“Holy shit, Tranquility.”

Forty years ago today — 11 years before I was born — Neil Armstrong stepped off the ladder of the LM Eagle and became the first human to ever step foot onto a celestial body. Stop and think about that for a minute. For uncounted millennia, people had looked up at these strange lights in the sky, weaving fantastic yarns to explain their origin and composition. But now we were there. It really was one giant leap for mankind. Throughout my life, it's served as an inspiration. At one point in my youth, in fact, I wanted to join NASA and get onto the first manned mission to Mars. I had it all planned; on the way there, I'd convince everyone else to go along with the plan. Whether it was me or not who stepped off the ladder first and made the historic speech didn't matter, but whoever it was would step onto the Martian regolith, start in with the speech, and then interrupt his or herself, saying something like "Did you see that? I swear that rock just moved!" Then a black form would zoom by the camera, and the screams would start. More forms zoom by the camera, one of them knocking it over; and as the screams grew to a crescendo, we'd cut the feed back to Earth, coming back on 8 hours later to cheerfully say "Only kidding!" and getting on with the mission as normal while the people of Earth recover from their collective heart attack. I mean, come on, we'd be on Mars! Who would be able to stop us? It would have been glorious.

I love photographs of the Earth, especially the Earthrise photos, like the one above taken during the Apollo 11 mission. In a commencement address delivered on 11 May, 1996, Carl Sagan summed up perfectly the things I think and feel whenever I look at a photo of the Earth:

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.

That's a perspective that humanity would not have ever conceived if it weren't for the drive to explore other worlds. And because of that, it's incredibly frustrating how we've essentially been trapped in low Earth orbit since the close of the Apollo missions. Sure, we've been able to expand our understanding through the use of robots, but the sky beckons us to follow them in their venture to other worlds. Kim Stanley Robinson's Red Mars makes well the case for human exploration. (And Martian terraformation; but even though the book takes place on Mars, if you substituted "Mars" for "Luna" the argument would still hold.)

The beauty of Mars exists in the human mind. Without the human presence it is just a concatenation of atoms, no different than any other random speck of matter in the universe. It's we who understand it, and we who give it meaning. All our centuries of looking up at the night sky and watching it wander through the stars. All those nights of watching it through the telescopes, looking at a tiny disk trying to see canals in the albedo changes. All those dumb sci-fi novels with their monsters and maidens and dying civilizations. And all the scientists who studied the data, or got us here. That's what makes Mars beautiful. Not the basalt and the oxides.

Now that we are here, it isn't enough to just hide under ten meters of soil and study the rock. That's science, yes, and needed science too. But science is more than that. Science is part of a larger human enterprise, and that enterprise includes going to the stars, adapting to other planets, adapting them to us. Science is creation. The lack of life here, and the lack of any finding in fifty years of the SETI program, indicates that life is rare, and intelligent life even rarer. And yet the whole meaning of the universe, its beauty, is contained in the consciousness of intelligent life. We are the consciousness of the universe, and our job is to spread that around, to go look at things, to live everywhere we can. It's too dangerous to keep the consciousness of the universe on only one planet, it could be wiped out. And so now we're on two, three if you count the moon. And we can change this one to make it safer to live on. Changing it won't destroy it. Reading its past might get harder, but the beauty of it won't go away. If there are lakes, or forests, or glaciers, how does that diminish Mars's beauty? I don't think it does. I think it only enhances it. It adds life, the most beautiful system of all. But nothing life can do will bring Tharsis down, or fill Marineris. Mars will always remain Mars, different from Earth, colder and wilder. But it can be Mars and ours at the same time. And it will be. There is this about the human mind; if it can be done, it will be done. We can transform Mars and build it like you would build a cathedral, as a monument to humanity and the universe both. We can do it, so we will do it. So we might as well start.

And so we might as well finish what we've started, 40 years ago today.