How Far Are We from the Quantum Theory of Gravity?
  I give a pedagogical explanation of what it is about quantization that makes
general relativity go from being a nearly perfect classical theory to a very
problematic quantum one. I also explain why some quantization of gravity is
unavoidable, why quantum field theories have divergences, why the divergences
of quantum general relativity are worse than those of the other forces, what
physicists think this means and what they might do with a consistent theory of
quantum gravity if they had one. Finally, I discuss the quantum gravitational
data that have recently become available from cosmology.
