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The Pale Blue Dot is a photograph of planet Earth taken by Voyager 1 from a record distance, showing it against the vastness of space. Both the idea for taking the distant photo, and the title came from scientist and astronomer Carl Sagan, who also wrote the 1994 book of the same name. In 2001, it was selected by Space.com as one of the top ten space science photos.1
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The photograph
On February 14, 1990, NASA commanded the Voyager 1 spacecraft, having completed its primary mission, to turn around to photograph the planets of the Solar System.2 One image Voyager returned was of Earth, showing up as a "pale blue dot" in the grainy photo.3
Sagan gives the distance as 3.7 billion miles in the book, while NASA website describes it as "more than 4 billion miles" (6.4 billion kilometres). According to JPL's HORIZONS software, on February 14, 1990, the distance to Voyager 1 from Earth was 40.47 A.U. (6.054 billion kilometres or 3.763 billion miles), and the distance to the sun was 40.36 A.U. (6.038 billion kilometres or 3.752 billion miles).
The picture was taken using a narrow-angle camera at 32° above the ecliptic, and created using blue, green, and violet filters.4 Narrow-angle cameras, as opposed to wide-angle cameras, are equipped to photograph specific details in an area of interest.5 Earth takes up less than a single pixel — NASA says "only 0.12 pixel in size."4
Sagan wrote:
| “ | "While almost everyone is taught that the Earth is a sphere with all of us somehow glued to it by gravity, the reality of our circumstance did not really begin to sink in until the famous frame-filling Apollo photograph of the whole Earth — the one taken by the Apollo 17 astronauts on the last journey of humans to the Moon." | ” |
6 In the spirit of that realization, Sagan pushed for Voyager to take a photo of the Earth from its vantage point on the edge of the solar system.3
Voyager took similar pictures of Venus, Jupiter, Saturn, Uranus and Neptune, creating a portrait of the Solar System.4 Mercury's proximity to the Sun prevented it from being photographed and Mars was not visible due to the effect of sunlight on the camera's optics.7 NASA compiled 60 images produced into a mosaic, called Family Portrait.
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In a commencement address delivered May 11, 1996, Sagan related his thoughts on the deeper meaning of the photograph:8
| “ | 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.
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand. It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known. |
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Al Gore's 2006 documentary film An Inconvenient Truth featured the "Pale Blue Dot" photo at the end. Gore used it in his slide show to underline the need to stop global warming,9 paraphrasing Carl Sagan with the statement, "That's all we've got".
See also
Footnotes
References
- Sagan, Carl (1994). Pale Blue Dot: A Vision of the Human Future in Space (1st edition ed.). New York: Random House. ISBN 0-679-43841-6.
Citations
- ^ Britt, Robert Roy (25 September 2001). "Experts Pick: Top 10 Space Science Photos". Space.com. http://www.space.com/scienceastronomy/astronomy/top10_images_010925-11.html.
- ^ "Pale Blue Dot". The Planetary Society. https://planetary.org/bluedot_poster.html. Retrieved on 2006-07-27.
- ^ a b Sagan. "Chapter 1. You Are Here". Pale Blue Dot. http://www.planetary.org/explore/topics/space_missions/voyager/pale_blue_dot.html. The quote is much copied elsewhere on the web.
- ^ a b c "Solar System Portrait – Earth as 'Pale Blue Dot'". NASA. http://visibleearth.nasa.gov/view_rec.php?vev1id=1947.
- ^ "SPACECRAFT - Cassini Orbiter Instruments - ISS". NASA. http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-iss.cfm.
- ^ The Pale Blue Dot, Chapter 1, end of the fifth paragraph
- ^ "Solar System Portrait – Views of 6 Planets". NASA. http://visibleearth.nasa.gov/view_rec.php?id=600.
- ^ "Reflections on a Mote of Dust". https://planetary.org/bluedot_poster.html. Retrieved on 2007-04-07.
- ^ Gore, Al (January 15, 2004). "Al Gore Speaks on Global Warming and the Environment". MoveOn.org. http://civic.moveon.org/gore3/speech.html. Retrieved on 2006-12-18.
External links
- Sagan's rationale for human spaceflight Article about Carl Sagan and Pale Blue Dot
- Spaceflight or Extinction: Carl Sagan Excerpts from Pale Blue Dot
- A new picture of Earth taken through the rings of Saturn by the Cassini spacecraft on September 15, 2006. Cassini's most popular photo.
- Carolyn Porco's opening speech on Pangea Day, May 10, 2008 Carolyn Porco discusses Cassini's image of Earth and introduces a film based on Sagan's 'Pale Blue Dot' on Pangea Day
- BookTalk.org: discuss Carl Sagan's Pale Blue Dot with other readers
- Video homage to the Pale Blue Dot
- [1] JPL's HORIZONS on-line solar system data and ephemeris computation service
Wikipedia content modification information:
- This page was last modified on 28 December 2008, at 06:43.
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