In the beginning, the Big Bang happened, sending everything in the universe expanding outward and apart, from a dense hot point. Since then, all that matter and energy has continued to move outward, carried along with the cosmos\u2019 expansion.<\/p>\n
That expansion is fueled by dark energy, a mysterious force that is fundamental to scientists\u2019 understanding of the past and future of the universe. Since dark energy’s discovery a quarter-century ago, scientists have assumed its influence to be constant, its force exerted the same way 5 billion years ago, today, and forever; a sort of steady foot on the gas pedal.<\/p>\n
But new results<\/a>, from an instrument called the Dark Energy Spectroscopic Instrument, or DESI, located at the Kitt Peak National Observatory in Arizona, suggest that might not be true: Dark energy may, in fact, evolve\u2014its influence changing over time. Data now suggest dark energy has weakened in more recent epochs, essentially lessening its pressure on the accelerator. The results potentially \u201creally change your understanding of what dark energy actually is,\u201d said Ashley Ross, a cosmologist at The Ohio State University who is working on a project to measure how galaxies are distributed, as part of the DESI collaboration.<\/p>\n If DESI\u2019s recent finding holds up, it means scientists\u2019 current conception of the universe\u2019s past, present, and future is mistaken. And news stories about the findings were quick to point that out: \u201cWe might have gotten dark energy totally wrong,\u201d proclaimed<\/a> Live Science. \u201cThis could change everything,\u201d wrote<\/a> Futurism.<\/p>\n Headlines like those may be true, but the verdict isn\u2019t yet in. Some scientists take the possible error as exciting, since it could provide a path to better understanding the most fundamental physics, for which details have so far been elusive; others doubt the finding will stand time\u2019s test.<\/p>\n To understand the universe, scientists use telescopes to observe as much of it as they can, gathering and characterizing patterns\u2014how galaxies tend to form, for instance, or how stars tend to die. They use those observations to create, and bolster or refute, theories: the underlying, usually mathematical models that explain why they see what they see through their telescopes.<\/p>\n But any human-made model is likely to be incomplete, oversimplified. And data that potentially conflicts with existing ideas, as DESI\u2019s data might, raises questions about the costs and benefits of being wrong<\/a>, like spending hundreds of millions of dollars of federal research money on instruments and human capital, as dark-energy studies have, that ultimately upend a particular idea about the universe.<\/p>\n Getting closer to cosmic truth, though, experts point out, often requires fumbling through uncertainties and smashing into dead ends. That mental maze, which is typical in this area of research, experts say, is something that sensationalized news coverage often fails to acknowledge.<\/p>\n And making that incremental progress and taking advantage of its fruits, like potential practical applications of fundamental science<\/a>, asks scientists to be willing to change their minds about even their closest-held foundational theories in favor of creative new lines of inquiry. But that line can be subjective, said Melissa Jacquart, a philosopher of science at the University of Cincinnati: \u201cWhen do we have enough evidence to make us shift our perspective or think that we need to be approaching it differently?\u201d<\/p>\n Dark energy seems distant from daily life on Earth, but its presence has made the universe what it is today, maybe even enabling that life to arise. And though it\u2019s not apparent on this planet, dark energy causes the universe to grow larger,\u00a0and faster, with each passing picosecond.<\/p>\n For a long time, scientists thought the expansion rate was slowing with time, like a coasting car. But in 1998 astronomers discovered that the opposite was true: Cosmic expansion was actually speeding up. The universe seemed to be pressing the gas pedal pretty hard.<\/p>\n Something had to be providing that fuel, counteracting the gravity that naturally draws things together. Scientists didn\u2019t know what that something was, so they called it dark energy. Decades later, they still can’t explain it: Dark energy is \u201cdark\u201d because it remains a mystery.<\/p>\n Dark energy is ubiquitous, though. It\u2019s estimated to make up about 70 percent of the universe, and together with dark matter\u2014another scientific shoulder-shrug\u2014the two account for a staggering 95 percent of the universe. \u201cWe don’t know what most of the universe actually is,\u201d said Ross.<\/p>\n Still, despite that lack of knowledge, scientists assumed dark energy forced a constant acceleration since it fit with the data they had gathered thus far on the universe\u2019s history and evolution.<\/p>\n \u201cWhen do we have enough evidence to make us shift our perspective or think that we need to be approaching it differently?\u201d<\/p>\n Cosmologists are not naive: They knew that assumption could be incorrect. And, in fact, analyzing it\u2014along with other hypotheses\u2014was one of DESI\u2019s goals.<\/p>\n The instrument, which started its main work in 2021, kicked toward that goalpost by peering at various galaxies across the universe. By analyzing the light emitted from those galaxies, DESI scientists were able to measure their distance from Earth and how fast they were moving outward and made a three-dimensional map of the cosmos to understand how its expansion has changed.<\/p>\n DESI\u2019s data, when combined with other observations, suggested that the universe\u2019s expansion rate has actually shifted over time\u2014and if dark energy dictates that rate, the energy itself must be changing.<\/p>\n If that\u2019s the case, it could alter scientists\u2019 prediction of the universe\u2019s fate: With constant dark energy, the cosmos is doomed to expand faster and faster forever, pushing everything so far apart that other galaxies will recede beyond the view of even the most powerful telescopes; our cosmic neighborhood will appear to be alone. If dark energy can change<\/a> over time, though, that dark ending may be avoided.<\/p>\n<\/p>\n By analyzing the light emitted from various galaxies, DESI scientists were able to measure their distance from Earth and how fast they were moving outward and made a three-dimensional map of the cosmos to understand how its expansion has changed. In this video, fly through millions of galaxies mapped using coordinate data from DESI. Credit: DESI collaboration and Fiske Planetarium\/CU Boulder<\/p>\n Even though this evolving possibility was DESI scientists\u2019 idea, it\u2019s nevertheless a big departure from scientists\u2019 current cosmological model of the universe, appropriately called the \u201cstandard model.\u201d That model postulates, in mathematical equations, that after the Big Bang, the universe experienced a period of rapid inflation. Since then, it has continued to expand, in a way dictated by the balance of its contents: regular atomic material and dark matter, both influenced by gravity, and dark energy\u2014the latter assumed to exert a constant acceleratory force in opposition to gravity.<\/p>\n But cosmologists have actually been searching for holes in the standard model\u2014holes that might lead to a more complete understanding of spacetime, because the standard model has limitations. Dark energy and dark matter, for instance, have never been directly detected\u2014only their effects. Scientists have also seen discrepancies in the measurement of the universe\u2019s expansion rate based on different methods of measurement. And the light left over from the Big Bang shows wonky anomalies that don\u2019t necessarily line up with the standard model\u2019s predictions.<\/p>\n \u201cWe don’t know what most of the universe actually is.”<\/p>\n To James Overduin, a theoretical physicist at Towson University who co-wrote a book about dark energy called The Weight of the Vacuum, the concept of dark energy itself is an opaque placeholder\u2014something hand-wave-y that explains a physical behavior that astronomers observe. That kind of a cover is something scientists have created for centuries, when they wanted to hang onto their current conception of the universe in the face of evidentiary challenges.<\/p>\n In some sense, making models of the universe always involves those kinds of simplifications\u2014something scientists don\u2019t always like to admit. In physics, we often think of the universe as a set of facts waiting to be discovered, said Jacquart. \u201cBut we can’t really just know those facts of the matter,\u201d she said. \u201cAnd so, in terms of how to explain everything, there are all of these spaces along the way where the scientists have to make either assumptions or idealizations.\u201d<\/p>\n Data and analysis that poke holes in those smooth models can push science in new directions, acting as their own kind of dark energy. The question, always, is how big those holes must be before a theory\u2014like the standard model, or dark energy\u2019s constancy\u2014rips.<\/p>\n Whether the DESI results rise to that level remains a debate among scientists. Zachary Slepian, an astrophysicist at the University of Florida and a member of the DESI team, doesn\u2019t think the new data represent enough evidence to abandon current cosmological conceptions. What appears to be creepily evolving dark energy could, in fact, be some kind of experimental error, or an instrumental quirk. At the lower end of calculations, scientists estimate that the odds the DESI results are due to random chance are about one in 385\u2014close to a statistical significance known as three-sigma. Five sigma is the field\u2019s standard for a real discovery\u2014something that has a one in 3.5 million chance of being a random fluke.<\/p>\n Colin Hill, a Columbia University cosmologist who works with the Atacama Cosmology Telescope in Chile<\/a>, also isn\u2019t convinced. \u201cThere’s sort of a borderline hint that maybe there’s something going on,\u201d said Hill. But the statistical significance could vanish with more data, and extensions of the standard model\u2014rather than a whole new model\u2014could also explain the galactic findings.<\/p>\n Besides, he said, if dark energy really is evolving, it could imply a scenario where, as the universe expands, more dark energy is created. \u201cThat’d be truly, truly wild,\u201d he said.<\/p>\n That data from DESI and other experiments doesn\u2019t necessarily indicate dark energy is evolving, he added; the DESI measurement could be attributed to other phenomena. \u201cIt’s a little bit of a messy situation.\u201d<\/p>\n Ross, though, sees the discovery as more solid: The statistical significance has increased as more DESI data has come in, for instance. \u201cThat’s what makes me excited and feel that it could all be pretty real,\u201d he said, adding that data from other instruments also increased the analysis\u2019 rigor.<\/p>\n Ross, along with other physicists, would actually be excited if the current model of dark energy were proven wrong, because it could help his crew think differently about the best direction for cosmology. Overduin agrees: Cosmologists haven\u2019t made much headway in using theories to explain the universe\u2019s nuances and contradictions, said Overduin. And the buzz about the DESI results, despite their preliminary nature, illuminate scientists\u2019 hope that discrepancies like this could be wormholes to new ideas, and so progress. \u201cThere’s a bit of desperation there,\u201d said Overduin.<\/p>\n Learning that dark energy may be fundamentally different\u2014and so, too, may the universe\u2014than scientists thought could be an important step toward the truth. Because, presumably, if scientists are on track for the truth, progress will come more easily. \u201cIf you look at the history of science it’s entirely filled with us throwing out theories,\u201d said Jacquart\u2014or, more accurately, using mounting evidence to keep what seems right, toss what seems wrong, and getting closer to \u201cthe actual reality of the world,\u201d she said.<\/p>\n Jacquart likens this stepwise process to a choose-your-own-adventure book. If one choice is a dead end, \u201clet’s go back a few steps and figure out where in our journey we could have gone on a different path.\u201d<\/p>\n Cosmologists have been searching for holes in the standard model\u2014holes that might lead to a more complete understanding of spacetime, because the standard model has limitations.<\/p>\n But in science, taking those steps back can be difficult. \u201cEspecially when you have theories that astronomers hold so dear,\u201d Jacquart said. Dearly held theories are often ones whose tenets line up with a preferred modus operandi for the physical world, revealing a human bias in the search for scientific truth\u2014not something that\u2019s unique to cosmology, since human bias can pervade any scientific field.<\/p>\n Dark energy\u2019s constant form may fall into the natural-bias category. \u201cSo many spaces of physics focus on consistency,\u201d Jacquart said. \u201cThe physics always works the same way. And, in some ways, that shows sort of a preference towards simplicity.\u201d<\/p>\n The DESI results are hinting that the universe isn\u2019t so simple, or consistent. It \u201cadds complexity that I don’t think we always want to lean towards,\u201d she said.<\/p>\n Leaning where evidence points, though, is important\u2014even though how dark energy behaves can seem lightyears away from everyday life on Earth. For one, pursuing dead-end theories spends research time, and tax dollars, that some argue would be better spent on ideas that open new doors to understanding.<\/p>\n More than 900 scientists are part of the DESI collaboration; getting that large dark-energy cohort mobilized around the most fruitful ideas, as DESI\u2019s results may, could prevent them from simply spinning their wheels. And being wrong, or holding onto ideas longer than data suggests is prudent, could lead to building expensive instruments that may not add much new knowledge to the world, if they are not engineered to pursue what the universe actually has on offer.<\/p>\n In particle physics, for instance, the Large Hadron Collider cost nearly $5 billion to build, not to mention operational costs. While it discovered a particle that validated scientists\u2019 existing understanding, it didn\u2019t find any of the new physics some were hoping for. Now proposals are on the table for a new machine that would cost tens of billions of dollars but doesn\u2019t have a clear road sign in the right direction from the previous experiment.<\/p>\n To Ross, that\u2019s part of why the new results are important for dark energy research: They might change how future experiments are designed. That would save science from wasting money and scientists\u2019 time on an outdated idea.<\/p>\n On a more long-term and abstract note, if scientists get closer to characterizing dark energy and its place in cosmic evolution, as the largest ingredient in the universe, that could someday benefit humans. Einstein, after all, probably didn\u2019t envision GPS satellites when he came up with general relativity, but those satellites nonetheless rely on his discovery.<\/p>\n \u201cI see science as something where you can never really be right. You can just be asymptotically less wrong.\u201d<\/p>\n If DESI does ultimately show astronomers, to their consensus satisfaction, that their existing models of the universe and its dark places are wrong, Jacquart doesn\u2019t think time spent on current ideas was a waste. Slepian, from his perch at the University of Florida, sees the DESI collaboration, which includes hundreds of scientists, as a physics incubator\u2014kind of like the Manhattan Project, he said. The project built the atomic bomb and altered the world forever, but it also united some of the 20th century\u2019s greatest scientific minds: \u201cThat seeded American particle theory and particle physics dominance for the next 50 years.\u201d<\/p>\n Perhaps DESI could do the same for cosmology.<\/p>\n Maybe someday those scientists and their instruments will tell us what dark energy actually is, said Ross: \u201cThe whole point to me is to not have to call it dark energy.\u201d<\/p>\n But, even if that\u2019s the case, Slepian doesn\u2019t think physicists will ever fully understand the fundamental truths of the universe. \u201cI see science as something where you can never really be right,\u201d he said. \u201cYou can just be asymptotically less wrong.\u201d<\/p>\n This article was originally published on Undark<\/a>. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"In the beginning, the Big Bang happened, sending everything in the universe expanding outward and apart, from a…\n","protected":false},"author":3,"featured_media":51721,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[492,159,67,132,68],"class_list":{"0":"post-51720","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-physics","9":"tag-science","10":"tag-united-states","11":"tag-unitedstates","12":"tag-us"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/114823987464510997","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/51720","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=51720"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/51720\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/51721"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=51720"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=51720"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=51720"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}