Prompted by reading about the recent Munich conference on the philosophy of science, I am reminded that many people regard the idea of a multiverse as so wild and wacky that talking about it brings science into disrepute. My argument here is the reverse: that the idea of multiple Big Bangs, and thus of a multiverse, is actually more mundane and prosaic than the suggestion that there has only ever been one Big Bang. I’m calling this a “philosophical” argument since I’m going to argue on very general grounds rather than get into the details of particular cosmological models.
First, let me clarify that several different ideas can be called a “multiverse”, and here I am concerned with only one. That “cosmological multiverse” is the idea that our Big Bang was not unique, but rather is one of many, and that the different “universes” created by each Big Bang are simply separated by vast amounts of space.
Should we regard our Big Bang as a normal, physical event, being the result of physical processes, or was it a one-off event unlike anything else, perhaps the origin of all things? It is tempting to regard it as the latter, but there is no evidence for that idea. The Big Bang might be the furthest back thing we have evidence of, but there will always be a furthest-back thing we have evidence of. That doesn’t mean its occurrence was anything other than a normal physical process.
If you want to regard it as a one-off special event, unlike any other physical event, then ok. But that seems to me a rather outlandish idea. When physics encounters a phenomenon, the normal reaction is to try to understand it in terms of physical processes. Continue reading