Though the concept may be far-fetched, there's good physics behind it; and there's not just one way to get to a multiverse — numerous physics theories independently point to such a conclusion. In fact, some experts think the existence of hidden universes is more likely than not.
These are the leading plausible theories that suggest that we live in a multi-verse.
The Infinite Universe theory hints that the universe might be flat, rather than spherical as first notion-ed by scientists. The idea revolves around the concept that space-time goes on forever, and since there are only a finite number of ways particles can be arranged in space and time, it is believed that at some point, between the stretch, there are reoccurrences of certain universes.
In one universe, you could be a lawyer and the next a hippie, looking for ways to legalize weed. The same person, but alternate life. Because the observable universe extends only as far as light has had a chance to get in the 13.7 billion years since the Big Bang (that would be 13.7 billion light-years), the space-time beyond that distance can be considered to be its own separate universe.
The next notion seems even more mind boggling. It’s known as the Bubble Universe theory or Eternal Inflation. This suggests that the universe expanded rapidly after the Big Bang, in effect inflating like a balloon. Eternal inflation, first proposed by Tufts University cosmologist Alexander Vilenkin, suggests that some pockets of space stop inflating while other regions continue to inflate, thus giving rise to many isolated "bubble universes."
The daughter universe idea can be considered the least likely of the truths. The theory of quantum mechanics, which reigns over the tiny world of subatomic particles, suggests another way multiple universes might arise. Quantum mechanics describes the world in terms of probabilities, rather than definite outcomes. And the mathematics of this theory might suggest that all possible outcomes of a situation do occur in their own separate universes. For example, if you reach a crossroads where you can go right or left, the present universe gives rise to two daughter universes: one in which you go right, and one in which you go left.
Last but certainly not least, the idea of mathematical universes. Scientists have debated whether mathematics is simply a useful tool for describing the universe, or whether math itself is the fundamental reality, and our observations of the universe are just imperfect perceptions of its true mathematical nature. If the latter is the case, then perhaps the particular mathematical structure that makes up our universe isn't the only alternative, and, in fact, all possible mathematical structures exist as their own separate universes. There’s some inception for you to think about tonight.