A theory proposed 50 years ago to explain how energy might be harvested from a black hole was verified by an experiment. Scientists from the University of Glasgow were able to provide first proof for an idea from 1969 by the famed British physicist Roger Penrose, who predicted that only an advanced alien civilization would be able to get energy in the black hole's ergosphere – the outer layer of its event horizon.
Why would it take aliens to do this? Penrose thought that if you lower an object into the ergosphere, you could produce negative energy. But for this to work, the object would have to be moving faster than the speed of light. Penrose envisioned a mechanism that would split an object dropped into the black hole in two, with one part going into the hole while the other would be recovered. As explains the press release from the University of Glasgow, the recoil generated by this process would result in the saved half gaining energy from the black hole's rotation.