Nature 169, 702 (26 April 1952); doi:10.1038/169702b0

Is there an Æther?

P. A. M. DIRAC

St. John's College, Cambridge. Feb. 16.

INFELD has shown how the field equations of my new electrodynamics can be written so as not to require an æther. This is not sufficient to make a complete dynamical theory. It is necessary to set up an action principle and to get a Hamiltonian formulation of the equations suitable for quantization purposes, and for this the æther velocity is required.