THE UNIVERSE IN WHICH WE LIVE 5 



are sources of energy in the sun comparable to that of radium, 

 which we know can give off energy rays for a very long time 

 with scarcely an appreciable diminution of weight. 



The outer layers of the sun, at least, are highly incandescent 

 gases filled with liquid particles. Possibly the central portions 

 are liquid. The intense heat makes volcanic activity and 

 storms exceedingly violent on the sun. Explosions carry flames 



FIG. i. The corona of the sun. Photographed at Matheson, Colorado, 

 June 8, 1918, by Edison Pettit, of Yerkes Observatory. 



out from its surface to a height of 200,000 miles or so, with veloci- 

 ties as great as 600 miles per second. Indeed, some of the impal- 

 pable dust and gases seem to be forced up to very much greater 

 height, and appear as streamers running far out into space. 

 These are seen well at times of eclipse, when the intense glare 

 of the sun's surface is hidden behind the moon, and they form 

 what is known as the corona (Fig. i). 



