Dyson englobement—
A Dyson sphere is a hypothetical megastructure that encompasses a star and captures a large percentage of its solar power output. The concept is a thought experiment that attempts to imagine how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Because only a tiny fraction of a star's energy emissions reaches the surface of any orbiting planet, building structures encircling a star would enable a civilization to harvest far more energy.
3D rendering of a Dyson sphere utilizing large, orbiting panels
The first modern imagining of such a structure was by Olaf Stapledon in his science fiction novel Star Maker (1937), in which he described "every solar system... surrounded by a gauze of light-traps, which focused the escaping solar energy for intelligent use". The concept was later explored by the physicist Freeman Dyson in his 1960 paper "Search for Artificial Stellar Sources of Infrared Radiation". Dyson speculated that such structures would be the logical consequence of the escalating energy needs of a technological civilization and would be a necessity for its long-term survival. Spheres detected in astronomical searches could be an indicator of extraterrestrial life, with different types of sphere and their energy-harvesting ability corresponding to levels of technological advancement on the Kardashev scale.
