It's like describing a dog to someone who's never seen a dog. And then asking them to draw it.

This photo is known as The Pale Blue Dot. It was taken by Voyager 1, a space probe meant to explore the outer reaches of the solar system. Far from dying, she's still out there doing her job and is the furthest human made object from Earth.

In the mid 80's, they knew Voyager 1 would soon pass beyond where her cameras would matter and she needed to save power, so the question became: what's the last thing she should take a picture of?

Carl Sagan and Carolyn Porco both independently had the same thought: take a picture of Earth. Us. Yes, it would be essentially just one pixel. It wouldn't be scientifically useful. It might even damage the camera because of how intense the sun is, even forty times as far from Earth as Earth is from the Sun. But they got it sorted because it's NASA.

3.7 million (not billion) miles away, that's Earth. Caught in bands of light, artifacts of the Sun's incredible power even 4 million miles away. We are an island in a sea of radiation and vacuum and it's all we have.

I can't say it better than Sagan did, so I'll let you alone with his words:

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 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