Have you ever heard of the planet Vulcan? There’s a good chance you haven’t, because it doesn’t exist. In the 4th episode of Think Like A Scientist, MIT professor of science writing Tom Levenson retells the amazing history of planet Vulcan - a story that reveals how the power of an idea can sometimes lead researchers down the wrong path. Meanwhile, experimental particle physicist Melissa Franklin explains how lessons learned from Vulcan apply to research today, and how, in the end, science usually gets things right. Animations by Dustin Grella.