Of all the space photos NASA has ever made, there are a few that are as iconic as an image Voyager took looking back at Earth from Saturn. It's a picture known among space nerds as the 'Pale Blue Dot.'
Its notoriety is largely due to Carl Sagan, who put the image on his show, Cosmos, and rapturously contrasted the smallness of Earth in space with the profusion of everythingness that the human perspective sees on this planet.
From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Consider again that dot. That's here. That's home. That's us. On it, every one you love. Every one you know. Every one 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 saint and sinner in the history of our species lived there, on the mote of dust, suspended in a sunbeam.
If gorgeous blue-and-green whole-Earth photos emphasize the uniqueness of humans' home, the pale blue dot provides "an alien view of Earth." You are here, it says, and that is nowhere in astronomical terms.
For most, or for me, at least, that could inspire existential dread. But the glory of Sagan is that it never did. Wonder, rapture: Those were his modes.
Carolyn Porco, who heads the imaging team for the Saturn-orbiting Cassini experiment, is an astronomer in the Sagan mold. She is a poet of space, prone to fits of awe and expansiveness on her blog, which she calls, "Captain's Log."