THE STORY OF COSMIC RAYS — SWANN 261 



Thus, R. D. Richtmyer and E. Teller have pointed out that on such a 

 view the total energy carried by all cosmic-ray particles is much more 

 than all the energy ever emitted by stars, together with their kinetic 

 energy. In fact, it would be an energy less by only a few orders of 

 magnitude than the total energy (E=mc 2 ) represented by all the 

 matter in the universe. 



Difficulties also arise as to how the supply of cosmic-ray particles can 

 be maintained, since it is necessary to allow for a continual loss as a 

 result of their collisions with atoms in space. 



Such considerations have led to the general concept of an extensive 

 magnetic field confining cosmic radiation to a definite region, a galaxy 

 for example, as just mentioned above. Such a theory removes the 

 necessity of extending the rays to the whole of intergalactic space, and 

 avoids the enormous amount of energy that such extension would im- 

 pute to cosmic rays in the universe as a whole. 



There are three general possibilities to account for the enormous 

 energies of the rays themselves, from 10 10 to as high as 10 17 electron 

 volts : 



1. The particles may receive energy by relatively small forces acting 

 over great distances. 



2. They may receive energy in single acts associated with enormous 

 forces. 



3. The particles, with their energies, might be considered to have 

 been born with the universe, their properties depending upon the cir- 

 cumstances associated with that event. 



The third possibility, first propounded by the Canon Lemaitre, can- 

 not very well be proved or disproved. At the time of the supposed 

 origin of the universe, conditions may have been so drastically different 

 from what they are now that in our ignorance we may assume almost 

 anything to form a basis for the origin of the high energies. 



The second category is deemed unlikely because we now know that 

 the cosmic radiation contains particles much heavier than protons. 

 Quantum theory demands that a process that could give them their 

 energy in a single act would disintegrate them. 



The first category, therefore, presents the natural field for explana- 

 tion in terms of our present knowledge. This category may be divided 

 into two classes, in one of which the energies are acquired little by 

 little by processes that are primarily mechanical, while in the second 

 the forces are primarily electrical. Of course, mechanical forces are 

 usually electromagnetic in the last analysis, but it is convenient to 

 distinguish between processes that are very clearly the result of elec- 

 tromagnetic forces and those in which any electromagnetic feature is 

 involved in more subtle form. 



Mechanical methods. — Thus, in the mechanical realm we have effects 

 of the pressure of light. For instance, L. Spitzer, Jr., has considered 



