Carl Sagan

Astronomer and Pulitzer Prize winner Carl Sagan died today at the age of 62. A spokesman for the Cancer Research Center says Sagan died from pneumonia after suffering from bone marrow disease for two years.

The famed astronomer and writer is co-author of the new book, "A Path Where No Man Thought." It's about the theory that even a small nuclear war would lead to a nuclear winter that would devastate the earth.

The astrophysicist says that participating in a "great unfolding of a cosmic story" should make us feel large, not small. This spring, Tyson hosts a TV series called Cosmos: A Space-Time Odyssey.