124 Common Science Y 



from the sun that we should not know there was such 

 a thing. 



But even if we filled the space between us and the sun 

 with copper or silver, which are about the best conductors 

 of heat in the world, it would take the heat from the 

 sun years and years to be conducted down to us. Yet 

 we know that the sun's heat really gets to us in a few 

 minutes. This is because heat can travel in a very much 

 quicker way than by conduction. It radiates through 

 space, just as light does. And it can come the whole 

 93,000,000 miles from the sun in about 8 minutes. This 

 is so fast that if it were going around the world instead 

 of coming from the sun, it would go around yi times be- 

 fore you could say " Jack Robinson," -really, because 

 it takes you at least one second to say " Jack Robinson." 



We are not absolutely sure how heat gets here so fast. 

 But what most scientists think nowadays is that there 

 is a sort of invisible rigid stuff, not made of molecules 

 or of anything but just itself, called ether. (This ether, 

 if there really is such a thing, is not related at all to 

 the ether that doctors use in putting people to sleep. 

 It just happens to have the same name.) The ether is 

 supposed to fill all space, even the tiny spaces between 

 molecules. The fast moving particles of the sun joggle 

 the ether up there, and make ripples that spread out 

 swiftly all through space. When those ripples strike 

 our earth, they make the molecules of earth joggle, 

 and that is heat. The ripples that spread out from the 

 sun are called ether waves. 



But the important and practical fact to know is that 

 there is a kind of heat, called radiant heat, that can 



