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Can we build deep into the Earth? Probably not... but it's funny to think about. The mantle is less than 4000 degrees C. Yet there are known materials with a m

Can we build deep into the Earth? Probably not... but it's funny to think about. The mantle is less than 4000 degrees C. Yet there are known materials with a melting point above that: https://www.asminternational.org/web/cmdnetwork/home/-/journal_content/56/10180/25655039/NEWS https://www.asminternational.org/web/cmdnetwork/home/-/journ... Even regular Tungsten would apparently get you through most of the mantle without melting. Alright, so what can be done about the extreme pressure that deep? It seems like bulk nanotubes are perhaps the only theoretical material that could withstand the pressure (100GPa)?

elihu 6y ago
> Alright, so what can be done about the extreme pressure that deep? Don't have any compressible gases. If we're just sending machines and infrastructure into the mantle, maybe that's possible. If we want to send people it's harder. I don't know if anything like the oxygenated fluid from the Abyss (or the LCL from Evangelion which was more or less the same thing) does or can exist in reality. Or if other problems would arise at extreme pressures. Your mention of high melting point materials makes me wonder if fiber optic cables could be made that survive in that environment. It'd be an expensive undertaking just to reduce, say, the network latency from North America to Asia. If we ignore the mantle, building into the shallow crust where it's still cool seems like a reasonable thing to do. I suspect the main reason it's usually not done are the cost of earth removal and reinforcement being higher than above-ground structures, and having to deal with water. It's fun to think about what an underground megastructure would be like, though. Could be as simple as turning an old pit mine or quarry into a below-ground urban center. In Portland, OR out towards Gresham there's a huge hole in the ground next to the Multnomah County land use planning department that I suppose is probably an old quarry. I like to imagine what it'd look like with apartment complexes along the sides and a park with a lake at the bottom. Maybe a shopping center with a farmer's market, and a light rail stop. Keeping it from flooding would be a huge logistical challenge, though.
- eloff 6y ago
  There is something like that in China, a luxury hotel in a quarry: https://www.ihg.com/intercontinental/hotels/us/en/shanghai/shghe/hoteldetail https://www.ihg.com/intercontinental/hotels/us/en/shanghai/s...
  - elihu 6y ago
    Wow, that's pretty cool.
- adrianN 6y ago
  The oxygenated fluid from the Abyss is a real thing https://en.wikipedia.org/wiki/Liquid_breathing https://en.wikipedia.org/wiki/Liquid_breathing
  - nradov 6y ago
    Only sort of real. So far no one has made it practical for humans.
- pontifier 6y ago
  We just need a few nuclear powered tunnel borers going. Then earth removal,water, and reinforcement aren't that big of issues. I've often wondered if there aren't already some of them crisscrossing the US already.

elihu 6y ago

> Alright, so what can be done about the extreme pressure that deep? Don't have any compressible gases. If we're just sending machines and infrastructure into the mantle, maybe that's possible. If we want to send people it's harder. I don't know if anything like the oxygenated fluid from the Abyss (or the LCL from Evangelion which was more or less the same thing) does or can exist in reality. Or if other problems would arise at extreme pressures. Your mention of high melting point materials makes me wonder if fiber optic cables could be made that survive in that environment. It'd be an expensive undertaking just to reduce, say, the network latency from North America to Asia. If we ignore the mantle, building into the shallow crust where it's still cool seems like a reasonable thing to do. I suspect the main reason it's usually not done are the cost of earth removal and reinforcement being higher than above-ground structures, and having to deal with water. It's fun to think about what an underground megastructure would be like, though. Could be as simple as turning an old pit mine or quarry into a below-ground urban center. In Portland, OR out towards Gresham there's a huge hole in the ground next to the Multnomah County land use planning department that I suppose is probably an old quarry. I like to imagine what it'd look like with apartment complexes along the sides and a park with a lake at the bottom. Maybe a shopping center with a farmer's market, and a light rail stop. Keeping it from flooding would be a huge logistical challenge, though.

eloff 6y ago
There is something like that in China, a luxury hotel in a quarry: https://www.ihg.com/intercontinental/hotels/us/en/shanghai/shghe/hoteldetail https://www.ihg.com/intercontinental/hotels/us/en/shanghai/s...
- elihu 6y ago
  Wow, that's pretty cool.
adrianN 6y ago
The oxygenated fluid from the Abyss is a real thing https://en.wikipedia.org/wiki/Liquid_breathing https://en.wikipedia.org/wiki/Liquid_breathing
- nradov 6y ago
  Only sort of real. So far no one has made it practical for humans.
pontifier 6y ago
We just need a few nuclear powered tunnel borers going. Then earth removal,water, and reinforcement aren't that big of issues. I've often wondered if there aren't already some of them crisscrossing the US already.