356 GENERA SCIENCE 



any later studies in Astronomy. In estimating distances in 

 degrees on the surface of the sky, it is helpful to remember 

 that from the south point of the horizon to either east or 

 west points, or to the zenith, is 90. The diameter of the 

 full moon is about J^, and the distance between the 

 "pointers" in the bowl of the "Big Dipper", by means of 

 which the North Star is readily located, is about 5. 



The full moon is always on the side of the earth opposite 

 the sun. In winter-time the sun rises far to the south of east, 

 and sets far to the south of west. This is because the north 

 pole of the earth is then tipped away from the direction of 

 the sun. It follows that the rising of the full moon at sunset 

 will be far northward of the east point of the horizon. By 

 reason of the earth 's motion of rotation the diurnal circle of the 

 full moon then will be high up in the heavens, and down to a 

 point of setting far northward of the west point of the hori- 

 zon. This occasions the long and very bright moon-lit 

 nights of midwinter. These are in marked contrast with 

 those of summer when the path of a full moon across the 

 heavens is much lower toward the south, and the light of 

 the moon much less intense because of the greater obliquity 

 of its rays. To attempt to reason out what must be true of 

 natural phenomena such as these requires always the check of 

 actual observation at every opportunity till one is assured 

 that his conclusions accord with the facts. Acquiring a 

 clear understanding of the phenomena presented in the 

 changing positions of the moon, and verifying one's concep- 

 tions by repeated observations, enables one to catch some- 

 thing of the spirit of the scientist as he seeks to master what 

 has hitherto been unknown. 



In many respects the moon itself is an uninteresting sub- 

 ject for study. Astronomers have been unable to detect any 

 evidences of life upon it, or to note there the physical condi- 

 tions essential to life like that known here on the earth. 



