HOW FAR AWAY ARE THE STARS? 191 



The light by which we see Aldebaran today left that star 44 years ago, and we 

 apparently see it as the upper star. But in that time the star has moved many 

 miles and it is really at a point 55 billion miles away from the place where we 



appear to see it. 



it travels about 6,000,000,000,000 miles, so that it takes 

 a little over 4 years for light from the nearest star to reach 

 us. The distance light travels in one year is called a 

 light year. This is the astronomer's yardstick or a way 

 of measuring distances. When the astronomer tells 

 us that there are probably many hundred thousands of 

 light years separating us from some of the more distant 

 stars, we can see that the distance of the stars from the 

 earth varies greatly. 



Distances to the Stars Are Enormous. There have 

 been many comparisons devised to make the enormous 

 distances to the stars understood. None of them help 

 very much, but that of Dr. Brashear, at one time a famous 

 lens maker of Pittsburgh, is at least interesting. In the 

 eyepiece of many telescopes a "cross hair" is used. This 

 had to be finer than any thread. Even the fiber of the 

 ordinary spider web is too coarse, but the mother spider 

 spins a very fine and delicate fiber to make the cocoon 

 which protects the young. These fibers were used by 

 Dr. Brashear in his telescope, and he became interested 

 in calculating how far so thin a fiber could reach. A pound 

 of it would circle the earth at the equator and ten pounds 

 would make enough fiber to reach the moon. How much 

 of this fine fiber would be required to go to the nearest 

 star 4 light years away? By Dr. Brashear's calculation 



