The Age of the Universe

Abstract

ONE of the most important problems of present-day astronomy is that of the age of the universe, and one of the most important pieces of evidence is provided by the orbits of binary stars. The ages which need to be seriously considered fall into two groups; the first is that of the so-called long time scale, which is of the order of 10¹³ years, the time the stars would need to have reached their present condition by annihilation of their substance; the second is that of the short time scale—which is of the order of 10¹⁰ or 10¹¹ years, the time needed for the universe to have expanded from small beginnings to its present size. The motions of the stars ought to provide a means of deciding between the two. For dynamical discussion shows that with the long time scale both the linear motions of single stars and the orbital motions of visual binaries ought to show a reasonably good approximation to equipartition of energy; the short time scale, on the other hand, gives nothing like enough time for such an approximation to be established. Thus if the motions of the stars are found to show any marked approximation to equipartition of energy, it is exceedingly difficult to do other than decide in favour of the long time scale.