BIG CRUNCH

 A cyclical universe is one of those things we want to be true.

Bouncy, bouncy

The current model of the universe, where it all ends in a heat death, is a bit depressing. We’ll all exist here for an eternity and when it’s all over the universe will be just a cold, empty, dark place to be. It’s depressing really and also rather anticlimactic. There was this big, huge, violent beginning and a pathetic wimper at the end.

I hope the hypotehsis proposed by Roger Penrose is true. His conjecture is fascinating: in the earliest epoch of the universe, it was at the point of thermal equilibrium. We know this from studies of Cosmic Microwave Background, there were only very slight pertubations in temperature universe-wide. However this is, by definition, a very low entropy state right at the beginning. And the heat death of the universe is also a low entropy state, so what gives?

Well, Penrose proposed that if matter has a finite lifespan, protons and other basic particles spontaneously decay eventually, there will come a moment in the universe where no matter exists at all. However without matter, time no longer describes anything, because photons don’t experience time. Time doesn’t stop, it disappears as a feature of the universe, because it no longer describes anything within it. However time and space are intrinsically connected, if two points are some distance apart, they have to be some time apart as well. Therefore the moment time doesn’t describe anytihng any more, neither does distance and all distances disappear as well.

Therefore the heat death of the universe, once the last proton decays, is the initial moment of the Big Bang.

I like the hypothesis, because it’s so clean and also because it says something we all want to be true. A cyclical universe is a whole lot more interesting than one that sprouted into existence and will continue to exist in an irrelevant state for what might as well be an eternity. There’s no magic involved, once you realise this implies distances and time are not intrinsic to the universe, but emergent phenomena of properties of matter. We don’t know if this is the case, but it could be.

I’ll also mention Roger Penrose isn’t some kook who makes youtube videos. He won the Nobel prize in Physics in 2020.