The music of the spheres

by Florence Armstrong Grondal

The Leibnitz and the Doerfel mountains are on the southern part of the moon near the pole. These mountains are so situated that the light of the sun always shines from their summits, and even during an eclipse they are visible in profile. Some of the peaks on these "mountains of eternal light" are very high, their needle-like points reaching upward for 26,000 to 27,000 feet. It has been estimated that if our mountains on earth were comparatively as high as the mountains on the moon, our earthly mountains would rise to the height of about 15 miles! The height and sharpness of the moon mountains is due partly to the low surface gravity, which is only about ⅙th that of the earth, and to the fact that there is no leveling influence such as is caused by frosts and rains.

Isolated mountains rising up like a huge lump, or a pen point, from a flat surface, are commonly found on the moon. These often stand several miles high and are particularly interesting as seen in the northern hemisphere of the moon, when the long shadow of such a solitary mountain stretches in inky-blackness against the smooth gray plain. Several of these may be seen in Mare Imbrium just above the crater Plato, the loftiest of which is Pico, rising about 8000 feet. Isolated mountains are very frequently found in the center of craters. This would seem a strange formation close at hand—a large crater, or a ringed plain, miles in extent, with a tall slender mountain standing in its center.

The oddest and most common mountains, however, are the circular mountains which surround a plain or a large sunken cavity, like a mighty wall. Such mountains appear on almost every part of the moon's surface and in some places they appear in such profusion that their rings frequently touch and even overlap one another. The peaks of the circular mountains are often two or three miles in height and their shadows sometimes cover a large portion of the plain which they surround. These shadows are continually varying, for during the increase of the moon they are thrown in one direction and during the decrease, in the direction exactly opposite. During full moon they disappear altogether and the plains are filled with light, but lunar scenes are much more interesting when the sunlighted portions are accentuated by the long, queer shadows, for these shadows are black and clear-edged and stand out like silhouettes done in ebony, even at this distance of 240,000 miles. Because they have no light reflected into them from an atmosphere, these shadows are actually so densely black that if one stepped into such a shadow he would instantly be blotted from view.

On account of the vividness of the shadows, moon-mountains are best observed during the first and last quarter of the moon. A good time to begin observing with a glass is when the moon is a narrow crescent in the western sky.

The most prominent object in the narrow crescent is the Mare Crisium or the Sea of Crises, 380 miles long. South of Mare Crisium is Mare Fecunditatis, the Sea of Fecundity and Mare Nectaris, the Sea of Nectar. When these three "Seas" are visible with Mare Tranquillitatis just coming into view, the moon is between 5 and 6 days old, that is, 5 or 6 days after new moon. The Leibnitz mountains may then be seen near the southern pole. Watch carefully evening after evening as the light creeps over new regions and brings them into view. The best place to select for observation is the boundary line between the illuminated and unilluminated portions, called the "terminator," for the shadows that are cast make the irregular features stand out more distinctly and bring out the individual beauties of the lunar scenes. Since we are looking down upon the moon, a mountain peak, at this distance, resembles a point of light, and a mountain range whose base is still in the shadow, but whose peaks are lighted by the rays of the sun, a straight or curved row of lights. Besides beautifying the country of the moon and revealing to us the peculiar sharpness of the mountain peaks, the shadows have proved of great practical value to astronomers, for by measuring the length of their shadows, the heights of the mountains are calculated.

THE CRATERS ON THE MOON

Craters are so numerous in some localities on the moon that one might walk for hundreds and hundreds of miles and step on nothing but crater rims. On the earth a crater is usually a rare object situated on the top of a mountain, but on the moon they are scattered all over the lunar plains, a state of landscape which permits of no short cuts. If, however, in the dim, distant past, life had ever developed on the moon, a moon-being would have been %th as heavy and able to jump six times as high as an earth-being for the surface gravity of the moon is only about ⅙th that of the earth. Thus if a lunarian had no other mode of transportation, he might at least have been able to surmount many of the minor obstacles by jumping over them.

A map of the moon resembles a big mud-ball with all the little pebbles picked out.