To keep the ball rolling on promoting her new album, Femme Fatale, Britney Spears has unleashed her second video, this time for "Till the World Ends." It takes us to a postapocalyptic dance club, complete with meteors, sweat, and a whole lot of writhing. It's a bit reminiscent of "I'm a Slave 4 U," but with fewer of Britney's signature moves. Still, the pop star looks gorgeous and genuinely seems to be having a good time. Plus, there's no denying that the song is one of the most infectious tracks on the album.