THE STRUCTURE OF THE UNIVERSE 395 



This is a first fact. The swarms of meteors is a second. 

 Space is teeming with them ; they may be the fundamentals 

 of the universe. Their number is vast beyond all computation. 

 Seen through a section hundreds of thousands of millions of 

 miles thick, they could hardly be perfectly translucid. 



And besides all this there is cosmic dust. It is microscopic 

 in dimensions, possibly less than a thousandth of a millimetre 

 in average diameter. However, the stars are very far. Arrhenius 

 has computed that no more than one hundred such minute 

 particles, distributed evenly through every cubic kilometre of 

 space, would, at the distance of the farther stars, suffice to 

 block their light from our view. 



In view of all this, it becomes highly improbable that the 

 light of all the stars reaches our eyes undimmed. It is possible 

 that this accounts for the fact that the heavens are not eternally 

 ablaze, and why a billion of blazing suns in no wise affects the 

 temperature of* the earth. It may be that we see the stars 

 as through a veil, and that the more distant of them are nothing 

 like so far away as our present estimates suppose. This, of 

 course, in no wise touches the distance of those whose parallax 

 has actually been determined ; but these are hundreds against 

 many millions. It may well be that the stars of the eighteenth 

 magnitude are nothing like a thousand times as far away as 

 the average of the first magnitude stars, as the present theory 

 supposes. 



The question will probably find decisive answer from in- 

 vestigations that are now being carried out. Professor Comstock 

 of Washburn Observatory has recently brought forward the 

 evidence to show that either the more distant stars have in- 

 dividually less light-giving power, are actually smaller or fainter, 

 or else that at great distances their light does suffer some diminu- 

 tion, some absorption. There seems, of course, no reason to 

 suppose that the actual size or luminosity of the stars is any 

 less in one particular region than in another. The conclusion, 

 therefore, is for absorption, and Professor Comstock endeavours 

 to find what factor of absorption, mathematically expressed, 

 would account for the facts he has brought out. 



If such an absorption takes place, it is obvious that we 

 shall never know much about the farther reaches of the stellar 

 system, and nothing at all of its possible boundaries or shape. 

 We shall, to be sure, steadily advance in our knowledge of 



