266 ELEMENTS OF GENERAL SCIENCE 



only about one eighth of an inch. This serves also to indicate 

 how far we are from the sun. 



When the distance of the earth from the sun was known, 

 it was easy to find the sun's actual diameter. The meas- 

 urements which have been made show that its diameter 

 is 866,000 miles. This meahs that the volume of the sun 

 is more than a million times that of the earth. In fact, if 

 the earth were placed at its center, a tiny particle compared 

 to the immense sun, and if the moon were revolving around 

 it just as it does at present, the moon would be less than 

 half the distance to the surface of the sun. It would take 

 330,000 bodies such as the earth on which we live to make 

 one body as great in mass as our sun. 



269. Source of the sun's heat. It follows from the enor- 

 mous amount of light and heat energy received from the 

 sun that the amount radiated by this great body must be 

 beyond our imagination. The earth as seen from the sun 

 would be a point in the sky and would intercept only 

 6lT6"tf3ozrtf7 f ^ e amoun t of light the sun radiates. It 

 is found upon computation that every square yard of the 

 sun's surface is giving off energy at the rate of about 70,000 

 horse power. Its temperature, therefore, is so high that we 

 have no adequate means of understanding it, though we 

 can approximate its measurement. The temperature of the 

 sun has been computed and shown to be about 10,000 F. 

 at the radiating surface ; and the interior is certainly much 

 hotter. This temperature is approximately twice as high as 

 can be reached in the most powerful electrical furnaces so 

 far constructed. 



270. Storms on the sun. The sun's surface is disturbed 

 by the most violent storms (fig. 131), as might be anticipated 

 from its great mass and extremely high temperature. Some 

 of these storms produce what are known as sun spots, which 

 in appearance are black spots ranging from a few hundred 

 miles to fifty thousand miles across. 



