8 EXPERIMENTAL GENERAL SCIENCE 



era Crown, Sagittarius, Pegasus, and the Scorpion. In 

 winter Orion is easily the most conspicuous. Owing to the 

 rotation of the earth on its axis, most of the constellations 

 appear to rise and set nightly. A few in the north, including 

 the Great Bear, are so situated with respect to the earth that 

 they never set but appear to circle endlessly about the pole 

 star. This is because the earth's axis points toward the part of 

 the heavens in which the pole star the so-called north star is 

 located. For the same reason, there are other constellations 

 that never rise for us, being below our southern horizon and 

 hidden from us by the great bulk of the earth. Since our 

 north pole points in the direction of the north or pole star, an 

 observer at the pole would find the star overhead, and at the 

 equator it would be on the horizon. The number of degrees 

 the pole star is above the horizon in any given locality is the 

 number of degrees the place is north of the equator, that is, it is 

 the latitude of the place. 



11. The Solar System. Our sun with its attendant bodies, 

 called planets, comprises the solar system. There are eight 

 planets which, named in their order from the sun outward 

 through space, are Mercury, Venus, Earth, Mars, Jupiter. 

 Saturn, Uranus, and Neptune. As seen with the unaided eye, 

 most of the planets appear as rather bright stars. Owing to 

 the fact that they ' are so near us, their motion is very 

 noticeable, and consequently they do not have definite places 

 in the sky, but change their courses with the seasons. The 

 ancients called such stars " planets" (which means "wander- 

 ers") to distinguish them from the "fixed" stars which seemed 

 to them to be fixed in their places. Often the planets are 

 especially noticeable, as when they appear in the evening sky 

 shortly after sunset. 



12. The Sun. Although so insignificant compared with the 

 other stars, our sun is still a body of vast dimensions. It is, in 

 fact, about a million times larger than the earth and seven 



