I listened to a radio interview physicist Leonard Susskind, founder of string theory. Susskind said that he thought a multiverse was possible, and if it was real it would be a series of universes one after the other rather than parallel universes. OK, except that this could never be scientifically verified, right? It's a non-verifiable theory.
Multiverse theory is popular now, but not among all physicists. It's fascinating and it's a lot of fun thinking about a near-infinity of other "me's" that exist simultaneously with the me who is typing these words. Really? Yes, says physicist Max Tegmark, who believes that in the multiverse "all possible states exist at every instant." Which means there are a host of "Max Tegmarks" in coexisting parallel universes. Tegmark says, ‘I feel a strong kinship with parallel Maxes, even though I never get to meet them. They share my values, my feelings, my memories – they’re closer to me than brothers.’
But, sadly, such thoughts are non-scientific. On this see Philip Ball's critical essay "Too Many Worlds." The Many Worlds Interpretation (MWI) has lots of glamour and publicity. "It tells us that we have multiple selves, living other lives in other universes, quite possibly doing all the things that we dream of but will never achieve (or never dare). Who could resist such an idea?"
Well, we should resist it, argues Ball. He writes:
"We should resist not just because MWI is unlikely to be true, or even because, since no one knows how to test it, the idea is perhaps not truly scientific at all. Those are valid criticisms, but the main reason we should hold out is that it is incoherent, both philosophically and logically. There could be no better contender for Wolfgang Pauli’s famous put-down: it is not even wrong."
Ball's essay gives reasons to question the non-scientific implications of MWI. He concludes:
"If the MWI were supported by some sound science, we would have to deal with it – and to do so with more seriousness than the merry invention of Doppelgängers to measure both quantum states of a photon. But it is not. It is grounded in a half-baked philosophical argument about a preference to simplify the axioms. Until Many Worlders can take seriously the philosophical implications of their vision, it’s not clear why their colleagues, or the rest of us, should demur from the judgment of the philosopher of science Robert Crease that the MWI is ‘one of the most implausible and unrealistic ideas in the history of science’."
Shall we assume our universe is the only world there is?
