Even Physicists Find the Multiverse Faintly Disturbing

How do you feel about the multiverse?” The question was not out of place in our impromptu dinner-table lecture, yet it caught me completely off-guard. It’s not that I’ve never been asked about the multiverse before, but explaining a theoretical construct is quite different to saying how you feel about it. I can put forth all the standard arguments and list the intellectual knots a multiverse would untangle; I can sail through the facts and technicalities, but I stumble over the implications.

In physics we’re not supposed to talk about how we feel. We are a hard-nosed, quantitative, and empirical science. But even the best of our dispassionate analysis begins only after we have decided which avenue to pursue. When a field is nascent, there tend to be a range of options to consider, all of which have some merit, and often we are just instinctively drawn to one. This choice is guided by an emotional reasoning that transcends logic. Which position you choose to align yourself with is, as Stanford University physicist Leonard Susskind says, “about more than scientific facts and philosophical principles. It is about what constitutes good taste in science. And like all arguments about taste, it involves people’s aesthetic sensibilities.”

My own research is in string theory, and one of its features is that there exist many logically consistent versions of the universe other than our own. The same process that created our universe can also bring those other possibilities to life, creating an infinity of other universes where everything that can occur, does. The chain of arguments starts from a place I’m familiar with, and I can follow the flourishes that the equations make as they dance down the page toward this particular conclusion, but, while I understand the multiverse as a mathematical construction, I cannot bring myself to believe it will leap out of the realm of theory and find a manifestation in physical reality. How do I pretend I have no problem accepting the fact that infinite copies of me might be parading around in parallel worlds making choices both identical to, and different from, mine?

I am not alone in my