It’s possible: the idea of parallel universes or the multiverse has been around in science fiction for many years and is now being seriously considered by scientists as a possible reality. There are a number of options for these models, but three are most often discussed.
The first is the idea of ‘bubble universes’, where other universes could exist either so far away from us that we will never observe each other (as light has a finite speed) or inside the singularities in the centre of black holes, where our understanding of physics breaks down completely.
The second is the idea of membranes and extra dimensions. This is partly inspired by String Theory’s predictions of many more dimensions than we observe, and suggests that everything we know of in three dimensions is only part of a much larger universe with many more dimensions. Almost like we are living on one flat sheet of paper which is really connected to many more sheets in the form of a book.
The third comes from quantum mechanics and is called the theory of many worlds. This suggests that every possible alternate timeline for the universe is real and they all branch out from one another, creating a different universe each time any decision is made. Currently there is no agreed observational evidence for any of these theories, but scientists are certainly looking!
Answered by Megan Whewell from the National Space Centre
Image credit: Silver Spoon