274 The Outline of Science 



of energy, and their motion is not stopped until that field of 

 energy disappears from the ether. The modern theory of mag- 

 netism supposes that all magnetism is produced in this way. All 

 magnetism is supposed to arise from the small whirling motions 

 of the electrons contained in the ultimate atoms of matter. We 

 cannot here go into the details of the theory nor explain why, for 

 instance, iron behaves so differently from other substances, but 

 it is sufficient to say that here, also, the electron theory provides 

 the key. This theory is not yet definitely proved, but it furnishes 

 a sufficient theoretical basis for future research. The earth itself 

 is a gigantic magnet, a fact which makes the compass possible, 

 and it is well known that the earth's magnetism is affected by 

 those great outbreaks on the sun called sun-spots. Now it has 

 been recently shown that a sun-spot is a vast whirlpool of elec- 

 trons and that it exerts a strong magnetic action. There is 

 doubtless a connection between these outbreaks of electronic 

 activity and the consequent changes in the earth's magnetism. 

 The precise mechanism of the connection, however, is still a 

 matter that is being investigated. 



ETHER AND WAVES 



Ether and Waves 



The whole material universe is supposed to be embedded in 

 a vast medium called the ether. It is true that the notion of the 

 ether has been abandoned by some modern physicists, but, 

 whether or not it is ultimately dispensed with, the conception of 

 the ether has entered so deeply into the scientific mind that the 

 science of physics cannot be understood unless we know some- 

 tiling about the properties attributed to the ether. The ether 

 was invented to explain the phenomena of light, and to account 

 for the flow of energy across empty space. Light takes time to 

 travel. We do not see the sun rise until eight minutes after it 

 has risen. It has taken that eight minutes for the light from the 



