IIRC “Super-string theory” has lost a lot of it’s luster over the last 10 years of so as a workable base level paradigm for a “theory of everything”. What are the latest and greatest theories for integrating all the various forces in nature?
M-Theory, or M(atrix)-Theory, appears to be leading candidate for superstring theory, although it has its inherent problems. I don’t know much about this theory, but there’s a TV documentary about M-Theory called “Parallel Universes” which will be on the Science Channel tomorrow (11/9).
Garrett Lisi’s Exceptionally Simple Theory of Everything is one of the most recent theories to be proposed regarding the TOE. Unlike other string theories, his “E8 Theory” (or, as I call it, “Surfer Dude Theory”) actually does have predictive value, and it’s gotten the attention (both positive and negative) of theoretical physicists worldwide. I’m more of a “fanboy” when it comes to theoretical physics, but I suspect this guy might be onto something major. CERN’s Large Hadron Collider, once it powers up, will show us more – assuming it doesn’t create a singularity which swallows the entire Universe whole.
The other biggie is loop quantum gravity.
But string theory is not at all ruled out by anything we know. It’s just more complicated than people hoped.
The biggest problem with the String Model and its descendants is that it’s not really falsifiable, at least not in a practical sense. It’s got a ton of free parameters which can take a wide range of values, leaving you in effect about a googol googol different models, all of them theoretically consistent. Even if you do manage to devise some clever and delicate experiment to rule out some of them, there’s still myriad more to step into the gap. And even if you did manage to confirm something predicted by some string models, it wouldn’t give you any heads-up on predicting anything else, because there are so many different variants of the model that are consistent with your experiment, and they might make different predictions for the other things.
How about we call it