I can think of 3 kinds of big.

  • By volume
  • By a linear measure
  • By mass or weight

Bonus points for all three. Extra bonus points for the object being realistic in construction.

Let's add to it that it not be naturally occurring.

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    Perhaps consider removing the 'bonus points' .. how will you award them? – Tim Post Feb 19 '11 at 21:30
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    @Tim Post: perhaps consider growing a sense of fun. But to answer, I awarded them by picking the answer I did. – DampeS8N Feb 20 '11 at 2:22
  • By far not as big as Ringworld, but since it seems to be described in a relatively uncommon book, I'll mention The Ship, described by Robert Reed in his novels Marrow and The Well of Stars. It's a spaceship the size of Jupiter, containing, well ... a surprise ;-) – takrl Jun 16 '11 at 10:48
  • I have been known to award bonus points for answers I really like, by means of awarding a bounty. – Flimzy Nov 3 '11 at 1:18
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    Would the Tardis count for the "By Volume"? It's bigger on the inside, and as big as it needs to be! – AidanO Aug 15 '12 at 9:22

34 Answers 34


The biggest in terms of volume would probably be a Matrioshka brain.

A Matrioshka brain is a collection of multiple Concentric Dyson Spheres which make use of different wavelengths of light.

Here's the list from Wikipedia's article on Megastructures where I found it:

  • The Alderson disk is a theoretical structure in the shape of a disk, where the outer radius is equivalent to the orbit of Mars or Jupiter and the thickness is several thousand miles. A civilization could live on either side, held by the gravity of the disk and still receive sunlight from a star bobbing up and down in the middle of the disk.
  • A Dyson sphere (also known as a Dyson Shell) refers to a structure or mass of orbiting objects that completely surrounds a star to make full use of its solar energy.
  • Larry Niven's Ringworld is an artificial ring with a radius roughly equal to the radius of the Earth's orbit. A star is present in the center and the ring spins to provide artificial gravity.
  • A Matrioshka brain is a collection of multiple Concentric Dyson Spheres which make use of different wavelengths of light.
  • A Stellar engine either uses the temperature difference between a star and interstellar space to extract energy or serves as a Shkadov thruster.
  • A Shkadov thruster accelerates an entire star through space by selectively reflecting or absorbing light on one side of it.
  • Topopolis (also known as Cosmic Spaghetti) is a large tube that rotates to provide artificial gravity.

A couple of the others that move entire stars around would probably be considered bigger in terms of mass if you count the mass of the star.

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    feel free to split that up into different answers. So we can all vote up the biggest ones. I'm not looking for a list. I'm looking for the BIGGEST one. – DampeS8N Jan 12 '11 at 16:22
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    @DampeS8N: I separated out the one I think is biggest. – Bill the Lizard Jan 12 '11 at 16:28
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    How does the Matrioshka brain uses different wavelengths of light? – pupeno Jan 12 '11 at 17:38
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    The point of the Matrioshka brain isn't so much to capture all the energy as to convert all the matter of the solar system into computational power. – user1030 Jun 6 '11 at 21:46
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    There is a bigger structure discussed, though I don't know if it has ever been used in a story. In his essay, Bigger than Worlds, Larry Niven discusses several, getting progressively larger, finishing up with his "megasphere". Basically, a Dyson sphere around the center of the galaxy rather than a single star. "We live in free-fall, above a surface area of tens of millions of light-years, within an atmosphere that doesn't thin out for scores of light-years." It's the final essay in Jerry Pournelle's collection, The Endless Frontier, Volume 1. – William B Swift Aug 27 '12 at 5:52

In Greg Egan's Diaspora, the manufactured objects at the end of the characters' journey are inconceivably vast in terms of our universe. Each sub-atomic particle contains an entire universe, each sub-atomic particle of which contains an entire universe, then iterate millions of times until you get to our universe.

Nothing else in SF comes within trillions of orders of magnitude of being as large.

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    Woah! Nice one! – DampeS8N Jan 12 '11 at 17:39
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    +1. If there were more writers like Greg Egan, then this question would pretty much be like “what’s the largest number dreamed of in mathematics”… – PLL Feb 7 '11 at 5:50
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    I'd like to point out that it's theorized, albeit with little credibility, that the universe is a strange loop, that subatomic particles might eventually become a universe if you go small enough, say beyond a quark. Most people dismiss this because it sounds a hell of a lot like stoner-talk, which is shown in Animal House. – Apoc326 Apr 14 '11 at 6:16
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    @Apoc326, theorized by who? I assume you mean hypothesized. When talking about science, a theory is something well described and understood that accurately describes what can be observed. – DampeS8N Jun 2 '11 at 12:01
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    @DampeS8N, Sorry about that. I wasn't thinking that a choice of words that are interchangeable in common parlance would warrant correcting on a relatively casual site. Yes, I did mean hypothesized. There are a few ideas that have been published regarding the "universe" as a strange loop" idea that I mentioned. – Apoc326 Jun 3 '11 at 0:13

Isaac Asimov's Multivac.

In "The Final Question," Asimov refers to the last version of Multivac as the known universe. It finally becomes a god when it answers the question: Can entropy be reversed?

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    Specifically, The AC creates a new universe. – Steve Melnikoff Jan 15 '11 at 16:11
  • As a creation of our creation, could we therefore claim the Universe as the largest creation in Sci-Fi? – Jeff Feb 8 '11 at 19:15
  • @Steve: Proof by example is still proof. – Sukotto May 23 '11 at 16:08
  • @Sukotto: indeed. I agree with the answer; I was just attempting to add a little more explanation. – Steve Melnikoff May 23 '11 at 16:21
  • Similarly at the beginning of Stephen Baxter's book Manifold Time, the entire Universe is connected computationally (probably some pieces physically and some pieces by radiation) as a type of giant computational engine/computer. – Jim2B Feb 27 '15 at 5:34

A device that's surrounding a star is fun but why not use those stars to build something? Fry did it!

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How about the Great Attractor created by the Xeelee in Stephen Baxter's Ring? Being an artificial structure of galactic super-cluster proportions, it should at least be on the list.

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    Vacuum Diagrams has a plethora of megastructures -- the Great Attractor probably the largest 'engineered structure' but there are indications of even bigger Works -- including architecting a 'low density field' millions of light years across by harvesting matter from several galaxies. The Ghosts also attempt the construction of a dark matter star... :) – Joseph Weissman Mar 18 '11 at 20:05
  • This is certainly the largest by far, being millions of light-years in diameter. – Stephen Collings Mar 9 '13 at 1:30

In Stargate Atlantis the star gate's on Earth and Atlantis create a wormhole three million light years in length. It is a single engineered object when instantiated. Of course three million light years is its perceived external length; presumably it is much shorter when travelling through it.

The wormhole in Stargate Universe at the start of the series is much longer (but I don'r recall how long).

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    Also in Stargate Universe they discover the Ancient Starship Destiny's mission was to investigate some background radiation from the creation of the Universe that seemed to indicated intelligent life, possibly that our entire Universe is created. I think that qualifies as being pretty big. – Jonathan Miller Aug 27 '12 at 20:13
  • nah, the universe was much much smaller then. – John Meacham Mar 18 '15 at 7:50

Not as big as an universe, but the "Hitchhiker's Guide to the Galaxy"'s planet-builders are impressive and fascinating.

alt text

Unfortunately, the planets would be naturally occurring, but, who knows at the end...

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    Actually, this might be the smallest thing on this list. :) – DampeS8N Jan 12 '11 at 20:07
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    In the book, the Magrathea factory floor is much larger on the inside than the outside, being large enough to work on several planets at once while fitting inside Magrathea itself. – Goodbye Stack Exchange Feb 18 '11 at 0:58
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    Building on what neilfein said, the "factory floor" as it's called is in another dimension, and with lighting similar to that of a decent star, the outer walls of the factory floor are hardly even visible, depending on how reflective that surface is, that could be a MASSIVE distance away, making it a possible candidate for the Volume winner. – Apoc326 Apr 14 '11 at 6:19
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    The Hitchhiker's Guide also has the house of Wonko the Sane, which contains almost all of the whole universe. – b_jonas Sep 29 '13 at 11:41

In The Galaxy Railways there is a galactic size interstellar railway system. (This is the same universe as the Harlock Saga, and Galaxy Express 999)


Ringworld However, I know you guys can do better! It is roughly 300 million miles in circumference and about 1 AU in radius (i.e., 93 million miles). It is composed of material with a tensile strength close to that of the strong nuclear force. It is roughly as massive as all the planets in a star system.

  • One of my favorite books. I've replaced the book twice, finally getting a hardback. – Goodbye Stack Exchange Feb 18 '11 at 0:56

Schlock Mercenary has a power generator built from the Galactic Core. It was originally built as a sort of trojan-horse (the beings who designed it wanted our galaxy destroyed, the beings who built it were misled into thinking it was just a generator). It was stopped from being a bomb and kept as just a generator by an alliance of pretty much every sapient around, along with the formation of the largest AI around.


In "Bill, The Galactic Hero", ships are powered by a "Bloater Drive" which causes the ship to expand until it's as big as the galaxy. When the ships are that big, the individual atoms are so far apart that no one notices the presence of the ship. The ship is then reduced back to its original size at a different location.

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    That would be one unhappy trip if it doesn't also do it to the people... I guess that might be unhappy too. Just an unhappy thing all around. Especially if it breaks down mid-way through. – DampeS8N Feb 18 '11 at 1:15
  • It also does it to the people. On his trip away there is a little slippage and Bill's home planet comes through the wall of the ship to his room, then shrinks an vanishes. – Oldcat Aug 13 '14 at 17:46

In Peter Watt's Blindsight, the alien artifact Rorschach is incredibly massive (although shadowed by a nearby planet), but there are indications that it is constantly growing, possibly beyond plantery size.

In Alastair Reynold's Pushing Ice, the structure in which the ships are trapped is engineered and at the end it is indicated that its size is immense (possibly light hours in scale).


In the Star Trek universe, it’s surely the Borg Collective. It spans a significant proportion of our galaxy.

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    hmm. Interesting take on the idea of an 'Engineer Object.' – DampeS8N Feb 21 '11 at 3:51
  • The Slaver Empire, referred to in the animated series episode "The Slaver Weapon", occupied the entire galaxy a billion years ago, and so was bigger than the Borg Collective. There are plenty of empires in SF that span multiple galaxies. But I wouldn't call an empire an "engineered object". – Keith Thompson May 3 '15 at 22:43
  • @KeithThompson: Point taken, but the Borg Collective isn’t merely a large empire consisting of billions of individual biological units. I can easily argue that the Borg Collective is a single ginormous computer/AI in a way that living civilizations aren’t. – Timwi May 21 '15 at 12:48

In Time Keeps on Slippin, an episode of Futurama, Fry uses a Bad-Ass Gravity Pump to move a whole mess of stars to spell out a message to Leela. The message reads:

"I Love You, Leela."

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    Wow! I wonder how many civilizations were wiped out by that love letter. – Bill the Lizard Jan 12 '11 at 16:47
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    @Bill the Lizard: Eeehh.. They were all destroyed in a Globe-trottered up Doomsday Implosion later on, anyway... – DampeS8N Jan 12 '11 at 16:52
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    Nothing says, "I love you" like omnicide. – Jeff Feb 8 '11 at 19:16

In Dan Simmons' Endymion books, the Ousters were growing modified trees in orbit around a star, intending to eventually enclose it completely in a living Dyson sphere. I remember the phrase "Leaves the size of continents". Though they did not do so in the book, their plan was to eventually do this with other stars, and maybe connect them, to fill the space between with life. I give them credit for thinking big.

Also, in Carl Sagan's Contact,

at the very end of the book it is mentioned that a message is hidden in the digits of PI, which suggests that all of space/time was created by something...

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    Hmm.. Not necessarily. Given a starting digit, any string of digits can be found in pi. Here is a fun illustration – DampeS8N Feb 22 '11 at 13:50
  • @DampeS8N - Not disputing reality, but in the book, after enough digits the message appears, then a series of 1s and 0s, then the last digit. – JohnWinkelman Mar 18 '11 at 21:07
  • IIRC, the 1s and 0s formed a circle when arranged in a matrix. – Ferruccio Jun 16 '11 at 13:11
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    @DampeS8N: That is conjectured (and widely suspected, I think) but not proven. – user1030 Mar 3 '12 at 21:40
  • I can disprove it. 1 repeating forever is not found in pi. Any finite string might fit, but not any string. – Oldcat Aug 13 '14 at 17:48

In Terry Pratchett's Strata, the protagonists' job is to build habitable planets with fake histories, such as fossils for beings that never actually existed. There seems to be an irresistible urge for such builders to include little impossibilities as signatures. The characters do learn more during the book, and...

At the end of the book, the protagonists find one of those little indications that their Universe was built by people with the same "signature" habit.

  • I was going to bring up the fact that The Hitchhiker's Trilogy is entirely dependent on the concept of constructed planets, but this seems like a similar thing. – Adele C Mar 3 '12 at 22:57

In Stargate universe, Rush discovered that the Destiny was launched to investigate a hidden message written onto the cosmic microwave background. Presumably some intelligence that existed prior to our universe's existence was able to emplace this message using undreamt of physics. Unfortunately the series terminates, so we will never find out who (or what) created it for what purpose. But it does span the entire universe!


In mass this might not be very big, but in terms of the scale of distance it covers, it's HUGE - the stargate's in the stargate series. A series of wormhole transports that span not only this galaxy, but connect over to another (Andromeda) galaxy.

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    The network also extends to the Pegasus galaxy in Stargate Atlantis – Apoc326 Apr 14 '11 at 6:22
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    The McKay/Carter Intergalactic Gate Bridge would be a nice candidate here too! – AidanO Aug 15 '12 at 9:20

How about the "Fleet of Worlds" - the home planets of the Pierson's Puppeteer race. Consisting of the actual homeworld, called "Hearth", and its agricultural worlds, arranged in a pentagonal Klemperer rosette. and accelerated to 80% of light speed by inertialess drives.


In the Cyberiad from Stanisław Lem someone constructs a giant robot out of nearly all the matter in the Universe. The whole story is quite tongue-in-cheek, but it might still qualify.


I voted for the dyson sphere as being the biggest realistic. If you want something that's not as big but maybe more realistic - then the culture ships from the iain banks books. Ships that are miles long, housing millions of people, other ships and capable of building other ships.

  • not familiar, are they FTL? – DampeS8N Jan 12 '11 at 18:52
  • What about the multiple dyson sphere's in Iain M Banks book Matter, on the Shellworld of Sursamen which is vast dyson spheres wrapped around each other, with a more ascendant race on higher levels. At the core is the super advanced alien, and on level 6 or 7, live the parasites of the super advanced alien creature, who have advanced far enough to get their own level. Each sphere is vast. – scope_creep Jan 17 '11 at 18:38
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    @DampeS8N - Yes to the FTL. The ships were one of my favorite things in the Culture series. They had an interesting concept that the more massive a vessel, the higher speeds it could obtain. These massive city sized ships would cruise around regular circuits or explore new areas, dropping and picking up smaller ships in different quadrants. Because of the disparity of speeds obtainable, they had tug-style ships that could slow down, pick up a smaller vessel, then boost it up to speed for a rendezvous. – Saiboogu Jan 19 '11 at 1:54
  • Hm, if they were FTL then they can't be more realistic. Since it would just take a very long time to make the Dyson Sphere without FTL, but it could be done. – DampeS8N Feb 18 '11 at 1:10
  • Not sure the Shell Worlds are Dyson spheres. Dyson Spheres are structures designed to encompass a star and gather its output. The Shell Worlds are just shells built onto a (very big) superstructure. – Rob Feb 22 '11 at 23:12

Perhaps not the biggest, but the computers in David Zindells A Requiem for Homo Sapiens trilogy, The Broken God being the first, the computers are truly vast covering 300k planets with each planet computer associated with a star to power it. The plot deals with people being vastened from normal humans into each of these computers, and some of the vast computer sentient entities being de-vastened into a childs toy, after being destroyed. A trully excellent series of books worth a read, about the ascendency of man, written in Zindells poetic language.

  • What allows them to communicate between planets? Some kind of FTL communication system? – DampeS8N Jan 17 '11 at 4:28
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    Communication through the Manifold, (the place underneath quantum foam), the sort of foundations of reality or matter. Well worth a read. Start out main hero and his tribe have genetically engineered themselves back into Neanderthals who travel the Manifold in ships looking for new routes. I'll say no more. – scope_creep Jan 17 '11 at 18:30
  • The Wikipedia plot page describes only the first coupla hundred pages of The Broken God. Its a hard SF book. – scope_creep Jan 17 '11 at 18:33

The structure simply known as The City or the Megastructure in Tsutomu Nihei's Blame! appears to outclass everything else here.

It's a classically engineered structure (i.e. no quantum "there's an entire universe inside!" cop-outs) that extends roughly spherically outwards from the center of the solar system to a point at or beyond the orbit of Jupiter. It's constantly expanding, being built by out-of-control AIs. It's multi-leveled ("the megastructure" nominally refers to the constructs separating the levels but is also shorthand for the whole thing sometimes) and so the theoretical "habitable volume" is enormous, although in practice few areas have oxygen, or gravity, or lack of killer androids, or etc.

Nominally this makes it a Dyson sphere, or rather a series of Dyson spheres, but I'm not aware of any other work of fiction that portrays a Dyson sphere this large. It also has some elements of a Matrioshka brain, as some kind of computer network appears to run throughout it.

  • (nitpick) there is at least one more universe inside, probably several (Toha Heavy Industries is bigger on the inside and connects to alternate realities), even more if you count the Netsphere. That doesn't take anything away from the external size though. – user36551 May 12 '15 at 18:10

I think we all are forgetting "The Death Star" here and ultimate weapon as big as a few hundred suns.

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    If you refer to Star Wars' Death Star, its actual size / volume of the death star has not been specified in the movies, but it is clearly smaller than a Gas giant, and could be mistaken for a Moon by an unsuspecting Observer – sum1stolemyname Mar 15 '11 at 11:24
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    "That's no moon..." – Apoc326 Apr 14 '11 at 6:23

Allen Steele's book Hex describes a Dyson sphere, but made of hexagons, 1000 miles (K? I forget, but 1000 of the units) long, 100 miles wide, each as a discrete habitat.

Ya, I know Dyson spheres have been mentioned, but this is an interesting example of it. 36 Trillion biopods (each arm of each hex).

Other Dyson Sphere example might be in Roger Mcbride Allen's Hunted Earth series (alas only two books, but great ones!)


In the Perry Rhodan Multiverse we have

  1. The Loolandre is the heart of the endless armada with a diameter of at least four light years
  2. The Tiefenland is a discworld with a diameter of one light year (and a transmitter dome every light second)

How about The Stone from Greg Bear's EON. The description of it is that it was endless, bigger on the inside than the outside; a hollowed-out asteroid connected TARDIS-fashion to The Way, an cylindrical artificial space a dozen kilometers in diameter and infinite length.

In the sequel, Eternity, it is revealed that the Way is not actually infinite; it ends by opening up into a small universe (finite but unbounded). The length of the Way is difficult to calculate from the book, but since it takes the Geshels at least several thousand years of subjective time to travel it at very nearly the speed of light, a rough estimate of a billion light-years would be very conservative.


The Magog World Ship is quite big, i can't find any facts about its size, but it's a solar system with at least 11 planets..


Starting in the second season of Lexx, Mantrid created a von Neumann probe drone of his own arm. Eventually Mantrid is tricked into summoning all of the Mantrid drones, which at this point had consumed all of the matter in Mantrid's original universe, to one place.

The Mantrid drones collected all of the matter in a universe and artificially created a big crunch when Mantrid summoned them to the same location.


Isn't there a space-opera series where an (obviously) disappeared alien race literally carved a galaxy ? I even remember there are some kind of tourists visiting this galaxy.In fact, I remember, it's not a galaxy, it's a chain of stars, linked each one to the other by ... a typical Ancient Disappeared Race means. According to timday's excellent comment, it's the kiimt homeworld in Night's Dawn hyper-huge trilogy of Peter F. Hamilton.

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