Fate of the Universe May Be Far Different Than Predicted

Cosmologists say new findings about a mysterious force called dark energy have upended their predictions about the eventual fate of the universe. For decades, researchers believed that the force powering the expansion of the universe was a "cosmological constant" that did not change over time, Nature reports. Scientists with the Dark Energy Spectroscopic Instrument—DESI—survey, however, say their observations suggest that the force has been weakening for billions of years, since the universe was around 70% of its current age. The findings suggest the "rate of expansion is still accelerating, but that dark energy is gently lifting its foot off the pedal," the Guardian reports. Researchers believe the force is now 10% weaker than it was a few billion years ago.

At a meeting of the American Physical Society on Wednesday, DESI researchers said there is not enough evidence yet to raise the findings on "evolving dark energy" to the level of a discovery, but they are growing more confident that it's not just a "blip" in the data, the BBC reports. "It is a dramatic moment," says Ofer Lahav, one of hundreds of researchers on the DESI team. "We may be witnessing a paradigm shift in our understanding of the universe." The team has mapped almost 15 million galaxies and quasars and aims to bring the total to 60 million by the end of next year.

Researchers still have many more questions than answers about the true nature of dark energy, but the findings raise multiple possibilities about the eventual fate of the universe. Constant expansion would lead to a "Big Freeze" and a cold, lifeless universe trillions of years in the future, but the new findings suggest that if dark energy fades over time, the universe will eventually collapse on itself in a "Big Crunch," the AP reports. "Now, there is the possibility that everything comes to an end," says DESI team member Mustapha Ishak-Boushaki. "Would we consider that a good or bad thing? I don't know." The Washington Post notes that it's also possible that expansion will speed up again—or that "the universe will settle down into a serene maturity, never in a rush, imperturbable." (More dark energy stories.)