For cosmologists, the origin of the universe is clear. Galaxies are accelerating away from each other, and when this motion is reversed, the universe contracts into a single event. This suggests that the Big Bang occurred some 14 billion years ago.
Astronomers, on the other hand, aren’t quite sure how it will all end. Perhaps the universe will continue to expand at an ever-increasing rate because of a mysterious force known as dark energy? Otherwise, the expansion will continue indefinitely.
Another possibility is that dark energy’s influence will diminish over time, resulting in a smooth transition from rapid expansion to slow contraction. There is a strong correlation between this possibility and the idea that the universe is constantly expanding and contracting in a continuous cycle.
In light of the second possibility, it begs the question of when it will all happen.
We’re closer than we realise.
Now A team led by Princeton University’s Cosmin Andrei has used theoretical models that are in line with current observations to investigate this issue in-depth. And they say it could begin sooner than we think, perhaps on a timescale of millions rather than billions of years..
Dark energy’s properties may change over time, but the universe as astronomers currently see it remains consistent with these changes. When they’ve done this, they figure out how long it will be before these transitions can begin.
The findings are interesting to read. “Strikingly soon, cosmologically speaking,” Andrei and co. say the minimum time before the acceleration ends is. Their claims are supported by the fact that they can be compared to geologic timescales.
It has been estimated that, in one scenario, we have approximately the same amount of time left until expansion stops as Earth has had life on it. 3 or 4 billion years.
Timeline of Dinosaurs
There are other scenarios in which “the time interval remaining before the end of acceleration is less than the time since asteroid Chicxulub wiped out the dinosaurs.” In cosmological terms, that’s just 65 million years.
Astronomers, on the other hand, have some bad news. It is unlikely that astronomers would be able to detect the end of the expansion that quickly. “Curiously, given the best available observations today,” say Andrei and co., “we could not detect the oncoming dramatic cosmic events.”
That’s because the evidence comes from distant objects that emitted light billions of years ago, like supernovas, and the cosmic microwave background, which is an echo of the Big Bang itself.
Although the authors suggest that there may be other ways to look for it, these objects will not show evidence of this change for a long time.
As a final thought, Andrei and co. discuss why the end of expansion should occur now, at the exact time that life has emerged to witness it. Because the universe alternates between expanding and contracting, there is only a brief period of time during each cycle when conditions are ideal for life to begin. So, that’s about where we are right now.
“The end of expansion could occur surprisingly soon,” they conclude, based on all of this. However, there’s no need to worry just yet.