The Expanding Universe

Abstract

SIR ARTHUR EDDINGTON'S skill as a writer is well known to-day. He makes effective use of it in this brilliant exposition of the theory of the structure of the universe from the point of view of the theory of general relativity. The observational problem to be discussed is becoming familiar to all scientific workers. Our galaxy is apparently surrounded by a cloud of other galaxies, the spiral nebulae, which appear to be evenly scattered throughout space. This cloud, moreover, does not seem to have a boundary. The spectral lines of the light emitted by these nebulse exhibit a shift towards the red end of the spectrum which increases proportionately to the distance of the nebula concerned. By means of the Doppler effect in the wave theory of light, this observed red-shift is interpreted as a velocity of recession. The speeds so found are enormous: the most recent determination is 24,000 km./sec. for a faint cluster of nebulae in the constellation Gemini. With this interpretation of the red-shift, we are evidently dealing with a material system which is certainly expanding and is also boundless, The Expanding Universe. By Sir Arthur Eddington. Pp. ix + 128 + 2 plates. (Cambridge: At the University Press, 1933.) 3s. 6d. net.