LIFE IN SPACE AND TIME 3 1 



known universe is probably to be counted by thousands, 

 and may be as great as a million. In how many of these 

 inteihgent life may exist we are hardly able to conjecture, 

 but there is no reason for supposing that our world is unique 

 even in this respect. 



Only one characteristic remains by which our system 

 and our world are likely to be distinguished. It is not at 

 all improbable that a world but a few billions of years 

 old may be the youngest of all. Indeed, encounters, under 

 present stellar conditions, should be so rare that it appears 

 improbable that even one should have happened, anywhere 

 among the stars so recently. However, as Eddington puts 

 it, these few billions of years may be "the interval between 

 the event itself and a direct consequence of this event 

 (viz. the evolution of beings capable of speculating about 

 it.)" Compared with the inhabitants of the older worlds, 

 our race may be primitive indeed. 



REFERENCES 



Eddington, A. S. 1927. Stars and Atoms. New Haven, Yale Univ. Press. 

 An admirably written popular account of recent astrophysical work. 

 1926. The Internal Constitution of the Stars. Cambridge Univ. Press. 



Henderson, L. J. 1913. The Fitness of the Environment. N. Y., Macmillan. 

 1917. The Order of Nature. Cambridge, Harvard Univ. Press. Lucid discus- 

 sions of the general physical and chemical conditions which make life 

 and evolution possible. 



Jeans, J. H. 1919. Problems of Cosmogony and Stellar Dynamics. Cambridge 

 Univ. Press. 



Jeffreys, H. 1924. The Earth. Cambridge Univ. Press. 



Russell, H. N., Dugan, R. S. and Stewart, J. Q. 1927. Astronomy. Bost. 

 Ginn, 2 vols. A general text book dealing more fully with most of the 

 matter here mentioned. 



