Abstract

For Eddington, the word ?ether? was synonymous with de Sitter spacetime, and as such it plays only an episodic role in his later work. Nevertheless, it is good to find out why he held such an opinion, for this leads us into most interesting physical ? and not only historical ? considerations. For this reason, in the present paper we have included the mathematical background necessary to make Eddington's physics clearer. We have also included some of Eddington's epistemological derivations of the ?number of particles in the universe?, not only as a curiosity, but also as a means of understanding the general character of his later work.