Introduction

Summary

One of the purposes of this conference is consideration of the historical background to the topics under discussion, so I shall open with a historical introduction to ‘quantum gravity’.

Once he completed work on the general theory of relativity at the end of 1915, Einstein began to concern himself with its implications for microphysics. In his first (1916) paper on gravitational radiation, Einstein argued that quantum effects must modify the general theory:

Nevertheless, due to the inneratomic movement of electrons, atoms would have to radiate not only electromagnetic but also gravitational energy, if only in tiny amounts. As this is hardly true in nature, it appears that quantum theory would have to modify not only Maxwellian electrodynamics, but also the new theory of gravitation.

(p. 209)

He reiterated this conclusion in his second (1918) paper:

As already emphasized in my previous paper, the final result of this argument, which demands a [gravitational] energy loss by a body due to its thermal agitation, must arouse doubts about the universal validity of the theory. It appears that a fully developed quantum theory must also bring about a modification of the theory of gravitation.

(P. 164)