Are we really alone in the universe? Can physics and math -- fundamental truths that underpin the universe -- act as symbolic messages to communicate with other life?
Carl Sagan wondered similar questions. Perhaps more than anyone, Sagan wanted to find other intelligence in the universe, but he was grounded by the lack of proof [source: Poundstone]. He famously coined the phrase, "Extraordinary claims require extraordinary proof," and at times dismissed his own sci-fi fantasies of aliens lurking around the cosmic corner. In a sense, Sagan's obsession with finding other life made him more relatable to the public. At the time, it was rare to see scientists comment on such things.
His 1985 novel "Contact," which was later made into a motion picture, portrayed one scientist's transmitting signals into space with the hope of intercepting other life. The novel certainly drew inspiration from Sagan's search for ET at the SETI Institute and from colleague Jill Tarter in particular. Sagan also strove to understand the chemical recipe necessary for basic life outside of Earth to take root, a discipline known as exobiology. He promoted using biology, chemistry and physics to probe life's origins.
But his most memorable space projects were less about hard science and more about humanity and love.
Should ET ever intercept a NASA spacecraft, Sagan wanted to be ready. This explains the golden record on Voyager 1 and 2, each containing "sounds" from the natural world and cultures, and 115 "images" representative of the diversity of life on Earth [source: NASA Jet Propulsion Laboratory].
"His feeling was that the American taxpayers and the world are really helping to support this, so we should have something that they can relate to," said Sagan biographer William Poundstone. The golden record united people despite their myriad differences.
Sagan's wife, Ann Druyan, recalls creating her own sounds for the project by recording and translating her body's brainwaves and vital signs into music. During the recording, she meditated and told the story of the universe (as humans knew it) with her thoughts. Her mind wandered to her love for Sagan, too. With the spacecraft now venturing deeper into the unknown of interstellar space each moment, Druyan still views her recordings as a romantic, cosmic tribute to the relationship she and Sagan shared [source: Druyan].