Hot answers tagged

164

Low-tech climate control: the waterfalls fill the air with spray, which evaporates off and cools the populace. The Romans used to achieve a similar effect with fountains.


125

Still water is heaven for proliferating algae, bacteria and annoying insects like mosquitoes. A large city with large bodies of still water is a recipe for plague spreading. Having water on the move keeps the water clean and, as a consequence, the city healtier. Also, waterfalls help enriching the water with oxygen, helping bacteria to decompose organic ...


74

In order to get water up to the top of a building, you can either carry it manually, or you can pump it. Pumps don't have to run on electricity. Wind-powered pumps use a windmill to power the pump, and have been used since at least the 1500s (and likely much earlier) for irrigation and other purposes. Other options like steam power, diesel, or water wheels ...


70

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). This plant converts air humidity into water with the help of its hairy leaves. It then gathers ...


70

Energy storage. You use a form of energy generation with unreliable or periodic output. As a form of energy storage you pump water up into a nice big reservoir when you have surplus, then power turbines by letting the water spill back down to a lower reservoir to create a more steady power supply. It might be more efficient in an enclosed system of pipes, ...


65

You can't control your direction in a sailboat when there is just one current. Sailboats are only able to move into a different direction than the wind is blowing because they have a "second sail" under water, called a keel. The actual physics on a sailboat are a complex topic. But the bottom line is: When the aerodynamic force on the sail and the ...


64

You won't be able to have this in a universe that uses our physics. The degree to which space itself expands or contracts is related to the cosmological constant and the density matter within that space. A universe full of water is going to have an insane matter density. Which can be balanced by a large cosmological constant. The problem arises in that ...


59

You're looking at it backwards. Nobody added artificial waterways to a city. They did what they had to do to support building a city on top of existing waterways. Human settlements naturally spring up near water sources for a number of different reasons. An annoying drawback of these water sources is that they limit the settlement's ability to expand. ...


58

Yes, this is possible. The ball of water could be kept in place with equally spaced air fans to nudge splashed water back from all directions. However... At 10 metres across (5 metres deep) there is a serious risk of drowning. In 0g, the adhesion of water and slight difference in density will cause suspended objects ("swimmers") to be enveloped and drawn ...


57

There is a 0g pool available for the guests. I want it to be a large ball of water 10m in diameter. Can it work? I don't think you can make this work as you've envisioned it. Let's look at some of the issues: Newton's Third Law When swimming, you push against the water and the water pushes back on you. You go forward, and the water goes backwards. Water's ...


54

The oldest pump in historical records is the force pump. The book that first describes it was written between 15 and 30 B.C/B.C.E. This is the Archimedes's screw, which is one of my favorite ancient machines. It was used for irrigation. These could be arranged within a building's staircases. And then there is always the classical bucketwheel. All of the ...


52

No, at least not with classical trees. A tree can be defined as a woody perennial plant, typically having a single stem or trunk growing to a considerable height and bearing lateral branches at some distance from the ground. Branches with leaves can't be dense enough to hold water, as this would defeat the purpose of the leaves on the trees. A leaf ...


51

What is the closest I can realistically have my spring to the ocean? 0 meters When, as a kid, I went to the sea during summer, it was common knowledge that, in some places along the coast, there were springs pouring fresh water directly into the sea. One could tell it by both the sudden drop in temperature, especially with calm waters preventing mixing (...


49

Depending on the temperature you are exposed to, you can go 100 hours without drinking at an average temperature outdoors. If it’s cooler, you can go a little longer. If you are exposed to direct sunlight, it’s less. (source) Which is a fancy way of saying almost everything on land is dead, and that's just the beginning Even life in deserts depends on ...


48

In medieval times, this was given quite a lot of thought as castles were designed in most cases to survive a siege. Food is an issue during a siege to be sure, but water more so; this ties into the law of 3s; you can survive 3 minutes without oxygen, 3 days without water and 3 weeks without food. These are of course approximations, but you get the general ...


42

Reverse osmosis. from Aristotle, Meteorilogica. There is more evidence to prove that saltness is due to the admixture of some substance, besides that which we have adduced. Make a vessel of wax and put it in the sea, fastening its mouth in such a way as to prevent any water getting in. Then the water that percolates through the wax sides of the ...


39

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 ...


39

Rocking Your continent is floating. Maybe it is rocking back and forth as it floats. That can happen with floating things. Any number of forces can put a body into an oscillating motion. As your continent rocks back and forth the water contained in it will flow back and forth, moving toward the low side. I could imagine the rocking being subtle ...


39

Water volume isn't a problem. The mass is the problem. Your body is somewhere around 60% water. This means even a perfect water storage mechanism can only be about 66% more efficient. You can't even double your water storage per body-mass. This is why water-efficient creatures typically focus on conserving water rather than trying to store more of it. ...


39

You can build a solar still using nothing but pottery tubes, sealed with asphalt or similar. A single unit (different design) can produce as much as five liters per day. For continuous production, the main "unit" is a large tube with two tubes inside, the upper one being half open. The upper tube is filled with slowly moving salt water, that evaporates and ...


39

Do it like it's done on Earth Using filters and machinery is useful when you need it fast or compact but on a generational ship, it's materials you can't spare. You need garden/agricultural areas for oxygen and food. Human waste water is good for growing plants. Said plants absorb the water through the roots and expel as vapor through the leaves which then ...


36

You've experienced water flying through the air at its eventual maximum speed. Rain. This is water at its terminal velocity. Gravity is trying to constantly accelerate the falling water, but that force is matched by the wind resistance and the water will not go any faster. Starting slow, it will reach that speed. Starting fast, it will reach the same ...


36

What you need is much, much lower terminal velocity for raindrops. Using mathematical terms, terminal velocity—without considering buoyancy effects — is given by$$ V_\text{t}= \sqrt{\frac{2mg}{\rho A C_\text{d} }} $$ where $V_\text{t}$ represents terminal velocity, $m$ is the mass of the falling object, $g$ is the Earth's gravity, $...


36

It is very possible. It's been done. The wheel itself can clearly be made out of wood, as many are even in societies that have metal. The axles and gears that transfer the rotational energy are usually wood too, though sometimes with metal fittings or casings so that they will wear down and need replacement less quickly. The milling surface itself can be ...


33

It will be WAY harder than it sounds Not sure if you've ever seen these floating lilly pads at any public pools, but they work more or less as described. The below body of water is completly still, and even with a net above you to hold on to, those things move around like crazy making them impossible to walk on without the overhead net. The problem you will ...


32

You need to have direct sunlight that can be dispersed to see a rainbow. If you have only already dispersed light, no rainbow can occur. If you have a permanently cloudy atmosphere (like it is the case on Venus), there never will be direct sunlight, and thus no rainbows. If you need a solid physical explanation for it rather than a handwaving "different ...


29

If ice did not float, Snowball Earth would have had a bigger effect on life ( when after great oxygenation it was not enough CO2 in the atmosphere to keep Earth warm enough and, according to some theories, the entire surface of Earth was covered by ice.) But it is quite possible that life could survive anyway around underwater volcanoes and in areas of ...


29

The idea of an ocean planet isn't too far-fetched. There are several moons in the Solar System - Enceladus and Europa, for instance - that have subsurface oceans. If the ice covering their surfaces melted, they'd be just what you're looking for. Extrapolating that to a larger, planetary-mass body isn't too hard. Creating an ocean planet isn't too difficult: ...


28

Steam it up with a solar concentrator. This London skyscraper can melt cars and set buildings on fire The building — designed by internationally renowned architect Rafael Viñoly — is a dramatic edifice with curved exterior walls. Built at 20 Fenchurch Street in London's financial center, the 38-story skyscraper is known locally as "the Walkie-...


28

Your question already contains the answer: There's a facet of my magic system that uses a certain kind of crystal to create water out of the magic energy stored within. The amount of magic energy that can be stored within a crystal is the natural limitation for the amount of water that can be created using this crystal. If you want to make the system ...


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