Dark energy weakening, potentially altering universe’s fate, scientists say

Dark energy, the mysterious force driving the universe’s expansion, appears to be weakening, scientists announced on Thursday, potentially upending long-held theories about the cosmos’s ultimate fate, according to a report by The Guardian.

The findings from the Dark Energy Spectroscopic Instrument (DESI) team suggest the force has declined by approximately 10 percent since reaching peak strength when the universe was about 70 percent of its current age.

If confirmed, the discovery could replace the prevailing “big freeze” theory of universal demise with a potential “big crunch” scenario, where expansion eventually reverses.

“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,” said Prof Alexie Leauthaud-Harnett, DESI co-spokesperson and cosmologist at the University of California, Santa Cruz.

The observations come from DESI’s latest data release capturing 15 million galaxies spanning 11 billion years of cosmic history, creating the most detailed three-dimensional map of the universe to date.

While the results have not reached physics’ gold standard of statistical certainty, many collaboration members now strongly support the findings.

“What we’re finding is that, yes, there is something pushing galaxies away from each other, but it is not constant. It is declining,” said Prof Carlos Frenk, cosmologist at the University of Durham and DESI collaboration member.

Dark energy was discovered in the late 1990s when astronomers found the universe’s expansion was accelerating rather than slowing as expected due to gravity’s counteracting force.

Scientists have generally assumed dark energy to be constant, accounting for approximately 70 percent of the universe alongside dark and ordinary matter.

The new findings, announced at the American Physical Society’s Global Physics Summit in Anaheim, California, suggest the universe’s expansion is still accelerating but at a gradually decreasing rate.

“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,” Frenk said.

Prof John Peacock, University of Edinburgh cosmologist and DESI collaborator, expressed similar confidence: “Extreme claims require extreme evidence. There’s almost nothing in science that I would bet my house on. But I would put £1,000 on this result”.

Others remain cautious. “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,” said Prof George Efstathiou of the University of Cambridge, who was not involved in the findings.

Scientists do not yet understand why dark energy might be weakening or whether this indicates missing components in physical laws.

“It’s fair to say we have no idea what dark matter or dark energy is,” said Prof Ofer Lahav, astronomer at University College London and DESI collaborator.

“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”.

(information from The Guardian)