170 Trees, Stars, and Birds 



Jupiter would have required 441 years; for Jupiter 

 is more than 5 times as far from the sun as we are. 



EARTH'S OKB1T IS AN ELLIPSE THAT IS NEAM.Y 

 A CIRCLE. IT IS HERE SHOWN IN PERSPECTIVE 

 AHI> THEREFORE, APPEARS FLATTENED -> 





-TH IN SUMMER- -^>SUN EARTH IN 



FIG. 112. How the distance to a star is measured. 



If they had arrived at Jupiter in 227 B.C., and that 

 same year had directed their course toward the orbit 

 of Neptune, the most distant of all the worlds that re- 

 volve around the sun, they would not have reached the 

 path of that planet until the year 1879. 



Suppose Neptune in 1879 to have been on the opposite 

 side of his orbit from the point where Romulus and 

 Remus arrived, and that they had set out to meet him, 

 traveling still at the rate of 125 miles an hour, or 3000 

 miles a day. Neptune is the slowest of all the planets ; 

 nevertheless, he moves along his path at a speed of 

 about 200 miles a minute, which is farther than Romulus 

 and Remus are flying in an hour. Although Neptune 

 and our voyagers through space were moving toward 



