THE SCALE OF TIME 167 



has really been observed is the slowing down of vibra- 

 tions consequent on the light from these objects having 

 travelled an appreciable part of the way round the world. 

 On that theory the radius of space is of the order twenty 

 times the average distance of the nebulae observed, or 

 say 100 million light years. That leaves room for a 

 few million spirals; but there is nothing beyond. There 

 is no beyond — in spherical space "beyond" brings us 

 back towards the earth from the opposite direction.* 



The Scale of Time. The corridor of time stretches back 

 through the past. We can have no conception how it 

 all began. But at some stage we imagine the void to 

 have been filled with matter rarified beyond the most 

 tenuous nebula. The atoms sparsely strewn move hither 

 and thither in formless disorder. 



Behold the throne 

 Of Chaos and his dark pavilion spread 

 Wide on the wasteful deep. 



Then slowly the power of gravitation is felt. Centres 

 of condensation begin to establish themselves and draw 

 in other matter. The first partitions are the star-systems 

 such as our galactic system; sub-condensations separate 

 the star-clouds or clusters; these divide again to give 

 the stars. 



Evolution has not reached the same development in 



*A very much larger radius of space (io 11 light years) has recently 

 been proposed by Hubble; but the basis of his calculation, though con- 

 cerned with spiral nebulae, is different and to my mind unacceptable. 

 It rests on an earlier theory of closed space proposed by Einstein which 

 has generally been regarded as superseded. The theory given above (due 

 to W. de Sitter) is, of course, very speculative, but it is the only clue we 

 possess as to the dimensions of space. 



