Just finished reading a biography of Carl Sagan by Keay Davidson. In the early part of his life he was very egotistical and in many ways not a nice person, although recognized as very bright. He had fantasies shared by many youngsters. I enjoyed the book and the tv series, "Cosmos" as well as a few other books. Following Carl's thoughts made one feel sophisticated.
One of Carl's obsessions was to find life outside earth. Eventually his reasoning combined with new results doomed his early hopes. Venus was considered a candidate for life, but as it was examined more closely it was determined that it was far too hot to sustain any life. At first its closeness to the sun was thought to be the critical factor and then different aspects of the atmosphere were examined. Carl was one of the first to realize that Venus was enveloped with heat retaining substances, one of which was carbon. This led other scientists to study the matter more closely for our home planet.
Carl had been involved in a project to listen to radio signals from outer space, called SETI. The reasoning was that with so many stars in the universe there has to be some with conditions similar to earth, some of those with life and some of those with advanced civilizations. There has been a great deal of argument against wasting the money for a project and the disappointing results seem to reinforce the argument. In a formula that captures the idea one key factor is the life of civilizations. How many survive long enough to be technologically advanced enough to communicate across the galaxy. Sagan was concerned that perhaps intelligence can lead to self-destruction.
He had a long history of taking activist causes. He participated in civil rights marches and gave lectures at black southern universities. He also became concerned with feminist causes.
Although as a scientist he had been funded by the military and worked on their projects he became anti-nuclear. He dared to criticize Ronald Reagan's pet Star Wars project. He felt that any anti missile system that could not totally prevent nuclear missiles gave false security. Right wing politicians would argue that a nuclear war was survivable, but Sagan helped organize scientist education against that notion.
His second last book, "The Demon-Haunted World" proved to be a good conversation piece with a friend, Gary Lohman. Sagan was concerned that the masses of the people were more aware of gossip than they were of many more significant facts of the news. Too many people seemed more willing to believe that Elvis Presley was still alive than would accept that science had proved smoking causes cancer. He referred to Thomas Jefferson who pointed out that the cost of education is trivial compared to the cost of ignorance or of leaving the government to the wolves. Judging by the American electorate, science does not often enough over-ride some religious belief or self serving pronouncements of big money.
After his death, a movie of his book "Contact" was released. He and wife Ann Druyan worked on both the book and the movie. They became friends with producer Linda Olbst. An observation made was that two movies dealing with aliens, "Men in Black" and "Independence Day" depicted aliens as the enemy. Both movies were more popular than "Contact" which sought aliens as friends.
What motivates people to pursue a particular path is often a model or a shining light. Carl Sagan was a candle in the dark. We need more scientists and they deserve more respect.