2O2 Trees, Stars, and Birds 



around. Will the ant be able to see the star during the 

 whole rotation? Will any other stars remain visible 

 during an entire rotation? Will any stars be visible 

 during the greater part of the rotation but not through 

 all of it? 



The celestial equator is where the plane of the earth's 

 equator, if extended, would meet the celestial sphere 

 or sky (page 174). It is midway between the north 

 and south poles of the heavens; that is, midway between 

 the points where the earth's axis, if extended, would 

 meet the celestial sphere. At the beginning of spring, 

 March 21, and the beginning of autumn, September 23, 

 the sun is on the celestial equator and the days and 

 nights are equal. During the spring and summer the 

 sun is north of the equator and the days are longer, for 

 it remains above the horizon more than half the time. 

 Stars still farther north remain above the horizon 

 during the greater part of the twenty-four hours. Can 

 you tell how far north they must be not to set at all? 

 How far north would you have to be to see the sun at 

 midnight? Do not think that the answers to the last 

 two questions are the same. 



