4 ms·
Is it merely impractical though? In the thought experiement the demon needs to be able to know the state of the impending particle before it arrives, so it can
by jp57 4y ago
Is it merely impractical though? In the thought experiement the demon needs to be able to know the state of the impending particle before it arrives, so it can decide whether to open the door. It can't do that without interacting with them and changing their state.
- nobodyandproud 4y agoHere’s a more mechanical variation of Maxwells Demon: https://en.m.wikipedia.org/wiki/Brownian_ratchet https://en.m.wikipedia.org/wiki/Brownian_ratchet
- bee_rider 4y agoI think it depends on how you define the demon. I first heard of it in the final, resolved version, so I see it as just impractical (because the solution is baked in). The interaction between the demon and the particles is the key. The final version, at least as far as I'm concerned, comes from Landauer and Bennett [https://en.wikipedia.org/wiki/Maxwell%27s_demon#Criticism_and_development https://en.wikipedia.org/wiki/Maxwell%27s_demon#Criticism_an...] -- the demon must accumulate information (which it can only do finitely) or erase it. Erasing information has a real physical cost, resolving the issue. When the demon was first invented, information theory hadn't been developed yet. So the mystery to Maxwell was that it looked like it was violating energy conservation, but that's just because there's a sneaky place we can store entropy temporarily or finitely. So, I think I was imprecise (or... wrong). A demon that does what we really want (generates free energy) is impossible. But it is impossible for weird reasons that Maxwell wouldn't have been aware of, and I don't think he explicitly explored them.