Page:Popular Science Monthly Volume 91.djvu/272

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What's On the Moon?

Look through the telescope with us and see the great mountains, the vast dead craters and arid wastes of slag

By Scriven Bolton, F. R. A. S.

Illustrations specially prepared for Popular Science Monthly by the author

��SUCH is the power of our largest tele- scopes that a creature as large as an elephant might be detected on the moon. Hence we are more familiar with the lunar surface than with Central Africa. Since there is no appreciable air on the moon, our view is always clear and un- obstructed.

Why has the moon no atmosphere? Simply because the force of gravity is so small. The weight of an object on any planet depends upon the mass of that planet. On Jupiter, the largest of all planets, you would have difficulty in lifting your arm from your side. On the Sun you would probably need a steam crane to help you move about. On Mars you could jump over a small house. Small planets, including the earth, are gradually losing their atmosphere. The smaller they are the more rapid is that rate of loss. And since the moon is very small, it lost its atmosphere long ago. Thus is to be ex- plained the fact that the earth is still wrapped in air although the moon, child of the earth though it is, is airless. Because of this entire absence of air astronomers consider it improbable that there is any lunar life. Perhaps there . may be rem- nants of vegetation within certain low- lying craters and in the deepest valleys and chasms where a few shreds of atmos- phere may still pervade. But nothing of the kind has as yet been detected, and as we gaze in bewilderment into every crack and crevice of the surface we rightly conclude that the moon is a truly barren world.

On Top of a Lunar Mountain

Although we cannot fully realize existence on the moon, it is nevertheless the inevitable experience of the astronomer when tele- scopically raking the lunar surface with what might be justifiably termed an eye of the earth to identify himself to such an extent with the scrutinized scene that he ofttimes unconsciously thinks himself a lunar inhabitant. It really requires but little imagination to suppose oneself actually planted among the lunar craters and

��mountains, viewing in awe the wonderful landscape.

Now let us endeavor to realize, by the help of the accompanying illustrations, that we have taken our stand upon one of the mountain peaks such as we see in these pictures, and by commanding an extended view of the surroundings we duly note the strange lunar conditions produced upon the landscape.

Dawn Is as Harsh as Midday

The lunar day is thirteen times longer than ours. Dawn, in an earthly sense, is unknown, for there is no atmosphere to reflect the solar beams while the sun is yet below the horizon. The terribly harsh solar beams suddenly appear on the black horizon, dazzlingly illuminating the moun- tain crests, while the valleys are still in utter darkness. Because there is no atmosphere, blending of the night into day at sunrise is unknown, and all the gorgeous tints which attend a terrestrial sunrise are on the moon quite absent. On earth we are accustomed to see the sun's light softened by an air screen. The fierce splendor of our luminary on the moon, however, is rendered more obvious by the blackness of the sky, owing to the absence of air. Even in broad sun- shine the sky is as dark as our darkest star- light nights, with the stars and planets shining more brightly than it is possible to see them here. The appendages to the sun, such as the Zodiacal Light, the Corona, and the red protuberances, appear in glorious perfection.

What a magnificent object is the earth, thirteen times larger than the moon appears to us, and practically stationary in the heavens! It exhibits phases precisely as does our moon, the interval between each full "earth" being about twenty-nine days. The sublime and periodical spectacles of a total solar eclipse and an eclipse of the "earth" are attended by circumstances far more imposing than their earthly counter- parts. The spectator sees the earth-globe rotating on its axis, the continents, oceans, and polar snow caps being well displayed. Portions of the surface appear inter-

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