rays cf Ju|)itri-. 'I'li;it \;i-l liiidy, \\kr ihc r;irlli, is \\lii]-lin,L; nii 

 its axis. Init muoli niDii' r;i]ii(lly. coinplclins^^ tlir i-ntation ol" its 

 huge l)ulk in ton In mis. Thiis, rays directed Inwards the earth, 

 which left its surface I" iiiimtle'- a.t^n, ]]:\\c w andci-c(l dlT into 

 far distant space, niilhun-^ nl" nnK'> in the rear (jI' the earth's 

 present position in its orl)il. I'.nt in this case we have not only 

 to take into account llie rotation of Jupiter round its axis, Init 

 als() its motion of S miles per second along its oi-hit i-ound the 

 sun. 



Wiw tliis complexity of motion is still furllier enlianced when 

 we take into consideration star motions, 'i'ake our own sun, 

 for instance. That mighty orh is transporting its large family 

 of planets, satellites, and comets at the rate of 12 miles per 

 second towards the great sun \ ega, shining from the zenith in 

 our summer evening skies, and estimated to be some 30 light 

 years distant — about four times as far away as the bright star 

 Sirius. But our own sun will never reach Vega, for when, in 

 the course of many million years it arrives at the point where 

 \'ega now is, that star, which is moving rapidly across our line 

 of sight, \vill he in a distant part of our sidereal system. 



Every star in the universe is in swift motion, either approach- 

 ing or receding from us, directly or diagonally, or moving across 

 the line of sight in every conceivable direction. But all are mov- 

 ing in vast but inappreciajjle curves, with radii so large that we 

 cannot distinguish the curves from straight lines. But every 

 star is at such an enormous distance from our solar system that 

 the rays of light coming from each have occupied from four 

 years to 20,000 years in traversing the intervening spaces. 



Xow each of these stars is probably rotating round its own 

 axis and ])rojecting rays of light from every inch of its spherical 

 surface. Take Polaris for instance — the North Star — a gigantic 

 sun whose dimensions are estimated to be eighty times those 

 of our own sun. While it is whirling on its own axis it is at 

 the same time swiftly circling opposite its big companion round 

 a common center of gravity in a period of four days. Again, 

 these two great suns are moving as a unit in a much larger orbit 

 round a gigantic dark body in a period of about 12 years; and 

 that body is by no means stationary, but moving in as yet an 

 unknown direction through the limitless voids of distant space, 



Xow if Polaris should this night direct a ray of light towards 

 the earth, both Polaris and the earth being in their present un- 

 stable positions in the universe, at the end of 46 years that ray 

 of light would perhaps reach some other world millions of millions 

 of miles distant from our present location. On the other hand, if 

 the North Star 46 years ago, while gyrating on its axis, circling 

 with its companion in its small four day orbit, and also moving 

 with planetary velocity round its masterful dark star, and yet 

 swinging with the wonderful system of which it forms a part far 



22 



