3 ms·

> into motion Kinetic energy will end up getting converted to waste heat nonetheless. > or bound carbon This seems hard to imagine. We're dealing with waste

> into motion Kinetic energy will end up getting converted to waste heat nonetheless. > or bound carbon This seems hard to imagine. We're dealing with waste energy here, so a very high-entropy type of energy. Bound carbon is low-entropy, so the conversion is impossible[0] unless we put that entropy elsewhere. As an analogy, consider a fridge: It brings your food from a high-entropy (high-temperature) to a low-entropy (low-temperature) state but in order to do that it also has to produce waste heat (entropy) on the outside. [0]: https://en.wikipedia.org/wiki/Second_law_of_thermodynamics https://en.wikipedia.org/wiki/Second_law_of_thermodynamics

regularfry 5y ago
We're not necessarily talking about a closed system, though. If you've got an energy supply that rounds to limitless, constructing planet-scale heatsinks starts to look tenable.
- codethief 5y ago
  > We're not necessarily talking about a closed system, though. Short of shooting hot lava into space[0] we pretty much are because, once again, thermalization through radiation is governed by Stefan-Boltzmann's law and there's no way around that. [0]: https://news.ycombinator.com/item?id=28468182 https://news.ycombinator.com/item?id=28468182
  - regularfry 5y ago
    Stefan-Boltmann talks about emission per surface area. So... increase the surface area. We're not limited to a sphere. The same problem crops up when you're talking about moon bases and so on - you've got the same problem of venting heat from an ecosystem into a vacuum. For that situation, one of the solutions that got designed out was to basically spray an oil mist across a gap, catch it, and recycle it into the cooling system. As a fine mist, the oil has a colossal surface area compared to its mass, and all that surface area can radiate heat off into the vacuum. So... scale that up? I realise it's a hell of a leap, to go from human-scale to humanity-scale, and I don't know exactly what it would need to look like, but limitless energy is a hell of a springboard.

regularfry 5y ago

We're not necessarily talking about a closed system, though. If you've got an energy supply that rounds to limitless, constructing planet-scale heatsinks starts to look tenable.

codethief 5y ago
> We're not necessarily talking about a closed system, though. Short of shooting hot lava into space[0] we pretty much are because, once again, thermalization through radiation is governed by Stefan-Boltzmann's law and there's no way around that. [0]: https://news.ycombinator.com/item?id=28468182 https://news.ycombinator.com/item?id=28468182
- regularfry 5y ago
  Stefan-Boltmann talks about emission per surface area. So... increase the surface area. We're not limited to a sphere. The same problem crops up when you're talking about moon bases and so on - you've got the same problem of venting heat from an ecosystem into a vacuum. For that situation, one of the solutions that got designed out was to basically spray an oil mist across a gap, catch it, and recycle it into the cooling system. As a fine mist, the oil has a colossal surface area compared to its mass, and all that surface area can radiate heat off into the vacuum. So... scale that up? I realise it's a hell of a leap, to go from human-scale to humanity-scale, and I don't know exactly what it would need to look like, but limitless energy is a hell of a springboard.