Its only since the middle 1980s that real progress began to be made on unifying relativity and quantum theory. The turning point was the invention of not one but two approaches: loop quantum gravity and string theory. Since then, we have been making steady progress on both of these approaches. In each case, we are able to do calculations that predict surprising new phenomena. Still, we are not done. Neither is yet in final form; there are still things to understand. But the really important news is that there is now a real chance of doing experiments that will test the new predictions of these theories.This is important, because were in the uncomfortable situation of having two well-developed candidates for the quantum theory of gravity. We need to reduce these to one theory. We can do this either by finding that one is wrong and the other right, or by finding that the two theories can themselves be unified.
Its only since the middle 1980s that real progress began to be made on unifying relativity and quantum theory. The turning point was the invention of not one but two approaches: loop quantum gravity and string theory. Since then, we have been making stea
