Exploring the Cosmos and Introductory Astronomy and Astrophysics
                                    
                                        
                                        JUL 01, 1974
                                    
                                
                            
                            
                            
                              DOI: 10.1063/1.3128694
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More about the Authors
Carl Sagan. Cornell University.
                                © 1974. American Institute of Physics