Velocity of Light

Abstract

M. E. J. GHEURY DE BRAY has directed attention to an apparent decrease in the velocity of light¹. I have recently tried to explain this on the basis of the theory of the expanding universe. If the speed of light is a true constant, independent of any variation in our unit of length, then a doubling of the radius of the universe should cause the measured velocity of light to diminish by half. If the radius of the universe doubles every K years, then the velocity of light will be proportional to (1/2)^t where K is the unit of time. Thus, the logarithm of the measured velocity of light must be a linear function of the time. I determined the two constants of such a function from de Bray's data and found that it represented the observations in a satisfactory manner. I then solved this equation for the length of time it would take the velocity to diminish by half. The time is of the order of 60,000 years, which is considerably shorter than the value derived from a study of the recession of the external galaxies². Consequently, this observed variation cannot be explained by the expanding universe theory unless we assume that the rate of expansion is much more rapid in the vicinity of the earth than it is at the distance of the spirals.