To fulfil their colossal energy requirements, advanced alien civilizations might build energy harvesting megastructures around black holes, a study has proposed.

While black holes are notorious for having such a strong gravitational pull that not even light can escape them, they also produce energy in a number of different ways.
Researchers from the National Tsing Hua University in Taiwan explored if any of these energy sources could theoretically be harnessed to power a civilisation.
Three give enough radiation to be viable — the surrounding gas cloud, disc of matter spiralling into the hole and the intense jets that shoot out along the axis of rotation.
These could be captured using so-called ‘Dyson spheres’, which were originally conceived as a theoretical way to better capture energy from a star like our sun.
However, the team calculated, black holes could provide as much energy as the total output of 100,000–100,000,000 suns — but all from one single cosmic body.
If Dyson spheres exist, they would emit a characteristic signal we could detect, thanks to the waste heat produced as they convert energy into a useable form.
In fact, traditional Dyson spheres — those around suns — have long been a target in the search for extraterrestrial life. To date, however, none have been found.
To fulfil their colossal energy requirements, advanced alien civilizations might build energy harvesting megastructures around black holes, a study has proposed
Energy from a black hole could be captured using so-called ‘Dyson spheres’, which were originally conceived as a theoretical way to better capture energy from a star like our sun (as depicted in this artist’s impression). Despite their name, they would not be a rigid sphere — as this would be impossible to build around a star — or a black hole — but would most likely be made of up a network of satellites encircles their host
DYSONS SPHERES
Dyson spheres are theoretical megastructures which, as they were first conceived, might be built around stars to better harness their energy.
Despite their name, a rigid sphere would be impossible to build around a star — or a black hole — because of the pressure and gravitational forces.
Instead, they are typically imagined as being made of a network of satellites that encircles their host in either a ring, sphere or swarm-like arrangement.
Humanity does not have the capabilities at present to build a Dyson sphere — but might one day.