our pale blue dot

“The Cosmos extends, for all practical purposes, forever. After a brief sedentary hiatus, we are resuming our ancient nomadic way of life. Our remote descendants, safely arrayed on many worlds throughout the Solar System and beyond, will be unified by their common heritage, by their regard for their home planet, and by the knowledge that, whatever other life may be, the only humans in all the Universe come from Earth. They will gaze up and strain to find the blue dot in their skies. They will love it no less for its obscurity and fragility. They will marvel at how vulnerable the repository of all our potential once was, how perilous our infancy, how humble our beginnings, how many rivers we had to cross before we found our way.”


Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space


Graphic - Dan McPharlin

17 years ago, a robot took the most important photograph of our planet:

Can’t see it? We’re just a pale blue dot – making up less than a twentieth of a pixel in angular diameter in this image, far too small to be resolved as a disc. It’s shining brightly enough to be detected, but only because it reflects the intense light of a far more massive body, the sun. The sun’s light is already close to drowning it out. 

The reason why it’s important, to me at least, is because it gives us a jarring sense of scale. Almost all of human history – and maybe all of the history of life itself – happened on the surface of that speck of dust. Everything you’ve ever experienced happened on that tiny little dot. Everyone you know – everyone you’ve ever heard of – lived or still lives within that pixel.

Carl Sagan requested this photo be taken from Voyager 1 as part of a family portrait of our Solar System. Seeing this photo, and realizing how insignificant our lives are in relation to the vast expenses of the universe, is an experience I think everyone should share.

The most striking part, to me, is that if none of humanity was present when the picture was taken, the pale blue dot would still look exactly the same.

Just keep in mind that we have no other place to go.

“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.

- Carl Sagan 

I have been reading Sagan’s “Pale Blue Dot” with ferocity this week. In it, he works to try and juxtapose the reality of Earth’s insignificance in the Universe, with our own pretentious, imagined self importance. 

There is a great story about this photo, Sagan insisted that the Voyager 1, which was en route to places beyond our understanding, take a moment to turn around and take this photo from 3.7 million miles from earth. It was a risky maneuver that had no real scientific importance to our world. The Voyager 1 had important scientific work to complete, and spending a month taking tourists photos of home seemed like an indulgence. 

Sagan, persisted, insisted. He thought by showing how small in insignificant our little spec of dust we call home is, that it might inspire the inhabitants of it to be a little kinder to each other. It’s a scary and beautiful thing to realize that we really aren’t so important, aren’t so special, so today I am sitting in a tiny corner of a tiny dot, thinking about his words:

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.


Why does Earth appear blue from space?

“The fact is that the ocean is made up of water molecules, and water — like all molecules — preferentially absorbs certain wavelengths of light. The easiest wavelengths for water to absorb are infrared, ultraviolet and red light. This means if you head down to even a modest depth, you won’t experience much warming from the Sun, you’ll be protected from UV radiation, and things will start to turn blue, as the red light is taken away.”

Seen from afar, Earth is often described as a pale blue dot. But why is our planet blue? Is it because the skies are blue? That can’t be right, or the clouds and icecaps would appear blue-hued as well. Is it because the blue skies are reflected by the oceans? That can’t be right either, or we wouldn’t see different shades of blue at different oceanic depths. The answer lies in the properties of water itself: it absorbs different wavelengths of light with different efficiencies, and is worst at absorbing blue light. That’s why, the deeper you go, the bluer underwater marine life appears, and that’s also why the blue light is most efficiently reflected back off the water, at all depths, and into space. The Earth may not be our Solar System’s only blue planet, but the physics of its blueness is unique!

Before we invented civilization our ancestors lived mainly in the open out under the sky. Before we devised artificial lights and atmospheric pollution and modern forms of nocturnal entertainment we watched the stars. There were practical calendar reasons of course but there was more to it than that. Even today the most jaded city dweller can be unexpectedly moved upon encountering a clear night sky studded with thousands of twinkling stars. When it happens to me after all these years it still takes my breath away.
—  Carl Sagan, ‘Pale Blue Dot’