Alderson disk
Encyclopedia
An Alderson disk is an artificial astronomical
megastructure
, like Niven's
Ringworld
, or a 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 radius of an Alderson disk would be roughly equivalent to the orbit of Mars
or Jupiter
. According to the proposal, a sufficiently massive disk would have a larger mass
than its sun.
Close to its surface, the gravity of the disk would closely approximate that of an infinite flat plate, for which gravity is perpendicular to the surface. Near the inner and outer edges of the plate, edge effects would become significant.
The mechanical stresses
within the disc would be far beyond what any known material can stand, thus relegating such a structure to the realm of exploratory engineering
until materials and construction science become sufficiently advanced.
Life could exist on either side of the disk, though close to the sun the heat would make life impossible without protection. Conversely, further away from the sun living beings would freeze. Therefore, for the entirety of such a structure to be made habitable, it would have to include a vast number of life support systems.
Because the sun remains stationary, there is no day/night cycle, only a perpetual twilight
. This could be solved by forcing the sun to bob up and down within the disk, lighting first one side then the other.
) was a prominent feature of Malibu Comics
' Ultraverse. The Godwheel was split between two societies, one which used technology
and one which used magic
(each occupied separate sides of the disk). Author Larry Niven
designed the Godwheel and wrote stories surrounding certain events on it.
A disk-shaped planet similar to an Alderson disk (though far smaller) served as the home world of the fantasy "Aysle" setting (or "cosm") of West End Games
' Torg
roleplaying game. In contrast with the Alderson disk, the Aysle "diskworld" works according to fantasy physics, including a "gravity plane" that bisects the disk laterally, so that opposite sides "fall" towards the plane. The diskworld of Aysle had a bobbing sun and multiple inner layers. Both sides of the disk were inhabited, as were the internal layers.
The Alderson disk is discussed in Larry Niven's "Bigger than Worlds" essay, 1974, which can be found in his Playgrounds of the Mind
anthology
.
In Charles Stross's Missile Gap
, a copy of the whole Earth is placed on an Alderson disk built around a black hole by ASB
s.
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
megastructure
Megastructure
A megastructure is a very large manmade object, though the limits of precisely how large this is vary considerably. Some apply the term to any especially large or tall building....
, like Niven's
Larry Niven
Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...
Ringworld
Ringworld
Ringworld is a Hugo, Nebula, and Locus award-winning 1970 science fiction novel by Larry Niven, set in his Known Space universe and considered a classic of science fiction literature. It is followed by three sequels, and preceded by four prequels, and ties into numerous other books set in Known Space...
, or a Dyson sphere
Dyson sphere
A Dyson sphere is a hypothetical megastructure originally described by Freeman Dyson. Such a "sphere" would be a system of orbiting solar power satellites meant to completely encompass a star and capture most or all of its energy output...
. The disk is a giant platter with a thickness of several thousand miles. The sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
rests in the hole at the center of the disk. The outer radius of an Alderson disk would be roughly equivalent to the orbit of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
or Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
. According to the proposal, a sufficiently massive disk would have a larger mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
than its sun.
Close to its surface, the gravity of the disk would closely approximate that of an infinite flat plate, for which gravity is perpendicular to the surface. Near the inner and outer edges of the plate, edge effects would become significant.
The mechanical stresses
Stress (physics)
In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
within the disc would be far beyond what any known material can stand, thus relegating such a structure to the realm of exploratory engineering
Exploratory engineering
Exploratory engineering is a term coined by K. Eric Drexler to describe the process of designing and analyzing detailed hypothetical models of systems that are not feasible with current technologies or methods, but do seem to be clearly within the bounds of what science considers to be possible...
until materials and construction science become sufficiently advanced.
Life could exist on either side of the disk, though close to the sun the heat would make life impossible without protection. Conversely, further away from the sun living beings would freeze. Therefore, for the entirety of such a structure to be made habitable, it would have to include a vast number of life support systems.
Because the sun remains stationary, there is no day/night cycle, only a perpetual twilight
Twilight
Twilight is the time between dawn and sunrise or between sunset and dusk, during which sunlight scattering in the upper atmosphere illuminates the lower atmosphere, and the surface of the earth is neither completely lit nor completely dark. The sun itself is not directly visible because it is below...
. This could be solved by forcing the sun to bob up and down within the disk, lighting first one side then the other.
In popular culture
An Alderson disk (the GodwheelGodwheel
The Godwheel is one of the main concepts of the Malibu Comics Ultraverse. While it lent its name to a 1994/1995 four-issue series, the Godwheel is actually the place of origin of quite a few Ultraverse concepts, characters and significant items that predate that series...
) was a prominent feature of Malibu Comics
Malibu Comics
Malibu Comics was an American comic book publisher active in the late 1980s and early 1990s, best known for its Ultraverse line of superhero titles. The company's headquarters was in Calabasas, California. Malibu imprints included Aircel Comics and Eternity Comics...
' Ultraverse. The Godwheel was split between two societies, one which used technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...
and one which used magic
Magic (paranormal)
Magic is the claimed art of manipulating aspects of reality either by supernatural means or through knowledge of occult laws unknown to science. It is in contrast to science, in that science does not accept anything not subject to either direct or indirect observation, and subject to logical...
(each occupied separate sides of the disk). Author Larry Niven
Larry Niven
Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...
designed the Godwheel and wrote stories surrounding certain events on it.
A disk-shaped planet similar to an Alderson disk (though far smaller) served as the home world of the fantasy "Aysle" setting (or "cosm") of West End Games
West End Games
West End Games was a company that made board, role-playing, and war games. It was founded by Daniel Scott Palter in 1974 in New York, but later moved to Honesdale, Pennsylvania...
' Torg
Torg
Torg is a cinematic multi-genre role-playing game created by Greg Gorden and Bill Slavicsek and released by West End Games in 1990, which uses several innovative techniques...
roleplaying game. In contrast with the Alderson disk, the Aysle "diskworld" works according to fantasy physics, including a "gravity plane" that bisects the disk laterally, so that opposite sides "fall" towards the plane. The diskworld of Aysle had a bobbing sun and multiple inner layers. Both sides of the disk were inhabited, as were the internal layers.
The Alderson disk is discussed in Larry Niven's "Bigger than Worlds" essay, 1974, which can be found in his Playgrounds of the Mind
Playgrounds of the Mind
Playgrounds of the Mind is a collection of short stories by Larry Niven, published in 1991. It is the sequel to N-Space.Many of the stories are set in Niven's Known Space universe...
anthology
Anthology
An anthology is a collection of literary works chosen by the compiler. It may be a collection of poems, short stories, plays, songs, or excerpts...
.
In Charles Stross's Missile Gap
Missile Gap
"Missile Gap" is a 2006 English language science fiction novella, originally published in the anthology One Million A.D. by British author Charles Stross. It won the Locus Award for best novella of 2006...
, a copy of the whole Earth is placed on an Alderson disk built around a black hole by ASB
Alien space bats
Alien space bats is a neologism for plot devices used in alternate history to create a point of divergence that would otherwise be implausible.-Definition:...
s.