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{{trope}}
[[File:250px-Alderaan.jpg|link=Star Wars|
'''Obi-Wan''': ''Hmmm. Convenient.''
That SF trope where planets fall into 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 Planet
▲{{quote|'''Qui-Gon''': ''We're going down to the planet. What's it like?''<br />
▲'''GM''': Err... ''Um... Earth-like?''<br />
▲'''Obi-Wan''': ''Hmmm. Convenient.''|''[[Darths and Droids]]'', [http://www.darthsanddroids.net/episodes/0014.html Episode 14]}}
▲That SF trope where planets fall into 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 Planet|Single Biome Planets]] are not immune.
There is, of course, a certain subjectivity regarding the definition of "Earth-like". In some works, "Earth-like" means that a human being can walk around without a pressure suit and not die, but everything else (the presence of animals and plants, the weather, the gravity, and so on) might be vastly different. In other works, "Earth-like" means not only are pressure suits unnecessary, but a person can eat the plants and animals, drink the water, walk around in the gravity without a lot of effort, survive the weather, and so on.
Often [[Justified Trope|justified]] by mentioning [[
In live-action TV, this is [[Acceptable Breaks From Reality|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 [[Shoot the Money|potentially reusable]]) which, if they are convincing full-protection envirosuits, will usually [[In Space Everyone Can See Your Face|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.
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Since this trope is [[Universal Tropes|so ubiquitous]], only [[Lampshaded|Lampshade Hangings]], [[Subverted Trope|subversions]] and [[Averted Trope|aversions]] ought to be listed.
{{examples|Examples:}}▼
== [[Anime]] and [[Manga]] ==
* In ''[[Dragonball Z]]'', someone steps blithely out onto the surface of an alien world without even bothering to test the atmosphere and is chastised for it.
** Well, in fairness, those someones tend to be Saiyans, half-Saiyans, a Namek, androids and so on- Krillin is the only human. Pretty much all the main characters possess an array of superpowers too. And they only spend a prolonged time two alien worlds anyway- Namek (which, since there is at least two Namekians living on Earth, presumably has a similar atmosphere) and King Kais planet, which has some connection to the Afterlife, so atmosphere shouldn't really be a problem.
* Played with in ''[[Macross Frontier]]''. The planet Gallian 4 that Alto and Sheryl go to is described as a planet [[Did Not Do the Research|tidally locked towards the sun by a gas giant neighbor]], making the extremities inhospitable.
** The {{spoiler|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.}}
* [[Lampshade Hanging|Lampshaded]] in the first [[All There in the Manual|Sound Stage]] of ''[[Magical Girl Lyrical Nanoha
* ''[[
* The world of ''[[
== [[Fan Works]] ==
* Invoked right at the start of ''[[
==
▲* Invoked right at the start of ''[[With Strings Attached (Fanfic)|With Strings Attached]]''. After Varx offers to whisk Paul to another planet for adventure, Paul (who thinks he's dreaming) jokingly worries that he might be dropped on the Moon or some other inhospitable place. Varx assures him that they have an oxygen planet all picked out. Later, when the four go on the Vasyn quest, the three planets they visit are very Earthlike (one of them being an actual parallel Earth) {{spoiler|but again, these were all picked out for them}}.
* It's not most definitely not a normal 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''. Maybe the Millennium Falcon was able to extend its artificial gravity field or the asteroid field as a whole had some kind of atmosphere.
** At the very least the planet Felucia possessed very unique looking, completely alien ecosystem. Even though it seems to suffer from similar atmosphere and gravity....
*** Likewise Mustafar, though distinctly non-terestrial in its appearance, has a perfectly breathable atmosphere despite the fact that it is ''completely covered with active volcanoes and lava rivers''. Seriously, not one person coughs in the Mustafar scenes.
* 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 (
* And in ''[[Avatar (
** The low gravity is also why everything is so much ''bigger'' on Pandora; it can afford to be, on account of the lower gravity.
* Averted in ''[[Rocketship X-M]]'', ironically enough given the movies' massive [[Hollywood Science]]. Scenes on Mars were filmed in California's Death Valley, which NASA latter used to test equipment due to be used on [[The Red Planet]] because of its similarity.
* [[Lampshade Hanging|Lampshaded]] in ''[[
== [[Literature]] ==
* [[Older Than Feudalism]]: This showed up in the world's first space-travel story, ''[[
* 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 Aliens|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.
** [[Justified Trope|Justified]] in a conversation between two of the characters in one of the later Foundation books. One of them [[Lampshade Hanging|mentioned how all inhabited planets are more or less the same,]] and the other replied, of course they are. If a planet wasn't comfortable enough for for people to want to live on, it wouldn't have been colonized.
* Done to extremes in the ''[[Honor Harrington
** It was [[Hand Wave|handwaved]] by describing it as a planet colonised by very Texan-like people determined to preserve stereotypical ornery cowboy lifestyle.
* Subverted in the ''[[
* 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 [[No Biochemical Barriers|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 livable mountaintop sticking up out of a high-pressure toxic atmosphere, were settled by humans whose early interstellar probes were [[Literal Genie|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 [[The Law of Conservation of Detail|simply unimportant]].
* Initially avoided in [[Madeleine L
* 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.
* ''[[Animorphs
* Played straight in [[H. Beam Piper]]'s ''[[Little Fuzzy]]'' series, with the extremely Earth-like planet Zarathustra. Subverted in his work ''[[Uller Uprising]]'', with the planets Uller (Breathable air and tolerable gravity, but silicon-based native life) and [[Meaningful Name|Nifflheim]] (hideously poisonous mining planet).
* Subverted by just about everything by Hal Clement, who would go to great lengths to invent non-terrestrial planets and populate them with believable life forms.
* Also subverted by Robert Forward in his novel Dragon's Egg. The planet in question is a ball of neutronium, the aliens are amoebas, and you STILL empathize with them.
* Averted in [[Peter F. Hamilton]]'s ''[[
** This is demonstrated in the first book, ''[[
** Hamilton's ''other'' big book series, the [[Nights Dawn|Night's Dawn Trilogy]], averts this trope as well, with habitable planets being classed as "Terracompatible".
* ''Fallen Dragon'', by [[Peter F. Hamilton]], averts this trope as well. Pretty much ''no'' planet is completely suited for human life. For all of them, extensive terraforming is required before sending in the colonists. Amethi was a frozen world with very little atmosphere when the first settlers came, and a scene depicts the startled reactions of a bunch of children who see ''a cloud'' for the first time. On Thallspring the soil bacteria and other biota make it necessary for the [[Mega Corp]] running the colonization efforts to clear out all life in large swaths of land via periodic [[Death From Above|orbital]] [[Death Ray|gamma laser]] "soaks", in preparation for colony expansion. The process is stated to kill all bacteria down to a few meters underground. Santa Chico has a ''very'' high oxygen content, and its biosphere is a biochemical and medical ''goldmine'', which is why the colonists modified ''themselves'' to adapt and eventually began using [[Organic Technology]], only to revert to a agrarian society of [[Body Horror|bizarre]] xenophobic [[Furry Fandom|Furries]] once they grew bored with the [[Mega Corp
* Averted in [[Alastair Reynolds]]'s ''Revelation Space'' universe. Most planets are barely habitable and human inhabitants require bases with constant life support to survive. The only planets with breathable atmospheres tend to be the Juggler waterworlds, which have oxygen atmospheres. By far the only really Earth-like planet is Sky's Edge, which has a breathable atmosphere and didn't even require much [[
* Present, after a fashion, in much of Murray Leinster's work. In one of the Med Ship stories, the author notes that though non-Terrestrial ecologies are rarely strongly similar to Earth, they tend to be broadly similar, with grass-like plants, tree-like plants, pollinating flying creatures, prey species, predator species, scavengers of various sorts, etc. Most non-Terrestial ecosystems are somewhat compatible with Earth life, which can keep the Med Service very busy.
* Taken to extremes in Heinlein's ''Tunnel in the Sky'', in which the planet on which Rob is stranded is ''so'' Earth-
* ''[[
▲== Live Action TV ==
* Once, really early on, ''[[
▲* ''[[Red Dwarf (TV)|Red Dwarf]]'', mainly due to the extremely low BBC budget. Most planets in the series looked [[BBC Quarry|suspiciously like a park in London]]. Justified by [[Sci Fi Writers Have No Sense of Scale|three million years]] of [[Terraform|terraforming]].
▲* Once, really early on, ''[[Doctor Who (TV)|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. This is usually [[Justified Trope|justified]] by the fact that either the Doctor or the the TARDIS (at least according to [[Doctor Who (TV)/Recap/S32 E4 The Doctors Wife|The Doctor's Wife]]) are in control of where they go.
** 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 already knew didn't have a breathable atmosphere: the moon.
** It happened again in the more recent "The Impossible Planet" / "The Satan Pit", and with "The Waters of Mars", where again the setting wasn't a fictional blank slate.
** 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.
** In "Midnight," the title planet ''is'' totally unlivable ( {{spoiler|except it turns out it isn't, but that's beside the point}}); it's apparently one big lump of crystal with no atmosphere and a star that emits ''very'' deadly rays. But Professor Hobbes goes on about this like it's remarkable for a star system NOT to support life.
* ''[[Battlestar Galactica
** Calling New Caprica "Earthlike" is a ''huge'' strech. Yes the flora, when exists, ''is'' earth-like but the Colonials were freezing their asses off while living ''on the equatorial belt''. And that was the only habitable part of that damn planet.
** 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.
** Now "The Plan" has shown several other planets in the 12 colonies: every one shown was Earth-like to some degree, but some may have been [[Single Biome Planet
* ''[[Star Trek:
** Of course, in [[
** A few aversion examples: ''[[Star Trek:
*** There are also two episodes where the reason for the crew to look closer is that the planet, or an area on it, is Earth-like when it shouldn't be ([[Sufficiently Advanced Aliens]] did it).
** And frequently enough in all Star Treks, "only" one or two planets in a system will be "Class M" (that is, Earthlike) and no one ever beams down/lands on a planet without checking first (though sometimes it's not always shown. However, you figure if the crew knows how to dress, they also know the air won't kill them them the second they arrive.)
** Then, there are the in-betweeners (planets that are ''nearly'' Earthlike and can [[
** ''[[Star Trek: Voyager
*** Technically, Venus is a Class N planet. Although the difference is mainly academic: either way, humans can't survive on it unprotected.
** In episode of [[Star Trek: Enterprise
* 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 [[Neglectful Precursors|Ancients]]) having [[
** Justified in ''[[Stargate (
** And let's face it, why would you place a ''pedestrian-accessible'' Stargate on a planet that wasn't amenable to humanoid life?
*** [[Stargate Atlantis
**** [[Justified Trope|It was the Wraith's doing.]] We surround our cattle with electric fence. The Wraith's [[I Am a Humanitarian|cattle]] is a bit more intelligent.
**** Except that the planet guarded by Chaya Sar (an ascended ancient) has an orbital gate. And the wraiths surely didn't put it there.
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** This is actually [[Justified Trope|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. 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?
**** ''[[
** They actually played with/subverted this trope in the teaser for a Season 9 episode. Most of the alien worlds, as stated, look almost exactly like the woods around [[Vancouver]] so the audience wouldn't be too surprised to have an episode open with a [[Mook|Jaffa]] running through one of these alien forests... until he gets hit by a truck and you find out that he was on [[Earth All Along]].
*** ''[[
* Likewise, all the inhabited worlds in ''[[
* ''[[Sliders]]'', which dealt with Earths in [[Alternate Universe|parallel universes]], [[Hand Wave|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.
** Although it did once briefly drop them on an Earth that was covered completely with ''fire''. Of course, they were standing in the one safe spot, and {{spoiler|the fire was ''alive'' and followed them}}.
* Aversion: In ''[[Dans Une Galaxie Pres De Chez Vous]]'', where a dysfunctional crew of French-Canadians tries to find one of these, it turns out there's [[Planet of Hats|every]][[Single Biome Planet|thing]] ''besides'' Earth-like planets!
* Averted by ''[[
* ''[[GURPS]] Space'' arguably goes [http://irregularwebcomic.net/94.html 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.
== Real Life ==▼
* Although not an exact example, the discovery of Zarmina (aka Gliese 581 g), the first extrasolar planet potentially capable of supporting Earth-like life, after just under twenty years of searching has some scientists convinced that Earth-like planets are actually pretty common.▼
** [[Subverted Trope|Subverted]] in that while it could possibly (we don't know for sure yet) support Earth-like life, it's still ''very'' different from Earth. Just for a start, the planet is tidally locked around its red dwarf sun, meaning that one side is always facing the sun while the other is in perpetual darkness. This means that the only habitable zone is the terminator, where it would be an unending dusk/twilight. Furthermore, the surface gravity is significantly higher (1.5 g is the current estimate), although still within a (relatively) comfortable range. ▼
** Gliese 581 g's existence has been called into question. Other teams examining the system have been unable to confirm its orbit. That said, the presence of planets potentially like Gliese 581 g has some interesting ramifications for the type of habitable worlds possibly present in the universe. If it's common for larger red dwarfs to have planets like that, then the ''majority'' of habitable planets may be those orbiting red dwarfs (since they vastly outnumber more luminous stars). ▼
* Due to observing how life exists in the most extreme environments on Earth, more scientists are beginning to ponder whether perhaps a planet doesn't need to be exactly like Earth to support some form of life, just a form of life very different from what we're used to. Carbon-based water-dependent life is likely, even if the secondary elements used (S, P, and in lesser quantities Fe, Ca, Na, etc.) in their biochemistry is different. Europa for example might evolve life in its vast underground ocean, though it would almost certainly be blind and use echolocation, perhaps, for there's no sunlight down there and energy is provided by tidal heating. Unfortunately for them, even if they rose to intelligence, they'd be trapped under a thick worldwide roof of ice and never know of the planet they orbit, their home star, and the wider universe. [[Carl Sagan]] even posited that life could arise in the upper atmospheres of ''gas giants'' and evolve there, as creatures incredibly different from us. However again, they'd be unlikely to form spacefaring civilizations, for the tool-making, agriculture, metallurgy, etc. that we're capable of would be impossible on their world, or at least be a lot less effective.▼
** That's not necessarily the case. While they'd be handicapped in terms of fire while only being able to work in a water environment, there are other ways to develop advanced technology that don't require open flames. They might develop technology based much more around the use of ''electricity'', which is easier to conduct in salty sea water, and which has been partially utilized by sea life on Earth. Even fire might not be totally off-limits on ice-covered ocean worlds, since they could presumably carve out water-free chambers in their planet's ice layer (and use flammable materials that can be found in water environments, such as methane hydrates).▼
* NASA's Kepler space telescope is dedicated to searching for planets around other stars. [http://io9.com/#!5750678/kepler-telescope-discovers-1200-new-worldsand-at-least-five-potentially-earth+like-planets As of February 2011], after surveying 156,000 stars, it has ''possibly'' (these discoveries are hard to be 100% certain about) found ''five'' planets that are Earth-like in terms of size and distance from their parent star. About 50 other found planets are much larger than Earth, but do orbit at about the right distance to make life possible (and so some could be -- purely hypothetically -- gas giants with habitable moons and the like). Considering the ''total'' number of possible planets found by Kepler is about 1,200, this seems like very much an aversion of [[All Planets Are Earthlike|All Planets Being Earthlike]]. On the other hand, with only 156,000 stars surveyed, and between two and four ''hundred billion'' stars in our galaxy, this discovery suggests that the ''total'' number of Earth-like planets out there may be very large.▼
** It's important to keep the limitations present on existing telescopes in mind. One of the reasons why Kepler has found so many "Neptunes" and "Super-Earths" is because they're easier to find than Earth-sized planets (never mind those even smaller than Earth in size).▼
** And on December 2011 scientists announced that Kepler found [http://news.cnet.com/8301-19514_3-57337039-239/earth-like-planet-found-in-distant-suns-habitable-zone/ Kepler-22b, a world twice the size of Earth] and parked well within the "Goldilocks" orbit that would allow for water to exist in liquid form (meaning it could generate carbon-based life similar to our own).▼
* Venus. Often called Earth's "sister planet" due to having an extremely similar mass, and favourable position relative to the Sun. The extreme heat and pressure make surface colonies unlikely (although there's always the possibility of terraforming it in the distant future), but various other [[Awesome Yet Practical|surprisingly sensible]] ideas exist. Notably, at an altitude of 50km, the atmosphere is friendly enough to allow humans to '''go outside without a pressure suit''' (although masks would still be needed). Serious proposals for floating cities at this altitude have been made.▼
* Alien life, if it exists, is likely to have ''some'' properties in common with Earth's life, if only because some biological life-strategies are too effective to pass up. Photosynthesis, for example, is an efficient way of acquiring energy, and a large surface area is advantageous for that, so it's likely that some form of "vegetation" with broad structures to collect light would arise on any world with land-based multicellular organisms.▼
* Despite all the science and fact-based theories out there the fact of the matter is we will never be able to conclusively pin down how much a planet can differ from Earth itself and still stay earth-like (for instance, ratio of ocean to land - most of our oxygen comes from the ocean), until we actually find earth-like worlds to compare (or terra-form our own). This is not to say that our theories aren't good science, they are. We just don't have any real-life examples to closely analyze to compare results yet, and there are always surprises ahead no matter how well-checked your math is.▼
* Compared to before the 1990's, when without solid proof of other exoplanets scientists were still bandying around the possibility that our planetary system itself could be a rare fluke among stars, it's pretty much a statistical certainty that there are other earthlike planets out there that should ''meet all the criteria'' to be Earthlike. Whether or not any actually do have life, etc? That's to be seen.▼
▲== Tabletop RPG ==
▲* ''[[GURPS]] Space'' arguably goes [http://irregularwebcomic.net/94.html 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 [[Precursors|Ancients]].
* In ''[[
** 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 like in ''[
* Not exactly an RPG, but [[Warhammer
** And being [[Crapsack World|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.
*** And then there's the ones where the atmosphere, gravity and water table are all near-perfect Earth standards... But everything from the smallest plant to the giantest bug wants to eat you ALL THE TIME. One world is so hostile that all habitation is on giant MOBILE CITIES because the [[Single Biome Planet|world-encompassing jungle]] would overtake any man-made structure in a matter of days, nevermind the ''creatures''. The oh so subtle name for such a planet? [[Death World]]. Beloved by the Imperial Guard and Space Marines because the people that grow on them tend to make [[Badass]] soldiers.
** 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".
== Toys ==
* Spherus Magna in ''[[Bionicle]]''. When [[Earthshattering Kaboom|The Shattering]] happened, it was divided into three [[Single Biome Planet|SingleBiomePlanets]]- one jungle, one mostly desert, one ocean. Although it's fair to assume not all inhabitants survived the event, most species retained a breeding population, and were able to function on the new planets with no apparent alterations to the atmosphere or gravity. Furthermore, two of these "planets" are actually moons of the bigger planet, yet the inhabitants didn't seem to suffer from a 28-day long day-night cycle. Then when Spherus Magna was restored to its Earthlike state, there was no mention of increased gravity whatsoever.
== [[Video Games]] ==
* In the old ''[[
* ''[[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 Cura?, 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 [[
** Most of these planets are covered in rocky pine forests.
* In the ''[[
* ''[[Meteos]]'' averts this trope. There is only one Earth-like planet in the game; every other planet is pretty much unique and un-Earth-like in its [[Single Biome Planet|own]] [[Planet of Hats|ways.]] Some of these are not even planets at all. Intelligent life, in this series, have sprung up on dwarf planets, asteroid clusters, dimensional rifts, interstellar gas clouds, neutron stars, and even mythological realms.
* ''[[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 shown in the first game are safe for humans, in a game shows around a hundred. 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.
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** In ''[[Mass Effect 2]]'', most of the planets you visit are at least partially Earthlike. Key word being ''visit'': you only ever touch down on planets with some kind of habitation, even if it's just a tiny mercenary resupply point. Also, the Blood Pack have a base set up on a world that's filled with gas that's toxic to all your crew members but the Vorcha can live there fine.
* ''[[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 ''[[
* Subverted in ''[[Earth 2150|Earth 2160]]''. The game takes place on a number of celestial bodies in the Solar System and around the nearby stars (one mission takes place on a very large ''comet''), but of these, only 2 planets are actually suited for human habitation. One of the is a desert planet reminiscent of the one in the ''[[Stargate]]'' movie (complete with ancient [[Precursors|alien]] pyramids), while the other is a ''very'' Earthlike planet called Eden. The main characters are visibly surprised when they see a video from the surface, and some even suspect that it's actually old Earth footage.
** All of the above locations are made a bit less pleasant by the Morphidian presence.
* ''[[
* ''[[
* The Lunarian Moon (no, that's not redundant) in ''[[
* 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]].
* Subverted in ''[[Sid
* The [[Escape Velocity]] games feature all kinds of planets. The most you'll ever see of one, though, is a little pre-rendered image. Many of the ones that you can actually interact with are habitable for one or another reason.
* [[Star Control]] 2 averts this trope hard: it has at least 50 ''types'' of planets. The kinds that support (humanoid) life are rare;
* ''[[Galactic Civilisations]] II'', with all of its expansions in, finally adds toxic, ocean, high grav, barren and other world types. However, you can research technologies to colonise all of them.
** Except possibly on the highest "usable worlds" setting, nearly all of the worlds you encounter are not only not earthlike but completely uninhabitable quality 0 gas giants or tiny balls of scorched or frozen rock. Although there are weird mega-events that occasionally roll through and turn an entire system into medium to high quality potential colonies, regardless of the size or nature of the planets.
* ''[[Star Ocean: Till the End of Time]]'' is guilty. Although there are a variety of planets not suitable for humans to live on (or those where it'd be very difficult for them to thrive), the main party always conveniently lands on one where they can breathe the air and move around comfortably despite any effects of the gravitational fields.
** {{spoiler|[[A Wizard Did It|The 4D beings designed things that way]].}}
* Subverted in the ''[[Halo]]'' series. It's revealed in the EU that it takes ''decades'' of terraforming to make a colony world suitable for human use.
* [[Space Colony]] averts this with no planets capable of supporting life without assistance, the planet range from barren, to volcanic and a few that have a bit ''too' much life on them.
* Averted in ''[[
* Comprehensively averted in ''[[Space Empires]] IV'', in which you set your race's preferred atmosphere and planet type (ice, rock or gas giant) and start out only able to colonise those.
* Averted in the ''[[X (
== [[Web Comics]] ==▼
▲== 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 [[Single Biome Planet|a planet-wide desert]]. Only, for the purposes of this trope, it's still Earth-like enough.
** "[http://www.darthsanddroids.net/episodes/0050.html 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 [[Lampshade Hanging|addresses the oddness]] of this, with Riff saying, "I've never seen a universe so ... deliberate." {{spoiler|Later [[Justified Trope|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.
* [http://www.irregularwebcomic.net/94.html This] ''[[Irregular Webcomic]]'' strip demonstrates what will happen if this trope didn't exist.
{{quote|
''You forgot that system with the uninhabitable gas giant with no interesting features whatsoever.'' }}
▲== Web Original ==
* [[Nexus Gate]]: The worlds of Taivas and Cielo
* Many of the planets and moons in ''[[
== [[Western Animation]] ==▼
* In the '90s ''[[X-Men (
▲== Western Animation ==
* ''[[Phineas and Ferb]]'' is especially
▲* In the '90s ''[[X-Men (Animation)|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.
* Averted in ''[[
▲* ''[[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.)
▲* Averted in ''[[Star Trek the Animated Series (Animation)|Star Trek: The Animated Series]]''. Personal environmental force fields allow the crew to explore planets without atmospheres while wearing nothing but a uniform. (A yellow line around each character was [[Limited Animation|easier to animate]] than spacesuits, which are what the live-action Treks use.)
* 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 [[Alien Sky|three giant suns]], apart from being a bit warm at full noon, was perfectly livable to humans.
▲== [[Real Life]] ==
▲* Although not an exact example, the discovery of Zarmina (aka Gliese 581 g), the first extrasolar planet potentially capable of supporting Earth-like life, after just under twenty years of searching has some scientists convinced that Earth-like planets are actually pretty common.
▲** [[Subverted Trope|Subverted]] in that while it could possibly (we don't know for sure yet) support Earth-like life, it's still ''very'' different from Earth. Just for a start, the planet is tidally locked around its red dwarf sun, meaning that one side is always facing the sun while the other is in perpetual darkness. This means that the only habitable zone is the terminator, where it would be an unending dusk/twilight. Furthermore, the surface gravity is significantly higher (1.5 g is the current estimate), although still within a (relatively) comfortable range.
▲** Gliese 581 g's existence has been called into question. Other teams examining the system have been unable to confirm its orbit. That said, the presence of planets potentially like Gliese 581 g has some interesting ramifications for the type of habitable worlds possibly present in the universe. If it's common for larger red dwarfs to have planets like that, then the ''majority'' of habitable planets may be those orbiting red dwarfs (since they vastly outnumber more luminous stars).
▲* Due to observing how life exists in the most extreme environments on Earth, more scientists are beginning to ponder whether perhaps a planet doesn't need to be exactly like Earth to support some form of life, just a form of life very different from what we're used to. Carbon-based water-dependent life is likely, even if the secondary elements used (S, P, and in lesser quantities Fe, Ca, Na, etc.) in their biochemistry is different. Europa for example might evolve life in its vast underground ocean, though it would almost certainly be blind and use echolocation, perhaps, for there's no sunlight down there and energy is provided by tidal heating. Unfortunately for them, even if they rose to intelligence, they'd be trapped under a thick worldwide roof of ice and never know of the planet they orbit, their home star, and the wider universe. [[Carl Sagan]] even posited that life could arise in the upper atmospheres of ''gas giants'' and evolve there, as creatures incredibly different from us. However again, they'd be unlikely to form spacefaring civilizations, for the tool-making, agriculture, metallurgy, etc. that we're capable of would be impossible on their world, or at least be a lot less effective.
▲** That's not necessarily the case. While they'd be handicapped in terms of fire while only being able to work in a water environment, there are other ways to develop advanced technology that don't require open flames. They might develop technology based much more around the use of ''electricity'', which is easier to conduct in salty sea water, and which has been partially utilized by sea life on Earth. Even fire might not be totally off-limits on ice-covered ocean worlds, since they could presumably carve out water-free chambers in their planet's ice layer (and use flammable materials that can be found in water environments, such as methane hydrates).
▲* NASA's Kepler space telescope is dedicated to searching for planets around other stars. [http://io9.com/#!5750678/kepler-telescope-discovers-1200-new-worldsand-at-least-five-potentially-earth+like-planets As of February 2011], after surveying 156,000 stars, it has ''possibly'' (these discoveries are hard to be 100% certain about) found ''five'' planets that are Earth-like in terms of size and distance from their parent star. About 50 other found planets are much larger than Earth, but do orbit at about the right distance to make life possible (and so some could
▲** It's important to keep the limitations present on existing telescopes in mind. One of the reasons why Kepler has found so many "Neptunes" and "Super-Earths" is because they're easier to find than Earth-sized planets (never mind those even smaller than Earth in size).
▲** And on December 2011 scientists announced that Kepler found [http://news.cnet.com/8301-19514_3-57337039-239/earth-like-planet-found-in-distant-suns-habitable-zone/ Kepler-22b, a world twice the size of Earth] and parked well within the "Goldilocks" orbit that would allow for water to exist in liquid form (meaning it could generate carbon-based life similar to our own).
▲* Venus. Often called Earth's "sister planet" due to having an extremely similar mass, and favourable position relative to the Sun. The extreme heat and pressure make surface colonies unlikely (although there's always the possibility of terraforming it in the distant future), but various other [[Awesome Yet Practical|surprisingly sensible]] ideas exist. Notably, at an altitude of
▲* Alien life, if it exists, is likely to have ''some'' properties in common with Earth's life, if only because some biological life-strategies are too effective to pass up. Photosynthesis, for example, is an efficient way of acquiring energy, and a large surface area is advantageous for that, so it's likely that some form of "vegetation" with broad structures to collect light would arise on any world with land-based multicellular organisms.
▲* Despite all the science and fact-based theories out there the fact of the matter is we will never be able to conclusively pin down how much a planet can differ from Earth itself and still stay earth-like (for instance, ratio of ocean to land - most of our oxygen comes from the ocean), until we actually find earth-like worlds to compare (or terra-form our own). This is not to say that our theories aren't good science, they are. We just don't have any real-life examples to closely analyze to compare results yet, and there are always surprises ahead no matter how well-checked your math is.
▲* Compared to before the 1990's, when without solid proof of other exoplanets scientists were still bandying around the possibility that our planetary system itself could be a rare fluke among stars, it's pretty much a statistical certainty that there are other earthlike planets out there that should ''meet all the criteria'' to be Earthlike. Whether or not any actually do have life, etc? That's to be seen.
▲* Many of the planets and moons in ''[[Orions Arm]]'' are rather earthlike, but it justifies it in that most of them were terraformed in some way. However even if you include the terraformed planets they are still greatly outnumbered by the non earthlike planets in this universe, ultimately making this an aversion. The non earthlike planets in Orion's Arm can be anything from dead rock worlds, to planets covered in atmospheres of strange gasses and pressures, yet thriving with ([[Starfish Aliens|non earthlike]]) life.
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