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Dyson Spheres
This nOde last updated July 1st, 2003 and is permanently morphing...
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The Dyson sphere (or Dyson shell) was originally proposed in 1959 by the astronomer Freeman Dyson in "Search for Artificial Stellar Sources of Infrared Radiation" in Science as a way for an advanced civilisation to utilise all of the energy radiated by their sun. It is an artificial sphere the size of an planetary orbit. The sphere would consist of a shell of solar collectors or habitats around the star, so that all (or at least a significant amount) energy will hit a receiving surface where it can be used. This would create a huge living space and gather enormous amounts of energy.

A Dyson sphere in the solar system, with a radius of one AU would have a surface area of at least 2.72e17 km^2, around 600 million times the surface area of the Earth. The sun has a energy output of around 4e26 W, of which most would be available to do useful work.

The original proposal simply assumed there would be enough solar collectors around the star to absorb the starlight, not that they would form a continuous shell. Rather, the shell would consist of independently orbiting structures, around a million kilometres thick and containing more than 1e5 objects. But various science fiction authors seem to have misinterpreted the concept to mean a solid shell enclosing the star, usually having an inhabitable surface on the inside, and this idea was so compelling that it has been the main use of the term in science fiction. The earliest appearance of this version seems to be Robert Silverberg's novel _Across a Billion Years_.

A third kind of shell would be very thin and non-rotating, held up by the radiation pressure of the sun. It would consist of statites. Essentially it is a "dyson bubble", where reflecting sails reflect light onto collectors for use in external habitats. Its mass would be very smalll, on the order of a small moon or large asteroid.

 - Anders Sandberg from the Dyson Spheres FAQ

• minimal techno track _Star Machine_ MP3 (192k) by Stewart Walker off of _Artificial Music For Artificial People_ 12" on Mosquito #012 (1998)
  • minimal tech house track _Star Machine (Si Begg Remix)_ MP3 (192k) off of same

The Dyson Scenario: Life expands into the universe, which is open. As the universe cools, life stores energy to survive (do information processing). It waits until the universe is cool enough, performs some processing with part of its energy stores, then waits until the universe has cooled so much that the remaining energy can be used to do an equal amount of computation, and so on. - Terminology from The Omega Point Theory Mailing List