LIGHT. 125 



gives us a new field of visible stars. If this expansion of the 

 stellar universe go on indefinitely and no light be lost, then, 

 assuming the fixed stars to be of an average equal brightness 

 with our sun, and to fill up every point of space, and that no 

 light be lost other than that by divergence, the night ought to 

 be equally luminous with the day ; for though the light from 

 each point diminishes in intensity as the square of the dis- 

 tance, the number of luminous points would increase as the 

 square of the distance, and thus occupy the whole visible 

 space around us ; and if every point of space is occupied by 

 an equally brilliant point of light, the distance of the points 

 from us becomes immaterial. The loss of light intercepted 

 by stellar bodies would make no difference in the total quan- 

 tity of light reaching us, for each of these would yield from its 

 own self-luminosity at least as much light as it intercepted. 

 Light may, however, be intercepted by non-luminous bodies, 

 such as planets revolving round the self-luminous stars ; but, 

 making every allowance for these, it is difficult to understand 

 why we get so little light at night from the stellar universe, 

 without assuming that some light is lost in its progress 

 through space not lost absolutely, for that would be an 

 annihilation of force but converted into some other mode of 

 motion. 



It may be objected that this hypothesis assumes the stellar 

 universe to be illimitable : if pushed to its extreme so as to 

 make the light of night equal that of day, provided no stellar 

 light be lost, it does make this assumption ; but even this seems 

 a far more rational assumption to make than that the stellar 

 universe is limited. Our experience gives no indication of a 

 limit ; each improvement in telescopic power gives us new 

 realms of stars or of nebulse, which, if not stellar clusters, are 

 at all events self-luminous matter ; and if we assume a limit, 

 what is it ? We cannot conceive a physical boundary, for 

 then immediately comes the question, what bounds the 

 boundary ? and to suppose the stellar universe to be bounded 

 by infinite space or by infinite chaos, that is to say, to suppose 

 a spot for it would then become so of matter in definite 

 forms, with definite forces, and probably teeming with definite 

 organic beings, plunged in a universe of nothing, is, to my 



