Latest news with #AlexieLeauthaud-Harnett
Khaleej Times
20-03-2025
- Science
- Khaleej Times
Dark energy seems to be changing, rattling our view of universe
Dark energy, the mysterious force thought to be driving the ever-faster expansion of the universe, appears to be changing over time, according to new observations released on Wednesday. If dark energy is in fact weakening, it would likely mean that science's understanding of how the universe works will need to be rewritten. The new findings come from the Dark Energy Spectroscopic Instrument (DESI), which sits on a telescope at the Kitt Peak National Observatory in the US state of Arizona. "What we are seeing is deeply intriguing," said Alexie Leauthaud-Harnett, a spokesperson for the DESI collaboration which brings together 70 institutions across the world. "It is exciting to think that we may be on the cusp of a major discovery about dark energy and the fundamental nature of our universe," she said in a statement. The DESI instrument's thin optical fibres can simultaneously observe 5,000 galaxies or quasars -- blazing monsters with a black hole at their heart -- for 20 minutes. This allows scientists to calculate the age and distance of these objects, and create a map of the universe so they can detect patterns and trace its history. 'Tensions' emerging Scientists have known for a century that the universe is expanding, because massive clusters of galaxies have been observed moving away from each other. In the late 1990s, scientists shocked the field by discovering that the universe's expansion has been speeding up over time. The name dark energy was given to the phenomenon driving this acceleration, the effects of which seem to be partially offset by ordinary matter -- and an also unknown thing called dark matter. The universe is thought to be made of 70 per cent dark energy, 25 per cent dark matter — and just five percent normal matter. Science's best understanding of how the universe works, which is called the standard cosmological model, refers to dark energy as being constant -- meaning it does not change. The idea was first introduced by Albert Einstein in his theory of relativity. Arnaud de Mattia, a French physicist involved in analysing the DESI data, told AFP that the standard model is "satisfactory" but some "tensions" are emerging between observations. There are several different ways of measuring the expansion of the universe, including looking at the lingering radiation from after the Big Bang, exploding stars called supernovae and how gravity distorts the light of galaxies. When the DESI team combined their new data with other measurements, they found "signs that the impact of dark energy may be weakening over time", according to a statement. "When we combine all the cosmological data, it favours that the universe's expansion was accelerating at a slightly higher rate around seven billion years ago," de Mattia said. But for the moment there is "absolutely not certainty" about this, he added. 'Inflection point' French physicist Etienne Burtin was confident that "we should have a clearer picture within five years". This is because there is loads of new data expected from DESI, Europe's Euclid space telescope, NASA's upcoming Nancy Grace Roman space telescope and the Vera Rubin Observatory in Chile. "This new generation of surveys -- in the next few years -- will nail this," Joshua Frieman, a theoretical astrophysicist at the University of Chicago, told AFP. But for now, "we're at this interesting inflection point", added Frieman, a dark energy expert and former DESI member. Burtin said confirming the "evolving dark energy" theory would be a "revolution on the level of the discovery of accelerated expansion", which itself was the subject of a physics Nobel. "The standard cosmological model would have to be different," he added. The DESI research, which involved three years' worth of observations of 15 million galaxies and quasars, was presented at a conference of the American Physical Society in California.
Yahoo
19-03-2025
- Science
- Yahoo
Dark energy seems to be changing, rattling our view of universe
Dark energy, the mysterious force thought to be driving the ever-faster expansion of the universe, appears to be changing over time, according to new observations released Wednesday. If dark energy is in fact weakening, it would likely mean that science's understanding of how the universe works will need to be rewritten. The new findings come from the Dark Energy Spectroscopic Instrument (DESI), which sits on a telescope at the Kitt Peak National Observatory in the US state of Arizona. "What we are seeing is deeply intriguing," said Alexie Leauthaud-Harnett, a spokesperson for the DESI collaboration which brings together 70 institutions across the world. "It is exciting to think that we may be on the cusp of a major discovery about dark energy and the fundamental nature of our universe," she said in a statement. The DESI instrument's thin optical fibres can simultaneously observe 5,000 galaxies or quasars -- blazing monsters with a black hole at their heart -- for 20 minutes. This allows scientists to calculate the age and distance of these objects, and create a map of the universe so they can detect patterns and trace its history. - 'Tensions' emerging - Scientists have known for a century that the universe is expanding, because massive clusters of galaxies have been observed moving away from each other. In the late 1990s, scientists shocked the field by discovering that the universe's expansion has been speeding up over time. The name dark energy was given to the phenomenon driving this acceleration, the effects of which seem to be partially offset by ordinary matter -- and an also unknown thing called dark matter. The universe is thought to be made of 70 percent dark energy, 25 percent dark matter -- and just five percent normal matter. Science's best understanding of how the universe works, which is called the standard cosmological model, refers to dark energy as being constant -- meaning it does not change. The idea was first introduced by Albert Einstein in his theory of relativity. Arnaud de Mattia, a French physicist involved in analysing the DESI data, told AFP that the standard model is "satisfactory" but some "tensions" are emerging between observations. There are several different ways of measuring the expansion of the universe, including looking at the lingering radiation from after the Big Bang, exploding stars called supernovae and how gravity distorts the light of galaxies. When the DESI team combined their new data with other measurements, they found "signs that the impact of dark energy may be weakening over time", according to a statement. "When we combine all the cosmological data, it favours that the universe's expansion was accelerating at a slightly higher rate around seven billion years ago," de Mattia said. But for the moment there is "absolutely not certainty" about this, he added. - 'Inflection point' - French physicist Etienne Burtin was confident that "we should have a clearer picture within five years". This is because there is loads of new data expected from DESI, Europe's Euclid space telescope, NASA's upcoming Nancy Grace Roman space telescope and the Vera Rubin Observatory in Chile. "This new generation of surveys -- in the next few years -- will nail this," Joshua Frieman, a theoretical astrophysicist at the University of Chicago, told AFP. But for now, "we're at this interesting inflection point", added Frieman, a dark energy expert and former DESI member. Burtin said confirming the "evolving dark energy" theory would be a "revolution on the level of the discovery of accelerated expansion", which itself was the subject of a physics Nobel. "The standard cosmological model would have to be different," he added. The DESI research, which involved three years' worth of observations of 15 million galaxies and quasars, was presented at a conference of the American Physical Society in California. ber-dl/phz
The Guardian
19-03-2025
- Science
- The Guardian
Dark energy: mysterious cosmic force appears to be weakening, say scientists
Dark energy, the mysterious force powering the expansion of the universe, appears to be weakening, according to a survey that could 'overthrow' scientists' current understanding of the fate of the cosmos. If confirmed, the results from the dark energy spectroscopic instrument (Desi) team at the Kitt Peak National Observatory in Arizona would have profound implications for theories about the evolution of the universe, opening up the possibility that its current expansion could eventually go into reverse in a 'big crunch'. A suggestion that dark energy reached a peak billions of years ago would also herald the first substantial change in decades to the widely accepted theoretical model of the universe. Prof Alexie Leauthaud-Harnett, a co-spokesperson for Desi and a cosmologist at the University of California, Santa Cruz, said: 'What we are seeing is deeply intriguing. It is exciting to think that we may be on the cusp of a major discovery about dark energy and the fundamental nature of our universe.' Dark energy was discovered in the late 1990s when astronomers used distant supernova explosions to investigate how the rate of cosmic expansion has changed over time. The expectation was that gravity should counteract the expansion that has been underway since the big bang, but instead, the supernovae indicated that the rate of expansion was accelerating, propelled by some unknown force that scientists called dark energy. Dark energy has been assumed to be a constant, which would imply the universe will meet its end in a desolate scenario called the 'big freeze', when everything is eventually so far apart that even light cannot bridge the gap between galaxies. The latest findings, announced on Thursday at the American Physical Society's Global Physics Summit in Anaheim, California, challenge that prevailing view. Desi uses its 5,000 fibreoptic 'eyes' to map the cosmos with unprecedented precision. Its latest data release captures 15m galaxies, spanning 11bn years of history, which astronomers have used to create the most detailed three-dimensional map of the universe to date. The results suggest that dark energy reached a peak in strength when the universe was about 70% of its current age and it is now about 10% weaker. This would mean the rate of expansion is still accelerating, but that dark energy is gently lifting its foot off the pedal. Prof Carlos Frenk, a cosmologist at the University of Durham and member of the Desi collaboration, said: 'What we're finding is that, yes, there is something pushing galaxies away from each other, but it is not constant. It is declining.' The results do not meet the so-called five-sigma threshold of statistical certainty that is the gold standard in physics for claiming a discovery. But many in the collaboration have shifted in recent months from a position of scepticism to confidently backing the finding. 'I'm not on the fence,' said Frenk. 'I've looked at the data carefully. To me, this is a robust result. We're witnessing the overthrow of the old paradigm and the emergence of a new paradigm.' Prof John Peacock, a cosmologist at the University of Edinburgh and a Desi collaborator who voiced scepticism about evolving dark energy at a Royal Society meeting last year, has been similarly persuaded. 'Extreme claims require extreme evidence,' he said. 'There's almost nothing in science that I would bet my house on. But I would put £1,000 on this result.' Others continue to reserve judgment. Prof George Efstathiou of the University of Cambridge, who was not involved in the findings, said: 'My take-home from this analysis is that the … measurements do not yet provide decisive evidence for evolving dark energy. They may do as Desi accumulates more data.' If dark energy keeps decreasing to the point where it becomes negative, the universe is predicted to end in a reverse big bang scenario known as the big crunch. Scientists do not know why dark energy, which is generally estimated to account for about 70% of the universe – with the rest made up of dark and ordinary matter – might be waning or whether this would indicate the laws of physics are changing or that a crucial component is missing from them. Prof Ofer Lahav, an astronomer at University College London and Desi collaborator, said: 'It's fair to say we have no idea what dark matter or dark energy is. The constant dark energy [theory] is already sufficiently challenging. I feel like: 'As if things were not complicated enough.' 'But you can also look at it more positively. For 20 years we've been stuck with dark energy. Now physicists have new questions.'
