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The Utopians are a wise and benevolent civilization with Ancient Rome-like technology. Unfortunately, they are so peaceful that they are constantly on the verge of being conquered by the neighboring and envious barbaric tribes.

So the Utopians prayed to their gods and they looked with favor to the poor mortals. And the Utopians were all raptured to the skies on Tolkien-like eagles and were given the magic substance: Handwavium.

When Handwavium is dropped on a cloud, the cloud becomes solid. It doesn't change shape anymore and you can walk on it and build with it. It also becomes fertile with handwave fruit trees and eddible handwave cereals. However, it still keeps afloat somehow.

The Utopians rejoice and start building their new city up there on a cumulus on the lowest étage (ca. 1.900-2.000 m high).

Unfortunately, they soon find the gods' blessing to be a curse. Even though they built their city on the lowest étage, it seems that all the rain falls from below their altitude, not from above them (I may be wrong on this one... if I am, please tell me, for I would like to be wrong), so they can't collect rainwater.

Handwavium, OTOH, has poisoned the water on the cloud they built in, so they can't collect water directly from their own cloud.

Also, as a roman-like civilization, they were very savvy on building aqueducts... but water doesn't flow upwards, as you all know. Using Archimedes' screws or drums lifted with cranes from that altitude is impossible and would never be able to supply a whole city.

The gods, when questioned, just shrug and say: "You can't wish for more wishes".

Is there any way to save Utopia from abandonment or catastrophe, all by the Utopians own devices?

Some help: There is a slight possibility that Handwavium may make the cloud a little heavier and so the city could drop some meters... how much of a drop would suffice?

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    $\begingroup$ how is the water poisoned exactly? Can it be filtered/boiled? $\endgroup$
    – depperm
    Jan 6, 2017 at 21:30
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    $\begingroup$ Basically I put the "poison" as a way to make people not consume the water from their own cloud. Any water must be collected elsewhere, on other clouds or from the ground. $\endgroup$
    – Pedro Gabriel
    Jan 6, 2017 at 21:34
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    $\begingroup$ I'm surprised you wouldn't want them to live on a cumulonimbus cloud instead? After all they are literally awesome and huge. Fit for an epic city... $\endgroup$
    – AngelPray
    Jan 6, 2017 at 21:48
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    $\begingroup$ Because then they would be even further away from the rainfall altitudes... $\endgroup$
    – Pedro Gabriel
    Jan 6, 2017 at 21:49
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    $\begingroup$ You are aware cumulonimbus clouds usually extend the whole cloud layer? In addition near the bottom they are often flattened out(the buttom existing at the same elevation as a typical cumulus cloud btw). it would essentially be the equivilant of a city being build around a mountain or hill(which is very often where cities are actually build), with room to have temples/forums higher up. $\endgroup$
    – AngelPray
    Jan 6, 2017 at 21:59

4 Answers 4

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You are wrong.

Your civilisation is far from doomed.

Clouds don't follow a strict layering system. Even though you are correct that precipitation generally occurs at lower elevations, cumulus clouds (which are one of the principal type of clouds that give rise to rain) and which do indeed exist at the lowest part of the cloud layer can quite literally fly on top of each other when pushed by complex wind currents (which often cause rain to be produced at the same time).

Being that the surface of the cloud presumably wouldn't be absorbing much of the water, even if this wouldn't happen that often, depending on the size of your population, this could be enough to account for all your water needs.

In addition clouds, (including cumulus clouds) often "bump" into each other (especially with cumulonimbi, because you know, they are massive). You could quite easily collect part of these clouds, with technology no more sophisticated then a bucket. If you want this to be more efficient you can simply have a system of thick cloth sheets blowing in the wind, being controlled by pulleys to harvest the water content.

Because of all this, being able to provide enough water for your city is not an actual issue (I mean we are dealing with cities of antiquity, usually having no more then a few hundreds of thousands inhabitants).

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    $\begingroup$ "You are wrong". Me: Yay! $\endgroup$
    – Pedro Gabriel
    Jan 6, 2017 at 22:20
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I thought they'd be getting snow from higher clouds, not so? Even if no snow, all's not lost. If the solidified cloud moves relative to the air around it, then local humidity could be condensed out of the air. (I'm not saying they'd figure out how, without lots of help or lucky accidents, but still possible.

Three key conditions:

  1. Source of power to condense ambient humidity. Extracting liquid water from ambient air takes power, and lots of it. From
    https://en.wikipedia.org/wiki/Enthalpy_of_vaporization we have just over 40 kJ per mole; and a mole of water masses just 18 grams (just over a tablespoon.) They can't use water power (irony), nor can they dig coal. Burning biomass is one option, but relative wind (see below) would IMHO be cleaner/nicer.

  2. Relative motion is needed to access a steady supply of (still somewhat humid) air to de-humidify. So long as there's even modest (few Km/hour ?) motion of the solidified cloud, relative to its enclosing air layer, then we're in business, at least air-supply wise. But if the cloud moves right along with the local air (essentially no relative motion), then the local air will soon be stripped of moisure, making it much harder to get any more (modulo diffusion of gaseous H20.)

  3. Do they have enough metal and metal-working skill to make something like a steam engine? (Actually an air compressor plus a few more bits.) Off hand, all the feasible heat engines I can imagine them building -- at the power levels they'd need -- would need either metal or exotic ceramics.

If they can't address 1 -- 3, I think they'd better start working on growing fiber for a long, long descent rope.

Although solar cells plus Peltier-junction (solid-state) refrigeration
https://en.wikipedia.org/wiki/Thermoelectric_cooling
would work very well indeed, up there above the rain clouds, the high-tech/green energy option just doesn't fit with this culture and would be really improbable.

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  • $\begingroup$ Thank you for your answer. However, I think it would be too complex for the Utopians tech level to develop such solutions. $\endgroup$
    – Pedro Gabriel
    Jan 7, 2017 at 14:56
  • $\begingroup$ I know that a tech-based solution would be a long shot, but it's the most nearly plausible answer I can offer. That said, I hope you/somebody offers up a workable solution, since I truly like the idea of these folks having to recover from a blessing with a hidden curse. $\endgroup$
    – Catalyst
    Jan 7, 2017 at 15:00
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You say they have fruit and plants. Where do these get water from? If it's magic water, they can squeez it from the fruit and plants and have an unlimited supply. If not, then their water problems should also extend to food.

Lowering a bucket during a rainstorm might get them a bit if water. The ropes wouldn't have to be all that long. Lemme do the math and get back to you...

OK, buckets are hard. Average global rainfall is ~1m, so 1 square meter bucket will collect ~35000 oz of water per year. Average American drinks 7000 oz, and that doesn't count bathing, etc. Crops can probably be watered with urine so at least that helps the crop watering problem. But yeah, every square meter of hanging bucket area allows about 5 people to survive (more if your world has more rainfall, less if they like to shower). Not impossible, but difficult.

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  • $\begingroup$ I wanted to build this city step by step. This thread should be solely about water, not food. The handwave fruits and cereals serve to focus the answers on the water issue, not the food issue. So you can't extract water from the food. $\endgroup$
    – Pedro Gabriel
    Jan 7, 2017 at 14:52
  • $\begingroup$ As for the buckets, as you said, they are not very practical to supply an entire city. $\endgroup$
    – Pedro Gabriel
    Jan 7, 2017 at 14:54
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You could try to "harvers" the cloud directley. Because the cloud is made from water.

Move you're cloud close to an other one and try to extract the water from it.

This way, you have access to water, without having to lower your vloud ore have it rained on.

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  • $\begingroup$ "Move you're cloud close to an other one and try to extract the water from it." - the million dollar question is: How? $\endgroup$
    – Pedro Gabriel
    Jan 7, 2017 at 14:56
  • $\begingroup$ @PedroGabriel - To answer your first question. If you can build a city on it, you can build at least a sail (to sail you cloud somwhere else) $\endgroup$
    – Frezzley
    Jan 8, 2017 at 0:18
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    $\begingroup$ @PedroGabriel To answer your second question. You can imagine a cloud just as fog. And they sre currently developing a sistem to extract water out of fog (to use it in the desert). - Thats how you do it. $\endgroup$
    – Frezzley
    Jan 8, 2017 at 0:20
  • $\begingroup$ @PedroGabriel - The Method is called "fog harvesting" you can read more about it here:google.ch/amp/phys.org/news/… $\endgroup$
    – Frezzley
    Jan 8, 2017 at 0:22
  • $\begingroup$ Roman Era technology is not so good for collecting fog. $\endgroup$
    – Nosajimiki
    Jun 18, 2020 at 2:55

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