14 FIRST YEAR COURSE IN GENERAL SCIENCE 



Not until about five hundred years ago did any one 

 suspect that the earth was like a globe or that it moved. 

 More has been learned about the earth since the days 

 when Columbus repeated to his timid captains the order, 

 "Sail on," than had been learned in all the time before. 

 Since that wonderful voyage, men have traveled over land 

 and water around the earth and back to the place from 

 which they started. They have found that there is no 

 "edge," and that at no point does the earth rest upon or 

 touch any other body. 



We know that there are other bodies, for when we look 

 away from tfhe earth, we see many luminous or light- 

 giving points, and we see two bodies whose shape we can 

 determine. Men have been watching and studying these 

 bodies for thousands of years. The ancients learned 

 much that was interesting about them. Modern ob- 

 servers have learned infinitely more, and there is still a 

 great deal to be learned. Some bodies are known to be 

 entirely unlike the earth; a few are in some respects similar 

 to the earth; but there has never been found any body in 

 external condition exactly like^the earth. 



The place where these luminous bodies seem to be is 

 called the sky, or the heavens, and the bodies are called the 

 heavenly bodies. The sky looks like the inside of a great 

 dome, where in the daytime we usually see but one bright 

 body, the sun, which to us is by far the most important of 

 all the heavenly bodies. At night we see stars, planets, the 

 moon, and occasionally a comet, meteors, and shooting stars. 



2. The Number of the Stars. The stars are the most 

 numerous of the heavenly bodies, but it is not strictly true 

 to say that the number visible to us is countless. 



In the whole sphere of the heavens, there are only about 

 7,000 stars bright enough to be seen without a telescope on 

 a clear, moonless night. Half of that number are in the 

 part of the sky that is visible to dwellers in the northern 



