However it may be, his gibes fell, if not on hostile, at least on deaf ears, and he remained an exception; for whether they thought the influence benign or unbenign, almost all men through all the centuries till the last two or three thought it supernatural.
Then, with Bayle the great name of the change, a great change began. Comets were still thought to produce effects on the earth, and these effects were still thought to be chiefly baleful; the change was that they came to be regarded as natural and not supernatural effects, part of the foreordained order of physical things. Comets tampered with the atmosphere; caused curious dry fogs, or over-great heat, or divers sicknesses. The Plague of London in 1665, as the sleeping-sickness epidemic in Japan in our own day, was put down to cometary gases. Thou shalt die in a polluted land.
The utter danger, that a comet would accomplish the end of the whole earth, was not removed; but by honest collision, not by magic.
The nineteenth century’s attitude differed from that of all its predecessors. A comet meant nothing, favourable or unfavourable; it could produce no supernatural results or natural ones either. A world so perfect and so progressive could not be destined for such harm—Providence would not be so foolish—while of goodness it had enough, without help from the heavens. Human reason and human records alike controverted the cometic claims, and however eager to smile at their forebears of the nineteenth, twentieth century students who toil through the long Chinese records or through Pingré must admit that most of the visitors therein so monotonously registered did little to the earth that was worth doing, either good or bad.
The twentieth century began to waver. If “somehow good” lived on, it was flickeringly. Magic was in the air again, and catastrophe. Also new facts. It was demonstrated, for instance, that by means of the shooting stars showered down by comets, or the tenuous matter shed from their tails, new supplies of carbon, the stuff of life, were given to us. Life was thus renewed on the earth, declared optimists. Thus it was kept going or set going everywhere, added enthusiasts; comets were peripatetic creators, Jehovahs itinerant, beneficent bodies bearing carbon and with it organic existence from star to star, in vital permutation, high cosmic interchange, eternal xenogamy of worlds.
Pessimists, on the other hand, though with many a reserve and proviso to prevent themselves looking ridiculous, are returning to a catastrophic view; of a comet not as herald or harbinger of doom—no worthy one announced Armageddon, the 1914 skies spake peace—but as its actual agent. They think that one might strike the earth, or almost; and that if it did, the consequences would be fatal. Or almost.
What would happen?
The answer depends upon many factors: the composition of the comet, its speed, its proximity, the angle at which it struck.
Approaching, it might absorb the oxygen of the atmosphere. We should die, gasping and choking, of asphyxia.
It might absorb the azote, leaving us proportionately too much oxygen. We should live hours of nervous delirious joy, the whole world dancing a saraband or international hornpipe until through over-exultation we attained death cardiac or neurotic.
It might contain some gas to poison the air. The name of the star is called Wormwood. Our end would be velenous.
Its gases might combine and combust with our oxygen, causing conflagration of the air; concremation of our fields, our cities and ourselves.
It might triumph tidally, attracting the seas, pulling them up to cover the earth. The Deluge again; we should drown.
It might whirl up the earth to be its satellite; rock and reel us away.
It might bombard with boulders bigger than islands. Falling, these would chafe the air to unbearable heat; plunging into the sea, would produce tidal waves and worldwide floods; colliding with the land, would bore huge holes through to Gehenna beneath, new craters of burning, wherefrom in every direction cracks in the earth’s rind would radiate, new rows of craters of burning; fire added to fire and both to ravening water.
It might, advancing, cancel the earth’s movement; which, transformed into heat, would suffice to dissolve the globe. We should vanish in instant steam.
The choice is thus various; are the chances many?
Most astronomers answer with a comforting negative. Their contention is this. Space is infinite; the length of the earth’s annual circuit is enormous; comets are not infinite in number; few of them cut the terrestrial orbit. Therefore the arithmetical likelihood of a collision, or of even a nearish encounter, is infinitely small. Arago put the chances of crashing with the central kernel of a wanderer at one in two hundred and eighty-one million, or with some less central part say ten times greater: one in twenty-eight million one hundred thousand. Imagine a vast urn, he says, in which were twenty-eight million white balls meaning us no harm and one black ball condemning us to death. Should we take that one chance seriously? When we put in our hand to draw should we whine and shrink?
Even if the one chance fell, and a comet passed very near, its passage would be too quick to matter. It would have no time to scorch, poison, pull up the seas. In a few seconds it would be infinitely far away again, not having had the physical time to harm us.
Further, even the worst—direct collision—would be survivable. Comets have been weighed in the astrophysician’s balance and found wanting; the scale shows zero. They are but light-clouds, as Xenocrates and Theon of Alexandria called them
