16 



THE OPEN SKY 



depressions, some of which are more than 100 miles in 

 diameter. 



Although we see the moon as a very bright object at night 

 for a part of every month, yet it has no light of itself, and 

 all the light it gives us is reflected from the sun. Astronomers 

 tell us that we receive more heat and light from the sun in a 



quarter of a minute 

 than from the moon in 

 a whole year. 



As the earth goes 

 around the sun and 

 the moon around the 

 earth, the position of 

 these three in relation 

 to each other is con- 

 stantly changing. It is 

 profitable to try to 

 picture to oneself the 

 changing phases of the 

 moon. Study the dia- 

 gram of the moon's 

 phases, and see what 



the relative positions of the sun, earth, and moon are from 

 the new moon to the dark of the moon. 



It must sometimes happen that >the moon comes directly 

 between the earth and the sun. The moon is so much 

 smaller than the earth, however, that it does not cut off 

 the face of the sun from the whole surface of the earth, but 

 merely from a comparatively narrow path. For hundreds 

 of miles on each side of this path of total eclipse of the sun, 

 observers see a partial eclipse. It is during a total eclipse 

 that the pictures of eruptions of incandescent gases on the 



TOTAL ECLIPSE OF THE SUN 

 From a photograph taken June 8, 1918. 



