The existence of parallel universes may seem like something cooked up by science fiction writers, with little relevance to modern theoretical physics. But the idea that we live in a “multiverse” made up of an infinite number of parallel universes has long been considered a scientific possibility — although it is still a matter of vigorous debate among physicists.
The race is now on to find a way to test the theory, including searching the sky for signs of collisions with other universes. It is important to keep in mind that the multiverse view is not actually a theory, it is rather a consequence of our current understanding of theoretical physics. This distinction is crucial. We have not waved our hands and said: “Let there be a multiverse.” Instead the idea that the universe is perhaps one of infinitely many is derived from current theories like quantum mechanics and string theory.
