12 The Outline of Science 



We thru have a total or partial eclipse of the sun. At other 

 times the earth passes directly between the sun and the moon, 

 and causes an erlipse of the moon. The great ball of the earth 

 naturally trails a mighty shadow across space, and the moon is 

 "eclipsed" when it passes into this. 



The other seven planets, five of which have moons of their 

 own. circle round the sun as the earth does. The sun's mass is 

 immensely larger than that of all the planets put together, and 

 all of them would be drawn into it and perish if they did not 

 travel rapidly round it in gigantic orbits. So the eight planets, 

 spinning round on their axes, follow their fixed paths round the 

 MIII. The planets are secondary bodies, but they are most im- 

 portant, because they are the only globes in which there can be 

 life, as we know life. 



If we could be transported in some magical way to an 

 immense distance in space above the sun, we should see our Solar 

 tern as it is drawn in the accompanying diagram (Fig. 1), 

 except that the planets would be mere specks, faintly visible in 

 the light which they receive from the sun. (This diagram is 

 drawn approximately to scale.) If we moved still farther away, 

 trillions of miles away, the planets would fade entirely out 

 of view, and the sun would shrink into a point of fire, a 

 And here you begin to realize the nature of the universe. 

 The tun it a Star. The stars are suns. Our sun looks big simply 

 because of its comparative nearness to us. The universe is a 

 stupendous collection of millions of stars or suns, many of which 



ha\e planetary families like ours. 



2 



The Scale of the Universe 



Ho\\ many stars are there? A glance at a photograph of 

 star-el. .uds will tell at once that it is quite impossible to count 

 them. Tin- tim- photograph reproduced in Figure 2 represents 



