In this world, there exists a type of material that has mass, but is incredibly buoyant in atmosphere. 1 kg of this material attached to 1 kg of any other material will be neutrally buoyant at sea level and act more like a beach ball than a large clod, excepting the effect of wind (it takes a lot of force to move more mass than a beach ball).

This material is available everywhere thanks to its incorrigible habit of bonding structurally and mixing with other materials and it is as common as most other forms of earth. Its buoyancy is logarithmic with respect to elevation so that even at the treeline on mountains it still retains something like 95% buoyancy, but achieves neutral buoyancy approximately in the range storm and rain clouds form and pass through, bringing it back to earth with the water cycle and re-bonding it to the now wet earth (this seems like a good way to keep it from both permanently floating up to where humans can't use it and from forming an opaque layer in the atmosphere, killing all plant life).

We'll call it floatstone.

A human analogue civilization has arisen on this planet and evolved to the point of approximately modern Earth humanity, including the ability to separate floatstone from other materials and form it into any shape we need it to be, much like clay. I don't think firing would be necessary, I'm envisioning a concrete like material, more curing to enable larger structural use.

How would modern city planning most effectively use this kind of material?

Would they float whole cities and place infrastructure underneath? Would they float individual buildings, chain them to the ground and join them by rope bridges? would it look much like our current infrastructure, just with the capability to build super high thanks to lighter bonded materials? Larger buildings and skyscrapers in relation to modern city planning are the goal, but including other buildings like factories or heavy industry would be great.


closed as too broad by Starfish Prime, elemtilas, A Lambent Eye, 011358 smell, Ash Jul 7 at 13:18

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    $\begingroup$ I don't think that immunity to the wind can work. If you think of a sailboat traversing the relatively low-friction surface of a calm lake, you will see that it doesn't take a lot of wind to move a comparatively massive object (the boat). Floating in the air, there would be even less friction so even less wind would be needed to move any air-buoyant object. When you neutralize an object's weight by bonding it to floatstone, you are making it into a cloud-like object and you better tie a leash to it before the wind takes it away. $\endgroup$ – Henry Taylor Jul 5 at 16:42
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    $\begingroup$ City planning uses a combination of cultural, economic, and policy inputs. For example, if floatstone is very expensive to use in construction then it won't be used much. We don't know the policy goals: Cheap housing, industrial development, stable neighborhoods, etc. And we don't know the culture of your not-quite-humans, perhaps they live in a tightly-regulated state of tiny apartment blocks or perhaps sprawling endless suburbs of large standalones. $\endgroup$ – user535733 Jul 5 at 16:51
  • $\begingroup$ @HenryTaylor I wasn't implying immunity to wind, just that it doesn't behave like a beach ball would when wind blows on it. A ship can move quickly, but it needs the wind's force to provide acceleration before it has the inertia to continue moving, just like the theoretical mass I've proposed. Beach balls require very little force to accelerate up to wind velocity. $\endgroup$ – Vashkarzas Jul 5 at 17:35
  • $\begingroup$ This question seems very broad, under specified, and judging by your comments on the answer below you already have some ideas about how this would work. You need to rephrase your question to be a bit more focussed. $\endgroup$ – Starfish Prime Jul 6 at 5:31

My first concern with such a material is how much does it clump with itself, and how does it react along the lines of dust-storm like conditions?

  • Based on your initial description, such a material's key impact on architecture may be to encourage cities to be based on low dome like structures that are Heavily reinforced... You know, to avoid serious damage to them by the giant multi-tonne boulders that travel across the ground like massive terrifying tumbleweeds of doom...

Assuming Bouncing Blundering Boulders of Bashing aren't actually much of a problem, then long term impact on architecture is unlikely to be hugely impacted for the most part.

  • Lighter materials may increase early 'Sky Scraper' development by decreasing some structural loading when stone and brick were still playing a big role in construction, but wind forces and swaying actions become far more of an issue than anything else as you start to get higher than current average buildings in cities.
  • Large 'floating cities' that aren't solidly tethered to the ground would face issues with transportation and basic services/resources. Getting water and power to a floating city is a non-trivial issue - You can't just lay a pipe or run some wires to them...
  • There are also major risks to huge volumes of mass floating around: They'll be hard, if not impossible, to control if you build them too large. They'll be strongly under the influence of storm weather pushing them around. Most people probably wouldn't want to invest in 'land' that might run itself into a mountain... Think of what happens when a ship runs into an iceberg, and scale things up? [That said, floating islands for the rich and powerful may still be a thing.]

Key problems to 'going tall' are in getting people/water/stuff up and down, and not having the things blown around by the wind. Humans have this odd tendency to complain when their buildings start swaying around like ships on a heavy sea...

  • $\begingroup$ I was envisioning something like Hengsha from Deus EX. Multiple vertical tiers of city, each with their own infrastructure, bonded together through a 'plates' made of a material that relies very little on the structural integrity of the city supporting it. Maybe I should make that a different question... $\endgroup$ – Vashkarzas Jul 5 at 17:41
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    $\begingroup$ It would be a useful material for such a structure concept, but you would still face the lateral-force issues [so build a 'pyramid'] and utilities logistics. - Piping water up massively tall buildings tends to be the greater engineering feat than just getting a structure up that tall. Engineering gets weird when you go to extremes. $\endgroup$ – TheLuckless Jul 5 at 17:47
  • $\begingroup$ They would only have to pump it up there once, to create a freshwater reservoir sitting in the plate above, which can be used either as ground source for the city above the plate, or like a massive water tower for the city below it. Thinking about it, all water towers would benefit from this process, essentially having freshwater lakes floating around. $\endgroup$ – Vashkarzas Jul 5 at 17:58
  • $\begingroup$ @Vashkarzas: Don’t forget the elevator problem! Getting food into/waste out of the upper tier cities will be tricky to say the least! $\endgroup$ – Joe Bloggs Jul 5 at 18:12
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    $\begingroup$ @JoeBloggs getting waste out of tall buildings is straightforward. Keeping the neighbours on a lower tier happy at the same time on the other hand... $\endgroup$ – Starfish Prime Jul 6 at 5:30

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