WHY DO THE STARS APPEAR TO MOVE? 197 



why it is that the sun, moon, and stars appear to rise 

 and set. The earth also rushes through space around the 

 sun at a rate of about 1100 miles a minute. If we also 

 remember that we are moving rapidly through space, we 

 can see why constellations do not always appear to be in 

 the same place in the heavens. Those of us who are 

 scouts know that certain groups of stars called constella- 

 tions are visible in the winter and that six months later 

 others have come above the horizon and occupy the places 

 held by those we saw in the winter. The reason for this 

 is evident when we recollect that in the summer our 

 earth is in quite a different place in space than it is in 

 winter. We have moved along to the other side of the 

 sun in a circular path whose diameter is 186,000,000 miles. 



Demonstration 1. How the Rotation of the Earth Causes Stars to 



Appear to Move. 



Hang a large round umbrella in the room so that the supporting 

 rod is in direct line pointing to the North Star. A compass will 

 show you north. There are 90 from the equator to the north 



