A Dyson sphere is an idea about a structure that surrounds a star, first thought up by physicist Freeman Dyson, and then used in some science fiction works.
The idea of the Dyson sphere was the result of a thought experiment. Dyson noted that civilizations constantly increased their need for energy. He reasoned that as human civilization went on, there would come a time when it demanded more energy than the Earth could provide.
He proposed a system of structures designed to intercept and collect all energy produced by the Sun. Dyson's proposal did not detail how such a system would be constructed. His 1960 paper "Search for artificial stellar sources of infra-red radiation", in the journal Science, was the first to present the concept of the Dyson sphere.
There are at least three types of Dyson spheres:
- A Dyson shell that is a solid structure and the inside could even become habitable if the sphere produces artificial gravity by spinning on itself. It would be extremely difficult, if not impossible to build (particularly because of the enormous quantity of material needed, the instability of the sphere and the strong gravity of the star affecting the whole structure).
- A Dyson swarm, which is not exactly a sphere, but millions of smaller bodies orbiting the star and thus forming a more or less spherical structure around it. The most physically realistic structure to build.
- A Dyson bubble that is made up of small bodies (like a Dyson swarm), but linked together with an extremely light and thin (but very large) structure such as a light sail around a star that keeps it centered because of stellar winds.
A far bigger Dyson sphere would be a Birch World