Physicists have proposed a new theory that hints that the universe, now expanding, may reach a turnaround point, and start collapsing in on itself. This mechanism of “cosmological collapse” suggests that the universe, in a time of an order of a few tens of billions of years or so, will stop expanding and start collapsing, imminently obliterating all matter as we know. Billions of years may seem like a long, long time for us, but for physicists, it is still much too soon. This mechanism has been analyzed by the physicists of University of California and University of Nottingham and its implications have been proposed, which include an explanation of dark energy.
This new finding and proposal, more importantly, may answer some questions that have kept physicists puzzled. Questions as to why the universe is expanding at an accelerating rate, and what is the dark energy causing this acceleration? These questions are related to the mother of all physics problems- the cosmological constant problem, which is that the predicted vacuum energy density of the universe causing the expansion is much larger than what is observed. This theory, which is built on previous research on the vacuum energy sequestering, addresses a brand new approach to this problem. The dynamics of vacuum energy sequestering predict that the universe will collapse, but did not provide any mechanism that explained the same.
According to the new mechanism, the universe originated under a specific set of initial conditions. In this scenario, once the collapse trigger begins to dominate, it does so in a period of “slow roll” that brings about the accelerated expansion we see today. Eventually, the universe will stop expanding and will start collapsing, ultimately terminating in a “big crunch”.
Presently, the universe, approximately 13.8 billion years old, is expanding and for it to start collapsing, the period of accelerated expansion must last until at least this time. According to the physicists, the naturalness of this mechanism makes it one of the first ever models that predicts acceleration without any direct fine tuning.
This idea is still in its early stages, but physicist hope to build on it much more. They are currently working on a way to describe the theory locally to make it more conventional, in keeping with some of the key principles behind quantum theory. Further, they would like to understand how this theory could emerge from a more fundamental theory such as string theory.
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