http://imgs.xkcd.com/comics/turnabout.png

Trust me, this is very funny. And after the week we had last week in space-travel news, a little levity is called for.

(Oh, all right, for those who don’t get it: The Apollo retroreflectors are essentially mirrors that were left behind on the lunar surface by the Apollo astronauts. If you bounce a laser beam off them, you can measure very precisely the distance from the Earth to the Moon. They’re also a nice refutation for all the crackpot theories that the Apollo missions were faked, because the mirrors are there, and their locations are known. If you can get a hold of a powerful enough laser, you too can do a little rangefinding of your own. And if the retroreflectors weren’t placed there by astronauts, where did they come from, hmmmm?)