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A 'megastructure', in science fiction and speculative (or exploratory) engineering, is an enormous self-supporting artificial construct. The definition is often informal and varies from source to source, but generally requires at least one dimension to be in the hundreds of kilometers. Other criteria such as rigidity or contiguousness are sometimes also applied, so large clusters of associated smaller structures may or may not qualify. The products of megascale engineering or astroengineering are megastructures.
Megastructures are also an architectural concept popularized in the 1960s where a city could be encased in a single building, or a relatively small number of buildings interconnected together.
Megastructures often play a part in the plot or setting of science fiction movies and books.
Existing megastructures
The Great Wall of China is an example of a megastructure. This picture was taken near Beijing in winter.
There are structures on Earth that may be considered megastructures, such as
★ The Great Wall of China is a human-built megastructure, a few meters wide and 3,947 mi (6,352 km) in length, about 4, 975,318 square yards (4,160,000 m²)
★ The Rice Terraces of the Philippine Cordilleras, a 10,360 square kilometer (4,000 square mile) sprawling agricultural landscape carved in the mountains by free tribesmen of Ifugao some 6,000 to 2,000 years ago.
Networks of roads or railways, and collections of buildings (cities and associated suburbs), are usually not considered megastructures, despite frequently qualifying based on size. However, an ecumenopolis might qualify.
Proposed megastructures
★ Atlantropa, a hydroelectric dam to be built across the Strait of Gibraltar, and the lowering of the surface of the Mediterranean Sea by as much as 200 metres.
Theoretical megastructures
Stellar scale
A cut-away diagram of an idealized Dyson shell—a variant on Dyson's original concept—1 AU in radius.
Most stellar scale Megastructure proposals are designs that make use of the energy from a sun-like star while possibly still providing gravity or other attributes that would make it attractive for an advanced civilization.
★ The Alderson disk is a theoretical structure in the shape of a disk, where the outer radius is equivalent to the orbit of Mars or Jupiter and the thickness is several thousand miles. A civilization could live on either side, held by the gravity of the disk and still receive sunlight from a star bobbing up and down in the middle of the disk.
★ A Dyson sphere (also known as a Dyson Shell) refers to a structure or mass of orbiting objects that completely surrounds a star to make full use of its solar energy.
★ The Niven ring is an artificial ring with a diameter roughly equal to the radius of the Earth's orbit. A star is present in the center and the ring spins to provide artificial gravity.
★ An Orbital is a space habitat similar to but much smaller than a Niven Ring. Instead of being centered around a star, it is orbiting a star, thus its diameter is typically in the Order of magnitude of a star. By giving a tilt to its orbit, there's a convenient day and night experience on its surface.
★ A Matrioshka brain is a collection of multiple Concentric Dyson Spheres which make use of different wavelengths of light.
★ A Stellar engine either uses the temperature difference between a star and interstellar space to extract energy or serves as a Shkadov thruster.
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★ A Shkadov thruster accelerates an entire star through space by selectively reflecting or absorbing light on one side of it.
★ Topopolis (also known as Cosmic Spaghetti) is a large tube that rotates to provide artificial gravity.
Planetary scale
★ Globus Cassus is a hypothetical proposed project for the transformation of Planet Earth into a much bigger, hollow, artificial world with the ecosphere on its inner surface. This model serves as a tool to understand the World's real functioning processes.
Orbital structures
★ The Bernal sphere is a proposal for a space colony with a maximum diameter of 16 kilometers.
★ The Stanford torus is a different design with a diameter just under 1.7 kilometers.
★ The O'Neill cylinder is yet another space colony proposal.
Trans-orbital structures
One concept for the space elevator has it tethered to a mobile seagoing platform.
★ A Skyhook is a tall structure that is held standing by something other than the materials connecting it to the ground.
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★ A Space fountain is held up by the momentum of a working fluid which is shot up to the top at high speeds.
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★ A Space elevator is held up by the angular acceleration of the top part of the structure which lies above a Geosynchronous orbit.
★ Rotovator proposals call for a large tether to transfer momentum between spacecraft in transit.
Fictional megastructures
Stellar scale
★ The Dyson shell (including its variation, the Ringworld) has appeared in many works of fiction, including the ''Star Trek'' universe.
★ Larry Niven's series of novels about his ''Ringworld'' centered around, and originated the concept of the Ringworld, or Niven ring.
★ In the manga ''Blame!'' the Megastructure is a vast and chaotic complex of metal, concrete, stone, etc, that covers the whole Earth and assimilates even the Moon. There is even a clue by the end of this manga that suggests the assimilation of Jupiter. The Megastructure continues to expand by itself, being built by robots called builders. The whole history of the manga takes place deep inside of the structure, where there is no sea or sky, and the characters find themselves climbing up thousand of kilometers of labyrinths searching for Net Terminal Genes. It has been suggested by Tsutomu Nihei himself that the Megastructure is actually a growing dyson sphere of gargantuan proportions.(Speculated to be roughly the size of Jupiter's planetary orbit.)
★ In ''White Light'' by William Barton and Michael Capobianco, a Topopolis is presented as taking over the entire universe.
★ In the Heechee books by Frederik Pohl the race of pure energy beings called The Foe have constructed the Kugelblitz, a black hole made of energy and not matter.
★ In the Xeelee series of books by Stephen Baxter, the eponymous alien race constructed the Ring, a megastructure made of cosmic string, spanning over 10 million light - years.
Planetary scale
★ Death Star of ''Star Wars'' fame
★ Borg Transwarp Hub and Unicomplexes
★ Buster Machine III from ''Gunbuster''.
★ Culture Orbital
★ Trantor, the capital of an interstellar empire in Isaac Asimov's Foundation series, is a planet entirely covered in one huge metal clad building, with only one small green space: the Emperor's palace grounds
★ The Ori Supergate seen in a number of episodes of ''Stargate SG1'' could be classed as a megastructure
★ In ''The Hitchhiker's Guide to the Galaxy'' series, Earth, as well as other planets, were artificial megastructures. Earth was intended to function as a gigantic computer, and was built by a race of beings who made their living by manufacturing other planets.
★ The Star Forge from Knights of the Old Republic
★ Despite being sentient, the Transformers universes Unicron's 'metal planet' form is comparable to a megastructure.
★ The seven Halos from the '' universe are 10,000 km wide rings.
★ In the Robotech Sentinels novels, Haydon IV is an artificially constructed cyber-planet with android citizens.
★ In the Invader Zim episode "Planet Jackers", two aliens surround the Earth with a fake sky in order to throw it into their sun.
★ Nightmare's fortress from can be classified as a megastructure because of the fact that it's the size of a small planet.
★ In several works, Arthur C. Clarke writes about a colossal hollow tube, first described in "Rendezvous with Rama" (1973), and inhabited by different races.
Megascale structures
Structures that might not be classified as "''Megastructures''" because they do not meet the requirements, but are indeed "''Mega''" sized structures/constructions.
Stellar scale
★ Dyson Bubble - Collection of separate constructions.
★ Dyson Swarm - Collection of separate constructions.
See also
★ Supertall
★ Arcology
★ Megaproject
External links
★ Megastructures in science fiction index by Ross Smith.
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