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I agree that it feels different. It certainly does to me. Energy feels real, while entropy feels like an abstraction. A rock falling on one's head is a clear manifestation of its potential (turned kinetic) energy, while getting burned by a hot beverage does not feel like a manifestation of the entropy increase. it feels like the beverage's temperature is to blame. On the other hand, if we knew precisely the state of every water molecule in the cup, would we still get burned? The answer is not at all obvious to me. Passive_fist claims that the cup would appear to be a absolute zero then:
I do not know enough stat mech to assess this claim, but it seems wrong to me, unless the claim is that we cannot know the state of the system unless it's already at absolute zero to begin with. I suppose a toy model with only a few particles present might shed some light on the issue. Or a link to where the issue is discussed.
Expanding on the billiard ball example: lets say one part of the wall of the pool table adds some noise to the trajectory of the balls that bounce off of that spot, but doesn't sap energy from them on average. After a while we won't know the exact positions of the balls at an arbitrary time given only their initial positions and momenta. That is, entropy has entered our system through that part of the wall. I know this language makes it sound like entropy is in the system, flowing about, but if we knew the exact shape of the wall at that spot then it would... (read more)