Tuesday, June 27, 2006

Tangled in Strings

That theory is worthless. It isn't even wrong! ~Wolfgang Pauli

It seems that more people are starting to doubt whether string theory is really going to lead physics anywhere but in circles.

String theory is based on the concept that matter is made up of vibrating strings, rather than tiny particles. It also requires 11 dimensions to reconcile the five or more variations on the theory. Most of the dimensions are compacted down to subatomic levels so that we aren't aware of them. It's immensely complex, but then quantum mechanics is no walk in the park. It's weird, but so is the concept that time slows as one approaches the speed of light. It's red hot popular these days, but so was the Ptolomaic model of the universe once upon a time.

But, and here's the real rub, it doesn't make new testable predictions. String theory explains certain quantum effects nicely, but it is merely doing it in a different way. There's nothing to suggest it is any more correct than the theories we already have. String theory has been around for over twenty years, yet it has yet to bring anything new to the table. In fact, physicist Lee Smolen is quoted in the article as follows: “When it comes to extending our knowledge of the laws of nature, we have made no real headway [in 30 years] ... It's called hitting the wall."

Instead of providing the Grand Unified Theory that Einstein and others have sought since the 1920's, string theory provides a lovely metaphysical basis for discussing multiple universes. String theory purports to be able to tell us what happened at those infinitesimal moments after the Big Bang when the laws of physics break down. But string theorists also tell us that we need to build accelerators big enough to approximate the energies of those moments; then, they say, string theory will be able to explain what we see.

Well, yes, but it's also possible that string theory won't explain a thing, and some other theory will be required. That's because string theory doesn't really predict what the conditions were like. In fact, it doesn't predict much of anything. As the article says, string theory is more of a framework than a concise set of equations that describes the physical world. Quantum mechanics and Special Relativity are theories; string theory is math.

Worse, the equations that do come out of string theory have multiple solutions, thanks to those 11 dimensions. In the event that it made a prediction that didn't agree with apparent physical reality, it's possible for theorists to claim that the solution is applicable to one of those “other” universes. Predictions that can't be tested are meaningless.

If the only issue was a debate over whether string theory was pseudoscience or not, we'd have an interesting intellectual exercise but no major problem. Unfortunately, string theory has been become the darling of mainstream physics. This means, for example, when a student is looking for thesis material, he or she is going to be pushed toward string theory. The article says, “Virtually every young mathematically inclined particle theorist must sign on to the string agenda to get an academic job.”

This sort of thing is not without precedent. Scientists are no less inclined to go with the flow than anyone else. It is remarkable, though, that the string theory flow has gone on for so long with so little to show for it.

I recently wrote about the GLAST satellite that might provide evidence for the existence of a fourth physical dimension. The upshot of this is that it might provide support for brane theory, a superset of string theory. The problem is that the existence of an extra linear dimension doesn't prove brane theory or string theory. It could, instead, be a missing element of gravity theory, for example. It also could put a dent in the string theorists ideas, because their equations call for 7 physical dimensions to be compacted. While having one of them uncompacted may be nice for the brane guys, it's going to alter all those Calabi-Yau shapes that string theory loves.

As I've said, I respect the minds that have come up with string theory. It is complex and deeply thought out, but that doesn't mean it can't be pseudoscience. But, it's time for some of those great minds to start looking at other paths to follow. Physics has gotten stale, as the article explains, and its best and brightest need to freshen it up.

Einstein spent nearly forty years trying to unify relativity and quantum mechanics. Had he devoted himself to other tasks, who knows what he might have discovered. String theory has tied up physicists for over 20 years now. Who knows what ideas have not been pursued while trying to make sense of its inelegant complexities?

It just might be time to move on.

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