Bibliography ivBefore we speculate on what kind of new physics we expect, let us take a step back and ask ourselves why we need a theory of quantum gravity to begin with. Independently quantum field theory and general relativity have been highly successful in explaining physical phenomena, and at first sight they seem to work at the complete opposites of the spectrum: the former concerns itself with physics 12 Recall that the Type IIA string coupling is fixed in terms of the radius of the M-theory circle as g IIA s