196 GETTING ACQUAINTED WITH THE STARS 



made up of stars of varying brightness. We could see stars varying 

 from the 1st to the 10th magnitude. I must have counted at least 

 30 first magnitude stars, the brightest of them all was Betelgeuse. 



PROBLEM II. WHY DO THE STARS APPEAR TO MOVE? 



The Earth Is Moving through Space. We must go back 

 to our geography to answer this question. The earth is a 

 nearly spherical body which rotates on its axis once in every 

 24 hours. We also know that it revolves around the sun 

 once every year. If we think of the size of the earth and 

 remember that it is about 25,000 miles in circumference 

 at the equator, we may imagine a city there whirling 

 around the earth's center at a rate many times as fast as 

 the fastest mail plane can travel. If we bear in mind 

 the rotation of the earth on its axis, we can understand 



The fact that the earth is revolving is shown in this photograph. The fixed stars 



make trails on the plate. Can you locate the position of the polar star ? In what 



hemisphere must this photograph have been taken ? 



