It’s good when they come right out and say that. From Sean Carroll at Arxiv:
Cosmological models that invoke a multiverse – a collection of unobservable regions of space where conditions are very different from the region around us – are controversial, on the grounds that unobservable phenomena shouldn’t play a crucial role in legitimate scientific theories. I argue that the way we evaluate multiverse models is precisely the same as the way we evaluate any other models, on the basis of abduction, Bayesian inference, and empirical success. There is
no scientifically respectable way to do cosmology without taking into account different possibilities for what the universe might be like outside our horizon. Multiverse theories are utterly conventionally scientific, even if evaluating them can be difficult in practice.
More.
The multiverse is probably unfalsifiable for the same reasons as leprechauns are unfalsifiable. You’ll never convince a true believer.
And then what about Occam’s razor? One can do science without the multiverse for the same reasons as one can do it without leprechauns. It would be more honest for people like Carroll to just admit that they need to believe this stuff and if they can impose it on the science public, they have solved a lot of problems (their own).
Falsifiability – propositions must be framed in such a way that they could be shown to be untrue – is not the only standard in science but it is the one that best protects science from becoming the mere imposition of establishment dogma. Funny it should be under attack just now…
See also: Astrophysicist: The multiverse absolutely must exist but won’t “fix physics” So is Ethan Siegel saying that fellow astrophysicist Sean Carroll is giving up on physics? Probably. Maybe physics is best off to just be whatever physicists currently consider a community of practice as long as it isn’t claiming any special status as a field of knowledge.
Sean Carroll and Brute Facts (Barry Arrington)
Theoretical physicist: Reasons to be skeptical of the multiverse Bookmark this for the next airhead invasion of your local Great Ideas discussion group.
and
Theoretical physicist: Multiverse not based on sound science reasoning Good points But what if multiverse theory is simply a means of fending off the impasses that fully naturalist theoretical physics is in? It doesn’t need to make sense, any more than bollards do.