r6 and I discuss his theory that entropy is subjective

[gustavolacerda]

r6 and I discuss his theory that entropy is subjective

I've never been satisfied with the solutions I've seen to Maxwell's Demon.
I take r6's interpretation of entropy as an agent-dependent quantity related to his knowledge, and a measurement of what one can do with this knowledge: knowledge is power. According to his theory, an all-knowing being (

Comments

[darius]

I think your question is subtly different from Maxwell's Demon, who is supposed to extract useful work from the system, e.g. by pushing a piston against an external resistance. We can imagine two different idealizations of that interaction with the outside: either the demon has perfect knowledge/control of it -- it's microscopically reversible to the demon -- or it's a random interaction with a heat bath at some temperature. In the first case, to keep doing additional useful work we need an endless supply of zero-entropy resistance -- the demon must have an endless supply of prior information. In the second case, at the end of an expansion the demon no longer knows the exact state of the insides -- which I wrote about before.

This is still a bit handwavey, but I think that's the shape of the argument you're looking for -- that at some point you need to interact with an uncontrolled environment for this to matter. Physical law is such that information is conserved in time evolution (well, modulo quantum measurement); if the amount of information in the 'outside' is reduced, the amount in the 'inside' must be increased.