Artwork showing an advanced civilisation extracting energy from a black hole. Black holes are enigmatic objects, with gravitations pulls so strong that no light can escape them. Many of them, however, are surrounded by discs of gas and dust, the shredded remains of stars, nebulae and planets which got too close and were torn apart by tidal forces. In this illustration, an advanced civilisation has constructed a huge lattice-like structure around a black hole to extract energy from the matter swirling around in the accretion disc.