OUR PLACE IN SPACE 365 



This evident parallelism of our earthly existence seems the 

 counterpart of the larger parallelism of the cosmic organism. 

 Imaginative minds have not hesitated to conceive of other 

 inhabited planets within our solar system. Mars has been a 

 favourite field of operations for novelists with ultramundane 

 fancies ; Venus may possess physical conditions much closer to 

 those which obtain upon the earth. It may be that both of 

 them, possibly others still, possess life in some form. Circling 

 the infinitude of suns there may be an infinitude of others. 



All the advance of physical knowledge has been, as it were, 

 convergent rather than dispersive that is, it tends always to 

 reveal a single operative cause at work through a variety of 

 phenomena. The analogy irresistibly suggests that if we ever 

 attain to an extended knowledge of cosmos, it will be found 

 to be relatively simple, following much the same course of 

 development, and built on much the same pattern. 



The quantitive measure may vary vastly. There is nothing, 

 for example, to forbid our believing that each of the five hundred 

 asteroids known to us may not have been one day, or may 

 not one day be, the theatre of life in some degree. There is 

 nothing to forbid our believing that the sun itself may one 

 day become habitable. We do not as yet know what are the 

 relative probabilities in the approach of the suns as to whether 

 they shall collide or go spinning one about the other as a binary 

 system, like unto those with which the heavens seem filled. 

 The latter might be the fate of our sun, or it might become 

 satellite to some vast luminary like Canopus. If in either 

 instance it were supplied with an exterior source of heat and 

 light, life would undoubtedly develop at some stage or other 

 of its cooling. 



If the density of the asteroids be something the same as 

 that of the earth, it is evident that the pull of gravity at their 

 surfaces would be twenty or thirty times less, even among the 

 largest of them. If the sun in cooling reaches the same density 

 that is to say, is reduced to one- fourth its present volume 

 the pull of gravity at its surface would be fifty times or more 

 that upon the earth. It is evident that within our own system 

 the physical conditions for the development of life would be 

 extremely diverse. A being the size of an average man set 

 upon an asteroid might "weigh" six or eight pounds. This 

 same body set upon the sun grown cold might weigh four tons. 



