CHAPTER l^Our Earth and Its 

 Fellow Planets 



E HAVE NOTHING ON EARTH SO Sublime as the 



star-filled night sky. We gaze in wonder- 

 ment at this vast and mysteriously ordered universe where a 

 million miles is a short distance and where each of the countless 

 stars moves in its own sphere without disturbing other heavenly 

 bodies. Who, looking heavenward, can fail to feel trivial by 

 comparison? 



A small child may not share all our adult feelings about this 

 miracle of the skies. Yet even to him the night sky has an irresis- 

 tible fascination. When a child recites "Twinkle, twinkle, little 

 star, how I wonder what you are," he is unwittingly giving expres- 

 sion to mankind's old curiosity about what a star is, and why it 

 behaves as it does. But the child can ask more questions about 

 stars than does the poem. Why do stars disappear in the daytime? 

 What makes stars twinkle? Why can't we fly to them in an air- 

 plane? Don't they ever bump into each other? These are questions 

 that many a child has asked me. 



Some of them are quite easy to answer. We cannot see stars in 

 the daytime because the brilliant light of the sun blots them out. 

 A youngster can understand this more easily when he looks at 

 the night sky from a brightly lit city and finds how dim the stars 

 seem and then sees their brightness from dark country fields. 



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