PHYSICAL BACKGROUND OF EVOLUTION I3 



thermodynamics that through the degradation of energy, 

 running downhill to a final heat death, the universe will 

 eventually die. 



For many, speculation concerning the cosmos is fascinat- 

 ing. The cosmologist, amateur or professional, is awed by 

 the vast sweep of the star systems, the inconceivable dis- 

 tances, the gigantic proportions, and the organization that 

 does appear out of what at first seems to be a star-scattered 

 chaos. A review of theories concerning the stars and their 

 history, however, is very liable to be confusing because of 

 the great differences of opinion among the astronomers 

 who concern themselves with this problem. The fact is that 

 the "riddle of the universe" is still very much a riddle. Mod- 

 em equipment like the great 200-inch reflector at Palomar 

 and, above all, the new giant radar telescopes hold real 

 promise for a future solution. But let us briefly review some 

 theories that are tentatively held in our day. 



Even the problem of the origin of one of the "cosmic 

 pebbles" we call the planets is diflicult, for, an examination 

 of the earth itself gives little information except that the 

 ground substance is common to the universe. The origin 

 took place in the remote past, not less than 3,000,000,000 

 years ago, a period of time that is only a little less than the 

 age of the universe in its present form. Theories are not 

 lacking, but possibly none is entirely satisfactory. In the 

 eighteenth century Buffon led off by finding place in one 

 of his more than two score volumes of the Histoire naturelle 

 for a description of the formation of the solar system as the 

 result of a collision between the sun and what he called a 

 "comet," meaning, however, a large soHd body. He thought 

 that this collision engendered various-sized bits of stellar 

 matter which were thrown off at the moment of impact to 

 form the planets, all set in motion in the same plane and in 

 the direction of the sun's rotation about its own axis. 



In 1796 Laplace criticized Buffon's views and proposed 

 the theory that the planets were produced by the sun itself as 



