The concept of a Dyson sphere was created by Freeman Dyson, but it is acknowledged that the idea was based mainly on the writings of Olaf Stapledon.
Personal facts
Freeman Dyson was born in 1923 in the UK, the second child of Mildred Lucy Atkey and George Dyson (later Sir Dyson).
He studied physics as well as pure mathematics at Trinity College, Cambridge. After working for the military (Royal Air Force) during World War II, he returned to Cambridge and started to concentrate on theoretical physics, although he was still active in mathematics
Dyson moved to the USA in 1947, where he soon joined Oppenheimer at Princeton, and eventually became professor of physics until his retirement in 1994.
Dyson was a very talented scientist but was also capable of engaging the average man. He wrote on a diverse number of topics in addition to his many academic publications, and it is in this milieu that he proposed the concept of the Dyson Sphere.
The concept
In short, Freeman Dyson speculated about the possibility of an interplanetary civilisation harnessing the complete radiation output of its sun by postulating that such a civilisation could create an artificial biosphere that completely encapsulates their sun and absorbs all of its radiated energy. This envelope of artificial creation that orbits the sun and contains the habitation of that civilisation came to be known as a Dyson sphere.
A Dyson Sphere is therefore a hypothesis or an abstraction, and does not exist (as far as is known) in reality. He also speculated that, when searching for other civilisations in outer space it would be a feasible objective to search for such a system where a sun is surrounded by artificial structures. It would be detectable because the waste energy (heat) would be radiated outside the sphere as infrared. This idea of searching for infrared radiation points to locate other civilisations was actually the main thrust of the article.
Dyson did not visualise this plethora of artificially created objects as spherical in shape although he did use the term biosphere, but he also used the term “shell.” It is the science fiction writers who used this concept in their books who dubbed it a “Dyson sphere”.
An example of fiction about the Dyson Sphere idea is found here.
The nitty gritty
Dyson’s article, which appeared in the popular magazine Science (Dyson, F.J. 1960. “Search for Artificial Stellar Sources of Infra-Red Radiation”. Science 131 (3414): 1667–1668) was due to Dyson’s thought experiment which could be formalised as “What would happen when civilisation’s need for energy just keeps increasing?” (This is the author’s understanding of the premise of the article).
He theorised that a technologically advanced civilisation could break up the planets in their solar system into a shell of orbiting planetoids that would be able absorb all of the energy emitted by the central sun, due to the vastly increased surface area of said planetoids.
These structures would be habitable due to the huge amount of energy available (and due to the unimaginable technological prowess of such a civilisation) and thus would support an energy-hungry civilisation. The waste heat would be radiated away from the system into outer space in the form of infrared radiation and would be detectable by man-made instruments. This later became known as a Type II Kardashev civilization (read more about this in Wikipedia).
Variants
Today there are several theoretical variants of the Dyson shell because there are several practical problems regarding the initial idea.
These variants are called the Dyson swarm, Dyson bubble and Dyson shell.
