It seems like just yesterday the dinosaurs were frolicking about the canyons of Pangaea, living their last few oblivious moments before an asteroid changed everything. You don’t really notice it while it’s happening, but 65 million years goes by pretty fast.
At least it does in the grand scheme of things. The universe has been around some 14 billion-or-so years according to the Big Bang Theory. In that context, 65 million years is just a few flakes of sand in a giant hourglass.
And that makes it all the more scary to read a pre-print research paper suggesting that our universe may only have a measly 65 million years of expansion left.
Once that expansion ends: it’s lights out. The universe will transition to a (hopefully) slow contraction until it becomes a single infinitesimal point made up of all the matter that’s ever been and ever will be.
At this point, according to scientists, the Big Bang will happen. Again.
A broken clock
The truth of the matter is that we have no way of knowing if and when the universe is going to end. It’s not that we don’t have the technology. We don’t have the perspective.
When we look up at the stars we’re gazing at light that’s traveled for millions or even billions of years. Some of those stars don’t even exist anymore.
Yet, by observing these distant lights we’re able to determine that the universe is expanding. And, in a series of simulations, scientists have used that data to try and figure out whether that expansion is infinite or if there’s some sort of universal reckoning coming.
To that end, a team of scientists from Princeton and NYU recently published a pre-print research paper describing the problem. According to them, if dark energy is responsible for the universe’s expansion, it’s plausible the energy could wind down and lead to a contraction.
Per their paper:
If dark energy is a form of quintessence driven by a scalar field evolving down a monotonically decreasing potential that passes sufficiently below zero, the universe is destined to undergo a series of smooth transitions: the currently observed accelerated expansion will cease; soon thereafter, expansion will come to end altogether; and the universe will pass into a phase of slow contraction.
Basically: the universe gets big, then it gets small.
However, as mentioned above, we’re in no position to know when this will happen. All we can do is guess.
According to the scientists:
The problem is that accurate cosmological measures of the expansion rate and other cosmological parameters are based on observations of the cosmic microwave background, baryon acoustic oscillations and distant objects, like supernovae, whose detected light was emitted far in the past, whereas, as we have shown, the transitions to deceleration and slow contraction may all occur within a small fraction of a Hubble time. For this reason, it is a challenge to detect the end of contraction even when the time is nigh.
And that means, for all we can tell, the universe could continue expanding for billions of years. Or, perhaps, the time is already nigh.
The Physics arXiv Blog describes the researchers’ time-frame as such:
In one scenario they say the minimum time remaining before the end of expansion is roughly equal to the period since life has existed on Earth. That’s 3 or 4 billion years.
In another scenario, they calculate that “the time interval remaining before the end of acceleration is less than the time since the Chicxulub asteroid brought an end to the dinosaurs.” That’s just 65 million years—the blink of an eye in cosmological terms.
The end of days
Right now, that 65 million years time-frame is just a guess. But if we could definitively determine that our universe has such a short amount of time before it starts contracting, the ramifications of this knowledge could have immediate, far-reaching impacts on humanity.
It would essentially mean we’re unlikely to ever find alien life. This simply boils down to the odds: if we look at 65 million years as the final few flakes in our universe’s hourglass, we have to concede that time’s almost up for all living beings.
If we haven’t found each other by now, the odds are mathematically against it ever happening.
Between expansion spreading us apart and contraction ultimately resulting in everything in the universe being compressed to a single point, it may even be pragmatic to give up the search all together and focus on something else. We could use our space resources to advance the goal of spreading Earth’s life throughout the galaxy, for example.
The universe may only have a little time left, but it’s worth making sure we’re all there to watch the grand finale. That is, of course, unless the world really did end in 2012.
The scientists also postulated that the universe’s expansion and contraction were cyclical, meaning another Big Bang is likely imminent.
On the bright side, this would mean there’s almost certainly going to be life again once we’re gone. But, on the not-so-bright-side, it also makes it less likely that life is prolific.
With such a tiny window for life to miraculously appear during each expansion and contraction cycle, planets like Earth might be once-in-a-Big-Bang occurrences.