An international team of astronomers on Wednesday unveiled the most compelling evidence to date that dark energy — a mysterious phenomenon pushing our universe to expand ever faster — is not a constant force of nature but one that ebbs and flows through cosmic time.
Dark energy, the new measurement suggests, may not resign our universe to a fate of being ripped apart across every scale, from galaxy clusters down to atomic nuclei. Instead, its expansion could wane, eventually leaving the universe stable. Or the cosmos could even reverse course, eventually doomed to a collapse that astronomers refer to as the Big Crunch.
The latest results bolster a tantalizing hint from last April that something was awry with the standard model of cosmology, scientists’ best theory of the history and the structure of the universe. The measurements, from last year and this month, come from a collaboration running the Dark Energy Spectroscopic Instrument, or DESI, on a telescope at Kitt Peak National Observatory in Arizona.
“It’s a bit more than a hint now,” said Michael Levi, a cosmologist at Lawrence Berkeley National Laboratory and the director of DESI. “It puts us in conflict with other measurements,” Dr. Levi added. “Unless dark energy evolves — then, boy, all the ducks line up in a row.”
The announcement was made at a meeting of the American Physical Society in Anaheim, Calif., and accompanied by a set of papers describing the results, which are being submitted for peer review and publication in the journal Physical Review D.
“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, an astrophysicist at Johns Hopkins University and the Space Telescope Science Institute in Baltimore who was not involved in the work but shared the 2011 Nobel Prize in Physics for discovering dark energy, wrote in an email.