I'm sure that this has been asked before, but I need floating islands for a fiction story I'm writing. It takes place 5000 years after a catastrophic event (on a vaguely earth-like planet populated with humans) that shrouded the surface of the planet in a continual fog of toxic, biochemically unstable gas a few kilometres thick.

Due to one reason or another, several thousand chunks of land were torn from the planet's surface and thrust into the upper atmosphere, carrying a few humans along for the ride. So, here is my question:

How could these landmasses be held in place for significant millennia without magical magnetic crystals or anything that breaches the realm of reality? The bending of physical laws and space-time continuum stuff is all fair game though.

  • 5
    $\begingroup$ Sorry, I can't see how this would be possible without magic. You can have a planetary ring system (like Saturn), but not in the upper atmosphere (drag causes the orbits to decay, and the islands crash). Similarly, having "bubble" atmospheres around each island is impossible (air molecules escape into space) without some kind of pressure vessel, like a huge dome around each. Would that be acceptable? Also, "bending physical laws" is usually considered "magic" here, so perhaps you could be more specific on what is allowed and what isn't. $\endgroup$ – type_outcast Jan 17 '16 at 7:09
  • $\begingroup$ Do you mean like satellites ? Why not the moon ? $\endgroup$ – Kii Jan 17 '16 at 11:53
  • $\begingroup$ Skyloft anyone? $\endgroup$ – Quiquȅ Jan 17 '16 at 16:41
  • $\begingroup$ Is it a natural phenomenon? Do you want the islands to be flying immediately following the catastrophe or can they be artificially maintained? $\endgroup$ – SilverCookies Nov 8 '17 at 20:33
  • $\begingroup$ How is bending physical laws not breaching the realm of reality? $\endgroup$ – sphennings Nov 20 '17 at 15:48

14 Answers 14


Perhaps you could utilize the phenomenon known as flux-pinning.

As explained by Game Theory's "Why Living on BioShock Infinite's Floating City Would Suck!" video,

"A superconductor is a material that, when cooled below a certain critical temperature, is able to conduct electricity with a zero energy loss. In other words, if I added some electric current into a superconducting wire and remove the power source, the electricity would continue to run through the wire forever."

Warning: this video seems a bit inappropriate for some viewers, though the science is nothing to sneeze at. The explanation of how flux pinning is utilized in the game is from around 1:39 to 5:09 with a nifty real world example at 2:36.

When a magnetic field is placed underneath the superconductor, the latter creates what is known as the Meissner effect, causing the magnetic field to bend around it. If the superconductor is thin enough, however, the magnetic field is able to penetrate through it in minuscule amounts known as "flux tubes".

"At such low temperatures, the flux tubes become pinned and can't move"

and the "low temperatures" are attributed to liquid nitrogen, as stated

"if [Columbia] were to really exist irl, we would need enormous tracks of magnets on the ground and lots of liquid nitrogen to keep the floating discs cool."

However, this brings up an important point: where would the magnets, superconductors, and liquid nitrogen (or some other method of cooling the conductor discs) come from? I'm not sure if the toxic gas of your world could cut it alone as a potential cooling system. Possibly, the "several thousand chunks of land" you mentioned were above an area of scientific research that possessed such materials before being uprooted. (Edit: part of this issue could be resolved by a theoretical room temperature superconductor as suggested by celtschk.)

Other points to consider, as brought up in the video, are the freezing temperatures resulting from the cooling system and effects of the lack of air pressure on your original inhabitants (speculated to be ~4.5-6 km above sea level). I'm sure there would be a lot more than ear popping happening on the ride up. Over time, though, your humans will likely become acclimated to the high altitude. On the other hand, they might become nauseous if they become fixated on the clouds (and try to move). As the video mentions, the movement of clouds past the islands, giving their bodies the illusion of being in motion, would cause their systems to go into disarray and give them visually induced motion sickness. In order to counteract this, the humans could construct exterior panels of some sort to (mostly) block the clouds from their vision, also having an effect on their society (i.e., "keep your eyes on the city" and "bird watching is the sport of the ill"). (Edit: Ville Niemi corrected parts of the original version of this paragraph)

Good luck with your story!

  • 3
    $\begingroup$ No exterior panels are needed. The visual system only gets it wrong if it has nothing static to fix on, ie you only see the clouds. And it only causes nausea if you try to move at the same time. So as long as you look where you are going, which is probably not a cloud, you'll be fine. And "air sickness" is caused by being in motion while it looks you are not. You do not get it from floating in place. So it is actually the inverse form of the same mismatch. $\endgroup$ – Ville Niemi Jan 17 '16 at 9:58
  • 1
    $\begingroup$ See also this answer. Nice to see someone else who's a fan of flux pinning! $\endgroup$ – JDługosz Jan 17 '16 at 10:06
  • 4
    $\begingroup$ The liquid nitrogen could be avoided by claiming a room temperature superconductor. $\endgroup$ – celtschk Jan 17 '16 at 13:18
  • $\begingroup$ Thanks for all your help. This really clears up a few things in terms of the story's physics and adds some unique cultural changes I didn't think of. ^^ $\endgroup$ – Mr. Question Jan 17 '16 at 21:58
  • 1
    $\begingroup$ I wonder, if you had a planet with a really strong magnetic field, like Jupiter's, which is 10 times stronger than Earth's, if you could do away with the magnetic tracks and just float on the planetary field. Alternately, the tracks could be naturally formed loadstone... $\endgroup$ – AndyD273 Jan 18 '16 at 18:08

You want an airship.

Tungsten Hexafluoride has a density 11 times that of air (and certainly fulfils the toxic criterion) - so an airship should be very possible using normal air as a lifting gas. Unlike a normal airship, the lifting gas would be breathable; meaning that you could actually live in the envelope of the airship. Make the whole thing out of aluminium and clear polythene and fill with lots of plants - on a large enough scale, you have yourself a closed ecosystem.

Gas loss would be an issue (although the rate would of course be slower the larger the ship is) - your best bet would be to send machines down to the surface to mine it for minerals that can be used to generate oxygen and nitrogen to balance the loss.


Excellent! Take a gander at Buckminster Fuller's idea for a floating geodesic dome city. He called it Cloud Nine, and it seems like a great slice of near-reality fit for your story.

A half mile (0.8 kilometer) diameter geodesic sphere would weigh only one-thousandth of the weight of the air inside of it. If the internal air were heated by either solar energy or even just the average human activity inside, it would only take a 1 degree shift in Fahrenheit over the external temperature to make the sphere float. Since the internal air would get denser when it cooled, Bucky imagined using polyethylene curtains to slow the rate that air entered the sphere. He wanted to build Cloud Nines and anchor them to mountains, or let them drift so their inhabitants could see the world. One of the more practical uses he proposed for them was as disaster sites for emergencies.

Excerpted from http://www.geniusstuff.com/blog/flying-cities-buckminster-fuller/

Essentially, it's Archimedes' Principle on a grand scale.

Anyone versed enough to do proper calculations?

  • $\begingroup$ Unfortunately, such a device would have to be constructed. Chunks of earth/rock which were thrown into the atmosphere by a natural event would not be hollow spheres. They also could not be heated enough before falling back to the ground. $\endgroup$ – Annonymus Jul 27 '16 at 10:29
  • $\begingroup$ Considering, how many amazing things the nature did manage to construct (nuclear reactor, eh), I'm sure there is a way this could happen. Some sort of a glass-blower super-volcano maybe? Gotta think about it. $\endgroup$ – Alice Nov 3 '17 at 16:11
  • $\begingroup$ @Annonymus - what if the dome-cities already existed before the catastrophe (including some form of thermal regulation and controlled air intake/release) and were quickly "re-purposed" when disaster struck? You can have one group of scientists realize that by reversing the polarity of the handwavium generator you could achieve buoyancy, transmit this discovery to all cites, and have a small portion of them succeed in making the adjustments in time. $\endgroup$ – G0BLiN Nov 8 '17 at 14:52
  • $\begingroup$ One way to get something close would be for the toxic gas or a precursor to it to form strong soap-like bubbles to which mud would adhere. With exposure to the sun and air, the mud turns to sedimentary rock with big fissures in it, and if something caused the gas in the bubbles to be sucked out, forming a vacuum, you get lots of floating spheres and bubble-cluster shapes made out of rock that could float in the sky. $\endgroup$ – ohwilleke Aug 5 at 0:56

The closest Thing I can come up with is: Produce a gas with has a density slightly less than water ($\approx 1000kg/m^3$) and release it $5000$ years ago slow enough that the people who already lived on the planet could build gigantic "ships". Light material like wood can swim on the gas, while water and humans will fall thru it. Make the "ships" big enough to carry landmass, maybe use mountains how a tall enough to not get covered.

But there comes several problems.

  • You need a density of about $950kg/m^3$. I don’t' know any gas with nearly that density under normal pressure.
  • You need a lot of mass to fill a few km with this density. That will need some serious scientific break thru.

$\text{mass} = \text{density}\times\text{volume}$ $\text{volume}\approx\text{volume}\space\text{sphere gas surface} - \text{volume water level volume sphere} = \frac{4}{3} \pi \times r^3 \text{with earth radius} \approx 6300\text{km} -> 1.047\times 10^{12} \text{gas 5km above ground} r \approx 6305\text{km} -> 1.049\times 10^{12}\text {difference} 2,495 \times 10^9 \text{estimate 950kg}/m^3 -> \text{mass} = 2,371\times 10^{12}\text{kg or} \space 2,371\times 10^9 t$ And in reality it will be even more cause you need more gas for this height cause of raising pressure level.

  • The Air will get thin even when you climbing high mountains ~5 km above water level can get hard. Mountains on earth go up to ~8km. So the planet must be flatter then earth or you may want to allow some original landscape.
  • If you don't change the climate in the progress it will be vary could ~5km up. In the real world there is a treeline at about ~4km over see height. And since your people will likely depend on trees that’s a problem. So we need some serious green house effect while producing gas.

With all that I don't see how we can get any closer with real world since.

  • 1
    $\begingroup$ Please note that the site has LaTeX enabled for mathematics. $\endgroup$ – HDE 226868 Feb 7 '16 at 15:38
  • $\begingroup$ won't the air float above this new gas? So you'll have the earth's crust, then water or continents, then a layer of new gas, then a layer of air. Even though the bottom of the air layer is a mile (or whavever) above sea level, shouldn't its thickness (and therefor air pressure at the bottom) be the same? $\endgroup$ – Daniel Bensen Nov 9 '17 at 10:11
  • $\begingroup$ the floating mass could be foam-stone, like volcanic tuff. $\endgroup$ – bukwyrm Apr 19 '18 at 17:51
  • $\begingroup$ @radogar: I put your math in LaTeX/MathJax format. You can rollback if you want to, but I'd suggest keeping it like this to make it a bit more readable. Please take a look at it both in regular format and in edit mode. Hope this is fine by you. $\endgroup$ – FoxElemental May 8 '18 at 18:17

How dense is the toxic gas? Could the gas be dense enough to cause a suspension between the upper "normal" atmosphere and the lower contaminated atmosphere? Perhaps the floating land masses are comprised of low density volcanic rock that "ride" on the surface of the gas volume? Perhaps contributing to the phenomenon are deposits of an exotic element (it isn't Earth, you said "Earth-like") that have anti-gravitational properties when exposed to oxygen. A sort of comedy of coincidences that could only occur on an alien world.

  • $\begingroup$ This would be a better answer if it explained what the heavier than oxygen, nitrogen, and carbon dioxide gas was. As is this seems most like a water world. Stuff can float on water. People can't breathe water. But people can travel through water. Comet storm as an initial cause? The icy shell melts off, leaving a hard core to cause damage and water vapor to rain down and make groundwater. $\endgroup$ – Brythan Nov 4 '17 at 17:48

Use Plants:

This changes up your premise a bit, so take it or leave it. Instead of blasting chunks of the planet into the atmosphere, say that some plants evolved to hold sacks of lighter-than-air gas, allowing them to float. Over thousands of years, these plants would grow together into large floating "islands", the interiors of which are mostly just lifting gas.

These islands couldn't hold up much besides their own weight, so no huge stone castles or whatever. However, depending on the size of the islands and how "deep" they go, they could maybe hold some human inhabitants. Weight matters a lot here, but you can probably fudge it by saying that the plants are unrealistically light, and the gas is unrealistically "lift-y".

These islands would need to exist before your catastrophe. Or, if you want, the catastrophe took a long time to happen (think: global warming), which is why these plants evolved to float in the first place. Either way, your humans would then need a means of getting up onto these "islands", but that's another story.

  • $\begingroup$ If these are separate plants grown into one mass, wouldn't the plants over which you built your castles or even just houses die for lack of sunshine to continue their photosynthesis? $\endgroup$ – Real Subtle Nov 10 '17 at 9:41
  • $\begingroup$ @RealSubtle It doesn't really matter if they die, just as long as they still hold in the lifting gas. Biologically this might be tough, but just say that they degrade differently, or the outer plants hold in the gas from the inner ones. $\endgroup$ – Bert Haddad Nov 13 '17 at 18:22

Here's a thought: We could say that the Earth's gravity was weakened, causing the Earth's centrifugal force to crack and separate the earth.

When this happens, all the oceans would be drained into the molten core, forming huge vapor clouds in the sky, giving the new humans a new water source.

As for how the islands would float, all I could think of is that the intense heat of the core would keep the islands afloat. But that would mean that the heat would kill a life. So I'm not sure if there is anyway to cool the core enough to keep the islands afloat while not cooking a life on the remaining Earth.

I'm not a scientist or a science expert, just a writer with some ideas. Need help from scientist to back me up.


Not out of rock collected from the surface and with current technology. Matt Bowyer's comment was devised by Geoffrey A. Landis to build floating cities on Venus.


What if the race that destroyed the planet was into some crazy science stuff. They found a way to tune the gravitational attractiveness of matter. Whole mountains could have been made neutrally buoyant by flipping half of the matter to gravity repelling material. Or simpler yet set to gravity neutral. That'd be some weird stuff. It'd still have mass so it would be hard to move around but it wouldn't fall to the surface if it broke off. It'd kind of drift away behaving as if it was in zero gravity.


Well if a Harrier can hover in air why not something larger which is really what you're asking. Of course it's possible just need the right sort of technology that can manipulate air not really gravity it's the same system as getting something to float on water with even distribution across surface.

With air it is lighter but that doesn't mean planes don't fly. People who believe otherwise are thinking Like those of times who thought it was impossible for anything to fly other than creatures like birds. Then we invented planes plus there are minds of fuel that keep on going to sustain it. Air itself can be used as well as solar energy by day and can alternate between the two.

If we are defeatist in the face of problems we would never have achieved the kind of scientific advances we ever achieved it's not impossible. It just hasn't been done because of costs and resources, same as we haven't built domes on moon or Mars with any urgency. Because we know of the dangers to human extinction. If anything ever happens to our planet, it doesn't mean we can't. It's because humanity can be lazy when it comes to urgency for things that aren't deemed necessary by governments and so on.

  • $\begingroup$ Welcome to Worldbuilding, Mark, a thoughtful answer you've put some effort into, but it does need improvement. Can you please edit this "there are minds of fuel that keep on going to sustain it"? It is obscure in its meaning. The Harrier is a VTOL aircraft, the question is about levitating chunk of land & how to keep them up there. If lumps of land were turned into hovering aircraft, your solution is plausible. The question itself seems to have a different scenario requiring a possible mechanism for long-term levitation. Apologies for being a grouch. Have fun here! $\endgroup$ – a4android Nov 3 '17 at 1:25

Ok, no natural magnetic solution. (somehow missed that when I read the question the first time DOH!)

Assuming that the catastrophe had a long build up before it happened and the islands were torn from the surface.

Using a force field that returns an equal force against whatever was applied against it but in the opposite direction would allow for the islands to float by effectively nullifying the downward force of gravity if the force field was deployed on the underside of the islands.

The power supply for the force fields to work can be the provided by the force field itself by increasing the returned force and diverting it to perpetually power the force field nodes.

The force field nodes would have a minimum size of island that could be kept afloat as the downward force of gravity on a small mass would not be enough to nullify the gravitational effects to keep the island far enough above the toxic cloud layer.

Conversely larger islands would have no issues beyond the requirement to calculate the number of nodes required to maintain a certain altitude above the toxic layer.

Adding the ability to moderate the output of the nodes within certain limits would also give the islands a limited form of guidance.

Warfare between the islands could evolve to being about gaining control of the force field nodes. The ability to lower an enemy island in to the toxic layer that would kill most of the inhabitants and then to raise the now depopulated island back above the clouds would be the equivalent of neutron bomb with limited if any damage to the infrastructure.

Time dilation would, in my opinion, be difficult to use as any effect that would say, slowed down the fall of the islands, would also effect people living on the islands so whilst it make take 5000 years for the island to fall 10 feet, to the inhabitants it would still only be experienced as a microsecond, so not very helpful. Again unless the time dilation effect could be focused in some form like the force field example to almost freeze the islands from moving. This would probably also mean the islands were fixed points geographically and did not move, this second point would make the continuation of civilization easier as communications links between islands would be easier if they're not moving around.

The Ancients did it.. it's been 5000 years, perhaps the decedents of the original builders of whatever device keeps the islands flying have lost a large amount of the information on how it was done, knowing only that the Ancients had great powers and made the world as it is. This could happen if communications between the islands was not possible due to the catastrophe, also islands with small populations my suffer from inbreeding which could cause a lose of the required mental ability to understand the methods used.


On an Earth-like alien planet, much can be different. Weird things can and do happen.

You can introduce a new element into your world, say Floridium, a substance that is like a solid form of helium. The molecule has a specific gravity that is, say, 4 times lighter than the poisonous gas which is very heavy 6 times heavier than air. Floridium can only become bonded chemically in the heated interior of the planet, where it is normally trapped.

When the earth cracked some of this substance worked its way out of the rocks. Floridium with rocks still clinging to it sink in the poison but other chunks free of stone and life float like a boat upon the ocean. While others float like icebergs.

See, you can make your own elements that don't exist and you suddenly don't have to rewrite the laws of physics or gravity to make them work. The poison being much heavier than air will act like a liquid and naturally find the lowest point and many things could float atop of it even though it's a gas.


Yes if you can walk on the top of a blimp. It could be build like an upside down pyramid and coloured to look like land. I would use chambers and have the biggest at the top to keep it upright. Build large enough it could be self sustaining using rain and grow food.

enter image description here

enter image description hereenter image description here


Force field that envelops the islands as a bubble and supercharges on the poles antigravity particles that maintain the island in a permanent equilibrium between falling and floating.

Energy source a combination of antimatter or cold fusion should do the trick , add in a colony on mars for safe measure just in case the story needs part 2 and if you want some trading to happen.

Edited as @sphennings stated in the comments if we only consider a scientific plausibility to this question the answer is no. Maintaining big land masses floating needs an amount of energy that would be absurd to even calculate(for the amount of time you want "in place for significant millennia") and would be better used in colonizing another planet at that point.

Humanity has not yet found an energy source that would come close to the output you need and in the mass needed ( remember fuel has mass also...)

  • $\begingroup$ The question seems poorly asked. The title and the body disagree. They're asking for a solution that doesn't breach reality yet it's ok to break the laws of physics. Perhaps the correct answer is to explain why what they're asking is impossible given the constraints they've provided. $\endgroup$ – sphennings Nov 20 '17 at 15:50
  • $\begingroup$ I wanted to give him/her a possible way to make it possible, because the question "Can airborne floating/flying islands be scientifically possible?" would be a big round NO, any ways i'll edit my answer if that tingles your fancy more $\endgroup$ – Kaotis Nov 20 '17 at 15:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.