Dark energy, which drives the universe’s expansion, is showing signs of weakening, according to research that could fundamentally alter our understanding of the cosmos’s destiny.
The findings from the dark energy spectroscopic instrument (Desi) team at Kitt Peak National Observatory in Arizona could significantly impact theories about universal evolution, suggesting the possibility of a reversal in expansion leading to a “big crunch“.
This indication that dark energy peaked billions of years ago represents the first significant modification to the accepted universal model in decades, Guardian reported.
“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.
Scientists discovered dark energy in the late 1990s whilst studying distant supernova explosions to understand cosmic expansion rates. Rather than gravity slowing the post-big bang expansion, they found acceleration driven by an unknown force, subsequently termed dark energy.
The findings, presented at the American Physical Society’s Global Physics Summit in Anaheim, California, challenge the notion of dark energy as a constant force, which previously suggested a “big freeze” end to the universe.
Desi’s 5,000 fibreoptic sensors have created the most detailed three-dimensional universal map yet, observing 15m galaxies across 11bn years of history.
Analysis indicates dark energy peaked when the universe was approximately 70% of its current age and has since decreased by about 10%. This suggests continued acceleration, albeit at a diminishing rate.
Prof Carlos Frenk from the University of Durham and Desi collaborator stated: “What we’re finding is that, yes, there is something pushing galaxies away from each other, but it is not constant. It is declining.”
While not meeting physics’ five-sigma threshold for definitive discovery, many researchers now support these findings with increasing confidence.
Prof John Peacock from the University of Edinburgh, initially sceptical, now strongly supports the results, stating: “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.”
Should dark energy continue decreasing to negative values, the universe could end in a big crunch scenario.
Scientists remain uncertain about why dark energy, comprising approximately 70% of the universe alongside dark and ordinary matter, might be diminishing, or whether this indicates incomplete or changing physical laws.
Prof Ofer Lahav from University College London noted: “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.”
