GIANT SUNS — TURNER. 175 



to a patient Scotsman. Those that are measurable show that the}'' 

 are so far off that light takes years to come to us from them — from 

 some four years ; from others hundreds of years ; from those with no 

 measurable result, thousands of years at least. 



Thus we began to obtain a little knowledge of the distance of the 

 stars. The method used for these measurements was the usual 

 method of parallax, which we may illustrate by two searchlights 

 trained on the same Zeppelin. Knowing their distance apart and the 

 angles at which they are sending their beams of light, those working 

 the apparatus can draw the triangle to scale and thus tell the height 

 of the Zeppelin. 



Now, replace the two searchlights by two telescopes — one on one 

 side of the earth's orbit round the sun, and the other on the other 

 side ; they can not be there simultaneously, but the star will wait six 

 months for us to move round or even longer. The angle at the 

 Zeppelin becomes, however, woefully small as we suppose it to mount 

 to the stars. It is twice the angle which seems to separate earth and 

 sun as seen from the Zeppelin, and it is this angle which is repre- 

 sented by the diameter of " a 3-penny bit 2 miles away." From the 

 distance of the nearest star the sun and earth might appear as a close 

 double star, of which there are many examples in the heavens, though 

 our little earth would probably be too faint to be seen, even from the 

 nearest star spectator. 



There would be no such difficulty in seeing the sun, but since his 

 diameter is only one one-hundredth part of the distance between 

 earth and sun, which has itself shrunk to almost imperceptible di- 

 mensions, it is easy to realize that the disk of the sun would have 

 disappeared completely, as does any disk of the stars to us, even with 

 our largest telescopes. 



Since we have imagined ourselves to mount far upward to a 

 Centauri, whence the sun and earth would represent a close double 

 star, let us retain the conception a moment longer in order to note a 

 useful fact. Watching long enough we should see the pair moving 

 across the heavens, while at the same time the earth would revolve 

 round its mighty companion. The sun would proceed therefore very 

 much more steadily than the earth. The sun's path is nearly 

 straight, while the earth takes a wavy path, or more correctly a cork- 

 screw path. If the masses of the two bodies were more nearly equal, 

 the two paths would be more nearly alike, and both wavy. 



By observing such movements (for we can observe the movements 

 of stars) we infer whether one component of a double star is more 

 massive than the other or whether they are nearly equal; and it is 

 found that there is never any very great disparity in mass between 

 the components. Their masses are closely similar, like those of peb- 



