What do we know about Quantum Gravity?
Precious little: We don’t even know if gravity is quantized in any way (but we strongly suspect that it is). We can say a few things about what the theory will look like, assuming that it is quantized: Gravity would be vectored by a particle called the graviton, just as electromagnetism is by the photon. The graviton would be massless and chargeless, and it would have a spin of 2, unlike most elementary particles, which have a spin of 1/2 or 1. Like all massless particles, it would travel at the speed of light, and it would couple weakly to all other particles, including itself. That’s about as far as we can go, so far.
Superstring theory and its decendant m-theory currently seem to offer the best hope for a theory of quantum gravity, and can make a few other predictions, but different flavors of the theory make different predictions, and there’s no way to verify them yet.
I read an article in Nature earlier this year claiming that it should be possible to make measurements with LIGO to disprove some of these conflicting theories. Damned if I can remember what they were planning to measure, though.
Were they trying to measure gravity waves by any chance? With one of those huge perpendicular laser arrays?
that’s the one.
http://antwrp.gsfc.nasa.gov/apod/ap001030.html