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I have humans who live in a world filled with floating islands. These islands span all heights in the planet: from the core to the upper atmosphere. The problem I have is that most of these islands are too small to have an internal water cycle. Is there a way to provide the people with a reliable source of water? if so, how would I go about doing it?

Conditions

  • The mechanism that makes the islands float is irrelevant/not to be considered.
  • The planet is a puffy gas giant, for all intents and purposes there is no surface.
  • The people I have to provide live in an earth-like environment (1atm, 1g, earth-like atm. composition, sun-like star, etc). Of course, these conditions change as expected as people travel up and down through the atmosphere.
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    $\begingroup$ how dense are the islands? if there are enough of them rain and runoff could produce streams and ponds, assuming you have a ocean underneath the islands. $\endgroup$ – John Jan 31 '17 at 16:46
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    $\begingroup$ If the islands can float, what's against an upward streaming waterfall? The gas giant planet makes it extra hard though. $\endgroup$ – Mast Jan 31 '17 at 19:09
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    $\begingroup$ -1. This question can't be answered properly if the mechanism of the floating islands is unknown. $\endgroup$ – March Ho Feb 1 '17 at 4:23
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    $\begingroup$ Possible duplicate of City on a Cloud - how to build an effective water supply? $\endgroup$ – Frezzley Feb 1 '17 at 12:07
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    $\begingroup$ Harvesting passing clouds, like collecting rain water, is the first thing that came into my mind... $\endgroup$ – Josh Feb 4 '17 at 14:42

19 Answers 19

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While I am answering my own question, this is by no means a definitive answer, please contribute your own if you feel there are other alternatives

There is a kind of plant in the Andean regions of northern South America called Espeletia (also known as Frailejón).

Espeletias

This plant converts air humidity into water with the help of its hairy leaves. It then gathers this water in its trunk and releases it on the soil through its roots. Large populations of these plants can feed entire rivers with water.

Given the environment, it's not a stretch to have a large number of plants evolve to have similar water-condensing mechanisms. Such mechanisms would provide the plants in question with water, as well as other living beings that may benefit the plant. Such as other plants that to help create nutrient-rich soils and animals to help spread seeds.

Another additional source of water would be cacti-like plants. Plants which gather water inside of them instead of releasing it to the ground. These plants may then be eaten as a source of nutrients and water.

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    $\begingroup$ This is a better answer than mine :) $\endgroup$ – James Jan 31 '17 at 17:13
  • $\begingroup$ Beat me to it! I hadn't realized there was an exact real-life analogy, but I straight away envisioned some sort of cactus that could get water from the air and then store it :P $\endgroup$ – Braeden Orchard Feb 1 '17 at 2:10
  • $\begingroup$ Just an additional thought, this can be reproduced mechanically as well, not just biologically. So you're not limited to just plants. $\endgroup$ – Bryant Jackson Feb 1 '17 at 17:08
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    $\begingroup$ The Canary Island pine has a similar effect: en.wikipedia.org/wiki/Pinus_canariensis Despite being a tropical volcanic island with a very large population, Tenerife makes very sparing use of desalination to supply municipal water. This is largely due to the water captured by the large pine forests that cover the center of the island. $\endgroup$ – Oliver Feb 2 '17 at 12:09
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Fundamentally you need a large enough body of water for evaporation to occur.

There are two options, the simplest is just to have a "water world" with an ocean down below and have the islands floating above it. That could fuel a standard water cycle, with the islands getting rained on with water evaporated from below.

Alternatively have the water float in the same way the islands do, with floating lakes and oceans hanging in mid air. Waterfalls would run from the lakes and oceans into each other. If your floating islands move then the water cycle could include drifting under a waterfall. If not then a conventional evaporate-precipitate cycle could hydrate them all fueled by the lakes and oceans.

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    $\begingroup$ Oooooh the second idea sounds cool! Think about volcanos and lava... $\endgroup$ – C Anderson Jan 31 '17 at 16:42
  • $\begingroup$ @CAnderson Yes, hard to justify in a science-based answer which is why I put it second. $\endgroup$ – Tim B Jan 31 '17 at 16:43
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    $\begingroup$ There was a larry Niven story about a torus world that had floating "lakes" blobs of water with their own fish. if two got to close they merged like water balls in zero G. The constant stirring caused by the fish keep them from forming perfect spheres. $\endgroup$ – John Jan 31 '17 at 16:45
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    $\begingroup$ @Mrkvička I thought the intended meaning of "A large enough body of water for sufficient water to evaporate that it can then form clouds". was clear by context but I've edited it for you... $\endgroup$ – Tim B Jan 31 '17 at 23:05
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    $\begingroup$ Ah, I see - sorry for my misunderstanding. To me the sentence really sounded as if you claimed that evaporation cannot occur at all unless there is a lot of water. $\endgroup$ – Mrkvička Feb 1 '17 at 6:45
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Floating icebergs. The island dwellers catch and melt them.

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I can think of two relatively realistic...or at least plausible options.

  1. Regular, if not almost constant rain. Its possible that this environment was selectively chosen (considering they are floating around in a gas giant) and the choice would not be made without access to the things you need to survive.

    • Either the natural state of the planet causes rain to fall on a regular basis (regular can be defined by how much water storage they have available)
  2. Super Tech. In this scenario I am thinking you could have a large antenna that reaches out into the atmosphere. By some mechanism it triggers reactions in the air that generate rain. The nature of the technology would be up to you to decide.

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Larry Niven's novels "The Smoke Ring" and "The Integral Trees" imagined life in a diffuse ring of planetary debris orbiting a star. In that world, plants pulled moisture from the air in manners similar to our epiphytes (or what's been described above). People sometimes had ways to exploit the plant mechanisms, or sometimes traveled to large floating "lakes" to extract water from them.

In Niven's "Ringworld" books, there were artificially floating cities with chilled condenser funnel systems for water collection. They worked on the same principle as condensation forming on the outside of a cold drink in the summer time.

Simple rain collection might work at some strata of the atmosphere, though I'm unsure whether physics is friendly to the idea of this happening at standard temperatures and pressures. You might find XKCD's "What If?" on the subject of dropping a submarine into Jupiter helpful for understanding this.

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One possibility (Though I don't know if the physics would work too well) could be simply that the inner layers of the gas are really hot, probably due to extreme greenhouse effects and such. It is hot enough that water always evaporates and it gets pushed back into the atmosphere. Then, it cools into clouds and rains again.

This could help keep the habitable higher areas warm, and also would provide the air with a lot of water. If you have plants that absorb water from the air and leak it into the soil, this gives you a 1-2 punch of water. The rain saturates the island, but most of it seeps through, and then it evaporates and rises up for the plants to gather. The islands get saturated, then keep it for a long time until the next storm comes in.

This would mean there is a lot of rain and large, powerful storms, but that could be a good thing that drives the plot. Gas Giants are going to have hectic weather, so it should constantly be hurricane season.

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  • $\begingroup$ Gigantic storms are one of the reasons I have the world. Lightning hunting is a dangerous job. $\endgroup$ – Miguel Bartelsman Jan 31 '17 at 20:34
  • $\begingroup$ For this to work, the main contents of the gas giant would need to consist of heavier molecules than water, otherwise even the evaporated gas would sink down. So no standard hydrogen/helium gas giant. $\endgroup$ – Paŭlo Ebermann Feb 3 '17 at 17:39
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The Death Gate Cycle (by Margaret Weis and Tracy Hickman) has four worlds, one for each classical element... the air world is a space of floating islands with inconsistent rain... water is provided by a giant sky pump, a mechanical device that spouts water up into the air, created by the gods at the same time the world was created.

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    $\begingroup$ Feh. Gods who count on mechanical contrivances for their "miracles" aren't worth the price of the sacrificial victims. $\endgroup$ – Bob Jarvis - Reinstate Monica Feb 1 '17 at 17:32
  • $\begingroup$ @BobJarvis Surprisingly, that would be the theme of the entire series of seven novels! $\endgroup$ – SRM - Reinstate Monica Feb 1 '17 at 19:36
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    $\begingroup$ Again, feh. Gods who insist on creating worlds which are "rational" and "logical" and "based on a consistent system of physics and chemistry which are, with sufficient effort, intelligible by the beings created to inhabit the universe" are wankers. Turtles all the way down, sez I, and when the bloody humans start imagining there's some sense to it you drop a great bloody elephant on their heads!! Lazy bastards, I've no sympathy, really I haven't... (grumble-grumble...) $\endgroup$ – Bob Jarvis - Reinstate Monica Feb 1 '17 at 20:23
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    $\begingroup$ +1: was waiting for someone to mention the Death Gate cycle. This world is already featured in the first book. Should be useful as comparison material for the OP. $\endgroup$ – Oliphaunt - reinstate Monica Feb 2 '17 at 2:54
  • $\begingroup$ Don't forget about the Hargast trees; they're harvested for water on some of the islands $\endgroup$ – Izkata Feb 2 '17 at 16:46
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Water is a side effect of the hover mechanism

Each island has a gravity generator that causes it to float, located fairly centrally. The gravity generator's waste product is a stead flow of water... The larger the generator, the larger the island, and the larger the production.

Or Vice Versa

Alternatively the gravity effect is a side effect of some kind of portal technology, and all of the water sources generate a localized gravitic effect which causes the land in a small area around it to float. Larger portals feed bigger lakes/streams but also loft larger land masses.

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    $\begingroup$ If the floating mechanism is biological: ie microorganisms producing gas, the water may be a side effect. $\endgroup$ – user2259716 Jan 31 '17 at 19:16
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If the planet is a puffy gas giant, you could assume that it may have a moon made of mostly ice on the surface with a liquid core. That moon would be rotating around the gas giant relative to its shadow, always remaining cold on the surface.

As planet rotates in its orbit it causes a tidal pull heating up the moons core causing it to release its liquid water core over a given interval via geysers shooting hundred of miles into space.

The gas giant, being larger will be massive and have more substantial gravitational pull, therefore attracting the ice. Condensing and warming in the atmosphere it then rains down on the surface of the islands, collecting in pools creating lakes, waterfalls etc... As an added benefit, you get rings around your gas giant.

Reference: Saturn & Enceladus

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Reclaiming the humidity from the air.

I actually know someone who has a device like this in his house. Basically, it just condenses water from the (incredibly humid) air and keeps it in a small tank.

This is relatively simple technology, all you really need is to cool a sheet of glass or metal a little, and water will condense.

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Assuming air with high humidity you can catch the water with nets.
https://en.wikipedia.org/wiki/Fog_collection
https://www.newscientist.com/article/mg22229754-400-fog-catchers-pull-water-from-air-in-chiles-dry-fields/
http://news.mit.edu/2013/how-to-get-fresh-water-out-of-thin-air-0830
With lightweight nets (e.g.: carbon-fiber) you can do that in a large scale. It is also a unique feature, useful for a part of the story and/or the illustration on the cover of the book.

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Are these islands steerable? Or just drifting in the air?

The people could have terraformed the world by collecting water in pools on the islands from space, which eventually caused enough evaporation to start a water cycle and would create a core of water.

Condensing water would work, through plants or technology.

Or there could be a sort of water trade going on, whether they bring water from space (ice in meteors) or from people carrying water from the core up to the islands.

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  • $\begingroup$ You know, I like Ryan's idea too, that the core would be too hot, the water evaporates as it gets too deep, and would rise back into clouds and rain again. $\endgroup$ – jandsm5321 Jan 31 '17 at 18:31
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Each island simply needs a supply of hydrogen and oxygen, as well as an energy source. Binding hydrogen to oxygen to form water is a simple process. But, it is dangerous because hydrogen and oxygen are flammable. For example, the Hindenburg fireball created a lot of water.

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    $\begingroup$ That's not a bug it's a feature: the inhabitants could be burning hydrogen to generate energy as well as water. $\endgroup$ – Luke R Feb 1 '17 at 20:03
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Even if they are not big enough for their own water cycle, they still could be OK with water/rain from the planet itself (if this happens). As long as there is a reasonable amount of soil/absorbent material, then the floating island will be OK for a few weeks on its own in between rain showers.

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The islands are floating at rain cloud level. Every time they float through a cloud, they have a good chance of triggering precipitation (rain), similar to how mountains tend to encourage precipitation IRL.

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If you could let the “core” of your puffy gas giant be hot and dense (and therefore necessarily unpopulated), than it could propel warm saturated air into the upper atmosphere via either stable or volatile thermal currents. The water would condense and rain back down, to be caught in rivulets and lakes on the floating islands. As a side benefit, if you went with the volatile option, you now have an extra unpredictable hazard in your world. Perhaps the people have learned to predict these violent uprisings and move islands safely out of the way. Perhaps the people on the lower islands have developed technology to manipulate these thermal uprisings, thus bringing water to where it is needed, and holding it back where it is not.

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Is there a reason clouds similar to earth won't occur? If there are temperatures similar to earth somewhere in the mix of island, then clouds, storms and winds could still occur. As the islands are not fixed, this would be a lot more serious but clouds floating by an a gentle breeze could be harvested. If clouds or fog patches are common enough then they could be harvested for water by even simple setups.

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If it's a fantasy setting, and the islands float because of some magic or entirely different physics, it would be cool to have bubbles of water slowly drifting from the planet 'surface' to the outer layers of the atmosphere. Catch 'em with a net. If caught, they stop floating and behave just like water here in our world.

Maybe even make a water shell outside. Would be interesting to see the Sun shine through it.

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    $\begingroup$ Hello and welcome to Worldbuilding.SE! Nice start, but this question has the "science-based" and "reality-check" tags. These tags signal that the author does not want magic but things that are somewhat plausible. If you hover over the tags at the end of the question you can see their descriptions. You might want to take the tour and visit the help center to learn more about how things are handled around here. If you have any questions don't hesitate to ask. Have fun! $\endgroup$ – Sec SE - clear Monica's name Feb 2 '17 at 14:12
  • $\begingroup$ @Secespitus Right, didn't notice it. Well, then there are better, more realistic answers than mine, like water condensers or plants. $\endgroup$ – Anton Voloshin Feb 2 '17 at 16:06
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You could use technology currently available today.

Ingredients: 1 Oxygen, 2 Hydrogen, 1 fuel cell.

http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell.htm

A fuel cell converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity.

If I'm not mistaken, these fit the bill. https://www.buygreen.com/products/pem-reversible-fuel-cell?utm_medium=cpc&utm_source=googlepla&variant=3181636609&gclid=Cj0KEQiAzsvEBRDEluzk96e4rqABEiQAezEOoBJRRj_6y4mYPozErvoaD8Rwit9BQfOSoieG959rFN0aAs5X8P8HAQ

However you'll have to call the company to confirm and/or test them out before relying on them for the gas giant.

Unfortunately I don't have the reputation to comment on my own answer (nor is there enough room) in response to: "Note that using electrolysis to make the fuel cells takes more electricity than the electricity it will produce. – Anketam", so I'm responding here.

Anketam, thanks for your comment. First, note that electrolysis is not used to make fuel cells. Electrolysis of water produces hydrogen, which I presume is what you're actually referring to. Converting that hydrogen back to water may or may not produce less electricity than went into producing the hydrogen, but it does make sense as there are likely to be losses in the system. On the other hand, perhaps the scientists in the OP's world have perfected the system to 100% efficiency.

Second, note that the OP is seeking a source of water not a source of electricity. The electricity is simply a byproduct of producing the water. It's a bonus. Yes, it costs electricity to make water. Perhaps electricity is free on the OP's world.

Third, note that solar panels can be added to the system to generate electricity (and hydrogen/oxygen gases) during the day, and the hydrogen can be used at night and during cloudy periods to generate electricity and water.

In this configuration hydrogen functions as a battery in a sense. Obviously there are other ways to generate electricity as well such as wind for example so electricity is essentially "free" - after the initial capital investment of course and any ongoing maintenance which should be minimal. Perhaps volunteers donated their time to building the system and therefore cost nothing but their donated labor. Or not, as the OP chooses for his world.

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  • $\begingroup$ Note that using electrolysis to make the fuel cells takes more electricity than the electricity it will produce. $\endgroup$ – Anketam Feb 2 '17 at 11:28

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