Dyson sphere

Dyson sphere is a hypothetical megastructure originally described by Freeman Dyson.Created by [[The Sidairean]] [Elder Races]],as SuperSantuary Worlds,{{Distant Outposts,Embassey Worlds,Temporal Transit Spaceports and such.

==Maveric Uninerse==

The Amazing Dysonsphere World of Terra-Prime was created as one of the last,great dyson sphere projects-apart of the Great Network of Temporal Transit Civilations,to complete a network of Temporal Jump Point Clusters,similar to Atlantis-Prime,Asguard-Prime,[[Olympus-Prime],Atlas-Prime,Asitland-Prime,Attiland-Prime.,[[Titanus-Prime]],Atlas-Prime,Promeathia-Prime,[1]Atlas-Prime,[[Hades-Prime]],[[Atlas-Prime]] Genisis-Prime,Titanus-Prime,Sidairia-Prime It was the hope of the ancient,elder civilizations to give to the many infinateTerran civilizations,a similar world as this.

Dyson Sphere

DIAMETER: 200,000,000km

BUILDER/COMMENTS: "The Dyson Sphere was constructed over a million years ago by an unknown race, and abandoned several thousand years ago, presumably due to instability in the central star. The carbon-neutronium shell is approximately 2500 metres thick, and is presumed to contain circulation equipment for the Class-M environmental systems as well as artificial gravity and power generators, but this is an as-yet untested hypothesis, since only limited access has been gained and sensors are unable to penetrate the material. The upper atmosphere polarises to provide an artificial day/night cycle of 15.4 hours of light and 10.2 hours of darkness." From here.

SOURCE: "the The Dyson sphere (or Dyson shell) was originally proposed in 1959 by the astronomer Freeman Dyson as a way for an advanced civilization to utilise all of the energy radiated by their sun. It is an artificial sphere the size of an 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 will hit a receiving surface where it can be used. This would create a huge living space and gather enormous amounts of energy." see here for more information.

Written by Jonathan O’Callaghan

First proposed by theoretical physicist Freeman Dyson in 1960, a Dyson sphere is a hypothetical swarm of satellites that would surround a star in order to harness its energy. It is something that is well and truly only in the remit of being possible for a civilisation far more advanced than our own, but nevertheless it is something that has garnered significant interest since it was first theorised.

== Dyson swarm

==

This particular idea is more commonly known as a Dyson swarm. Some people, however, have discussed the possibility of rather than a swarm of satellites a star could be encased in a solid sphere by a future civilisation, but this is an idea that Dyson himself is keen to stray away from. Indeed, for a planetary system like our own, such a structure would likely require every object in the Solar System other than the Sun to be dismantled and rebuilt into a giant sphere owing to the huge size of the Sun.

Dyson’s initial proposal was suggested as a way that a future civilisation could sate their expected vast energy needs. As the energy requirements of a civilisation increases they may require an ever-growing amount of energy, a crisis perhaps solved only by harnessing the power of stars.

With it this carries further connotations, namely that perhaps there are advanced extraterrestrial races elsewhere in the universe that have built such structures. Dyson postulated that these would radiate a large amount of infrared radiation noticeable even to us here on Earth.

The idea has gained enough ground such that the SETI Institute in California, USA, has been on the lookout for Dyson spheres, while Fermilab near Chicago has carried out their own analysis of observations from outside the Solar System to ascertain the likelihood of the existence of Dyson spheres. Aside from finding four candidates that were “amusing but still ambiguous and questionable,” though, nothing too promising has been found.

While fun to imagine, the logistics of a Dyson sphere are also quite far-fetched. Taking the solid shell idea, this structure would be thin at perhaps just a few tens or hundreds of metres thick with its membrane covered in solar panels, but it would still be many times more massive than Earth. Placed around a star, though, it would have little chance of keeping its structural integrity; if made to rotate so as to keep it in “orbit” around the star, the areas around its artificial equator would be stable but at the poles, where there was no rotation, the structure would succumb to the forces of gravity and collapse.

This is why Dyson himself favours the swarm idea. With this, many thousands of solar energy-gathering satellites would be placed around the star. They could perhaps be tethered together, and they would then beam their energy to a central hub to be utilised by a civilisation. Using separate satellites, all in orbit around the star, the structure would remain intact and huge amounts of energy could be transferred from the star.

While this particular structure might seem impractical, something on a smaller scale could feasibly do a similar job. For example, some theories suggest that a large solar-gathering spacecraft placed between Earth and the Moon would be able to absorb huge amounts of power that could be beamed to our planet. Known as space-based solar power (SBSP), this is something that science fiction writers have favoured and is a much more promising technology than an entire Dyson sphere. However, perhaps many thousands of year in the future when we become interstellar explorers, it may be necessary to find huge resources of energy and, as far as we know, there’s nothing better than an entire star.

Rhandarian Sargasso Vines bawled into planet shape

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. Dyson speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization, and proposed that searching for evidence of the existence of such structures might lead to the detection of advanced intelligent extraterrestrial life. Different types of Dyson spheres correlate with information on the Kardashev scale. Since then, other variant designs involving building an artificial structure or series of structures to encompass a star have been proposed in exploratory engineering or described in science fiction under the name "Dyson sphere". These later proposals have not been limited to solar-power stations. Many involve habitation or industrial elements. Most fictional depictions describe a solid shell of matter enclosing a star, which is considered the least plausible variant of the idea (see below). In May 2013, at the Starship Century Symposium in San Diego, Freeman Dyson repeated his comments that he wished the concept had not been named after him.

Name: Dyson Sphere or Dyson Swarm

Named for: Princeton physicist Freeman Dyson, who proposed the megastructure concept in a 1960 Science paper, "Search for Artificial Stellar Sources of Infrared Radiation"

Selected Science Fiction Portrayals: Across a Billion Years, a 1969 novel by Robert Silverberg; the Star Trek: The Next Generation episode "Relics," which first aired in 1992; and the 1995 novel The Time Ships by Stephen Baxter.

Humankind is energy hungry. As our civilization has industrialized over the last couple centuries, global energy consumption has spiked more than twentyfold with no end in sight. When demand outstrips what we can reap from Earth and its vicinity, what will our power-craving descendants do?

A bold solution: the Dyson Sphere. This megastructure—usually conceived of as a gigantic shell enclosing the sun, lined with mirrors or solar panels—is designed to collect every iota of a star’s energetic output. In the case of our sun, that colossal figure is 400 septillion watts per second, which is on the order of a trillion times our current worldwide energy usage. What’s more, the interior of the Dyson Sphere could, in theory, provide far more habitable real estate than a measly planet.

Physicist Freeman Dyson speculated that a technologically advanced race, reaching the limit of its civilization’s expansion because of dwindling matter and energy supplies, would seek to exploit their sun for all it is worth.

"One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star," Dyson wrote in the 1960 Science paper that led to his becoming the namesake of this megastructure.

The U.S.S. Enterprise encounters a Dyson Sphere in Star Trek: The Next Generation. (Photo Credit: Paramount)

A Dubious Sphere

From an engineering perspective, a Dyson Sphere sounds pretty wild. And it is: As an immense, hollow ball, the structure is impossible. "An actual sphere around the sun is completely impractical," says "Stuart Armstrong, a research fellow at Oxford University’s Future of Humanity Institute who has studied megastructure concepts.

Armstrong says the tensile strength needed to prevent the Sphere from tearing itself apart vastly exceeds that of any known material. Another problem: The Sphere would not gravitationally bind to its star in a stable fashion. This is perhaps counterintuitive; you might think that a perfect sphere around a star would be stable. But if any part of the sphere were nudged closer to the star—say, by a meteor strike—then that part would be pulled preferentially toward the star, creating instability.

That’s too bad. If it could be stabilized, a Dyson Sphere built at 93 million miles from the sun, the same distance as the Earth, would contain about 600 million times the surface area of our planet in its interior. However, comparatively little of the surface would be habitable on account of a lack of gravity. By spinning the whole sphere, you create gravity in the form of centrifugal force along an equatorial band. But this rotation would wrack the megastructure with yet more destructive stress.

The interior of a Dyson Sphere as envisioned on Star Trek: The Next Generation>em>. The portal to the left allowed the passage of the U.S.S. Enterprise into the Sphere. (Photo Credit: Paramount) If the Dyson Sphere were possible, its residents would be treated to an awesome vista. The "sides" of the inner Sphere would seem to contain the observer within a bowl-like tunnel, with the sun, constantly overhead, appearing as a light at the tunnel’s "end."This would be much the hollow earth of Edgar Rice Burrouths's Pellucidar,but with was scientific problem. Astonishingly, along those sides, an object the size of the Earth would look miniscule. According to a Dyson Sphere FAQ posted by Armstrong’s Oxford colleague, Anders Sandberg, Earth would be about the size of a pea glimpsed at a distance of 100 meters (or, to Americanize the reference, from one football end zone to the other.)

If oceans, continents, and clouds were to be individually visible along the habitable band stretching upward from either horizon, they’d have to be monstrous.

Flocking Mirrors

Okay, so the fanciful Dyson Sphere appears to defy the laws of physics. A related concept—the Dyson Swarm—is more promising. "The Swarm is the more realistic model," Armstrong says.

A Dyson Swarm consists of thousands of relatively small mirrors or solar panels in an array of orbits around the sun. Like a dense cloud of bees buzzing around a hive, a Dyson Swarm largely shrouds the sun from external view, capturing most of the available solar energy.

A Dyson Swarm, made of thousands of individual units. (Photo Credit: Steve Bowers/Orion’s Arm Project)

Armstrong says that a robot-driven manufacturing process could build up a Dyson Swarm in as little as several decades. His plan relies on exponential returns from a virtuous cycle beginning with robots mining material from Mercury. The material is rocketed into orbit (not too tough, given Mercury’s weak gravity), then fabricated into an energy-collecting Dyson Swarm unit. The first unit would take a decade to make, be less than a half-square-mile in area, and have "the thickness of tin foil," Armstrong said. This unit would then power an uptick in mining and collector building, and so on. Three more similar cycles would commence, each grander in scale than the last. "It all depends on exponential feedback," Armstrong says.

Transmogrified Planets

About half of Mercury’s mass—2 sextillion pounds or so—would be usable in the form of the elements oxygen and iron, Armstrong reckons. These elements could be combined to form an iron oxide called hematite, which we humans have used to make mirrors since antiquity. The mirrors could reflect sunlight to power a generator akin to a solar thermal energy plant but adapted for operation in space.

After 40 years of getting worked over, Mercury would be kaput. The small planet would have been converted into a horde of mining and manufacturing robots, powered by fleets of Dyson Swarm solar collectors. Making a full Dyson Swarm that would catch nearly all of the sun’s rays, though, would require dismantling perhaps the entire inner solar system—Mercury, Venus, Earth, and Mars. But once engineers have reached this advanced stage, Armstrong says, this prospect wouldn’t seem so daunting. Strip-mining Venus would take merely a year given all the available energy and robotics following Mercury’s demise.

In devising this Dyson Swarm game plan, Armstrong assumed—conservatively, he thinks—only a one-tenth efficiency for rocketing material off Mercury. The other 90 percent of available energy would go toward mining and processing ore. He assumed further that the mirror and associated generator would reap just a third of the available solar energy, less than some of today’s solar concentrator efficiencies.

Living in the Dyson Swarm Era

If we’re going to destroy the Earth to build the swarm, then obviously we’ll need some habitat units amidst the Swarm. These could come in the form of large, rotating space colonies, like O’Neill Cylinders, placed at a nice, temperate, average Earth–Sun distances, and in safe zones where Swarm solar collecting units would not swoop through. The habitats could be configured to receive energy via lasers from the vast Swarm network.

Then again, creating Earthlike oases amidst the Swarm as replacements for our departed planet might not be the true motivation of a Dyson Swarm society. A commonly suggested reason why humankind might one day desire all the Sun’s radiated energy is to power incredibly sophisticated computers. Maybe those computers would, in fact, be us—in the form of post-biological consciousness with no need for air, water, or food.

"When thinking of how future people may view [building a megastructure], we tend to get caught up with specific images of various habitats, with natural grass and other things," Armstrong says. "But our values may have shifted . . . we might be living in machines ourselves."

 

Origin of concept

Template:See alsoThe concept of the Dyson sphere was the result of a thought experiment by physicist and mathematician Freeman Dyson, when he theorized that all technological civilizations constantly increased their demand for energy. He reasoned that if our civilization expanded energy demands long enough, there would come a time when it demanded the total energy output of the Sun. He proposed a system of orbiting structures (which he referred to initially as a shell) designed to intercept and collect all energy produced by the Sun. Dyson's proposal did not detail how such a system would be constructed, but focused only on issues of energy collection.

son Sphere FAQ

by Anders Sandberg with ideas and additions from: Richard Treitel <treitel@wco.com> Stefan E. Jones <stefanj@io.com> Dani Eder < ederd@bcstec.ca.boeing.com> Cheradenine Zakalwe <zakalwe@vision25.demon.co.uk> Steve Linton <sal@caolila.dcs.st-and.ac.uk> David Lorenzo Duffy <dlduffy@welchlink.welch.jhu.edu> Erik Max Francis <max@alcyone.com> Frank Palmer <flpalmer@ripco.com> 'ric <btgsch@rmplc.co.uk> Christopher P. Winter <cpwinter@ix.netcom.com> Steve Willner <willner@cfa183.harvard.edu> Index

What is a Dyson Sphere? Who is Dyson? Was Dyson First? Why build a Dyson sphere? What would a Dyson Sphere look like from the outside? What would a Dyson Sphere look like from the inside? Is a Dyson sphere stable? How strong must a rigid Dyson sphere be? What about gravity on a rigid Dyson shell? Would the solar wind be a problem? Can a Dyson sphere be built using realistic technology? Is there enough matter in the solar system to build a Dyson shell? Wouldn't a Dyson sphere heat up? Other Dyson Sphere-Like Concepts Have any Dyson spheres been observed? Web Resources What has been written about dyson Spheres?

What is a Dyson Sphere?

The Dyson sphere (or Dyson shell) was originally proposed in 1959 by the astronomer Freeman Dyson in "Search for Artificial Stellar Sources of Infrared Radiation" in Science as a way for an advanced civilisation to utilise all of the energy radiated by their sun. It is an artificial sphere the size of an 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 will 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 2.72e17 km^2, around 600 million times the surface area of the Earth. The sun has a energy output of around 4e26 W, 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 kilometres thick and containing more than 1e5 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. The earliest appearance of this version seems to be Robert Silverberg's novel Across a Billion Years.

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 (see below, in the section about stability). Essentially it is a "dyson bubble", where reflecting sails reflect light onto collectors for use in external habitats. Its mass would be very smalll, 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.

Who is Freeman Dyson?

Freeman Dyson was born in 1923 in Crowthorne, Berkshire, England. Dyson received his bachelor of arts degree in mathematics from the University of Cambridge in 1945. He completed fellowships at Cambridge's Trinity College from 1946 to 1947, at Cornell University in 1947 and at the University of Birmingham from 1949 to 1951. He returned to Cornell to become a professor of physics in 1951, leaving in 1953 to join the Institute for Advanced Study, where he is now professor emeritus. Dyson is a fellow of the Royal Society, a member of the U.S. National Academy of Sciences, a corresponding member of the Bavarian Academy of Sciences, a honorary fellow of Trinity College and an Associé Etranger de l'Académie des Sciences. He is president of the the SSI (Space Studies Institute).

Among his numerous awards and honors, Dyson received the Oersted Medal from the American Association of Physics Teachers, the Phi Beta Kappa Award in Science for Infinite in All Directions, the National Books Critics Circle Award for nonfiction, the 1981 Wolf Prize in physics, the Lewis Thomas Prize and many other honors.

Books by Dyson:

Disturbing the Universe (1979) Weapons and Hope (1984) Infinite in all Directions (1988) Origins of Life (1986) From Eros to Gaia (1992) Selected Papers of Freeman Dyson (1996) Imagined Worlds (1997) Major papers on the net: Time Without End: Physics and Biology in an Open Universe Was Dyson First?

No, he admitted himself that his original inspiration came from The Star Maker by Olaf Stapledon, written in 1937. As the aeons advanced, hundreds of thousands of worldlets were constructed, all of this type, but gradually increasing in size and complexity. Many a star without natural planets came to be surrounded by concentric rings of artificial worlds. In some cases the inner rings contained scores, the outer rings thousands of globes adapted to life at some particular distance from the sun. Great diversity, both physical and mental, would distinguish worlds even of the same ring. Stapledon, in turn, may have got the idea from J. D. Bernal, who also influenced Dyson directly. Bernal describes in The World, the Flesh, and the Devil spherical space colonies: Imagine a spherical shell ten miles or so in diameter, made of the lightest materials and mostly hollow; for this purpose the new molecular materials would be admirably suited. Owing to the absence of gravitation its construction would not be an engineering feat of any magnitude. The source of the material out of which this would be made would only be in small part drawn from the earth; for the great bulk of the structure would be made out of the substance of one or more smaller asteroids, rings of Saturn or other planetary detritus. The initial stages of construction are the most difficult to imagine. They will probably consist of attaching an asteroid of some hundred yards or so diameter to a space vessel, hollowing it out and using the removed material to build the first protective shell. Afterwards the shell could be re-worked, bit by bit, using elaborated and more suitable substances and at the same time increasing its size by diminishing its thickness. The globe would fulfil all the functions by which our earth manages to support life. In default of a gravitational field it has, perforce, to keep its atmosphere and the greater portion of its life inside; but as all its nourishment comes in the form of energy through its outer surface it would be forced to resemble on the whole an enormously complicated single-celled plant. - - -

A star is essentially an immense reservoir of energy which is being dissipated as rapidly as its bulk will allow. It may be that, in the future, man will have no use for energy and be indifferent to stars except as spectacles, but if (and this seems more probable) energy is still needed, the stars cannot be allowed to continue to in their old way, but will be turned into efficient heat engines. The second law of thermodynamics, as Jeans delights in pointing out to us, will ultimately bring this universe to an inglorious close, may perhaps always remain the final factor. But by intelligent organization the life of the universe could probably be prolonged to many millions of millions of times what it would be without organization. Besides, we are still too close to the birth of the universe to be certain about its death.

According to Stefan E. Jones <stefanj@io.com>;, Raymond Z. Gallun, an american SF author may have come up with a similar concept independently. Why build a Dyson sphere?

Energy and space. As described above, the amount of collected energy would be immense, and the living space simply unimaginable. Dyson pointed out that so far the energy usage of mankind has increased exponentially for at least a couple of thousand years, and if this continues we will soon consume more energy than the Earth receives from the sun, so the natural step is to build artificial habitats around the sun so that all energy can be used. The same goes for population in the long run (it should be noted that this is not a solution, just a logical result of growth). It is also possible that the Dyson sphere simply stores the energy for future use, for example in the form of antimatter. Even if cheap and efficient fusion power can be developed, eventually the waste heat has to be radiated away by a Dyson sphere-like cooling system.

Other proposed uses have been for security (although it is hard to hide the infrared emissions; energy could be radiated away in certain directions, but thermodynamics places some limits on it), or just for the fun of it (if you have a sufficiently advanced technology megaengineering could become a hobby activity; after all, ordinary people today perform engineering or crafting feats far beyond the imagination of previous eras).

What would a Dyson Sphere look like from the outside?

A Type I Dyson sphere would probably not cover the star perfectly, so occasional glimpses of its surface would be seen as the habitats orbited. A type II Dyson sphere would be totally opaque (unless it had openings). The spheres would hence be invisible from a distance, just a black disk on the sky. But they would shine powerfully in the infrared, as the waste heat from the internal processes radiate away. The apparent temperature would be T = (E / (4 pi r^2 eta sigma))^1/4 where E is the energy output of the sun, r the radius of the sphere, eta the emissivity and sigma the constant of Stefan-Boltzman's law. This would correspond to an infrared wavelength of lambda = 2.8978e-3 / T m (assuming a blackbody sphere) which for reasonable sizes lies in the infrared. Dyson predicted the peak of the radiation at ten micrometers.

What would a Dyson Sphere look like from the inside?

The curvature of the "ground" would be even less than on Earth, so to an observer close to it it would look perfectly flat. In a solid dyson sphere with atmosphere, the atmosphere would limit the range of sight due to its opacity, and the horizon would be slightly misty. The sky would be filled with the surface of the sphere, giving the impression of a huge bowl over a flat earth, covered with clouds, continents and oceans although for a real Dyson shell these would have to be immense to be noticeable. The angular size of an object at a distance d and diameter l is 2arctan(l/2d). For an object of diameter 10,000 km (like the Earth) at a distance of a 100 million km (around 120 degrees away from the observer on the shell), the angular size would be around 10^-4 rad or 0.005 degrees, roughly the size of a pea 100 meters away.

It should be noted (as Richard Treitel has pointed out) that even a very dark surface will shine intensely, making the sky much brighter than on Earth. The albedo of Earth is around 0.37, so an interior with an earthlike environment would have a sky where each patch reflects a noticeable fraction of the sunlight.

In a type I dyson sphere roughly the same things would be seen: a plane wall of orbital habitats, solar collectors and whatnot stretching away into what looks like infinity (although here the curvature may become noticeable for observant viewers) and a hemispherical bowl covering the rest of the sky, centered around the sun. Solar collectors would have a very low albedo, but it is still likely that the interior will be very bright.

Is a Dyson sphere stable?

In a type I Dyson Sphere all the structures orbit independently around the star, and their orbits are normal keplerian elliptic or circular orbits. Since the mass of the shell is negligible compared to the sun, the self-gravity can be ignored (it will merely cause some precession of elliptical orbits). And if two orbits intersect, they can be adjusted by using solar sails, ion engines, magsails or similar low-energy devices. Another version would be based on statites (this is probably due to Robert L. Forward): each solar collector will also be a solar sail, and hover without orbiting above the sun, held up by light pressure. By adjusting the sail area statites can move in and out, and by adjusting their angle they can move away if needed. Traffic control may be a problem, but can likely be handled in various ways, for example by local flight control centres or automatic systems based on flocking behaviour.

The force on a statite would be F = L/(4 pi c r^2) - GMm/r^2, where L is the total luminosity of the sun (3.9e26 W), M is the mass of the sun, m is the density of the statite, r the distance to the sun and c is the speed of light. To remain in balance, the statite will have to have the density

m=E/(4 pi c G M) (this assumes a 100% reflective statite). Note that this is independent of distance to the sun, closer to the sun the gravitational pull is greater, but the radiation pressure is stronger. The density depends only on the mass/luminosity of the sun. For a statite in the solar system, the density would be around 0.78 g/m^2 A rigid dyson sphere is not stable, since there is no net attraction between a spherical shell and a point mass inside. If the shell is pushed slightly, for example by a meteor hit, the shell will gradually drift off and eventually hit the star. This is a classic problem in elementary mechanics and is usually solved in introductory textbooks.

Gauss Law

One easy way to derive it is from Gauss Law: the integral of the force across an arbitrary closed surface is proportional to the amount of mass inside it. If the surface is a sphere surrounding the dyson sphere, there is obviously an inward force on the surface of the sphere since there is a mass inside it. But if the sphere is inside the dyson sphere (the sun is ignored in this calculation, as we are only interested in the gravity of the dyson sphere), there is no mass inside it and hence the integral must be zero, which means that there is no gravitational field inside the sphere. Elementary Proof

It can also be proven using only elementary (brute force) calculus. This treatment is from Kleppner & Kolenkow, An Introduction to Mechanics (p. 101) and deals with the force between a point of mass m at radius r on the x-axis from a spherical shell centred at the origin: Divide the shell into narrow rings. Let R be the radius of the shell, t its thickness (t << R). The ring at angle theta, which subtends an angle dtheta, has a circumference 2 pi R sin theta, width R dtheta an thickness t, which gives it a volume of

dV=2 pi R^2 t sin theta d theta and a mass of (M/2) sin theta dtheta where rho is the density of the shell. Each part of the ring is the same distance r´ from m, and by symmetry the force from the ring is directed along the axis with no transversal component. Since the angle alpha between the force vector and the line of centres is the same for all sections of the ring, the force components along the line of centres add to give

dF=G m rho dV cos alpha / r´^2 for the whole ring. This is then integrated: F = int (G m rho dV/r´2) cos alpha. By expressing cos alpha as a function of polar angle we get: F = [GMm/2] int_0^pi ( (r - R cos theta) sin theta dtheta)/(r^2 + R^2 - 2 r R cos theta)^2/3 (where int_0^pi is the integral from 0 to pi). Through the substitution u=r-Rcos(theta), du=Rsin theta dtheta we get: F = [GMm/2R] int_{r-R}^{r+R} (u du) / (R^2 - r^2 +2ru)^(3/2) which is a standard integral resulting in: F = (GMm/2R)(1/2r^2)[sqrt(R^2-r^2+2ru)-(r^2-R^2)/sqrt(R^2- r^2+2ru)]_{r-R}^{r+R} For r<R we get: F=(GMm/4Rr^2){(R+r)-(R-r)-(r^2-R^2)(1/(R+r)-1/(R-r))} = 0 How strong does a rigid Dyson shell need to be?

Very strong. According to Frank Palmer: Any sphere about a gravitating body can be analysed into two hemispheres joined at a seam. The contribution of a small section To the force on the seam is g(ravity)*d(ensity)*t(hickness)*A(rea)*cos(angle). The integral of A*cos(angle) is (pi)*R^2. So the total force is g*d*t*(pi)*R^2. Which is independent of distance, neatly enough.

The area resisting the force is 2*(pi)*R*t.

Thus, the pressure is g*d*R/2; this can be translated into a cylindrical tower of a given height on Earth. If that tower built of that material can stand, then the compression strain is not too great.

At 1 AU, that comes to 2*([pi]*AU/YR)^2, or -- by my calculations -- in the neighborhood of 80 to 90 THOUSAND kilometers high.

The tendncy to buckle, moreover, is another problem.

What about gravity on a rigid Dyson shell?

A nonrotating dyson shell would have just two sources of gravity: the shell itself and the star. As mentioned above, on the inside only the gravity of the star would be felt and everything would fall down into it, while on the outside there would be weak gravity (for a 1 AU sphere centred around the sun, the gravity would be 6e-3 m/s^2). The only ways to make a rigid Dyson shell habitable on the inside would be either to provide it with some sort of antigravity (which is unlikely) or to rotate it, which would make only the equatorial band habitable unless the interior was terraced. A rotating dyson sphere would be under immense strains; see the section about the ringworld for a simple calculation. Niven pointed out that if you want to spin a Dyson sphere, it is better to build it like a film canister for reasons of structural strength, and then you have a Ringworld.

It has been suggested that one could live on the outside of the sphere, especially if the interior star is rather cool; it appears that a terrestrial environment is possible around M stars just at the end of the main sequence. Erik Max Francis gives the following derivation of this kind of sphere:

First, know the luminosity-mass relation for main sequence stars:

L = k M^nu, where k is a constant of proportionality and nu is between 3.5 and 4.0. (k depends on the choice of nu, obviously.) You can find the constant k, given nu, based on the fact that the Sun has a luminosity of 3.83 x 10^26 W and a mass of 1.99 x 10^30 kg. Second, know the gravitational acceleration:

g = G M/R^2. Third, the blackbody power law (we're approximating the star as a blackbody, which isn't too bad of an approximation): L = e sigma A T^4. Knowing these factors, you can combine them to get an equation which relates the mass of the star to the desired temperature and gravity of the sphere: k M^(nu - 1) = 4 pi e sigma G T^4/g. Substituting ideal conditions (g = 9.81 m/s^2, T = 300 K), you find that M must be between 0.054 and 0.079 masses solar (the variance is dependent on the variance in the exponent in the mass-luminosity relation). The end of the main sequence is at about 0.08 masses solar, for comparison. This would produce spheres with a radius of 0.0057-0.0069 AU (852,720 - 1,032,240 km).

It might also be possible to have a biosphere between two dyson spheres (this is used in Baxter's The Time Ships).

Would the solar wind be a problem?

If an earthlike ecology was built inside a large rigid dyson shell, there would be an influx of ions (mostly hydrogen) from the solar wind. The solar wind has a density of around 5 ions/cm^3, moving at around 500 km/s; that would lead to an influx of 2.5e12 ions/m^2/s. This might appear large, but is actually a tiny amount, just 4e-12 mol (one gram of hydrogen is approximately one mol). Since the hydrogen could not naturally escape from the atmosphere it would gradually become more and more hydrogen rich, but it would take trillions of years before the effects became significant. The net force from the solar wind and the light pressure (which is larger than the solar wind pressure) is also minor compared to the attraction of the sun and the internal strains of a rotating dyson shell. In a type I dyson sphere the light pressure could be used to keep statites hanging in space. It should be noted that there would be no auroras in a dyson shell, since there is no magnetic field. This also would also mean that more radiation would reach the ground from the sun since it cannot naturally be deflected (although one could imagine megaengineering systems to provide an artificial magnetic field).

Can a Dyson sphere be built using realistic technology?

A type I Dyson sphere can be built gradually, without any supertechnology or supermaterials, just the long-term deployment of more solar collectors and habitats. This work could start today (and one might argue that our satellites are the first step). Using self-replicating machinery the asteroid belt and minor moons could be converted into habitats in a few years, while disassembly of larger planets would take 10-1000 times longer (depending on how much energy and violence was used). A rigid dyson shell would require superstrong materials, and its construction is complicated since half a shell is unstable. One could conceive of some dramatic capping process, where a number of previously freely orbiting structural components at the same time moved inwards to lock together into a shell (for example twenty spherical triangles). This would require tremendous precision, but since supertechnology is already assumed for building a rigid shell, it seems almost trivial. As somebody put it, if you can build a dyson shell you don't need it.

Is there enough matter in the solar system to build a Dyson shell?

Dyson originally calculated that there is enough matter in the solar system to create a shell at least three meters thick, but this might be an overestimate since most matter in the solar system is hydrogen and helium, which isn't usable as building materials (as far as we know today). They could presumably be fusioned into heavier elements, but if you can fusion elements on that scale, why bother with a dyson sphere? If one assumes that all elements heavier than helium are usable (a slight exaggeration), then the inner planets are completely usable, as is the asteroid belt.

Mass (1e24 kg)

Mercury: 0.33022 Venus: 4.8690 Earth: 5.8742 Moon: 0.0735 Mars: 0.64191 Asteroids: ~0.002

Sum: 11.78733e24 kg It is a bit more uncertain how much of the outer planets is usable. Jupiter and Saturn mainly consist of hydrogen and helium, with around 0.1% of other material. Jupiter is assumed to have a rock core massing around 10-15 times the Earth, and Saturn probably contains a smaller core massing around 3 times the Earth. Uranus and Neptunus seem to be mainly rock and ice, with around 15% hydrogen, so a rough estimate would be around 50-70% usable mass. Pluto seems to be around 80% usable.

               Mass (1e24 kg)       Usable Mass (rough estimate)

Jupiter: 1898.8 ~58 Saturn: 568.41 ~17 Uranus: 86.967 ~43 Neptune: 102.85 ~51 Pluto: 0.0129 ~0.01 Kuiper belt objects: ~0.02 ~0.016

Sum: 2657.06 Usable: ~170

(this is based on the assumption that the size distribution of the Kuiper belt mirrors the asteroid belt) (these tables based on information from Physics and Chemistry of the Solar System by John S. Lewis and The Nine Planets by Bill Arnett)

The inner system contains enough usable material for a dyson sphere. If one assumes a 1 AU radius, there will be around 42 kg/m^2 of the sphere. This is probably far too little to build a massive type II dyson sphere, but probably enough to build a type I dyson sphere where mass is concentrated into habitats and most of the surface is solar sails and receivers, which can presumably be made quite thin.

With the extra material from the outer system, we get around 600 kg/m^2, which is enough for a quite heavy sphere (if it was all iron, it would be around 8 centimeters thick, and if it was all diamond around 20 centimeters).

A Type III shell, a "dyson bubble", would have a very low mass. Since its density is independent of the radius (see the stability section), its mass would scale as r^2. For an 1 AU bubble, the total mass needed would be around 2.17e20 kg, around the mass of Pallas.

Wouldn't a Dyson sphere heat up?

Even if the civilisation living in the Dyson sphere did its best to store available energy, thermodynamics eventually wins and the sphere begins to radiate away energy until equilibrium is reached. Its temperature becomes T=[E/(4 pi eta sigma r^2)]^(1/4) where eta is the emissivity (=1 for a blackbody), sigma the constant of Stefan-Bolzman's law (5.67032e-8 Wm^2K^-4)and E the total energy output of the star measured in watts. In theory, if eta is very low the interior of the sphere could become as hot as desired, but this is unlikely since the material of the sphere would start to melt or evaporate if the temperature moved above 2000-3000K or so. And if the surface of the star became hot enough, the outer parts of the star would expand and a new thermal equilibrium set in with less internal energy production. If the sphere was a perfect energy container the star would eventually expand until its fusion processeses ended; if the temperature was lowered (by energy use) fusion would resume until an equilibrium was reached - a bottled star.

It should be noted that at 1 AU, the energy flux is around 1.4e3 W/m^2, which calculates as around 395 K, or 122 degrees C if the sphere is a blackbody. This is a bit too hot for an earthlike biosphere (Earth is cooled by its rotation, which effectively halves the energy flux, and its spherical shape, that lowers it further), and a dyson shell need some rather impressive cooling to work.

The radius of the smallest passively radiating shell with thermal tolerance T_max is

r_smallest = sqr(E/(4 pi eta sigma T_max^4)) Diamond can stand around 4000K; putting 4000K into the equation, we get 1.48e9 meters, or around 1.4 million kilometers. For 1000K we get a radius of 2.37e10 meters, or around 23 million kilometers. This is roughly 2 and 32 solar radii respectively. With active cooling the shell can be made much smaller. olar radii respectively. With active cooling the shell can be made much smaller. Other Dyson Sphere-Like Concepts

Ringworlds

Ringworlds were introduced by Larry Niven in Ringworld. A ringworld is essentially a band encircling a star, rotating to create gravity and covered with an ecosphere. The atmosphere is held in by gravity and 1000-kilometre mountain walls at the edges. Day and light are provided by a second ring of "shadow squares", black rectangles covering the sun during "night". Cooling systems keep the climate stable and an automated meteor defence system shoots down meteors. Just as with a type II Dyson sphere the internal stresses would require an immensely strong material (Niven uses the invented material scrith, a greyish translucent material with strength on the order of the nuclear binding strength). The stress is

F= r rho g [N/m] where rho is the weight of the ringworld per square meter (kg/m^2) and g is the surface acceleration and r is the radius. For the ringworld g was close to earthly, a radius of around 1 AU and there was at least a kilometre of surface material of approximately eartlike density. This would provide a stress on the order of 1e18-1e19 N/m. The ringworlds instability is also (in)famous. It is not neutrally stable like a dyson sphere, but dynamically unstable - a small disturbance (such as the inhomogenities in the solar wind or meteor strikes) will grow gradually, and the ringworld would gradually loose its centeredness until it runs into its sun (the ringworld is transversely stable, if the ring is perturbed along its axis it will oscillate around the equilibrium position). See Erik Max Francis' page abour ringworld stability for an easy derivation. Niven solves this problem in Ringworld Engineers by placing ramjets along the edges, forming an active stabilisation system.

A related idea to ringworlds is Ian Bank's orbitals. An orbital is a small ringworld orbiting the sun (instead of encircling it; this circumvents the instability), with a rotation period of 24 hours and earthlike gravity due to the spin. Its size would be

r=g T^2 / (4 pi^2) which gives a radius of around 2 million kilometers. If the orbital is tilted and sufficiently broad, it could shade itself to provide day and night. Note that it still requires superstrong materials, although less extreme than scrith. Bubbleworld, by Dani Eder < ederd@bcstec.ca.boeing.com>

A bubbleworld is an artificial construct that consists of a shell of living space around a sphere of hydrogen gas. It was invented to answer the question "what is the largest space colony that can be built". The answer is a non-rotating bubbleworld can be as large as 480,000 km in diameter (about 3 times the diameter of Jupiter), if you make certain assumptions. A rotating one is too hard for me to analyze. Assume that you wish to have a large living volume in the form of a shell. The shell contains air, people, houses, furniture, etc. that averages 10 kg/m^3. If you fill the interior of the shell with hydrogen (the lightest gas) at room temperature, it will assume a distribution based on self-gravity. If the pressure at the inner shell boundary, where the hydrogen and living space meet, is 1 atmosphere, then there is a largest size you can build such a structure before the self-gravity of the hydrogen starts to make it smaller.

The living space has a thickness of 2400 km if you assume that the outer surface is at a pressure equal to that at 3000 m (10,000 ft) above sea-level on Earth. Such a bubbleworld would have about 5 million times the useable living volume of the Earth. The atmosphere is held in by a cap of material (such as 500 meters of iron-nickel) so as to balance the gas pressure from below. The entire structure is in pressure equilibrium, so it requires no particular structural strength.

A rotating bubbleworld would be a flattened ellipsoid and could be several times larger, but determining the shape is more complicated than the non-rotating spherical case.

The living volume of the Bubbleworld would be in a 0.001 to 0.01 gee environment, making unusual architecture and human-powered flight possible. The entire bubbleworld would mass about 3 Earths in mass.

SupraJupiter

Paul Birch suggested that Jupiter could be enclosed in a solid shell; at a certain radius the surface gravity would be terrestial, and energy could be provided by tapping the thermal energy of the planet. Paul Birch "A Visit to SupraJupiter" Analog December 1992

Submerged Dyson Spheres

Nick Szabo proposed that since communications delays are rather long in a normal-size dyson sphere and energy densities grow as it becomes smaller, it would be advantageous to build spheres closer and closer to the star for advanced "solid state civilizations". The logical conclusion would be a shell around the core of the star, through which all energy would be filtered. The problem with this is that the amount of energy that can be extracted from the radiation depends on the difference in temperature on the two sides of the shell, and inside the star this will be rather low, while outside the star the difference will essentially be between the shell temperature and the cosmic background radiation. But it should be noted that if neutrinous can be captured, they would provide a kind of temperature differential that could be used (since the sun is almost transparent to them).

Galactic Dyson Spheres

Hara Ra <harara@shamanics.com> suggested that to maximize available energy and matter, and minimize communications delays it would be useful for very advanced civilizations or beings ("galaxy brains") to gather all the stars and other matter in the galaxy into a dense region in the core. The result would be a sphere of carefully aligned orbiting matter just larger than its Schwartzhild radius, with a black hole in the middle. Instead of relying on energy from stellar fusion, matter could be fed into the black hole, releasing energy which would be used by a surrounding "galactic dyson sphere". The total size would be on the order of a few light-months.

Using black holes for energy production can also be done using smaller dyson spheres. A very small black hole will radiate intense Hawking radiation, quickly loosing its mass. If an equal amount of mass is swallowed (for example in the form of garbage) the hole will remain stable, and convert matter into energy which can be collected by the dyson sphere.

Have any Dyson spheres been observed?

I have found the following three searches for Dyson spheres at http://www.seti-inst.edu/searches/searches-list.html:

DATE: 1980 OBSERVER(S): WITTEBORN SITE: NASA - U OF A, MT. LEMMON INSTR. SIZE (M): 1.5 SEARCH FREQ.(MHz): 8.5 microns - 13.5 microns FREQUENCY RESOL.(Hz): 1 micron OBJECTS: 20 STARS FLUX LIMITS (W/m**2): N MAGNITUDE EXCESS < 1.7 TOTAL HOURS: 50 REFERENCE: COMMENTS: Search for IR excess due to Dyson spheres around solar type stars. Target stars were chosen because too faint for spectral type.

DATE: 1984 OBSERVER(S): SLYSH SITE: SATELLITE INSTR. SIZE (M): RADIOMETER SEARCH FREQ.(MHz): 37x10**3 FREQUENCY RESOL.(Hz): 4x10**8 OBJECTS: ALL SKY 3K BB FLUX LIMITS (W/m**2): T/T =< .01 TOTAL HOURS: 6000 REFERENCE: 27 COMMENTS: Lack of fluctuations in 3K background radiation on angular scales of 10**-2 Strd. rules out optically thick Dyson spheres radiating more than 1 solar luminosity within 100 pc.

DATE: 1987 OBSERVER(S): TARTER, KARDASHEV & SLYSH SITE: VLA INSTR. SIZE (M): 26 (9 ANTENNAS) SEARCH FREQ.(MHz): 1612.231 FREQUENCY RESOL.(Hz): 6105 OBJECTS: G357.3-1.3 FLUX LIMITS (W/m**2): TOTAL HOURS: 1 REFERENCE: COMMENTS: Remote observation (by VLA staff) of IRAS source near galactic center to determine if source could be nearby Dyson sphere. Source confirmed as OH/IR star. In short, none have been observed yet. References

Slysh, V. I., Search in the Infrared to Microwave for Astro- engineering Activity, in The Search for Extraterrestrial Life: Recent Developments, M. D. Papagiannis (Editor), Reidel Pub. Co., Boston, Massachusetts, 1985 Kardashev, N. S., and Zhuravlev, V. I., SETI in Russia, paper presented at the IAA/COSPAR/IAF/NASA/AIAA symposium on SETI: A New Endeavor for Humankind, The World Space Congress, Washington, D.C., August 30, 1992. To appear in a special issue of Acta Astronautica.

Jugaku, J., and Nishimura, S., A Search for Dyson Spheres Around Late-Type Stars in the IRAS Catalog, in Bioastronomy: The Search for Extraterrestrial Life, J. Heidemann and M. J. Klein (Eds.), Lectures Notes in Physics 390, Springer-Verlag, 1991

Web Resources

An article about dyson spheres by Sarah Voigt: Dyson Spheres: A Primer A mini-FAQ, covering the basics (at SEDS): The Ultimate Biospheres Illustration of a dyson sphere: http://www.setiquest.com/dyson.htm.

Picture of F. Dyson: http://www.setiquest.com/dyson2.htm.

Computer graphics of a Ringworld: http://www.rahul.net/rootbear/graphics/ringworld/index.html

Images of dyson spheres: http://www.algonet.se/~aleph/Trans/Tech/Megascale/dyson_page.html

The Ultimate Biospheres: http://seds.lpl.arizona.edu/nodes/NODEv4n3-10.html

Transhuman Technologies, Megascale section: http://www.thehub.com.au/~mitch/extro/mega.html

Megastructures in science fiction by Ross Smith: http://www.geocities.com/SiliconValley/Park/3699/sf-megastructures.html

Outside Dyson spheres by Erik Max Francis: http://www.alcyone.com/max/writing/essays/outside-dyson.html

What has been written about dyson Spheres?

The original papers:

Dyson, F. J., Search for Artificial Stellar Sources of Infrared Radiation, Science, vol. 131, pp. 1667-1668, 1959 Dyson, F. J., The Search for Extraterrestrial Technology, in Perspectives in Modern Physics (Essays in Honor of Hans Bethe), R. E. Marshak (Editor), John Wiley & Sons, New York, 1966

Fact:

Larry Niven: "Bigger than Worlds" in A Hole In Space (1974) and Playgrounds of the Mind. Deals with all kinds of megaengineering structures. Marshall T. Savage: The Millennial Project (ISBN 0-316-77163-5). Describes a plausible space-colonization scenario, involving the construction of a type I dyson sphere.

Fiction that involves dyson spheres or linked concepts:

(sources gathered from Usenet discussions and "Megastructures in Science Fiction" by Ross Smith, http://www.algonet.se/~aleph/Trans/Tech/Megascale/megastruct.txt) Star Maker (1937) by Olaf Stapledon (An enthusiastic review)

The World is Round by Rothman

Larry Niven: Ringworld, Ringworld Engineers and Ringworld Throne

Lord Kalvan of Otherwhen by H. Beam Piper

"Relics" episode of Star Trek The New Generation (regarded as very bad by many sf lovers)

Cageworld 1: Search for the Sun, Cageworld 2: The Lost Worlds of Cronus, Cageworld 3: The Tyrant of Hades and Cageworld 4: Star-Search by Colin Kapp.

Orbitsville (1975), Orbitsville Departure (1983) and Orbitsville Judgement (1990) by Bob Shaw

Across a Billion Years by Robert Silverberg

Farthest Star (1975), Wall Around a Star (1983) by Frederik Pohl & Jack Williamson

The Time Ships by Stephen Baxter

The Wanderer by Fritz Leiber (1967?) mentions in passing that the light from most of the stars in the inhabited galaxy are dimmed by the density of habitats orbiting them. (David Lorenzo Duffy <dlduffy@welchlink.welch.jhu.edu>)

Dyson spheres need great big walls To keep the world from spilling out They make them out of buckyballs And use gravitons for grout Mister Skin < mrskin@mindspring.com>

Dyson is credited with being the first to formalize the concept of the Dyson sphere in his 1960 paper "Search for Artificial Stellar Sources of Infra-Red Radiation", published in the journal Science. However, Dyson was not the first to advance this idea.  He was inspired by the mention of the concept in the 1937 science fiction novel Star Maker, by Olaf Stapledon, and possibly by the works of J. D. Bernal, Raymond Z. Gallun, and Edgar Rice Burroughs who seem to have explored similar concepts in their work.If written today,David Innes and Abner Perry might have used an Ironmole  

Entry to the sphere is by means of ten symmetrically-spaced 3000 metre wide octagonal portals. These portals are automatically operated, triggered by any sensor or communications signal directed toward them. Massive tractor beams are then used to draw vessels inside. Due to the incompatibility of the Sphere's systems with those of Federation ships, standard procedure was until recently for a ship to shut down all systems before transmitting a signal, in order to avoid overloads. Since no access had yet been gained to the control systems, a ship could not open the portal from the inside, so a second ship or a shuttle had to trigger it from the outside at a predetermined time, standing off 500,000km to avoid being drawn in itself.

Federation personnel have since gained limited access to the Sphere's data banks, allowing them to open the Portals at will without danger.

Externally, the sphere is made up of rectangular panels metallic/ceramic composites. About two thirds of these measure 601 by 826 metres, and the remaining third measure 601 by 413 metres. The significance of the dimensions and the proprtion of large to small panels is as yet unknown. While the shell of the Dyson Sphere is composed of carbon-neutronium, the exterior panels are of more conventional materials. The basic structure of the panels is composed of a foamed tritanium/dikieferate alloy. This is covered by several thin layers of tritanium and duranium.

The purpose of many of the structures on the exterior surface is still unknown, although some are obviously a reaction-control system to keep the Sphere centred on the central star. Others, originally mistaken for communications arrays, appear to be computer interfaces. It is these which, when subjected to a standard Federation hailing frequency or sensor scan, activate the automatic process which opens the portals and tractor beams. One of these has been removed by Starfleet personnel and is being studied at the technological assessment laboratories at Starbase 21

Several large bodies of water have been spotted - indeed, approximately 50% of the surface is water, as well as wilderness areas and what appear to be large-scale industrial or urban areas. Minimal surface exploration has been conducted. Although no sapient life forms were detected by the Enterprise-D during its time inside the sphere, Dyson Base survey crews have discovered at several sapient species living on the interior surface.

Built-up "City" area surrounding a portal, Most of the Portals are surrounded by large built-up areas. These areas (dubbed "Cities" by Dyson Base personnel) are uninhabited. A few buildings have been identified as holographic data displays each devoted to a single category. Two of these have been identified by the Sphere Projector as the "Museum of Flight," depicting space vessels from many alternate realities; and the "Museum ofLife," depicting sapient life forms.

Several technological installations have been explored, including a tower with a number of habitat enclosures housing a number of different species which appear not to be native to the Sphere. One of these, a being called Gurrrps, escaped confinement and has attached himself to the crew Dyson Base. Details of the tower installation, code-named Gamma One, are classified at this time.

Feasibility

Some ideas to build a fixed-in-place 'Dyson sphere' are currently beyond humanity's engineering capacity. However, parts of the technology, like orbiting satellites and solar sails, have already been developed. Deployment of spacecraft and satellites using photovoltaics might be seen as the first small steps towards building a Dyson swarm (see below for differences between these sub-types).  However, the number of craft required to obtain, transmit, and maintain a complete Dyson sphere far exceeds level one civilizatin industrial capabilities.Many employ black rectangles of solar blocks floating in the sky representing the artificial day/night controls. Ring walls in the distance. A space port at a far end and massive mirror panels in the distance reflecting the image of the sun. It would be easy with the layered background of the worlds. Most of all it would be a nice advanced game place to discover. Higher tier worlds full of hostile xeno forms not interested in sharing the technology and landscape of their ancestors's great creation. 
Perfect for exploring, it would blow conventional space stations and bases out of the water and would be great as a group high tier project world! 

Variants

In fictional accounts, the Dyson-sphere concept is often interpreted as an artificial hollow sphere of matter around a star. This perception is based on a literal interpretation of Dyson's original short paper introducing the concept. In response to letters prompted by this paper, 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 traveling on independent orbits around the star." 

Dyson swarm

File:Dyson Ring.PNG

A Dyson ring — the simplest form of the Dyson swarm — to scale. Orbit is 1 AU in radius, collectors are 1.0Template:E km in diameter (~25× the Earth–Moon distance), spaced 3 degrees from center to center around the orbital circle.

A relatively simple arrangement of multiple Dyson rings of the type pictured above, to form a more complex Dyson swarm. Rings' orbital radii are spaced 1.5Template:E km with regard to one another, but average orbital radius is still 1 AU. Rings are rotated 15 degrees relative to one another, around a common axis of rotation.

 The variant closest to Dyson's original conception is the "Dyson swarm". It consists of a large number of independent constructs (usually solar power satellites and space habitats) orbiting in a dense formation around the star. This construction approach has advantages: components could be sized appropriately, and it can be constructed incrementally. Various forms of wireless energy transfer could be used to transfer energy between components and Earth. Disadvantages: the nature of orbital mechanics would make the arrangement of the orbits of the swarm extremely complex. The simplest such arrangement is the Dyson ring in which all such structures share the same orbit. More complex patterns with more rings would intercept more of the star's output, but would result in some constructs eclipsing others periodically when their orbits overlap. Another potential problem is the increasing loss of orbital stability when adding more elements increases the probability of orbital perturbations. As noted below, such a cloud of collectors would alter the light emitted by the star system.  However, the disruption compared to a star's overall natural emitted spectrum would most likely be too small to be noticed on Earth. 

Dyson bubble

File:Dyson Bubble.png

A Dyson bubble: an arrangement of statites around a star, in a non-orbital pattern. As long as a statite has an unobstructed line-of-sight to its star, it can hover at any point in space near its star. This relatively simple arrangement is only one of an infinite number of possible statite configurations, and is meant as a contrast for a Dyson swarm only. Statites are pictured as the same size as the collectors pictured above, and arranged at a uniform 1 AU distance from the star.

 A second type of Dyson sphere is the "Dyson bubble". It would be similar to a Dyson swarm, composed of many independent constructs (usually solar power satellites and space habitats) and likewise could be constructed incrementally. Unlike the Dyson swarm, the constructs making it up are not in orbit around the star, but would be statites—satellites suspended by use of enormous light sails using radiation pressure to counteract the star's pull of gravity. Such constructs would not be in danger of collision or of eclipsing one another; they would be totally stationary with regard to the star, and independent of one another. As the ratio of radiation pressure and the force of gravity from a star is constant regardless of the distance (provided the statite has an unobstructed line-of-sight to the surface of its star), such statites could also vary their distance from their central star. The practicality of this approach is questionable with modern material science, but cannot yet be ruled out. A statite deployed around our own sun would have to have an overall density of 0.78 grams per square meter of sail.

To illustrate the low mass of the required materials, consider that the total mass of a bubble of such material 1 AU in radius would be about 2.17Template:E kg, which is about the same mass as the asteroid Pallas. Such a material is currently beyond humanity's ability to produce. The lightest carbon-fiber light sail material currently produced has a density – without payload – of 3 g/m², or about four times as heavy as would be needed to construct a solar statite. A single sheet of graphene, the two-dimensional form of carbon, has a density of only 0.77 mg per square meter, but has not been fabricated in large sheets and has transparency of 97.7%, making such a single sheet of graphene not very effective as a solar sail. However, this could change thanks to the recent creation of ultra light carbon nanotubes meshed through molecular manufacturing techniques whose densities range from 1.3g/m² to 1.4g/m². By the time a civilization is ready to use this technology, the carbon nanotube's manufacturing might be optimised enough for them to have a density lower than the 0.7g/m² mark, and the average sail density with rigging might be kept to 0.3 g/m² (a "spin stabilized" light sail requires minimal additional mass in rigging). If such a sail could be constructed at this areal density, a space habitat the size of the L5 Society's proposed O'Neill cylinder – 500 km², with room for over 1 million inhabitants, massing 3Template:E tons – could be supported by a circular light sail 3,000 km in diameter, with a combined sail/habitat mass of 5.4Template:E kg.

For comparison, this is just slightly smaller than the diameter of Jupiter's moon Europa (although the sail is a flat disc, not a sphere), or the distance between San Francisco and Kansas City. Such a structure would, however, have a mass quite a lot less than many asteroids. While the construction of such a massive inhabitable statite would be a gigantic undertaking, and the required material science behind it is as yet uncertain, its technical challenges are negligible compared to other engineering feats and required materials proposed in other Dyson sphere variants. In theory, if enough statites were created and deployed around their star, they would compose a non-rigid version of the Dyson shell mentioned below. Such a shell would not suffer from the drawbacks of massive compressive pressure, nor are the mass requirements of such a shell as high as the rigid form. Such a shell would, however, have the same optical and thermal properties as the rigid form, and would be detected by searchers in a similar fashion (see below). 

Dyson shell

File:Dyson Sphere Diagram-en.svg

A cut-away diagram of an idealized Dyson shell, a variant on Dyson's original concept, with a radius of 1 AU.

The variant of the Dyson sphere most often depicted in fiction is the "Dyson shell": a uniform solid shell of matter around the star. Such a structure would completely alter the emissions of the central star, and would intercept 100% of the star's energy output. Such a structure would also provide an immense surface which many envision would be used for habitation, if the surface could be made habitable. A spherical shell Dyson sphere in the Solar System with a radius of one astronomical unit, so that the interior surface would receive the same amount of sunlight as Earth does per unit solid angle, would have a surface area of approximately 28.1 Eha (Exa Hectare), or about 550 million times the surface area of Earth. This would intercept the full 384.6 yottawatts (3.846 × 10²⁶ watts) of the Sun's output; other variant designs would intercept less, but the shell variant represents the maximum possible energy captured for the Solar System at this point of the Sun's evolution.

This is approximately 33 trillion times the power consumption of humanity in 1998, which was 12 terawatts. There are several serious theoretical difficulties with the solid shell variant of the Dyson sphere: Such a shell would have no net gravitational interaction with its englobed star (see shell theorem), and could drift in relation to the central star. If such movements went uncorrected, they could eventually result in a collision between the sphere and the star—most likely with disastrous results. Such structures would need either some form of propulsion to counteract any drift, or some way to repel the surface of the sphere away from the star. For the same reason, such a shell would have no net gravitational interaction with anything else inside it. The contents of any biosphere placed on the inner surface of a Dyson shell would not be attracted to the sphere's surface and would simply fall into the star.

It has been proposed that a biosphere could be contained between two concentric spheres, placed on the interior of a rotating sphere (in which case, the force of artificial "gravity" is perpendicular to the axis of rotation, causing all matter placed on the interior of the sphere to pool around the equator, effectively rendering the sphere a Niven ring for purposes of habitation, but still fully effective as a radiant-energy collector) or placed on the outside of the sphere where it would be held in place by the star's gravity. In such cases, some form of illumination would have to be devised, or the sphere made at least partly transparent, as the star's light would otherwise be completely hidden. If assuming a radius of one AU, then the compressive strength of the material forming the sphere would have to be immense to prevent implosion due to the star's gravity.

Any arbitrarily selected point on the surface of the sphere can be viewed as being under the pressure of the base of a dome 1 AU in height under the Sun's gravity at that distance. Indeed it can be viewed as being at the base of an infinite number of arbitrarily selected domes, but as much of the force from any one arbitrary dome is counteracted by those of another, the net force on that point is immense, but finite. No known or theorized material is strong enough to withstand this pressure, and form a rigid, static sphere around a star. It has been proposed by Paul Birch (in relation to smaller "Supra-Jupiter" constructions around a large planet rather than a star) that it may be possible to support a Dyson shell by dynamic means similar to those used in a space fountain.

Masses travelling in circular tracks on the inside of the sphere, at velocities significantly greater than orbital velocity, would press outwards on magnetic bearings due to centrifugal force. For a Dyson shell of 1-AU radius around a star with the same mass as the Sun, a mass travelling ten times the orbital velocity (297.9 km/s) would support 99 (a=v²/r) times its own mass in additional shell structure. Also if assuming a radius of one AU, then there may not be sufficient building material in the Solar System to construct a Dyson shell. Anders Sandberg estimates that there is 1.82Template:E kg of easily usable building material in the Solar System, enough for a 1-AU shell with a mass of 600 kg/m²—about 8–20 cm thick on average, depending on the density of the material. This includes the hard-to-access cores of the gas giants; the inner planets alone provide only 11.79Template:E kg, enough for a 1-AU shell with a mass of just 42 kg/m². The shell would be vulnerable to impacts from interstellar bodies, such as comets, meteoroids, and material in interstellar space that is currently being deflected by the Sun's bow shock. The heliosphere, and any protection it theoretically provides, would cease to exist. 

Galaxy-level Dyson sphere

This construct follows the same principles as the ones before, but instead of around a star, this structure surrounds an entire galaxy. This is the most improbable of the Dyson spheres, and is consistent of a type-3 intellectual species on the Kardashev scale. 

Other types

Another possibility is the "Dyson net", a web of cables strung about the star which could have power or heat collection units strung between the cables. The Dyson net reduces to a special case of Dyson shell or bubble, however, depending on how the cables are supported against the sun's gravity. A bubbleworld is an artificial construct that consists of a shell of living space around a sphere of hydrogen gas. The shell contains air, people, houses, furniture, etc. It was invented to answer the question, "What is the largest space colony that can be built?" However, most of the volume is not habitable and there is no power source. Theoretically, any gas giant could be enclosed in a solid shell; at a certain radius the surface gravity would be terrestrial, and energy could be provided by tapping the thermal energy of the planet. This concept is explored peripherally in the novel Accelerando (and the short story Curator which is incorporated into the novel as a chapter) by Charles Stross, in which Saturn is converted into a human-habitable world. Stellar engines are a class of hypothetical megastructures, whose purpose is to extract useful energy from a star, sometimes for specific purposes. For example, Matrioshka brains extract energy for purposes of computation; Shkadov thrusters extract energy for purposes of propulsion. Some of the proposed stellar engine designs are based on the Dyson sphere.

A black hole could be the power source instead of a star in order to increase energy-to-matter conversion efficiency. A black hole would also be smaller than a star. This would decrease communication distances which would be important for computer-based societies as those described above. == Search for extra-terrestrial intelligence ==In Dyson's original paper, he speculated that sufficiently advanced extraterrestrial civilizations would likely follow a similar power consumption pattern as humans, and would eventually build their own sphere of collectors. Constructing such a system would make such a civilization a Type II Kardashev civilization. The existence of such a system of collectors would alter the light emitted from the star system. Collectors would absorb and reradiate energy from the star.

The wavelength(s) of radiation emitted by the collectors would be determined by the emission spectra of the substances making them up, and the temperature of the collectors. Since it seems most likely that these collectors would be made up of heavy elements not normally found in the emission spectra of their central star–or at least not radiating light at such relatively "low" energies as compared to that which they would be emitting as energetic free nuclei in the stellar atmosphere–there would be atypical wavelengths of light for the star's spectral type in the light spectrum emitted by the star system. If the percentage of the star's output thus filtered or transformed by this absorption and reradiation was significant, it could be detected at interstellar distances. Given the amount of energy available per square meter at a distance of 1 AU from the Sun, it is possible to calculate that most known substances would be reradiating energy in the infrared part of the electromagnetic spectrum.

Thus, a Dyson Sphere, constructed by life forms not dissimilar to humans, who dwelled in proximity to a Sun-like star, made with materials similar to those available to humans, would most likely cause an increase in the amount of infrared radiation in the star system's emitted spectrum. Hence, Dyson selected the title "Search for Artificial Stellar Sources of Infrared Radiation" for his published paper. SETI has adopted these assumptions in their search, looking for such "infrared heavy" spectra from solar analogs. Template:As of Fermilab has an ongoing survey for such spectra by analyzing data from the Infrared Astronomical Satellite (IRAS).  Identifying one of the many infra-red sources as a Dyson Sphere would require improved techniques for discriminating between a Dyson Sphere and natural sources. Fermilab discovered 17 potential "ambiguous" candidates of which four have been named "amusing but still questionable". Other searches also resulted in several candidates, which are however unconfirmed. 

Dyson spheres in popular culture

Popular culture uses many examples of a dyson sphere-some correct,whiles are off the wall.Much of the web material,and includes various science web pages,due represent the true scope and visual depict of the sphere.

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Dyson Spheres can as big as Jupiter,as Terra-Prime was originally supposed to be or as big as the orbit of the earth around the one.

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"Imagine the energy crisis of a really advanced planetary civilization. They've used up all their fuels, they depend on solar power. An enormous amount of energy is generated by the local star, but most of the star's light doesn't fall on their planet. So perhaps, they would build a shell, to surround their star, and harvest every photon of sunlight. Such beings, such civilizations, would bear little resemblance to anything we know.

—The Dyson Sphere in a nutshell, as described by Carl Sagan.

'Big Dumb Object' or Thats No Moon not big enough for you? Look no further. Sci Fi authors have made solar-system-sized artifacts into a trope of their own. The Trope Namer is physicist and mathematician Freeman Dyson, who theorized in a 1959 scientific paper that, given the ever-increasing demand for energy typical of industrial civilization, Sufficiently Advanced Aliens might need to capture all the energy radiating from a star.

While Dyson himself originally saw his concept as a cloud of many separate orbiting habitats and power-stations, most media depictions show a single continuous solid shell completely enclosing its star. This is an acute case of Sci Fi Writers Have No Sense Of Scale. Constructing such an artifact would probably put a civilization at least 2.0 on the Kardashev scale.

The technologies and resources needed to do it raise the question of whether a race that could build one would still need it. It has been estimated that constructing the sphere would require the energy equivalent of the lifetimes of several stars AND the raw materials of more than the entire solar system, which rather defeats the purpose of the initial construction.

For a real-life example: there is absolutely nothing stopping the human race from building a bridge across the Pacific Ocean. Humanity has all the engineering know-how and resources needed. So why haven't we? Well, we already have ships and airplanes, not to mention things like videoconferencing -- these are all already-existing ways to bridge the Pacific using the very same know-how and technology which would let us build that hypothetical bridge in the first place.

The Ringworld concept was created by science fiction author Larry Niven as a mid-point between this and a true planet because, as Niven put it in his essay Bigger Than Worlds (a discussion of Ring World Planets, Dyson Spheres, and other possible macrostructures), I like being able to see the stars at night. Something that a Dyson Sphere prevents.

This trope doesn't require an object to block all light from the star, but it does require construction on that scale. To be a Dyson Sphere, the artifact must:

1. be an artificial structure. Naturally-occuring structures don't count, though a nest built by a Space Whale would.

1. contain a star inside it (that is, a giant ball of gas lit by stable nuclear fusion initiated by the pressure on its core due to its own gravity, not some little glowing speck or a mythological god with a lantern, OK?)

1. contain an inside surface where people can survive (possibly with space suits) without being burnt to a crisp by the star.

1. be at least the size of a small solar system. Typically we're talking 100 million kilometers or more.

In fiction, Dyson Spheres tend to be abandoned and uninhabited. If they are inhabited, the residents are usually not at a tech level capable of building the sphere. This is because, if your protagonists run into a sphere whose residents are in the full flower of their technological might, they and their problems promptly get overwhelmed.

Subtrope of Hollow World. Compare Big Dumb Object and Thats No Moon. Not to be confused with the Dyson Ball, which is part of a vacuum cleaner.

Some useful notes on the Real Life physics of objects this size

• In response to letters prompted by his original paper, Freeman 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. The evolution of the term Dyson Sphere is an example of Memetic Mutation. Dyson himself referred to his idea as a shell or swarm, and his use of biosphere was in the ecological, rather than any geometric sense. But then Rule Of Cool caught up with him.

• The surface gravity of the outside of a stereotypical 1-AU solid shell is likely to be negligible. Gravitational acceleration due to the Sun out there is less than 1000 g. Calculus and physics (the Shell Theorem) tell us that the gravitational effect of any spherical shell we're outside of is equivalent to that of the same mass as a point source at the shell's center; we can assume that the sphere doesn't have mass orders of magnitude more than the Sun, considering that it has to be made of locally available materials and the Sun weighs much more than everything else nearby combined, so don't expect much.

• • Also, increasing the mass of the star increases its brightness, so the sphere would be larger as well.

• • It might be possible that a Sufficiently Advanced Alien has a reason to build a Dyson Sphere around a white dwarf, neutron star, or black hole, or has to build a smaller, 'hot' Sphere. In that case the gravity might be higher.

• The surface gravity on the inside of a 1-AU solid shell is also negligible. Newton's shell theorem predicts that the gravity anywhere inside a hollow sphere would actually be zero, so that the main gravitational force acting on a body at the inside surface would be the star at the center, which as stated above is not large.

• • Spinning such an object would allow for near-normal gravity at the surface, but as was discovered by Larry Niven, the strength-to-weight ratio of the material required to withstand 1g of centrifugal force across this scale would be something around 1000 times that of steel.

• • Of course, Speculative Fiction writers are allowed to Handwave it as 'a network of gravity generators', Functional Magic, etc.

• A Klemperer Rosette is a group of objects set to orbit together in a rotating pattern. Technically this may count if it's big enough to be considered a small solar system, and the objects were placed there artificially.

• A solid Dyson Sphere would not be stable around its star without some form of correctional thruster system or Applied Phlebotinum to keep everything bolted in place.

• • 'Harder' settings may couple the star to the mass streams of active supports holding up the sphere.

• A point which is often ignored is that a solid shell will not only have eternal day, but also, instead of reflecting sunlight into space, will reflect it upon the sphere itself. This means that a shell around a Sun sized star will have to be not 300 million km across, but more likely about twice as much in order to maintain reasonable temperatures or using materials either with high efficiency in the production of energy (if the interior wall is dedicated exclusively to energy production) or with a high thermal conductivity coupled with an interior wall with high absorption of radiation.

• • A reasonable partial solution to this is for a star-faring society (and any society able to build a Dyson Shell is likely to be star-faring at least potentially) to select a smaller, cooler star (say a class M) and build their Shell around it, letting it heat up to hotter intensities due to reflection.

• A Dyson sphere could be used as a computational node for a single massively powerful supercomputer, presumably either a segment of, or the entire physical being of, some kind of massively advanced Artificial Intelligence entity, presumably of the post-Singularity kind. Such an entity would be called a Matrioshka brain named after Russian Matrioshka dolls, because it may consist of layers of Dyson shells within each other, the inner layer being devoted to energy harvesting while the outer structures are devoted to computation.

 

Anime & Manga

• BLAME takes place inside of one. This is hinted at throughout the story, but the biggest piece of evidence comes later on when the protagonist finds a chamber that is absolutely massive. Its measured diameter is the same as that of the planet Jupiter.

• • This theory is given more creedence in the prequel N Oi SE, where a self-replicating superstructure begins construction, enveloping (and recycling) Earth and the Moon by the end of that series. It can be inferred that the massive room in BLAME! is where Jupiter used to be.

• The ending of Futaba Kun Change reveals the . It Makes Just As Much Sense In Context

• While not spanning the entire Solar System, in Sol Bianca Earth is like this. Interestingly, the government tries to hide the fact that the plant is already dead and thus the people live ON the sphere, not shielded by it on the planet.

 

Comic Books

• New Mutants, an X- Men spin-off from Marvel Comics, featured a Dyson Sphere belonging to Cannonball's then-girlfriend, Lila Cheney.

 

Literature

• In Alastair Reynolds's House of Suns, Dyson Spheres made out of perfectly reflective Ring World Planets are used to encapsulate stars that are about to go supernova.

• <span style="font-size:12.0pt;font-family:"TimesNewRoman","serif";mso-fareast-font-family: "TimesNewRoman"">Orbitsville''' and Orbitsville Departure by Bob Shaw featured a solid Dyson Sphere. (But in this troper's opinion totally wasted the concept on soap-opera plots.)

• 'Larry Niven''s Ringworld: the Puppeteers' Fleet of Worlds is a Kemplerer [sic] Rosette.

• • The Ringworld itself is a flattened Dyson Sphere - it is described as being like a ribbon encircling its sun, nearly a million miles wide and 300 million miles in diameter.

• A Dyson Sphere made of a forcefield holds the Sealed Evil In A Can in Peter F. Hamilton's Commonwealth Saga.

• The humorously tiled The Millennial Project: Colonizing the Galaxy in Eight Easy Steps features a more realistic version of a Dyson Sphere called a Dyson cloud. See here for more details.

• • It also proposed a solar-cell sphere around the orbit of Mercury, held up by the solar-sail effect and leaving a gap around the ecliptic for the planets and the aforementioned cloud.

• <span style="font-size:12.0pt;font-family:"TimesNewRoman","serif";mso-fareast-font-family: "TimesNewRoman"">Illegal Aliens'''. The inside of the shell was covered in solar collectors, and the people lived inside the shell, as basically it was a big spherical shaped space station.

• Neal Asher's novel Polity Agent features the Cassius Project, humanity's first attempt to construct a Dyson Sphere. One of the subplots kicks off when an antagonist tries to sabotage its construction.

• 'Iain M Banks''s Culture novels have Orbitals, which seem suspiciously similar to Ringworlds.

• • Orbitals are actually a lot smaller that Ringworlds - think Halo (it's where Bungie got the idea in the first place). The Culture does have Ringworlds (they lost three in the war with the Idirans) but they're rare and regarded as somewhat wasteful since you could build thousands of orbitals with the same material.

• • • Dyson Spheres are referenced in the casualty list of the Idiran War at the end of Consider Phlebas.

• The Doctor Who New Adventures novel The Also People is set in a Dyson Sphere inhabited by a society which seems suspiciously similar to Iain M. Banks's Culture.

• Part of The Time Ships by Stephen Baxter is set in a Dyson Sphere.

• In the final Hyperion book, The Rise of Endymion, the Ousters are growing an organic Dyson Sphere around a star. It does not have gravity. While

• The title object in Wall Around a Star.

• <span style="font-size:12.0pt;font-family:"TimesNewRoman","serif";mso-fareast-font-family: "TimesNewRoman"">Second Genesis''' by Donald Moffitt is mostly set on a Dyson Sphere composed of planet-orbit sized disks, used to power a massive interstellar transmitter (The rest of the story is set on another of Dyson's conceptual objects, a Dyson Tree that has been converted into a Living Ship).

• William Forstchen's Gamester Wars universe has a Dyson Sphere setting that's still being built-- the Precursors' ancient robots have been at it for millions of years and it's still only half-complete, because it's big. There's also a Ring World Planet and other stellar-scale objects in the same universe.

• Half of Century Rain is set in one of these, but it wasn't built for the normal reasons. The inside of the sphere is patterned with stars that match the stars in our own solar system, and by some pseudo-scientific method they shift as our own stars would, so that those inside the sphere don't know that they're not really on Earth.

• In Robert Silverberg's Across a Billion Years, some archaeologists discover an artifact left behind by a billion-year-old vanished civilization that leads them to the Dyson Sphere that the civilization disappeared into.

• Xenology lists several projects beyond even the scale of a normal Dyson Sphere.

• George Zebrowski's Macrolife mentions an alien solar system that consists of Worldships orbiting a black hole in a Dyson cloud. Later, a fleet encounters an interuniversal transport ship 100 million km in diameter.

• Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization discusses several types of Dyson Sphere-scale projects and construction materials, as well as Galactic Megastructures which are even larger.

• The jungle world of Pryan (World of Fire) in the Death Gate Cycle is eventually revealed to be a Dyson's Sphere. Not much is done with this concept, apart from the facts that there is no night on the planet except in areas where night cycles are created by artificial means, and its nature makes navigating the planet when one was expecting a more normally arranged world rather difficult.

• In Housuke Nojiri's Usurper of the Sun, the Sufficiently Advanced Aliens start building one around ours.

 

Live Action TV

• 'Star Trek' had multiple instances:

• • In a Star Trek The Next Generation episode, the Enterprise encounters such a sphere that was left abandoned for some reason, where an engineer had crashed his shuttle. The characters themselves, even with all their advanced technology and having encountered far more advanced aliens, are astonished that anybody would be capable of building such a thing.

• • There's also one in Star Trek New Frontier, but called a Thul Sphere after the financier. Needless to say, it gets blown up.

• • In the non-canon novel series Star Trek Titan, the crew of the U.S.S. Titan uncover evidence of the existance of what may be the largest lifeform in the galaxy, a living Dyson Sphere distantly related to an alien lifeform the Enterprise encountered in The Next Generation pilot, Encounter at Farpoint.

• • In one of the other non-canonical novels, part of the Star Trek Millennium trilogy, O'Brien is trapped in one of these for what seems like years as the Fate Worse Than Death meted to him by the Pah-Wraiths.

• In Gene Roddenbery's Andromeda the Magog Worldship is somewhat closer to the original concept of a Dyson Sphere but even more fantastic in some ways. It consists of twenty inter-connected planets surrounding an artificial sun. If the stresses involved in connecting twenty planet-sized bodies in stable orbits around a sun isn't enough, the entire thing could move.

 

Tabletop Games

• One of the C'tan stargods in Warhammer 40000 is sealed inside a Dyson Sphere. Whether it was imprisoned or sealed itself there is not quite clear (although the background seems to suggest the latter).

• Traveller. A Klemperer Rosette created by the Ancients exists in the Tireen system in the Vargr Extents.

• Spelljammer... First, Crystal Spheres as such (e.g. Realmspace has pseudo-stars, walking cursed people and big magical scroll-like writings on its inner surface). Also, while Penumbra's Stellar Well isn't a Dyson Sphere, it's a large enough part of it, and the disk behind it is of Dyson Sphere scale.

• Mage: The Ascension has a Dyson Sphere that belongs to the Void Engineers; the Copernicus Research Center functions as an Earth-away-from-Earth for a large number of Engineers, researchers, and their families. This actually puts the Void Engineers under suspicion: People started thinking that it'd be unlikely they managed to build 'The Cop' on their own, and some wonder if they got it from some... friends... they met beyond the stars. In one outcome of The End Of The World As We Know It, the Void Engineers retreat to the Sphere en masse and leave the Universe in their own portable biosphere.

• AT-43'''''s Therians freaking love Dyson Sphere, so much in fact they plan on making the whole universe into them.

• Magic The Gathering has a plane called Pyrulea, which is a Dyson Forest.

 

Video Games

• Prey takes place, for the most part, in an cybernetic living Dyson spaceship, the Sphere. It's essentially a smaller version of this trope, with a small dwarf star at its core.

• Shows up in the final level of Freelancer.

• Strangely, the world of Atreia in the MMORPG Aion was one. Then it broke.

• <span style="font-size:12.0pt;font-family:"TimesNewRoman","serif";mso-fareast-font-family: "TimesNewRoman"">'Halo' Wars has a micro Dyson Sphere in the finale. The Expanded Universe has one the size of a solar system; time passes much slower inside the sphere than it does outside.

• • Here an actual reason for why an advanced civilization would build one is given. The Shield Worlds were bunkers where the Forerunners would take shelter when the Halo Array was triggered; considering they were trying to shelter the entire population of an interstellar empire and possibly less-advanced sentient species, it is understandable they would need a lot of room.

• • 'Halo 4' will take place largely from within a Dyson Sphere called Requiem. It is similar to the Halo Wars example, but instead of an inside-out planet, this sphere is a shell which contains another planet inside. The shell does appear to have a geology of its own, though.

• In Infinite Space, . .

• In Mass Effect 2, Legion states that the end desire of the mainstream geth is

• You can actually build one, as of Space Empires IV... or you could build a massive war fleet for one-tenth the cost.

• One alien race in Fargate has one of these as their home system. As these aliens possess no apparent mechanical technology but are the masters of biological manipulation, the entire double-layered Dyson Sphere is grown organically. It looks very fleshy.

• In X3 Terran Conflict,

• The Ascent to Transcendence ending of Sid Meiers Alpha Centauri suggests a variant: stellar encapsulation, effectively bottling the star without dismantling the planets of the system or otherwise affecting their biospheres.

 

Webcomics

• The F'sherl-Ganni of Schlock Mercenary have built several of these. They call them buuthandi, a shortened version of a F'sherl-Ganni phrase that roughly translates to This was [expletive] expensive to build (fully transliterated as expensive and expensive-expensive [expletive] we built.). At one point, the characters gather a fleet to assault one.

• • The author tried to depict them more realistically then a solid shell build around a star. In this setting Dyson Spheres (there are 5, well 4 now after one was destroyed) are constructed from a flexible material. They are practically bubbles around a star kept inflated by the solar wind. Habitats are anchored to the interior of the sphere. Setting also has widespread gravity generators, so that's not a problem either.

• The Sluggy Freelance Punyverse is revealed to be contained in one.

• In Dreamwalk Journal the world of Cyeatea, with its immense jungle housing a peaceful culture of sexually-insatiable anthropoid insects and spiders, is apparently a habitat within a Dyson Sphere called Velveteen. However, there is only one reference to this in a related text piece.

 

Web Original

• Many types appear in Orion's Arm. Most impressive is probably the suprastellar shell, a solid Dyson Sphere (actively supported) that people live on the outside of.

    At Maveric Universe Wiki,an ancient alliance of Elder Civilizations,called the Atlantean Allliance and Tauron Alliance have created a series of Dyson Spheres,as sanctuary   worlds for their and other worlds to populate.They also manuefacture fuel for great fleet of Star Ships,Worldships and so on.Each so far are named each primary civilization that makes use of them,added with later term ‘’Prime’’.Hense one Dyson-Sphere is refered to as Atlantis-Prime,to use primary for the Atlanteans,while another might be primary use for Terrans would known as Terra-Prime.

Western Animation

• Umbra, the Big Bad in the 1984 animated series Mighty Orbots was a Dyson Sphere. He was the core of the Shadow Star, a world so large it contained its own internal sun.

 

Real Life

• There are quite a few stories of small children getting the misconception Earth is like this.

• • And of some grown-ups mimicking this, completely disregarding the fact that Earth would be a Dyson Sphere if the Hollow Earth theory was proved true. To summarize: Earth is hollow and there is a tiny star inside, providing enough heat and light to sustain life. It Gets Worse when you ask them who is inside.

• Some folks at SETI want to use some recently installed IR telescopes for searching after Dyson Spheres. While some feel it would be a waste of the usage time of a scientific instrument, others say that these spheres should stick out like sore thumbs and therefore it would be silly at least not to check.

• • This has been done, as part of the WISE spacecraft's all-sky infrared survey. Among other things, WISE was designed to discover brown dwarf stars with surface temperatures similar to Earth's within ~30 lightyears of the Sun. It would also have found 1-AU-radius Dyson Swarms around Sun-like stars out to >3000 lightyears. It didn't find any.

Notes

Fiction

As noted above, the Dyson sphere originated in fiction, and it is a concept that has appeared often in science fiction since then. In fictional accounts, Dyson spheres are most often depicted as a Dyson shell with the gravitational and engineering difficulties of this variant noted above largely ignored.