The stranger had emerged slowly from the depths of space. Instead of appearing suddenly, as more than once the great comets have been observed to do,—either because coming into view immediately after their perihelion passage, or after a long series of storms or moonlight nights has prevented the search of the sky by the comet-seekers—this floating star-mist had at first remained in regions visible only to the telescope, and had been watched only by astronomers. For several days after its discovery, none but the most powerful equatorials of the observatories could detect its presence. But the well-informed were not slow to examine it for themselves. Every modern house was crowded with a terrace, partly for the purpose of facilitating aerial embarkations. Many of them were provided with revolving domes. Few well-to-do families were without a telescope, and no home was complete without a library, well furnished with scientific books.
The comet had been observed by everybody, so to speak, from the instant it became visible to instruments of moderate power. As for the laboring classes, whose leisure moments were always provided for, the telescopes set up in the public squares had been surrounded by impatient crowds from the first moment of visibility, and every evening the receipts of these astronomers of the open air had been incredible and without precedent. Many workmen, too, had their own instruments, especially in the provinces, and justice, as well as truth, compels us to acknowledge that the first discoverer of the comet (outside of the professional observers) had not been a man of the world, a person of importance, or an academician, but a plain workman of the town of Soissons, who passed the greater portion of his nights under the stars, and who had succeeded in purchasing out of his laboriously accumulated savings an excellent little telescope with which he was in the habit of studying the wonders of the sky. And it is a notable fact that prior to the twenty-fourth century, nearly all the inhabitants of the earth had lived without knowing where they were, without even feeling the curiosity to ask, like blind men, with no other preoccupation than the satisfaction of their appetites; but within a hundred years the human race had begun to observe and reason upon the universe about them.
To understand the path of the comet through space, it will be sufficient to examine carefully the accompanying chart. It represents the comet coming from infinite space obliquely towards the earth, and afterwards falling into the sun which does not arrest it in its passage toward perihelion. No account has been taken of the perturbation caused by the earth’s attraction, whose effect would be to bring the comet nearer to the earth’s orbit. All the comets which gravitate about the sun—and they are numerous—describe similar elongated orbits,—ellipses, one of whose foci is occupied by the solar star. The drawing on page gives an idea of the intersections of the cometary and planetary orbits, and the orbit of the earth about the sun. On studying these intersections, we perceive that a collision is neither an impossible nor an abnormal event.
The comet was now visible to the naked eye. On the night of the new moon, the atmosphere being perfectly clear, it had been detected by a few keen eyes without the aid of a glass, not far from the zenith near the edge of the milky way to the south of the star Omicron in the constellation of Andromeda, as a pale nebulæ, like a puff of very light smoke, quite small, almost round, slightly elongated in a direction opposed to that of the sun—a gaseous elongation, outlining a rudimentary tail. This, indeed, had been its appearance since its first discovery by the telescope. From its inoffensive aspect no one could have suspected the tragic role which this new star was to play in the history of humanity. Analysis alone indicated its march toward the earth.
But the mysterious star approached rapidly. The very next day the half of those who searched for it had detected it, and the following day only the near-sighted, with eyeglasses of insufficient power, had failed to make it out. In less than a week every one had seen it. In all the public squares, in every city, in every village, groups were to be seen watching it, or showing it to others.
Day by day it increased in size. The telescope began to distinguish distinctly a luminous nucleus. The excitement increased at the same time, invading every mind. When, after the first quarter and during the full moon, it appeared to remain stationary and even to lose something of its brilliancy, as it had been expected to grow rapidly larger, it was hoped that some error had crept into the computations, and a period of tranquillity and relief followed. After the full moon the barometer fell rapidly. A violent storm-center, coming from the Atlantic, passed north of the British Isles. For twelve days the sky was entirely obscured over nearly the whole of Europe.
Once more the sun shone in purified atmosphere, the clouds dissolved and the blue sky reappeared pure and unobscured; it was not without emotion that men waited for the setting of the sun—especially as several aerial expeditions had succeeded in rising above the cloud-belts, and aeronauts had asserted that the comet was visibly larger. Telephone messages sent out from the mountains of Asia and America announced also its rapid approach. But great was the surprise when at nightfall every eye was turned heavenward to seek the flaming star. It was no longer a comet, a classic comet such as one had seen before, but an aurora borealis of a new kind, a gigantic celestial fan, with seven branches, shooting into space seven greenish streamers, which appeared to issue from a point hidden below the horizon.
No one had the slightest doubt but that this fantastical aurora borealis was the comet itself, a view confirmed by the fact that the former comet could not be found anywhere among the starry host. The apparition differed, it is true, from all popularly known cometary forms, and the radiating beams of the mysterious visitor were, of all forms, the least expected. But these gaseous bodies are so remarkable, so capricious, so various, that everything is possible. Moreover, it was not the first time that a comet had presented such an aspect. Astronomy contained among its records that of an immense comet observed in 1744, which at that time had been the subject of much discussion, and whose picturesque delineation, made de visu by the astronomer Chèzeaux, at Lausanne, had given it a wide celebrity. But even if nothing of this nature had been seen before, the evidence of one’s eyes was indubitable.
Meanwhile, discussions multiplied, and a veritable astronomical tournament was commenced in the scientific reviews of the entire world—the only journals which inspired any confidence amid the epidemic of buying and selling which had for so long a time possessed humanity. The main question, now that there was no longer any doubt that the star was moving straight toward the earth, was its position from day to day, a question depending upon its velocity. The young computor of the Paris observatory, chief of the section of comets, sent every day a note to the official journal of the United States of Europe.
A very simple mathematical relation exists between the velocity of every comet and its distance from the sun. Knowing the former one can at once find the latter. In fact the velocity of the comet is simply the velocity of a planet multiplied by the square root of two. Now the velocity of a planet, whatever its distance, is determined by Kepler’s third law, according to which the squares of the times of revolution are to each other as the cubes of the distances. Nothing evidently, can be more simple. Thus, for example, the magnificent planet, Jupiter, moves about the sun with a velocity of 13,000 meters per second. A comet at this distance moves, therefore, with the above-mentioned velocity, multiplied by the square root of two, that is to say by the number 1.4142. This velocity is consequently 18,380 meters per second.
The planet Mars revolves about the sun at the rate of 24,000 meters per second. At this distance the comet’s velocity is 34,000 meters per second.
The mean velocity of the earth in its orbit is 29,460 meters per second, a little less in June, a little more in December. In the neighborhood of the earth, therefore, the velocity of the comet is 41,660 meters, independently of the acceleration which the earth might occasion.
These facts the laureate of the Institute called to the attention of the public which, moreover, already possessed some general notions upon the theory of celestial mechanics.
When the threatening star arrived at a distance from the sun equal to that of Mars, the popular fear was no longer a vague apprehension; it took definite form, based, as it was, upon the exact knowledge of the comet’s rate of approach. Thirty-four thousand meters per second meant 2040 kilometers per minute, or 122,400 kilometers per hour!
As the distance of the orbit of Mars from that of the earth is only 76,000,000 of kilometers, at the rate of 122,400 kilometers an hour, this distance would be covered in 621 hours, or about twenty-six days. But, as the comet approached the sun, its velocity would increase, since at the distance of the earth its velocity would be 41,660 meters per second. In virtue of this increase of speed, the distance between the two orbits would be traversed by a comet in 558 hours, or in twenty-three days, six hours.
But the earth at the moment of meeting with the comet, would not be exactly at that point of its orbit intersected by a line from the comet to the sun, because the former was not advancing directly toward the latter; the collision, therefore, would not take place for nearly a week later, namely: at about midnight on Friday, the 13th of July. It is unnecessary to add that under such circumstances the usual arrangements for the celebration of the national fête of July 14th had been forgotten. National fête! No one thought of it. Was not that date far more likely to mark the universal doom of men and things? As to that, the celebration by the French of the anniversary of that famous day had lasted—with some exceptions, it is true—for more than five centuries: even among the Romans anniversaries had never been observed for so long a period, and it was generally agreed that the 14th of July had outlived its usefulness.
It was now Monday, the 8th of July. For five days the sky had been perfectly clear, and every night the fan-like comet hovered in the sky depths, its head, or nucleus, distinctly visible and dotted with luminous points which might well be solid bodies several kilometers in diameter, and which, according to the calculations, would be the first to strike the earth, the tail being in a direction away from the sun and in the present instance behind and obliquely situated with reference to the direction of motion. The new star blazed in the constellation of Pisces. According to observations taken on the preceding evening, July 8th, its exact position was: right ascension, 23h., 10m., 32s.; declination north, 7°, 36´, 4˝. The tail lay entirely across the constellation of Pegasus. The comet rose at 9h., 49m. and was visible all night long.
During the lull of which we have spoken, a change in public opinion had occurred. From a series of retrospective calculations an astronomer had proved that the earth had already on several occasions encountered comets, and that each time the only result had been a harmless shower of shooting stars. But one of his colleagues had replied that the present comet could not in any sense be compared to a swarm of meteors, that it was gaseous, with a nucleus composed of solid bodies and he had in this connection recalled the observations made upon a comet famous in history, that of 1811.
This comet of 1811 justified, in a certain respect, a real apprehension. Its dimensions were recalled to mind: its length of 180,000,000 kilometers, that is to say, a distance greater than that of the earth from the sun; and the width of its tail at its extreme point, 24,000,000 kilometers. The diameter of its nucleus measured 1,800,000 kilometers, forty thousand times that of the earth, and its nebulous and remarkably regular elliptical head was a spot brilliant as a star, having itself a diameter of no less than 200,000 kilometers. The spot appeared to be of great density. It was observed for sixteen months and twenty-two days. But the most remarkable feature of this comet was the immense development to which it attained without approaching very close to the sun; for it did not reach a point nearer than 150,000,000 kilometers, and thus remained more than 170,000,000 kilometers from the earth. As the size of comets increases as they near the sun, if this one had experienced to a greater degree the solar action, its appearance would certainly have been still more wonderful, and, doubtless, terrifying to the observer. And as its mass was far from insignificant, if it had fallen directly into the sun, its velocity, accelerated to the rate of five or six hundred thousand meters per second at the moment of collision, might, by the transformation of mechanical energy into thermal energy, have suddenly increased the solar radiations to such a degree as to have utterly destroyed in a few days every trace of vegetable and animal life upon the earth.
A physicist, indeed, had made this curious remark, that a comet of the same size as that of 1811, or greater, might thus bring about the end of the world without actual contact, by a sort of expulsion of solar light and heat, analogous to that observed in the case of temporary stars. The impact would, indeed, give rise to a quantity of heat six times as great as that which would be produced by the combustion of a mass of coal equal to the mass of the comet.
It had been shown that if such a comet in its flight, instead of falling into the sun, should collide with our planet, the end of the world would be by fire. If it collided with Jupiter it would raise the temperature of that globe to such a point as to restore to it its lost light, and to make it for a time a sun again, so that the earth would be lighted by two suns, Jupiter becoming a sort of minor night-sun, far brighter than the moon, and shining by its own light—of a ruby-red or garnet color, revolving about the earth in twelve years. A nocturnal sun! That is to say, no more real night for the earth.
The most classical astronomical treatises had been consulted; chapters on comets written by Newton, Halley, Maupertuis, Lalande, Laplace, Arago, Faye, Newcomb, Holden, Denning, Robert Ball, and their successors, had been re-read. The opinion of Laplace had made the deepest impression and his language had been textually cited: “The earth’s axis and rotary motion changed; the oceans abandoning their old-time beds, to rush toward the new equator; the majority of men and animals overwhelmed by this universal deluge, or destroyed by the violent shock; entire species annihilated; every monument of human industry overthrown; such are the disasters which might result from collision with a comet.”
Thus discussion, researches into the past, calculations, conjectures succeeded each other. But that which made the deepest impression on every mind was first that, as proved by observation, the present comet had a nucleus of considerable density, and second, that carbonic-oxide gas was unquestionably the chief chemical constituent. Fear and terror resumed their sway. Nothing else was thought of, or talked about, but the comet. Already inventive minds sought some way, more or less practicable, of evading the danger. Chemists pretended to be able to preserve a part of the oxygen of the atmosphere. Methods were devised for the isolation of this gas from the nitrogen and its storage in immense vessels of glass hermetically sealed. A clever pharmacist asserted that he had condensed it in pastilles, and in a fortnight expended eight millions in advertising. Thus commerce made capital out of everything, even universal death. All hope was not, however, abandoned. People disputed, trembled, grew anxious, shuddered, died even—but hoped on.
The latest news was to the effect that the comet, developing, as it approached the thermal and electric influences of the sun, would have at the moment of impact a diameter sixty-five times that of the earth, or 828,000 kilometers.
It was in the midst of this state of general anxiety that the session of the Institute, whose utterance was awaited as the last word of an oracle, was opened.
The director of the observatory of Paris was naturally to be the first speaker; but what seemed to excite the greatest interest in the public was the opinion of the president of the academy of medicine on the probable effects of carbonic-oxide. The president of the geological society of France was also to make an address, and the general object of the session was to pass in review all the possible ways in which our earth might come to an end. Evidently, however, the discussion of its collision with the comet would hold the first place.
As we have just seen, the threatening star hung above every head; everybody could see it; it was growing larger day by day; it was approaching with an increasing velocity; it was known to be at a distance of only 17,992,000 kilometers, and that this distance would be passed over in five days. Every hour brought this menacing hand, ready to strike, 149,000 kilometers nearer. In six days anxious humanity would breathe freely—or not at all.