The Physics of a Better Shadow

Take a perfectly round disk, hold it up to a beam of light, and look at the very center of its shadow. There's a bright spot sitting there, in the one place that should have been the darkest of all. It's a piece of physics more than two centuries old, and it's the reason you cannot hide a star behind a simple screen: the starlight bends around the edge and rebuilds itself right where you wanted to put a planet. So the fix isn't a bigger screen. It's a stranger one, shaped like a flower — and the reason it works leads to a strange realization, that much of the difficulty of photographing another Earth isn't a fixed price the universe charges, but a consequence of where you choose to stand when you block the light.