On the Emergence of Time in Quantum Gravity

This chapter discusses the idea that the treatment of time in present-day physical theories, general relativity and quantum theory, might be an approximation to a very different treatment in the as yet unknown quantum theory of gravity. It considers the general idea that one theory could be emergent from another, emergence being a relation analogous to, but weaker than, intertheoretic reduction. It also gives a broad description of the search for a quantum theory of gravity and some of its interpretative problems. Thereafter, the discussion focuses on the emergence of time in two specific quantum gravity programmes: quantum geometrodynamics and the Euclidean programme. It also addresses the so-called ‘problem of time’. It is really a cluster of problems; technical and conceptual, arising from how time is treated very differently in general relativity and quantum theory.