In 1492, Columbus set out for 'Cipangu' and the Spice Islands. He never got where he was going, and never knew what he had found. In 1969 we went to the Moon and discovered Earth. Voyages of exploration are funny that way.
This should not have come as a surprise. A classic trope of travel literature is that wherever you go, what you truly discover is home, because only by going elsewhere can you place home in context. There and Back Again was Bilbo Baggins's name for the book we call The Hobbit, and as discussed in a comment thread last month, the true culmination of Lord of the Rings comes where its journey began, in the Shire.
So it is no accident that the first Earth Day was in 1969 – a few months before Apollo 11, but a few months after Apollo 8, when humans first ventured into lunar space and saw Earth above a moonscape. As I've mentioned here before, until we saw Earth from deep space we did not even know what our homeworld looks like – a planet of sworled blue and white, now so familiar, often with barely a hint of the land surface.
The space and environmental movements have not been on the best of terms, at any rate in the US, for a variety of reasons. Space boosters are big and noisy, not in and of themselves a particularly 'green' technology, but environmentalism as we know it would have been impossible without them. I first learned the word ecology from Heinlein books, and 'spaceship Earth' remains about as good a summary of environmental concerns as anything. If the life support system goes blooey, it is Houston that has a problem, along with every other place where humans now live. Environmentalism as we know it is a child of space travel.
We have continued to discover Earth in the 40 years since Apollo 11. Not by going back to the Moon, which we only did a handful of times before Apollo was canceled, but by going – albeit, so far, robotically - to other places. Missions have visited all eight major solar planets (sorry, Pluto!), with multiple landings on Mars and Venus, a journey into the clouds of Jupiter, and a landing on Titan. In all, a good start on exploring the Solar System. We've also continued to explore Earth itself from space. We have learned more about the weather from looking down at it than we'd ever have guessed from living below it. (Score one more for Arthur C. Clarke.)
Human spaceflight has turned out to be difficult, more difficult in sheer complexity and cost than anyone in the rocketpunk era imagined. The dangers were expected, and we have encountered them: catastrophes during liftoff and reentry; from fire; from crashing; from loss of air. We have learned that microgravity – contrary, this time, to Clarke – is not good for our breed. Progress, since Apollo, has been slower than the breakneck pace of the 1960s led us to expect. This is the historical norm: sudden leaps, followed by much longer periods of consolidation and maturation. (Which will be recapitulated by any interplanetary mission – minutes of thrill followed by months of tedium.)
And since Apollo, only the tragedies have been spectacular. (Well, any space launch is spectacular, but you know what I mean.) The successes have sort of sneaked up on us; it was a few years into the ongoing operation of the International Space Station before it fully hit me that we have a permanent space station. Half a thousand people have gone into space, for up to months at a time.
And the ISS is, among other things, a sort of tethered interplanetary mission. It doesn't look at all like our 'classical' bike-wheel image of a space station, but if you clapped a drive on one end it would look a great deal like an interplanetary ship. It has operated for nearly a decade with no critical emergency – the single most vital benchmark for going to Mars, or anywhere in the Solar System. Long duration spaceflight is achievable, not just in theory but in practice.
We have taken high specific impulse drive out of the lab and into space, flying deep space robotic missions using electric drive. A lot of development is need to scale it to a human mission, but we know that it works. Small step by small step, we are heading toward that first step onto the surface of Mars.
Bittersweet coda: Legendary CBS anchorman Walter Cronkite, heard in the clip above, died last Friday. His love of space exploration and the space program shone through his reporting; now he too has passed escape velocity. We will miss him – indeed, we have missed him for many years now. (The footage link is via Atrios' Eschaton, a political blog. You have been warned.)
Related links: Last year I reflected on the 39th anniversary of Apollo 11, and also – quite by coincidence – on the significance of space travel for our understanding of Earth.