Does Laplace's demon know about entropy?

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SUMMARY

The discussion centers on the philosophical implications of entropy in a deterministic universe, particularly in relation to Laplace's demon, a thought experiment in classical mechanics. It posits that if Laplace's demon knows the precise microstate of the universe, the concept of macrostate and, consequently, entropy may not apply in the same way it does for humans. The conversation also introduces the idea of a "half-demon," which only knows particle positions, suggesting that entropy could be perceived subjectively based on the information available. This raises questions about the objectivity of thermodynamic entropy versus information entropy in information theory.

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  • Understanding of Laplace's demon and deterministic systems
  • Familiarity with concepts of microstates and macrostates in thermodynamics
  • Knowledge of entropy in both thermodynamics and information theory
  • Basic principles of classical mechanics and statistical mechanics
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Philosophers of science, physicists, and anyone interested in the foundational concepts of entropy and determinism in both thermodynamics and information theory.

greypilgrim
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Hi.

I read this thread with great interest and have similar question:
In a deterministic universe, does entropy exist for Laplace's demon? Since he knows the universe to it's microstate, does the term "macrostate" even make sense to him?

And say there is a "half-demon" that only knows the position of each particle in the universe. Since this greatly reduces the number of possible microstates, he should ascribe the universe a lower entropy than we humans do. Does this mean the notion of entropy is purely subjective? If I measure the temperature of a gas in my lab and compute the entropy, I might get a smaller number than my colleague outside who doesn't now the exact temperature and therefore needs to take into account microstates of other temperatures as well. Is he wrong, or are we both right?

I know that in information theory, entropy is highly subjective and can change drastically upon learning new information. I have experienced entropy in thermodynamics to be used much more objectively, but why?
 
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As you mention infomation entropy, where does the demon store all the information he has about the universe? What would be the information entropy of that storage device?
 

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