80 INTRODUCTION TO GENERAL SCIENCE 



59. DISTANCES OF THE STARS 



The stars are so distant that we must make use of a unit of 

 measurement other than the mile. It would be hard to ex- 

 press these distances in miles, and the numbers would be 

 meaningless. Light travels one hundred and eighty-six thou- 

 sand miles a second. The unit of distance is taken as the 

 space through which light would pass in one year, which is 

 called the light-year. Using this standard of measurement, 

 the nearest star is about three light-years away. Those stars 

 which are just visible to the naked eye are between two hun- 

 dred and three hundred light years distant. The telescopic 

 stars, that is, those stars which can be seen only through the 

 telescope, are so distant that the light from them has been 

 thousands of years on its way to us. When we see some change 

 in a star, or group of stars, we are seeing something which 

 happened several hundreds of years ago. 



References : 



1. 1002 : 504-507. Distances of the Stars. 



2. 1803 : 390. Results of the Finite Speed of Light, 

 a. 1001 : 315. The Unit of Stellar Distance. 



6. 1003 : 209-212. Distances of the Stars. 



c. 1004 : 304-306. Distance of the Stars The Light- Year. 



d. 1301 : 27. Distances of the Stars. 



e. 1303 : 12. Distances of the Stars. 



60. THE EARTH AS A WHOLE 



The surface of the earth is a solid mass of rock, of which 

 only a very thin top layer has been changed to soil and sand. 

 Thus the surface is covered in most places, except where the 

 rocks show through, with a mixture of material ranging in 



