Dyson Sphere

The Dyson sphere (or Dyson shell) was originally proposed in 1959 CE by the astronomer Freeman J. Dyson in "Search for Artificial Stellar Sources of Infrared Radiation" in Science as a way for an advanced civilization to utilize all of the energy radiated by their sun. It is an artificial sphere the size of a 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 would 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$$ 2.72 x 10^1^7 km^2$$, around 600 million times the surface area of the Earth. The sun has an energy output of around$$ 4 x 10^2^3 kW $$, 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 kilometers square and containing more than 100,000 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. 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 – a solar sail that hovers without orbiting above the sun. Essentially it is a "dyson bubble", where reflecting sails reflect light onto collectors for use in external habitats. Its mass would be very small, on the order of a small moon or large asteroid. In the following I will call solid Dyson spheres Type II or dyson shells and independently orbiting spheres Type I.