So in a world plagued by Floating Iridescent Jellyfish that are Inflammable(FIJI). Assuming they float with the aid of highly flammable, lighter than air gas/mixture that ignites at altitudes of 3km or higher.

What problems would such a world face with FIJI occasionally dropping from the skies? (The flaming environment kind, not the cultural, economical, social kind) in a medieval-esque world.

I would assume that it would it burn some vegetation but there should be more serious consequences like the occasional burning house right?

EDIT: FIJI are about 50cm to 50 cm big. Tentacles can be up to a meter or two. They don't really move, they use the air currents to move around. Therefore they don't really have control over where they go. However, they do tend to be carried around in large groups of up to a hundred FIJI strong.

  • $\begingroup$ How large are they FIJI? $\endgroup$ Commented Oct 1, 2016 at 4:23
  • $\begingroup$ Could you provide detail about their behaviour that is their movement, localisation etc is it like normal jellyfish or like migratory birds?? $\endgroup$
    – user93
    Commented Oct 1, 2016 at 4:30
  • $\begingroup$ And how high do they fly or do they change altitude drastically $\endgroup$
    – user93
    Commented Oct 1, 2016 at 4:31
  • $\begingroup$ Some comment on how it's too broad pls. My brain isn't at it's best. $\endgroup$
    – Skye
    Commented Oct 1, 2016 at 7:47
  • $\begingroup$ So, thanks for the information; its size would have drastically effected the volatility of it's combustion. The groups of Fuji adds an interesting aspect to this explosion business (chain combustion!) $\endgroup$ Commented Oct 1, 2016 at 7:56

2 Answers 2


Out of curiosity, What flammable gas will be most likely used by the FIJI?

There are many gasses with a density lighter than air, but few are flammable. More common combustable gasses include Hydrogen (H2), Methane (CH4) and Ammonia (NH4). Since Methane is readily produced through the digestive process of many creatures (microbial respiration), it will be one of the easiest gasses for the FIJI to form and collect in it's canopy/whatever the organ it called that holds the gas. (I like the name "float-bladder").

Methane burns cleanly, which means that out of all fossil fuels releases the lease carbon dioxide when burnt, making it a "cleaner" alternative to coal or LPG. When ignited, FIJI's are going to burn at least 75% of their methane store immediately to form carbon-dioxide and water, meaning there is going to be little climate destruction caused because of them in this regard.

The Canopy or "bell" of a normal jellyfish is made from a non-living material called "Mesoglea"; primarily made from water, it gives the fish it's typical jelly-like appearance, also making it the definition of non-flammable (hence, being the bulk of the FIJI, this means that when the creature explodes the organic debris that drops to the earth will not be as ablaze as one might first expect). But the FIJI is not a "normal" jelly fish, so it would be naive to assume it would retain the same gelatinous water-bell; instead we must assume it has evolved an even lighter, more elastic, parachute like material to use instead, a material that can not only hold methane but one that can burn long after the initial spontaneous combustion has occurred, almost like the wick of a candle.

With such a canopy, the almost harmless explosion process takes a more dangerous turn.

After the initial explosive event, the FIJI's burning remains will rain down spectacularly from the sky. As this combustion process takes place at an altitude of +3km, the embers will have a long way to fall, and at the mercy of the wind will be carried in all directions - hence possessing a very large potential burn radius. They will land in random locations where if in close proximity to fuels in the form of grasses, timber or flammable liquids ( and provided that it is still alight) will quickly start spot fires that have to potential to then grow into large untamed blazes, posing great risk to life in nearby areas. With little control over when explosions will take place and where exactly fragments of the FIJI will fall, there cannot be much done to prevent these fires flaring up - besides eliminating all dry foliage or the FIJI population in general.

NOTE: The probability of spot-fires burning out of control will more or less depend on the weather conditions as much as the burn-time of the FIJI itself, which will be dictated by the material it is composed of. Depending on these factors, the FIJI can either be a relatively harmless creature, or a devastating force of the natural world!

ADDITIONALLY: Given that these creatures travel in large groups, the combustion of one may cause those nearby to ignite also, leading to the chain explosion of dozens of FIJI and potentially catastrophic damage to the surrounding ecosystem (huge amounts of firry debris from said event more than capable of causing severe bush-fires or the destruction of countless homes in an inhabited region). The population of your world will need to have preventative measures in place, like water-bores and other water catchment/distribution systems, in case one of these fire-storms takes place nearby, or they'll be in a lot of strife. FIJI therefore could also prove an interesting dynamic in war, an enemy "blowing" a group of creatures into opposition territory and exploding them one way or another.

  • $\begingroup$ I added in the size. But just add in your take on flaming FIJI. I'm gonna have to look for more volatile substances to put in. $\endgroup$
    – Skye
    Commented Oct 1, 2016 at 7:21
  • $\begingroup$ @Skye it has been revised as per your editing. Still, a second question relating to the actual biology of the FIJI would be great, once this one gets enough positive attention. Enjoy. $\endgroup$ Commented Oct 2, 2016 at 9:38
  • $\begingroup$ Thanks, unfortunately I could have sworn that there was a question on flying jellyfish. $\endgroup$
    – Skye
    Commented Oct 2, 2016 at 12:00
  • $\begingroup$ @Skye, another question about iridescent jellyfish that are flammable? $\endgroup$ Commented Oct 5, 2016 at 1:14

I would assume that it would it burn some vegetation but would there be more serious consequences?

Since the Neolithic Revolution, having all your crops burned down is basically the most serious thing that could happen. People in your world need to focus on plants that fire spreads poorly in - so rice where it's possible, as it can be grow partly submerged, and if they are into potatoes or cabbage they need to carefully weed them. Wheat and other dry cereal is completely out of question.


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