All Planets Are Earth Like - Television Tropes & Idioms

Not Earth. But close enough.

"Well it's a Class M planet, so there should be Roddenberries."

—Leela foraging for food in Futurama

Qui-Gon: We're going down to the planet. What's it like?
GM: Err... Um... Earth-like?
Obi-Wan: Hmmm. Convenient.

—Darths And Droids, Episode 14

Planets in SF fall under two categories: Earth-like (solid, with a human-breathable atmosphere and the same gravity, even if completely barren), and gas giants. And often, the gas giants have Earth-like moons. Even the most inhospitable of Single Biome Planets are not immune.

Often justified by mentioning terraforming; series without terraforming invariably have ~~way too many Earth-like planets to be realistic~~ many life-bearing planets that are perhaps more similar to Earth than most would consider plausible (we don't actually know how common or uncommon they are, not having actually been out there to count them or anything). Hell, even with terraforming, there still would not be too many planets in one solar system that might be human-inhabitable without some sort of huge sunlight-focusing and gathering apparatus in orbit, since the planets' distance to the sun seems to be the main factor.

In live-action TV, this is pretty much inevitable, since creating a convincing alien planetary setting tends to require (a) a great deal of budget and F/X spent on a set that must be built very quickly and most likely will not be used again, and (b) any actors appearing in that setting to don costumes (also expensive, but more potentially reusable) which, if they are convincing full-protection envirosuits, will usually obscure the face and make acting more difficult. (See Rubber Forehead Aliens for a reverse example of that problem.) Movies, animation and novels, less bound by time and budget concerns, have a somewhat better record, but even there the ability for human characters to see, be seen, and interact with each other without significant inconvenience tends to trump realistic assessment of xenoplanetary environmental conditions.

Of course, this makes it problematic if some species wants the resources of a certain planet and are not concerned about the fate of its inhabitants. You'd think that a universe full of uninhabited planets would be a wonderful resource for metals and other minerals, but no.

Since this trope is so ubiquitous, only Lampshade Hangings, subversions and aversions ought to be listed.

Examples:

Anime

In Dragon Ball Z, Galaxy Quest and Futurama, someone steps blithely out onto the surface of an alien world without even bothering to test the atmosphere and is chastised for it.
- In Futurama, the only non-Earthlike planets shown so far are a few moons and asteroids without atmospheres, and one high-gravity (but otherwise Earthlike) planet. Even the world with three giant suns, apart from being a bit warm at full noon, was perfectly livable to humans.
Played with in Macross Frontier. The planet Gallian 4 that Alto and Sheryl go to is described as a planet tidally locked towards the sun by a gas giant neighbor, making the extremities inhospitable.
- The Vajra homeworld is a Class-A planet, virtually identical to Earth except for the three moons, and the Vajra nest/planet-sized rock formation that stretches up from gigantic pillars to form a huge ring around the equator. At the end of the series, Island 1 successfully lands on it, and the Frontier population start a new life there.
Lampshaded in the first Sound Stage of Magical Girl Lyrical Nanoha StrikerS. When the cast visits Nanoha's homeworld, her students immediately express surprise on how similar it was to Mid-Childa.

Film

It's not quite a planet, but while the belly of the gigantic space slug in The Empire Strikes Back lacks a breathable atmosphere, it apparently has normal gravity and pressure. Odd, as it's inside an asteroid in deep space.
- Star Wars does have quite a few earth-like planets, Like Alderaan, Corellia and Telos IV.
- Naboo. With *coughcough* ducks.
- We're only listing examples that are subversions, aversions, etc. here. It's obvious that Star Wars, of all universes, would have Earth-like planets seeing as many of the characters are humans.
  - At the very least the planet Felucia possess very unique looking, completely alien ecosystem. Even though it seems to suffer from similar atmosphere and gravity....
It's an aversion if the human characters have to wear space suits (or at least respirators) when on the surface, as with LV-426 in Alien.

Literature

The Robots-Empire-Foundation universe in the novels of Isaac Asimov has at least 20 million Earthlike planets inhabited by human beings, which is almost literally explained in terms of A Wizard Did It. (Actually, a Sufficiently Advanced Robot.)
- Not true. In the Robots universe, Earth terraforms and colonizes worlds, and those worlds does the same, after thousands of years no one is certain of the location of Earth.
- Plus this is galaxy wide. Even 20 million habitable planets means only an average of roughly one per 10,000 stellar systems. The galaxy is a big place.
Done to egregious extremes in the Honorverse, where the very Texas-like planet of Montana just happens to have a lot of animals that are almost exactly like real Texas animals. And everyone is a stereotypical ornery cowboy.
- It was handwaved by describing it as a planet colonised by very Texan-like people determined to preserve stereotypical ornery cowboy lifestyle.
Subverted in the Co Dominium universe. Life-bearing worlds are common, but they aren't always fully compatible with Earth life. Nonetheless, most have at least a few areas where very hardy humans can survive, albeit with high mortality rates (the poles of Frystaat and Tanith, the equator of Haven). A rare few, like Sparta, are nearly ideal for Earthlife, if slightly off in gravity and length of day. And some worlds, like New Caledonia, require extensive terraforming. The alien-inhabited Mote Prime requres respirators. The double-planet system of Franklin/New Washington requred Earth plants to be genetically altered for the red sunlight.
In the Darkover series, the titular planet itself and the hundreds of planets making of the Terran Empire.
In Larry Niven's Known Space universe, there are many planets that are liveable, but not Earthlike. Most of these were seeded with microbes as food sources by the Slaver empire, which died out billions of years ago, explaining why so many of them are biochemically cross-compatible; humans and Kzin, for example, can eat each other. Non-Earthlike worlds, such as high-gravity Jinx with its vacuum-exposed tidal "poles", and Plateau with its single liveable mountaintop sticking up out of a high-pressure toxic atmosphere, were settled by humans whose early interstellar probes were rather poorly programmed regarding what kinds of places to green-light for colonization.
- Explained somewhat because one of his books concludes Earth itself was what happened when the Slavers left a feed planet untouched for two billion years.
Played with in the Antares series: most star systems resemble Sol, with a single habitable planet. There are no named uninhabitable solid planets. However, it is implied that just like Sol, there are a number of uninhabitable solid planets in most systems - New Providence, for instance, is identified as the seventh planet in the Napier system. Presumably, the other planets are simply unimportant.
Intially avoided in Madeleine L'Engle's A Wrinkle In Time, where the characters visit in quick succession a two-dimensional planet and a planet where the air has a slightly different oxygenation level; later planets are sufficiently Earthlike for no problems to occur (and Camazotz even has earthlike trees).
Played with in the book "Anywhere But Here". The heroes, a married couple, take off for space, going to planets that are already colonized and have people and aliens living on them. However, once the navigation system on their camper truck (yes, a converted camper truck) goes haywire, they quickly end up on a series of planets that aren't on the map. There's one very short stop at a planet filled with some kind of unbreathable for humans gas. They get stranded for a few days on a planet with breathable air, but everything melts like plastic when exposed to fire, including some of the rocks, and is inedible. The local water isn't good for them either.
The Ellimist Chronicles features the interesting case of the Ketrans. Their home planet features giant floating crystals (upon which the Ketrans live) above acid oceans and an atmosphere that seems to consist mainly of hydrogen. When their home planet is invaded they flee in a newly built spacecraft to search for a new home, assuming that All Planets Are Ket Like. But, as anyone familiar with the Animorphs verse knows, the truth is that All Planets Are Earth Like, and thus inhospitable to Ketrans.

Live Action TV

Red Dwarf, mainly due to the extremely low BBC budget. Most planets in the series looked suspiciously like a park in London. Justified by three million years of terraforming.
Once, really early on, Doctor Who had its characters wear special atmosphere suits to explore an alien planet. They were never seen again. Every other alien planet ever has earth-normal gravity and atmosphere.
- It was "The Web Planet." That First Doctor serial has the distinction of being set fully in an alien galaxy, with (aside from the Doctor and his companions) a full insectoid supporting cast and environment. The Earthlings (and Gallifreyans) did not wear space suits, but at times did suffer from weakness owing to the difference in atmospheric composition.
- The early example of space-suits was "The Moonbase", and most likely did it because it was set somewhere that the viewing audience ** The early example of space-suits was "The Moonbase", and most likely did it because it was set somewhere that the viewing audience already knew didn't have a breathable atmosphere: the moon.
- It happened again in the more recent "The Impossible Planet" / "The Satan Pit".
- It was toyed with slightly in "The Daleks' Master Plan", when the Doctor was nervous about the effect of poisonous gases in the atmosphere of a city on his companions. It turned out to be an industrial city Oop North, and the gases were just then-normal levels of air pollution.
Battlestar Galactica (the new series) has had a relatively small number of Earth-like worlds actually shown for a show of its type (Caprica, Kobol, New Caprica, Tauron [in Razor], and the Algae Planet). The other 10 colonies may or may not all be Earth-like (it's possible a military base shown in a flashback was on Picon). We also have references to moons and planets from the First Cylon War that apparently have snakes and other creepy-crawlies, so we can assume they're Earth-like. However, BSG has also shown a windswept, dusty red Mars-like planet, an Ice-Moon, and a few Gas Giants. Also, the Algae Planet was originally conceived as far more primordial than the budget would have allowed for. We can speculate that whatever world the colonists originated from might have been the model by which the 13th Tribe or the other original 12 Tribes terraformed their newly settled planets, especially since only Earth-identical wildlife is ever mentioned (whether or not the humans originated on Earth or on Kobol or somewhere else altogether).
- The finale does point out that the even the colony worlds were comparatively desolate; even the comparatively lush Caprica didn't have nearly the biodiversity of Earth. Caprica goes on to note specifically that Tauron doesn't have flowers.
Star Trek The Next Generation may have had the ultimate subversion: Earth, 3.5 Billion Years Ago, just prior to the first protein being formed by two amino acids. Presumably, if not for Q's abilities, Jean Luc Picard couldn't have breathed on that surface.
- Of course, in Star Trek, the First Humanoids spread DNA to most life-bearing worlds to ensure Hollywood Evolution... er, parallel evolution. Many alien planets have been described as having the equivalent of orchids, vultures, cats, and other terrestrial-specific animals as well as Human Aliens and Rubber Forehead Aliens. The Klingons even have coffee.
- A few aversion examples: Star Trek The Original Series the planet Elba II, which had a poisonous atmosphere that would kill humans breathing it before very long, "The Way to Eden" had a planet that was technically habitable (right sunlight and air quality), but all the flora excreted a deadly acid, and the fruit was lethal; In The Wrath Of Khan, the planet Khan was found on had been Earth-like but is fairly toxic now; Star Trek Voyager had the "Y-class" planet in the episode "Demon".
- And frequently enough in all Star Treks, "only" one or two planets in a system will be "Class M" (that is, Earthlike.) The existence of non-Earthlike planets is never in question... there's just never any point in landing on one. Except, of course, in cases in which a planet that's nearly Earthlike that can support the away team with the busted shuttlecraft for only a while becomes the setting of a story, that is. The crew never beam to or land on a planet without checking its conditions (or without sufficient time for it to have been done offscreen having passed.) However, it is a striking coincidence that the planet a shuttlecraft crashes on almost always happens to be class M.
- In episode of Enterprise, Tucker crash lands on a small planet that is habitable while it is night time. Once the planet rotates to face the sun, it is uninhabitable for human life, as it is too hot.
Most of the planets in Stargate SG-1 are fairly Earth-like, though there are some exceptions where the team has to wear special space suits to explore them. This is explained as the Goa'uld (and before them, the Ancients) having terraformed the planets millenia in the past.
- And let's face it, why would you place a pedestrian-accessible Stargate on a planet that wasn't amenable to humanoid life?
  - Why would you place a pedestrian-accessible stargate in orbit? Ask the Ancients.
  - It was the Wraith's doing. We surround our cattle with electric fence. The Wraith's cattle is a bit more intelligent.
- And then, there are those examples where Planets are absurdly present-day Earth-like to the point where Ikea furniture would fit right in. Particularly common in later seasons and "Atlantis".
- This is actually Justified in both, though less in Atlantis. All missions in SG1 are preceded by sending a MALP robot first. We only rarely see situations where the team enters a planet lacking either an atmosphere or a DHD (though we do see both, at different times). In Atlantis, more recent seasons have the IOA demanding MALPs be sent ahead. Previously, though, many if not most missions were initially sent using the convenience of a Puddle Jumper, which allows breathing because it's a spaceship, and dialing because it has its own DHD. Remember, in Atlantis most of those gates DON'T have an earth-like planet on the other side... most of them have space on the other side.
  - In either case, Stargates aren't naturally occuring phenomena, so the Ancients would tend to place them only near places interesting enough to merit visiting.
  - Repeatedly visting or actually living there. The Stargate system doesn't make sense for one-off or very occasional visits. A near-instantaneous interplanetary mass-transit system only makes sense for worlds that you are visting on a regular basis. It's likely that many, if not most of these planets, at least in the Milky Way, were inhabited by the Alterans at some point. Otherwise what would be the point of terraforming them?
  - Stargate Universe shows that the gates in the Pegasus Galaxy were seeded by unmanned ships well in advance of the Ancients settling. The criteria was apparently set for "could be useful," so even the Ancients may not have visited all of the seeded planets. This would explain why the planet of the living crystal, Lotus Eater Machine-generating creatures had a gate, when it would have been child's play for the Ancients to remove it from such a dangerous world.
Likewise, all the inhabited worlds in Firefly were deliberately terraformed, though they each have their little quirks.
Sliders, which dealt with Earths in parallel universes, mentioned once or twice that the nature of the wormhole would keep it from dropping the heroes in universes that were patently incompatible with human life. Or inside rocks.

Tabletop RPG

GURPS Space arguably goes too far in the other direction. Enough that the fourth edition had you deciding whether you wanted an Earthlike planet to start with and then designing the physical characteristics with that in mind. The main alternatives being Gas Giant, rocky moon/asteroid, ice moon, or toxic terrestrial.
Justified in the Traveller RPG, where Earth life (including Transplanted Humans and Uplifted canines) were spread by the Ancients.
In Battle Tech, 'Earthlike' is variable. No planet is exactly like Earth in terms of comfort for humans, which is commented on by those who are lucky enough actually travel there. Most of the settled worlds are fairly close, though there are wild exceptions, like the domed cities of Sirius V (the atmosphere is poisonous), or the Lyran capital world of Tharkad, which is in a total ice age, with even the equator iced over.
- Strange that they haven't tried to warm it up. It's not all that difficult for an advanced starfaring society to end an ice age, if they really want to.
- The Successor States may not have quite literally succeeded in bombing each other back to the Stone Age by the beginning of the 31st century, but they were getting close enough. You're no longer an 'advanced' starfaring society if all the faster-than-light vessels you have are leftovers from the time when people still knew how to build those...
- It's not that difficult for even the most basic spacefaring society to warm up a planet if they're already living on it. Spread a little soot on the ice caps to diminish their reflectivity, pump out some super-greenhouse gases - and pretty soon you have your result.
Not exactly an RPG, but Warhammer40000 averts this trope pretty impressively. The Imperium of Man classifies planets into several different categories, some of which are Earthlike. Even within a category there is enough variation that most planets aren't a SingleBiomePlanet.
- And being the kind of universe it is, most of the settled planets are not, in fact, habitable. The Imperium seems to absolutely love settling worlds that humans can't actually expect to survive on.
- Special note: Earth itself is a giant planet city that had been seriously messed up several times in the past. It is doubtful that Earth itself could be qualified as "Earth-like".

Video Games

In the old Star Trek game for the NES, players could technically only land on planets with breathable atmospheres, but all that it actually meant is that the designers only made planets with oxygenated atmospheres. The rest are just there as a backdrop.
Freelancer has roughly a 50/50 ratio of Earth-like planets and somehow uninhabitable worlds. On one hand, you have planets such as Cambridge or Stuttgart, full of fertile farmlands, or Curaçao, a planet full of heavenly beaches; but on the other hand, you also have planets like Pittsburgh, a barren, deserted wasteland punctuated with mines, or California Minor, a little frozen ball under terraforming.
- Most of these planets are covered in rocky pine forests.
In the Homeworld series, while Hiigara falls under this trope, Kharak is only partly habitable, being a harsh desert planet that only the poles are comfortably habitable, while maintaining .98g gravity and breathable atmosphere. Justified in the fact that since the original Hiigarans were exiled there, the planet must've been chosen specifically as being harsh, but not too inhospitable.
Mass Effect notably averts this; the vast majority of the planets encountered are actually very hostile to human (or most) lifeforms. This makes those inhabitable worlds that can be found all the more valuable.
- "Vast majority" here meaning that only three planets are safe for humans, in a game that spans a third of the galaxy. Most of the planets you visit require spacesuits and sealed environments for survival, and sometimes not even your Powered Armor/space suit will keep you alive for very long. The 80%+ of planets you don't visit are often even more inhospitable.
- A few planets actually are more like subversions, too. Like the planet with a much higher oxygen concentration than Earth's. It's enough for humans to feel plenty comfortable, like being in a hyperbaric chamber...but it makes thunderstorms absolutely devastating to anything they catch in their path, and vegetation goes up like tinder in amounts that make the California wildfires look like campfires.
  - Not to mention huge insects and plants that give off pollen that causes death by allergy in seconds.
Space Quest III sort of averts this with the Planet Ortega, which while the atmosphere is breathable, the surface is too hot for humans who don't have special clothes.
Averted in the Master of Orion series. Terran class planets exist, but so does Toxic, Desert, Ocean, Tundra etc. etc. Terraforming can help make them more habitable.
Star Craft is pretty guilty of this. Although a wide variety of planet types exists, all of them that appear in the novels have breathable atmospheres (with one exception). It's hard to tell ingame since all terran units use spacesuits regardless of the circumstances anyway, but there is no mention of human colonies on planets that aren't rather earth-like.
- Couldn't say much with regards to the novels, but most of the planets with Terran settlements might be Earth-like because those are the ones the Terrans would bother to settle on.
War Craft only has two explicity known planets, Azeroth and Draenor, both of which are very earth-like. However, Draenor was ripped apart by magical experiments and drained of it's life by demonic influence, which makes it a very alien place... with the exception of Nagrand, which somehow remained untouched. What else if left of the planet still qualifies as earth-like as far as certain criterias are concerned. Life is still possible (even though half of the zones have no water or any plantlife other than herbs).
The Lunarian Moon (no, that's not redundant) in Final Fantasy IV has a perfectly breathable atmosphere and its gravity is identical to the heroes' homeworld. Just ignore the man-sized viruses and the killer flans.
Invoked in Ultima Underworld II, when Iolo expresses concern that one of the facets of the gem might transport you to a planet of poisonous gas or an ocean floor. He's clearly not very Genre Savvy.

Web Comics

Darths And Droids tries to explain this trope as applied to Star Wars. When unexpectedly asked about what Naboo is like, the Game Master automatically responds: "Um... Earth-like?", and the players notice that it's "convenient". Later, when they approach Tatooine, they ask the GM if it's "conveniently Earth-like again", and he hastily assures them that it's a planet-wide desert. Only, for the purposes of this trope, it's still Earth-like enough.
- "So it's Mad Max World?"
- Later subverted somewhat with Naboo, as well, as they figure out that, while it may have an Earth-like surface, its geology would have to be radically different from ours for some of the things they do in the game to be possible.
In the "GOFOTRON" arc of Sluggy Freelance, the cast visits the Punyverse, Another Dimension consisting of about one hundred planets, all but a few of them inhabited, and packed together within easy traveling distance. The strip actually addresses the oddness of this, with Riff saying, "I've never seen a universe so ... deliberate." Later justified when it's revealed that the Punyverse did not evolve naturally, but was actually created for an alien science project.
Earthsong justifies this one fairly well - all the aliens encountered are from Earthlike planets for the simple reason that planets must make themselves Earthlike before they are given the secret of supporting life.
This Irregular Webcomic strip demonstrates what will happen if this trope didn't exist.
Man, this is the hundredth tide-locked airless rockball orbiting an M-dwarf we've found in a row!
You forgot that system with the uninhabitable gas giant with no interesting features whatsoever.

Western Animation

In the 90's X-Men cartoon, a passing Shiar ship was bored that they had to map out a section of the universe filled with uninhabited worlds. This was the section that Dark Phoenix fried. Note, this is more of a case of softening her Face Heel Turn, as in the original comics she did destroy inhabited worlds; and some people consider that unforgivable.
Phineas And Ferb is especially odd—-even Mars is Earth-like enough for the human characters to survive, not to mention an asteroid that had air and normal Earthly gravity. Of course, the latter had a milkshake bar on it, so presumably the aliens terraformed it in some way. (It Makes Sense In Context. Sort of.)

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