The Distances to the Heavenly Bodies 169 



FIG. in. How the distance to the moon is measured. If the astronomer knows 

 the length of the line AB and the size of the angles M and N, he can compute the 

 distance to the point C. 



had started from Italy in 753 B.C. in an airplane 

 that would carry them 125 miles an hour. In 2 days 

 they might have reached North America, and on the 

 third they would have crossed the continent and 

 reached the Pacific Ocean. Keeping on around the 

 world they would have arrived at their native land in 

 about a week from the time they started. Suppose 

 them to start again on a journey, this time to the moon, 

 traveling at the same high rate of speed. The journey 

 would have required about 80 days, and if they had 

 started back to the earth at once it would have been 

 more than 5 months before they reached their home 

 again. 



Suppose they had then set out for the sun. They 

 would have taken 85 years to reach it and would 

 have grown quite old before they arrived. If, not 

 content with seeing so much of the universe, they had 

 kept on through space, directing their swift flight toward 

 the great planet Jupiter, the journey from the sun to 



