SUMMARY. 133 



bodies can be driven from each other as a consequence of tidal friction, 

 this maximum distance corresponding to a minimum of energy, and that 

 this maximum distance is not many times greater than the distance im- 

 mediately after separation. In particular, when the equations were applied 

 to two stars each equal in mass and dimensions to the sun at an initial 

 distance between centers of 866,000 miles, it was found, on the basis of 

 conclusive reasoning, that the greatest distance possible as a result of tidal 

 evolution would be only 1,042,400 miles. These results, which were ob- 

 tained under the hypothesis that the stars suffered no shrinkage with loss 

 of heat, were not radically modified when they were supposed to shrink to 

 any extent whatever. The conclusion is that the widely separated binaries 

 which our telescopes reveal to us can not have originated by fission, at least 

 from masses condensed beyond the nebulous stage.* 



In a word, the quantitative results obtained in this paper are on the whole 

 strongly adverse to the theory that the earth and moon have developed 

 by fission from an original mass, and that tidal friction has been an impor- 

 tant factor in their evolution. Indeed, they are so uniformly contradictory 

 to its implications as to bring it into serious question, if not to compel us 

 to cease to consider it as even a possibility. 



1 This of course refers only to spontaneous fission without the accession of moment of 

 momentum from some outside body. 



