My world's flying islands are made of a kind of coral that grows up to tens of kilometers in size, usually smooth on the bottoms and with plant life on top, mostly from seeds left there by birds. The polyps excrete a gas lighter than air that keeps the colony afloat.

Islands drift with the wind and bob up and down as the coral gets dehydrated from being above the clouds and some of it dies, reducing lifting gas production and making the island sink until it becomes healthier again.

Today i wondered, what would happen if lightning struck one of these? What little i've read about lightning hitting airplanes and animals leads me to believe it wouldn't be great for the coral, but i'd love to hear what people who might know more about these things think.

Would the strike be less impactful with no ground current? Would the coral have to develop a way to avoid stormy areas? Would these things just being less conductive than air be enough to protect them, or would they need to develop something like a Faraday cage to be safe in a storm?

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[–] Wrufieotnak@feddit.org 4 points 3 weeks ago (2 children)

First thing that comes to mind: evolution lead to symbiotic union with another coral species that lives of stored electricity from lighting strikes, thereby protecting the other coral type.

Regarding the effect of a lighting strike: the biggest problem would probably be the change in electrical charge on the island as a whole. But not for the island travelers while on the island, but each time they interact with somebody/something from outside the island. Because the difference in static electrical charge would lead to an equilibrium between the two entities, i.e. a lighting strike. So every time a ship would land at the island, it would get zapped. Same if somebody from the island would get close to the ground.

[–] IndigoGollum@lemmy.world 2 points 3 weeks ago* (last edited 3 weeks ago) (1 children)

That's a point i hadn't considered. I was planning to have at least one populated island and airships that travel to it, but now i know i'll need to account for that in airship design. I wonder if an anchor or ground wire dragging on the ground would fix this.

Does this sort of thing cause problems on Earth with airplanes and zeppelins?

[–] Wrufieotnak@feddit.org 2 points 3 weeks ago

Does this sort of thing cause problems on Earth with airplanes and zeppelins?

That is completely outside of my expertise, but I would guess not. Most air vehicles are made out of metal on the outside, leading to the vehicle just being a conductor for the electricity passing further on to the ground and not "staying" in the vehicle.

Your islands would probably be enough of a ground mass, that it could store the electrical charge.

[–] veniasilente@lemm.ee 1 points 3 weeks ago (1 children)

If so, since we're talking about islands to be inhabited / urbanized here, I'm seeing two cases:

In the case of the island approaching the ground, would a practical way to deal with this be planting a lightning inverse-rod at the bottom of the island? So that electricity can more easily discharged to the ground while the island is approaching the ground, before any actual contact event?

In the case of people or objects from the island approaching the ground or vice-versa, I'm actually wondering how to even palliate this. Space (even airspace) is 3D and I don't think it's really feasible to place an "electro decompression cabin" all around the island.

[–] IndigoGollum@lemmy.world 2 points 3 weeks ago (1 children)

The island shouldn't ever land, and i have some plans for that already. I was actually thinking there would be towers and bridges leading up to the island (which is anchored in place), but airships would also have to be able to reach it. I think the inverse lightning rod would help with that. I was just planning to have regular lightning rods around the island, connected to the ground with chains. The people on the island would also go out of their way to keep it healthy, so it running out of water isn't likely.

You're right that a system for safe electrical equalization/decompression around the whole island wouldn't be feasible, but maybe those could exist on docks, and trying to land just anywhere is more likely to pop your airship.

[–] veniasilente@lemm.ee 1 points 3 weeks ago

If the islands are to be anchored in place most or all of the time, I think it would not be too unsafe to simply run wiring alongside whichever non-rigid or rope-like anchorings are available. That is, material and distances permitting.

The wiring wouldn't even have to necessarily reach down to the ground / up to the islands. Just high enough to an intermediary point where electricity can be discharged relatively safely away from the anchoring or connecting stations. And defo outside the range of airport-like platforms, but I'd assume in a civ where those islands are a long-term fixture there would be already regulations in place to restrict operation of flying machines directly underneath these islands.