Ask The Bad Astronomer

Astronomer, author, columnist, and successful populizer of science Phil Plait, perhaps best known as The Bad Astronomer, is a regular sight on Slashdot for his unusual ability to find lucid explanations of esoteric scientific claims and controversies. Phil has graciously agreed to answer Slashdot readers' questions, so ask him below about space, science, debunking conspiracy claims, and anything else that makes sense. Asking more than one question is fine (and encouraged!), but please separate unrelated questions into separate posts, lest your questions be moderated down.