40 years ago today two human beings, a couple of American guys, became the first members of our species -- or, we can be reasonably sure, any species from this planet -- to set foot on another world.

As "other worlds" go, we were always lucky to have the moon, so big and yellow and tempting and sitting right there in our backyard. It only makes sense that our first steps into space would culminate in a journey there and back. Apollo 11 was a proof of concept. We are also fortunate to have so many interesting planets and moons (as well as asteroids, comets, and hard-to-classify stuff flying out there in and beyond the Oort Cloud) orbiting the sun with us. Apollo 11 was the first step towards our reaching out to explore all of them...and beyond.

Sure, we can argue about whether we went to the moon the right way. Working from earth orbit (rather than lunar orbit) with reusable spacecraft would have almost certainly been a better model. If we had built the space shuttle and a space station before going to the moon, we would understand better why we have those things. Rather than being these odd anticlimactic artifacts, symbols of the long decline of our manned exploration of space, they would have been the core infrastructure for pushing outward. In that model, sub-orbital flights lead to orbital flights, leading to a permanent presence in orbit, leading to moon missions, leading to a permanent presence on the moon and, at the same time, missions deeper into space.

Of course, even had we chosen to get there using such a model, there's no guarantee that we wouldn't have abandoned our spacefaring ambitions soon after that first trimuphant moon landing. The reason that a national deprioritization of space exploration was all but inevitable has to do with the other big argument people like to get into about that first flight to the moon: that we went there for the wrong reasons. The Commies had beaten us into space. We needed to take an an unambiguous lead in the space race, show 'em who's boss. So we chose to go to the moon...

...which, unfortunately, meant that the whole enterprise had a one-off, stunt-like quality to it. We didn't need a space shuttle or a space station -- we needed a great big enormous white rocket with "USA" emblazoned on the side. We went with the lunar orbit model because it was cheaper and we could make it happen faster. We didn't need to worry about infrastructure or where we would go next. There was no tomorrow -- we were going to the moon!

I think the problem with arguing about how we went or why we went is that it ignores the likely alternative to going to the moon the way we did, for the reasons we did. The likely alternative is not that we would have gone a different way, for a different set of reasons. The likely alternative is that we never would have gone.

Imagine a version of the year 2009 in which an eventual trip to the moon is as ephemeral and unlikely a notion as a return to the moon (or a manned mission to Mars) is in our timeline. We should celebrate Apollo 11 whole-heartedly. It was the first step, even if the next step is going to be much later coming than many of us would have liked. And what a glorious first step it was.

Happy Moonday, all. If you're interested in reliving the event in real-time, Ken B. suggests checking out this site.