388 ANNUAL. EEPORT SMITHSONIAN INSTITUTION, 1910. 



passing near. However this may be, it must be conceded that in 

 collision and close approach lie possibilities of ultimate disruption to 

 the solar system and disaster to our earth. 



But here, as in other vital issues, the degree of danger is deter- 

 mined by the time elements involved. How imminent is this liability 

 to disaster? 



The distances between the stars are so enormous that the contin- 

 gencies of collision or disastrous approach are very remote. Although 

 nothing but rough computations can be made, and even these must 

 be based on assumptions whose validity is open to doubt, the chance 

 of a given sun or planetary system falling on disaster from collision 

 or close approach seems to be of some such order as once in some 

 few billions of j'ears. There is no star whose nearness to us or whose 

 direction of motion is such as to appear to threaten the earth at any 

 specific time in the future. There is only the general theoretical 

 possibility or probability when time enough is allowed. 



"While, therefore, there is to be, with little doubt, an end to the 

 earth as a planet, and while perhaps previous to that end a state in- 

 hospitable to life may be reached, the forecast of these contingencies 

 from the point of view herein taken places the event far ahead in the 

 indeterminate future. The geologic analogies give fair ground for 

 anticipating conditions congenial to life for millions or tens of mil- 

 lions of years to come, not to urge the even greater possibilities. 



This answer to the question of the future habitability of the earth, 

 even if the conditions remain congenial to man, does not necessarily 

 carry the actual realization of the future opportunities thus open to 

 our race. Congenial conditions granted, there still arise questions as 

 to man's continued biological adaptation, as to the tenacity of his 

 vital powers and as to the consequences of his own choices of action. 

 If an appeal be made to the record of the animal races for an argu- 

 ment from analog} 7 , it is easy to find some cases of marvelous endur- 

 ance and some cases of very short records, while the majority fall 

 between these extremes. Many families of animals persisted for 

 millions of years, and the average record known to us is much greater 

 than the record already made by man. On historical grounds, then, 

 a long career can not be denied to man — neither can it be assured. It 

 is an individual race problem. It is a special case in the problem of 

 races in the largest sense of the term. 



In distinction from the animal races, two new factors of deep 

 import enter into the problem of human endurance, one the power 

 of a definite moral purpose, and the other the resources of research. 

 No previous race has shown clear evidence that it was guided by 

 moral purpose in seeking ends not immediately before it and not 

 connected with its physical requirements. In the human race such 

 moral purpose has risen into a declared distinctness. As it grows 



