From the Earth to the Moon Page 5

  There was nothing more to be known with regard to the intensity of its light: the scientists knew that it is three hundred thousand times weaker than that of the sun, and that its heat has no appreciable effect on a thermometer. As for the phenomenon known as “ashy light,” it is explained by the effect of sunlight reflected from the earth to the moon, which seems to complete the lunar disk when it is seen in the shape of a crescent during its first and last phases.

  Such was the state of acquired knowledge concerning the earth’s satellite. The Gun Club proposed to augment it from every point of view: cosmographic, geological, political, and moral.

  * According to Wallaston, the diameter of Sirius must be twelve times that of the sun, or over ten million miles.

  * Some of these asteroids are so small that a man could run all the way around them in one day.

  * Approximately twenty-nine and a half days.

  * The height of Mont Blanc is 15,787 feet above sea level.

  CHAPTER 6

  WHAT IT IS IMPOSSIBLE NOT TO KNOW AND WHAT IT IS NO LONGER PERMISSIBLE TO BELIEVE IN THE UNITED STATES

  ONE IMMEDIATE effect of Barbicane’s proposal was to focus attention on all astronomical facts relating to the moon. Everyone had been studying it assiduously. It seemed that the moon had appeared on the horizon for the first time, that no one had ever seen it in the sky before. It became fashionable; it was the celebrity of the day without seeming less modest, and took its place among the “stars” without showing any more pride. The newspapers revived old stories in which the “wolves’ sun” played a part; they recalled the influence that the ignorance of earlier times had attributed to it, they sang its praises in every way; they stopped just short of quoting its witty remarks. The whole country had a case of “moon fever.”

  The scientific journals dealt more specifically with matters concerning the Gun Club’s project. They published the letter from the Cambridge Observatory, commented on it, and gave it their unqualified approval.

  In short, it was no longer permissible for even the least learned American to be ignorant of a single one of the known facts about the moon, or for even the most narrow-minded old woman to go on entertaining superstitious beliefs about it. Science came to them in every form and penetrated through their eyes and ears. It was no longer possible to be an ignoramus—in astronomy.

  Till then, many people did not know how the distance from the earth to the moon had been measured. Experts took the opportunity to tell them that it had been measured by means of the moon’s parallax. If the word “parallax” seemed to surprise them, they were told that it was the angle formed by two straight lines projected to the moon from opposite ends of the earth’s radius. If they doubted the accuracy of this method, it was immediately proven to them that not only was this average distance 234,347 miles, but that the astronomers’ error was less than seventy miles.

  For the sake of those who were not familiar with the motions of the moon, the newspapers demonstrated daily that it has two distinct motions—rotation on its axis and revolution around the earth—which both take place in the same length of time: twenty-seven and a third days.*

  The movement of rotation is the one that makes day and night on the moon’s surface; but there is only one day and one night per lunar month, and each lasts 354⅓ hours. Fortunately, however, the side turned toward the earth is illuminated by it with an intensity equal to the light of fourteen moons. As for the other side, which is always invisible to us, it naturally has 354? hours of profound darkness mitigated only by “the pale glow that falls from the stars.” This is due solely to the fact that the motions of rotation and revolution take place in exactly the same span of time, a phenomenon which, according to Cassini and Herschel, is common to the satellites of Jupiter, and probably to all other satellites as well.

  There were some well-meaning but rather dense people who at first could not understand that the same side of the moon is always visible from the earth because the moon rotates once on its axis during the time required for it to circle the earth. They were told, “Go into your dining room and walk around the table so that you’re always looking at the center of it. When you’ve gone all the way around it, you’ll have pivoted once on your own axis, too, because your eyes will have swept past every point in the room. The room is the sky, the table is the earth, and you’re the moon!” And they were delighted with the comparison.

  Thus the moon constantly shows the same side to the earth. To be precise, however, it must be added that as the result of a certain oscillation known as libration, we are able to see a little more than half of its surface: about fifty-seven percent of it.

  When the ignorant had come to know as much as the director of the Cambridge Observatory about the moon’s rotation, they became concerned with its revolution around the earth. A score of scientific journals quickly set about enlightening them. They learned that the firmament, with its infinity of stars, can be regarded as a vast dial on which the moon moves, indicating the correct time to the inhabitants of the earth; that it is in this movement that the moon shows its different phases; that the moon is full when it is in opposition to the sun, i.e., when the moon, earth, and sun form a straight line, with the earth in the middle; that the moon is new when it is in conjunction with the sun, i.e., when it is between it and the earth; and finally that the moon is in its first or last quarter when it forms a right angle with the sun and the earth, with itself at the vertex.

  A few perspicacious Americans concluded from this that eclipses could take place only at times of conjunction or opposition, and their reasoning was sound. In conjunction, the moon can eclipse the sun, and in opposition the earth can eclipse the moon. These eclipses do not happen twice in a lunar month because the plane of the moon’s motion is inclined to the ecliptic, that is, the plane of the earth’s motion.

  As for the height that the moon can reach above the horizon, the letter from the Cambridge Observatory had said everything on that subject. Everyone knew that this height varies according to the latitude of the place from which one is observing. But the only parts of the globe where the moon passes the zenith, that is, where it can be seen directly overhead, necessarily lie between the twenty-eighth parallels and the equator. Hence the important recommendation to perform the experiment in this part of the earth, so that the projectile could be launched perpendicularly and thus escape more quickly from the pull of gravity. It was an essential condition for the success of the enterprise, and public opinion was keenly interested in it.

  As for the path followed by the moon in its revolution around the earth, the Cambridge Observatory had made it sufficiently clear, even to the most ignorant people in all countries, that this path is not a circle but an ellipse, with the earth occupying one of the foci. These elliptical orbits are common to all planets as well as all satellites, and rational mechanics proves conclusively that it could not be otherwise. It was widely understood that the moon is at its apogee when it is furthest from the earth, and at its perigee when it is nearest.

  This, then, was what every American knew, whether he liked it or not, what no one could decently be ignorant of. But while these true principles were rapidly disseminated, it was less easy to uproot certain errors and illusory fears.

  Some people maintained, for example, that the moon was a former comet which, while moving in its elongated orbit around the sun, had passed close to the earth and been captured by its gravity. These parlor astronomers felt that this explained the seared appearance of the moon, an irreparable misfortune for which they blamed the sun. But when it was pointed out to them that comets have an atmosphere, while the moon has either very little or none at all, they had nothing to say in reply.

  Others, who belonged to the breed of tremblers, had certain fears with regard to the moon. They had heard that, since the observations made in days of the caliphs, its speed of revolution around the earth had been increasing. From this they concluded, quite logically, that the acceleration must indicate a decreas
e in the distance between the earth and the moon, and that if the process continued the moon would eventually fall against the earth. However, they had to be reassured and stop fearing for future generations when they were told that, according to the calculations of Laplace, a famous French mathematician, this acceleration is contained within very narrow limits, and that a proportionate diminution will soon follow. Thus the equilibrium of the solar system cannot be upset in the centuries to come.

  In the last place came the superstitious category of the ignorant. These people are not content to lack knowledge: they claim to know things that are actually false, and they “knew” many such things about the moon. Some of them regarded it as a smooth mirror by means of which people could see each other from various points on the earth and communicate their thoughts. Others maintained that out of a thousand new moons that had been observed, nine hundred fifty had brought about notable changes such as cataclysms, revolutions, earthquakes, floods, etc. They thus believed that the moon had a mysterious influence on human destiny and considered it to be the “true counterbalance” of existence. They thought that each lunar inhabitant was attached to each inhabitant of the earth by a sympathetic bond. Following Dr. Mead they maintained that the vital system was completely dependent on the moon. They stubbornly insisted that boys were born mainly during the new moon and girls during the last quarter, etc., etc. But finally they had to give up these gross errors and return to the truth. Although the moon, stripped of all its influence, was diminished in the minds of those who paid court to all powers, and although some people turned their backs on it, the vast majority decided in favor of it. As for the Americans, their only ambition was now to take possession of that new continent in space, and plant the star-spangled banner of the United States on its highest peak.

  * This is the duration of the sidereal revolution, i.e., the time it takes the moon to return to a given star.

  CHAPTER 7

  THE HYMN TO THE PROJECTILE

  IN ITS memorable letter of October 7, the Cambridge Observatory had dealt with the problem from the astronomical point of view. It now had to be solved mechanically. At this point the practical difficulties would have been insurmountable in any other country than America. There, they were only child’s play.

  Without wasting any time, President Barbicane appointed an executive committee from among the members of the Gun Club. In three meetings this committee was to elucidate the three great questions of the cannon, the projectile, and the propellant. It was composed of four members who were highly learned in these matters: Barbicane, who had a deciding vote in case of deadlock, General Morgan, Major Elphiston, and finally the inevitable J. T. Maston, who was assigned to act as secretary and recorder.

  On October 8 the committee met in Barbicane’s house at 3 Republican Street. Since it was important that such a serious discussion should not be disturbed by the cries of the stomach, the four members of the Gun Club sat down around a table covered with sandwiches and large teapots. J. T. Maston screwed his pen into his iron hook and the meeting began.

  Barbicane was the first to speak:

  “Gentlemen, we must solve one of the most important problems of ballistics, that exalted science which deals with the motion of projectiles, or bodies launched into space by some sort of propelling power, then abandoned to themselves.”

  “Ah, ballistics!” J. T. Maston exclaimed with deep emotion.

  “It might have seemed more logical,” Barbicane went on, “to devote this first meeting to a discussion of the cannon …”

  “Yes,” remarked General Morgan.

  “However,” said Barbicane, “after thorough consideration it seems to me that the question of the projectile ought to take precedence over that of the cannon, and that the dimensions of the latter ought to depend on those of the former.”

  “I request permission to speak,” said J. T. Maston.

  It was granted to him with all due deference to his magnificent past.

  “Valiant friends,” he said in an inspired tone, “our president is right to give priority to the question of the projectile. The projectile we’re going to send to the moon will be our messenger, our ambassador, and I would like to consider it from a purely moral point of view.”

  This new way of regarding a projectile aroused the curiosity of the other committee members. They listened to J. T. Maston with keen attention.

  “My dear colleagues,” he went on, “I’ll be brief. I’ll disregard the physical projectile, the one that kills, and consider only the mathematical, moral projectile. To me, the artillery projectile is the most brilliant manifestation of human power, which is entirely summed up in it. It was in creating it that man came closest to the Creator!”

  “Well said!” exclaimed Major Elphiston.

  “Yes,” the orator continued, “God made the stars and the planets, but man made the artillery projectile, that criterion of earthly velocities, that miniature version of the heavenly bodies wandering in space—and they, after all, are only a different kind of projectile! To God belong the speeds of electricity, light, stars, comets, planets, satellites, sound, and wind, but to us belongs the speed of the artillery projectile, a hundred times greater than the speed of the fastest trains and horses!”

  J. T. Maston was transported; his voice took on lyrical inflections as he sang this sacred hymn to the projectile.

  “Would you like figures? I’ll give you some eloquent ones! Let’s consider only the modest twenty-four-pounder. It’s true that it moves 800,000 times slower than electricity, 640,000 times slower than light, seventy-three times slower than the earth in its orbit around the sun, but when it leaves the cannon its speed is greater than that of sound:* it is traveling at the rate of 1,200 feet per second, 12,000 feet in ten seconds, 14 miles a minute, 840 miles an hour, 20,100 miles a day—approximately the same speed as a point on the equator in the earth’s rotation—and 7,336,500 miles a year. At this speed it would take eleven days to reach the moon, twelve years to reach the sun, and 360 years to reach Neptune, at the outermost limit of the solar system. That’s what that modest projectile, the work of our hands, could do! Just think what it will be like when we fire a projectile more than twenty times as fast, at a speed of seven miles a second! Ah, magnificent projectile, I like to think that you’ll be received up there with all the honor befitting an ambassador of the earth!”

  The end of this lofty speech was greeted with loud cheers, and J. T. Maston, overcome with emotion, sat down amid the congratulations of his colleagues.

  “And now that we’ve paid ample tribute to poetry,” said Barbicane, “let’s approach the matter directly.”

  “We’re ready,” replied the committee as each man prepared to eat his sixth sandwich.

  “You know the problem that must be solved,” said Barbicane. “We must give a projectile a speed of 36,000 feet per second. I have reason to think we’ll succeed. But now let’s examine the speeds obtained so far. General Morgan can enlighten us on that subject.”

  “Yes, especially since I was on the Experiment Committee during the war,” replied the general. “First, I can tell you that the Dahlgren hundred-pounders, which had a range of three miles, gave their projectiles a muzzle velocity of 1,500 feet per second.”

  “Good. And what about the Rodman Columbiad?”* asked Barbicane.

  “The Rodman Columbiad, tested at Fort Hamilton, near New York City, shot a half-ton projectile six miles, with a muzzle velocity of 2,400 feet per second, a result never obtained by Armstrong and Paliser in England.”

  “Oh, the English!” said J. T. Maston, shaking his formidable hook at the horizon.

  “So 2,400 feet per second is the highest velocity reached so far?” asked Barbicane.

  “Yes,” replied Morgan.

  “I will say, however,” remarked J. T. Maston, “that if my mortar hadn’t burst …”

  “Yes, but it did burst,” Barbicane said with a benevolent gesture. “Now, let’s take that velocity of 2,400 feet p
er second as our starting point. We’ll have to increase it fifteenfold. I’ll postpone discussing the means of achieving that velocity until another meeting! For the moment, I’d like to call your attention to the dimensions that the projectile will have to have. As you can well imagine, we won’t be dealing with a little bullet weighing no more than half a ton!”

  “Why not?” asked Major Elphiston.

  “Because our projectile,” J. T. Maston said quickly, “must be big enough to attract the attention of the inhabitants of the moon, if there are any.”

  “Yes,” said Barbicane, “and also for an even more important reason.”

  “What do you mean?” asked the major.

  “I mean that it’s not enough to send off a projectile and then forget about it: we must be able to watch it until it reaches its destination.”

  “What!” exclaimed the general and the major, somewhat startled by this idea.

  “If we can’t watch it,” Barbicane said with self-assurance, “our experiment will be inconclusive.”

  “Then you must be planning to make a projectile of colossal size!” said the major.

  “No. Listen carefully. As you know, optical instruments have been highly developed. There are telescopes capable of magnifying objects six thousand times, and bringing the moon to an apparent distance of forty miles. At that distance, objects sixty feet wide are clearly visible. The reason why telescopes haven’t been made any more powerful is that their clarity decreases as their power increases, and the moon, which is only a reflecting mirror, doesn’t give off enough light to make it desirable to increase magnification beyond that point.”