Celestial Bodies 155 
THE SUN 
The Sun is the central body of the solar system about which 
all of the previously mentioned bodies revolve. It is a fiery 
ball 800,000 miles in diameter—one hundred times the diam- ' 
eter of the earth, one million times the earth’s volume. The 
material which composes the sun is different from matter as 
we know it on earth because of the high temperatures and 
pressures which prevail. 
THE PHYSICIST SAYS 
Atomic physics teaches us that matter_is made up of atoms, 
each of which is a complex system of electrons and protons 
(elementary negative and positive electric charges) re- 
volving about one another in well defined orbits. Under high 
temperatures and pressures such as those on the sun, these 
_ atomic systems are partially disrupted or disturbed, electrons 
~ 
are torn from the outer orbits, or the orbits themselves are 
changed from their normal unexcited state. The atoms of 
matter on the sun are continually disrupted, excited, and 
then reform themselves again, a process which results in the 
tremendous pouring out of light and heat from the sun. What 
the ultimate source of all the sun’s energy is, is as yet not 
completely understood, although recent investigations in 
so-called nuclear chain reactions have been suggestive of 
possible processes sufficiently powerful and long-lived. The 
entire heat radiation of the sun is five hundred and eight 
sextillion horsepower. To give an idea of the staggering size 
of this number, and the immense power it signifies, we may 
state that this power is enough so that with it every man, 
woman, and child on the earth could operate continuously 
one hundred billion medium sized steamships of 2500 horse- 
