Asked by: Henry Parr, Bristol
Although the ‘Big Crunch’ idea is currently out-of-favour with cosmologists, it is still one possible fate for the Universe.
However, the eventual endpoint of the Big Crunch is not known. In simple terms, if we regard it as the opposite of the Big Bang, we might indeed expect that all matter and space-time itself would collapse into a ‘singularity’: an infinitely dense point similar to that from which the Universe appears to have sprung.
But singularities are notoriously difficult notions to investigate scientifically, so modern physics can say very little about what might ultimately happen during the Big Crunch.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.