Pale Blue Dot

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Earth is a tiny dot 4 billion miles distant, about halfway down in the rightmost streak of sunlight circled in blue
Earth is a tiny dot 4 billion miles distant, about halfway down in the rightmost streak of sunlight circled in blue

"Pale Blue Dot" is a famous Voyager 1 photograph of Earth, and the title of a book by Carl Sagan inspired by the photo.

Contents

[edit] The photograph

On February 14, 1990, NASA commanded the Voyager 1 spacecraft, having completed its primary mission, to turn around to photograph the planets it had visited.[1][2] NASA ultimately compiled 60 images from this unique event into a mosaic of the Solar System.[3][4] One image Voyager returned was of Earth, 4 billion miles (6.4 billion kilometres) distant, showing up as a "pale blue dot" in the grainy photo.[5] Robert Britt describes the distance as "more than 4 billion miles."[6] 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.[7] Only 0.12 pixels represents Earth in the photo.[4][8][9]

Sagan said the famous Earthrise picture taken during the Apollo 8 mission, showing the entire Earth above the moon, forced humans to step back and see the Earth as just a part of the universe.[citation needed] In the spirit of that realization, Sagan said he pushed for Voyager to take a photo of the Earth from its vantage point on the edge of the solar system.[9][10]

There was danger to the spacecraft's optics from the nearby Sun.[citation needed] Voyager took similar pictures of Venus, Jupiter, Saturn, Uranus and Neptune, creating a "portrait" of the Solar System.[8] Mercury's proximity to the Sun prevented it from being photographed, Mars was not visible due to the effect of sunlight on the camera's optics, and Pluto was too small and distant.[11]

Sagan said the following quotation on May 11, 1996 about what he felt the photo demonstrated:[3]

We succeeded in taking that picture [from deep space], and if you look at it, you see a 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.

Later in the book, Sagan's wife, Ann Druyan, challenges readers to pick one of the other planetary dots photographed and featured in the book and imagine there are inhabitants on that world that believe the universe was created solely for themselves. She shared Sagan's belief that humans are not as important as they believe.

[edit] Media attention

The 2006 documentary film An Inconvenient Truth by Al Gore featured the "Pale Blue Dot" photo at the end of the movie. Gore used it in his slide show to demonstrate the need to stop global warming.[12] He said "That's all we've got" in reference to the Earth as a dot seen from four billion miles away. Gore also paraphrased Carl Sagan when he spoke about the photograph during the documentary.

[edit] Book summary

Pale Blue Dot: A Vision of the Human Future in Space (1994) is a non-fiction book by Carl Sagan. It is the sequel to Cosmos and was inspired by the "Pale Blue Dot" photograph, for which Sagan provides a sobering description.[13] In this book, Sagan mixes philosophy about the human place in the universe with a description of what was known about the solar system at the time the book was published. He also details a human vision for the future.[14]

The first part of the book looks at the claims made throughout history that Earth and the human species are unique. Sagan makes two claims for the persistance of the idea of a geocentric, or Earth-centred universe: human pride in our existence, and the threat of torturing those who dissented from it, particularly during the Spanish Inquisition. However, he also admits the scientific tools to prove the Earth orbited the Sun were (until the last few hundred years) not accurate enough to measure effects such as parallax, making it difficult for astronomers to prove the geocentric theory was false.

After saying that we have gained humility from understanding we are not, literally, the centre of the universe, Sagan embarks on an exploration of the entire solar system. He begins with an account of the Voyager program, in which Sagan was a participating scientist. He describes the difficulty of working with low light levels at distant planets, and the mechanical and computer problems which beset the twin spacecraft as they aged. Sagan then examines each one of the major planets as well as some of the moons, including Titan, Triton and Miranda, focusing on whether life is possible at the frontiers of the solar system.

Sagan argues that studying other planets provides context for understanding the Earth - and protecting it from environmental catastrophe. He feels NASA's decision to cut back human explorations to the moon after the Apollo program was a short-sighted decision, despite the expense and the failing popularity of the program among the American public. Sagan says future exploration of space should focus on ways to protect Earth. The book was published the year after the comet Shoemaker-Levy 9 crashed into Jupiter, an event Sagan uses to highlight the danger Earth faces from the occasional asteroid or comet large enough to cause substantial damage if it were to hit Earth. He says we need the political will to track large extra-terrestrial objects, or we risk losing everything. Sagan argues that in order to save the human race, space colonization and terraforming should be utilized.

The first edition of the book includes an extensive list of illustrations and photographs, mostly provided by NASA.


[edit] See also

[edit] References

  1. ^ A Pale Blue Dot. Big Sky Astronomy Club. Retrieved on 2006-04-02.
  2. ^ Pale Blue Dot. The Planetary Society. Retrieved on 2006-07-27.
  3. ^ a b Pale Blue Dot. Sky Image Lab Astrophoto. Retrieved on 2006-04-02.
  4. ^ a b c "http://www.spaceimages.com/palebluedot.html". 
  5. ^ Sagan. "You Are Here", Pale Blue Dot, 8-9. 
  6. ^ Britt, Robert Roy (2006-04-02). "http://www.space.com/scienceastronomy/astronomy/top10_images_010925-11.html". 
  7. ^ "http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-iss.cfm". 
  8. ^ a b "http://visibleearth.nasa.gov/view_rec.php?vev1id=1947". 
  9. ^ a b "http://www.planetary.org/explore/topics/space_missions/voyager/pale_blue_dot.html". 
  10. ^ "http://www.xeaglex.com/Page510.Quotations.shtml". 
  11. ^ Portrait of the Solar System
  12. ^ Gore, Al (January 15, 2004). " Al Gore Speaks on Global Warming and the Environment". MoveOn.org. Retrieved on 2006-12-18.
  13. ^ "http://www.bigskyastroclub.org/pale_blue_dot.htm". 
  14. ^ "http://www.biblio.com/isbnsearch.php?isbn=0345376595". 

[edit] External links

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