“The universe is curling up on the sofa like a couch potato,” said astronomer Joe Liske from the European Southern Observatory in reference to a new study released on Monday, which suggests that the universe is getting dimmer.
In the study, researchers released conclusive evidence that the universe has lost half its brightness over the past 2 billion years, as older stars die faster than new ones are born. The evidence also suggests it stands to lose much more over the next 2 billion.
Star formation peaked around 8 billion years ago, when the universe contained higher levels of hydrogen and helium, which are necessary for fusion reactions that occur when a star is born. As the universe continues to expand, this cosmic fuel becomes sparser and sparser.
The international team analyzed 220,000 galaxies using land and space telescopes, which observed an area about the size of 1000 moons. To measure the dimming, astronomers conceptualized the universe in enormous cubes of one million square light years and measured different wavelengths of light. The oldest cubes glowed with a brightness of 19 million suns, while the youngest glowed with a brightness of only 11 million suns. The younger the galaxies are, the dimmer their glimmer, as fewer and fewer stars are forming.
While it’s certainly unsettling to imagine the universe as a countdown clock, the impact for us is far from imminent.
“The universe is not going to go black anytime soon,” said Will Sutherland, an astronomer at Queen Mary, University of London, who estimates it will be several billion years before the dimming has any effect. “But it’ll fade. And then what you’re left with is little old red stars that shine away for a long time more.”
But as compelling as the evidence is, not all scientists are buying into the theory—other recent ideas suggest a very different fate for the cosmos.
The belief that the universe will slowly fade to black is challenged by a new theoretical model released last month from scientists at Vanderbilt University in Tennessee, which suggests a far more dramatic finale than a quiet demise. The model predicts that the universe will split in two before all the lights go out, pulled apart by rapid growth. In about 22 billion years, the model predicts the growth rate of the universe will approach infinity, at which point the cosmos will literally rip in two.
“Under the rip scenario, dark energy gets stronger and you get this wild expansion that essentially rips space-time apart,” said Marcelo Disconzi, who led the work at Vanderbilt. “The universe would vanish in front of your eyes. Basically, you don’t want to be around for it.”
And we won’t be—we won’t be around for either scenario: a silent dimming or a furious finale. We’re not even certain that they’ll ultimately occur.
Humankind has spent virtually all of its history reaching: for new lands, across expansive oceans, and just recently, even further afield, to the stars. But researchers today already know the stars. They’ve mapped them; they’ve seen them through telescopes and satellite images. Researchers today are reaching through time itself, all the way to the beginning and all the way to the end in search of what might become of this vast, unknowable creature: our universe.
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