Removing zero from the universe might seem like a drastic step, but strings are much more tractable than dots; by eliminating zero, string theory smooths out the discontinuous, particle-like nature of quantum mechanics and mends the gashes torn in general relativity by black holes. With these problems patched over, the two theories are no longer incompatible. Physicists began to think that string theory would unify quantum mechanics with relativity; they believed that it would lead to the theory of quantum gravity-the Theory of Everything that explains every phenomenon in the universe. However, string theory had some problems. For one thing, it required 10 dimensions to work.