How do wall craters arise?

Excursion to the moon

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Hardly any other subject in popular astronomy has occupied the imaginations of earthly children so often and so persistently as the obvious question of how it would be like to live on the moon, our closest neighbor in space, whether there is something quite different from ours on it The world of humans, animals and plants is indigenous, or whether its light mountains and shady valleys are perhaps assigned to the souls separated from the earth as a place to stay, either for everyone in general, or only for those of unbaptized children, as the Middle Ages fable? Most intelligent people have always considered themselves justified in assuming that our neighboring world is by and large very similar to the earth and that the moonspots, with the interpretation of which the peoples' imagination has so thoroughly occupied, stem from differences in terrain and do not exist Imagine the mirror image of the earth, as individual Greeks and Indians thought.

Given the impossibility of a more exact investigation and the lack of direct information, this favorite direction of the human imagination, which hardly escapes any contemplative mind on beautiful full moon spring nights, ventured early in longing, enthusiastic poems, in romantic journeys to the moon, at which point Of course, Luna as the ideal world far outshines our world of reality and misery and has to overshadow it, which naturally led to humorous treatment and satire. The fantastic-satirical “moon journeys” therefore form a special poetic genre of world literature, and truly not the worst. What sequence of adventurous space trips, from that "moon trip" in the "true stories" Lucian's to the now so popular, but nothing less than classic, space voyages by Julius Vernethat can only satisfy a rather bad taste!

In the great time of the rebirth of all arts and sciences, which are briefly called the Renaissance, these [234] Lunar journeys became a welcome means of mocking Aristotelian philosophy with its scholastic interpretation and also the disputes between theology and astronomy of the time, and one still reads with pleasure in the "Lunar Journey" by the French poet Cyrano de BergeracHow one threatens a stranger on the moon with the death penalty if he does not want to give up his heretical opinion that that great cosmic body, whose sole purpose is to serve as a lamp to the inhabitants of the moon in the absence of the sun, is an inhabited earth and its home. Sixteen years before Bergerac’s book, 1634, was in Germany Kepler’s "Traum vom Monde" appeared in print as a posthumous work, a text that describes the conditions of the lunar world in a fantastic guise according to the state of astronomy of that time and at the same time shows us the great astronomers as amiable poets.

Did the other authors use more or less inept means of transport to get their heroes from the earth to the moon - Lucian a waterspout, Ariost Elias' fire chariot, Franz Godwin a team of wild geese, Bergerac a flying machine, Verne even a monster - Cannon - this is how Kepler sensibly uses the shadow, which stretches itself from one celestial body to the other during solar and lunar eclipses without interruption, as the enormous bridge on which the light-hostile demons can quickly transfer a person, but have to hurry with it the shadow does not tear off before reaching its goal. With unshakable faith in the theory of Copernicus on the one hand and with a foreboding confidence in the coming Newton on the other, Kepler, like Bergerac, described the rotation of the globe abandoned by travelers, the increasing cold of space, the decreasing gravitational pull of the earth, until the travelers, beyond the neutral zone, begin to move rapidly towards the moon as a result of their gravity, in order to land there at accelerated speed. Then, with the deepening power of mathematical genius, Kepler sketches for us a picture of the celestial phenomena from the moon, among which, of course, the sight of the Volva, as the earth is called because of its daily rotation, occupies a prominent place.

His description, which is still worth reading today, could of course not turn out to be a trial in all directions given the inadequacy of the optical aids and methods of that time. So Kepler still believed in the habitability of the moon, and that soon after his passing through the astronomer Riccioli Well-founded doubts about such a possibility, because the moon lacks the first conditions of life, air and water, have only recently been raised to the necessary security. Even in our century, F. P. Gruithuysen in Munich the craters of the moon, some twelve miles and more wide, which Kepler had taken for deep wells in which the inhabitants of the moon were supposed to hide from the immense heat of the sun, for colossal round buildings, circular walls and city walls, and so on Brandes even came up with the idea of ​​initiating a telegraphic exchange of ideas with the people of the moon, with the aid of country-sized rapeseed fields, which should be given the outlines of mathematical figures. Gruithuysen’s opinion that the Earth people or Geen would come into very close contact and intercourse with the Moon people or Meneen in the future Börne as is well known, already prompted a determination of the visiting ceremony. He thinks that we should just wait and see, since the inhabitants of the moon, as members of the smaller world, denote us first Owed a visit.

If we now leave this fantastic satirical field and ask ourselves: what does today's science know about the more detailed nature of the moon? so we must say that this age-old neighborly curiosity and sympathy found its complete satisfaction only through a recently published magnificent work by the English astronomers J. Nasmyth and J. Carpenter[1] has found which describes the moon according to all its peculiarities in a language understandable to every educated person, and has reduced the cost of a picturesque journey to the moon, which actually replaces the book, to twenty-four marks. After thirty years of study of the moon, these researchers have made relief maps of the most instructive areas of it with an accuracy that only a long exercise in telescopic vision can provide. These reliefs are then illuminated from the side, so that the elevations cast long shadows, as in the first and last quarters of the moon, were photographed and reproduced by the light pressure in such an admirable way that, with the correct position of these quarters and the closure of the one You have to convince your eyes with your fingertip that you really only have mirror-like light prints and not the reliefs themselves. With the help of these maps, which hitherto had no equal, we are able to orientate ourselves better on the moon than we would be able to do with the best telescopes, indeed, perhaps better than we would be able to do on an actually carried out journey .

From this we learn that the moon, like a pockmarked face, is densely covered with thousands of smaller and larger craters, which are generally just as formed as the active or extinct volcanic mountains of the earth, except that the smallest are still visible are larger than our greatest volcanoes, while there are numerous colossal rings of this kind on the moon, in the space of which, more than ten geographical miles in diameter, entire provinces and German lands could be found. Isolated mountain ranges rise ruggedly, with peaks rising to twenty thousand feet, the lunar alps and the lunar apennines, and the plains are crisscrossed by many miles of, half-mile-wide, yawning fissures under which one may imagine those fissures that Ariostus can be filled with all those things that earth man lose, such as his intellect, the vain earthly glory, etc., before he knows it:

With sighs of love and with vain tears,
With empty time that passes over the game
At leisure, the ignorant yawn,
With hollow plans that the wind blows
With all that poor unfulfilled longing
Almost the whole site is full.

A large part of this classic work is concerned with inferring from those scars and scrapes the developmental diseases and struggles which the moon had to go through in its youth, before it attained the manly wrinkled face which it now holds almost invariably. The gigantic nature of the craters is made easier to understand by the less attractive force of the smaller mass and the lack of atmospheric pressure; Forces similar to those of the earthly volcanoes had to exert a much stronger effect there: the volcanic ejecta could be thrown five or six miles under certain circumstances, and the craters and ring walls thus formed were so resistant to subsequent weathering due to the lack of water and air protected that the moon is in its original purity of character, like a Creation Medal represents our eyes. It is of course impossible to give due account of these circumstances in a short journal article; Let us rather try, with the help of the authors who are at the height of science, to pay a brief visit in our minds to the moon in order to see phenomena that have probably never been seen by a breathing being.

The entrepreneurs of this great social tour cite their excuse - if one was required - that for a thoughtful observer who gazes at the moon night after night, it sees the sun rise over its volcanic landscapes and the sequence of its light effects until it sets enjoys the fact that it is almost inevitable to turn into an inhabitant or visitor of the moon oneself from time to time. If one takes this first step in silence and solitude in front of a mighty telescope, the irresistible urge soon arises to go beyond what is actually visible, and the invisible part of the landscape painting from the results and conclusions of the [235] To supplement science, to briefly complete a picture of which the philosophers would say that it does not exist because it does not depict itself on the ground of the eye. Under the safe guidance of our informants, we climb the steep slope of one of the larger wall craters near the center of the moon, e.g. B. Copernicus, for which, incidentally, we would need six times less muscular exertion than on earth, because our weight there would be so much times less. The day on the moon is three hundred and fifty-four hours and the night is just as long. Without a preceding twilight, only announced by the shimmer of the zodiacal light, without dawn and gilding of the mountain peaks, the sun rises slowly over the horizon, which is limited by the stronger curvature of the moon's surface, radiating a blinding light that emerges from the dark surroundings from the first moment. Twenty-nine times slower than ours, the disk of rays rises above the horizon; The shadows cast by the mountain peaks and craters are shortening very slowly. And just as the sun shines in a black sky, these shadows also appear pitch black; With the blue reflected light of our heavenly vault, the scattered light, which softens the shadows in us, is also missing. Everywhere we look, light and shadow stand side by side in abrupt contrast; those gentle transitional tones of the atmosphere are missing[WS 1]with which she conveys night and morning, evening and night, light and shadow by embellishing the earthly landscape with splendid refractive and absorbent colors. What is missing is that mild blue veil that she spreads over the distance and depths and over the abyss of the universe itself, the laughing blue sky with the white clouds. Every distant detail on the moon itself, as in the vast universe, is clearly recognizable there even by day.

As hour after hour slips by, the rays of the sun slowly reach the summit on the summit of our Ringgebirge, until finally the circle is closed and the enormous crater rim, twelve German miles in diameter, embraces the dark abyss as a silver-shining hoop. Gradually the light also reaches the somewhat lower peaks of the central cones, which, comparable to Vesuvius in the Somma, have risen in the middle of the volcanic wall. Most of the lunar craters show, incidentally, this formation, not only peculiar to the earth's craters, which is explained by the decline in volcanic activity, and a bird's-eye view of Vesuvius and its volcanic surroundings shows us a miniature painting very similar to the lunar landscapes. If we now, in view of the fact that the view from a lower point would be comparatively more limited than on earth, return to our lunar vantage point, situated high up, and turn our gaze backwards to the sunlit side of the cosmorama, we overlook one wild region of the greatest volcanic desolation. Crater after crater down to an English mile in diameter pile up in innumerable numbers, so that, as far as we can see, the surface looks as if it were all overflowing with them. Close behind us, also casting black shadows, is pressing, rock on rock and abyss on abyss; we see gaping cracks of gruesome depth and blackness, punctuated by craters, tower-like battlements, and heaps of cinder and colored volcanic debris. No trace of past organic life! No weeds or moss soften the sharp edges and hard surfaces; no coating of cryptogamic or lichen-like vegetation gives the hard, burned-out surface a color of life. As far as we can see the landscape, it is the realization of a terrible dream of desolation and lifelessness.

In addition, there is this uninterrupted silence, in which gullies wide for miles could open without our being able to hear anything of it in the absence of the element conveying the sound, wherever we turn the gaze of the spirit, a dreadful one, even in the greatest distance through no aerial perspective softened light next to pitch-black shadows. Even the sky is deep black, and next to the sun most of the planets, the fixed stars, are visible in the only slightly changed positions known to us, but without sparkling, as is the case with us. Invariably in the middle of the vertex or, if we are more on the edge of the lunar hemisphere, which is constantly turned towards our earth, describing a small circle around the vertex of the sky, the earth appears, within a lunar day that is equal to twenty-nine earth days, changing its appearance as well as for us the moon, now appearing as a colossal sickle or as full earth, then disappearing as new earth, but turning around itself twenty-nine times and constantly presenting a new spectacle to the moon. If at the end of the long lunar day the sun is just as slow and just as colorless as it came, sunk behind the crater walls and mountain ranges, then the earth offers a magnificent spectacle. Appearing four times larger in diameter than the moon, every hour of the endless night it offers him a different spectacle as an immense clock, and the lunar landscape, when it shines over it in its full splendor, transfigures with an abundance of light that we often see its re-emergence from the Aware of earth.

Whilst the moon, however the sun may illuminate it, always shows the earth dweller the same much-sung crooked face, the other way round, the earth offers it an ever changing appearance. Sometimes the pole with the silver cap of the eternal ice turns towards him, sometimes the flanks in constant change, the picture changes from hour to hour; A full earth is never like the previous or the following, and the two quarters are still less alike. This picture is probably a colored one, insofar as the seas want to appear pale blue-green and the continents in different colors. In addition, the picture changes with the seasons; the polar ice belt expands or contracts, and if not a faint hue of color, then a diminished light intensity distinguishes a zone of the earth in its summer splendor from its winter picture. Often, when clouds roll over entire circles of the earth, all drawing disappears under a dazzling shimmer of fog. This radiant glow will hardly be able to considerably lessen the terrible cold of the long moonlit night.Sinking perhaps more than a hundred degrees Celsius below zero, the temperature rises on the following day, during its three hundred and fifty hours of sunshine, perhaps to a degree at which lead and bismuth would melt, and this sharp alternation has perhaps the most prominent part in the cracks and possible changes on the moon, as one claims to have observed them, without, however, being completely certain of this fact.

Of all the natural spectacles that could make an observer enchanted by the moon forget the desolation of his surroundings, that of a total solar eclipse, which on earth is seen as a lunar eclipse, would be the greatest. When the sun goes behind the earth, its huge black sphere will, depending on the moisture content of the air, surround it with a more or less brilliant, golden-yellow to dark purple-red halo, probably flaming in these colors alternately, as if it were bordered with gold and rubies would. This phenomenon, which then, as an exception, floods the lunar landscape with colored light, will present certain phases during the long duration of these eclipses, provided that the ring of light will be brightest where the sun has just disappeared behind the earth or wants to emerge. The authors have tried to show their readers this spectacle, the entrance of which has sometimes been recognized from the earth in the strong reddish shimmer of the darkened moon, in a color table, and believe, despite its beauty, that the painting falls far short of reality would like to. It is, if one will, a morning and evening red thrown from the earth to the moon, an alpine glow, for which the moon mountains of our atmosphere are obliged. The sight of a solar eclipse of the earth from the moon would be much less important. A round black nightspot, surrounded by a penumbra, then hurries quickly over the illuminated, mighty silver disk of the full earth. Since the long shadow brush, which leads this spot over the earth, after Kepler represents the jetty to be used in a hurry, on which lunar tourists can get back to their home earth, so we call out a quick farewell to the moon and suddenly recommend each other.


  1. The moon, viewed as a planet, world and satellite. Authorized German edition. With explanations and additions by. H. J. Small. With numerous woodcuts, two lithographs and nineteen plates in collotype. Leipzig, Leopold Voss 1876.

Annotations (Wikisource)