3 68 



GENERAL SCIENCE 



The table below gives for purposes of comparison the 

 diameters of the eight planets, and the times required by 

 them for one revolution about the sun (their year periods) : 



The astronomer considers our sun as a star, and the stars as 

 so many suns. The little heat and light received on the 

 earth from the stars results from their enormous distances. 

 Many of them must be vastly larger than our sun. If any 

 of them have planets circling about them, these planets 

 must remain invisible because of the distances involved 

 (page 366). Even from Neptune the light is too feeble to be 

 made out by the naked eye, although it is approximately 

 only thirty times the sun's distance from the earth, and 

 consequently is but 30 X 499 light-seconds (or 4 light-hours) 

 away as contrasted with 4 light-years for the nearest star. 



Astronomers believe, too, tiiat our sun with all its attend- 

 ant planets, asteroids, and satellites, is moving onward 

 through space more or less free of the controlling influence of 

 other celestial bodies. This independence in motion is true 

 of all the stars, but so vast are the celestial spaces that colli- 

 sions, though possible in long periods of time, are unlikely. 

 The theories given in Astronomy of the structure of the 

 Universe, as well as of the origin of our Solar System, merit 

 the thoughtful consideration of all students. 



SUMMARY 



So distant are many of the stars that their light is too faint to affect 

 the eye sufficiently for them to be seen. The great telescopes are as it 

 were enlarged eyes, gathering up a far greater amount of light than 



