MIRACLES OF SCIENCE 



The results of these measurements and computa- 

 tions show that the great outlying planets are of 

 very low density, no one of them being as dense as 

 the sun. The density of water being taken as unity, 

 the density of Jupiter is found to be 1.33, that of 

 Saturn 0.72, that of Uranus 1.22, and that of Neptune 

 1.11. When it is recalled that the density of the 

 earth is about 5.50, it will be seen that the outlying 

 planets are very tenuous structures. Like the sun, 

 they are doubtless gaseous in constitution, although 

 their great bulk gives them a gravitational power 

 that condenses their average substance to a fluid 

 consistency, Jupiter, as the figures just cited show, 

 being about one-third denser than water, and Saturn, 

 the most tenuous of all, less than three-quarters as 

 dense. 



Notwithstanding their tenuous structure, how- 

 ever, the outlying planets are of such enormous bulk 

 that their total mass quite dwarfs that of the earth. 

 Jupiter would require more than 317 globes like ours 

 to balance its weight, and Saturn would more than 

 tip the beam against 94 earths. Uranus and Nep- 

 tune, however, are less colossal, the weight of the 

 former being only 14.6, and that of the latter only 

 17 times that of our globe. 



Our nearer neighbor Mars, on the other hand, has 

 a structure more like that of our own planet, its 

 average density being 3.95, or about seven-tenths 

 that of the earth. Its total mass is a little less than 

 one-ninth (0.11) that of the earth. 



The two remaining major planets, Mercury and 

 Venus, are without satellites, and hence can not be 



