Preface; Carl Sagan at sixty; Part I. Planetary Exploration: 1. On the occasion of Carl Sagan's sixtieth birthday Wesley T. Huntress, Jr.; 2. The search for the origins of life: U.S. Solar system exploration, 1962-1994 Edward C. Stone; 3. Highlights of the Russian planetary program Roald Sageev; 4. From the eyepiece to the footpad: The search for life on Mars Bruce Murray; Part II. Life in the Cosmos: 5. Environments of Earth and other worlds Owen B. Toon; 6. The origin of life in a cosmic context Christopher F. Chyba; 7. Impacts and life: Living in a risky planetary system David Morrison; 8. Extraterrestrial intelligence: The significance of the search Frank D. Drake; 9. Extraterrestrial intelligence: The search programs Paul Horowitz; 10. Do the laws of physics permit wormholes for interstellar travel and machines for time travel? Kip S. Thorne; Public Address: 11. The age of exploration Carl Sagan; Part III. Science Education: 12. Does science need to be popularized? Ann Druyen; 13. Science and pseudo-science James Randi; 14. Science education in a democracy Philip Morrison; 15. The visual presentation of science Jon Lomberg; 16. Science and the press Walter Anderson; 17. Science and teaching Bill G. Aldridge; Part IV. Science, Environment and Public Policy: 18. The relationship of science and power Richard L. Garwin; 19. Nuclear-free world? Georgi Arbatov; 20. Carl Sagan and nuclear winter Richard P. Turco; 21. Public understanding of global climate change James Hansen; 22. Science and religion Joan B. Campbell; 23. Speech in honor of Carl Sagan Frank Press.