12 OUR PHYSICAL WORLD 



Meztli, and regarded her as the wife of the sun-god. The son 

 of this pair was Inca, their national hero. 



Our moon is not very far away as astronomical distances go, 

 only 238,840 miles. It has a djameter of 2,162 miles. The 

 moon has no atmosphere and apparently no moisture on its sur- 

 face. It is quite thoroughly cooled off, and the surface tempera- 

 tures there are probably 200 below zero, except as the sun's 

 rays heat it at noonday. Its contour is varied with great plains 

 that are quite smooth and seem dark, and with mountainous 

 areas whose numerous peaks reflect the light and so appear 

 bright, just as the numerous facets of salt or snow crystals reflect 

 the light and appear white. These patches of light and dark are 

 arranged so as to suggest the face of the "man in the moon" or 

 the "woman's face/' according to the way one looks at it. 



These imaginary figures have given rise to many fables. 

 According to the Chinese legend, it is the man in the moon who 

 ties together with invisible yet unbreakable cords the young 

 man and maiden who are destined to marry each other. It has 

 been aptly suggested that he must be the man of the honeymoon. 



The moon shines only by reflected light, the sunlight always 

 illuminating the half turned toward it. When the moon is on 

 the opposite side of the earth from the sun we see the illuminated 

 half, and the moon is full. The full moon, therefore, always 

 rises as the sun is setting. When the sun and moon are on the 

 same side of the earth and about in line with it, we do not see the 

 moon at all, for the side turned our way is the dark side. 

 Between these two positions we see first the new moon, just as a 

 narrow rim of light, then more and more of the illuminated por- 

 tion, as the moon proceeds to quarter and on to full. During 

 this time it is waxing more and more brilliant. Then gradually 

 it wanes, passing to third quarter and so on till the old moon 

 disappears. 



The period of time occupied by these changes from new 

 moon to new moon is apparently the original month. The divi- 

 sion of this into four periods or weeks was likely facilitated by 



