IS THERE LIFE IN OTHEE WORLDS? ' 



By H. Spencek Jones, F. R. S. 

 Astronomer Royal, Royal Ohservatory, Greenunch 



[\Yith 5 plates] 



One of the results that hfis f ollo^ecl from the employment in astron- 

 omy of larger and larger telescopes is a clearer recognition of the 

 vastness of the universe. We see our Sun as an average sort of star, 

 eccentrically situated in a disk-shaped stellar system containing some- 

 thing like 100,000 million stars and of such great extent that light 

 takes more than 100,000 years to travel from one end of it to the other. 

 The depths of space are peopled by myriads more of such systems, not 

 differing greatly in size and general structure, at an average distance 

 apart of the order of 1 million light-years. With long exposures on 

 fast plates under good conditions, the 100-inch telescope can just reveal 

 such systems at a distance of 500 million light-years. Within a sphere 

 of this radius there are about 100 million systems, yet there is no indi- 

 cation of any thinning out in the distribution at the extreme limit to 

 which the largest telescope can reach. 



IS THE EARTH UNIQUE? 



The universe being on so vast a scale, the question is inevitably sug- 

 gested whether life is to be found elsewhere than on our own little 

 Earth. Is the Earth unique in the whole of creation? I think that 

 most people would find it difficult to believe that this can be so; for 

 there to be but one home of life in the great universe seems such a waste 

 of creation. 



What has astronomy to say on this question? Though it does not 

 provide a definite answer, we can get some evidence that at least sug- 

 gests what the probable answer should be. It is not possible to discuss 

 the question, however, without making certain assumptions. Suppose, 

 in the first place, we could prove that there were other worlds where 

 conditions resembled generally those on the Earth. Life could exist, 

 of course, on those worlds but would it be legitimate to assume that, 

 just as life has somehow come into existence on our own Earth, it 



I Reprinted by permission from Discovery, n. s., vol. 2, No. 10, Jan. 1939. 



145 



