There is many-universe interpretation of quantum mechanics, invented in the 1950s by Hugh Everett, who was then a student in Princeton. Everett imagined the quantum universe as an infinite assemblage of ordinary universes all existing simultaneously. He called the assemblage the multiverse.
The essence of quantum physics is unpredictability. At every instant, the objects in our physical environment—the atoms in our lungs and the light in our eyes—are making unpredictable choices, deciding what to do next.
According to Everett and David Deutsch, the multiverse contains a universe for every combination of choices. There are so many universes that every possible sequence of choices occurs in at least one of them.
I take this to mean that even if i decided not to brush my teeth last night another me has done it in another unverse.
Everet and Deutsch believe that Each universe is constantly splitting into many alternative universes, and the alternatives are recombining when they arrive at the same final state by different routes.
The multiverse is a huge network of possible histories diverging and reconverging as time goes on.
The "quantum weirdness" that we observe in the behavior of atoms, the "spooky action at a distance" that Einstein famously disliked, is the result of universes recombining in unexpected ways.
According to Deutsch, each of us exists in the multiverse as a crowd of almost identical creatures, travelling together through time along closely related histories, splitting and recombining constantly like the atoms of which we are composed.
OK? Now that we have got that out of the way, have a good day