Paper
A Newtonian Expanding Universe
Published Sep 1, 2000 · E. A. Milne
General Relativity and Gravitation
223
Citations
5
Influential Citations
Abstract
1. The phenomenon of the expansion of the universe has usually been discussed by students of relativity by means of the concept of ‘expanding space’. This concept, though mathematically significant, has by itself no physical content; it is merely the choice of a particular mathematical apparatus for describing and analysing phenomena. An alternative procedure is to choose a static space, as in ordinary physics, and analyse the expansion-phenomenon as actual motions in this space. Moving particles in a static space will give the same observable phenomena as stationary particles in ‘expanding’ space. In each case the space is a construct built up by the mathematician out of observations that could in principle be made; it is built up around the matter in motion according to certain rules. The formulation of the relevant laws of nature depends on the rules adopted, and the laws will be quite different if different rules are adopted, as I have elsewhere† explained. The alternative procedures have been tersely described in a recent paper by S. R. Milner.‡ He explained that we can either modify our geometry in order to retain d ∫ ds c 0 as the paths of free particles, or retain Euclidean geometry and Minkowski space-time and modify the variational principle by weighting the elements of path ds with appropriate invariant weighting factors. Einstein’s general relativity adopts the first procedure; in my recent treatment of the cosmological problem I adopted the second procedure. In neither case has the space constructed any physical significance—no content attaches to the phrase ‘the space of nature’—but the second procedure has the advantage that it employs the space commonly used in physics. The equations of motion I obtained for free particles moving in the presence of a certain distribution of matter in motion were derived by the straightforward method of making
Highly CitedThe expansion of the universe can be analyzed as actual motions in a static space, providing the same observable phenomena as in 'expanding' space, with no physical significance to the concept of 'expanding space'.
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