Ask a String Theorist! Or an Atomic Physicist.

Over at Uncertain Principles, Chad Orzel is on vacation and has handed the keys to the blog over to Aaron Bergman and Nathan (last name mysterious), specialists in string theory and atomic physics, respectively. Good luck to them as they experience what the blogosphere is like from the other side. Aaron has begun to talk a little about the multiverse -- here, here. He has thereby earned grumpy mutterings, rolled eyes, and "help" from some sensible physicists, some crackpots, some curmudgeons, his guest co-blogger, and even himself. I don't quite understand what all the angst is about. (Actually I do understand, of course; this is one of those times when you adopt a rhetorical stance of pretending not to understand some alternative position in order to emphasize how unimpeachably correct your own position is.) People are very welcome to disagree with the presuppositions or conclusions of anthropic reasoning; that's just how science goes, and is perfectly healthy. But in addition to the substantive disagreements, there's a widespread urge to express dismay that it's even being talked about all the time. Now, that urge can't be sensibly directed toward the actual research being done, because on that score multiverse-type stuff is a tiny percentage of all the work that goes on. Peek at any day's worth of abstracts on hep-th, hep-ph, gr-qc, or astro-ph; you might find something anthropic here or there if you're lucky, but it's a tiny minority. This stuff is not dominating science, or physics, or theoretical physics, or high-energy theory, or even string theory. No, the complaint is that considerations of parts of the universe that we can't possibly see tend to receive an inordinate amount of attention in public discussions -- on blogs, in books, in magazines and newspapers. Which is completely true, as a factual statement. At the risk of revealing a trade secret: the public discussion of different avenues of scientific research does not faithfully reflect the amount of research effort being put into those questions. Eek! I'd be willing to bet that it has always been like that. And yet, science marches on. You may ask why something like the multiverse exerts such an outsized pull on the public imagination. So let me break it down for you here: it's fun. People like talking about other universes, and whether we could be living in a simulation, and what happened before the Big Bang. For one thing, anyone can dive in; you don't need to be an expert on twistor space, or two-loop counterterms, or BRST invariance in order to pontificate about the conditions under which life could exist if the laws of physics were very different. (Comments from people who are more informed and thoughtful about the subject will generally be more useful, but anyone can say something.) For another, it's just cool to contemplate these way-out possibilities. The lure of crazy ideas is what draws a lot of people to science in the first place. And that's ... okay, as Stuart Smalley would remind us. It would be very bad indeed if unmoored philosophizing about other universes became the dominant paradigm in science, or any subset thereof, but there's zero danger of that. Really. But there's no reason why people can't have fun contemplating some of the more provocative and accessible ideas out there. On this very blog we will occasionally write lengthy discourses on some piece of technical work related to observations -- and not get anywhere near the number of comments that a two-minute toss-off about the anthropic principle gets. And yet, science has not ground to a halt. I think the enterprise is sufficiently healthy to survive a few more posts about the multiverse.