The discovery that past events were after all persistent, and accessible, was of course for the Fifth Men a source of deep joy; but also it caused them a new distress. While the past was thought of as a mere gulf of nonexistence, the inconceivably great pain, misery, baseness, that had fallen into that gulf, could be dismissed as done with; and the will could be concentrated wholly on preventing such horrors from occurring in the future. But now, along with past joy, past distress was found to be everlasting. And those who, in the course of their voyaging in the past, encountered regions of eternal agony, came back distraught. It was easy to remind these harrowed explorers that if pain was eternal, so also was joy. Those who had endured travel in the tragic past were apt to dismiss such assurances with contempt, affirming that all the delights of the whole population of time could not compensate for the agony of one tortured individual. And anyhow, they declared, it was obvious that there had been no preponderance of joy over pain. Indeed, save in the modern age, pain had been overwhelmingly in excess.
So seriously did these convictions prey upon the minds of the Fifth Men, that in spite of their own almost perfect social order, in which suffering had actually to be sought out as a tonic, they fell into despair. At all times, in all pursuits, the presence of the tragic past haunted them, poisoning their lives, sapping their strength. Lovers were ashamed of the delight in one another. As in the far-off days of sexual taboo, guilt crept between them, and held their spirits apart even while their bodies were united.
III
Voyaging in Space
It was while they were struggling in the grip of this vast social melancholy, and anxiously craving some new vision by which to reinterpret or transcend the agony of the past, that the Fifth Men were confronted with a most unexpected physical crisis. It was discovered that something queer was happening to the moon; in fact, that the orbit of the satellite was narrowing in upon the earth in a manner contrary to all the calculations of the scientists.
The Fifth Men had long ago fashioned for themselves an all-embracing and minutely coherent system of natural sciences, every factor in which had been put to the test a thousand times and had never been shaken. Imagine, then, their bewilderment at this extraordinary discovery. In ages when science was still fragmentary, a subversive discovery entailed merely a reorganization of some one department of science; but by now, such was the coherence of knowledge, that any minute discrepancy of fact and theory must throw man into a state of complete intellectual vertigo.
The evolution of the lunar orbit had, of course, been studied from time immemorial. Even the First Men had learned that the moon must first withdraw from and subsequently once more approach the earth, till it should reach a critical proximity and begin to break up into a swarm of fragments like the rings of Saturn. This view had been very thoroughly confirmed by the Fifth Men themselves. The satellite should have continued to withdraw for yet many hundreds of millions of years; but in fact it was now observed that not only had the withdrawal ceased, but a comparatively rapid approach had begun.
Observations and calculations were repeated, and ingenious theoretical explanations were suggested; but the truth remained completely hidden. It was left to a future and more brilliant species to discover the connection between a planet’s gravitation and its cultural development. Meanwhile, the Fifth Men knew only that the distance between the earth and the moon was becoming smaller with ever-increasing rapidity.
This discovery was a tonic to a melancholy race. Men turned from the tragic past to the bewildering present and the uncertain future.
For it was evident that, if the present acceleration of approach were to be maintained, the moon would enter the critical zone and disintegrate in less than ten million years; and, further, that the fragments would not maintain themselves as a ring, but would soon crash upon the earth. Heat generated by their impact would make the surface of the earth impossible as the home of life. A short-lived and shortsighted species might well have considered ten million years as equivalent to eternity. Not so the Fifth Men. Thinking primarily in terms of the race, they recognized at once that their whole social policy must now be dominated by this future catastrophe. Some there were indeed who at first refused to take the matter seriously, saying that there was no reason to believe that the moon’s odd behaviour would continue indefinitely. But as the years advanced, this view became increasingly improbable. Some of those who had spent much of their lives in exploration of the past now sought to explore the future also, hoping to prove that human civilization would always be discoverable on the earth in no matter how remote a future. But the attempt to unveil the future by direct inspection failed completely. It was surmised, erroneously, that future events, unlike past events, must be strictly nonexistent until their creation by the advancing present.
Clearly humanity must leave its native planet. Research was therefore concentrated on the possibility of flight through empty space, and the suitability of neighbouring worlds. The only alternatives were Mars and Venus. The former was by now without water and without atmosphere. The latter had a dense moist atmosphere, but one which lacked oxygen. The surface of Venus, moreover, was known to be almost completely covered with a shallow ocean. Further the
