A basic consequence of string theory. Look it up.
For one thing, I said "what seems the most likely scenario", so don't get anal about 'absolute proof'.
As for "c'mon, there's got to be more evidence to start stating things" and "nowhere near proven"; you consider a near-complete theoretic framework, being worked on by thousands of the best minds around the world, with tens of thousands of academic publications to be "not worth mentioning?"
We know that the two theories we have to describe the 4-dimensional universe we live in are incompatible.
We know that we need to account for higher-dimensions in order to couple mavity with the other three basic forces.
We know that to obtain direct observations of the behavior of higher dimensions, in order to PROVE the theoretical framework correct, will take more energy than we can currently generate. There is no proof because we do not yet have the tools powerful enough and sensitive enough to probe the small lengthscales and high-energies required. This is the whole reason that we build devices such as the LHC.
Just because you don't understand something, or don't want to believe it, doesn't mean you should become a luddite.
Stop criticising things you don't understand, and try to find me even the basics of just one theory of quantum mavity which DOESN'T have mavity existing in higher dimensions. If you're convinced it does not exist, and that you know better than the entire theoretical physics comuinity, then go prove it. Otherwise shut up.
