The Outer Planets 



247 



on January i, 1919, and about one month later with 

 each succeeding year. 



FIG. 148. Jupiter in conjunction and in opposition. 



Jupiter's year is about 12 times as long as our year. 

 This great planet rotates on its axis in 9 hours, 55 

 minutes, so that the time between sunrise and sunset 

 there is less than 5 hours and we should have to hurry 

 to accomplish a day's work before sundown. Moreover, 

 hurry on Jupiter would be difficult, for a man who weighs 

 150 pounds on the earth would weigh 400 pounds on 

 Jupiter. There you could not jump half as high as you 

 can here. 



Possibly if you were on Jupiter you would find nothing 

 to stand on or lie on, for all that can be seen from the 

 earth is cloud. It may be that the whole planet, like 

 the sun, consists of gases, vapors, and mist, which are 

 hot, although the intensity of the heat received from 

 the sun at that distance is only ? of what it is at the 

 earth's distance. It is probably not so hot as to emit 

 any light of its own. We see it as we do other planets, 

 by means of reflected sunlight. Its brilliancy is due 

 both to its large size and to its high reflecting power, 

 for, like a bright cloud, it reflects more light than does 



