Your basic, average floating sky island. How would a floating island 1. Get up high, and 2. Stay up.

Here's the info you need to work with:

  1. The planet is Earth-like (supports earth like life)
  2. The islands aren't man-made
  3. Gravity is a below Earth's (Gravity can be as low as .9 or .1 of Earth's)
  4. Floating Islands can support life as well

Here's the bonus questions :

  1. How would life evolve on these islands (would it be mainly winged or never see outside of the island.)
  2. How would humans look at these islands (would they be home to kingdoms or what)
  • $\begingroup$ Floating in air or floating on water? $\endgroup$
    – SRM
    Commented Dec 2, 2016 at 21:44
  • 2
    $\begingroup$ I think that you should make clear that you are interested in islands floating in the air. Islands floating on water are quite common. $\endgroup$
    – AlexP
    Commented Dec 2, 2016 at 21:44
  • 1
    $\begingroup$ We already have one, albeit a little high up than what I assume you want. There are treaties that prevent kingdoms from being established on it though. $\endgroup$
    – user69874
    Commented Dec 2, 2016 at 22:13
  • $\begingroup$ If you pick one of the flotation methods in the potential duplicate, you could narrow this question and focus only on the life question. $\endgroup$
    – Brythan
    Commented Dec 4, 2016 at 3:07

4 Answers 4


Link to full avatar answer

Basically, you could do what they did in the Avatar movie. Their floating mountain has unobtanium in them, which is a room temperature superconductor. They float because of the Meissner effect with the magnetic field below them.

A superconductor is a material that when you cool it down to a certain temperature, it can conduct electricity effortlessly without much energy loss. This allows them to float in the presence of a magnetic field. You can look up the details, but basically, a magnetic field's flux cannot penetrate a superconductor once it becomes superconducting, so it bends and pushes around them instead, allowing the material to float in midair. So, if I add electricity into those superconductors, they'd be able to run in those materials forever. Unless the earth somehow loses its magnetic field, those islands could stay floating forever.

Now unobtanium is a room temperature superconductor, which takes away the requirement for them to be cool to their critical temperature. And since the gravity is lower than that of earth, the magnetic field can similarly be lower than that of earth, which would allow the use of metal tools and such without the tools propelling upwards.

I'm not sure about the evolution part, so I'll just take a guess. If you want humans on those islands, I imagine life would evolve normally similarly to that of earth, up until about sailing and such.

It probably depends largely on the environment of your islands. How big are your islands? Are they massive continents with diverse biomes, or just small floating island with one single environment? After all, the reason human evolved in the first place is due to the Africa savanna. Without a floating Africa savanna, humanity might not evolve at all and you'd have monkeys eating fruits in their floating island forests happily forever.

If humanity did evolve and formed societies, then depending on how close the islands are to one another, they could build bridges between the islands. If the islands are far apart, perhaps they will never know another island until the invention of the telescope. And they'd still have no means of travel across until the invention of the hot air balloons.

As for if they'd belong to a kingdom or not, it also depends on how big of a population each island can support. Humans naturally form societies and work together. If your islands are small, perhaps they'd form tribes and villages and band together. If you islands are big enough, then they could certainly form kingdoms, given enough time.

  • 1
    $\begingroup$ If you want humans t olive on them they need to be big, humans need a lot of water, and the only water on your floating islands are going to be what collects from rain. No wells in the sky. Birds however will love them, no ground predators. $\endgroup$
    – John
    Commented Dec 2, 2016 at 23:23

Difference in Gravitational Field

Perhaps gravity effects the island's foundational material differently than the rest of the environment, allowing the island to float. Some possible explanations for why gravity effects the island differently could be:

  • Intentional Alteration: Perhaps gravity is being manipulated purposefully by humans or an alien race.

  • Accidental Alteration: Perhaps accidents in gravitational manipulation have left gravity permanently or temporarily effecting the foundation material of the island less than normal.

  • Natural Difference: Perhaps in your story a certain type of material is naturally effected by gravity less than other materials. This material would then be the foundation of the islands.

  • Natural Fluctuations: Perhaps in your universe, gravity's effect on certain materials naturally fluctuates from time to time.

Evolution of Life on Floating Islands

I think the main issues affecting evolution on a floating island could be termed as environmental factors. I feel it is the envionment that dictates how life can evolve. Some major environmental factors would be:

  • Size of the island: The larger the island, the more likely life will not need to evolve to leave the island. The smaller the island, the more likely life will have needs going unmet on the island, and would therefore have to evolve to get the needs met from the surrounding environment. If the island was only a few feet wide, the possibilities for life evolving there would be much less than if the island was thousands of miles wide.

  • Movement: If the islands are very small and moving very quickly, life evolving there would need to tolerate this movement, whereas if the islands are large and don't move at all, movements would not be as big of an issue. Also, size, direction and frequency of movements would affect evolution. Tiny movements would probably affect evolution less than enormous movements. Direction of movements, such as linear, spinning, flipping, wobbling, etc. would affect evolution. Frequency of these movements would also play an integral part in evolution. If sudden huge movements happened every day, life would have to be able to withstand such shifts, whereas if there were only a few movements per decade, life could be less affected by them.

  • Existence of other land masses: The presence of other lands gives evolutionary reason to possibly go to them. Lack of other places to go, though, gives little evolutionary incentive to evolve to leave.

  • Limitations on travel to or from the island: If there were hinderances to leaving the island, such as severe weather surrounding the island, then that would affect the evolution of any life trying to leave. Lifeforms leaving the island could perhaps jump, fly, float (like a blimp), glide, fall (perhaps not being able to return), teleport, or perhaps even use tools to build machines enabling them to leave the island. If waterfalls or vines were there, they could be used as travel vectors, or even fallen trees or long rock outcroppings could be used as bridges to nearby lands. Strong winds, sideways or updrafts, could also be useful for travel.

How Human View the Islands

I think that depends on many, many factors, such as:

  • Size: If the islands are only a few feet wide, they could be much less interesting than if they were significant landmasses. However, clouds of small chunks of land, like hail storms or like fields of small asteroids, could evolve much different lifeforms than large lands.

  • Number: Rarity of floating islands could make them prized or revered; abundance could render then uninteresting; overabundance could cause them to be annoyances.

  • Resources: If the islands were home to valuable resources, humans would definitely like to get there and gain control of the resources; if the islands were innocuously plain, with nothing to offer, people might have little interest.

  • Protection: If humans were threatened by other elements, such as floods, fires, wars, predators, etc, they might want to take refuge on the islands, if the islands could provide safety.

  • Ease of Travel: If it is easy to travel to and from the islands, they would be treated differently from islands extremely difficult to reach. Extreme difficulty could be useful in providing protection from invaders, and extreme ease of travel could give rise to effortless trade and expansion.

  • $\begingroup$ «how an island could float would be for the amount of gravitons affecting the island to vary from its surroundings. » that's wrong on multiple levels. $\endgroup$
    – JDługosz
    Commented Dec 4, 2016 at 7:35
  • $\begingroup$ You might want to review my edit for future reference. $\endgroup$
    – JDługosz
    Commented Dec 4, 2016 at 7:37
  • $\begingroup$ @JDługosz Thanks...I got too tired of proofreading. I'll reword it. $\endgroup$ Commented Dec 4, 2016 at 16:00
  • $\begingroup$ @JDługosz Ok, see how that works. My brain is pretty tired right now. $\endgroup$ Commented Dec 4, 2016 at 16:22

Apart magic, the only solution is see is levitating with magnetic field, like in the movie Avatar:

  • The magnetic field on the planet is way stronger than earth
  • On some island, there are a lot of ore of some metal that act as a strong magnet: the magnetic field is strong enough to support the island
  • Violent geological event like earthquake or landslide can weaken link between island and ground, allowing the island to float in the air.

Bonus question:

  1. Life on theses island would initially the same ecosystem in regular island when the separation occur due to the fact floating island receive the same amount of sunlight and rain than regular isles, there are just no geological activities so no hot spring. However, with no direct access to sea, animal that relies on fishing to survives will disappear or change. Moreover, the lack of accessibility will prevent new animal or plant to establish in this island, excepting bird and seeds carried by them.

  2. Due to the fact that island are inaccessible and certainly moving, no country could claim theses floating island until the discovery of flying locomotion like hot air balloon. This restriction could lead to better interest in flying transportation in order to access theses mysterious island. Once flying discovers, floating island would act as regular island and be used as airport and military base. At last, the abundance of strong magnet ore on each island could be useful for any science field that use magnet.

  • $\begingroup$ Wouldn't the magnetic ore eventually lose its strength? $\endgroup$
    – Areeb
    Commented Dec 2, 2016 at 22:35
  • 1
    $\begingroup$ yes. And if it was powerful enough to lift the island it would likely flip it over then bring it crashing down with tremendous force during the first storm. Be fun to watch though. $\endgroup$
    – John
    Commented Dec 2, 2016 at 23:43

The simplest and most probable mechanism would be the islands have lower average density than air (basically think of huge natural balloons).

This would be more probable in environments where there is lots of air (increasing the average density of the air). It would require some natural mechanism that forms gas traps and a mechanism that produces lighter than air gas in large quantities. Membranes trapping large amounts of light gasses could form, albeit this would require some exotic chemistry. On microscopic scales this does happen in earths oceans - a variety of plankton organisms enclose oils/fats that makes them lighter than water.

But anyhow in an environment that facilitates earth like life, huge islands would not be stable over geological time frames. Erosion by rain would disolve them in comparably short time frames; any matter lost to erosion does end up leaving the island eventually. Collisions between islands would also act to accelerate their eventual destruction. This would happen regardless of what their mechanism for keeping afloat is.

Without a basis for stability over geological time frames, life spread on these islands would not have time to specialize too much for their environment. Also, most likely islands would be very dry, arid environments. Rain would either run off, or if the geometry traps it in a pocket make the island so heavy it sinks to the ground in a few years. They might be still host universalist species, or seasonally (e.g. as breeding ground for avain species).

Working up a scenario where floating islands can believably exist (for the sceptic reader) will be exceptionally hard, if not impossible.


Not the answer you're looking for? Browse other questions tagged .