Sunday, July 15, 2007

More optimism for String Theory

After watching this week's episode of Science Saturday on Bloggingheads, I've decided to give String theory some credit. This week they had George Johnson with Sean Carroll, who writes on a very popular blog known as Cosmic Variance. In this week's episode, Sean Carroll does a pretty good job at addressing some of the arguments against String Theory. Including the arguments that String theory makes no predictions, and the near-monopoly String theory holds on resources such as faculty positions and research grants. (Note: Some material may have also been used from Carroll's critique of The Trouble with Physics, or Joe Polchinski's review of the two anti-string-theory books.)

Apparently, the reason string theorists have been having trouble making predictions because string theory is literally a "twenty-first century theory revealed in the twentieth century". As most people who studied the history of String theory know, String theory wasn't the work of long, gradual work to derive, but rather a "Eureka"-type birth. Instead of dredging through years of trial and error, physicists managed to shoot up to it. Now, the problem is that while our theory is advanced and futuristic, our technology is still stuck in the late-twentieth /early-twenty-first century. Until our technology advances enough, the only thing String theorists have are hard mathematical models and working further on understanding String theory. I buy this. Although String theorists may not exactly be making technologically feasible predictions yet, as Smolin admits, "No one disputes that a lot of good mathematics has come out of string theory and that our understanding of some gauge theories has been deepened" (pg 177). So, I guess that while String theorists churn out useful work and are still working on and expanding String theory, we could spare them the absolute need for experimental evidence. The way I see it, as long as String theory is still being studied, there's the possibility of someone finding some technologically-feasible, if indirect, method of confirming or refuting String theory.

As for the monopoly on resources, Sean Carroll's position is (I believe) that's a pity. But unfortunately, university politics make it difficult for non-string-theorists to find a position in theoretical physics. It would be ideal for there to be a diversity of theories that are worked on, but that's not the way things go. University administrators do not want to take a chance of hiring unorthodox or different people and are very risk-averse when it comes to this. However, Carroll admits that if an alternative theory were to be as promising as String theory, this would probably change; however, he believes that the theory Smolin advances, loop quantum gravity, does not offer anything String theory already offers. Until another theory steps up to explain more than String Theory does, non-string-theorists would have to put up with their minority position. I hope I summarized Carroll's position accurately.

Now, the thing that really bothers me about String theory was brought up by Peter Woit. It's the gigantic zoo of elementary particles which were predicted but not observed by String theory. Namely that String theory (if I remember) needs a property called supersymmetry, which states that for every boson there's a fermion and for every fermion there's a boson. This basically doubles the size of the number of elementary particles. Now, I may be a little behind on the times, but the explanation I heard was that there was a symmetry-breaking which caused the super-particles to be much more massive and thus, undetectable by our current accelerators. Now that, I don't buy. It seems a bit too convenient. If anyone knows of a better explanation for this problem, I'd gladly hear it.

No comments: