String Theory

[MarxSchmarx]

What is your assessment of string theory?

[ÑóẊîöʼn]

Where's the "unproven hypothesis" option? String theory is a beautiful, self-consistent theory which may or may not match up to reality. The problem is that the usual way of testing such theories - smashing particles together in an accelerator - requires more energy than we can currently produce. But there may be other ways of proving it or getting indirect confirmation of the theory.

[mikelepore]

After almost a hundred years they still can't unite relativity and quantum mechanics by demonstrating that both of them are special cases of something more general. Einstein continued working on that problem on the day that he died. It's inevitable that they'll keep trying. It's okay to propose an answer that can't be tested, because maybe someday it will be testable. However, for the time being, people shouldn't speak of it the solution as factual. This is a bad habit. Many people speak of gravitons as factual, as well as the Higgs boson, reversible time, multiverses, etc., although all of these are only hypothetical and undemonstrated. Likewise, the claims of string theory, such as space having so many more dimensions that we can't see, shouldn't be spoken of as factual. But there are always some some popular science paperback authors who will be careless.

[ÑóẊîöʼn]

After almost a hundred years they still can't unite relativity and quantum mechanics by demonstrating that both of them are special cases of something more general. Einstein continued working on that problem on the day that he died. It's inevitable that they'll keep trying.

Well, you must remember it took nearly 300 years for us to discover that Newton's Theory of Gravitation were merely a special case of a more general theory - that of relativity. So I don't think the case for unifying relativity and quantum mechanics should be thrown out just yet.

[MarxSchmarx]

It's okay to propose an answer that can't be tested, because maybe someday it will be testable.


The problem is that the usual way of testing such theories - smashing particles together in an accelerator - requires more energy than we can currently produce. But there may be other ways of proving it or getting indirect confirmation of the theory.

Indeed, although I was under the impression that some conclusions of string theory are, even in principle, essentially untestable.Or is it really just a problem of inadequate resources?

[ÑóẊîöʼn]

Indeed, although I was under the impression that some conclusions of string theory are, even in principle, essentially untestable.Or is it really just a problem of inadequate resources?

The problem is simply energy. String theory operates at very small scales, and the smaller the scale the more energy one needs to investigate it. We currently cannot build accelerators that can produce the required energies, and hence investigate the required scales.

But! There is more than one way of confirming a hypothesis. Grand Unified Theories, like String Theory, can only be investigated at energies that exceed current maximums for accelerator design. But Grand Unified Theories made an observational prediction - the decay of the proton. Now, GUT predicted that protons would have a half-life of about 32 trillion years if I remember correctly. Now, clearly it is impractical to sit around for that long waiting for a single proton to decay. But observe billions of trillions of protons, the amount of protons in a massive tank of water buried deep underground to shield it from cosmic rays, and your highly sensitive detectors might pick up, on average, about one proton decaying per year, or at least that was the prediction of Grand Unified Theories.

A similar approach may be taken with String Theory - although we cannot directly observe strings through our particle accelerators, we can still infer their existance by confirming predictions that the theory makes.