Somebody has called astronomy the Futile Science, and I am not at all sure that the epithet is wholly undeserved. What do the stars matter to us? There was a time when they were believed to have an influence on human affairs, particularly those of kings and emperors. To-day they are insignificant specks at an immense distance from us, a distance so great that if they all were utterly annihilated neither we nor our remotest descendants should experience the smallest material effect. The only assignable value of the stars to us, beyond the general enlargement of our mental horizon, is that they serve as an accurate measure of time. But even that use is now almost superfluous, since other absolute standards of time have become available, such as the rates of disintegration of the radio-active elements. How, then, can I account for the fact that there is a perpetual fascination about “the heavens,” that books are constantly being written about them, societies founded to study them, and vast observatories built to watch them? It cannot be simply the thirst for knowledge. Knowledge in the abstract has but few devotees. For every one person who wants the Truth at all costs there are a thousand who want an Illusion at all costs, even at the cost of mental balance. Let a man go about proclaiming truths ascertained by research and experiment, and he will be considered a bore by all except a few specialists. But let him boldly assert an absurdity or a paradox, and he will obtain millions of adherents, all animated by the Will to Believe. And the more absurd his assertions, the more self-assured and fanatical will be his followers. No, the popular interest in astronomy is not due to a thirst for accurate information. It is due to a vestige of the old astrological belief in the significance of the constellations. We still try to “read our fate in the stars.” They are of interest to us for what they can tell us of the future, proximate or remote. We search the heavens for an answer to the question “Whither?”――_Quo vadimus?_ In trying to predict the fate of the human race we must begin by gauging the chances of permanence possessed by our habitable globe. Its probable age has been put at a hundred million years. Predictions as to when it will cease to be habitable vary enormously, but the latest figures go into many millions of years, and the discovery of radio-activity has had the effect of greatly postponing the general freezing up of our planet. Our earthly habitation, then, seems assured for many millions of years. But millions of years are, after all, but relative, and they vanish before the vast age of the stellar universe[1] and the enormous vistas of time yet to come. [1] Dr. Jeans, on very modern data, puts this age at seven million million years.