Did NASA really spend millions creating a pen that would write in space? Is chocolate poisonous to dogs? Does stress cause gray hair?

These questions are a sample of the urban lore investigated in this audiobook, Fact or Fiction: Science Tackles 58 Popular Myths. Drawing from Scientific American's "Fact or Fiction" and "Strange But True" columns, we've selected fifty-eight of the most surprising, fascinating, useful, and just plain wacky topics confronted by our writers over the years.