OUR PLACE IN SPACE 357 



Our little earth turns, of course, very near the sun ; it is one 

 of the innermost of the planets. Jupiter is five times as far. 

 Within the planetary scheme the remotest object which we may 

 see with the naked eye is Saturn with his rings ; he is distant 

 about ten times the way of the sun. The telescope brings within 

 our view Neptune three times farther still. This, the outermost 

 reach of the system, so far as we know it, lies at consider- 

 ably more than a hundred thousand times a girdle of the 

 earth, considerably more than a million times the width of the 

 Atlantic, a little under twenty-eight hundred million miles. To 

 skirt the rim of this system, Neptune, travelling at 200 miles 

 per minute, requires 165 of our earthly years. 



Could we set out from this rim for a journey through space, 

 so far as we know the first stopping-place which we might 

 gain would be the alpha star of the constellation of the Centaur. 

 It is something like nine thousand times the distance of Neptune 

 that is to say, about two hundred and seventy-seven thou- 

 sand times the distance of the sun. To cross the intervening 

 emptiness, could we travel at the speed of light, would require 

 close to four and a half years ; at the speed of an express train, 

 one million two hundred and fifty thousand years. 



The brilliant Dog-star lies apparently twice farther still 

 that is to say, at eight or nine light-years from our solar system. 

 The Pole-star is something like forty light-years. These are 

 among the nearest of the suns. 



With present-day micrometric methods, and still more by 

 means of the photographic plate, it is possible to reduce the 

 limits of error in measures of parallax to between o.oi and 0.02 

 of a second of arc. As the accepted parallax of alpha Centauri 

 is about |, or 0.75 of a second, it will be seen that there is little 

 likelihood that further advances will seriously change our ideas 

 as to the distance of the nearer stars. 



In all, measures of parallax have been effected with reason- 

 able accuracy upon sixty to a hundred suns, and the number 

 is growing steadily. But this, in the face of fifty millions 

 or more which the gigantic telescopes of the present day will 

 disclose, seems an absurdly small number ; it might readily 

 yield the inference that their distance is for the most part 

 so great that it would be hopeless ever to dream of trying 

 to fix our place in cosmos. The easy conclusion would be 

 that, so far as any human means of observation will ever 



