The Problem of Quantum Gravity: From Feelings to Phenomena

Abstract

This chapter provides a simple, schematic introduction to the problem of quantum gravity. The problem of quantum gravity spent much of its earliest history at the mercy of wider changes with respect to the ingredient theories, general relativity and quantum theory. Even once those theories settled down, quantum gravity remained firmly detached from experiments. This situation has only recently changed and promises to offer new phenomena to test proposed solutions to the problem which will enable us to make firmer statements about the more physical implications of these proposed solutions. However, we see that we may still face a problem of polysemicity stemming from the very differing interpretations and formulations that the ingredient theories allow, as well as differing motivations for pursuing quantum gravity.