Although some scientists have analyzed data in search of evidence for other universes, no statistically significant evidence has been found. Critics argue that the multiverse concept lacks testability and falsifiability, which are essential for scientific inquiry, and that it raises unresolved metaphysical issues.

Pretty much any time subatomic particles interact with each other or with anything else anywhere in the universe, there are multiple possible outcomes, which means a lot of branching of history. There may even be infinitely many branches. So is the many-worlds hypothesis true? We don't know.

A Type III multiverse would be a consequence of the many-worlds interpretation of quantum mechanics, in which quantum events with probabilistic outcomes resolve in all ways at once, passing into a vast number of Everett branches each considered to be its own universe.

Quantum physics deals with subatomic particles, which are the building blocks of all matter. So, in that sense, we already exist in a quantum reality, Kolodrubetz said. And because people are made of quantum particles, they are quantum mechanical beings. Rather than being a place, quantum physics is about size.