Stealing Black Hole's Energy

Due to angular momentum, when really massive spinning stars collapse to form black holes, they start spinning faster and faster. In fact, some black holes spin millions of times a second. This spinning creates a volume of dragged space-time called the ergosphere, which is escapable. Theoretically, any injected matter could capture some of the spinning black hole's angular momentum. British mathematician Roger Penrose hypothesized a way to steal some energy from a rotating black hole by injecting matter into the ergosphere and capturing some of the spinning black hole's angular momentum.