Or more accurately, an asteroid?
The closest approach by an asteroid recorded happened about nine hours ago. Now corny movies with Bruce Willis and Ben Affleck aside, this brings home the fact that space is well, not all that spacious sometimes.
There's all sorts of crap floating around up there, knocking into other crap that's floating up there along with it. Kind of like how my brain works most days. But some days, just by random chance, there are more things knocking about in one spot than there are on others, and it's those days when, at least in my brain, good things happen. Out in space--or at least, the immediate neighborhood, things knocking against each other can be downright catastrophic.
Now the size of space dictates that the likelihood of crap crashing into us shrinks exponentially. But a million to one chance still is pretty likely, given the number of chances in the universe makes a million feel like significantly smaller of a number.
Where am I going with all this? Philosophy. When something like this comes along, no matter how small or large of a chance of its happening--its meaning bears a significance that has nothing to do with chance.