raincoat of invisibility, The

Dumbledore gives one to Harry, who uses it to sneak into the restricted section of the Hogwarts library. The Lady Galadriel gives one to Frodo, who uses it to hide from Sauron's troops outside the Black Gates of Mordor. What is it? A cloak of invisibility, of course.

Total fiction, right? Violates basic scientific principles, right?

Not necessarily. Think of it this way. To be invisible, all you have to do is look like whatever is behind you at the time. So if you're in a library, you need to look like shelves of books, and if you're outside Mordor, you need to look like boulders.

How do you make yourself look like whatever is behind you? It's not that hard. You stick a camera onto your back, and you project what it sees onto your front. You just have to go around in an outfit made of reflective stuff, like this green raincoat made by Susumu Tachi, a professor at Tokyo University.

How good is the raincoat of invisibility? It does make people look wavery, ectoplasmic, and-well-not all there. But we don't think you'd want to rely on it to escape detection by a Filch or an Easterling.