So this moon, or rather “moon” since there's some debate over the terminology—and I’ll get to that in an moment—is called Cruithne (also known as asteroid 3753). I don’t remember where I actually heard about this second moon, although it was probably on NPR since that is where the majority of my information seems to filter in from. Anyway, I thought I would look into it...
Here are the findings: First off, it seems that Cruithne is not really a moon, because Earth and Cruithne are not gravitationally bound. A moon would actually orbit the planet, while Cruithne just shares the Earth's orbit around the Sun. It was discovered in 1986, although it took until the late nineties to figure out its orbit. Apparently, it’s up there careening around in some sort of crazy horseshoe pattern. Cruithne’s orbit will not cause it to crash into the earth. I find this reassuring.
So while I’m looking this up, I discover that there’s a bunch of other crap floating around up there. There are at least four Earth Coorbital Asteroids or "coorbitals" that share Earth's orbit. They are certainly catchily named: 2003 YN107, 2002 AA29, 2004 GU9, and 2001 GO2. Poetic.
So the best part of the story is that that they thought they found another one called J002E3. Only then they discovered this:
“J002E3's small size and unusual orbit suggest the object is no asteroid or other natural object, but a piece of man-made "space junk," possibly a piece of one of the Saturn V rockets that launched American astronauts to the moon during the Apollo program.”
Nice. Yeah, we thought that might be a planet or something, but it turns out that’s its just some trash we didn’t dispose of properly...
So my real problem doesn’t actually have any thing to do with any of that. What I want to know is why do we call the moon the moon? Other planets have moons (and coorbitlas for that matter) and most of them have names. Pretty ones: Triton, Nereid, Phoebe, Titan, Calypso, Ganymede…Jupiter has 39 moons for goodness sake. In fact, as you may note above, even the other stuff orbiting the earth has a name (or at least a number).
So why do we call the big white one up there the moon. That’s like saying, “I have this cat, and we are going to call him ‘the cat’. Now, all these other cats—who you may note are also cats—will have names like Midnight and Socks and Nutmeg and Steve.” What's that about? Makes no sense.