On theKardashev scale, Type II and Type III civilizations can harness energy on the required scale.[2][3] This can allow them to constructmegastructures.
AnAlderson disk[5] (named afterDan Alderson, its originator) is a hypothetical artificialastronomicalmegastructure, a giantplatter with a thickness of several thousand miles. TheSun rests in the hole at the center of the disk. The outer perimeter of an Alderson disk would be roughly equivalent to the orbit ofMars orJupiter.
In theRingworld series byLarry Niven, a ring a million miles wide is built and spun (to simulate gravity) around a star roughly oneastronomical unit away. The ring can be viewed as a functional version of aDyson sphere with the interior surface area of 3 million Earth-sized planets. Because it is only a partial Dyson sphere, it can be viewed as a construction of a civilization intermediary between Type I and Type II. Both Dyson spheres and the Ringworld suffer from gravitational instability, however—a major focus of the Ringworld series is coping with this instability in the face of partial collapse of the Ringworld civilization.
TheMorlocks ofStephen Baxter'sThe Time Ships occupy a spherical shell around the Sun the diameter of Earth's orbit, spinning for gravity along one band. The shell's inner surface along this band is inhabited by cultures in many lower stages of development, while the K II Morlock civilization uses the entire structure for power and computation.[6]
In theHalo universe, theForerunners created many planet-sized artificial megastructures, such as the Halo ringworlds, the two Arks, and the Shield Worlds, which were micro-Dyson spheres. One of the Precursors' most well known creations were the Star Roads: immense, indestructible cables that connected planets and star systems.
In the movieElysium, a large-scale space habitat has been built to orbit Earth and is capable of sustaining life permanently.
In theCorellian Trilogy (Star Wars Legends books), the Corellian system is revealed to have been constructed by an unknown ancient civilization, using Centerpoint Station to transport the planets across interstellar distances, and "planetary repulsors" to maneuver the planets into their orbits.
InIain M. Banks' fictionalCulture universe, an Orbital is a purpose-builtspace habitat forming a ring typically around 3 million km (1.9 million miles) in diameter. The rotation of the ring simulates both gravity and a day-night cycle comparable to a planetary body orbiting a star.
TheDyson shell is the variant of the Dyson sphere most oftendepicted in fiction. It is a uniform solid shell of matter around the star, as opposed to a swarm of orbiting satellites.[8] In response to letters prompted by some papers, Dyson replied, "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 travelling on independent orbits around the star."[9]
^Dyson, Freeman J. (1966). Marshak, R. E. (ed.). "The Search for Extraterrestrial Technology". Perspectives in Modern Physics. New York: John Wiley & Sons.
^Dyson, Freeman J. (1966). "The Search for Extraterrestrial Technology". In Marshak, R. E. (ed.).Perspectives in Modern Physics: Essays in Honor of Hans Bethe. New York: John Wiley & Sons.Bibcode:1966pmp..book..641D.
^Dyson, F. J.; Maddox, J.; Anderson, P.; Sloane, E. A. (1960). "Letters and Response, Search for Artificial Stellar Sources of Infrared Radiation".Science.132 (3421):250–253.doi:10.1126/science.132.3421.252-a.PMID17748945.
