This admittedly catchy idea is undermining the integrity of physicsby Jim Baggott / June 25, 2018 / Leave a comment
Over the last few decades “multiverse theories” have become increasingly fashionable within a relatively small—but publicly vocal—group of theoretical physicists. This group specialises in foundational problems in cosmology, particle physics, and quantum mechanics. These theories are advertised as science’s answer to much that we can’t otherwise explain about the universe we inhabit, the elementary particles we have discovered in it, and the reasons for our own existence.
It’s “theories” plural because the multiverse is used in various ways to fill gaps in our current understanding. Cosmological multiverse theories “explain” why the initial conditions that prevailed at the Big Bang origin of our universe, and the physical constants and laws which shaped its subsequent evolution, appear so exquisitely fine-tuned to allow for the possibility of life. The idea is that there’s nothing particularly special about our “Goldilocks” universe: it is simply one of a (possibly infinite) number of universes, all with different initial conditions, constants, and laws. Most will be inhospitable, but it should come as no surprise to find ourselves in a universe which isn’t.
Multiverse arguments are also used by some string theorists to “explain” why they’re unable to identify a specific formulation of the theory (among 10500 different possibilities) that uniquely describes the elementary particles in our universe and the forces that act between them. Their answer is that these possibilities form a “landscape” or a continuum—a multiverse—and once again it’s no surprise to find ourselves in the one structure hospitable to life, whatever that may be. Job done.
Finally, current theories of particle physics are based on a version of quantum mechanics, which has a reputation for not being understandable. Among the great variety of different possible interpretations of quantum theory, the “many worlds” interpretation attempts to understand it by introducing the notion of parallel universes, all equally real. One leading theorist has declared that such a “quantum multiverse” is as real as dinosaurs once were, and we should just get over it.
This is all very well, but the multiverse is also extremely controversial, with some scientists publicly voicing the concerns of many by arguing that it is entirely metaphysical. It is really no more than an idea bandied about as a handy way to fill some admittedly significant explanatory gaps in our current theories. In this sense it is used much as the mechanical philosophers of the…