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. It is also the title of a 1994 book by scientist and astronomer Carl Sagan. Both the idea for taking the distant photo, and the title came from Carl Sagan. In 2001, it was selected by Space.com as one of the top ten space science photos.
An extended homage video ("Pale Blue Dot / Wanderers") created by Lang Kasranov uses the unredacted audiobook to provide the authoritative historic backstory to how the Pale Blue Dot photo came to be taken. A briefer homage by Pale Blue Films is less science oriented, but still offers opens with some historic context and had over a quarter-million YouTube viewings in it's first year and a half since release. A collaborative video homage primarily by Joshua Sellers was released by The Sagan Appreciation Society to mark the announcement of the NASA Carl Sagan Fellowships in Astrobiology. It remains one of the most highly-rated Pale Blue Dot homage on YouTube. The first-ever Pangea Day event opened with a simple homage to the Pale Blue Dot, adding to the growth of the meme. It was presented by scientist Carolyn Porco, who helped work out the exposure times on the original Voyager photo. In half a year the 20-minute segment on YouTube had over 1 Million viewings.
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).
The picture was taken using a narrow-angle camera at 32° above the ecliptic, and created using blue, green, and violet filters. Narrow-angle cameras, as opposed to wide-angle cameras, are equipped to photograph specific details in an area of interest. Earth takes up less than a single pixel — NASA says "only 0.12 pixel in size."
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. 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.
Voyager took similar pictures of Venus, Jupiter, Saturn, Uranus and Neptune, creating a portrait of the Solar System. 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. NASA compiled 60 images produced into a mosaic, called Family Portrait.
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.
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, paraphrasing Carl Sagan with the statement, "That's all we've got".