As of 2011, no sane person seriously doubts that string theory is the right framework that describes the Universe around us. However, there remain uncertainties about the inner structure of the relevant string vacuum. String/M-theory possesses many four-dimensional solutions that qualitatively resemble our world.What he is saying here is that string theory postulates an 11-dimensional space with zillions of possibilities for the vacuum, and no one has found one that matches our 4-dimensional spacetime vacuum. Some of the models have some qualitative resemblance to the vacuum, but that's all. The vacuum is what used to be called the aether.
Those solutions are connected on the configuration space of the theory and may be related by various dualities. However, the known stringy descriptions that are semi-realistic and weakly coupled may still be divided into several major categories:
Weakly coupled heterotic E8 x E8 strings
Heterotic M-theory in 11 dimensions; the strongly coupled limit of (1) with two end-of-the-world domain walls
M-theory on singular 7-dimensional G2-holonomy manifolds
Type IIA orbifold/orientifold braneworlds
F-theory on local singularities
A reader named Daniel responds:
I imagine that is a tongue-in-cheek comment, written with a smirk on your face. Am I right?Motl responds:
From your own blog (Gibbs guest post), about half of people surveyed gave string theory a less than 10% chance of being correct.
No, there has been no toungue-in-cheek comment in my text, except for the lolcat. It's a totally serious technical text, unlike your comment.Motl posts some good stuff sometimes, but he is off the rails. String theory has no chance of being correct.
Well, I have no doubt that at least 90% of people don't have any clue about physics - I actually think that the number is above 99%. People are dumb as a doorknob, indeed. ...
I've banned Daniel after his third obnoxious comment. Just to make sure, this thread is dedicated to low-energy models of string theory.