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Baby Planet

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An inhabitable planet that is far smaller than astronomically possible, often less than a few functional miles in diameter. As a general rule, a Baby Planet is small enough that you can see its curvature even on the surface. In Real Life, a body this small would be called an asteroid or be a natural satellite orbiting a planet, and would usually be incapable of supporting an atmosphere (or rather, an atmosphere with enough pressure and warmth to support life), and would probably not even be spherical. But in fiction, these often sport an entire ecosystem awkwardly compressed into the minute available space.

Although Sci-Fi Writers Have No Sense of Scale, they usually aren't this far off the mark on accident; this trope usually comes about either because of limitations in technology's ability to represent planets in a realistic scale or just for the sake of aesthetic.

Often, this is used for purely aesthetic reasons, particularly on cover art for games and CDs. Just as often it's Art Major Physics. In photography, this effect is often created with very-wide angle (or fisheye) lenses.

Bonus points if it's unusually shaped too.

Related to Floating Continent. Not to be confused with LittleBigPlanet, It's a Small World After All or Planetville.



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  • In the UK, British Gas have been running a series of rather fun adverts based on the idea that "your home is your world"; the person whose boiler is up the plonk lives on a tiny planet that is their house, drive, and garden!! And their cars and vans take them to other planets and some planets have theme parks... sounds like a cross between The Sims and Super Mario Galaxy in advert form. Some of them are gathered here.

    Anime and Manga 
  • King Kai's planet in Dragon Ball Z. Despite being maybe fifty feet in diameter, it strangely has ten times earth's gravity. Based on King Kai's vague explanation, it apparently has the same mass as Earth, heavily compressed. This should technically make it a neutron star, but then, nobody ever accused Dragon Ball Z of realism. Even if they did, it's still the self-built home of a Physical God, and still set up in a corner of the afterlife, so it might as well be decorated with "A Wizard Did It" in 50-foot-high neon any way the audience looks at it. Dragon Ball Z: Battle of Gods explains that King Kai's planet was once larger, possibly realistically so, until Beerus destroyed most of it in retaliation for losing a game of Hide and Seek. This doesn't explain how it continues to be a planet now, of course.
  • An episode of Sgt. Frog had one of Keroro's last-ditch invasion schemes involve stealing garbage and water from Earth to create a mini-planet. We learn it was a "last-ditch" scheme because unauthorized planet creation is against the law, and when the planet creation goes out of control, it nearly becomes big enough to qualify as a full planet, leading to the Keronians nearly getting arrested by Space Police officer Poyon.
  • In Goodnight Punpun, Punpun dreams up a small meteor that fits the bill, which he names Punpunia. It's really only big enough for his house, family, and a few stray animals.
  • Mildian in EDENS ZERO is a very tiny planet with a noticeable curvature from ground level, enough to make the main characters confident that the first building they come across on the planet is probably the only one.

    Comic Books 
  • A Silver Age Superboy story had Clark Kent travel to a small asteroid/planet, where he found someone with powers similar to his own. At the time, the preferred explanation for Superman's powers was that Krypton was larger than Earth, so the native race evolved to counteract the more powerful gravity. The boy on the asteroid, it turned out, was from Earth, so on his little world, he got to have some of the same benefits Superboy did. The native races of all 3 ecosystems evolved to be identical in size and shape...
  • Carl Barks' Uncle Scrooge comic "Island in the Sky" features a couple of asteroids that are somehow capable of supporting life. They also orbit each other closely enough to share an atmosphere.
  • The Dutch comic Storm has this as a common sight in the solar system the later albums are set in.

  • The CGI shots of the Earth in Zombieland (which are apparently the mental images of the narrator).
  • The movie Timelock is set on a prison asteroid. It is at least established to be very cold outside (and the worst offenders are hung outside in a state of suspended animation). Then the movie goes and violates its own logic at the end when Riley sticks three small nuclear devices on Villum and knocks him into an abyss. Villum is shown alive and well in the very last minute of the movie.
  • Mongo's moons in Flash Gordon. The ones we see aren't round, Arboria is bowl-shaped with everything on "top" of it and the Hawk Men live in a flying fortress.
  • Exaggerated in Men in Black, as the plot centers around a galaxy small enough to fit in the bauble of a cat's collar.
  • Ego the Living Planet in Guardians of the Galaxy Vol. 2 is the size of Earth's moon with Earthlike air and gravity.

  • "Asteroid B-612" from Antoine de Saint-Exupery's The Little Prince may be the Trope Codifier, if not the Trope Maker. It's house-sized, which makes it bigger than most neighboring planets. And he keeps encountering new stuff on it every day, including baobab trees.
  • Justified in Larry Niven's Protector due to the use of gravity generators, etc.
  • Played straight and justified in the novel The Collapsium by Wil McCarthy: one of the main characters lives on an artificially constructed planet which is only a few hundred kilometers wide. It has a core made out of degenerate matter in the form of neutronium which gives it Earth-normal gravity, holds it in a spherical shape, and allows it to retain an atmosphere.
  • The Mushroom Planet in the eponymous novels.
  • The Fredric Brown story Placet is a Crazy Place features a tiny planet with a breathable atmosphere with a core made of extra-dense 'heavy' matter to give it its shape and gravity. It even has life forms made of heavy matter that "fly" through the crust (which is like air to them since they are so dense), causing earthquakes. It obviously suffers from the "what keeps the heavy matter from expanding" problem, but might be excused since it is a story from the 40s and Science Marches On. Also, the heavy matter "birds" that cause earthquakes are completely 100% excused by the Rule of Funny; the buildings on Placet are small and light, and never last more than three weeks. The birds fly right through the foundations.
  • In Jack Vance's short story "We'll Build Your Dream Castle", retreats for the super-rich are built on a few dozen chunks of super-dense matter in orbit near Earth.
  • Gary Gibson's Stealing Light has at least one asteroid fitted with a Shoal 'world engine', and their Coreships.
  • In The Light Fantastic, the great world turtle Great A'Tuin ushers eight eggs into the world, each hatching to reveal a perfectly formed baby turtle, each supporting on its back a group of elephant calves which on their back support a proto-Discworld. These then swim from the shores of harsh reality back into the depths of the improbable part of the universe that supports such things.
  • The backstory of House of Suns features a planetoid that held the Gentian household in the distant past. It had standard Earth gravity which was hinted to be due to a small black hole contained within the planetoid.
  • ''The New World Of Mr Tompkins: Justified with a Baby Universe where the gravitational constant is enormous. Inverted in Relativity Land, which should be a black hole if gravity still works the same despite the speed of light being 30 mph or less.
  • Lorien Legacies: Lorien is one-tenth the size of Earth and Mogadore one fifth.
  • N. K. Jemisin's Inheritance Trilogy: The Trickster God Sieh has a collection of stars and planets the size of toy balls, some of which like to follow him around. Their real nature is ambiguous until the third book, when he puts some of them back in space, undoes the spell keeping them miniaturized, and proves that the "Stole the sun for a prank" Playground Song about him is Not Hyperbole.

    Live-Action TV 
  • Several episodes of The Twilight Zone TOS had asteroids with normal Earth gravity and a breathable atmosphere.
    • Played straight in "The Lonely"
    • Lampshaded in "Elegy". The astronauts specifically mention that an asteroid shouldn't have Earth gravity and atmosphere.
    • Subverted in "I Shot An Arrow Into The Air". Some shipwrecked astronauts think they're on such an asteroid: they're actually on Earth!
  • Lexx:
    • Season 2 had something like this, a small planetoid with an artificial atmosphere that was a TV studio center. Our 'heroes' wind up there and find that if their ratings slide they'll be in trouble.
    • In one episode, a planetoid was so small you could see grazing sheep on its surface from orbit. For unexplained reasons, it had Earthlike gravity.
  • Aversion: In the original Star Trek episode "That Which Survives" the fact that a Luna-sized world has Earthlike atmosphere is one of the clues that something's amiss.
  • The official atlas for the Firefly verse says even the small moons, barely large enough to be balls (think Mimas or Enceladus), are terraformed using gravitic technology.

  • Yes:
    • Album cover art: The miniature planet on the cover of Fragile by Yes. (On the back cover, the planet breaks up and the population escape in a wooden space glider. This later inspired Jon Anderson's solo album Olias of Sunhillow.)
    • The band's later album "Yessongs" shows the glider guiding a fragment of the baby planet through space, where it lands in the ocean of a new, full-size world.
  • The zoom out at the end of the music video for Björk's "Human Behavior" reveals the story to be set on a tiny planet.

  • Molag spends most of Firebringer walking in a straight line, trying to reach the edge of the world. By the end of the play (which doesn't seem to be more than a few days or weeks), she's gone all the way around the world and come back to the tribe.

    Video Games 
  • Space Engineers finds itself somewhere in between. Planets are massive; their curvature is only visible from tens of thousands of meters up, but they're still small enough that the developers had to add special code to flatten out the terrain when at a distance so they actually look round. There are actual asteroids, which are fittingly atmosphere-less and gravity-less, but are unreasonably tiny, frequently no more than a few dozen meters in diameter.
  • Spore. The planets look regular-sized from close but appear increasingly tiny as you advance towards the Space Stage. To give you an idea of scale: You can find Earth. The UK is about the size of an average spaceship.
  • Kingdom Hearts. One of the unique artistic features in the first game was condensing of most of the Disney worlds into miniature planets, most of which could be seen from 'space'. The worlds themselves, while modeled after the various Disney worlds, tend to be as small as possible, no more than a few miles each. The residents don't seem to notice.
  • Super Mario Bros.:
    • Super Mario Galaxy not only has baby planets; it has baby galaxies. As in, galaxies that're not much bigger than a large paddock. And with several galaxies, you can look off into the distance and see a single planet bigger than the entire galaxy.
    • And don't forget the Lumas, who transform into these miniature planets and galaxies when they mature, making them literally baby planets.
  • Sonic the Hedgehog:
    • Sonic CD takes place on the appropriately named Little Planet, which appears in the sky once a year. It reappears in Sonic the Hedgehog 4.
    • The Special Stages of Sonic 3 & Knuckles.
    • In Sonic Adventure 2, Rouge has a large stage called Mad Space, which features tiny planetoids similar to those later seen in the Super Mario Galaxy series. They pull Rouge into their gravitational field if she jump or glides too close. One of them is cylindrical in shape.
  • The cover of SimCity Societies.
  • The Prince Planet in Katamari Damacy (very obviously based on The Little Prince's) as well as Earth itself if you get big enough to notice the curvature.
  • The cover of Animal Crossing: Wild World, and in addition, in-game the ground curves downward into the distance.
  • The freeware game Frozzd features dozens of such planets.
  • The American cover art for Bullfrog's Theme Park game.
  • In Yoshi's Island, you fight Raphael the Raven on one of these. To be clear, it is the world's moon.
  • Spacebuild maps for Garry's Mod have very small planets generally no bigger than about the size of a football field, though largely due to the Source engine's max map size capping out under 1 kilometer^3.
  • Albion. The titular planet is considerably smaller than Earth but is mostly made up of exceptionally heavy metal, making the planet's mass just slightly smaller than Earth's.
  • Angry Birds Space features many levels with small planetoids that have gravity bubbles that affect the birds' trajectories.
  • Planets in Planetary Annihilation range between this and more reasonable sizes, depending on the settings used. Nevertheless, they're much closer than would really be possible, in order that interplanetary travel doesn't take ages.
  • Incoboto Mini has the main character running across several small planets as part of the gameplay.
  • One of your party members in Anachronox is an entire miniaturized planet, Democratus. This is however not it's natural state, when first encountered it is normal size and also has to return to normal size in an emergency in a late section of the plot, scattering the rest of the party across the surface and sending them on short solo adventures.
  • The planet Auraxis in PlanetSide 1 has a tiny surface area, less than 1000 km^2, along with a thin atmosphere which cannot sustain air-breathing engines past 400m above sea level. Being heavily infused with Ancient Vanu technology, it has been theorized that the planet has a black hole in its core to provide gravity. The sequel has the same issue of tiny scale - in fact, it's even smaller - but almost triples the flight ceiling.
  • This is downplayed in Rodina. The asteroids are too small to support atmospheres, but they do have enough gravity for you to walk on without floating into space.
  • Kerbal Space Program and its various analogues for various real-life Solar System bodies are scaled down from reality by a factor of ten. They still have approximately the same gravity, however, meaning either the planets are denser than any known substance, or that the Kerbal-verse has an increased constant of gravitation. Kerbin in particular, despite being only 600km in radius, still manages a very Earth-like 9.81 meters per second per second and a life-supporting atmosphere. For those that want additional challenge, Real Solar System scales the planets, moons, and star back up to real-world sizes.
  • Germination Both the campaign and endless mode take place on a planet the size of a large yard.
  • Deiland: This survival/crafting game takes place on a planet which has a diameter of about 60 feet/20 metres. It has an Earth-like gravity and atmosphere and a temperate climate. Population: one.
  • Populous: The Beginning: each level of the game takes place in a different small planet, which all form part of a small solar system. Though some of them seem to actually be moons, as they are orbiting around another of the planets (which isn't significantly bigger than them).
  • Grow
    • Grow RPG takes place on a tiny planet that the hero can explore in less than 5 minutes.
    • The red ball from Grow Ver 3 could count as one since every item and creatures are attracted by its gravitational center, even though the red ball itself is placed on a gray ground.
    • If you are on the right path of Grow Ver 1 you make a little planet.
    • In Grow Island you need a rocket-ship to pick up a blue potion on a planet that's even smaller than the examples above.
  • Aether: It takes about 12 seconds to traverse the circumference of most of the planets. The moons are even smaller.
  • Outer Wilds takes place in a baby solar system, with planets as small as 500 meters across separated by a few kilometers of empty space between them.
  • Exaggerated in The Binding of Isaac: Rebirth with the Tiny Planet item, which consists of a baseball-sized planetoid embedded in Isaac's head. It even has its own gravitational field, making every tear Isaac shoots orbit him.

    Web Animation 

  • Awkward Zombie: One strip shows why it would suck to live on one of these. When your planet is the size of a cottage and your food supplies consist of a single coconut, it's really easy for your ecosystem to be wrecked by a passing plumber deciding to use your planet's entire food supply as ammunition.
  • In The Inexplicable Adventures of Bob!, the planetoid of Fleen follows this trope, even to the point of depicting The Little Prince's asteroid floating nearby.
  • Homestuck: Prospit and Derse. If the size of the towers on their respective moons is any indication, they are smaller than a Death Star, though still quite big. This ultimately applies to almost every planet in the Incipisphere; the players' Lands are likely less than a hundred kilometers in diameter, small enough that at a fairly distant view the players' homes are still visible, giant tower status notwithstanding. Skaia and The Battlefield within it are large but still fairly small for a planet.
  • In Nedroid, Reginald once demonstrated how small the planet Mercury was by holding his hand up, reaching out with his other, and giving himself a high five. He later ate part of Pluto.

    Web Original 
  • Discussed on this issue of the What If? Blog, mostly with regard to what the gravitational effects of such a world would be, if it could exist.
  • SCP Foundation: SCP-756 is this trope up to eleven, with an entire solar system fitting inside a room.

    Western Animation 
  • Futurama:
    • Briefly alluded to in an episode where a planet implodes, leaving behind something the size of a large boulder with a few of its native animals pathetically hanging on. As far as the cast is concerned, this is an acceptable level of survival for them.
    • "The Mutants Are Revolting" has Lady Astor's asteroid. It's got both an atmosphere and normal gravity, yet it's so small that when Bender backs up to take a running leap over a canyon, he accidentally walks past Lady Astor's mansion and over a rickety rope bridge without realizing it. Twice.
    • Inverted in the Futurama game, when the Sun seems to have Earth gravity...and is a lava planet.
    • "Fear of a Bot Planet" has Fry remarking on how small entire planets can appear when you're flying through space, at which point a Saturn-like planet that appeared to be off in the distance is revealed to actually be about the size of a large bug when it hits the ship's windshield like one.
  • The Clangers' The Clanger Planet. It has vaguely moonlike craters, and in one episode a Lunar Module lands and an astronaut plants a flag (which the Clangers adopt as a tablecloth,) but it's referred to by the narrator as a "star" and exists among other similar worldlets. But since the Clangers occasionally leave it for the space above without any breathing problems, it runs strictly on Cartoon Physics.
  • The Transformers: Generation 1 portrayal of Cybertron. Curvature could often be seen, and buildings could be seen from space. When Cybertron was moved into Earth's orbit, it was shown to be smaller than the moon - close enough for a plane-bot to fly to in under a minute, and yet the entire planet could be easily seen whenever it was in frame. Asteroid-sized is generous, and yet it's shown to have gravity comparable to Earth.
  • In Duck Dodgers in the 24½th Century, Planet X gets reduced down to a rock that's barely large enough for Dodgers and Marvin the Martian to both stand on. Nonetheless, it still has air and some weird kind of gravity that allows someone to fall off.
    Duck Dodgers: As I was saying, buster, this planet ain't big enough for the two of us, so off you go! (pushes Marvin off) Now, this planet is hereby claimed in the name of Earth by Duck Dodgers in the Twenty-Fourth-and-a-Half Century!
    Cadet: A-a-a-a-big deal.
  • All the planets in Tiny Planets; in the episode "Gone with the Wind", the protagonists find the path to their goal blocked, and solve the problem by going all the way around the planet and approaching it from the far side. Taking it up a notch, the title sequence shows a trio of aliens living on an asteroid not much larger than themselves.
  • All the planets in Wander over Yonder are small enough for buildings, mountains, and other features around that size area to be visible from space.
  • Rick and Morty: Dwarf Terrace 9 from the season 2 finale, which the family hides out on from the Galactic Federation. It's small enough that Morty can throw a frisbee across the surface and catch it from the other side with some practice, and its circumference is about the size of a normal neighborhood.
  • Some planets in Bounty Hamster are small enough that a reasonably fast ground vehicle can generally go around one in about ten seconds.

    Real Life 
  • Neutron stars are stellar remnants that pack 1-2 solar masses into a nearly-perfect sphere around 10 kilometers across. Their gravitational pull, about 200 billion times stronger at their surface than on Earth, is stronger than anything except a black hole.
  • Polar panorama photos look very much like tiny planets and can be made from any panorama photo, such as a cityscape.


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