  Although general relativity is a predictively successful theory, it treats
matter as classical rather than as quantum. For this reason, it will have to be
replaced by a more fundamental quantum theory of gravity. Attempts to formulate
a quantum theory of gravity suggest that such a theory may have radical
consequences for the nature, and indeed the fate, of spacetime. The present
article articulates what this problem of spacetime is and traces it through
three approaches to quantum gravity taking general relativity as their vantage
point: semi-classical gravity, causal set theory, and loop quantum gravity.
