MOON 



3940 



MOON 



States and Canada a temperature of 50 below 

 zero is considered almost the limit of human 

 endurance. Polar expeditions have failed and 

 brave men have been exhausted and frozen to 

 death at a temperature of 69 below zero. If 

 there is life on the moon, that life, whether hu- 

 man, animal or vegetable, must be different 

 from life on the earth. If water exists on the 

 moon, it must be in the form of ice and if there 

 is any air present it cannot exceed in pressure 

 1/750 part of the pressure of the earth's atmos- 

 phere. The moon is perhaps the most studied 

 object in the heavens; more things can be 

 definitely proved concerning it and its motion 

 than concerning any other planet, but there is 

 not yet built a telescope that can detect any 

 cloud or atmospheric effect on or surrounding it. 



Weight on the Moon's Surface. The attrac- 

 tion of the moon is only one-sixth of that of 

 the earth. An apple, or other object, dropped 

 from a height above the earth will travel to- 

 wards the earth at the rate of 16.08 feet the 

 first second (see FALLING BODIES). If dropped 

 above the surface of the moon it would travel 

 only at the rate of 2% feet the first second. A 

 strong man on earth who can easily lift and 

 raise a 56-pound weight over his head with one 

 hand could perform the same feat on the moon 

 with a weight of 336 pounds. The record high 

 jump of earthly athletes would be broken by 

 the merest amateurs, who in the atmosphere of 

 the moon would be able to jump 20 feet as 

 easily as one on earth can step on or off the 

 street pavement. 



Its Light. At the full moon the light re- 

 flected by it is just 1/600,000 part of the light 

 of the noonday sun. The surface of the moon, 

 viewed from the earth, appears white, but in 

 reality it is a light gray, in places darkened to 

 the color of seasoned sandstone or slate. The 

 light reflected from it to the earth has passed 

 through two stages, or, perhaps, atmospheres. 

 From the sun to the moon the light travels di- 

 rect; the light is then deflected towards the 

 earth in volume according to the relative posi- 

 tion of earth and moon. The light of the moon 

 is simply modified sunlight which has under- 

 gone only such changes as are caused by reflec- 

 tion. The moon occupies a curious position in 

 the solar system. It rotates on its own axis, 

 also revolves round the earth, and with the 

 earth revolves round the sun. The same face, 

 or side, of the moon is always turned toward 

 the earth. The light of the small crescent of 

 the new moon is much less than the light of 

 the full moon because^the new moon is at such 



an angle that the light of the sun is reflected 

 only from a small portion of the moon's surface. 



Motion. The orbit, or path, of the moon 

 round the earth is elliptical, but constantly 

 changing in its form. The line of apsides, or 

 points of least and greatest distance from the 

 center of motion, continually changes, perform- 

 ing a complete revolution in a little less than 

 nine years. The motion of the moon is eccentric. 

 One night it appears to be very close to some 

 particular star, but the next night far to the 

 east of that star, changing its position about 

 13 daily. At the time of the new moon the 

 distance between sun and moon is at the low- 

 est, and the moon is said to be in conjunction; 

 at the full moon it is farthest away from the 

 sun, and is in opposition. In its motion the 

 moon is continually oscillatory, constituting 

 what are called librations. Owing to these li- 

 brations we see really more than half of the 

 moon's surface. Cfeily 41 per cent of the moon 

 is never visible to Its and a belt of about 18 per 

 cent at the edge of the moon is alternately visi- 

 ble and invisible, owing to the oscillation. 



Craters. Studied through a telescope the sur- 

 face of the moon appears to be marked with 

 craters of extinct volcanoes, some of them hav- 

 ing walls of 20,000 feet in height. Volcanoes on 

 earth have craters of much less depth, the high- 



IMAGINARY VIEW OF MOON 

 Showing typical crater ring. 



est mountain mass only reaching a height of 

 29,000 feet, the crater occupying a very small 

 portion. The moon is often referred to as a 

 dead planet. Whatever life there ever was is 

 extinct. The moon has grown old; its volca- 

 noes are dead; its s.eas are empty, silent wastes. 

 The volcanoes, in exhausting themselves, have 

 apparently worn out the whole surface of the 

 moon. 



Photography of the Moon. Although modern 

 instruments, especially telescopes of great power, 

 have done much to increase the definite knowl- 



