Can You Steal Energy From A Black Hole? #VeritasiumContest

The video was created by Shane Farnsworth and Claudio Paganini. Check out the Escaped Sapiens Podcast and consider subscribing for in-depth conversations with researchers on topics ranging from the de-extinction of animal species to the colonization of Mars. In this video we explain the Penrose Process, which describes a way of extracting energy from a rotating black hole.

As a black hole rotates it drags spacetime along with it. Close to the event horizon there is a region known as the ergoregion within which this dragging effect is so strong that it is impossible for an object to remain stationary with respect to an outside observer looking on from a great distance. In order to do so the object would need to move at faster than light speed with respect to the local spacetime, which is not possible. The Penrose Process describes an object entering the ergoregion and then breaking up into two pieces, with one piece escaping back out of the ergoregion, and the other falling into the event horizon. With careful arrangement, the escaping piece of matter can be made to have greater energy than the original combined piece of matter, and the infalling piece gets negative energy. The difference in energy for the outgoing object is provided by the black hole itself, which suffers a decrease in its mass and angular momentum as it absorbs the infalling object with negative energy.

At a more technical level, the reason the Penrose Process works is because on entering the ergoregion the usual time coordinate becomes flipped with one of the spatial coordinates. The result is that the vector field that encodes the stationarity of the spacetime (i.e. directions along which the space-time doesn’t change in time) becomes spacelike. The vector field that encodes the stationarity of the spacetime is the vector with respect to which energy is defined. Massive objects can only travel forward in time-like directions, which means that the worldline of a massive object far from a spinning black hole must be aligned with the timelike vector field that encodes the stationarity of the space-time, with the result that its energy is always positive. Inside the ergoregion where the vector field that encodes the stationarity of the spacetime is space-like, objects are able to travel along trajectories with tangent vectors anti-aligned with this vector field. An observer at infinity perceives these trajectories as having negative total energy.

►For a technical description of the Penrose process see Chapter 2.3 of Claudio Paganini’s doctoral thesis:

[nikkimac]

Love the animation, makes it easier to understand

[DanielOgburn]

If a cat was harmed, we wouldn't know once it passes the event horizon?

[gerddeiter]

So is this a solution for the planet's 'Waste' and a simultaneous energy source? Whats the distance between earth and the closest black hole?