It was Carl Sagan’s birthday last week (November 9, to be precise). He would have been 77 years old — he returned to “star-stuff” in 1996. Thoughts of this charming astronomer and cosmologist reminded us of a project with which he was intimately involved — the Voyager program.
In 1977, NASA launched two spacecraft to explore Jupiter and Saturn. The spacecraft performed so well that their missions were extended several times: first, to journey farther in the outer reaches of our solar system and explore the planets Neptune and Uranus; and second, to fly beyond our solar system into interstellar space. And, by all accounts both craft are now close to this boundary. The farthest, Voyager I, is currently over 11 billion miles away. For a real-time check on its distance, visit JPL’s Voyager site here. JPL is NASA’s Jet Propulsion Lab in Pasadena, CA.
Some may recall that Carl Sagan presided over the selection and installation of content from the Earth onto a gold plated disk that each Voyager carries on its continuing mission. The disk contains symbolic explanations of our planet and solar system, as well as images of its inhabitants and greetings spoken in 55 languages. After much wrangling over concerns about damaging Voyager’s imaging instruments by peering back at the Sun, Sagan was instrumental in having NASA reorient Voyager I’s camera back towards the Earth. This enabled the craft to snap one last set of images of our planet from its vantage point in deep space. One poignant image became know as the “Pale Blue Dot”, and Sagan penned some characteristically eloquent and philosophical words about this image in his book, Pale Blue Dot: A Vision of the Human Future in Space.
[div class=attrib]From Carl Sagan:[end-div]
From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Look again at that dot. That’s here, that’s home, that’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
[div class=attrib]About the image from NASA:[end-div]
From Voyager’s great distance Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera. Earth was a crescent only 0.12 pixel in size. Coincidentally, Earth lies right in the center of one of the scattered light rays resulting from taking the image so close to the sun. This blown-up image of the Earth was taken through three color filters – violet, blue and green – and recombined to produce the color image. The background features in the image are artifacts resulting from the magnification.
To ease identification we have drawn a gray circle around the image of the Earth.
[div class=attrib]Image courtesy of NASA / JPL.[end-div]