Everybody talks about the multiverse, but nobody does anything about it


Paraphrasing Twain, everybody talks about the multiverse, but nobody does anything about it.

There's a reason. Light, after all, travels only so fast, and right now its reach is about 13.7 billion light years. So there's no way of knowing what might have come before the Big Bang or what lies beyond its accelerating reach.

Inflationary theory explains the universe we see with precision. But CalTech theoretical physicist Sean Carroll, who attended and spoke at IdeaFestival in 2010 on the subject of time, wonders if the addition of string theory to what we know about inflation might yield "pocket universes," each of them ordered by just some of the physical laws made possible by string theory and inflated to 12-dimensional worlds with 7 primary forces, for example, instead of the three dimensions and four forces of energy to which we're accustomed.

In short, string theory predicts that the laws of physics can take on an enormous variety of forms, and inflation can create an infinite number of pocket universes. So the different laws of physics predicted by string theory might not be just hypothetical. They might really be out there somewhere among the countless parts of the multiverse. This is not a situation that cosmologists dreamed up in a flight of fancy; it is something we were led to by trying to solve problems right here in the universe we observe. The question is, now that the multiverse is here, what are we going to do about it?

The answer is not much. Because not all theories can be tested, and the multiverse, while logically consistent, can't yet be tested even if there may be hints in the cosmic microwave background of other possible universes. We are, after all, stuck with the physical laws that obtain in this universe, and the corresponding limits they impose on what we might know.

But that's the part of the scientific fun, according to Carroll. Not all predictions made by science will be accompanied by data; and in this case, the corresponding data may be permanently opaque. Astrophysicist Adam Frank offers a modest counter, wondering whether science can be science without empirical data.

As for what might be done about it, here's a thought: Put in your earbuds at work and listen to the music in the video above. Turn it up. Listen in awe at Lacrimosa, scored to images from the film The Tree of Life. You will be goose-pimpled.