Wikipedia:Reference desk/Archives/Science/2025 July 24

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July 24

Lightning not in the atmosphere

Could a lightning occur entirely within the earth or ocean?Rich (talk) 01:05, 24 July 2025 (UTC)[reply]

Not according to the description in Lightning. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:13, 24 July 2025 (UTC)[reply]

Isn't Earth's atmosphere part of "the Earth"? That aside, to get lightning, first you need some process that generates a charge separation between different regions of something. And this process has to be able to get the field strength of the resulting electric field, to exceed the dielectric strength of the medium—upon which, dielectric breakdown happens and the medium begins conducting current. What sorts of processes are going to cause that in rock or in ocean water? Ocean water isn't a dielectric at all; it's electrically conductive. --Slowking Man (talk) 02:19, 24 July 2025 (UTC)[reply]

I don't know that much. Concerning the ocean or a even a lake, i was wondering if the water would acquire a charge relative the earth beneath it, maybe from an ordinary lightning stroke from the atmosphere. As a side note, maybe some form of lightning inside caves or empty magma chambers? But another thing I was wondering if inside the crust or mantle or even core, charge separation could build up, probably much more slowly than in the atmosphere, and somehow get triggered by a cosmic ray or gamma ray from uranium decays. And I don't see that the charge carriers would need to have water droplets in a generalalized lightning.Rich (talk) 03:55, 24 July 2025 (UTC)[reply]

Some related topics:

1. Fulgurites.

2. Electricity at hydrothermal vents.

3. Piezoelectricity/Flexoelectricity/Triboelectricity maybe in connection to earthquake lights if they're real. Also Seismo-electromagnetics: Current research suggests it's dissolved gases that come out of solution when de-pressurized and then ionize to generate the electrical signatures.

4. Telluric currents, which sound like more forteana but are used in Magnetotellurics for serious geology. Geomagnetically induced current (a better article).

I also vaguely remember an old ref desk question about getting electric current for free by ... well it involved sticking poles in the ground, or a cable. But none of this is very much like lightning (as Bugs already told us).  Card Zero  (talk) 07:05, 24 July 2025 (UTC)[reply]

Well for "electric current in the ground" there's this: single-wire earth return. (Also perhaps of interest: [1]) Of course, it's only "free" to you if you're sponging off someone else's SWER system. Depending on soil chemistry, you can do the electric potato thing with suitable rods, but that's only "free" until you deplete it. --Slowking Man (talk) 23:31, 26 July 2025 (UTC)[reply]

There's an anecdote – whether it's true, I don't know, but it sounds somewhat plausible – of a lightning strike underground in a gold mine in the US, 19th or early 20th century. Supposedly, lightning struck the ground and the electric current passed through a gold vein. The gold vein was interrupted by the mine and lightning jumped from the ceiling to the floor of the tunnel. PiusImpavidus (talk) 09:25, 24 July 2025 (UTC)[reply]

Reminds me of The First Sirian Bank -- Verbarson  ^talk_edits 20:09, 25 July 2025 (UTC)[reply]

The thing is that water in a lake or ocean is itself an electrical conductor. If lightning hits it (which happens a lot, over the 70% of the planet's surface that is water), the current just flows through the water "down" the voltage gradient. There is no visible "bolt" figure in the water: the "bolt" you see in the air is formed by some of the air getting ionized, once the air's breakdown voltage is exceeded, into a plasma. The electric current flows through this conductive "channel" of plasma and superheats it to glowing; thunder is caused by the explosive expansion of the plasma and surrounding air as it's suddenly heated.

Soil is variably conductive (for one it tends to have some water dissolved in it): not extremely well, but enough to use it as a generally-assumed-as-infinite "sink" to use as the zero-voltage reference point for electrical ground. Take a look at that SWER stuff I mentioned above, to see how demonstrable amounts of current can even be conducted long-distance through it! Getting deeper down, I'd have to defer to a geophysicist for details, but I suspect interaction with Earth's magnetic field makes it so a large-scale charge separation can't really form and be sustained. For one the convection currents in the mantle and core get "linked in" with the planet's magnetic field; that's how it's generated, and there's continual chaotic effects back-and-forth between the field and the mantle/core. --Slowking Man (talk) 23:31, 26 July 2025 (UTC)[reply]