Cutting spacetime into patches could help explain the size of the universe—and provide the first ”experimental” evidence that string theory is on the right track.
No one really knows the answer to this question. It's quite possible that there are more than one, in fact there may be infinitely many, popping in and out of existence like bubbles in a bubble bath.
There are many theories in particle physics that cannot be tested in experiments. Does this make it unscientific? This debate, featuring one of our favourite theoretical physicists, David Tong, explores the question.
Are there parallel universes? Universes in which, rather than reading this article, you are still asleep; in which you are happier, unhappier, richer, poorer, or even dead? The answer is "possibly". It's a controversial claim but one that has won more and more followers over the last few decades.