November 3, 2011
Is your theory that if one universe can be generated from simple algorithms, all universes can and have been? Or would be?
The only thing we can meaningfully talk about in science, as far as empirical science is concerned, is our actual universe: there’s only one. Anything else we say about it is a purely theoretical thing. Now, the question would be—we might then say, gosh, what must be happening is that somewhere out there, not in any way that we can ever be aware of, but somewhere out there every possible universe must be going on. That might be a possible theory. It’s not a testable theory. There’s no way we could test that theory because we’re stuck in our universe. And if that theory was correct, then the overwhelming likelihood is that the rules for our universe are very, very complicated, because if there are gazillions of universes out there and we’re just in a random universe, the randomly chosen universe will be one with very complicated rules. It’s like, each universe could be labeled by an integer. Well, there are an infinite number of integers. If we’re a random integer, it’s going to be a big integer. It’s not going to be ‘8’ or something. There’s no reason for it to be 8 if it’s just randomly chosen.
Now, I have a sneaking suspicion that when we really understand what’s going on, that—typically, in the history of science, those kinds of metaphysical questions have crumbled because they weren’t quite the right question, or things worked in a way that sort of worked around the question rather than having to centrally ask the question. My sneaking suspicion is that what we’ll discover is that any one of a large collection of possible rules for the universe is equivalent in generating our universe. I don’t know if I’m correct. That’s just a guess. Something bizarre like that will happen, I suspect, to make that question of “Why this universe and not another?” not really be a meaningful question. It’s a situation that’s like—in a lot of cases in the history of science, people figure out a lot about how stuff works and then they say, “Well, why was it set up this way and not another?” And Newton was famous for saying, “Once the planets are originally set up, then [his] laws of motion can figure out what can happen. But how the planets were originally set up, well, that’s not a question we can answer in science”. Now, 300 years later, we know a lot about how the planets were originally set up.
One of the nicer things I always like about philosophers at that time, like Locke and people like that, would say: the fact that the number of planets is nine, eight, whatever it was in their day—that number is not a necessary truth about our universe. That number is somehow an arbitrary number. That was what they thought. They didn’t think that number—just like I’m saying if our universe turns out to be universe number 1,005 or something, that that’s just an arbitrary number. In their day, they couldn’t imagine that you could compute the number would be seven or something. Now, in our day we know that if we have a star about the size of the sun and you have a solar system and it’s about the age of our solar system, we know roughly how many planets there will be typically in such a thing. We can compute it. But in their day, that was an inconceivable idea, to be able to compute that. And I think that—I think we’re at too early a stage. It feels a bit wrong to say, gosh, our universe must be one of the simple ones, so let’s go out and search for it—because it seems like a sort of anti-Copernican kind of claim. It seems like a very arrogant claim about us and our universe. Why should we be one of the simple ones, not one of the ones that’s incredibly complicated? My guess is, that question will resolve itself in some way that isn’t quite centrally that question, but I don’t yet know what that is.