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noordung
@n00rdung
Long answer: it's because laws of physic with time reversal symmetry describe evolution of microstates, but since identity doesn't matter, thermodynamic arrow of time is a direct consequence of equivalent macrostates corresponding to unequal number of microstates.
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Enye Word
@EnyeWord
Replying to
@QiaochuYuan
Not a physicist, but my general impression is that high-entropy macrostates have more corresponding microstates, so a system that starts in a low-entropy macrostate tends to move (essentially at random thru microstates) to high-entropy macrostate, but the reverse is unlikely.
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Dhruva
@dhruvakarkada
Yup this is correct and the real (unsolved) mystery is why the universe started w/ low entropy "macrostates = human construct" (another reply) is kinda the right idea (entropy is fundamentally info-theoretic). We kinda decide what to measure (physics/locality constrains us)
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Mike
@noworkfunction
Replying to
@QiaochuYuan
all that mass that produced the big bang had to come from somewhere eventually the system could get back to that state and not violate any laws of physics we see entropy increasing on our relevant time scales, but nothing says we can't get a big decrease... eventually...
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IdeaRadar
@idearadar
Replying to
@QiaochuYuan
I think Carroll’s perspective that it’s all about the big bang is directionally correct (alas not a physicist, just a curious human)
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Patrick Wilkie
@patlouiswilkie
Replying to
@QiaochuYuan
Not Loschmidt’s paradox directly but Marletto 2016 formalized Thermodynamics through Constructor Theory (down to quantum scale). She provides a “non-approximative, scale independent formulation of adiabatic accessibility”.
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