a href="https://arxiv.org/pdf/1312.3966.pdf">damped random walk</a>”. This characterisation assigned a time scale, a tick, to each quasar.</p>
<p>Like each supernova, each quasar is different, and the observed variability can depend upon their intrinsic properties. But with this new data, we could match similar quasars with each other, removing the impact of these differences. As had been done for supernovae before, we had standardised the tick-tock of quasars.</p>
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<p>The only remaining influence on the observed variability of quasars was the expansion of space, and we unambiguously revealed this signature. Quasars obeyed the rules of the Universe exactly as Einstein’s theory predicted. </p>
<p>Due to their brightness, however, the influence of this cosmic time dilation could be seen much further. The most distant quasars, seen when the Universe was only a tenth of its present age, were ticking away time five times more slowly than today.</p>
<p>At its heart, this is a story about how <a href="https://scitechdaily.com/einstein-proven-right-yet-again-theory-of-general-relativity-passes-a-range-of-precise-tests/">Einstein is right again</a>, and how his mathematical description of the cosmos is the best we have. It puts to rest ideas of a sea of cosmic black holes, or that we truly inhabit a static, unchanging universe. And this is precisely how science advances.</p><img src="https://counter.theconversation.com/content/208621/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Geraint Lewis receives funding from the Australian Research Council.</span></em></p>Bright, flickering galaxies called quasars were thought to pose a problem for our understanding of the cosmos – but new research shows Einstein was right yet again.Geraint Lewis, Professor of Astrophysics, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2088152023-06-30T20:57:15Z2023-06-30T20:57:15ZA subtle symphony of ripples in spacetime – astronomers use dead stars to measure gravitational waves produced by ancient black holes<figure><img src="https://images.theconversation.com/files/535073/original/file-20230630-14361-kaueuz.jpg?ixlib=rb-1.1.0&rect=38%2C76%2C4547%2C2919&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Black holes and other massive objects create ripples in spacetime when they merge.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/black-holes-illustration-royalty-free-illustration/1088377636?phrase=gravitational+waves&adppopup=true">Victor de Schwanburg/Science Photo Library via Getty Images</a></span></figcaption></figure><p>An international team of astronomers has detected a <a href="https://doi.org/10.3847/2041-8213/acdac6">faint signal</a> of gravitational waves reverberating through the universe. By using dead stars as a giant network of <a href="https://iopscience.iop.org/collections/apjl-230623-245-Focus-on-NANOGrav-15-year">gravitational wave detectors</a>, the collaboration – called <a href="https://nanograv.org/">NANOGrav</a> – was able to measure a low-frequency hum from a chorus of <a href="https://theconversation.com/why-astrophysicists-are-over-the-moon-about-observing-merging-neutron-stars-84957">ripples of spacetime</a>.</p>
<p>I’m an <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">astronomer</a> who studies and has written about <a href="https://wwnorton.com/books/9780393343861">cosmology</a>, <a href="https://wwnorton.com/books/9780393357509">black holes</a> and <a href="https://www.penguinrandomhouse.com/books/718149/worlds-without-end-by-chris-impey/">exoplanets</a>. I’ve researched the <a href="https://www.cambridge.org/core/journals/proceedings-of-the-international-astronomical-union/article/survey-of-agn-and-supermassive-black-holes-in-the-cosmos-survey/B1ADC49E96B9D865D55188EC839ED033">evolution of supermassive black holes</a> using the Hubble Space telescope.</p>
<p>Though members of the team behind this new discovery aren’t yet certain, they strongly suspect that the background hum of gravitational waves they measured was caused by countless ancient merging events of supermassive black holes.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zsDOqLWuWQ4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Pulsars are spinning dead stars that emit strong beams of radiation and can be used as accurate cosmic clocks.</span></figcaption>
</figure>
<h2>Using dead stars for cosmology</h2>
<p><a href="https://www.ligo.caltech.edu/page/what-are-gw">Gravitational waves</a> are ripples in spacetime caused by massive accelerating objects. Albert Einstein predicted their existence in his <a href="https://theconversation.com/why-does-gravity-pull-us-down-and-not-up-162141">general theory of relativity</a>, in which he hypothesized that when a gravitational wave passes through space, it makes the space shrink then expand periodically.</p>
<p>Researchers first detected direct evidence of gravitational waves in 2015, when the <a href="https://theconversation.com/gravitational-wave-detector-ligo-is-back-online-after-3-years-of-upgrades-how-the-worlds-most-sensitive-yardstick-reveals-secrets-of-the-universe-204339">Laser Interferometer Gravitational-Wave Observatory, known as LIGO</a>, <a href="https://theconversation.com/what-happens-when-ligo-texts-you-to-say-its-detected-one-of-einsteins-predicted-gravitational-waves-53259">picked up a signal</a> from a <a href="https://www.ligo.caltech.edu/detection">pair of merging black holes</a> that had traveled 1.3 billion light-years to reach Earth.</p>
<p>The NANOGrav collaboration is also trying to detect spacetime ripples, but on an interstellar scale. The team <a href="https://theconversation.com/fifty-years-ago-jocelyn-bell-discovered-pulsars-and-changed-our-view-of-the-universe-88083">used pulsars</a>, rapidly spinning dead stars that emit a beam of radio emissions. Pulsars are functionally similar to a lighthouse – as they spin, their beams can sweep across the Earth at <a href="https://nanograv.org/science/topics/pulsars-cosmic-clocks">regular intervals</a>.</p>
<p>The NANOGrav team used pulsars that <a href="https://doi.org/10.3847/2041-8213/acda9a">rotate incredibly fast</a> – up to 1,000 times per second – and these pulses can be timed like the ticking of an <a href="https://nanograv.org/science/topics/pulsars-cosmic-clocks">extremely accurate cosmic clock</a>. As gravitational waves sweep past a pulsar at the speed of light, the waves will very slightly expand and contract the distance between the pulsar and the Earth, ever so slightly changing the time between the ticks. </p>
<p>Pulsars are such accurate clocks that it is possible to measure their ticking with an accuracy to within 100 nanoseconds. That lets astronomers calculate the distance between a pulsar and Earth to within <a href="https://astronomy.swin.edu.au/cosmos/p/Pulsar+Timing">100 feet</a> (30 meters). Gravitational waves change the distance between these pulsars and Earth by tens of miles, making pulsars easily sensitive enough to detect this effect.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A giant, white reflecting dish with a receiver." src="https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535071/original/file-20230630-17-5kb781.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">The NANOGrav team used a number of radio telescopes, including the Green Bank Telescope in West Virginia, to listen to pulsars for 15 years.</span>
<span class="attribution"><a class="source" href="https://public.nrao.edu/gallery/green-bank-telescope/">NRAO/AUI/NSF</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Finding a hum within cacophony</h2>
<p>The first thing the NANOGrav team had to do was control for the <a href="https://doi.org/10.3847/2041-8213/acda88">noise in its cosmic gravitational wave detector</a>. This included <a href="https://theconversation.com/radio-interference-from-satellites-is-threatening-astronomy-a-proposed-zone-for-testing-new-technologies-could-head-off-the-problem-199353">noise in the radio receivers</a> it used and subtle astrophysics that affect the behavior of pulsars. Even accounting for these effects, the team’s approach was not sensitive enough to detect gravitational waves from <a href="https://doi.org/10.48550/arXiv.2306.16222">individual supermassive black hole binaries</a>. However, it had enough sensitivity to detect the sum of all the massive black hole mergers that have occurred anywhere in the universe since the Big Bang – as many as a million overlapping signals.</p>
<p>In a musical analogy, it is like standing in a busy downtown and hearing the faint sound of a symphony somewhere in the distance. You can’t pick out a single instrument because of the noise of the cars and the people around you, but you can hear the hum of a hundred instruments. The team had to tease out the signature of this <a href="https://www.space.com/gravitational-wave-background-universe-1st-detection">gravitational wave “background”</a> from other competing signals.</p>
<p>The team was able to detect this symphony by measuring a network of 67 different pulsars for 15 years. If some disruption in the ticking of one pulsar was due to gravitational waves from the distant universe, all the pulsars the team was watching would be affected in a similar way. On June 28, 2023, the team published <a href="https://www.nytimes.com/2023/06/28/science/astronomy-gravitational-waves-nanograv.html">four papers</a> describing its project and the evidence it found of the gravitational wave background.</p>
<p>The hum the NANOGrav collaboration found is produced from the merging of black holes that are billions of times more massive than the Sun. These black holes spin around one another very slowly and produce gravitational waves with <a href="https://www.scienceinschool.org/article/2017/gravitational-waves-taxonomy/">frequencies of one-billionth of a hertz</a>. That means the spacetime ripples have an oscillation every few decades. This slow oscillation of the wave is the reason the team needed to rely on the incredibly accurate timekeeping of pulsars.</p>
<p>These gravitational waves are different from <a href="https://theconversation.com/ligo-announcement-vaults-astronomy-out-of-its-silent-movie-era-into-the-talkies-85727">the waves LIGO can detect</a>. LIGO’s signals are produced when two black holes <a href="https://media.ligo.northwestern.edu/gallery/mass-plot">10 to 100 times the mass of the Sun</a> merge into one rapidly spinning object, creating gravitational waves that oscillate hundreds of times per second.</p>
<p>If you think of black holes as a tuning fork, the smaller the event, the faster the tuning fork vibrates and the higher the pitch. LIGO detects gravitational waves that “ring” in the audible range. The black hole mergers the NANOGrav team has found “ring” with a frequency billions of times too low to hear. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A star-filled sky with many spiral galaxies." src="https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=610&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=610&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=610&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=767&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=767&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535068/original/file-20230630-15-bjzonq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=767&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The James Webb Space Telescope has allowed astronomers to peer back in time and study the first galaxies to form after the Big Bang.</span>
<span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2022/038/01G7JGTH21B5GN9VCYAHBXKSD1">NASA, ESA, CSA, STScI</a></span>
</figcaption>
</figure>
<h2>Giant black holes in the early universe</h2>
<p>Astronomers have long been interested in <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-explains-the-stunning-newly-released-first-images-186800">studying how stars and galaxies first emerged</a> in the aftermath of the Big Bang. This new finding from the NANOGrav team is like adding another color – gravitational waves – to the picture of the early universe that is just starting to emerge, in large part thanks to <a href="https://theconversation.com/the-james-webb-space-telescope-is-finally-ready-to-do-science-and-its-seeing-the-universe-more-clearly-than-even-its-own-engineers-hoped-for-184989">the James Webb Space Telescope</a>.</p>
<p>A major scientific goal of the <a href="https://webbtelescope.org/home">James Webb Space Telescope</a> is to help researchers study how the first stars and galaxies formed after the Big Bang. To do this, James Webb was designed to detect the faint light from incredibly distant stars and galaxies. The farther away an object is, the longer it takes the light to get to Earth, so James Webb is effectively a time machine that can peer back over 13.5 billion years to see light from the <a href="https://webb.nasa.gov/content/science/firstLight.html">first stars and galaxies</a> in the universe. </p>
<p>It has been very successful in the quest, having found <a href="https://www.space.com/james-webb-space-telescope-galaxies-early-universe-first-light">hundreds of galaxies</a> that flooded the universe with light in the first 700 million years after the big bang. The telescope has also detected the <a href="https://www.livescience.com/james-webb-space-telescope-discovers-oldest-black-hole-in-the-universe-a-cosmic-monster-ten-million-times-heavier-than-the-sun">oldest black hole</a> in the universe, located at the center of a galaxy that formed just 500 million years after the Big Bang.</p>
<p>These findings are challenging existing theories of the evolution of the universe. </p>
<p>It takes a long time to <a href="https://www.smithsonianmag.com/smart-news/webb-telescope-finds-evidence-of-massive-galaxies-that-defy-theories-of-the-early-universe-180981689/">grow a massive galaxy</a>. Astronomers know that supermassive black holes <a href="https://theconversation.com/say-hello-to-sagittarius-a-the-black-hole-at-the-center-of-the-milky-way-galaxy-183008">lie at the center of every galaxy</a> and have mass proportional to their host galaxies. So these ancient galaxies almost certainly have <a href="https://ec.europa.eu/research-and-innovation/en/horizon-magazine/how-did-supermassive-black-holes-grow-so-fast">the correspondingly massive black hole</a> in their centers.</p>
<p>The problem is that the objects James Webb has been finding are far bigger than current theory says they should be. </p>
<p>These new results from the NANOGrav team emerged from astronomers’ first opportunity to listen to the gravitational waves of the ancient universe. The findings, while tantalizing, <a href="https://doi.org/10.1038/d41586-023-02167-7">aren’t quite strong enough to claim a definitive discovery</a>. That will likely change, as the team has expanded its pulsar network <a href="https://nanograv.org/news/15yrRelease">to include 115 pulsars</a> and should get results from this next survey around 2025. As James Webb and other research challenges existing theories of how galaxies evolved, the ability to study the era after the Big Bang using gravitational waves could be an invaluable tool.</p><img src="https://counter.theconversation.com/content/208815/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation.</span></em></p>Astronomers have for the first time detected the background hum of gravitational waves likely caused by merging black holes.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2076072023-06-26T04:28:01Z2023-06-26T04:28:01ZNothing is not nothing: how a scientist set out to sing the story of our origins<figure><img src="https://images.theconversation.com/files/531513/original/file-20230613-28-c47rc9.jpg?ixlib=rb-1.1.0&rect=28%2C0%2C4833%2C4500&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.jwst.nasa.gov/content/webbLaunch/assets/images/firstImages/image3-StellarDeath/STSCI-J-p22033b-4000px.jpg">JWST / NASA</a></span></figcaption></figure><p>At the close of the 18th century, the Austrian composer Joseph Haydn wrote one of his masterpieces: an oratorio – a large concert piece for orchestra, choir and solo singers – entitled The Creation, with a libretto based on the biblical story of the creation of the world.</p>
<p>More than 200 years later, our understanding of how our world began has changed spectacularly. As both a scientist and a chorister, I have waited for decades for someone to write a new oratorio that tells of the origin of the Universe, of life, of species, and of humanity, based on science.</p>
<p>But nobody ever did, although composer Alan Williams, librettist Philip Goulding and astrophysicist Tim O'Brien wrote an oratorio called Wonder for the International Year of Astronomy in 2009 that reflected scientific understanding of the birth of the Universe.</p>
<p>So – with the help of a poet colleague, a composer and the choir I sing in – I set out to tell this story of origins with music and beautiful words and images from cosmology, molecular biology, evolutionary genetics, ecology and anthropology.</p>
<h2>Science is beautiful</h2>
<p>Rereading my old books by the masters of these fields brought back to me the awe and wonder inspired by the discoveries of the past century.</p>
<p>What could be more awesome than the creation of a universe from nothing? Or the creation of the molecules of life in a warm pond or hydrothermal vent? </p>
<p>What could be more beautiful than the origin of species of increasing complexity, including our own? What could be more important than conserving our planet and understanding ourselves and our place in the Universe?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/did-life-evolve-more-than-once-researchers-are-closing-in-on-an-answer-205678">Did life evolve more than once? Researchers are closing in on an answer</a>
</strong>
</em>
</p>
<hr>
<p>So why isn’t the general public in love with science? When I lived in a commune 50 years ago, the very smart sociologists, psychologists and teachers I lived with would deride my passion. <em>Science is hard and boring. Science is downright dangerous. Science is only good for inventing gadgets.</em></p>
<p>In 1959, the English novelist and chemist C.P. Snow wrung his hands at the existence of “<a href="https://en.wikipedia.org/wiki/The_Two_Cultures">two cultures</a>” that don’t talk to each other. Despite the explosion of scientific advances, I’m not sure we have advanced much in the integration of science into our culture.</p>
<p>My early experiences began a lifelong search for ways to express the beauty and simplicity of science. What could touch us more profoundly than music?</p>
<h2>We are what we sing</h2>
<p>Humans of all ages and cultures have sung their deepest desires, hopes and fears. There’s even a <a href="https://www.psychologytoday.com/us/blog/your-musical-self/201209/which-came-first-music-or-language#:%7E:text=Music%20did%20not%20emerge%20as,interactions%20between%20music%20and%20language">theory</a> that song evolved before language.</p>
<p>Religion uses music to foster community and bring comfort and certainty to our uncertain lives. For centuries, beliefs have been fostered and reinforced by constant repetition of a credo in one form or another.</p>
<p>As a chorister, I have sung dozens of masses, requiems and oratorios, by Bach, Brahms, Mozart, Berlioz, Faure, Britten and more. I think these classics are the most gorgeous music in the world, and I love singing them.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illuminated manuscript showing scenes from the biblical creation story." src="https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=310&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=310&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=310&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=389&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=389&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533912/original/file-20230626-101831-8bzn3y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=389&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 biblical story of creation has inspired artists for millennia, but scientific origin stories have been less successful at capturing the imagination.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/The_Creation_(Haydn)#/media/File:The_Creation_in_L'Antiquité_Judaïque_-_Google_Art_Project.jpg">Wikimedia</a></span>
</figcaption>
</figure>
<p>But the ideas in the librettos were developed centuries ago. </p>
<p>When I first thought of writing an update, the idea seemed preposterous. How could an evolutionary geneticist with little formal musical training ever conceive, let alone write, the libretto for a major new work? </p>
<p>Up until then I had written 462 scientific articles, but only one poem – and that was 65 years earlier.</p>
<h2>Nothing is not nothing</h2>
<p>I teamed up with my fellow chorister, poet Leigh Hay, with support from Peter Bandy, the conductor of our choir (the <a href="http://www.hcs.asn.au">Heidelberg Choral Society</a>). Peter persuaded the Australian-born composer Nicholas Buc to write the music.</p>
<p>I had the first line in my head for years: “Nothing is not nothing.” I also had an idea for the finale “Man is the astronomer”, in which soloists ask despairing questions about humanity’s future, answered by the chorus’ reassurance that we humans, uniquely, can understand the universe and our place in it.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pencil sketch showing a double-helix structure." src="https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=766&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=766&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=766&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=962&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=962&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533915/original/file-20230626-105184-r64fub.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=962&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 early sketch of the double helix structure of DNA by Francis Crick.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/DNA#/media/File:Pencil_sketch_of_the_DNA_double_helix_by_Francis_Crick_Wellcome_L0051225.jpg">Francis Crick via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>To my surprise, the story unfolded in my head, in (rather unkempt) verse, and fell naturally into four sections: the universe, life, species, and humanity.</p>
<p>First the Big Bang and the cacophony of early Earth, and our planet forming into the “pale blue dot no bigger than Neil Armstrong’s thumb”.</p>
<p>Then the coalescence of molecules into self-replicating machines. Dramatising the discovery of the structure of DNA was fun to write: we interrupted excited half-sentences from Watson and Crick with a plaintive aria from Rosalind Franklin. </p>
<p>The steely beauty of DNA, the elegance of coding. The stuttering of mutation was obviously a fugue. For early life, I looked to famous Australian fossils.</p>
<p>Enter Darwin, singing calmly about his “one great law” against a chorus of hysterical hecklers. I had Bach’s St Matthew Passion in mind. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/decoding-the-music-masterpieces-handels-messiah-oratorio-composed-in-just-24-days-151092">Decoding the music masterpieces: Handel’s Messiah oratorio, composed in just 24 days</a>
</strong>
</em>
</p>
<hr>
<p>Then the desperation and frivolity of evolution; black and white moths, dancing lyrebirds, mechanically altruistic ants, speciating rock wallabies. Here I used my knowledge of famous Australian examples, including, alas, extinctions. A funeral march with tolling bell introduces the sixth extinction that is all our own.</p>
<figure class="align-center ">
<img alt="A photo of a black-and-white moth on a branch against a green background." src="https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533919/original/file-20230626-98671-niqdlt.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 changing colours of the black-and-white peppered moth are famous case of evolution in action.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>When I got to the rise of the third chimpanzee, the “dominant mammal” making a mess of our planet, I started feeling gloomy and had to rescue myself by writing a strong message of hope into the finale.</p>
<h2>Approaching the performance</h2>
<p>With the words done, Nick Buc’s music written, and a visual backdrop created by animator Drew Berry, we are now well into rehearsals with the 100 voices of the Heidelberg Choral Society, a 60-piece orchestra and four soloists, conducted by Peter Bandy.</p>
<p>The premier of Origins is set for July 18 at the Melbourne Recital Centre. Some 225 years after Haydn’s Creation first dazzled audiences with its religious vision, an oratorio on our origins based in science will have arrived. </p>
<hr>
<p><em>Clarification: this article has been amended to mention the 2009 oratorio Wonder, by Alan Williams, Philip Goulding and Tim O'Brien.</em></p><img src="https://counter.theconversation.com/content/207607/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenny Graves receives funding from the Australian Research Council. She is affiliated with the Heidelberg Choral Society. </span></em></p>Evolutionary geneticist Jenny Graves loves classical choral music, but grew tired of its biblical themes. So she set out to write an alternative based in science.Jenny Graves, Distinguished Professor of Genetics and Vice Chancellor's Fellow, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2065752023-06-18T20:08:12Z2023-06-18T20:08:12ZWhy is the sky dark at night? The 200-year history of a question that transformed our understanding of the Universe<figure><img src="https://images.theconversation.com/files/528678/original/file-20230527-19-36mvgt.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C3390%2C2841&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://esawebb.org/images/potm2301a/">ESA/Webb, NASA & CSA, A. Martel</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>As dawn rose over the German city of Bremen on May 7 1823, <a href="https://link.springer.com/referenceworkentry/10.1007/978-1-4419-9917-7_1031">Heinrich Olbers</a> put the finishing touches to an article that left his name in history. After the deaths of his wife and daughter, Dr Olbers had recently given up his work as an opthalmologist to devote himself to his nocturnal passions: the stars, the Moon, meteorites and comets. </p>
<p>Like many of his peers, Olbers trained himself in astronomy. He gained a <a href="https://en.wikisource.org/wiki/Popular_Science_Monthly/Volume_27/July_1885/Some_Self-Made_Astronomers">solid reputation</a> in the academic world and spent long nights observing the sky from the observatory on the second floor of his house.</p>
<p>On that morning, Olbers had come to a strange conclusion: based on all that was known about the Universe at that time, the night sky should not have been dark. In fact, the entire heavens should have been glowing as brightly as the Sun.</p>
<p>Olbers was <a href="https://ui.adsabs.harvard.edu/abs/1990IAUS..139....3H/abstract">not the first</a> to note this paradox. But his name is the one we attach to it today. The enigma of the night sky’s darkness has echoed down the centuries from Olbers and the poet Edgar Allan Poe to 20th-century astronomers and space probes today.</p>
<h2>Finite light in an infinite Universe</h2>
<p>Like many of his contemporaries, Olbers followed <a href="https://doi.org/10.1063/1.881049">Isaac Newton and René Descartes</a> in believing the Universe was infinite.</p>
<p>If the Universe were finite and static, the force of gravity should draw all the stars together at a central point. But if the Universe stretched on forever, gravitational forces would on average be balanced in all directions. </p>
<p>But Olbers realised this model of the cosmos was inconsistent with observations. In a limitless Universe filled with an infinite number of stars, wherever we look at night our gaze should land on the surface of a star, in much the same way as every line of sight in a forest ends at a tree.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of densely packed tree trunks in a forest" src="https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528760/original/file-20230529-17-zhp9e7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In an infinite forest, every line of sight leads to a tree trunk. In an infinite Universe, is the same true for stars?</span>
<span class="attribution"><a class="source" href="https://pxhere.com/fr/photo/1273647">PXHere</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>This is the problem Olbers raised in his <a href="https://www.biodiversitylibrary.org/page/2471191#page/163/mode/1up">paper</a> of May 7 1823: the cosmological model of the time suggested every point in the sky should be as bright as the surface of the Sun. There should be no night.</p>
<p>Olbers proposed a solution: the light from more distant stars was absorbed by dust or other material floating in space. The English astronomer John Herschel later pointed out this couldn’t be right, because anything absorbing that much light would eventually heat up enough to glow.</p>
<p>When Olbers died on March 2 1840, at the age of 81, the riddle we know today as Olbers’ paradox was unsolved.</p>
<h2>A poet’s intuition</h2>
<p>Eight years later, on the other side of the Atlantic Ocean, poet and writer Edgar Allan Poe <a href="https://articles.adsabs.harvard.edu/pdf/1994QJRAS..35..177C">thought he had found an answer</a>. On February 3 1848, he gave a public lecture about his ideas to 60 people at the New York Society Library.</p>
<p>Veering between metaphysics and science, Poe argued the cosmos had emerged from a single state of matter (“Oneness”) that fragmented and dispersed under the action of a repulsive force.</p>
<p>This meant the Universe was a finite sphere of matter. If the finite universe is populated by a sufficiently small number of stars, then we won’t see one in every direction we look. The night can be dark again. </p>
<p>Even if we assume the Universe is infinite, if it began at some point in the past then the <a href="https://academic.oup.com/book/32357">time taken by light to reach us</a> would limit the size of the amount of the Universe we can see. This travel time would create a horizon beyond which distant stars would remain inaccessible. </p>
<p>Poe’s audience at the New York Society Library did not give him the rapturous reception he had hoped for. Later the same year, he published his theories in the prose poem <a href="https://www.eapoe.org/works/editions/eurekac.htm">Eureka</a>, which was little circulated.</p>
<p>The following year, on October 7 1849, Poe died at the age of 40. It would be more than a century before scientists confirmed his intuitions about the enigma of the dark night sky.</p>
<h2>Two and a half facts</h2>
<p>In the first half of the 20th century many new theories of the cosmos were developed, spurred on by Einstein’s theory of general relativity, which explained gravity, space and time in new ways. In the second half of the century, these cosmological theories began to be tested with observations.</p>
<p>In 1963, <a href="https://articles.adsabs.harvard.edu/pdf/1993QJRAS..34..157L">British astronomer Peter Scheuer</a> argued that cosmology was based on only “two and a half facts”: </p>
<ul>
<li>fact 1: the night sky is dark, which had been known for some time</li>
<li>fact 2: galaxies are <a href="https://en.wikipedia.org/wiki/Hubble%27s_law">moving away from each other</a>, as shown by Hubble’s observations published in 1929</li>
<li>fact 2.5: the content of the Universe is probably evolving as cosmic time unfolds. </li>
</ul>
<p>Strong controversies on the interpretation of facts 2 and 2.5 agitated the scientific community in the 1950s and 1960s. Was the Universe essentially stationary, or had it begun in an enormous explosion – a Big Bang? Supporters of both sides conceded, however, they needed to explain the darkness of the night sky. </p>
<h2>The lifetime of stars</h2>
<p>British cosmologist Edward Harrison <a href="https://www.nature.com/articles/204271b0">resolved the conflict</a> in 1964. He showed that the main factor determining the brightness of the night sky is actually the finite age of the stars. </p>
<p>The number of stars in the observable Universe is <a href="https://www.esa.int/Science_Exploration/Space_Science/Herschel/How_many_stars_are_there_in_the_Universe">extremely large</a>, but it is finite. This limited number, each burning for a limited time, spread over a gigantic volume, lets darkness manifest itself between the stars. </p>
<p>Harrison later <a href="https://www.nature.com/articles/322417a0">realised</a> this solution had already been proposed not only by Edgar Allan Poe, but by British physicist Lord Kelvin in 1901. </p>
<p>Observations in the 1980s confirmed the resolution proposed by Poe, Kelvin and Harrison. Olbers’ paradox had <a href="https://ui.adsabs.harvard.edu/link_gateway/1986SSRv...44..169W/ADS_PDF">finally been put to rest</a>.</p>
<h2>Fossil light</h2>
<p>Or perhaps not quite. Viewed from a different angle, there is another resolution to the paradox: the night sky is not actually so dark after all. </p>
<p>After the discovery of the expansion of the Universe in the late 1920s, scientists realised the Universe could have started off extremely compact, dense and hot. This is the “hot Big Bang” model we have today.</p>
<p>One core prediction of this model is the existence of “fossil light” released in the cosmic dawn. This fossil light should be observable today – but not with the naked eye, as the expanding Universe would have shifted it to longer wavelengths. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=323&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=323&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=323&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=406&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=406&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528761/original/file-20230529-19-ipn9fu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=406&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">When seen via microwave radiation, the sky is dominated by our Milky Way galaxy. But behind it we can see the fainter glow of the cosmic microwave background.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/images/pia13239-plancks-view-of-the-whole-sky">ESA, HFI & LFI consortia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>This radiation – the cosmic microwave background – was <a href="https://ui.adsabs.harvard.edu/abs/1965ApJ...142..419P/abstract">detected in 1964</a>. Now measured with <a href="https://doi.org/10.1051/0004-6361/201833880">exquisite accuracy</a>, the cosmic background radiation is the most common light in the Universe. </p>
<p>We now know the cosmos is also illuminated by <a href="https://ui.adsabs.harvard.edu/abs/1967ApJ...148..377P">a second, much fainter background light</a>, produced by galaxies as they form and evolve. This light is referred to as the cosmic ultraviolet, optical and infrared background. </p>
<p>So we can also answer Olbers’ paradox by saying the sky is not dark, but faintly glimmers with the <a href="https://journals.sagepub.com/doi/10.1177/0003702818767133">dim relic radiation</a> of all that has been over the finite lifetime of the Universe.</p>
<h2>New answers, new questions</h2>
<p>In 2023, Olbers’ paradox has evolved into a rich field of research. In our own work, we carry out ever-more precise measurements of the brightness of the night sky, and simulate the stars of the cosmos with supercomputers. We can now determine the <a href="https://academic.oup.com/mnras/article/503/2/2033/6152275">number of stars</a> in the sky with great accuracy. </p>
<p>Nevertheless, puzzles remain. Last year the New Horizons space probe, out beyond the orbit of Pluto and away from the dust of the inner Solar System, found the sky is <a href="https://iopscience.iop.org/article/10.3847/2041-8213/ac573d/pdf">twice as bright</a> as we expected it to be.</p>
<p>And so the question of the darkness of the sky lives on, crossing ages and cultures.</p><img src="https://counter.theconversation.com/content/206575/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Biteau receives funding from University Paris-Saclay, CNRS (Centre National de la Recherche) and ANR (Agence National de la Recherche). </span></em></p><p class="fine-print"><em><span>Alberto Domínguez receives funding from Ministerio de Ciencia e Innovación (Spain) and Banco Santander - Universidad Complutense de Madrid.</span></em></p><p class="fine-print"><em><span>David Valls-Gabaud receives funding from the CNRS (Centre National de la Recherche Scientifique) and CNES (Centre National d'Etudes Spatiales).</span></em></p><p class="fine-print"><em><span>José Fonseca receives funding from Fundação para a Ciência e Tecnologia. </span></em></p><p class="fine-print"><em><span>Juan Garcia-Bellido receives funding from MICINN (Spain) through various research projects.</span></em></p><p class="fine-print"><em><span>Simon Driver receives funding from the Australian Research Council which supports studies of the Extragalactic Background Light (EBL). Simon is also a member of the Hubble Space Telescope SkySURF program (measuring the EBL) and a member of the Messier team (a potential space mission which includes, as part of its science case, studies of the EBL).</span></em></p><p class="fine-print"><em><span>Hervé Dole 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 darkness of the night sky seems so obvious as to need no explanation – yet it has intrigued and baffled scientists for centuries.Jonathan Biteau, Maître de conférence en physique des astroparticules, Université Paris-SaclayAlberto Domínguez, Investigador en Astrofísica, Universidad Complutense de MadridDavid Valls-Gabaud, Astrophysicien, Directeur de recherches au CNRS, Observatoire de ParisHervé Dole, Astrophysicien, Professeur, Vice-président, art, culture, science et société, Université Paris-SaclayJosé Fonseca, Assistant Research, Universidade do PortoJuan Garcia-Bellido, Catedratico de Fisica Teórica, Universidad Autónoma de MadridSimon Driver, ARC Laureate Fellow and Winthrop Research Professor at the International Centre for Radio Astronomy Research, UWA., The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2008292023-03-05T19:19:56Z2023-03-05T19:19:56ZWhat are the best conditions for life? Exploring the multiverse can help us find out<figure><img src="https://images.theconversation.com/files/513318/original/file-20230303-18-ugje3l.jpeg?ixlib=rb-1.1.0&rect=12%2C0%2C4013%2C3024&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Israel Pina / Unsplash</span></span></figcaption></figure><p>Is our universe all there is, or could there be more? Is our universe just one of a countless multitude, all together in an all-encompassing multiverse? </p>
<p>And if there are other universes, what would they be like? Could they be habitable?</p>
<p>This might feel like speculation heaped upon speculation, but it’s not as crazy as you might think. </p>
<p>My colleagues and I have been exploring what other parts of the multiverse might be like – and what these hypothetical neighbouring universes can tell us about the conditions that make life possible, and how they arise.</p>
<h2>What-if universes</h2>
<p>Some physicists <a href="https://www.space.com/25100-multiverse-cosmic-inflation-gravitational-waves.html">contend</a> that a burst of rapid expansion at the cosmic dawn known as inflation makes some form of multiverse inevitable. Our universe would really just be one of many. </p>
<p>In this theory, each new universe crystallises out of the seething background of inflation, imprinted with its own unique mix of physical laws.</p>
<p>If physical laws similar to ours govern these other universes, then we can come to grips with them. Well, at least in theory. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&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 history of our universe. Other universes with slightly different laws of physics may also have crystallised from the early period of inflation.</span>
<span class="attribution"><a class="source" href="http://map.gsfc.nasa.gov/media/060915/index.html">NASA</a></span>
</figcaption>
</figure>
<p>Within our universe, physics is governed by rules that tell us how things should interact with each other, and constants of nature, such as the speed of light, that dictate the strengths of these interactions. So, we can imagine hypothetical “what-if” universes where we change these properties and explore the consequences within mathematical equations.</p>
<p>This might sound simple, but the rules we tinker with are the fundamental makeup of the universe. If we imagine a universe where, say, the electron is a hundred times heavier than in our universe, then what would its consequences be for stars, planets and even life?</p>
<h2>What does life need?</h2>
<p>We recently tackled this question in a series of papers where we considered habitability across the multiverse. Of course, habitability is a complex concept, but we think life requires a few choice ingredients to get going.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-multiverse-is-huge-in-pop-culture-right-now-but-what-is-it-and-does-it-really-exist-181781">The multiverse is huge in pop culture right now – but what is it, and does it really exist?</a>
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<p>Complexity is one of those ingredients. For life on Earth, that complexity comes from the elements of the periodic table, which can be mixed and arranged into a myriad of different molecules. We are living molecular machines. </p>
<p>But a stable environment and a steady flow of energy are also essential. It is no surprise that Earthly life began on the surface of a rocky planet, with an abundance of chemical elements, bathed in the light of a long-lived stable star.</p>
<h2>Tweaking the fundamental forces</h2>
<p>Do similar environments exist across the extent of the multiverse? We started our theoretical exploration by considering the <a href="https://www.mdpi.com/2218-1997/8/12/651">abundance of chemical elements</a>. </p>
<p>In our universe, other than primordial hydrogen and helium that were formed in the Big Bang, all elements arise through the lives of stars. They are either generated through the nuclear reactions in stellar cores, or in the supreme violence of supernovae, when a massive star tears itself apart at the end of its life.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-are-lucky-to-live-in-a-universe-made-for-us-46988">We are lucky to live in a universe made for us</a>
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<p>All these processes are governed by the four fundamental forces in the universe. Gravity squeezes the stellar core, driving it to immense temperatures and densities. Electromagnetism tries to force atomic nuclei apart, but if they can get close enough, the strong nuclear force can bind them into a new element. Even the weak nuclear force, which can flip a proton into a neutron, plays an important role in the ignition of the stellar furnace.</p>
<p>The masses of the fundamental particles, such as electrons and quarks, can also play a pivotal role. </p>
<p>So, to explore these hypothetical universes, we have many dials we can adjust. The changes to the fundamental universe flow through to the rest of physics.</p>
<h2>The carbon–oxygen balance</h2>
<p>To tackle the immense complexity of this problem, we chopped the various pieces of physics into manageable chunks: <a href="https://www.mdpi.com/2218-1997/9/1/4">stars and atmospheres</a>, <a href="https://www.mdpi.com/2218-1997/9/1/2">planets and plate tectonics</a>, the <a href="https://www.mdpi.com/2218-1997/9/1/42">origins of life</a>, and more. And then we pinned the chunks together to tell an overall story about habitability across the multiverse.</p>
<p>A complex picture emerges. Some factors can strongly influence the habitability of a universe. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-a-planet-need-plate-tectonics-to-develop-life-61303">Does a planet need plate tectonics to develop life?</a>
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<p>For example, the ratio of carbon to oxygen, something set by a particular chain of nuclear reactions in the heart of a star, appears to be particularly important. </p>
<p>Straying too far from the value in our universe, where there are roughly equal amounts of the two elements, results in environments where it would be extremely difficult for life to emerge and thrive. </p>
<p>But the abundance of other elements appears to be less important. As long as they are stable, which does depend on the balance of the fundamental forces, they can play a pivotal role in the building blocks of life.</p>
<h2>More complexity to explore</h2>
<p>We have only been able to take a broad-brush approach to unravel habitability across the multiverse, sampling the space of possibilities in very discrete steps. </p>
<p>Furthermore, to make the problem manageable, we had to take several theoretical shortcuts and approximations. So we are only at the first stage of understanding the conditions for life across the multiverse.</p>
<p>In the next steps, the full complexity of alternative physics of other universes needs to be considered. We will need to understand the influence of the fundamental forces at the small scale and extrapolate it to the large scale, onto the formation of stars and eventually planets. </p>
<h2>A word of caution</h2>
<p>The notion of a multiverse is still only a hypothesis, an idea that has yet to be tested. In truth, we don’t yet know if it is an idea that <em>can</em> be tested. </p>
<p>And we don’t know if the physical laws could be different across the multiverse and, if they are, just how different they could be. </p>
<p>We may be at the start of a journey that will reveal our ultimate place within infinity – or we may be heading for a scientific dead end.</p><img src="https://counter.theconversation.com/content/200829/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Geraint Lewis receives funding from Australian Research Council. </span></em></p>Some physicists think we live in a multiverse, surrounded by universes not quite like our own. What does that mean for life?Geraint Lewis, Professor of Astrophysics, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2003432023-02-22T19:04:55Z2023-02-22T19:04:55Z‘We just discovered the impossible’: how giant baby galaxies are shaking up our understanding of the early Universe<figure><img src="https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&rect=21%2C24%2C1978%2C1319&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Images of six candidate massive galaxies, seen 500–800 million years after the Big Bang.</span> <span class="attribution"><span class="source">NASA / ESA / CSA / I. Labbe</span>, <span class="license">Author provided</span></span></figcaption></figure><p>“Look at this,” says Erica’s message. She is poring over the very first images from the brand new James Webb Space Telescope (JWST). </p>
<p>It is July 2022, barely a week after those first images from the revolutionary super telescope were released. Twenty-five years in the making, a hundred to a thousand times more powerful than any previous telescope, one of the biggest and most ambitious scientific experiments in human history: it is hard to not speak in superlatives, and it is all true. </p>
<p>The telescope took decades to build, because it had to be made foldable to fit on top of a rocket and be sent into the coldness of space, 1.5 million kms from Earth. Here, far from the heat glow of the Earth, JWST can detect the faintest infrared light from the distant universe. </p>
<p>Little did I know that among the pictures is a small red dot that will shake up our understanding of how the first galaxies formed after the Big Bang. After months of analysis, my colleagues and I just <a href="https://www.nature.com/articles/s41586-023-05786-2">published our results in Nature</a>.</p>
<h2>Hunting new kinds of galaxies</h2>
<p>Erica and I are on the hunt to discover new types of galaxies. Galaxies that the venerable Hubble Space Telescope had missed, even after decades of surveying the sky. </p>
<p>She and I go back 15 years. We met when she was a first-year student at a Californian liberal arts college and I was a freshly minted PhD straight out of university, just starting my first gig as a researcher in Los Angeles. JWST was only a distant rumor.</p>
<p>Somehow, many years later, our paths crossed again, and now Assistant Professor Erica Nelson of the University of Colorado and I are finding ourselves at the tip of the spear attacking the first data of a very real JWST. </p>
<hr>
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<strong>
Read more:
<a href="https://theconversation.com/two-experts-break-down-the-james-webb-space-telescopes-first-images-and-explain-what-weve-already-learnt-186738">Two experts break down the James Webb Space Telescope's first images, and explain what we've already learnt</a>
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<p>“UFOs”, she calls the new galaxies, and I can read a giant grin between the lines: <a href="https://arxiv.org/abs/2208.01630">“Ultra-red Flattened Objects”</a>, because they all look like flying saucers. In the colour images they appear very red because all the light is coming out in the infrared, while the galaxies are invisible at wavelengths humans can see. </p>
<p>Infrared is JWST’s superpower, allowing it to spy the most distant galaxies. Ultraviolet and visible light from the first stars and galaxies that formed after the Big Bang is stretched out by the expansion of the universe as it travels towards us, so by the time the light reaches us we see it as infrared light. </p>
<h2>Impossibly early, impossibly massive galaxies</h2>
<p>All of Erica’s galaxies look like saucers, except one. I stare at the little red dot on the screen. That is no UFO. And then it hits me: this is something very different. Much more important. </p>
<p>I run the analysis software on the little pinprick and it spits out two numbers: distance 13.1 billion light years, mass 100 billion stars, and I nearly spit out my coffee. We just discovered the impossible. Impossibly early, impossibly massive galaxies. </p>
<p>At this distance, the light took 13 billion years to reach us, so we are seeing the galaxies at a time when the universe was only 700 million years old, barely 5% of its current age of 13.8 billion years. If this is true, this galaxy has formed as many stars as our present-day Milky Way. In record time. </p>
<p>And where there is one, there are more. One day later I had found six. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&rect=21%2C24%2C1978%2C1319&q=45&auto=format&w=1000&fit=clip"><img alt="Pixelated images of six reddish dots against dark backgrounds." src="https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&rect=21%2C24%2C1978%2C1319&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/511593/original/file-20230222-22-uxqf8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Images of six candidate massive galaxies, seen 500–800 million years after the Big Bang.</span>
<span class="attribution"><span class="source">NASA / ESA / CSA / I. Labbe</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Astronomy’s missing link?</h2>
<p>Could we have discovered astronomy’s missing link? There has been a long-standing puzzle in galaxy formation. As we look out in space and back in time, we see the “corpses” of fully formed, mature galaxies appear seemingly out of nowhere around 1.5 billion years after the Big Bang. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-the-james-webb-space-telescope-finding-the-furthest-oldest-youngest-or-first-galaxies-an-astronomer-explains-187915">Is the James Webb Space Telescope finding the furthest, oldest, youngest or first galaxies? An astronomer explains</a>
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</em>
</p>
<hr>
<p>These galaxies have stopped forming stars. Dead galaxies, we call them, and some astronomers are obsessed with them. The stellar ages of these dead galaxies suggest they must have formed much earlier in the Universe, but Hubble has never been able to spot their earlier, living stages. </p>
<p>Early dead galaxies are truly bizarre creatures, packing as many stars as the Milky Way, but in a size 30 times smaller. Imagine an adult, weighing 100 kilos, but standing 6cm tall. Our little red dots are equally bizarre. They look like baby versions of the same galaxies, also weighing in at 100 kilos, with a height of 6cm. </p>
<h2>Too many stars, too early</h2>
<p>There is a problem, however. These little red dots have too many stars, too early. Stars form out of hydrogen gas, and fundamental cosmological (“Big Bang”) theory makes hard predictions on how much gas is available to form stars. </p>
<p>To produce these galaxies so quickly, you almost need all the gas in the universe to turn into stars at near 100% efficiency. And that is very hard, which is the scientific term for impossible. This discovery could transform our understanding of how the earliest galaxies in the universe formed. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=536&fit=crop&dpr=1 754w, https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=536&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/511591/original/file-20230222-16-4ylne.png?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"></a>
<figcaption>
<span class="caption">The six galaxies and their surroundings in the sky.</span>
<span class="attribution"><span class="source">NASA / ESA / CSA / I. Labbe</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The implication is that there is different channel, a fast track, that produces monster galaxies very quickly, very efficiently. A fast track for the top 1%.</p>
<p>In a way, each of these candidates can be considered a “black swan”. The confirmation of even one would rule out our current “all swans are white” model of galaxy formation, in which all early galaxies grow slowly and gradually. </p>
<h2>Checking the fingerprints</h2>
<p>The first step to solve this mystery is to confirm the distances with spectroscopy, where we put the light of each of these galaxies through a prism, and split it into its rainbow-like fingerprint. This will tell us the distance to 0.1% accuracy. </p>
<p>It will also tell us what is producing the light, whether it is stars or something else more exotic. </p>
<p>By chance, about a month ago, JWST already targeted one of the six candidate massive galaxies and it turned out to be a distant baby quasar. A quasar is a phenomenon that occurs when gas falls into a supermassive black hole at the centre of a galaxy and starts to shine brightly. </p>
<p>This is really exciting on the one hand, because the origin of supermassive black holes in galaxies is not understood either, and finding baby quasars might just hold the key. On the other hand, quasars can outshine their entire host galaxy, so it is impossible to tell how many stars are there and whether the galaxy is really that massive. </p>
<p>Could that be the answer for all of them? Baby quasars everywhere? Probably not, but it will take another year to investigate the remaining galaxies and find out. </p>
<p>One black swan down, five to go.</p><img src="https://counter.theconversation.com/content/200343/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ivo Labbe receives funding from ARC in the form of a Future Fellowship, to conduct research with the James Webb Space Telescope.</span></em></p>The discovery of massive, early galaxies could force scientists to rethink how the first galaxies formed after the Big Bang.Ivo Labbe, ARC Future Fellow / Associate Professor, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1998312023-02-15T17:16:17Z2023-02-15T17:16:17ZBlack holes may be the source of mysterious dark energy that makes up most of the universe<figure><img src="https://images.theconversation.com/files/509870/original/file-20230213-4443-xsmxpu.jpg?ixlib=rb-1.1.0&rect=313%2C0%2C2251%2C1483&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">black hole</span> </figcaption></figure><p><a href="https://www.nasa.gov/vision/universe/starsgalaxies/black_hole_description.html">Black holes</a> could explain a mysterious form of energy that makes up most of the universe, according to astronomers. The existence of <a href="https://en.wikipedia.org/wiki/Dark_energy">“dark energy”</a> has been inferred from observations of stars and galaxies, but no one has been able to explain what it is, or where it comes from.</p>
<p>The stuff, or matter, that makes up the familiar world around us is just 5% of everything in the universe. Another 27% is <a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy">dark matter</a>, a shadowy counterpart of ordinary matter which does not emit, reflect or absorb light. However, the majority of the cosmos – around 68% – is dark energy.</p>
<p>The new evidence that black holes could be the source of dark energy is described in <a href="https://iopscience.iop.org/article/10.3847/2041-8213/acb704">a scientific paper</a> published in The Astrophysical Journal Letters. The study is the work of 17 astronomers in nine countries and was led by the University of Hawaii. The collaboration included researchers in the UK, based at STFC RAL Space, The Open University, and Imperial College London.</p>
<p>Searching through data spanning nine billion years of cosmic history, the astronomers have uncovered the first evidence of <a href="https://physicsworld.com/a/cosmological-coupling-is-making-black-holes-bigger-study-suggests/">“cosmological coupling”</a>, which would mean that the growth of black holes over time is linked to the expansion of the universe itself.</p>
<p>The idea that black holes might contain something called <a href="https://en.wikipedia.org/wiki/Vacuum_energy">vacuum energy</a> (a manifestation of dark energy) is not particularly new and in fact was discussed theoretically as far back as the 1960s. But this latest work assumes this energy (and therefore the mass of the black holes) would increase with time as the universe expands as a result of cosmological coupling.</p>
<p>The team calculated how much of the dark energy in the universe could be attributed to this process. They found that black holes could potentially explain the total amount of dark energy we measure in the universe today. The result could solve one of the most fundamental problems in modern cosmology.</p>
<h2>Rapid expansion</h2>
<p><a href="https://hubblesite.org/contents/articles/the-big-bang">Our universe began in a Big Bang</a> around 13.7 billion years ago. The energy from this explosion of space and time caused the universe to expand rapidly, with all the galaxies flying away from each other. However, we expect that this expansion would gradually slow down because of the effect of gravity on all the stuff in the cosmos.</p>
<p>This is the version of the universe we thought we lived in until the late 1990s, when the Hubble space telescope discovered something strange. Observations of distant exploding stars showed that, in the past, the universe <a href="https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_universe">was actually expanding more slowly than it is today</a>. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/gjwxnoPoEHQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The new discovery is explained by Chris Pearson of RAL Space and The Open University.</span></figcaption>
</figure>
<p>So the expansion of the universe has not been slowing due to gravity, as everyone thought, but instead has been accelerating. This was highly unexpected and astronomers struggled to explain it.</p>
<p>To account for this, it was proposed that a “dark energy” was responsible for pushing things apart more strongly than gravity pulled things together. The concept of dark energy was very similar to a mathematical construct Einstein had proposed but later discarded – a <a href="https://en.wikipedia.org/wiki/Cosmological_constant">“cosmological constant”</a> that opposed gravity and kept the universe from collapsing.</p>
<h2>Stellar explosions</h2>
<p>But what is dark energy? The solution, it seems, might lie with another cosmic mystery: black holes. Black holes are commonly born when <a href="https://public.nrao.edu/ask/when-does-a-neutron-star-or-black-hole-form-after-a-supernova/">massive stars explode and die at the ends of their lives</a>. The gravity and pressure in these violent explosions compresses vast amounts of material into a small space. For instance, a star about the same mass as our sun would be squashed into a space of just a few tens of kilometres. </p>
<p>A black hole’s gravitational pull is so strong that not even light can escape it – everything gets sucked in. At the centre of the black hole is a place called a <a href="https://bigthink.com/starts-with-a-bang/singularity-black-hole/">singularity</a>, where matter is crushed into a point of infinite density. The problem is that singularities are a mathematical construct that should not exist.</p>
<figure class="align-center ">
<img alt="The Andromeda galaxy" src="https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/509866/original/file-20230213-14-3kjqam.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">
<figcaption>
<span class="caption">Dark energy explains why the expansion of the universe is speeding up.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/galex/pia15416.html">NASA/JPL-Caltech</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The black holes nestled at the centres of galaxies are much heftier than those born when stars die violently. These galactic “supermassive” black holes can weigh millions to billions of times the mass of our Sun.</p>
<p>All black holes increase in size by accumulating matter, by swallowing stars that get too close, or by merging with other black holes. So we expect them to get bigger as the universe gets older.</p>
<p>In the latest paper, the team looked at supermassive black holes in the centres of galaxies and found that these black holes gain mass over billions of years. </p>
<h2>Radical rethink</h2>
<p>The team compared observations of <a href="https://en.wikipedia.org/wiki/Elliptical_galaxy">elliptical galaxies</a>, which lack star formation, in the past and in the present day. These dead galaxies have used up all their fuel so any increase in their black hole mass over this time cannot be ascribed to the normal processes by which black holes grow by accumulating matter.</p>
<p>Instead, the team proposed that these black holes actually contain vacuum energy and that they are “coupled” to the expansion of the universe, so that they increase in mass as the universe expands. </p>
<figure class="align-center ">
<img alt="Visualisation of a black hole" src="https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&rect=17%2C34%2C3782%2C2098&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/509864/original/file-20230213-18-s6s06q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A visualisation of a black hole, which could play a role in dark energy.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2019/nasa-visualization-shows-a-black-hole-s-warped-world">NASA’s Goddard Space Flight Center/Jeremy Schnittman</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This model neatly provides a possible origin for the dark energy in the universe. It also circumvents the mathematical problems that affect some studies of black holes, because it avoids the need for a singularity at the centre.</p>
<p>The team also calculated how much of the dark energy in the universe could be attributed to this process of coupling. They concluded that it would be possible for black holes to provide the necessary amount of vacuum energy to account for all the dark energy that we measure in the universe today. </p>
<p>This would not only explain the origin of dark energy in the universe but would also make us radically rethink our understanding of black holes and their role in the cosmos.</p>
<p>Much more work needs to be done to test and confirm this idea, both from observations of the sky and from theory. But we may at last be seeing a new way to solve the problem of dark energy.</p><img src="https://counter.theconversation.com/content/199831/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Pearson receives funding from STFC and is head of astronomy at STFC RAL Space and a visiting fellow at the Open University </span></em></p><p class="fine-print"><em><span>Dave Clements receives funding from STFC and the UKSA and works at Imperial College London.</span></em></p>Astronomers have found that mysterious dark energy may originate in black holes.Chris Pearson, Astronomy Group Lead, Space Operations Division at RAL Space, and Visiting Fellow, The Open UniversityDave Clements, Reader in Astrophysics, Imperial College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1966492022-12-15T16:23:01Z2022-12-15T16:23:01ZHow the James Webb Space Telescope has revealed a surprisingly bright, complex and element-filled early universe – podcast<figure><img src="https://images.theconversation.com/files/501209/original/file-20221215-15338-7jlg2y.png?ixlib=rb-1.1.0&rect=5%2C191%2C1886%2C1613&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The James Webb Space Telescope is providing astronomers with images and data that reveal secrets from the earliest era of the universe.</span> <span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2022/034/01G7DA5ADA2WDSK1JJPQ0PTG4A?news=true">NASA/STScI</a></span></figcaption></figure><p>If you want to know what happened in the earliest years of the universe, you are going to need a very big, very specialized telescope. Much to the joy of astronomers and space fans everywhere, the world has one – the <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-on-the-team-explains-how-to-send-a-giant-telescope-to-space-and-why-167516">James Webb Space Telescope</a>. </p>
<p>In this episode of “<a href="https://theconversation.com/uk/topics/the-conversation-weekly-98901">The Conversation Weekly</a>,” we talk to three experts about what astronomers have learned about the first galaxies in the universe and how just six months of data from James Webb is already changing astronomy. </p>
<iframe src="https://embed.acast.com/60087127b9687759d637bade/639ae709691e1f00111140ea" frameborder="0" width="100%" height="190px"></iframe>
<p><iframe id="tc-infographic-561" class="tc-infographic" height="100" src="https://cdn.theconversation.com/infographics/561/4fbbd099d631750693d02bac632430b71b37cd5f/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The James Webb Space Telescope successfully launched into space on Dec. 25, 2021. After about six months of travel, setup and calibration, the telescope began collecting data and NASA published the first <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-explains-the-stunning-newly-released-first-images-186800">stunning images</a>.</p>
<p>One of Webb’s nicknames is the “<a href="https://theconversation.com/is-the-james-webb-space-telescope-finding-the-furthest-oldest-youngest-or-first-galaxies-an-astronomer-explains-187915">first light telescope</a>.” This is because Webb was specifically designed to be able to see as far back as possible into the earliest days of the universe and detect some of the first visible light. </p>
<p>You can see these galaxies in the <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-explains-the-stunning-newly-released-first-images-186800">images NASA has released</a>. <a href="https://scholar.google.com/citations?user=AWluLnoAAAAJ&hl=en&oi=ao">Jonathan Trump</a>, an astronomer at the University of Connecticut, is on one of the teams working on some of the early James Webb data. He was watching the release of the first images live and noticed some things many nonastronomers might have missed. “In the background, behind these beautiful arcs and spirals and massive elliptical galaxies are these tiny, itty-bitty red smudges. That’s what I was most interested in, because those are some of the first galaxies in the universe.”</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two images showing a suite of galaxies with small boxes around faint red smudges." src="https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=247&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=247&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=247&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=310&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=310&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501213/original/file-20221215-22-oaoozi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=310&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This compound image shows some of the earliest galaxies ever seen, highlighted by the small boxes in the images on the left and right, and shown up close in the images in the center.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2022/nasa-s-webb-draws-back-curtain-on-universe-s-early-galaxies">NASA, ESA, CSA, Tommaso Treu (UCLA)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>To see any of these galaxies from the earliest days of the universe would be exciting, but right off the bat, <a href="https://scholar.google.com/citations?user=oXVDWEcAAAAJ&hl=en&oi=ao">Jeyhan Kartaltepe</a>, an astronomer at the Rochester Institute of Technology, found something exciting when she started digging into the data. </p>
<p>“One of the things we’ve learned is that there are more of these galaxies than we expected to see.” In addition to working on identifying these early galaxies, Kartaltepe has been using Webb’s incredible resolution to study their structure and shape. “We expect there to be discs because discs form pretty naturally in the universe whenever you have something that’s rotating. But we’ve been seeing a lot of them, which has been a bit of a surprise.”</p>
<p>In addition to noting the shape of the galaxies in the early universe, astronomers like Trump are starting to be able to assess the <a href="https://arxiv.org/pdf/2207.12388.pdf">chemical composition of these galaxies</a>. He does this by looking at the spectrum of light James Webb is collecting. “We look at these distant galaxies and we look for particular patterns of emission lines. We often call them a chemical fingerprint because it really is like a particular fingerprint of particular elements in the gas in a galaxy.” </p>
<p>The universe started with just hydrogen and helium, but as stars formed and fused elements together, bigger, heavier elements started to emerge and fill in the periodic table as it is today. And just like Kartaltepe, Trump is finding evidence that things were happening faster in the early universe than astronomers expected. “I would’ve guessed that the universe would have struggled to make the periodic table and build up things. But that’s not what we found. Instead, the universe seems to have proceeded pretty rapidly.”</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photos showing thousands of galaxies in a night sky." src="https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=612&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=612&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=612&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=769&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=769&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501210/original/file-20221215-20-lvlbo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=769&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This photo shows Webb’s first deep-field image, a long exposure of a small part of the sky revealing thousands of galaxies, many of which are too faint for even Hubble to detect.</span>
<span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2022/035/01G7DCWB7137MYJ05CSH1Q5Z1Z?news=true">NASA/STScI</a></span>
</figcaption>
</figure>
<p>The discoveries coming out of James Webb are already changing how astronomers think of the early universe and challenging much of the existing theory. But the truly exciting part is that we are just beginning to see what this telescope is capable of, as <a href="https://scholar.google.com/citations?user=npUHvbwAAAAJ&hl=en&oi=ao">Michael Brown</a>, an astronomer at Monash University, explains. </p>
<p>“I’ve been on science papers that have used literally just a couple of minutes of data,” Brown says. “The image quality is just so good that a couple of minutes can do amazing things.” But soon Webb will begin to do follow-up surveys, take deep-field images and stare at parts of the sky for days and even weeks. Over the coming months, years and decades, Webb is going to keep giving astronomers plenty to work on, and astronomers like Brown are excited. “There is just all this complexity there, and we are barely scratching the surface. This will be the stuff that people who are students now are going to devote their careers to. And it’s going to be marvelous.”</p>
<hr>
<p>This episode was produced by Katie Flood and Daniel Merino, with sound design by Eloise Stevens. It was written by Katie Flood and Daniel Merino. Mend Mariwany is the show’s executive producer. Our theme music is by Neeta Sarl. </p>
<p>You can find us on Twitter <a href="https://twitter.com/TC_Audio">@TC_Audio</a>, on Instagram at <a href="https://www.instagram.com/theconversationdotcom/">theconversationdotcom</a> or <a href="mailto:podcast@theconversation.com">via email</a>. You can also sign up to The Conversation’s <a href="https://theconversation.com/newsletter">free daily email here</a>. A transcript of this episode will be available soon. </p>
<p>Listen to “The Conversation Weekly” via any of the apps listed above, download it directly via our <a href="https://feeds.acast.com/public/shows/60087127b9687759d637bade">RSS feed</a>, or find out <a href="https://theconversation.com/how-to-listen-to-the-conversations-podcasts-154131">how else to listen here</a>.</p><img src="https://counter.theconversation.com/content/196649/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span> </span></em></p><p class="fine-print"><em><span>Jeyhan Kartaltepe receives funding from NASA and the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Jonathan Trump receives funding from NASA and NSF. </span></em></p><p class="fine-print"><em><span>Michael J. I. Brown receives research funding from the Australian Research Council and Monash University.</span></em></p>It has been one year since the launch of the James Webb Space Telescope and six months since the first pictures were released. Astronomers are already learning unexpected things about the early universe.Daniel Merino, Associate Science Editor & Co-Host of The Conversation Weekly Podcast, The ConversationNehal El-Hadi, Science + Technology Editor & Co-Host of The Conversation Weekly Podcast, The ConversationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1878282022-08-22T12:26:28Z2022-08-22T12:26:28ZWhat are wormholes? An astrophysicist explains these shortcuts through space-time<figure><img src="https://images.theconversation.com/files/476951/original/file-20220801-77550-omilb4.jpg?ixlib=rb-1.1.0&rect=29%2C426%2C4962%2C3263&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Solutions to Einstein's famous equations back in the 20th century describe 'wormholes,' or tunnels through space-time. </span> <span class="attribution"><a class="source" href="https://media.gettyimages.com/illustrations/wormhole-conceptual-artwork-illustration-id99312262?s=2048x2048">Mark Garlick/Science Photo Library via GettyImages</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">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<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>What are wormholes and do they exist? – Chinglembi D., age 12, Silchar, Assam, India</strong></p>
</blockquote>
<hr>
<p>Imagine two towns on two opposite sides of a mountain. People from these towns would probably have to travel all the way around the mountain to visit one another. But, if they wanted to get there faster, they could dig a tunnel straight through the mountain to create a shortcut. That’s the idea behind a wormhole.</p>
<p>A wormhole is like <a href="https://www.sciencefocus.com/space/what-is-a-wormhole/">a tunnel between two distant points</a> in our universe that cuts the travel time from one point to the other. Instead of traveling for many millions of years from one galaxy to another, under the right conditions one could theoretically use a wormhole to <a href="https://doi.org/10.1119/1.15620">cut the travel time</a> down to hours or minutes.</p>
<p>Because wormholes represent shortcuts <a href="https://doi.org/10.1103/PhysRevLett.61.1446">through space-time</a>, they could even act like time machines. You might emerge from one end of a wormhole at a time earlier than when you entered its other end.</p>
<p>While scientists have no evidence that wormholes actually exist in our world, they’re good tools to help astrophysicists <a href="https://scholar.google.com/citations?user=qqUNcY0AAAAJ&hl=en&oi=ao">like me</a> think about space and time. They may also answer age-old questions about what the universe looks like.</p>
<h2>Fact or fiction?</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of a wormhole, a tube with two funnel-like ends, next to a planet" src="https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=833&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=833&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=833&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1047&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1047&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476946/original/file-20220801-62374-uyna4z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1047&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scientists call the points where you would enter and exit a wormhole ‘mouths,’ while they call the tunnel itself the ‘throat.’</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/wormhole-in-space-royalty-free-illustration/670895147">Victor Habbick Visions/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<p>Because of these interesting features, many science fiction writers use wormholes in novels and movies. However, scientists have been just as captivated by the idea of wormholes as writers have.</p>
<p>While researchers have never found a wormhole in our universe, scientists often see wormholes described in the solutions to important physics equations. Most prominently, the solutions to the equations behind Einstein’s <a href="https://doi.org/10.1103/PhysRev.48.73">theory of space-time and general relativity</a> include wormholes. This theory describes the shape of the universe and how stars, planets and other objects move throughout it. Because Einstein’s theory has been tested many, many times and found to be <a href="https://doi.org/10.48550/arXiv.1705.04397">correct every time</a>, some scientists do expect wormholes to exist somewhere out in the universe. </p>
<p>But, other scientists think wormholes can’t possibly exist because they would be too unstable. </p>
<p>The constant pull of gravity affects every object in the universe, including Earth. So gravity would have an effect on wormholes, too. The scientists who are skeptical about wormholes believe that after a short time the middle of the wormhole would <a href="https://doi.org/10.1119/1.15620">collapse under its own gravity</a>, unless it had some force pushing outward from inside the wormhole to counteract that force. The most likely way it would do that is using what’s called “negative energies,” which would <a href="https://doi.org/10.1119/1.15620">oppose gravity</a> and stabilize the wormhole. </p>
<p>But as far as scientists know, negative energies can be created only in amounts much <a href="https://doi.org/10.1142/9789814289931_0055">too small</a> to counteract a wormhole’s own gravity. It’s possible that the Big Bang created teeny, tiny wormholes with small amounts of negative energies way back at the beginning of the universe, and over time these wormholes have <a href="https://doi.org/10.1103/PhysRevLett.61.1446">stretched out</a> as the universe has expanded. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/M_p6Z_Qm1_s?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In this short video by Fusion, a Caltech professor sums up what wormholes are and the stability question that’s boggling scientists.</span></figcaption>
</figure>
<h2>Just like black holes?</h2>
<p>While wormholes are interesting objects to think about, they still aren’t accepted in mainstream science. But that doesn’t mean they’re not real – black holes, which we astrophysicists know abound in our universe, weren’t accepted when scientists first suggested they existed, back in the 1910s. </p>
<p>Einstein first formulated his famous field equations in 1915, and German scientist Karl Schwarzschild found a way to mathematically describe black holes after <a href="https://doi.org/10.48550/arXiv.physics/9905030">only one year</a>. However, this description was so peculiar that the leading scientists of that era refused to believe that black holes could actually exist in nature. It took people 50 years to start taking black holes seriously – the term “black hole” wasn’t even coined <a href="https://www.physicsoftheuniverse.com/scientists_wheeler.html">until 1967</a>.</p>
<p>The same could happen with wormholes. It may take scientists a little while to come up with a consensus about whether or not they can exist. But if they do find strong evidence pointing to the existence of wormholes – which they may be able to do by looking at odd movements in <a href="https://doi.org/10.1103/PhysRevD.100.083513">star orbits</a> – the discovery will shape how scientists see and understand the universe.</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/187828/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dejan Stojkovic works for the State University of New York, University at Buffalo. He receives funding from the National Science Foundation. </span></em></p>An astrophysicist explains what wormholes are and how these theoretical space-time tunnels have popped up in the solutions to a set of decadesold equations.Dejan Stojkovic, Professor of Physics, University at BuffaloLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1879152022-08-01T04:04:51Z2022-08-01T04:04:51ZIs the James Webb Space Telescope finding the furthest, oldest, youngest or first galaxies? An astronomer explains<figure><img src="https://images.theconversation.com/files/476660/original/file-20220729-20-z3fsbn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">James Webb has peered into the distant Universe</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet">NASA</a></span></figcaption></figure><p>We’ve now seen the <a href="https://www.nasa.gov/webbfirstimages">first data from the James Webb Space Telescope</a>. It has observed the atmospheres of distant planets, groups of nearby galaxies, galaxy light bent by unseen dark matter, and clouds of gas and dust in stellar nurseries. </p>
<p>We have also seen headlines claiming Webb has found “<a href="https://www.newscientist.com/article/2329601-jwst-has-found-the-oldest-galaxy-we-have-ever-seen-in-the-universe/">the oldest galaxies we have ever seen</a>”, but what does that mean? </p>
<p>I’m a professional astronomer who <a href="https://ui.adsabs.harvard.edu/abs/2008ApJ...682..937B/abstract">studies old galaxies</a>, and even I find this a little puzzling.</p>
<h2>Looking far, looking back</h2>
<p>One of the key <a href="https://webb.nasa.gov/content/science/">science goals of Webb</a> is to peer back in time and observe the early Universe. Webb can do this because, like all telescopes, it is a time machine. </p>
<p>Light travels at 300,000 kilometres per second, so when we look at the Moon we are seeing it as it was a second ago. As the planets of our Solar System are millions or billions of kilometres away, we see them as they were minutes or hours ago. </p>
<p>Going further still, when we look at distant galaxies with telescopes we are often looking at light that has taken millions or billions of years to reach us. This means we are seeing these galaxies as they were millions or billions of years ago.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/when-you-look-up-how-far-back-in-time-do-you-see-101176">When you look up, how far back in time do you see?</a>
</strong>
</em>
</p>
<hr>
<h2>What has James Webb seen?</h2>
<p>The James Webb Space Telescope is able to see more distant galaxies than other telescopes, including the Hubble Space Telescope. </p>
<p>Like Hubble it is above the glowing and turbulent atmosphere of the Earth. However, whereas Hubble has a 2.3 metre mirror for focusing light, Webb has a vast 6.5 metre mirror formed from 18 hexagonal segments. Finally, Webb is optimised to detect infrared light, which is what we observe from the most distant galaxies as the expansion of the Universe has stretched ultraviolet and infrared light into the infrared. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="James Webb has a vast segmented mirror." src="https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476657/original/file-20220729-19-43296g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">James Webb has a vast segmented mirror that allows it to look into the distant past.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Among the first data obtained by Webb were infrared images looking towards a cluster of galaxies called <a href="https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet">SMACS 0723</a>. </p>
<p>The light from SMACS 0723 has taken 4.6 billion years to reach us, so we are seeing it as it was 4.6 billion years ago. That’s slightly older than the Sun and the Earth, which only formed 4.56 billion years ago.</p>
<p>In recent weeks, galaxies far beyond SMACS 0723 have gained attention. Webb has detected a number of galaxies in the direction of SMACS 0723 and <a href="https://ceers.github.io/index.html">other regions</a> that could be so distant their light has taken 13.5 billion years to reach us. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1551864183230177280"}"></div></p>
<p>I say “could” because more data will be needed to absolutely confirm their distances, but some of these galaxies are <a href="https://twitter.com/astrosteven/status/1551732076734455808">very compelling</a> candidates (others <a href="https://twitter.com/stewilkins/status/1552334303383650304">less so</a>).</p>
<p>As the light has taken 13.5 billion years to reach us, we are seeing these galaxies as they were 13.5 billion years ago. The Universe itself is 13.8 billion years old, so we could be seeing galaxies as they were just a few hundred million years after the <a href="https://theconversation.com/au/topics/big-bang-470">Big Bang</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maise's galaxy" src="https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=292&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=292&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=292&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=367&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=367&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476667/original/file-20220729-25-960hmj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=367&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Maisie’s Galaxy may be one of the most distant celestial objects yet observed.</span>
<span class="attribution"><span class="source">Steve Finkelstein/Twitter</span></span>
</figcaption>
</figure>
<h2>Young, old or early?</h2>
<p>While these very distant galaxies have been advertised as the “<a href="https://www.dailymail.co.uk/sciencetech/article-11032541/James-Webb-discovers-oldest-galaxy-universe-13-5-billion-year-old-stars.html">oldest galaxies</a>”, I find this a little confusing. We are actually seeing these galaxies as they appeared when they were very young, perhaps a hundred million years old or so.</p>
<p>It is true that these galaxies will be old now, but our own Milky Way galaxy is very old now too. While our Sun is 4.56 billion years old, many stars in our galaxy are 10 billion years old and some stars in the Milky Way are <a href="https://www.anu.edu.au/news/all-news/oldest-stars-found-near-milky-way-centre">13 billion years old</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The Milky Way is billions of years old." src="https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476663/original/file-20220729-12-jfj12d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The galaxy we live in, the Milky Way, is billions of years old.</span>
<span class="attribution"><span class="source">Caroline Jones/Flickr</span></span>
</figcaption>
</figure>
<p>Furthermore, the very distant galaxies Webb has spotted will look very different today. Galaxies grow by acquiring gas and dark matter, forming new stars and merging with other galaxies. </p>
<p>A small galaxy that was vigorously forming stars soon after the Big Bang may have ended up being the seed of a galaxy that today is very massive and stopped forming stars long ago. That small galaxy and its old stars could also have ended up being just part of a larger galaxy formed relatively recently by merging galaxies together.</p>
<h2>A record set to fall</h2>
<p>So should we call these most distant galaxies young or old? Perhaps neither. </p>
<p>James Webb is seeing the <em>earliest</em> galaxies yet observed – some of the <em>first</em> galaxies that formed soon after the Big Bang.</p>
<p>I have thrown in one last caveat – “yet observed”. Webb has only just begun its <a href="https://webb.nasa.gov/content/about/faqs/facts.html">mission</a>, and current analyses are based on data collected over hours. </p>
<p>With days’ worth of data, Webb will push its view out to fainter and further objects, and see yet-more-distant galaxies. The record for the most distant and thus earliest observed galaxy will probably tumble a few times before the year is out.</p><img src="https://counter.theconversation.com/content/187915/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.
</span></em></p>James Webb has spotted extremely distant galaxies formed soon after the Big Bang, but are they old or young? Or is this the wrong question to ask?Michael J. I. Brown, Associate Professor in Astronomy, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1855372022-06-23T14:46:57Z2022-06-23T14:46:57ZCurious Kids: what is cosmic microwave background radiation?<figure><img src="https://images.theconversation.com/files/470549/original/file-20220623-51658-fb0ewc.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C3000%2C1985&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/abstract-space-nebula-backgrounds-1007304667">Yaroslav Vitkovskiy/Shutterstock</a></span></figcaption></figure><p><strong>What is cosmic microwave background radiation? Did it happen after the Big Bang? – Sreehari, aged nine, Kerala State, India</strong></p>
<p>The <a href="https://www.space.com/33892-cosmic-microwave-background.html">Cosmic Microwave Background</a> (CMB for short), is light: the oldest and most distant light that we can see in the entire universe. It comes from soon after the <a href="https://theconversation.com/curious-kids-what-existed-before-the-big-bang-did-something-have-to-be-there-to-go-boom-103742">Big Bang</a> – which is considered to be the beginning of the universe.</p>
<p>However, it isn’t made up of light that you or I are able to see with the naked eye. The type of light we can see is called visible light, but other <a href="https://justenergy.com/blog/electromagnetic-energy-understanding/">types of light</a> exist. Microwaves are a type of light, and so are the X-rays that we use to check for broken bones, and the radio waves that let us listen to music in the car. </p>
<p>At first, the CMB was very energetic X-ray light. Over time, it has lost energy and become lower-energy microwaves. </p>
<figure class="align-center ">
<img alt="Oval image of red, green and blue points of light" src="https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470131/original/file-20220621-12-318fon.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An image of the CMB from the Planck telescope. The colours show the temperature of different spots of the CMB.</span>
<span class="attribution"><a class="source" href="https://www.esa.int/ESA_Multimedia/Images/2013/03/Planck_CMB">ESA and the Planck Collaboration</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The CMB is the light from the beginning of the universe. At this point in time, the universe was very hot and dense, and full of particles called electrons and protons. These particles have an electric charge, and when light reached one of the particles, the electric charge would send the light off in another direction. This stopped the light from travelling very far.</p>
<h2>Cooling down</h2>
<p>Over time though, the universe expanded and cooled down. Eventually, once the universe became cool enough, the electrons and protons began to bind together and form atoms of hydrogen. These atoms have no electric charge, so they don’t affect light in the same way that electrons and protons do on their own. Light could pass through them and on through the universe as if it were completely empty. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.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">
<figcaption>
<span class="caption"></span>
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</figure>
<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>The universe cooled at the same rate all over, so this process happened at the same time everywhere. Suddenly, light could travel very far and fast from all over the universe at the same time. This light is still travelling today, and it’s what reaches us on Earth as the CMB now. </p>
<p>The CMB light was always around in the universe but couldn’t travel far at all until the first atoms formed. In fact, we know that it was released <a href="https://www.universetoday.com/135288/what-is-the-cosmic-microwave-background/">380,000</a> years after the Big Bang. This sounds like a long time between the Big Bang and CMB release, but since the universe is nearly 14 billion years old, this happened when the universe was very young. </p>
<p>The CMB tells us lots of important information about what the universe was like long ago. According to the Big Bang theory, the early universe was very hot and full of radiation. As the universe expanded and cooled down, this radiation would eventually be released. This is exactly what we see now as the CMB. It even has the temperature predicted by the Big Bang theory, and this is why we can say the CMB is evidence that the Big Bang theory is correct.</p>
<h2>An accidental discovery</h2>
<p>The CMB was discovered accidentally. <a href="https://www.space.com/25945-cosmic-microwave-background-discovery-50th-anniversary.html">Two scientists</a> in the US, Robert Wilson and Arno Penzias, were using a microwave telescope and kept seeing the same extra signal wherever they pointed the antenna. They thought the extra signal might be caused by a <a href="https://www.smithsonianmag.com/smithsonian-institution/how-scientists-confirmed-big-bang-theory-owe-it-all-to-a-pigeon-trap-180949741/">fault in their telescope</a> – or even by pigeon poo on their antenna. </p>
<figure class="align-center ">
<img alt="Black and white image of antenna equipment with two men standing on it" src="https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=472&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=472&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=472&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=593&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=593&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470584/original/file-20220623-51813-dm02vt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=593&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The 15m Holmdel horn antenna at Bell Telephone Laboratories in Holmdel, New Jersey was used by radio astronomers Robert Wilson and Arno Penzias to discover the CMB.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Horn_Antenna-in_Holmdel,_New_Jersey_-_restoration1.jpg">NASA via Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Eventually they realised they were the first people to ever detect the CMB, which the Big Bang theory had predicted would exist. They won the <a href="https://www.nobelprize.org/prizes/physics/1978/summary/">Nobel prize</a> for their discovery.</p>
<p>Since then, we have sent many <a href="https://www.esa.int/Enabling_Support/Operations/Planck">telescopes</a> into space to get <a href="https://www.youtube.com/watch?v=k19ZtdIxNOY&ab_channel=WIRED">better and better images</a> of the CMB. Looking at the oldest light in the universe can helps us to understand how everything we see today came to be.</p><img src="https://counter.theconversation.com/content/185537/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Pattison 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>It’s the oldest light in the universe.Christopher Pattison, Senior Research Associate at the Institute of Cosmology and Gravitation, University of PortsmouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1806232022-04-04T17:03:26Z2022-04-04T17:03:26ZMost distant star to date spotted – but how much further back in time could we see?<figure><img src="https://images.theconversation.com/files/456146/original/file-20220404-13794-xmsy6x.png?ixlib=rb-1.1.0&rect=10%2C0%2C1428%2C1500&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hubble's view of Earendel.</span> <span class="attribution"><span class="source"> Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)</span></span></figcaption></figure><p>The Hubble Space Telescope has observed <a href="https://www.bbc.co.uk/news/science-environment-60931100">the most distant star ever seen</a> – Earendel, meaning morning star. Even though Earendel is 50 times the mass of the Sun, and millions of times brighter, we would not normally be able to see it. We can see it due to an alignment of the star with a large galaxy cluster in front of it whose gravity bends the light from the star to make it brighter and more focused – essentially creating a lens.</p>
<p>Astronomers see into the deep past when we view distant objects. Light travels at a constant speed (3x10⁸ metres per second) so the further away an object is, the longer it takes for the light to reach us. By the time the light reaches us from very distant stars, the light we are looking at can be billions of years old. So we are looking at events that happened in the past.</p>
<p>When we observe the star’s light, we are looking at light that was emitted from the star 12.9 billion years ago – we call this the lookback time. That is just 900 million years after the Big Bang. But because the universe has also expanded rapidly in the time it took this light to reach us, Earendel is now 28 billion light years away from us. </p>
<p>Now that Hubble’s successor, the <a href="https://theconversation.com/james-webb-telescope-how-it-could-uncover-some-of-the-universes-best-kept-secrets-173717">James Webb Space Telescope</a> (JWST), <a href="https://theconversation.com/the-james-webb-space-telescope-has-taken-its-first-aligned-image-of-a-star-heres-how-it-was-done-178315">is in place</a> it may be able to detect even earlier stars, although there may not be many that are nicely aligned to form a “gravitational lens” so that we can see it. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0YMRuh772IA?wmode=transparent&start=4" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>To see further back in time, the objects need to be very bright. And the furthest objects we have seen are the most massive and brightest galaxies. The brightest galaxies are ones with quasars – luminous objects thought to be powered by <a href="https://theconversation.com/supermassive-black-holes-weve-spotted-signs-of-mergers-that-may-finally-help-us-prove-they-exist-105438">supermassive black holes</a> – in them. </p>
<p>Before 1998, the furthest detected quasar galaxies were about 12.6 billion years lookback time. The improved resolution of the Hubble Space Telescope increased the lookback time to 13.4 billion years, and with the JWST we expect to improve on this possibly to 13.55 billion years for galaxies and stars. </p>
<p>Stars started to form a few hundred million years after the Big Bang, in a time that we call the <a href="https://news.ucsc.edu/2021/06/cosmic-dawn.html">cosmic dawn</a>. We would like to be able to see the stars at the cosmic dawn, as this could confirm our theories on how the universe and galaxies formed. That said, research suggests we may never be able to see the most distant objects with telescopes in as much details as we like – the universe <a href="https://theconversation.com/the-universes-resolution-limit-why-we-may-never-have-a-perfect-view-of-distant-galaxies-50993">may have a fundamental resolution limit</a>.</p>
<h2>Why look back?</h2>
<p>One of the main goals of JWST is to know what the early universe looked like and when early stars and galaxies formed, thought to be between 100 million and 250 million years after the Big Bang. And, luckily, we can get hints about this by looking even further back than Hubble or the JWST can manage. </p>
<p>We can see light from 13.8 billion years ago, although it is not star light – there were no stars then. The furthest light we can see is the <a href="https://theconversation.com/the-cmb-how-an-accidental-discovery-became-the-key-to-understanding-the-universe-45126">cosmic microwave background</a> (CMB), which is the light left over from the Big Bang, forming at just 380,000 years after our cosmic birth. </p>
<p>The universe before the CMB formed contained charged particles of positive protons (which now make up the atomic nucleus along with neutrons) and negative electrons, and light. The light was scattered by the charged particles, which made the universe a foggy soup. As the universe expanded it cooled until eventually the electrons combined with the protons to form atoms. </p>
<p>Unlike the soup of particles, the atoms had no charge, so the light was no longer scattered and could move through the universe in a straight line. This light has continued to travel across the universe until it reaches us today. The wavelength of the light got longer as the universe expanded – and we currently see it as microwaves. This light is the CMB and can be seen uniformly at all points in the sky. The CMB is everywhere in the universe. </p>
<figure class="align-center ">
<img alt="Close up of Earendel." src="https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/456148/original/file-20220404-21-sb3qcz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Close up of Earendel.</span>
<span class="attribution"><span class="source">Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)</span></span>
</figcaption>
</figure>
<p>The CMB light is the furthest back in time that we have seen, and we cannot see light from earlier times because that light was scattered and the universe was opaque. </p>
<p>There is a possibility, however, that we can one day see even beyond the CMB. To do this we cannot use light – we will need to use <a href="https://theconversation.com/explainer-what-are-gravitational-waves-53239">gravitational waves</a>. These are ripples in the fabric of spacetime itself. If any formed in the fog of the very early universe, then they could potentially reach us today. </p>
<p>In 2015, gravitational waves <a href="https://theconversation.com/gravitational-waves-found-the-inside-story-54589">were detected</a> from the merging of two black holes using the LIGO detector. Maybe the next generation <a href="https://theconversation.com/lisa-pathfinder-will-pave-the-way-for-us-to-see-black-holes-for-the-first-time-51374">space-based gravitational wave detector</a> – such as Esa’s telescope Lisa, which is due for launch in 2037 – will be able to see into the very early universe before the CMB formed 13.8 billion years ago.</p><img src="https://counter.theconversation.com/content/180623/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Carolyn Devereux is affiliated with:
Royal Astronomical Society
Institute of Physics
Labour Party</span></em></p>The Hubble Space Telescope could gaze back 13.4 billion years, and with the JWST we expect to improve on this possibly to 13.55 billion years.Carolyn Devereux, Senior Lecturer in Astrophysics, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1749402022-01-24T15:10:28Z2022-01-24T15:10:28ZCurious Kids: will time ever stop?<figure><img src="https://images.theconversation.com/files/441751/original/file-20220120-8326-t062wt.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5742%2C3819&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/childrens-palms-old-clock-conceptual-photography-1448333879">Olga_Kuzmina/Shutterstock</a></span></figcaption></figure><p><strong>Will time ever stop? – Casandra, aged 11, Epsom, UK</strong></p>
<p>Time began when the universe did. How – and if – the universe ends will determine whether time will end as well. </p>
<p>We think the universe started out squeezed into an infinitely small space. For some reason we do not yet understand, the universe immediately started to expand – to get bigger and bigger. This idea, or “model”, of the beginning of the universe is called the <a href="https://www.esa.int/kids/en/learn/Our_Universe/Story_of_the_Universe/The_Big_Bang">Big Bang</a>.</p>
<p><a href="https://hubblesite.org/hubble-30th-anniversary/hubbles-exciting-universe/discovering-dark-energy">In 1998</a>, scientists learned that the universe is expanding faster and faster, but we still don’t know why this is happening. </p>
<h2>Dark energy</h2>
<p>It might have something to do with the energy of the vacuum of space. It might be a new type of energy field. Or, it might be some completely new form of physics. To symbolise our lack of understanding, we call this new phenomenon “<a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy">dark energy</a>”. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.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/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>Even though we are still trying to work out what dark energy is, we can already use it to predict different ways in which the universe might end. </p>
<p>If dark energy is not too strong, it will take an infinite amount of time for the universe to expand to an infinitely large size. Infinite means never-ending, and so in this case, time will never end. </p>
<p>But, if dark energy is too strong, it will cause the universe to expand so fast that everything in it – even the <a href="https://www.bbc.co.uk/bitesize/topics/zstp34j/articles/zc86m39">tiny atoms</a> that are the building blocks for every single thing in existence – will be ripped apart. In this <a href="https://www.wired.co.uk/article/big-rip-end-of-the-universe">Big Rip</a> scenario, the universe will not expand forever. </p>
<p>Instead, it will expand so fast that it will reach an infinitely large size at a specific moment in time. That moment, when the universe is infinitely large and all matter has been ripped apart, will be the last. The universe will cease to exist, and time will come to an end.</p>
<figure class="align-center ">
<img alt="small light galaxies on black background" src="https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441777/original/file-20220120-9349-1w4wfat.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">
<figcaption>
<span class="caption">An image of galaxies in the Virgo galaxy cluster taken from the Nasa Galaxy Evolution Explorer space telescope.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details-PIA07906">NASA/JPL-Caltech/SSC</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>There is another way that the universe might end. This is called the <a href="https://hubblesite.org/contents/media/videos/2004/12/421-Video.html?news=true">Big Crunch</a>. In this scenario, the universe will at some point stop expanding and start shrinking again. </p>
<p>The universe will get smaller and smaller, galaxies will collide with each other, and all the matter in the universe will be scrunched up together. When the universe will once again be squeezed into an infinitely small space, time will end.</p>
<h2>The Big Bounce</h2>
<p>Some physicists think that a Big Crunch may not be the end of the universe, but merely the middle of its existence. According to this way of thinking, the universe starts out infinitely large, then shrinks for an infinitely long time until it is squeezed into the smallest size possible. When that happens, instead of ending, there is a Big Bang and the universe begins to expand. </p>
<p>In this <a href="https://www.wired.com/story/what-if-the-big-bang-was-actually-a-big-bounce/">Big Bounce</a> scenario, there is an infinite amount of time before the universe becomes scrunched up into the smallest possible space, and an infinite amount of time as it expands afterwards. Time has no beginning and no end. </p>
<p>In some Big Bounce models, the universe only bounces once. In others it goes through an infinite number of bounces, constantly expanding and contracting, like an accordion that never stops playing.</p>
<p>All of these scenarios show us what is possible, not necessarily what is true. For one thing, we still need to figure out what dark energy is. More importantly, there is no guarantee that our current understanding of how the universe works is correct. </p>
<p>One day, maybe 100 years or just a few weeks from now, someone (perhaps you?) will come up with a better theory to describe the workings of the universe. Maybe then we will know whether time ever comes to and end. Then again, perhaps the new theory will have a wildly different concept of time, or even do away with it altogether.</p><img src="https://counter.theconversation.com/content/174940/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Or Graur receives funding from the UKRI Science and Technology Facilities Council. </span></em></p>Time ends when the universe does.Or Graur, Senior Lecturer in Astrophysics, University of PortsmouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1719862022-01-03T14:11:11Z2022-01-03T14:11:11ZHow could the Big Bang arise from nothing?<figure><img src="https://images.theconversation.com/files/434028/original/file-20211125-15-n9woro.jpg?ixlib=rb-1.1.0&rect=8%2C301%2C5725%2C3587&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The evolution of the cosmos after the Big Bang</span> <span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/10128">NASA</a></span></figcaption></figure><p><strong>READER QUESTION:</strong> <em>My understanding is that nothing comes from nothing. For something to exist, there must be material or a component available, and for them to be available, there must be something else available. Now my question: Where did the material come from that created the Big Bang, and what happened in the first instance to create that material? Peter, 80, Australia.</em></p>
<p>“The last star will slowly cool and fade away. With its passing, the universe will become once more a void, without light or life or meaning.” So warned the physicist Brian Cox in the recent BBC series <a href="https://www.bbc.co.uk/iplayer/episode/p09ybpb8/universe-series-1-1-the-sun-god-star">Universe</a>. The fading of that last star will only be the beginning of an infinitely long, dark epoch. All matter will eventually be consumed by monstrous black holes, which in their turn will evaporate away into the dimmest glimmers of light. Space will expand ever outwards until even that dim light becomes too spread out to interact. Activity will cease.</p>
<p>Or will it? Strangely enough, some cosmologists believe a previous, cold dark empty universe like the one which lies in our far future could have been the source of our very own Big Bang.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313328/original/file-20200203-41485-1foofme.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This article is part of <a href="https://theconversation.com/uk/topics/lifes-big-questions-80040?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=LifesBigQuestionsUK">Life’s Big Questions</a></em></strong>
<br><em>The Conversation’s new series, co-published with BBC Future, seeks to answer our readers’ nagging questions about life, love, death and the universe. We work with professional researchers who have dedicated their lives to uncovering new perspectives on the questions that shape our lives.</em></p>
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<h2>The first matter</h2>
<p>But before we get to that, let’s take a look at how “material” – physical matter – first came about. If we are aiming to explain the origins of stable matter made of atoms or molecules, there was certainly none of that around at the Big Bang – nor for hundreds of thousands of years afterwards. We do in fact have a pretty detailed understanding of how the first atoms formed out of simpler particles once conditions cooled down enough for complex matter to be stable, and how these atoms were later fused into heavier elements inside stars. But that understanding doesn’t address the question of whether something came from nothing.</p>
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<p>So let’s think further back. The first long-lived matter particles of any kind were protons and neutrons, which together make up the atomic nucleus. These came into existence around one ten-thousandth of a second after the Big Bang. Before that point, there was really no material in any familiar sense of the word. But physics lets us keep on tracing the timeline backwards – to physical processes which predate any stable matter.</p>
<p>This takes us to the so-called “<a href="http://ffden-2.phys.uaf.edu/webproj/211_fall_2016/Trevor_Jepsen/trevor_jepsen/Grand_unification.html">grand unified epoch</a>”. By now, we are well into the realm of speculative physics, as we can’t produce enough energy in our experiments to probe the sort of processes that were going on at the time. But a plausible hypothesis is that the physical world was made up of a soup of short-lived elementary particles – including quarks, the building blocks of protons and neutrons. There was both matter and “antimatter” in <a href="https://theconversation.com/cern-discovery-sheds-light-on-the-great-mystery-of-why-the-universe-has-less-antimatter-than-matter-147226">roughly equal quantities</a>: each type of matter particle, such as the quark, has an antimatter “mirror image” companion, which is near identical to itself, differing only in one aspect. However, matter and antimatter annihilate in a flash of energy when they meet, meaning these particles were constantly created and destroyed.</p>
<p>But how did these particles come to exist in the first place? Quantum field theory tells us that even a vacuum, supposedly corresponding to empty spacetime, is full of physical activity in the form of energy fluctuations. These fluctuations can give rise to particles popping out, only to be disappear shortly after. This may sound like a mathematical quirk rather than real physics, but such particles have been spotted in countless experiments.</p>
<p>The spacetime vacuum state is seething with particles constantly being created and destroyed, apparently “out of nothing”. But perhaps all this really tells us is that the quantum vacuum is (despite its name) a something rather than a nothing. The philosopher David Albert has <a href="https://www.nytimes.com/2012/03/25/books/review/a-universe-from-nothing-by-lawrence-m-krauss.html">memorably criticised</a> accounts of the Big Bang which promise to get something from nothing in this way. </p>
<figure class="align-center ">
<img alt="Image of a simulation of quantum vacuum fluctuations." src="https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437872/original/file-20211215-25-iapu5n.gif?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">
<figcaption>
<span class="caption">Simulation of quantum vacuum fluctuations in quantum chromodynamics.</span>
<span class="attribution"><span class="source">Wikimedia/Ahmed Neutron</span></span>
</figcaption>
</figure>
<p>Suppose we ask: where did spacetime itself arise from? Then we can go on turning the clock yet further back, into the truly ancient “<a href="http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/eraplanck.htm">Planck epoch</a>” – a period so early in the universe’s history that our best theories of physics break down. This era occurred only one ten-millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang. At this point, space and time themselves became subject to quantum fluctuations. Physicists ordinarily work separately with quantum mechanics, which rules the microworld of particles, and with general relativity, which applies on large, cosmic scales. But to truly understand the Planck epoch, we need a complete theory of quantum gravity, merging the two.</p>
<p>We still don’t have a perfect theory of quantum gravity, but there are attempts – like <a href="https://en.wikipedia.org/wiki/String_theory">string theory</a> and <a href="https://en.wikipedia.org/wiki/Loop_quantum_gravity">loop quantum gravity</a>. In these attempts, ordinary space and time are typically seen as emergent, like the waves on the surface of a deep ocean. What we experience as space and time are the product of quantum processes operating at a deeper, microscopic level – processes that don’t make much sense to us as creatures rooted in the macroscopic world.</p>
<p>In the Planck epoch, our ordinary understanding of space and time breaks down, so we can’t any longer rely on our ordinary understanding of cause and effect either. Despite this, all candidate theories of quantum gravity describe something physical that was going on in the Planck epoch – some quantum precursor of ordinary space and time. But where did <em>that</em> come from?</p>
<p>Even if causality no longer applies in any ordinary fashion, it might still be possible to explain one component of the Planck-epoch universe in terms of another. Unfortunately, by now even our best physics fails completely to provide answers. Until we make further progress towards a “theory of everything”, we won’t be able to give any definitive answer. The most we can say with confidence at this stage is that physics has so far found no confirmed instances of something arising from nothing.</p>
<h2>Cycles from almost nothing</h2>
<p>To truly answer the question of how something could arise from nothing, we would need to explain the quantum state of the entire universe at the beginning of the Planck epoch. All attempts to do this remain highly speculative. Some of them appeal to supernatural forces like <a href="https://global.oup.com/academic/product/the-existence-of-god-9780199271689?cc=gb&lang=en&">a designer</a>. But other candidate explanations remain within the realm of physics – such as a multiverse, which contains an infinite number of parallel universes, or cyclical models of the universe, being born and reborn again.</p>
<p>The 2020 Nobel Prize-winning physicist <a href="https://www.nobelprize.org/prizes/physics/2020/penrose/facts/">Roger Penrose</a> has proposed one intriguing but controversial <a href="https://en.wikipedia.org/wiki/Cycles_of_Time">model for a cyclical universe</a> dubbed “conformal cyclic cosmology”. Penrose was inspired by an interesting mathematical connection between a very hot, dense, small state of the universe – as it was at the Big Bang – and an extremely cold, empty, expanded state of the universe – as it will be in the far future. His radical theory to explain this correspondence is that those states become mathematically identical when taken to their limits. Paradoxical though it might seem, a total absence of matter might have managed to give rise to all the matter we see around us in our universe.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/DpPFn0qzYT0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>In this view, the Big Bang arises from an almost nothing. That’s what’s left over when all the matter in a universe has been consumed into black holes, which have in turn boiled away into photons – lost in a void. The whole universe thus arises from something that – viewed from another physical perspective – is as close as one can get to nothing at all. But that nothing is still a kind of something. It is still a physical universe, however empty.</p>
<p>How can the very same state be a cold, empty universe from one perspective and a hot dense universe from another? The answer lies in a complex mathematical procedure called “conformal rescaling”, a geometrical transformation which in effect alters the size of an object but leaves its shape unchanged.</p>
<p>Penrose showed how the cold empty state and the hot dense state could be related by such rescaling so that they match with respect to the shapes of their spacetimes – although not to their sizes. It is, admittedly, difficult to grasp how two objects can be identical in this way when they have different sizes – but Penrose argues size as a concept ceases to make sense in such extreme physical environments. </p>
<p>In conformal cyclic cosmology, the direction of explanation goes from old and cold to young and hot: the hot dense state exists <em>because of</em> the cold empty state. But this “because” is not the familiar one – of a cause followed in time by its effect. It is not only size that ceases to be relevant in these extreme states: time does too. The cold empty state and the hot dense state are in effect located on different timelines. The cold empty state would continue on forever from the perspective of an observer in its own temporal geometry, but the hot dense state it gives rise to effectively inhabits a new timeline all its own.</p>
<p>It may help to understand the hot dense state as produced from the cold empty state in some non-causal way. Perhaps we should say that the hot dense state <em>emerges from</em>, or is <em>grounded in</em>, or <em>realised by</em> the cold, empty state. These are distinctively metaphysical ideas which have been <a href="https://framephys.org/">explored by philosophers of science</a> extensively, especially <a href="https://beyondspacetime.net/">in the context of quantum gravity </a> where ordinary cause and effect seem to break down. At the limits of our knowledge, physics and philosophy become hard to disentangle.</p>
<h2>Experimental evidence?</h2>
<p>Conformal cyclic cosmology offers some detailed, albeit speculative, answers to the question of where our Big Bang came from. But even if Penrose’s vision is vindicated by the future progress of cosmology, we might think that we still wouldn’t have answered a deeper philosophical question – a question about where physical reality itself came from. How did the whole system of cycles come about?
Then we finally end up with the pure question of why there is something rather than nothing – one of the biggest questions of metaphysics.</p>
<p>But our focus here is on explanations which remain within the realm of physics. There are three broad options to the deeper question of how the cycles began. It could have no physical explanation at all. Or there could be endlessly repeating cycles, each a universe in its own right, with the initial quantum state of each universe explained by some feature of the universe before. Or there could be one single cycle, and one single repeating universe, with the beginning of that cycle explained by some feature of its own end. The latter two approaches avoid the need for any uncaused events – and this gives them a distinctive appeal. Nothing would be left unexplained by physics. </p>
<figure class="align-center ">
<img alt="Image of Penrose's ongoing cycles of distinct universes." src="https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=612&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=612&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=612&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=769&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=769&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437868/original/file-20211215-21-1o5dc69.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=769&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ongoing cycles of distinct universes in conformal cyclic cosmology.</span>
<span class="attribution"><span class="source">Roger Penrose</span></span>
</figcaption>
</figure>
<p>Penrose envisages a sequence of endless new cycles for reasons partly linked to his own preferred interpretation of quantum theory. In quantum mechanics, a physical system exists in a superposition of many different states at the same time, and only “picks one” randomly, when we measure it. For Penrose, each cycle involves random quantum events turning out a different way – meaning each cycle will differ from those before and after it. This is actually good news for experimental physicists, because it might allow us to glimpse the old universe that gave rise to ours through faint traces, or anomalies, in the leftover radiation from the Big Bang seen by the Planck satellite. </p>
<p>Penrose and his collaborators believe <a href="https://academic.oup.com/mnras/article/495/3/3403/5838759">they may have spotted</a> these traces already, attributing patterns in the Planck data to radiation from supermassive black holes in the previous universe. However, their claimed observations have been <a href="https://iopscience.iop.org/article/10.1088/1475-7516/2020/03/021">challenged by other physicists</a> and the jury remains out.</p>
<figure class="align-center ">
<img alt="Map of the cosmic microwave background radiation." src="https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437871/original/file-20211215-17-3hqkn0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Map of the cosmic microwave background radiation.</span>
<span class="attribution"><span class="source">ESA and the Planck Collaboration</span></span>
</figcaption>
</figure>
<p>Endless new cycles are key to Penrose’s own vision. But there is a natural way to convert conformal cyclic cosmology from a multi-cycle to a one-cycle form. Then physical reality consists in a single cycling around through the Big Bang to a maximally empty state in the far future – and then around again to the very same Big Bang, giving rise to the very same universe all over again. </p>
<p>This latter possibility is consistent with another interpretation of quantum mechanics, dubbed the many-worlds interpretation. The many-worlds interpretation tells us that each time we measure a system that is in superposition, this measurement doesn’t randomly select a state. Instead, the measurement result we see is just one possibility – the one that plays out in our own universe. The other measurement results all play out in other universes in a multiverse, effectively cut off from our own. So no matter how small the chance of something occurring, if it has a non-zero chance then it occurs in some quantum parallel world. There are people just like you out there in other worlds who have won the lottery, or have been swept up into the clouds by a freak typhoon, or have spontaneously ignited, or have done all three simultaneously.</p>
<p>Some people believe such parallel universes <a href="https://theconversation.com/could-cold-spot-in-the-sky-be-a-bruise-from-a-collision-with-a-parallel-universe-78563">may also be observable</a> in cosmological data, as imprints caused by another universe colliding with ours.</p>
<p>Many-worlds quantum theory gives a new twist on conformal cyclic cosmology, though not one that Penrose agrees with. Our Big Bang might be the rebirth of one single quantum multiverse, containing infinitely many different universes all occurring together. Everything possible happens – then it happens again and again and again.</p>
<h2>An ancient myth</h2>
<p>For a philosopher of science, Penrose’s vision is fascinating. It opens up new possibilities for explaining the Big Bang, taking our explanations beyond ordinary cause and effect. It is therefore a great test case for exploring the different ways physics can explain our world. It deserves more attention from philosophers.</p>
<p>For a lover of myth, Penrose’s vision is beautiful. In Penrose’s preferred multi-cycle form, it promises endless new worlds born from the ashes of their ancestors. In its one-cycle form, it is a striking modern re-invocation of the ancient idea of the ouroboros, or world-serpent. In Norse mythology, the serpent Jörmungandr is a child of Loki, a clever trickster, and the giant Angrboda. Jörmungandr consumes its own tail, and the circle created sustains the balance of the world. But the ouroboros myth has been documented all over the world – including as far back as ancient Egypt.</p>
<figure class="align-center ">
<img alt="Image of stone ouroboros carved on the tomb of Tutankhamun" src="https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434029/original/file-20211125-17-89mxlf.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">Ouroboros on the tomb of Tutankhamun.</span>
<span class="attribution"><span class="source">Djehouty/Wikimedia</span></span>
</figcaption>
</figure>
<p>The ouroboros of the one cyclic universe is majestic indeed. It contains within its belly our own universe, as well as every one of the weird and wonderful alternative possible universes allowed by quantum physics – and at the point where its head meets its tail, it is completely empty yet also coursing with energy at temperatures of a hundred thousand million billion trillion degrees Celsius. Even Loki, the shapeshifter, would be impressed.</p>
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<li><p><em><a href="https://theconversation.com/happiness-is-feeling-content-more-important-than-purpose-and-goals-131503?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=LifesBigQuestionsUK">Happiness: is contentment more important than purpose and goals?</a></em></p></li>
<li><p><em><a href="https://theconversation.com/could-we-live-in-a-world-without-rules-128664?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=LifesBigQuestionsUK">Could we live in a world without rules?</a></em></p></li>
<li><p><em><a href="https://theconversation.com/death-can-our-final-moment-be-euphoric-129648?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=LifesBigQuestionsUK">Death: can our final moment be euphoric?</a></em></p></li>
<li><p><em><a href="https://theconversation.com/are-humans-still-part-of-nature-or-is-it-now-just-our-dominion-128790?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=LifesBigQuestionsUK">Nature: have humans now evolved beyond the natural world, and do we still need it?</a></em></p></li>
<li><p><em><a href="https://theconversation.com/love-is-it-just-a-fleeting-high-fuelled-by-brain-chemicals-129201?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=LifesBigQuestionsUK">Love: is it just a fleeting high fuelled by brain chemicals?</a></em></p></li>
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<p class="fine-print"><em><span>Alastair Wilson receives funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 757295), and from the Australian Research Council (grant agreement no. DP180100105).</span></em></p>Some argue the Big Bang was a rebirth rather than a birth.Alastair Wilson, Professor of Philosophy, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1695622021-11-04T16:05:35Z2021-11-04T16:05:35ZYour smile’s cosmic history: we discovered the origin of fluoride in early galaxies<figure><img src="https://images.theconversation.com/files/430101/original/file-20211103-25-10jnbn2.jpg?ixlib=rb-1.1.0&rect=0%2C74%2C958%2C834&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Flouride is created by Wolf–Rayet stars, here seen in the Milky Way by the Hubble Space Telescope. </span> <span class="attribution"><span class="source">Nasa/Judy Schmidt</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Look at the ingredients on a tube of toothpaste and you will probably read something like “contains sodium fluoride”. Fluoride, as you probably know, is important for healthy teeth. <a href="https://www.nature.com/articles/news040119-8">It strengthens enamel</a>, the hard, protective layer around a tooth, and so helps prevent cavities. </p>
<p>You may not think too deeply about toothpaste. But like all things on Earth, from the majestic to the mundane, fluoride - and the story of a smile - has a cosmic origin. Now, my colleagues and I have <a href="https://www.nature.com/articles/s41550-021-01515-9">published a paper in Nature Astronomy</a> that sheds some light on it.</p>
<p>Virtually all natural elements were formed long ago in the history of the universe. Hydrogen is the oldest element: it formed very shortly after the big bang, about 14 billion years ago. Within a few minutes of the big bang, the light elements <a href="https://w.astro.berkeley.edu/%7Emwhite/darkmatter/bbn.html">helium, deuterium and lithium</a> were also formed in a process called <a href="https://w.astro.berkeley.edu/%7Emwhite/darkmatter/bbn.html">big bang nucleosynthesis</a>. Since then, nearly every other element has been forged in processes associated with the <a href="https://theconversation.com/piercing-the-mystery-of-the-cosmic-origins-of-gold-88880">life and death of stars</a>. But those stars were not always around. </p>
<figure class="align-center ">
<img alt="Image of toothpaste." src="https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430041/original/file-20211103-25-f9f941.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Do you consider the cosmic origins of your toothpaste when brushing your teeth?</span>
<span class="attribution"><span class="source">Pixabay</span></span>
</figcaption>
</figure>
<p>We still don’t know exactly when the first stars ignited in the universe, but it probably didn’t happen for about <a href="https://theconversation.com/after-our-universes-cosmic-dawn-what-happened-to-all-its-original-hydrogen-65527">100 million years or so after the big bang</a>. Before this, the universe was filled with a fog of hydrogen, mingled with the mysterious, invisible substance astronomers call dark matter. This fog was not smooth, but rippled - slightly denser in some places. It was these regions that started to contract, or “collapse”, due to gravity, to form the first galaxies. Where the gas got dense enough, stars ignited and lit up the universe.</p>
<p>The following few billion years was a time of rapid growth: the rate of star formation in the universe rose sharply until it reached a peak, 8 to 10 billion years ago. Ever since that “cosmic noon”, the overall rate of star formation in the universe has been in decline. That’s why astronomers are so interested in the early phases of the history of the cosmos: what happened then shaped what we see around us today. </p>
<p>While we have quite a lot of information about how the growth of galaxies “ramped up” in terms of their star formation, we have relatively little insight into their chemical evolution at the earliest times. This is important because, as stars live and die, the elements they produce become dispersed throughout a galaxy and beyond. Many years later, some of those elements can form new planets like ours. </p>
<h2>Rapid evolution</h2>
<p>We observed a distant galaxy called NGP-190387 with the <a href="https://www.almaobservatory.org/en/home/">Atacama Large Millimetre/sub-millimetre Array</a> (Alma) - a telescope that detects light with a wavelength of around one millimetre. This allows us to see the light emitted by cold dust and gas in distant galaxies. The data revealed something unexpected: a dip in the light at a wavelength of exactly 1.32 millimetres. This corresponds exactly to the wavelength at which the molecule hydrogen fluoride (HF), comprising a hydrogen atom and fluorine atom, absorbs light (taking into account a shift in wavelength that happens due to the universe’s expansion). The deficit of light implies the presence of clouds of hydrogen fluoride gas in the galaxy. This light has taken over 12 billion years to reach us, and we see the galaxy as it was when the universe was 1.4 billion years old.</p>
<p>This is exciting, because it provides information about how galaxies first became enriched with chemical elements shortly after they first formed. We can see that even at this early time, NGP-190387 had a high abundance of fluorine. Although we have observed other elements in distant galaxies, such as carbon, nitrogen and oxygen, this is the first time fluorine has been detected in a star-forming galaxy at such a distance. The greater the variety of elements we can observe in early galaxies, the better our understanding of the process of chemical enrichment at that time.</p>
<p>We know that fluorine can be produced in different ways: for example, in star explosions called supernovas and in certain <a href="https://en.wikipedia.org/wiki/Asymptotic_giant_branch">“asymptotic giant branch”</a> stars - red supergiant stars nearing the end of their life, having burned most of the hydrogen and helium in their cores and now swollen in size. </p>
<p>Models of how elements form in stars and in supernovae can tell us how much fluorine we should expect from these sources. And we found that the abundance of fluorine was too high in NGP-190387 to be explained by supernovas and asymptotic giant branch stars alone. An extra source was needed, and this is probably another type of star called a <a href="https://astronomy.swin.edu.au/cosmos/w/wolf-rayet+star">Wolf-Rayet</a>. Wolf-Rayet stars are quite rare – there are only a few hundred catalogued in the Milky Way, for example. But they are extreme. </p>
<figure class="align-center ">
<img alt="The Hubble Ultra Deep Field" src="https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430034/original/file-20211103-27-o51gsc.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">Ancient galaxies seen by the Hubble Space Telescpope.</span>
<span class="attribution"><span class="source">NASA/ESA</span></span>
</figcaption>
</figure>
<p>Wolf-Rayet stars are a phase in the lifecycle of very massive stars – with more than ten times the mass of our Sun. Approaching the end of their short life, these stars burn helium in their cores, and are millions of times more luminous than the Sun. Unusually, Wolf-Rayet stars have lost their envelope of hydrogen via powerful winds, leaving the helium core exposed. They will eventually explode in dramatic core-collapse supernova explosions. When we added the amount of fluorine expected from Wolf-Rayet stars to our model, we could finally account for the dip in light from NGP-190387. </p>
<p>This adds to a growing body of evidence that shows that the growth of galaxies was surprisingly fast-paced in the early universe: a frenzy of star formation and chemical enrichment. Those processes lay the foundations for the universe we see around us today, and this work provides new insight into the detailed astrophysics at play, over 12 billion years ago. </p>
<p>But perhaps the main take away is that it shows that the story of your smile is a tale as old as time.</p><img src="https://counter.theconversation.com/content/169562/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Geach receives funding from The Royal Society and the Science and Technology Facilities Council. </span></em></p>Tracing the cosmic origin of toothpaste, scientists got a glimpse into the surprising chemistry of early galaxies.James Geach, Professor of Astrophysics and Royal Society University Research Fellow, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1696032021-10-12T19:31:56Z2021-10-12T19:31:56ZThe most powerful space telescope ever built will look back in time to the Dark Ages of the universe<figure><img src="https://images.theconversation.com/files/425795/original/file-20211011-27-1pyo32m.jpeg?ixlib=rb-1.1.0&rect=35%2C72%2C951%2C833&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hubble took pictures of the oldest galaxies it could – seen here – but the James Webb Space Telescope can go back much farther in time.</span> <span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/vis/a030000/a030900/a030946/hudf-hst-6200x6200_print.jpg">NASA</a></span></figcaption></figure><p>Some have called NASA’s James Webb Space Telescope the “<a href="https://doi.org/10.1038/4671028a">telescope that ate astronomy</a>.” It is the <a href="https://www.jwst.nasa.gov/">most powerful space telescope</a> ever built and a complex piece of mechanical origami that has pushed the limits of human engineering. On Dec. 25, 2021, after years of delays and billions of dollars in cost overruns, the telescope is <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-on-the-team-explains-how-to-send-a-giant-telescope-to-space-and-why-167516">launched into space</a> to usher in the next era of astronomy.</p>
<p>I’m an <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">astronomer</a> with a specialty in observational cosmology – I’ve been studying distant galaxies for 30 years. Some of the biggest unanswered questions about the universe relate to its early years just after the Big Bang. When did the first stars and galaxies form? Which came first, and why? I am incredibly excited that astronomers may soon uncover the story of how galaxies started because James Webb was built specifically to answer these very questions. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphic showing the progression of the Universe through time." src="https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425594/original/file-20211010-23-1ff1ae6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Universe went through a period of time known as the Dark Ages before stars or galaxies emitted any light.</span>
<span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/4352-Image">Space Telescope Institute</a></span>
</figcaption>
</figure>
<h2>The ‘Dark Ages’ of the universe</h2>
<p>Excellent evidence shows that the universe started with an event called the <a href="https://www.space.com/40370-why-should-we-believe-big-bang.html">Big Bang</a> 13.8 billion years ago, which left it in an ultra-hot, ultra-dense state. The universe immediately began expanding after the Big Bang, cooling as it did so. One second after the Big Bang, the universe was a hundred trillion miles across with an average temperature of an incredible 18 billion F (10 billion C). Around 400,000 years after the Big Bang, the universe was 10 million light years across and the <a href="http://www.astro.ucla.edu/%7Ewright/BBhistory.html">temperature had cooled</a> to 5,500 F (3,000 C). If anyone had been there to see it at this point, the universe would have been glowing dull red like a giant heat lamp.</p>
<p>Throughout this time, space was filled with a smooth soup of high energy particles, radiation, hydrogen and helium. There was no structure. As the expanding universe became bigger and colder, the soup thinned out and everything faded to black. This was the start of what astronomers call the <a href="https://astronomy.com/magazine/news/2021/01/the-beginning-to-the-end-of-the-universe-the-cosmic-dark-ages">Dark Ages</a> of the universe.</p>
<p>The soup of the Dark Ages was <a href="https://wmap.gsfc.nasa.gov/universe/bb_cosmo_fluct.html">not perfectly uniform</a> and due to gravity, tiny areas of gas began to clump together and become more dense. The smooth universe became lumpy and these small clumps of denser gas were seeds for the eventual formation of stars, galaxies and everything else in the universe. </p>
<p>Although there was nothing to see, the Dark Ages were an important phase in the evolution of the universe.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing different wavelengths of light compared to size of normal objects." src="https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=236&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=236&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=236&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=296&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=296&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425792/original/file-20211011-17-126iwpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=296&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Light from the early universe is in the infrared wavelength – meaning longer than red light – when it reaches Earth.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:EM_Spectrum_Properties_edit.svg#/media/File:EM_Spectrum_Properties_edit.svg">Inductiveload/NASA via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Looking for the first light</h2>
<p>The Dark Ages ended when gravity formed the first stars and galaxies that eventually began to emit the first light. Although astronomers don’t know when first light happened, the best guess is that it was <a href="https://earthsky.org/space/cosmic-dark-ages-lyman-alpha-galaxies-lager/">several hundred million years</a> after the Big Bang. Astronomers also don’t know whether stars or galaxies formed first. </p>
<p><a href="https://astronomy.com/magazine/greatest-mysteries/2019/07/20-did-stars-galaxies-or-black-holes-come-first">Current theories</a> based on how gravity forms structure in a universe dominated by dark matter suggest that small objects – like stars and star clusters – likely formed first and then later grew into dwarf galaxies and then larger galaxies like the Milky Way. These first stars in the universe were extreme objects compared to stars of today. They were <a href="https://webbtelescope.org/resource-gallery/articles/pagecontent/filter-articles/what-were-the-first-stars-like?filterUUID=a776e097-0c60-421c-baec-1d8ad049bfb0">a million times brighter</a> but they lived very short lives. They burned hot and bright and when they died, they left behind <a href="https://astronomy.com/magazine/greatest-mysteries/2019/07/20-did-stars-galaxies-or-black-holes-come-first">black holes</a> up to a hundred times the Sun’s mass, which might have <a href="https://astronomynow.com/2020/03/24/how-to-seed-supermassive-black-holes-in-the-early-universe/">acted as the seeds for galaxy formation</a>. </p>
<p>Astronomers would love to study this fascinating and important era of the universe, but detecting first light is incredibly challenging. Compared to massive, bright galaxies of today, the first objects were very small and due to the constant expansion of the universe, they’re now tens of billions of light years away from Earth. Also, the earliest stars were surrounded by gas left over from their formation and this gas acted like fog that absorbed most of the light. It took several hundred million years for <a href="https://www.quantamagazine.org/how-the-cosmic-dark-ages-snuffed-out-all-light-20200302/">radiation to blast away the fog</a>. This early light is very faint by the time it gets to Earth. </p>
<p>But this is not the only challenge.</p>
<p>As the universe expands, it continuously stretches the wavelength of light traveling through it. This is called <a href="https://www.esa.int/Science_Exploration/Space_Science/What_is_red_shift#:%7E:text=Ever%20since%201929%2C%20when%20Edwin,is%20'red%2Dshifted">redshift</a> because it shifts light of shorter wavelengths – like blue or white light – to longer wavelengths like red or infrared light. Though not a perfect analogy, it is similar to how when a car drives past you, the pitch of any sounds it is making drops noticeably. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8WgSQlRymwE?wmode=transparent&start=35" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Similar to how a pitch of a sound drops if the source is moving away from you, the wavelength of light stretches due to the expansion of the universe.</span></figcaption>
</figure>
<p>By the time light emitted by an early star or galaxy 13 billion years ago reaches any telescope on Earth, it has been stretched by a factor of 10 by the expansion of the universe. It arrives as infrared light, meaning it has a wavelength longer than that of red light. To see first light, you have to be looking for infrared light.</p>
<p>[<em>The Conversation’s science, health and technology editors pick their favorite stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-favorite">Weekly on Wednesdays</a>.]</p>
<h2>Telescope as a time machine</h2>
<p>Enter the James Webb Space Telescope. </p>
<p>Telescopes are like time machines. If an object is 10,000 light-years away, that means the light takes 10,000 years to reach Earth. So the further out in space astronomers look, the <a href="https://astronomy.swin.edu.au/cosmos/l/lookback+time">further back in time we are looking</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large golden colored disc with a sensor in the middle and scientists standing below." src="https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=493&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=493&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425798/original/file-20211011-25-fi5m9g.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=493&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The James Webb Space Telescope was specifically designed to detect the oldest galaxies in the universe.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/webb/images/index.html">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Engineers <a href="https://www.jwst.nasa.gov/content/science/firstLight.html">optimized James Webb</a> for specifically detecting the faint infrared light of the earliest stars or galaxies. Compared to the Hubble Space Telescope, <a href="https://www.jwst.nasa.gov/content/about/comparisonWebbVsHubble.html">James Webb has a 15 times wider field of view on its camera</a>, collects six times more light and its sensors are tuned to be most sensitive to infrared light.</p>
<p>The strategy will be to <a href="https://www.nasa.gov/feature/goddard/2021/mapping-the-universes-earliest-structures-with-cosmos-webb">stare deeply at one patch of sky for a long time</a>, collecting as much light and information from the most distant and oldest galaxies as possible. With this data, it may be possible to answer when and how the Dark Ages ended, but there are many other important discoveries to be made. For example, unraveling this story may also <a href="https://doi.org/10.1093/mnras/stz1924">help explain the nature of dark matter</a>, the mysterious form of matter that makes up about <a href="https://www.space.com/20930-dark-matter.html">80% of the mass of the universe</a>. </p>
<p>James Webb is the <a href="https://futurism.com/james-webb-telescope-budget-delay">most technically difficult mission</a> NASA has ever attempted. But I think the scientific questions it may help answer will be worth every ounce of effort. I and other astronomers are waiting excitedly for the data to start coming back sometime in 2022.</p>
<p><em>This article was updated with the launch.</em></p><img src="https://counter.theconversation.com/content/169603/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation and the Hearst Foundation.</span></em></p>The James Webb Space Telescope is set to launch into orbit in December 2021. Its mission is to search for the first light to ever shine in the universe.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1645022021-07-15T15:06:58Z2021-07-15T15:06:58ZBig bang: how we are trying to ‘listen’ to it – and the new physics it could unveil<figure><img src="https://images.theconversation.com/files/411445/original/file-20210715-32735-1ak3sbm.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5000%2C2813&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What happened during the Big Bang?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/big-bang-space-birth-universe-3d-1052269634"> FlashMovie/Shutterstock</a></span></figcaption></figure><p>Exactly what happened at the beginning of the universe, 14 billion years ago, is one of the greatest mysteries in physics – there’s no simple way to probe it. That’s because, <a href="https://theconversation.com/what-would-it-have-been-like-to-witness-the-beginning-of-the-universe-90043">in its early stages</a>, the universe was filled with a dense plasma – a gas made out of charged particles including electrons and protons (particles that comprise the atomic nucleus alongside neutrons). Photons (particles of light) were trapped in the mix, bouncing off the other particles furiously, with no way to escape.</p>
<p>As the universe expanded and the density decreased enough, photons could finally escape and light started travelling freely. This event, happening 380,000 years after the big bang, dubbed “recombination”, gave rise to the first snapshot of the universe’s origin – the <a href="https://theconversation.com/the-cmb-how-an-accidental-discovery-became-the-key-to-understanding-the-universe-45126">cosmic microwave background</a> – which we observe with telescopes. Most of what we know about the early universe is based on this leftover radiation from the big bang. But recombination acts like a wall: we cannot directly probe earlier epochs with telescopes, as light was trapped at that time.</p>
<p>Now several projects are trying to listen to the big bang using gravitational waves – <a href="https://theconversation.com/explainer-what-are-gravitational-waves-53239">ripples in the very fabric of spacetime</a>. Our <a href="http://www.ctc.cam.ac.uk/activities/UHF-GW.php">new project</a>, will aim to detect such waves at ultra-high frequencies, and could lead to the discovery of brand new physics.</p>
<p>The recent <a href="https://theconversation.com/gravitational-waves-found-the-inside-story-54589">detections of gravitational waves</a>, <a href="https://theconversation.com/explainer-what-are-gravitational-waves-53239">ripples in the very fabric of spacetime</a>, by the <a href="https://theconversation.com/gravitational-waves-discovered-how-did-the-experiment-at-ligo-actually-work-54510">Ligo/Virgo experiments</a> have opened <a href="https://theconversation.com/scientists-behind-the-discovery-of-gravitational-waves-win-the-2017-nobel-prize-for-physics-66457">a new window of observation</a> onto the universe. They enable us to investigate phenomena in which gravity, instead of light, is the messenger. The gravitational waves detected so far are called astrophysical gravitational waves – they are created by relatively recent physical processes, such as mergers of black holes. </p>
<p>The type of waves that might be produced in the early universe are called <a href="https://iopscience.iop.org/article/10.1088/1361-6382/aac608">cosmological gravitational waves</a> and have not yet been detected. Such waves travel freely after being produced; they act like ghosts that can go through the recombination wall and provide a unique tool to investigate the early universe. While astrophysical gravitational waves come from a precise direction in the sky, cosmological ones reach us from all possible directions, corresponding to different regions where they were produced in the past. This makes them very hard to detect.</p>
<p>But the reward of being able to detect cosmological gravitational waves would be huge: there are many possible cataclysmic phenomena in the early universe that could produce them. <a href="https://www.newscientist.com/article/mg21829224-100-cosmic-preheating-baked-planets-stars-and-people/">Preheating</a>, for instance, can be thought of as a series of explosions during which the energy was transferred from the unknown particles driving <a href="https://theconversation.com/shape-of-the-universe-could-it-be-curved-not-flat-126721">inflation</a> – an era when the universe blew up in size – to particles described in the <a href="https://theconversation.com/the-standard-model-of-particle-physics-the-absolutely-amazing-theory-of-almost-everything-94700">Standard Model of particle physics</a> today. This occurred when the universe was a fraction of a second old, immediately after the end of inflation. It is also very likely that the universe changed state a few times (as water does when boiled) during its first second: such events are called phase transitions.</p>
<p>Processes involving yet undiscovered particles such as <a href="https://www.scientificamerican.com/article/is-dark-matter-made-of-axions/">axions</a> (which may make up dark matter) could also have produced the waves. So if cosmological gravitational waves are detected, they could give us crucial information about what happened at the beginning of time.</p>
<h2>High versus low frequency</h2>
<p>Current and <a href="https://theconversation.com/lisa-pathfinder-will-pave-the-way-for-us-to-see-black-holes-for-the-first-time-51374">planned</a> gravitational wave detectors mostly focus on low frequencies, where astrophysical signals are guaranteed to exist. These can also look for cosmological gravitational waves and will be able to probe signals produced when the universe was extremely young, bar <a href="https://theconversation.com/shape-of-the-universe-could-it-be-curved-not-flat-126721">the very first moments</a> after inflation.</p>
<p>That’s because the wavelength of a produced wave is proportional to the “size” of the universe (that is expanding). The earlier it was produced, the smaller the corresponding wavelength – and the higher the frequency. The era immediately after the end of inflation is what we are aiming to probe with our new project. This covers times when we could see actual evidence for some of the most fascinating theories of nature, such as <a href="https://theconversation.com/stephen-hawking-had-pinned-his-hopes-on-m-theory-to-fully-explain-the-universe-heres-what-it-is-93440">string theory</a>.</p>
<p>There are also other possible sources that would produce high-frequency gravitational waves in the more recent universe. Examples include mysterious objects called boson stars (stars made out of elementary particles called bosons) or “primordial black holes”, which <a href="https://www.quantamagazine.org/black-holes-from-the-big-bang-could-be-the-dark-matter-20200923/">might compose dark matter</a>. These are both hypothetical entities thought to exist that have never been observed.</p>
<p>The vast majority of signals at high frequency would immediately point to particles or phenomena that cannot be described within the <a href="https://theconversation.com/the-standard-model-of-particle-physics-the-absolutely-amazing-theory-of-almost-everything-94700">Standard Model of particle physics</a> and the <a href="https://www.universetoday.com/84730/astronomy-without-a-telescope-assumptions/">Standard Model of cosmology</a>, our best descriptions of nature. So a discovery would shed light on some of the unsolved problems of our universe, such as the composition of dark matter and the origin of inflation.</p>
<h2>Tiny machinery</h2>
<p>There are a couple of clear advantages of high-frequency detectors. First, as the size of the detector is proportional to the wavelength to be probed, high-frequency gravitational wave detectors would be much smaller (and cheaper) than low-frequency ones. The length of the Ligo arms, for instance, is four kilometres. We dream of listening to the sound of the big bang with a detector that would fit in our kitchen. We are hopeful this could work – at high frequency there are no astrophysical background signals interfering with what we want to measure.</p>
<figure class="align-center ">
<img alt="Aerial view of LIGO facility in Hanford, Washington." src="https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=602&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=602&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=602&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=756&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=756&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411446/original/file-20210715-15-1o64zv8.jpg?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">Aerial view of LIGO facility in Hanford, Washington.</span>
<span class="attribution"><a class="source" href="https://www.ligo.caltech.edu/WA/image/ligo20150731a">Caltech/wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Detecting high-frequency gravitational waves is hard though. An experiment like Ligo looks for the variation of the distance between two mirrors, caused by the passing gravitational wave, equivalent to a fraction of the size of the nucleus of an atom. As high-frequency gravitational waves detectors are smaller, the variation to be detected would be even tinier. </p>
<p>With our currently available technology, we are already able to detect minute variations in the high-frequency range (though we haven’t caught any gravitational waves yet). But we need to improve it a bit more to detect gravitational waves from the early universe. Supporting this technological development is what <a href="http://www.ctc.cam.ac.uk/activities/UHF-GW.php">our project</a> is all about.</p>
<p>Ultimately, we are trying to start a challenging journey, much as people did back in the 1970s when they began searching for astrophysical gravitational waves. It took almost 50 years and more than 20 attempts, which ultimately shows that hard work and patience pay off.</p><img src="https://counter.theconversation.com/content/164502/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Francesco Muia is funded by a UKRI/EPSRC Stephen Hawking fellowship and partially supported by an STFC consolidated grant.</span></em></p>How scientists are planning to listen to the sound of the big bang with a gravitational wave detector that would fit in a kitchen.Francesco Muia, Postdoctoral Researcher, Theoretical Physics and Cosmology, Stephen Hawking Fellow, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1551252021-02-15T18:51:20Z2021-02-15T18:51:20ZA tiny crystal device could boost gravitational wave detectors to reveal the birth cries of black holes<figure><img src="https://images.theconversation.com/files/384196/original/file-20210215-15-u84vo1.jpg?ixlib=rb-1.1.0&rect=8%2C13%2C2986%2C2645&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NSF / LIGO / Sonoma State University / A Simonnet</span>, <span class="license">Author provided</span></span></figcaption></figure><p>In 2017, astronomers witnessed the birth of a black hole for the first time. Gravitational wave detectors picked up the ripples in spacetime caused by <a href="https://en.wikipedia.org/wiki/GW170817">two neutron stars colliding</a> to form the black hole, and other telescopes then observed the resulting explosion.</p>
<p>But the real nitty-gritty of how the black hole formed, the movements of matter in the instants before it was sealed away inside the black hole’s event horizon, went unobserved. That’s because the gravitational waves thrown off in these final moments had such a high frequency that our current detectors can’t pick them up.</p>
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<strong>
Read more:
<a href="https://theconversation.com/at-last-weve-found-gravitational-waves-from-a-collapsing-pair-of-neutron-stars-85528">At last, we've found gravitational waves from a collapsing pair of neutron stars</a>
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<p>If you could observe ordinary matter as it turns into a black hole, you would be seeing something similar to the Big Bang played backwards. The scientists who design gravitational wave detectors have been hard at work to figure out how improve our detectors to make it possible.</p>
<p>Today our team is publishing <a href="https://www.nature.com/articles/s42005-021-00526-2">a paper</a> that shows how this can be done. Our proposal could make detectors 40 times more sensitive to the high frequencies we need, allowing astronomers to listen to matter as it forms a black hole.</p>
<p>It involves creating weird new packets of energy (or “quanta”) that are a mix of two types of quantum vibrations. Devices based on this technology could be added to existing gravitational wave detectors to gain the extra sensitivity needed.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=464&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=464&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383921/original/file-20210211-17-q8esrc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=464&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An artist’s conception of photons interacting with a millimetre scale phononic crystal device placed in the output stage of a gravitational wave detector.</span>
<span class="attribution"><span class="source">Carl Knox / OzGrav / Swinburne University</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Quantum problems</h2>
<p>Gravitational wave detectors such as the <a href="https://en.wikipedia.org/wiki/LIGO">Laser Interferometer Gravitational-wave Observatory (LIGO)</a> in the United States use lasers to measure incredibly small changes in the distance between two mirrors. Because they measure changes 1,000 times smaller than the size of a single proton, the effects of quantum mechanics – the physics of individual particles or quanta of energy – play an important role in the way these detectors work.</p>
<p>Two different kinds of quantum packets of energy are involved, both predicted by Albert Einstein. In 1905 he predicted that light comes in packets of energy that we call <em>photons</em>; two years later, he predicted that heat and sound energy come in packets of energy called <em>phonons</em>. </p>
<p>Photons are used widely in modern technology, but phonons are much trickier to harness. Individual phonons are usually swamped by vast numbers of random phonons that are the heat of their surroundings. In gravitational wave detectors, phonons bounce around inside the detector’s mirrors, degrading their sensitivity.</p>
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<strong>
Read more:
<a href="https://theconversation.com/australias-part-in-the-global-effort-to-discover-gravitational-waves-54525">Australia's part in the global effort to discover gravitational waves</a>
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<p>Five years ago physicists realised you could <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.211104">solve the problem</a> of insufficient sensitivity at high frequency with devices that <em>combine</em> phonons with photons. They showed that devices in which energy is carried in quantum packets that share the properties of both phonons and photons can have quite remarkable properties. </p>
<p>These devices would involve a radical change to a familiar concept called “resonant amplification”. Resonant amplification is what you do when you push a playground swing: if you push at the right time, all your small pushes create big swinging.</p>
<p>The new device, called a “white light cavity”, would amplify all frequencies equally. This is like a swing that you could push any old time and still end up with big results.</p>
<p>However, nobody has yet worked out how to make one of these devices, because the phonons inside it would be overwhelmed by random vibrations caused by heat.</p>
<h2>Quantum solutions</h2>
<p>In <a href="https://www.nature.com/articles/s42005-021-00526-2">our paper</a>, published in Communications Physics, we show how two different projects currently under way could do the job.</p>
<p>The Niels Bohr Institute in Copenhagen has been <a href="https://www.nature.com/articles/nnano.2017.101">developing devices</a> called phononic crystals, in which thermal vibrations are controlled by a crystal-like structure cut into a thin membrane. The Australian Centre of Excellence for Engineered Quantum Systems has also demonstrated <a href="https://www.nature.com/articles/srep02132">an alternative system</a> in which phonons are trapped inside an ultrapure quartz lens.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383913/original/file-20210211-16-1girq3t.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of a tiny device that could boost gravitational wave detector sensitivity in high frequencies.</span>
<span class="attribution"><span class="source">Carl Knox / OzGrav / Swinburne University</span>, <span class="license">Author provided</span></span>
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</figure>
<p>We show both of these systems satisfy the requirements for creating the “negative dispersion” – which spreads light frequencies in a reverse rainbow pattern – needed for white light cavities. </p>
<p>Both systems, when added to the back end of existing gravitational wave detectors, would improve the sensitivity at frequencies of a few kilohertz by the 40 times or more needed for listening to the birth of a black hole.</p>
<h2>What’s next?</h2>
<p>Our research does not represent an instant solution to improving gravitational wave detectors. There are enormous experimental challenges in making such devices into practical tools. But it does offer a route to the 40-fold improvement of gravitational wave detectors needed for observing black hole births.</p>
<p>Astrophysicists have predicted <a href="https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.043005">complex gravitational waveforms</a> created by the convulsions of neutron stars as they form black holes. These gravitational waves could allow us to listen in to the nuclear physics of a collapsing neutron star. </p>
<p>For example, it has been shown that they can clearly reveal whether the neutrons in the star remain as neutrons or whether they <a href="https://en.wikipedia.org/wiki/Quark_star">break up into a sea of quarks</a>, the tiniest subatomic particles of all. If we could observe neutrons turning into quarks and then disappearing into the black hole singularity, it would be the exact reverse of the Big Bang where out of the singularity, the particles emerged which went on to create our universe.</p><img src="https://counter.theconversation.com/content/155125/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Blair receives funding from the Australian Research Council. </span></em></p>A small add-on to existing gravitational wave detectors could reveal what happens to matter as it becomes a black hole, a process like the big bang in reverse.David Blair, Emeritus Professor, ARC Centre of Excellence for Gravitational Wave Discovery, OzGrav, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1284302020-04-30T12:12:37Z2020-04-30T12:12:37ZHow could an explosive Big Bang be the birth of our universe?<figure><img src="https://images.theconversation.com/files/317199/original/file-20200225-24680-ba246u.jpg?ixlib=rb-1.1.0&rect=220%2C494%2C2555%2C1607&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">No one knows what kicked off the Big Bang that eventually allowed the stars to begin forming.</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details-0203045">Adolf Schaller for STScI</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</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>
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<blockquote>
<p><strong>How can a Big Bang have been the start of the universe, since intense explosions destroy everything? – Tristan S., age 8, Newark, Delaware</strong></p>
</blockquote>
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<p>Pretend you’re a perfectly flat chess piece in a game of chess on a perfectly flat and humongous chessboard. One day you look around and ask: How did I get here? How did the chessboard get here? How did it all start? You pull out your telescope and begin to explore your universe, the chessboard….</p>
<p>What do you find? Your universe, the chessboard, is getting bigger. And over more time, even bigger! The board is expanding in all directions that you can see. There’s nothing that seems to be causing this expansion as far as you can tell – it just seems to be the nature of the chessboard.</p>
<p>But wait a minute. If it’s getting bigger, and has been getting bigger and bigger, then that means in the past, it must have been smaller and smaller and smaller. At some time, long, long ago, at the very beginning, it must have been so small that it was infinitely small.</p>
<p>Let’s work forward from what happened then. At the beginning of your universe, the chessboard was infinitely tiny and then expanded, growing bigger and bigger until the day that you decided to make some observations about the nature of your chess universe. All the stuff in the universe – the little particles that make up you and everything else – started very close together and then spread farther apart as time went on. </p>
<p>Our universe works exactly the same way. When astronomers like <a href="https://people.rit.edu/mtlsps/">me</a> make observations of distant galaxies, we see that they are <a href="https://starchild.gsfc.nasa.gov/docs/StarChild/questions/redshift.html">all moving apart</a>. It seems our universe started very small and has been expanding ever since. In fact, scientists now know that not only is the universe expanding, but the speed at which it’s expanding is <a href="https://theconversation.com/curious-kids-will-the-universe-expand-forever-or-contract-in-a-big-crunch-96209">increasing</a>. This mysterious effect is caused by something physicists call dark energy, though we know very little else about it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330861/original/file-20200427-145530-jbrvx5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A visualization of tiny energy fluctuations in the early universe.</span>
<span class="attribution"><a class="source" href="https://sci.esa.int/web/planck/-/51553-cosmic-microwave-background-seen-by-planck">ESA, Planck Collaboration</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Astronomers also observe something called the <a href="https://wmap.gsfc.nasa.gov/universe/bb_tests_cmb.html">Cosmic Microwave Background Radiation</a>. It’s a very low level of energy that exists all throughout space. We know from <a href="https://lambda.gsfc.nasa.gov/education/graphic_history/observations.cfm">those measurements</a> that our universe is <a href="https://lambda.gsfc.nasa.gov/education/graphic_history/age.cfm">13.8 billion years old</a> – way, way older than people, and about three times older <a href="https://www.scientificamerican.com/article/how-science-figured-out-the-age-of-the-earth/">than the Earth</a>. </p>
<p>If astronomers look back all the way to the event that started our universe, we call that <a href="https://spaceplace.nasa.gov/big-bang/en/">the Big Bang</a>.</p>
<p>Many people hear the name “Big Bang” and think about a giant explosion of stuff, like a bomb going off. But the Big Bang wasn’t an explosion that destroyed things. It was the beginning of our universe, the start of both space and time. Rather than an explosion, it was a very rapid expansion, the event that started the universe growing bigger and bigger.</p>
<p>This expansion is different than an explosion, which can be caused by things like chemical reactions or large impacts. Explosions result in energy going from one place to another, and usually a lot of it. Instead, during the Big Bang, energy moved along with space as it expanded, moving around wildly but becoming more spread out over time since space was growing over time.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/LeUcjqqhNxM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Try to think of the Big Bang as a massive expansion, rather than a destructive explosion.</span></figcaption>
</figure>
<p>Back in the chessboard universe, the “Big Bang” would be like the beginning of everything. It’s the start of the board getting bigger.</p>
<p>It’s important to realize that “before” the Big Bang, there was no space and there was no time. Coming back to the chessboard analogy, you can count the amount of time on the game clock after the start but there is no game time before the start – the clock wasn’t running. And, before the game had started, the chessboard universe hadn’t existed and there was no chessboard space either. You have to be careful when you say “before” in this context because time didn’t even exist until the Big Bang.</p>
<p>You also have wrap your mind around the idea that the universe isn’t expanding “into” anything, since as far as we know the Big Bang was the <a href="https://theconversation.com/curious-kids-what-existed-before-the-big-bang-did-something-have-to-be-there-to-go-boom-103742">start of both space and time</a>. Confusing, I know!</p>
<p>Astronomers aren’t sure what caused the Big Bang. We just look at observations and see that’s how the universe did start. We know it was extremely small and got bigger, and we know that kicked off 13.8 billion years ago.</p>
<p>What started our own game of chess? That’s one of the deepest questions anyone can ask.</p>
<hr>
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<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>The term ‘Big Bang’ might make you think of a massive explosion. Put the thought out of your head. Rather than an explosion, it was the start of everything in the universe.Michael Lam, Assistant Professor of Physics and Astronomy, Rochester Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1249302019-10-08T21:49:46Z2019-10-08T21:49:46ZNobel Prize in Physics for two breakthroughs: Evidence for the Big Bang and a way to find exoplanets<figure><img src="https://images.theconversation.com/files/296084/original/file-20191008-128652-16ovxuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's rendering of a Jupiter-sized exoplanet and its host, a star slightly more massive than our sun. Image credit:</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/news/news.php?feature=4674">ESO/NASA</a></span></figcaption></figure><p>Did the universe really begin with a Big Bang? And if so, is there evidence? Are there planets around other stars? Can they support life? </p>
<p>The 2019 Nobel Prize in Physics goes to three scientists who have provided deep insights into all of these questions. </p>
<p>James Peebles, <a href="https://phy.princeton.edu/people/p-james-peebles">an emeritus professor of physics</a> at Princeton University, won half the prize for a body of work he completed since the 1960s, when he and a team of physicists at Princeton attempted to detect the remnant radiation of the dense, hot ball of gas at the beginning of the universe: the Bang Bang. </p>
<p>The other half went to Michel Mayor, <a href="http://www.planetary.org/connect/our-experts/profiles/michel-mayor.html">an emeritus professor of physics from the University of Geneva</a>, together with Didier Queloz, <a href="http://obswww.unige.ch/%7Equeloz/Welcome.html">also a Swiss astrophysicist at the University of Geneva</a> and <a href="https://www.astro.phy.cam.ac.uk/directory/prof-didier-queloz">the University of Cambridge</a>. Both made breakthroughs with the discovery of the first planets orbiting other stars, also known as exoplanets, beyond our solar system.</p>
<p>I am an <a href="http://www.novastella.org">astrophysicist</a> and was delighted to hear of this year’s Nobel recipients, who had a profound impact on scientists’ understanding of the universe. A lot of my own work on exploding stars is guided by theories describing the structure of the universe that James Peebles himself laid down. </p>
<p>In fact, one might say that Peebles, of all this year’s Nobel winners, is the biggest star of the real “Big Bang Theory.” </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296088/original/file-20191008-128681-quk6go.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nobel Prize winners in physics, from left, James Peebles in Princeton, N.J., Didier Queloz in London and Michel Mayor in Madrid.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Nobel-Physics/38f8572988cd40fdba43aab73b2a714b/29/0">AP Photo/Frank Augstein</a></span>
</figcaption>
</figure>
<h2>The real Big Bang Theory</h2>
<p>As Peebles and his Princeton team rushed to complete their discovery in 1964, they were scooped by two young scientists at nearby Bell Labs, <a href="https://www.nobelprize.org/prizes/physics/1978/penzias/biographical/">Arno Penzias</a> and <a href="https://www.nobelprize.org/prizes/physics/1978/wilson/biographical/">Robert Wilson</a>. The remaining radiation from the Big Bang was predicted to be microwave energy, in much the same form used by countertop ovens.</p>
<p>It was a serendipitous finding because Penzias and Wilson had constructed an antenna to detect this microwave radiation which was used in satellite communications. But they were mystified by a persistent source of noise in their measurements, like the fuzz of a radio tuned between stations. </p>
<p>Penzias and Wilson talked to Peebles and his colleagues and learned that this static they were hearing was the radiation left over from the Big Bang itself. Penzias and Wilson <a href="https://www.nobelprize.org/prizes/physics/1978/summary/">won the Nobel Prize in 1978</a> for their discovery, though Peebles and his team <a href="https://doi.org/10.1086/148306">provided the crucial interpretation</a>. </p>
<p>Peebles has also made decades of pivotal contributions to the study of the matter which pervades the cosmos but is invisible to telescopes, known as <a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy">dark matter</a>, and the equally mysterious energy of empty space, known as dark energy. He has done foundational work on the formation of galaxies, as well as to how the Big Bang gave rise to the first elements – hydrogen, helium, lithium – on the <a href="https://pubchem.ncbi.nlm.nih.gov/periodic-table/">periodic table</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=434&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=434&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296085/original/file-20191008-128648-1ijlkkj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=434&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">First discovery of an exoplanet just earned the Nobel Prize for Physics.</span>
<span class="attribution"><a class="source" href="https://exoplanets.nasa.gov/resources/289/infographic-profile-of-planet-51-pegasi-b/">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>Finding planets beyond our solar system</h2>
<p>For their Nobel Prize-winning work, Mayor and Queloz carried out a survey of nearby stars using a <a href="http://www.obs-hp.fr/www/guide/elodie/elodie-eng.html">custom-built instrument</a>. Using this instrument, they could detect the wobble of a star – a sign that it is being tugged by the gravity of an orbiting exoplanet. </p>
<p>In 1995, in a landmark discovery <a href="https://doi.org/10.1038/378355a0">published in the journal Nature</a>, they found a star in the constellation Pegasus rapidly wobbling across the sky, in response to an unseen planet with half the mass of Jupiter. This exoplanet, dubbed <a href="https://exoplanets.nasa.gov/resources/289/infographic-profile-of-planet-51-pegasi-b/">51 Pegasi b</a>, orbits close to its central star, well within the orbit of Mercury in our own solar system, and completes one full orbit in just four days. </p>
<p>This surprising discovery of a “hot Jupiter,” quite unlike any planet in our own solar system, excited the astrophysical community and inspired many other research groups, including the <a href="https://exoplanets.nasa.gov/keplerscience/">Kepler space telescope team</a>, to search for exoplanets. </p>
<p>These groups are using both the same wobble detection method as well as new methods, such as looking for light dips caused by exoplanets passing over nearby stars. Thanks to these research efforts, more than 4,000 exoplanets have now been discovered.</p>
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<p class="fine-print"><em><span>Robert T Fisher receives funding from NASA. </span></em></p>Scientists who discovered planets in far off stellar systems and the fundamentals of the Big Bang Theory have earned the 2019 Nobel Prize in Physics.Robert T. Fisher, Associate Professor of Physics, UMass DartmouthLicensed as Creative Commons – attribution, no derivatives.