Item of sf/scientific Terminology named for a concept put forward by the physicist Freeman J Dyson. According to Dyson, the logical power source for a sufficiently advanced galactic civilization would derive from the reconstruction of its solar system into an artificial biosphere completely enclosing – and thus trapping the maximum possible energy output from – the local sun. This original concept should more properly be termed a Dyson Swarm, since Dyson had in fact conceived a dispersed shell of multiple orbiting habitats and/or energy collectors. In his own words: "A solid shell or ring surrounding a star is mechanically impossible. The form of 'biosphere' which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star."
In sf, authors naturally prefer the more dramatic option of a continuous sphere – a single Big Dumb Object or Macrostructure. This and related schemes, like the basic notion behind his own Ringworld (1970), are discussed by Larry Niven in his article "Bigger than Worlds" (March 1974 Analog; reprinted in A Hole in Space coll 1974). An sf novel which makes use of a shell-like Dyson sphere with a habitable interior is Bob Shaw's Orbitsville (1975); further speculations on the purpose of this artefact appear in sequels completing the Orbitsville trilogy. Shaw's friend James White's Federation World (stories August 1980, 4 January 1982 Analog; exp as fixup 1988) features a similar vast habitat expanded from spherical form with huge polar cones so that its edge-on aspect is "a diamond with rounded sides". The "Cuckoo" in Farthest Star (1975) by Frederik Pohl and Jack Williamson – whose habitable region is on the outside – is revealed in the sequel, Wall Around a Star (1983), to be a Dyson sphere. Larry Niven's hoop-shaped Ringworld (1970) is in effect a narrow strip cut from the equator of a hypothetical Dyson sphere; recognizing that this requires an impossibly strong material, Niven does not hesitate to introduce one. Bowl of Heaven (2012), by Niven and Gregory Benford, describes in considerable detail a bisected Dyson sphere which may be defined as a World Ship, as its trapped sun provides energy to move it through interstellar space. Colin Kapp fills our solar system with concentric Dyson spheres in his 1980s Cageworld sequence.
A further elaboration of the concept is the Matrioshka Brain, whose multiple Dyson shells enclose one another like the classic Russian matrioshka doll (as in Cageworld), and whose constituents are not dumb objects but smart matter (sometimes generically termed "computronium") – data spaces capable of supporting detailed Virtual Reality, vast numbers of Uploaded personalities, etc. One sf example of such gigantic computing facilities is the Solid State Entity in David Zindell's Neverness (1988). Charles Stross tracks the conversion of our solar system into a Matrioshka Brain in Accelerando (fixup 2005). [DRL]
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