The Universe and Solar System 165 



a nighthawk we could not reach them in a thousand 

 years. The sun is a star, no larger or brighter than 

 thousands of others; but it is much nearer to us, and 

 that is why it gives us so much more heat and light and 

 seems so much larger than the other stars. 



The solar system. The earth and seven other worlds 

 or planets, some smaller than the earth, others larger, 

 revolve around the sun (Fig. 108). These are the 

 major planets. The sun controls the motion of several 

 hundred minor planets, which are of much smaller size 

 also, as well as the movements of various comets 

 and a host of meteors. Some of the major planets are 

 attended by satellites that revolve around them as they 

 themselves revolve around the sun. The moon is the 

 earth's satellite, and some other planets have several 

 moons or satellites. 



The sun and all the bodies that revolve around it 

 the planets with their satellites, the minor planets, and 

 the comets and meteors constitute the solar system ; 

 that is, the system of the sun. Whether, like the sun, 

 the other stars have smaller bodies revolving about 

 them we cannot tell. They are so far away that at 

 such distances bodies like our earth would be invisible 

 to us. Yet it would seem reasonable to believe that 

 each star is the controlling center of a great system of 

 worlds like our own. 



The vastness of the universe. The earth on which 

 we live is so large that none of us will ever see more than 

 a small part of its surface, and the vast mass of matter 

 that lies deep in the earth's interior has never been seen 

 by human eye. Yet the earth is but a small member 



