Quantum theory dictates that the entanglement required to link all the particles outside the black hole precludes those particles from also linking up with particles inside the black hole. That trick transformed a confusing mess of Hawking particles — paradoxically entangled with both a black hole and each other — into two black holes connected by a wormhole. In the June Journal of High Energy Physics, Preskill’s team showed how the entanglement of multiple particles on a holographic boundary perfectly describes a single particle being pulled by gravity within a chunk of anti-de Sitter space.