hi i have been reading in many books that the unification of quantum mechanics and general relativty is not possible. but why??? it is clear that we cannot use a certain theory for certain phenomen in the universe and other theory for the rest phenomenas of the world. at singularity we have to consider both quantum mechanics and relativity.but we are no ablr to unify this two theory.but why? why is it so that we cannot prive both the theories together at the same time???