Rensselaer Union, Volume 7, Number 8, Rensselaer, Jasper County, 12 November 1874 — WHAT WE KNOW ABOUT THE MOON. [ARTICLE]

WHAT WE KNOW ABOUT THE MOON.

There can be but few of the more elderly citizens of New York who do not remember the “ Moon Hoax” which was perpetrated some thirty years ago by an ingenious and impecunious journalist. He meant it as a joke, but the credulous public devoured it at once, and for a long time refused to be undeceived. At that time, as was then well known, Herschel, the great astronomer, was at the Cape of Good Hope, observing the moon. Upon this slender basis of fact the grim humorist founded his hyperbolical narration. It pretended to be an account of Herschel’a discoveries, and the smallest details were given with an accuracy and minuteness worthy of Balsac or Poe. The public were soberly told of the number and size of the instruments used, and of the extraordinary care used in the observations, the combination preventing, of course, the possibility of error. The resulting discoveries were sufficiently wonderful. Not only was the existence of animals and vegetables upon the moon abundantly proved, but men, undoubted lunarians, had been clearly seen coming and going about their business at the trilling distance from the observer of 233,756 miles. It’was too wonderful not to command instant belief. This English Columbus had not only discovered a new world, but be had also solved the secrets of illimitable space. The articles were copied far and wide; the ex--eitement spread to other countries, and, finally, the infatuation became so universal and complete that Arago felt himself obliged to go before the Academy and give the lie to the author of the hoax. Finally Herschel himself denied the whole story, and the world found itself as ignorant as before it had allowed itself to be humbugged. Since then sbience has made great -advances, and her discoveries about the earth’s satellite when stated in a popular form, as has been done by Amadee Guillemin, are a little less wonderful than the great feat of the imagination above spoken of, and the present time seems not inapt to mention a few of the more interesting things known to men of science about the moon. A beginning may be made by giving a few of the most generally known facts about the subject of this sKetch. Its distance from the earth has been already stated, but the mind refuses to grasp figures of such magnitude. A cannonball, traveling with its initial speed, would require about two weeks to complete the journey, and if the tangential and gravitating forces which keep the moon in its orbit were to be destroyed the earth and moon would not come together for over six days. The diameter of the moon is 2,159 miles. Its area is one-third and its volume one-forty-ninth that of the earth. Its density is 355 that is to say, the moon jveighs 3.55 as much as a globe of water of the same dimensions. Its gravity, compared with that of the earth, is very small, about one-fifth, so that if a man weighing 150 pounds were to be transported to the moon he would there weigh" about thirty pounds, and if he was moderately muscular he would lift 1,200 pounds with ease. The heat and light given by the moon have been measured with great accuracy. It would require 800,000 moons to equal the sun’s light. The moon radiates with the power of a body heated t</860 degrees, and it gives out warmth equal to that shed by a waxcandle at a distance of fifteen feet, which, according to Lord Rosse, is equal to a calorific effect of one-ninety-millionth of a degree, which speaks more for the delicacy of his thermometer than for the warmth of the moon. Still, inconsiderable as this amount of heat may appear, it is by it that is explained the wellknown facUthat the sky becomes clearer as the moon rises, for even this small amount of heat is sufficient to rarify the aqueous vapor of the clouds and thus dissipate them. The color of the moon is. hard to settle. Everybody knows that it is red when on the horizon, that it is yellow at night and that it is white by day. But which is its real color? Humboldt thinks it is yellow. Its red appearance when on the horizon he explains in the same manner as .the redness of the setting sun, viz.: by the refraction of the luminous rays by the atmosphere; and the whiteness of the moon by day would, of course, result if the moon were-really yellow, for that color is complementary to the blue of the atmosphere; that is, the two colors make white when mingled! Thus much may be learned about the moon without a telescope. But with thq aid of that instrument the hundreds of thousands of miles which separate the earth and moon may be reduced to about 180, so far as visual possibilities are concerned. That is to say, with a telescope magnifying 1,100 or 1,200 times an ok server on the earths can examine the moon as easily and accurately as though he were less than 200 miles distant from it. • At that distance objects 1,300 feet in diameter could be easily seen, but anything of smaller bulk than the Egyptian pyramids would eseape observation. These are the best results which, have been obtained. Telescopes have indeed bee* constructed admitting the use of

eye-pieces magnifying 6,000 times, and which would bring the observer within thirty-seven miles of the moonr-Bot their use is prevented by the diminution; of light which accompanies the observation of bodies not self-luminous by high magnifying powers. So that it can be readily seen that any minute description of the moon’s surface, its vegetation, of human and, animal inhabitants, is prima facie absurd and false. It is as if a painter should attempt to depict New York city on canvas without ever having been any nearer to it than Boston. Still 180 miles is not much in ijtself, and, it can be safely said that the whole of that part of the moon which is turned toward the earth is better known, and is mapped out with greater topographical precision, than are many parts of our own globe. When looked at with the naked eye the moon is _ seen to consist of roughnesses which bear a rude likeness to the human face, which, according to the French, who have a story for everything, is Judas buried in the moon for his sins. But when looked at with the telescope the moon appears the color of trodden snow or wet plaster, and the “ roughness” assumes at ouce the proportions of mountains. Mount Dorfel and Mount Leibnitz, for instance, are 2,500 feet high, and four others rise over 1,400 feet. Some of Tbpse mountains; as Copernicus aricl Kepler, are very bright, and others, like Plato and Endymion, are almost black, or dark, spots. Besides these mountains are seen “ cirques,” which are not unlike our volcanoes, and are some 15ft miles irr diameter, and “ rainures,” or grooves, as the term may be roughly translated. It is on these rainures that Schracter, the stoutest supporter of the hypothesis which peoples the moon, builds bis strongest argument. The rainures are about 100 in number, and are from 10 to 180 miles long, 1,500 to 10,000 feet broad, and 1,000 to 1,500 feet deep. Schracter contends that they are canals, and clearly of artificial construction —a supposition which their size conclusively negatives. Another hypothesis makes them rivers or river beds. But it would be a strange river which should begin and terminate abruptly, and run directly through or over mountains. Whatever else they may be, these rainures are not of artificial or aqueous formation.

It has been said that it would be impossible to discover with the telescope any signs of vegetation on the moon. That would be true of a detached tree, for instance, but if there were any extensive vegetable growths, such as an immense forest or a prairie, they could be clearly seen from their color. Thus tße Mare Crisium is of a dark green color and the Mare Grenitotis is a bright green; Monno Lichtenberg is a reddish, and Palus Lornnii is a yellow, approaching brown. But thaf these colors have any connection with a forest or prairie is very improbable, for this reason: The moon has no atmosphere, and without an atmosphere no form of organized life of which we have any conception could possibly exist. It may, indeed, be said that we are not acquainted with all the forms in which life manifests itself, and that would doubtless be true. Yet is it not equally clear that, if we are to conceive of other forms of life than those known to us, we must leave the realm of observed facts and enter those of pure imagination? Assuming, then, that if there is animal or vegetable life on the moon it must be similar to that on the earth, it is pretty safe to say that there is no life of either kind on the moon, because it has no atmosphere. And it is known that there is no atmosphere because there are no movable spots on the moon. If there were an atmosphere there would certainly be clouds in it, as there is in our atmosphere, and those clouds would certainly be movable and visible. But not the slightest spot on the face of the moon has ever changed its appearance from the time of the Chaldeans. Another reason is found in the manner of the occultation of stars by their passing behind the moon. If the lunar atmosphere were as dense as is ours, then a star would not be occulted at all, even though the moon passed so directly over the star’s true place on the heavens that a straight line joining the star and the observer’s eye passed through the moon’s center. This is easily seen. The refractive part of our atmosphere is 68 minutes, and the moon’s semi-diameter is only 16 minutes. Accordingly, since 16 minutes is less than a quarter of 68 minutes, if the moon’s atmosphere possessed only a fourth part of the refractive power of qur atmosphere, a star in reality behind the center of the moon’s disk would appear as a ring of light. It is on exactly the same principle that the sun appears to view when he is really below the horizon. The actual circumstances of the occulation of a star by the moon are markedly contrasted to those just mentioned. The star disappears instantly when the moon’s edge reaches the star’s place. There is no perceptible displacement of the star, no change of color, no effect whatever, such as a refractive atmosphere would produce. These and other similar considerations suggest, not indeed that the moon has absolutely no atmosphere, but that if it has any it can only be the half-thousandth part of the density of the atmosphere, or something more rare than the most complete vacuum that the best air-pump can produce. It is also certain that there can l)e no water On the moon, for water would certainly be accompanied by the aqueous vapors called clouds, and the moon has no clouds, but moves on its orbit with a sky ever serene. There is, then, on the moon no life, no air, no water, no winds, no currents, no sound except that transmitted by the vibration of solid molecule. The Queen of Night is indeed only a “ hushed and silent desert.”

That the moon has days and nights is shown by its phases. Ihe period of lunation is 709 hours, and this is divided equally into day and night. From sunrise to noon is about 177 hours, and until night is about 177 more. Then begins a night of 354) hours, or some thirty times as long as ours. But duration does not constitute the only difference between the moon’s day and night and ours. As the moon has fib atmosphere it can have no twilight. The lunarians, if there were any, could have no conception of the brilliant light fti the east, the vivid colors, and the charming shades with which our day gives place to night. Except that at the moon it takes ten hours for the sun to rise, the passage from day to night, and from night to day, is instantaneous. Even on the earth we cannot endure the brightness of the sun, tempered as it is by some thirty to 500 miles of atmosphere,' but on the ftioon the rays beat straight down with a dazzling and cruel brilliancy. And bn the other hand the lunar nights are dark with blackness of which the Egyptians had no conception, and whose gloom is only relieved by the beauty and the

glory of the stars, which shine with it power and clearness unknown to us. As 1 a place of residence, tfie moon, then, would be "rather more peculiar than salubrious. —New York Tribune.