In what were arguably the greatest journeys of discovery ever undertaken, the two unmanned Voyager spacecraft gave us our first close-up looks at four of the outer planets and almost 60 moons. What were once points of light in the largest Earth-based telescopes suddenly became landscapes. As the Voyagers were reaching the edge of the Solar System, astronomer Carl Sagan suggested turning their cameras back to take one last picture of the planet from which they were launched. On February 14, 1990, from a distance of 6.4 billion kilometers, Voyager 1 captured this image of our Earth. Here the entire world fills only 0.12 pixel and appears as a tiny crescent of light. Because of the reflection of light off the spacecraft, Earth seems to be sitting in a beam of light, as if there were some special significance to this small world. But that is just an accident of geometry and optics. The apparent rays of light are not sunbeams, but scattering off the camera's optics, a result of pointing it so close to the Sun. Had the picture been taken a little earlier or a little later, there would have been no sunbeam highlighting the Earth. This is how the planets would look to an alien spaceship approaching the Solar System after a long interstellar voyage. From this perspective, there seems nothing remarkable about this pale blue dot. 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.
"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."
- Carl Sagan, Pale Blue Dot, Random House, 1994.