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The Earth in all of its varieties has wide ranging climates. At the top level it has tropical, dry, temperate, continental, and polar climates. And yet often the planets depicted in science fiction are often single climate planets.

  • The forest moon of Endor
  • The desert planet of Dune
  • The desert planet of Tatooine
  • The desert planet of Vulcan
  • The outer planets in Firefly all appeared to be mostly desert (supiciously like Calfornia desert).
  • The inner planets in Firefly were all temperate or tropical.
  • The icy Breen homeworld
  • The icy Andorian homeworld
  • The icy Frost Giant planet

I'm not suggesting there are no Earth-like planets in science fiction, but it feels like it is less common than it should be. Considering the only planet we have as an example is our own, it seems like planets should be just as varied in the cosmos.

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

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    Is being 70% covered by water that varied? ;) – gnovice Jun 20 '12 at 15:35
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    Stargate SG-1 did a good riff on this: Sam and Jack are stranded in an ice cave, and Sam comments "Ah, an ice planet". Of course, it turns out to just be Antarctica. – Daniel Roseman Jun 20 '12 at 15:50
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    Let's not confuse climate with terrain. "Forest", "desert" and "swamp" (you forgot Dagoba) describe arrangements of vegetation, which we associate with climate, because here on Earth that's what plants do. Take away all the plant life, and Earth would look much less varied. Personally I'd love to see more SF with alien biomes that had different comfort zones; we could walk around in sub-zero swamps, forests in perpetual "darkness", lush grassland hotter than Death Valley... But that would require rare writing skill. Endor is much easier. – Beta Jun 20 '12 at 21:31
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    Compare to Majirpoor, Tiamat, Tines World, More Prime, etc. If you consume simple, lazy, sketchy or ill-thought-out material you're going to get sketchy, lazy, simple or ill-thought-out planets. There is probably less of the good stuff, but that is not a large surprise. – dmckee Jun 21 '12 at 0:59

14 Answers 14

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This is known on tvtropes as the Single Biome Planet trope:

Planets in outer space will often be defined by a single setting. It doesn't matter if the events of the story only take place in on a small portion of the planet — we are still told the entire planet has one climate; specifically, the same climate as where the story takes place. Very rarely does any planet have the same level of environmental diversity as Earth, despite being as large and having a normal orbit. An ecological equivalent to the Planet of Hats.

See the link for a more complete description and a pretty long list of examples. It also discusses when single biome planets can be justified.

Personally I am often annoyed by the frequent occurrence of this trope in mainstream SF and Fantasy (although the latter also often succumbs to the opposite, Patchwork maps). It can make an entire world flat, uninspiring and implausible, and I would advise any aspiring SF writer to avoid this at all cost.

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Since humans evolved on the Earth, we're sensitive to its climatic variations. -10C is arctic, +30C is tropical. Alien planets are unlikely to be centred around the temperature ranges that humans find comfortable. If a planet has as much variation as the Earth but in the range -60C to -20C, it's all arctic. If it's +30C to +70C, it's all hot (and much of it is probably uninhabitable).

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    Yes! If you demand an in-universe explanation, this is a good one. – ThePopMachine Jun 20 '12 at 16:31
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    +1, Very likely to be the best explanation, but it doesn't quite explain missing vegetation, like on the deserts of Vulcan or the ice of Andoria. I'd expect it to have just adapted, but instead of matches deserts/ice fields of Earth: Little/no vegetation. – Izkata Jun 20 '12 at 18:00
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    @Izkata -- The lack of vegetation on Vulcan always made me wonder about how the entire Vulcan race could be vegetarian. – Roddy of the Frozen Peas Jun 20 '12 at 19:34
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    @RoddyoftheFrozenPeas Their hairstyle makes for good solar panels? – Izkata Jun 20 '12 at 19:40
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    Probably lived underground since the planet was hellish a good portion of the year, and likely grew food underground as well to support their population. Vulcan did not look like it was a planet prone to suffering from overpopulation so perhaps their controlled population didn't need much or perhaps they imported food from alien worlds. – Thaddeus Howze Jun 20 '12 at 19:40
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There are several reasons science fiction worlds do not suffer the climactic variability of Earth. Increased simplification of writing or display in media, lack of scientific knowledge of writers regarding weather and climate, and unless weather is an active participant in the story, it is more a window dressing or stage setting than something to be focused on as an element in a story.

  1. Easier to write about if the entire planet is one giant ecosystem of one type or another. Readers or watchers say, "oh an ice planet" and are able to move on to the next part of the story. This trope is far more common than you realize. Watch any modern science fiction and you will see this trope in action.

  2. Writers are often limited in their understanding of the causes of weather, the development of climate, or environmental conditions contributing to weather. So, when in doubt, they make the entire world that way and move on.

  3. A planet without an axial tilt, and with a circular orbit (rather than elliptical), will tend to have fairly uniform weather bands across the same latitude of a planet because there is an even heating and cooling of the world. Our world's weather varies strongly because of the Earth 23.4 degree tilt on its axis. This tilt creates variability in our weather and in conjunction with our variation in distance from the sun can cause a wide variation in our weather patterns.

enter image description here

So, seasonal changes depend on the tilt of the earth's axis because they lead to changes in the amount of heat delivered to a square meter of surface, and the fact that there are a changing number of hours in the day when the Sun is above the horizon and high enough up that it can efficiently heat the surface over the course of a typical day. --Goddard's Space Flight Center > Ask an astrophysicist

Seasons due to Axial Tilt

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    #3 doesn't make a lot of sense. Firstly -- Earth's axial tilt is not particularly large, at least among the planets in our Solar System. Secondly -- a planet with no axial tilt will not have seasons, but it will still have a non-uniform climate: the poles will be colder than the equator, Coriolis-generated wind patterns will depend on the latitude and on the arrangement of continents and seas, etc., etc., etc. – ruakh Jun 20 '12 at 18:59
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    Look, I don't make the weather or report it, but there is loads of evidence reporting on the effects of both axial tilt and uneven heating as part and parcel of our weather and climate. And 23.4 degrees DOES make a difference. – Thaddeus Howze Jun 20 '12 at 19:07
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    Eh? Sorry, I think you must have misunderstood my comment. (Or else I'm misunderstanding yours.) What I'm saying is -- your point #3 relies on two faulty assumptions. Faulty assumption A: that other planets don't have axial tilt. In fact, they do. Of the planets in the Solar System, the majority have even greater axial tilt than Earth. (You write of Earth's "normal zero degree tilt" until it was struck by a Mars-sized body, but your link doesn't support that.) – ruakh Jun 20 '12 at 19:20
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    Faulty assumption B: that a planet without axial tilt will have a uniform climate. In fact, it won't. Its climate patterns will be different from Earth's, of course, because Earth's climate is hugely affected by its axial tilt, but its climate near the poles will still be much colder than that near the equator, its wind patterns will still be affected by the arrangement of land and sea (if it has those), etc. – ruakh Jun 20 '12 at 19:22
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    I get a lot of flack for taking the time to write extensive treatments replete with what are considered too many scientific facts. I tried to keep it as simple as possible so I could make a point without writing a book. I am forced by social convention to allow readers to do their own research. Assumptions made here are NOT mine. I do understand there is FAR more to weather than axial tilt, distance from the sun, arrangement of continents, and other events like the Coriolis Effect. TRYING TO KEEP IT SIMPLE. Giant Impact Hypothesis: en.wikipedia.org/wiki/Giant_impact_hypothesis – Thaddeus Howze Jun 20 '12 at 19:28
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I imagine this could be the result of a prevailing sense that our little blue planet (and in particular the climatological state that it's in now) is very much unique and unusual in its features. Consider the following points:

  • The other eight seven planets of our star system are fairly uniform: a hot, desolate marble (Mercury), an inhospitable greenhouse (Venus), a cool desert (Mars), and a bunch of gas giants. Even if you consider some of the larger moons, like Europa or Io, you still see some fairly uniform climatic features.

  • The geological history of Earth suggests that we have gone through "Greenhouse" and "Snowball" periods where the climate would have been quite a bit more uniform. The variety in climate we see now could therefore be considered uncharacteristic or short-lived.

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    Poor Pluto. In my mind you will always be a planet. – hammythepig Jun 20 '12 at 16:11
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    @hammythepig: It's a real-life retcon. Pluto shot first! – gnovice Jun 20 '12 at 16:20
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    Well, only the planet with the "odd" climate has live. Maybe its correlated? So if we visit other civilisations maybe an Earth-like planet is implied? – bitmask Jun 20 '12 at 16:29
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    The other planets look uniform from a distance. Mercury has surface temperature that varies roughly from 450C to -170C, which makes Earth look like a rare-book vault. Mars has temperature variation almost as great as ours, ice caps, and tremendous seasonal dust storms. The gas giants require a whole new definition of "climate". Venus... well, yeah, Venus is pretty much the same all over. – Beta Jun 20 '12 at 21:17
  • @Beta yeah, Venus basically amounts to a planet-wide thermos. There may be variation due to Coriolis forces storing up storms etc, some areas may be more prone to having lakes for example (of sulphuric acid, for "fun", of course.) as an example, different areas may undergo different weathering patterns leading to different terrain. It's just a bit hard to study any of it. but for example Radar images of Venus have revealed geological structures on the planet, such as steep-sided domes and rugged highland terrain – Baldrickk Mar 29 at 9:29
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Theme

The main reasoning is that the minds behind the stories being told have an idea or a concept they want to get across, which is an easier concept to send to the viewer/reader if the entire planet only features one biome.

On Hoth for example they want to show how far out the rebels have been pushed, to what extremes, literal and figurative, they have been forced. As such it necessitates the entire planet being shown as an ice planet so no one has to explain why the rebels chose that ice-desert over a tropical region.

On endor the idea may have been to show a less advanced group (rebels) over throw the more advanced enemies. To facilitate this, they force the juxtaposition of shield generators and AT-ST in the jungle. And work with common understandings of jungle dwelling civilisations being less advanced to show off the accomplishment is down to perseverance, not superior tech.

  • I think you've buried the lead here - you only ever see "extreme" biomes as whole planets [to handwave explaining why the installations weren't in a more favorable region]. I've never heard of a temperate planet. – Random832 Jun 21 '12 at 17:20
  • Sorry what do you mean 'buried the lead'? – AncientSwordRage Jun 21 '12 at 17:23
  • Sorry, it's just an expression - i.e. that in my opinion the "you only see it with extreme biomes, since you don't need an excuse to tell a story in a temperate biome" bit is the most important factor, and you just mention it offhand. – Random832 Jun 21 '12 at 17:24
  • @Random832 Fixed? – AncientSwordRage Jun 21 '12 at 17:33
  • That's fine - I didn't actually intend it as a criticism, just my two cents, and I'd even upvoted it before. Your edit works, though. – Random832 Jun 21 '12 at 17:34
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H.P. Lovecraft wrote about this topic in an article in 1934, and criticized exactly these points in the 1930's: "Some Notes on Interplanetary Fiction (written around July 1934; Winter 1935)". And then there is the wonderful Supernatural Horror in Literature, which was aiming more generally at what makes fantasy/sci-fi literature and film adaptations rather predictable. Oh, and it's a very interesting insight into the history of, what he calls "Supernatural Horror."

I have the text, but it's not in English... but he points at exactly the things that make 90% of sci-fi so very generic. Stanislaw Lem and the brothers Strugatzki went very different ways in that area. Hope this helped a little bit. Cheers!

  • Can you add some information from that text? Right now, this answer says "HP Lovecraft commented on this, here's a link." We prefer to have information included in posts on this site rather than merely linking to the source. Links go dead over time, so duplicating the key pieces of information here makes this answer longer-lasting. – user1027 Jun 20 '12 at 19:51
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    the text deals mostly with the 'horror' based upon primal fears of something so different from what is known or imaginable, and the wasted potential (his opinion). Alien cultures mirroring the human society, with only exchanging looks is not very creative. The text is a harsh criticism, written about 80 years ago and still so true in all it's points. Sadly, I didn't find the whole text online anywhere, though I guess it should be in the public domain already - but it can be found in various collections of his essays etc. So the title might be helpful in the next visit at a library. – el_olmo Jun 20 '12 at 20:54
  • Click the 'edit' link below you answer and add that information there. – user1027 Jun 20 '12 at 20:57
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    As far as i can see from short russian quote, Lovecraft simply pointed out that low skill writers of cheap fiction cannot describe believable worlds (or characters, or technologies) and this will never change. – c69 Jun 25 '12 at 14:25
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The issue is that we're talking about science fiction here. Note that while the genre in theory is not so young (just to give one example, Icarus could be considered science fiction, as it featured technology that made something possible that actually wasn't in that time). The concept of actually visiting different planets is (200 years is young in this context).

Also, stories are essentially memes. I would argue there isn't a single truly 100% original story. Everything is ultimately tailored together (while still allowing for creativity and innovation) from ideas that the writer(s) picked up from other writers. Like the evolution of genes, the evolution of memes takes time (while it is faster by orders of magnitude).

If you can't go to other planets you're stuck on earth. A scenery of a location is a functional element of a story if it's of any importance. For instance, if you tell the story of Columbus, an important element of that story might be the rough sea. That's a fixed location, as a plot element. Similarly there are stories that involve traversing a desert. Again, you're immobile because the roots of the memes that we keep evolving lie in a time, where you couldn't change location that fast.

Now, if you write a story that involves planets, they're locations, and since the story is inspired by previous memes it makes sense that that location has fixed properties, such as being extremely cold.

So of course you can introduce a planet with realistic heterogeneous climates, but in order for it to be actually part of the story, you have to come up with a story that genuinely involves these features, and you have little inspiration to work with.

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I think that Mike Scott is partly correct.

However, there is another crucial aspect - useful land masses. Humans prefer to settle on land in places that have convenient resources (water, minerals, arable land). So, if a planet has only one continent, and that with an average temperature of -10C then it may not matter what the rest of the planet's climate is - people are probably going to think of it as an ice planet.

In truth, we don't really know that much about planet formation and this gives writers tremendous latitude when world building. As long as the planets they create are within reason, given the climate factors that we do understand, nobody can really say that they're wrong.

  • Good point about settlement patterns, but I have to disagree with your second paragraph. Nobody can really say they're definitely wrong, but just as with rubber forehead aliens, we can say that they're almost certainly wrong, and that they're being lazy. – user1786 Jun 22 '12 at 3:54
  • Clarke's first law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong. – Donald.McLean Jun 22 '12 at 4:02
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Most science fiction and fantasy is inevitably linked to existing story-telling tropes.

So what would, in a traditional setting, be an (environmentally homogenous) city or country becomes a planet, a continent becomes a star system, the world becomes a galaxy and different races or cultures are translated into different sentient species.

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I think most books or movies only show a small part of the planets. Who knows what the rest was like?

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    That would be a great simple explanation, except that in many (most?) cases, the planets are either explicitly or implictly described as being homogeneous ("the ice planet Hoth", not "the planet Hoth, where they've built a base in the arctic zone"). – user1786 Jun 22 '12 at 3:56
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For the same reason that characters, events, places, and everything else in fiction are not as varied as in reality ... because the author is telling a specific story.

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While the answer to your question is, in most cases due to author laziness or thematic considerations, I do take exception to the following:

The desert planet of Dune

Dune is a desert planet due to very important story considerations. It is a planet that has been undergoing extreme climate change due to organisms which lock away the water, leaving the entire planet effectively waterless.

The ecology of Dune is a very integral part of the story. Other planets are barely mentioned other than in rememberings of the main characters or descriptions (Salusa Secondus was known as being a prison hell planet but the ecology of it was not really talked about).

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I'd like to add an answer with some science. If you consider the history of planet earth (e.g. at earth history, wikipedia) you will see that for most it's 4.5by history earth surface wasn't as diverse as today.

There was a long "hellish" phase with volcanic desserts and greenhouse effect too hot for lakes. Desert phases as no plants were around to gr (just look at Mars). and even some snowball phases (snowball earth) where even at equator temperatures were as low as nowadays Antarctica.

So there is definitely some scientific logic of expecting some planets to be completely desert or frozen.

Forest and jungle planets are a different story. It may suffice that a "planet" is small enough. Endor is actually just a moon. But that's all speculation.

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I personally think it was a product of the early adventure novels/comics since those often ended up with people sailing to other islands that are similar but different to known earth, and it made them seem far away exotic and special.

Meanwhile planets as variable as earth don't seem, as memorable or special.

RPGs are like this too, your opening country usually has multiple cities, then later each other region has one city. We do this in real life too, the more further out the more we try and associate each area with something simple.

For example I used to think spain was just colorful buildings, flamenco and bull fighting in every city. Then I went to 3 different cities extremely close to each other there and they were more varied than New York, Calgary, and LA could ever be to each other.

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