MIRACLES OF SCIENCE 



of the absence of air and the frigidity of empty space. 

 Yet it would constitute only the beginning of an ex- 

 ploratory tour across the solar system. If our phan- 

 tom voyager were disposed to see something more 

 of the world-system of which the earth and Mars are 

 minor members, he might pass right on for some cen- 

 turies through the region of the swarming minor 

 planets, called asteroids or planetoids, and only after 

 700 years of flying would he come to Jupiter, some- 

 thing really worth while in the way of planets, bulk- 

 ing 1300 times bigger than the earth. 



Another period of 760 years would be required! 

 to cross the gap between Jupiter and Saturn. The 

 journey from Saturn to Uranus would require 1700 

 years. And the final stage of the tour across the 

 planetary system to Neptune, the farthest outlying 

 member of the sun's family, would take 1800 years 

 more. Thus the entire journey from the earth to 

 Neptune (when that planet is nearest us) would re- 

 quire 5000 years. 



If we recall that the craft which thus required 

 fifty centuries to pass from our earth to its most dis- 

 tant planetary neighbor required but seventeen days 

 to circumnavigate the earth itself, we shall pretty 

 clearly realize that our solar system is a stupendous 

 structure. 



But all things are relative. And if we would fully 

 grasp the situation, we must reflect that the journey 

 to Neptune is after all only a very short excursion 

 into the depths of space as contrasted with the stellar 

 distances. If our hypothetical air-machine, which 

 went to Mars in ninety years, and to Neptune in 5000, 



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