A new computer model for the origin of the universe lends credence to the idea that the Big Bang was actually more of a Big Bounce. If the model is correct, that means our universe will not be facing demise in the form of a Big Crunch several millennia from now - so you can let out a sigh of relief.
The Big Bang is the more well-known theory of how the universe came to be: emerging from a singularity of infinite temperature and density. According to Science Alert, the Big Bounce is a similar concept, but it proposes that the expansion of our universe was preceded by a state of contraction. That is, the universe is alternately expanding and contracting - it has done so before, and it will do so again.
The idea has been bouncing around since 1922, although the popular nickname did not appear in scientific literature until the '80s. The theory did not manage to gain much acceptance among cosmologists, since Big Bounce theorists have been unable to explain how the universe would be able to transition from the state of contraction to that of expansion.
A new study published in Physical Review Letters has come up with a plausible explanation. Penned by Steffen Gielen of the Imperial College London and Neil Turok of the Perimeter Institute for Theoretical Physics in Canada, the article proposes that when the universe contracts, it becomes so tiny that its physics is defined entirely by quantum mechanics, the science of the very small.
Quantum mechanics deals with the world of sub-atomic particles, which is very different from our everyday world of regular matter. Physics is different for objects on a quantum scale. But some cosmologists think that this divide did not exist in the very early universe - back then, physics at the sub-atomic scale would have been the same as physics of much larger matter.
Gielen and Turok's model envisions the universe in contraction as experiencing quantum effects that keep it from collapsing permanently in a Big Crunch, instead allowing it to transition into a new expansion. Their model includes the minimal requirements needed for the universe's expansion - that it is filled with radiation and contains almost no matter.
Turok says on Phys.org, "The big surprise in our work is that we could describe the earliest moments of the hot Big Bang quantum mechanically, under very reasonable and minimal assumptions about the matter present in the universe. Under these assumptions, the Big Bang was a 'bounce', in which contraction reversed to expansion."