The Penrose process (also called Penrose mechanism) is theorised by Roger Penrose as a means whereby energy can be extracted from a rotating black hole. That extraction can occur if the rotational energy of the black hole is located not inside the event horizon but outside in a region of the Kerr spacetime called the ergosphere in which any particle is necessarily propelled in locomotive concurrence with the rotating spacetime. All objects in the ergosphere become dragged by a rotating spacetime.