Is dark energy weakening?
A new 3D map of the universe suggests that dark energy is “evolving”—a finding that would upend everything we thought we knew about our expanding universe. Dark energy, the mysterious force that accounts for about 70 percent of the universe, is thought to be responsible for the accelerating expansion of the cosmos. But new data show that it may not be a constant, unchanging force, but instead appears to be weakening. That would be “a very big deal,” Adam Riess, a Johns Hopkins University professor who won a Nobel prize for discovering dark energy, tells New Scientist. “It would be the first real clue we have gotten about the nature of dark energy in 25 years.” The current thinking holds that right after the Big Bang rapidly expanded the universe, gravity began to slow the rate of expansion down, but that billions of years later the pace began to rev back up, driven by an unknown force we named dark energy. Such an expansion implies that all life, light, and energy will eventually wink out, as stars and galaxies race further apart in a “Big Freeze.” But that gloomy prediction, the new data suggests, may need rewriting. The findings come from the Dark Energy Spectroscopic Instrument in Arizona, a huge high-tech telescope that observes 100,000 galaxies every night as part of a massive project to map the universe. “It’s all we’ve been talking about for months,” says DESI spokesman Kyle Dawson. “It’s really motivating us.”