A respected planetary scientist best known outside the field for his popularizations of astronomy, Carl Sagan was born in New York City on November 9, 1934. He attended the University of Chicago, where he received a B.A. in 1954, a B.S. in 1955, and a M.S. in 1956 in physics as well as a Ph.D. in 1960 in astronomy and astrophysics. He has several early scholarly achievements including the experimental demonstration of the synthesis of the energy-carrying molecule ATP (adenosine triphosphate) in primitive-earth experiments. Another was the proposal that the greenhouse effect explained the high temperature of the surface of Venus. He was also one of the driving forces behind the mission of the U.S. satellite Viking to the surface of Mars. He was part of a team that investigated the effects of nuclear war on the earth's climate - the "nuclear winter" scenario. Sagan's role in developing the "Cosmos" series, one of the most successful series of any kind to be broadcast on the Public Broadcasting System, and his book The Dragons of Eden (1977) won the Pulitzer Prize in 1978. He also wrote the novel Contact, which was made into a movie starring Jodie Foster. He died from pneumonia on December 20, 1996.
Astrophysicist Neil deGrasse Tyson was born in New York City on October 5, 1958. Interested in astronomy since he was a child, Tyson gave lectures on the topic at the age of 15. He attended the Bronx High School of Science and was the editor-in-chief for its Physical Science Journal. After earning a B.A. in Physics from Harvard in 1980, Tyson received an M.A. in Astronomy from the University of Texas at Austin in 1983. He earned his Ph.D. in Astrophysics from Columbia in 1991. Since 1996, Tyson has held the position of Frederick P. Rose Director of the Hayden Planetarium at Manhattan's American Museum of Natural History. In 2001, he was appointed by President George W. Bush to serve on the Commission on the Future of the United States Aerospace Industry. In 2004, Tyson joined the President's Commission on Implementation of United States Space Exploration Policy. He has hosted PBS's television show NOVA scienceNOW since 2006. Tyson can also be seen frequently as a guest on The Daily Show with Jon Stewart, The Colbert Report, and Late Night with Conan O'Brien. Tyson has written many popular books on astronomy, and he began his "Universe" column for Natural History magazine in 1995. In 2009, he published the bestselling book The Pluto Files: The Rise and Fall of America's Favorite Planet to describe the controversy over Pluto's demotion to dwarf planet. Tyson was recognized in 2004 with the NASA Distinguished Public Service Medal, and Time named him one of the 100 Most Influential People of 2007.