A number of theories independently point to the conclusion that we live among a number of hidden universes, or a multiverse. For one, space-time is most likely flat, rather than spherical or donut-shaped, and stretches out infinitely. “But if space-time goes on forever, then it must start repeating at some point, because there are a finite number of ways particles can be arranged in space and time. So if you look far enough, you would encounter another version of you — in fact, infinite versions of you,” Space.com explains.
Other universes could also arise from a theory called eternal inflation. Inflation is the notion that the universe expanded rapidly after the Big Bang, like a balloon. While some pockets of space stop inflating, other regions continue expanding. Our own universe, where inflation has come to a halt, allowing stars and galaxies to form, “is but a small bubble in a vast sea of space — some of which is still inflating — that contains many other bubbles like ours. And in some of these bubble universes, the laws of physics and fundamental constants might be different than in ours, making some universes strange places indeed,” the article suggests.