Thursday, September 2, 2010

Tied Up with Strings

Or, Why I Don't Believe in String Theory.

String theory has a large body of ardent fans, both physicists and laypeople. I am not one of them.

"But string theory is so beautiful!"
a) Beauty does not mean truth. I can think of half-a-dozen symmetries at least as beautiful as Gell-Mann's Eightfold Way. So why is he a world-famous physicist and I'm an insignificant blogger? Because his version is not only beautiful, it works. Yes, most good theories are beautiful, but not every beautiful theory is a good theory.
b) Beauty is in the eye of the beholder. I actually don't think string theory is that beautiful! People complain about the ugliness of the Standard Model's eighteen adjustable constants; well, I find string theory's six (or seven, in M-theory) extra dimensions just as ugly and wasteful.

"It's going to be a unique theory of nature."
"Going to" is the operative word here. Perhaps someday, if we can ever get M-theory written down (see next point), it will be a unique theory of nature. But then it won't be string theory, it will be some other theory. There are several thousand, possibly several million, different string theories, and our universe could have been any one of those. (Of course, I believe that God could definitely control the string theory our universe is described by; however, I don't think he would have designed our universe so messily.)

"But M-theory is a unique theory of nature!"
And so it may be, but it doesn't do anyone any good. We can't even write down all of M-theory's solutions (string theories), and we can barely prove that M-theory exists! Even regular string theory is pretty useless: the theorists can't calculate with it and the experimentalists can't test it, so what are we to do with it?

"Well, anyway, it's the only game in town for quantum gravity."
No way. Loop quantum gravity! Noncommutative geometry! Doubly special relativity (in which lightspeed depends on the photon's energy)! Maybe none of these are any good. In that case, let's invent some more!

So my words to the string theorists: By all means, keep working on string theory; it's a fascinating structure with interesting symmetries. Just don't call it physics. Call it pure math.

Physics forever,

P.S. If you enjoyed this post, check out Lee Smolin's books The Trouble with Physics and Three Roads to Quantum Gravity. He's a skeptic, but a very refreshing kind: he's as skeptical of established science as he is of religion.


  1. Interesting post! I have to say though, that I am a "fan" of string theory, but only in that I find it to be fascinating and I love to study it (and all advances in the theory thereof) but I'm definitely not a believer in string theory.

    The main reason I'd have to say why people accept the theory is because it would explain so many things (especially from an atheistic worldview) very well. It gives people an explanation why all these constants are set perfectly for our universe, how quantum mechanics and special relativity relate, and even what caused the big bang.

    And by the way, when you referred to those "eighteen adjustable constants," where you talking about the constants such as the strength of the weak force and the cosmological constant that HAVE to be precisely tuned in order for the universe to exist? I believe the current count for those constants is over 35 now.

  2. Wow, 35? That's a lot!
    Actually, by the "eighteen adjustable constants" I was referring to the particle masses, etc., that the Standard Model doesn't predict, but that have to be determined by experiment -- many physicists think that a final theory (if we ever get one) must predict EVERY observation, and not have to have anything "fed into" it, so to speak. Personally, this doesn't worry me much, as I don't think we can ever find the final theory on earth; maybe when we get to heaven we will be allowed to discover it as an act of worship.

    Sorry about the tangents.