Latest news with #LCDM
Yahoo
07-05-2025
- Science
- Yahoo
Scientists Say That Something Very Weird Is Going on With the Universe
Yahoo is using AI to generate takeaways from this article. This means the info may not always match what's in the article. Reporting mistakes helps us improve the experience. Yahoo is using AI to generate takeaways from this article. This means the info may not always match what's in the article. Reporting mistakes helps us improve the experience. Yahoo is using AI to generate takeaways from this article. This means the info may not always match what's in the article. Reporting mistakes helps us improve the experience. Generate Key Takeaways Astronomers have made an intriguing discovery that could upend everything we know about the structure of the universe and its expansion. Scientists recently found that dark energy, the mysterious form driving the accelerating expansion of the universe, could be weakening over time. The findings could undermine the existing standard cosmological model of the universe called the lambda-cold dark matter (LCDM) model, which takes dark energy, ordinary matter, and cold dark matter — a hypothetical form of dark matter that moves slowly compared to the speed of light — into consideration. The symbol lambda in the model refers to Albert Einstein's cosmological constant, which assumes that the universe is accelerating at a fixed rate. Yet, last year, scientists concluded that dark energy isn't a constant after all, analyzing observations by the Dark Energy Spectroscopic Instrument (DESI) in Arizona, as New Scientist reports. They found that the mysterious force could be evolving and weakening over time. In March, scientists released a follow-up, strengthening the unusual findings. "This is exciting – it might actually be putting the standard model of cosmology in danger," Autonomous University of Madrid assistant research professor Yashar Akrami told New Scientist. Instead of making changes to the LCDM itself, Akrami and his colleagues suggested redefining dark energy as a "quintessence field," which has been used to explain observations of an accelerating rate of expansion of the universe. That could allow scientists to harmonize more advanced string theory with the standard cosmological model. "If you prove that quintessence is dark energy, it's very good for [string theorists]," Akrami told New Scientist. "That's why the string theory community is really excited now." An altered take on the quintessence model of dark energy suggests the mysterious force could be interacting with gravity itself. "We've always grown up thinking about the universe as having the gravitational force, and gravity fuels everything," University of Oxford astrophysicist Pedro Ferreira told the publication. "But now there's going to be an additional fifth force, which is due to the dark energy, which also fuels everything." But before we can add this fifth force, we'd have to reconcile the fact that we simply haven't seen any evidence for it, at least not when we're making precise measurements of our neighborhood of the universe. "Physics ends up being even more complicated than we thought it could have been, and that kind of makes you wonder, why do you want to go down that route?" Ferreira added. The researcher believes it's most likely that scientists will debate different models of dark energy and "never resolve it." Yet, there's still a chance researchers could observe gravity being influenced by dark energy in upcoming observations by the European Space Agency's Euclid satellite and DESI. More on dark energy: Scientists Say They've Built a "Black Hole Bomb"
Yahoo
24-03-2025
- Science
- Yahoo
A Shocking Discovery Shows Dark Energy Is Weakening—and We Might Be Wrong About How the Universe Ends
"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." The Dark Energy Spectroscopic Instrument (DESI) collaboration just dropped their first official data release, covering the first 13 months of the instrument's operation. While many conclusions were drawn from this data, one stood out—dark energy may not be a cosmological constant after all. In fact, its effects on the universe may be weakening over time. If this were to prove correct upon further data collection and analysis, it would punch a massive hole in the standard model of cosmology, known as the LCDM model. Hey, big news—everything we thought we knew about the universe might be wrong. Well… not everything. But scientists may have just blown a serious hole in the standard model of cosmology—known scientifically as ΛCDM—which is the theory underpinning the entirety of astrophysics. Like, a hole big enough to potentially change the name. So… also not not everything. Here's the deal. For the last 13 months, astronomers around the world have been collaborating on the use of the Dark Energy Spectroscopic Instrument (DESI) and the analysis of the data it has collected. You may have already guessed from the name, but DESI is primarily meant to study dark energy—as part of the team puts it, 'DESI aims to place unprecedented constraints on the equation of state of dark energy, the gravitationally driven growth of large-scale structure, and the sum of the neutrino masses, as well as to explore the observational signatures of primordial inflation.' Lofty goals, indeed. This week, DESI dropped its Data Release 1, which encompasses all of the observations it's made over its first 13 months of operation. It was accompanied by a slew of papers detailing the first round of analysis done on this absolute treasure trove of data. While numerous exciting conclusions were drawn, one result stood head and shoulders above everything else: dark energy might not be a cosmological constant. That's a small statement with a big impact. See, when dark energy was discovered in 1998, our picture of the universe fundamentally changed. Instead of living in an infinite bubble that had been inflated by the Big Bang and was slowing down in its expansion over time, we suddenly knew that our universe was, in fact, accelerating outward. All that energy had to come from somewhere, and the idea of dark energy was made known to humanity. The new findings from the DESI teams don't negate that picture, but they do modify it significantly. Rather than accelerating into infinity forever, the new data seems to show that the acceleration attributed to the influence of dark energy is slowing down over time. Not only is it not a constant influence on the cosmos—it seems to be a weakening one. The team made use of two massive sets of data to draw this conclusion. The first, obviously, was Data Release 1. From this massive release, the team was able to make measurements of the large-scale fluctuations of visible matter (known as baryon acoustic oscillations, or BAO) and the behavior of the intergalactic medium (through proxy observations of what is known as the Lyman-α forest) across nearly the entire history of the universe. Because DESI can see so far into the universe, it can also see billions of years into the past. The second major data set was the yet-unreleased DESI Data Release 2, from which they were able to pull a second round of BAO measurements. They also made use of external data sets describing the behaviors of the cosmic microwave background and type Ia supernovae. Combining all of that data, analyzing what it tells us (or, more accurately, what it tells the people who have studied enough physics to understand it), and comparing it to existing theories and calculations, scientists came to the conclusion that the equations that best explain what we are seeing are ones where dark energy is expressed as a variable entity, rather than a constant. To understand how big a deal this is, refer for a second back to the scientific name for the standard model of cosmology. Breaking down ΛCDM, CDM stands for Cold Dark Matter, and Λ is the cosmological constant that represents the effects of dark energy. If this finding is confirmed, the Λ in ΛCDM would be no more, as that component would be inherently incorrect. 'It's fair to say that this result, taken at face value, appears to be the biggest hint we have about the nature of dark energy in the ~25 years since we discovered it,' Adam Riess, one of the astrophysicists who first discovered dark energy, told The New York Times. This isn't the first time the idea of variable dark matter has been proposed—not by a long shot, and not even by researchers on the DESI team, who started hinting at the possibility in their early data release a few months ago. But it's easily the best indication we've ever gotten. To try and contextualize how certain the team is about their results: scientists express certainty of discovery in units of statistical significance known as sigma (σ) in order to describe how likely it was that the thing they detected was a fluke. Experts claim that something is a true 'discovery' when its statistical significance reaches 5σ, which means there's only a 1-in-3.5 million chance that the finding was the result of random fluctuation. The statistical significance of this evolving-dark-energy detection peaked at 4.2σ, which means about a 1-in-50,000 chance of fluke. So, not a 'eureka' yet, but definitely exciting. As cosmologist Wendy Freedman told The Washington Post: 'We are still at the 'interesting' or 'stay tuned' level. Very intriguing but not yet definitive.' Especially (as the NYT points out) considering that another similarly large and impressive recent study, undertaken by a consortium using the Atacama Cosmology Telescope, seemed to confirm that the ΛCDM model is accurate—at least, in the very early universe. In part by further confirming the Hubble tension (full explanation on that idea here), the team concluded that our current model still seems good to go. 'It just blew me away that we didn't see even, like, a hint of one of these new physics extensions,' Colin Hill, a cosmologist who worked on the team, told Science News. 'It indicates that we might need to go back really to some of the foundational assumptions of our understanding of cosmology.' Critically, the Atacama study being correct does not preclude the DESI study from also being correct. It just adds more puzzles to scientists' plates. So, what does this all mean? Well, outside of increasing our understanding of the vast and varied universe in which we live, it means we might be able to paint a better picture of how the universe will end. As it stands right now, the ΛCDM model implies that everything in the universe will fly apart faster and faster as time goes on, until everything is so far apart from each other that it's all functionally destroyed. But if the Λ part of ΛCDM is more of an equation than a constant—and, especially, an equation indicating that the effects of dark energy are weakening over time—our universe may not be doomed to rip itself apart. Rather, it may collapse back into an infinitely dense point in a sort of reverse-Big Bang, as described by a hypothesis known as the Big Crunch. Or, if we're very lucky, it could completely stabilize. An infinite frozen universe, forever. All of that is still left to scientists to figure out. But luckily, that's what they want to do, anyway. 'This is actually a little bit of a shot in the arm for the field,' Will Percival, a cosmologist and spokesperson for DESI, told the NYT. 'Now we've got something to go after.' You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life?
Yahoo
20-03-2025
- Science
- Yahoo
Dark energy is even stranger than we thought, new 3D map of the universe suggests. 'What a time to be alive!' (video)
When you buy through links on our articles, Future and its syndication partners may earn a commission. New results from the Dark Energy Spectroscopic Instrument (DESI) suggest that the unknown force accelerating the expansion of the universe isn't what we believed it to be. This hints that our best theory of the universe's evolution, the standard model of cosmology, could be wrong. The newly released DESI data comes from its first three years of observations collected as the instrument, mounted on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, continues to build the largest 3D map of the universe ever created. By the time DESI completes its five-year mission next year, the instrument will have measured the light from an estimated 50 million galaxies and black hole-powered quasars, in addition to the starlight of over 10 million stars. It is the capability of DESI to capture light from 5,000 galaxies simultaneously that makes it the ideal instrument to conduct a survey large enough to investigate the properties of dark energy. This new analysis focuses on data from the first three years of DESI observations, encompassing nearly 15 million of the best-measured galaxies and quasars. "The universe never ceases to amaze and surprise us," DESI Project Scientist Arjun Dey said in a statement. "By revealing the evolving textures of the fabric of our universe as never before, DESI and the Mayall telescope are changing our very understanding of the future of our universe and nature itself." Dark energy is the placeholder name given to whatever aspect of the universe is causing the fabric of spacetime to inflate faster and faster, constantly pushing galaxies apart more rapidly. It is thought to account for around 70% of the universe's matter and energy. The mysterious "stuff" called dark matter makes up another 25%, and ordinary matter comprising stars, planets, moons, our bodies and the cat next door accounts for just 5%. Essentially, everything we understand about the universe, including all of chemistry and biology is wrapped up in that 5%! The current "best guess" at the identity of dark energy is the cosmological constant, the vacuum energy of energy space, which is baked into the pie we call the standard model of cosmology or the Lambda Cold Dark Matter (LCDM) model. However, this model is built on the presumption that dark energy, represented by the Greek letter lambda (Λ), is constant over time. Vacuum energy describes the density of particles popping in and out of existence. While "something" appearing from "nothing" sounds crazy, you can think of it as the universe having an overdraft facility. Pairs of virtual particles are allow to "borrow" some energy from the cosmos to come into existence as long as they pay it back by meeting and annihilating each other. When taken in isolation, the DESI findings don't actually challenge the picture of dark energy developed in the LCDM model. It is when the DESI data is compared with other measurements of the cosmos that problems with the cosmological constant start to manifest. DESI is hinting, and not for the first time, that dark energy isn't constant but is changing over time. Specifically, this accelerating "push" seems to be weakening. These measurements include our observations of a "fossil" light left over from an event that happened shortly after the Big Bang called the "last scattering," when the universe had expanded and cooled enough to allow electrons to bond with protons and form the first neutral atoms. The disappearance of free electrons suddenly allowed photons, the particles that make up light, to travel freely. In other words, it was as if a universal fog had lifted, and the cosmos became transparent. This first light is referred to as the "cosmic microwave background" or "CMB," and it can still be observed today. Tiny variations or "wrinkles" were "frozen into" the CMB by fluctuations in the density of matter in the early universe called baryon acoustic oscillations (BAO). As the cosmos continued to expand, so too did these wrinkles. Thus, BAO wrinkles can act as a standard measuring stick of the expansion of the universe, with their size varying at different cosmic times. This variation arises as a result of how fast the universe was expanding at those times. Thus, measuring the BAO reveals the strength of dark energy throughout the history of the cosmos, and DESI can do this more precisely than any other instrument. Changes in dark energy itself were also hinted at when DESI data was compared with observations of type Ia supernovas, cosmic explosions that occur when white dwarf stars "overfeed" on a companion star. This stolen material piles up on the surface of the stellar remnant until a thermonuclear runaway is triggered. Type Ia supernovae are so uniform in terms of their light output that astronomers can use them as "standard candles" for measuring cosmic distances. In fact, type Ia supernovas were integral to the discovery that the expansion of the universe is accelerating, the genesis of dark energy, back in 1998. These distance measurements are possible because of a phenomenon called "redshift," which occurs when the wavelength of traveling light is stretched as it crosses the expanding universe. The longer the light has traveled, the more extreme the shift toward the long wavelength "red end" of the electromagnetic spectrum. That means measuring the redshift of a very well-known and consistent source of light, a standard candle, can give distance measurements. DESI data can also be combined with observations of an effect called "gravitational lensing," the distortion of light from distant galaxies by foreground objects of great mass to show the signature of evolving dark energy. The evolution of dark energy isn't robust enough to be considered a "discovery" just yet, but different combinations of the data with other observations are pushing this concept toward what is considered the "gold standard" in physics for such a determination. In addition to unveiling these latest dark energy results on Wednesday (March 19), the DESI collaboration also announced that its Data Release 1 (DR1) is now available for anyone to explore through the National Energy Research Scientific Computing Center (NERSC). DR1 contains information regarding 18.7 million cosmic objects, including roughly 4 million stars, 13.1 million galaxies, and 1.6 million quasars. Luz Ángela García Peñaloza, a former DESI team member and a cosmologist at the Universidad ECCI in Colombia, is just one scientist who is thrilled with the new DESI results and the fact that DR1 is now available to the general astronomical community. told "I am also really excited to find out DESI has released redshift information of about 19 million galaxies and quasars. We've increased the number of identified galaxies by an order of magnitude in less than 10 years!" García Peñaloza said. "The most fascinating result of all is that different sets of observations, a combination of BAO from DESI with CMB data from Planck, and the three main sets of luminosity distances of type Ia supernovas are making a stronger case for an evolving dark energy model, disfavoring the cosmological constant. "This is getting more and more consistent with other independent cosmological tests that seem to be opening a window of opportunity for new ways to explore and study dark energy and the accelerated expansion of the universe." Related Stories: — 'Mind-blowing' dark energy instrument results show Einstein was right about gravity — again — In a way, and the dark universe grew up together — Dark energy could be getting weaker, suggesting the universe will end in a 'Big Crunch' The availability of the DR1 data means astronomers outside the DESI collaboration can now dive into this vast dataset collected between May 2021 and June 2022. "Our results are fertile ground for our theory colleagues as they look at new and existing models, and we're excited to see what they come up with," DESI director Michael Levi, a scientist at Berkeley Lab, said. "Whatever the nature of dark energy is, it will shape the future of our universe. "It's pretty remarkable that we can look up at the sky with our telescopes and try to answer one of the biggest questions that humanity has ever asked.' Meanwhile, the DESI collaboration is preparing to begin additional analyses of the new dataset to extract even more findings as DESI itself continues collecting data during its fourth year of operations. "Just amazing," García Peñaloza concluded. "What a time to be alive and to be a cosmologist!" The DESI data is discussed in a series of papers available here.
