A Dyson sphere is a hypothetical megastructure that encompasses a star and captures a large percentage of its solar power output. The concept is a thought experiment that attempts to imagine how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Because only a tiny fraction of a star's energy emissions reaches the surface of any orbiting planet, building structures encircling a star would enable a civilization to harvest far more energy.
Ringworld is a 1970 science fiction novel by Larry Niven, set in his Known Space universe and considered a classic of science fiction literature. Ringworld tells the story of Louis Wu and his companions on a mission to the Ringworld, an enormous rotating ring, an alien construct in space 186 million miles in diameter. Niven later wrote three sequel novels and then cowrote, with Edward M. Lerner, four prequels and a final sequel; the five latter novels constitute the Fleet of Worlds series. All the novels in the Ringworld series tie into numerous other books set in Known Space. Ringworld won the Nebula Award in 1970, as well as both the Hugo Award and Locus Award in 1971.
The Kardashev scale is a method of measuring a civilization's level of technological advancement based on the amount of energy it is capable of harnessing and using. The measure was proposed by Soviet astronomer Nikolai Kardashev (1932–2019) in 1964 and was named after him.
Orion's Arm is a multi-authored online science fiction world-building project, first established in 2000 by M. Alan Kazlev, Donna Malcolm Hirsekorn, Bernd Helfert and Anders Sandberg and further co-authored by many people since. Anyone can contribute articles, stories, artwork, or music to the website. A large mailing list exists, in which members debate aspects of the world they are creating, discussing additions, modifications, issues arising, and work to be done.
Star lifting is any of several hypothetical processes by which a sufficiently advanced civilization could remove a substantial portion of a star's matter which can then be re-purposed, while possibly optimizing the star's energy output and lifespan at the same time. The term appears to have been coined by David Criswell.
A matrioshka brain is a hypothetical megastructure of immense computational capacity powered by a Dyson sphere. It was proposed in 1997 by Robert J. Bradbury (1956–2011). It is an example of a class-B stellar engine, employing the entire energy output of a star to drive computer systems. This concept derives its name from the nesting Russian matryoshka dolls. The concept was deployed by Bradbury in the anthology Year Million: Science at the Far Edge of Knowledge.
An Alderson disk is a hypothetical artificial astronomical megastructure, like Larry Niven's Ringworld and the Dyson sphere. The disk is a giant platter with a thickness of several thousand miles. The Sun rests in the hole at the center of the disk. The outer perimeter of an Alderson disk would be roughly equivalent to the orbit of Mars or Jupiter. According to the proposal, a sufficiently large disk would have a larger mass than its Sun.
A megastructure is a very large artificial object, although the limits of precisely how large vary considerably. Some apply the term to any especially large or tall building. Some sources define a megastructure as an enormous self-supporting artificial construct. The products of megascale engineering or astroengineering are megastructures.
Megascale engineering is a form of exploratory engineering concerned with the construction of structures on an enormous scale. Typically these structures are at least 1,000 km (620 mi) in length—in other words, at least one megameter, hence the name. Such large-scale structures are termed megastructures.
The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
Stellar engines are a class of hypothetical megastructures which use the resources of a star to generate available work. For instance, they can use the energy of the star to produce mechanical, electrical or chemical work or they can use the impulse of the light emitted by the star to produce thrust, able to control the motion of a star system. The concept has been introduced by Bădescu and Cathcart. The variants which produce thrust may accelerate a star and anything orbiting it in a given direction. The creation of such a system would make its builders a type-II civilization on the Kardashev scale.
Stellar engineering is a type of engineering concerned with creating or modifying stars through artificial means.
An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are often the result of circumstellar dust heated by starlight and reemitted at longer wavelengths. They are common in young stellar objects and evolved stars on the asymptotic giant branch or older.
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a significant amount of jargon.
Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or present technology. Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not. Some authors prefer to exclude radio transmissions from the definition, but such restrictive usage is not widespread. Jill Tarter has proposed that the search for extraterrestrial intelligence (SETI) be renamed "the search for technosignatures". Various types of technosignatures, such as radiation leakage from megascale astroengineering installations such as Dyson spheres, the light from an extraterrestrial ecumenopolis, or Shkadov thrusters with the power to alter the orbits of stars around the Galactic Center, may be detectable with hypertelescopes. Some examples of technosignatures are described in Paul Davies's 2010 book The Eerie Silence, although the terms "technosignature" and "technomarker" do not appear in the book.
"Bigger Than Worlds" is an essay by the American science fiction writer Larry Niven. It was first published in March 1974 in Analog magazine, and has been anthologized in A Hole in Space (1974) and in Playgrounds of the Mind (1991). It reviews a number of proposals, not inconsistent with the known laws of physics, which have been made for habitable artificial astronomical megastructures.
Tabby's Star is an F-type main-sequence star in the constellation Cygnus approximately 1,470 light-years from Earth. A distant red dwarf companion has been reported, making Tabby's Star a binary stellar system.
A planetary civilization or global civilization is a civilization of Type I on the Kardashev scale. This type of civilization is likely to be reliant on renewable energy sources such as stellar power, as well as powerful non-renewable sources such as nuclear fusion. A Type I civilization's energy consumption level is roughly equivalent to the solar insolation on Earth (between 1016 and 1017 watts) – around 3 orders of magnitude higher than that of contemporary humanity (around 2×1013 as of 2020).
An artificial planet is a proposed stellar megastructure. Its defining characteristic is that it has sufficient mass to generate its own gravity field that is strong enough to prevent atmosphere from escaping, although the term has been sometimes used to describe other types of megastructures that have self-sufficient ecosystems. The concept can be found in many works of science-fiction.
