I think it’s interesting how science progresses from the simple to complex. On one hand, a complexity of apparently different phenomena can be unified by an underlying principle. On the other hand, theories usually start simple, then exceptions are found, and the theory must have rules added, increasing complexity. Cosmology seems like that. It makes me wonder why scientists think they are right when they start with a simple theory. You might as well start by saying, I’m going to assume such and such in order to simplify the analysis, but really the universe is probably more complicated. One of the biggest examples to me in cosmology is the Cosmological Principle, that the properties of the universe are the same everywhere; we are not in a unique location. More, though, it’s not just the principles that are the same everywhere, but the properties, like density and temperature. Why should it be that way? We see lots of examples, like different rock formations in geology. It’s not just a uniformly stirred pot of cream of wheat.
The multiverse example takes this to the other extreme. Maybe everything is different everywhere. :-) I’m reading Greene’s latest book, where he develops these arguments. Personally, I’m not happy with it. It borders on, dare I say, philosophy! :-) Sure, I like philosophy, but I don’t like to mix it with science. :-) Okay, I’m being a little facetious here. But, seriously, to me it’s like the mathematical concept of infinity, making it too easy to ignore the details. Divide any number by infinity and you can throw the result away, it’s zero. I don’t believe in infinity; it’s a matter of faith to me. I don’t think the universe is infinite, and neither is anything else. It has no practical value. The multiverse extreme is that one can say that there’s a universe out there with the exact copies of you and I in it, because with an infinite number, you can do anything you want. That’s too intellectually unbounded. In the words of my college roommate of many years, whom I studies physics with, it is “mind masterbation”.
I do think we are in another golden age of cosmology. There are many interesting ideas and developments. We are able to observe the entire, er, well, observable universe. :-) I support the weak anthropic principle, not the strong one. Arguments and intellectual struggles over why the properties of the universe are so finely tuned for us are specious. We’re here because the universe supports life. Nothing more special than that.
The multiverse could be possible. No reason to assume it isn’t. But it could also be an intellectual cop-out, avoiding the anthropic problem by creating all the possible universes. It’s simpler to just accept the universe in the current state and go on to try to understand how it works, instead of agonizing over why we are here. It’s like some sort of scientific political correctness: we can’t consider ourselves and our universe as special, so we hypothesize that there are all the other universes in which life cannot exist, or different forms of life. Then, we don’t have to be self-conscious about being who we are.
