"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.
Big Dumb Object
— The Dyson Sphere, in a nutshell, as described by Carl Sagan
or Planet Spaceship
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 network
of many separate orbiting habitats and solar power-stations
, most media depictions show a single continuous solid sphere
completely enclosing its star. This misconception 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.
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:
- be an artificial structure. Naturally-occuring structures don't count, though a nest built by a Space Whale would.
- 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?)
- contain an inside surface where people can survive (possibly with space suits) without being burnt to a crisp by the star.
- 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 Planet Spaceship
. 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 the "sphere" misconception and 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 1/1000 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. However, it might be possible for a Sufficiently Advanced Alien to build a smaller, 'hot' Sphere, in which case the gravity would 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.
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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 noise, 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 Shimerus are Human Aliens from a ringworld made out of nano-engineered giant ivy. 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.
- In Yu-Gi-Oh! ZEXAL, Christopher Archlight (called simply V most of the time) uses a monster called Number 9: Dyson Sphere, which is Exactly What It Says on the Tin. In fact, in terms of sheer size, it's no-doubt the biggest Duel Monster in the history of the franchise, being the size of a small star, and it seems to be one of the most powerful Numbers. Despite this, in his duel against Kaito, Kaito manages to destroy it and win the duel.
- In the 2013 Valvrave the Liberator, the settai or setting makes several mentions of a Dyson Sphere and it is implied that Jior is based on such a structure. However the story never delves into the nature of the sphere or its usage, it just has the protagonist living in a runaway module from a Dyson Structure.
- New Mutants, an X-Men spin-off from Marvel Comics, featured a Dyson Sphere belonging to Cannonball's then-girlfriend, Lila Cheney. It had actually been built and abandoned by unknown aliens, but Lila (whose power is intergalactic teleportation) found it and claimed it as her base of operations. Since she can only teleport over intergalactic distances, any short-range travel requires a double teleport, with the Dyson Sphere being a convenient transit point. Thought the Dyson sphere is featured in the opening and publicity artworks as a nice, yellow-greenish background
- In New Avengers Vol 3, Tony Stark pays aliens to build a Dyson Sphere for him as part of a alternate world destroying weapon he is preparing.
- Guardians of the Galaxy: The modern-day team visits one early on in vol 2., when a fissure in time and space opens up there. They arrive and find that the locals aren't there. And when they do find them, they really wish they hadn't. Note that only the tiniest fraction of the sphere's surface was inhabited, protected from the local star by a shell, which the team had to open to get rid of what they found. The trouble with that started when they wound up a good distance away from the control panel required to re-seal the shell.
- In Undocumented Features, the Republic of Zeta Cygni makes its home in a Dyson Sphere (which happens to be home to one of the most blatant Shining Cities in written fiction.
- Transcendent Humanity has one for the Sol System in order to make the best use of the sun's energy and raw materials. It's made abundantly clear that materials required for it made it necessary for humanity to take material from the sun itself, turning a G Class yellow dwarf sun into at the very least a K Class yellow (or orange) dwarf in building it.
- Star Maker by Olaf Stapledon contains the first known instance of this, long before Freeman Dyson came up with it and gave it a name. During the travels of the narrators, they encounter several of these that range from uninhabited spheres, spheres composed of artificial beings and artificial-but-sentient spheres that share a symbiosis with their inhabitants who are also artificial and sentient beings. It's even more complex than it sounds.
- 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.
- Orbitsville and Orbitsville Departure by Bob Shaw featured a solid Dyson Sphere.
- 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.
- Illegal Aliens by Phil Foglio and Nick Pollotta. 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.
- Two(?) spheres are actually mentioned. The second was discovered in a previously-unknown sector of space. When opened, it was found to contain a slightly smaller sphere. Which itself had another inside, and so on. The discoverers abandoned their investigation after going several layers deep, positing that "With so many amateur lunatics around the universe, nobody wanted to meet professionals."
- 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' The Culture novels have Orbitals, which seem suspiciously similar to Ringworlds, although a lot smaller. 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 Culture/Idiran War at the end of Consider Phlebas.
- The Doctor Who New Adventures novel The Also People has two.
- The main plot is set in a Dyson Sphere inhabited by a society which seems suspiciously similar to Iain M. Banks's Culture and who have orbited a planet inside it. As a mark of the dwellers sense of humour the planet is called Whynot and is home to a massive supercomputer named God.
- The other appears in a brief flashback to Bernice's past when she was a field archaeologist. It is an abandoned ruin, slowly disintegrating, and its current inhabitants are a species that evolved in it after the start of its disintegration and abandonment.
- Part of The Time Ships by Stephen Baxter is set in a Dyson Sphere.
- In the final book of the Hyperion Cantos, The Rise of Endymion, the Ousters are growing an organic Dyson Sphere around a star. It does not have gravity. While this particular one is heavily damaged by the Pax war fleet (at least, the narrator assumes the damage was heavy - he is not a very smart guy and only saw the start of the battle) it is revealed that there are more in existence.
- The title object in Wall Around a Star by Frederik Pohl and Jack Williamson. In that case, the inhabitants live on the low-gee outside of the sphere.
- 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.
- An unfinished Dyson Sphere is found in Andrei Livadny's The History of the Galaxy series. It was built 3 million years ago by the Insects as a way to escape the oncoming swarm of Forerunners (mindless Planet Eaters). The idea was to hide the star from the outside, as the swarm is attracted to starlight. They manage to build most of it, but the swarm still reaches them. Strangely, the Forerunners don't consume it but merely damage it. The sphere is part of the ancient Portal Network. Interestingly, one novel reveals that the "sphere" is a misnomer, as the structure is, in fact, an ellipsoid and looks like an American football from the side. The wider sides are the habitable ones. Naturally, the Insects' modern-day descendants have forgotten all about their glorious past.
- Karl Schroeder's "Virga" series takes place inside a kind of mini-Dyson Sphere: a hollow shell roughly the size of Earth, filled with air and lots of tiny little artificial stars orbited by floating cities.
- Star Trek Expanded Universe:
- A Star Trek novel about the sphere in TNG: "Relics" indicates that the area around this sphere is nearly devoid of other star systems, because the ancient builders of the Dyson sphere had consumed them (stars and all!) for raw materials. It also implies that the sphere's builders would go on to become the Borg.
- 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 existence 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.
- The Star Trek: Destiny trilogy features the Caeliar. They build a sphere around their sun to hid it from the rest of the galaxy and another smaller one around their planet which draws energy from the sun's sphere allowing them to make the Omega Particles which power their civilization. An offshoot faction of them which were sent back in time, by an accident which nearly destroyed their civilization, billions of years to one of the first galaxies to ever form build spheres around every single star in the galaxy thereby harnessing not just the full power of a single star, but the full power of an entire galaxy. They do this in order to create a Stable Time Loop and CAUSE the 'accident' which sent them back in time to begin with. The Enterprise E briefly visits this 'shrouded galaxy' by traveling through a subspace corridor and realize any race capable of doing such a thing is one best left alone, and very quickly gets out of there.
- In David Brin's Uplift universe retired species live in fractal worlds that are similar to dyson sphere built around red dwarf stars from hydrogen snow impregnated with carbon fibers. The structure also extends inward towards the star in fractal patterns to maximize "window space".
Live Action TV
- 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.
- In the Star Trek: The Next Generation episode "Relics", the ''Enterprise' encounters such a spherenote that was abandoned after the encased star became unstable, rendering the inner surface uninhabitable. 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.
- 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.
- Magic: The Gathering has a plane called Pyrulea, which is a Dyson Forest.
- 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.
- AT-43's Therians freaking love Dyson Sphere, so much in fact they plan on putting every solar system they can find into them.
- Traveller. A Klemperer Rosette created by the Ancients exists in the Tireen system in the Vargr Extents.
- One of the C'tan stargods in Warhammer 40,000 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).
- In the Space Marine Battles novel Malodrax the titular planet is surrounded by a orbital coral reef, because the writers in this franchise will go to any length necessary to drive home the point that Space Is an Ocean. Interestingly, the reef does nothing to block out the planet's twin suns... though Malodrax is a daemon world, so it probably gets free sunlight from the Warp instead.
- One exoplanet in Eclipse Phase is believed to be a Dyson sphere. Who built it, and why, and why the Pandora Gate is on the outside, and why it shoots down any attempt at orbit, and at least a hundred other things about it, are not known.
- The Exalted Shard known as Heaven's Reach has the Primordials exist in this form and similarly scaled hyperconstructions. Malfeas in particular is a Dyson sphere wrapped around a green sun, with a demonic city on the inside.
- In Yu-Gi-Oh!, there is an Xyz Monster called Number 9: Dyson Sphere, a Real Life version of the card used by V in the anime. (See the entry in the Anime/Manga folder above.)
- Prey takes place, for the most part, in an organic/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.
- 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.
- Probably not that much, though. A Dyson sphere the size of Earth's orbit would have over fifteen trillion times the surface area of Earth. That's more room than would be necessary for a civilization spanning the entire galaxy, with multiple inhabited planets per system.
- 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, the Dyson Sphere covers the Sun, absorbing its energy to empower the True Void Gate. Taranis successfully destroyed it in the end of the game at the cost of his own life, preventing the Overlords from destroying the universe further.
- One level of Homeworld takes place inside of a partially finished Dyson Sphere. The builders are nowhere to be seen and the area is filled with clutter and wreckage. Like most of the game, the level is sheer Scenery Porn with vast sections of plate in the background, still so distant they're unreachable.
- In Mass Effect 2, Legion states that the end desire of the mainstream geth is to build a structure somewhat analogous to a Dyson Sphere and upload each one of their individual programs into it. The geth gain proportionally in intelligence as they mass together, with more bodies or "mobile platforms" available meaning faster processing and higher thought processes. If every geth were able to simultaneously occupy one such super-structure, they would become nigh-omniscient. As of Mass Effect 3, they've finished it....just in time for the quarian Migrant Fleet to roll in with a new weapon that disables geth, who then destroy the superstructure, which houses the majority of the geth "species" and utterly shattering their ability to process and analyze data. The geth revert to survival mode, and turn to the Reapers for code upgrades to protect them from immediate destruction by the quarians.
- 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, a plot leads you to The Hub, an ancient space station inside a Dyson Sphere. However, the latter orbits a star, and looking outside, you can see more of them, like in Dyson's concept.
- The Ascent to Transcendence ending of Sid Meierís Alpha Centauri suggests a variant: "stellar encapsulation," effectively bottling the star without dismantling the planets of the system or otherwise affecting their biospheres.
- The Polycon total conversion for EV Nova contains several of these, including at least one Dyson cube.
- The ending cutscene of Mission Critical has the protagonist travel to the future (a positive one this time), where humans and ELFs live in peace. Earth is gone and has been replaced by a Dyson Sphere, with the humans living on the inner surface, while the ELFs live on the outside, as they don't need air or heat.
- Star Trek Online's Season 8 expansion "The Sphere" takes place inside of one as the Federation, the Klingon Empire and the Romulan Republic fight the Voth for possession of Omega Particles.
- Space Pirates and Zombies has stars encased in glass cages as window dressing for some maps.
- 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.
- 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.
- 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. The one and only solid Dyson Sphere which people live on the inside of is called "The Impossible Dyson" and exists only in a virtual reality.
- 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.
- 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. Just 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.
- On the other hand, there IS at least one object, that could be a Dyson Sphere, judging by it's visual properties.