why, and when, can we use mathematics to learn something about our physical Universe? We don’t know the answer to why, but we do know the answer to when: when it agrees with our experiments and observations. So long as the laws of physics remain the laws of physics, and do not whimsically turn on-and-off or vary in some ill-defined way, we know we can describe them mathematically, at least in principle. Mathematics, then, is the toolkit we use to describe the functioning of the Universe. It’s the raw materials: the nails, the boards, the hammers and saws. Physics is how you apply that mathematics. Physics is how you put it all together to make sense of your materials, and wind up with a house, for example, instead of a collection of parts that could, in principle, be used to build something entirely different. More.
It’s interesting that Siegel’s definition makes physics out to be rather pragmatic. It doesn’t allow for wars on evidence such as those waged by multiverse advocates. In other words, the multiverse is probably a war on the implications of mathematics for physics as well.
Nonetheless, he thinks that the multiverse is inevitable and we’re living in it. That’s very PoMo.
See also: At Forbes: Wishing the multiverse into existence
Astrophysicist: The multiverse absolutely must exist but won’t “fix physics”
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.