Does Laplace's demon know about entropy?

In summary, the conversation discusses the concept of entropy in a deterministic universe and whether it exists for Laplace's demon. It also brings up the idea of a "half-demon" and how their knowledge of the universe's microstates affects their perception of entropy. The conversation then delves into the subjectivity of entropy and how it can differ based on the amount of information known. The question of where the demon stores all the information and the information entropy of that storage device is also raised.
  • #1
greypilgrim
548
38
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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  • #2
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?
 

FAQ: Does Laplace's demon know about entropy?

What is Laplace's demon?

Laplace's demon is a thought experiment proposed by French mathematician Pierre-Simon Laplace in the 19th century. It is a hypothetical all-knowing being who has complete knowledge of the universe, including the position and velocity of every particle at a given moment.

What is entropy?

Entropy is a measure of the disorder or randomness in a system. It is a thermodynamic quantity that describes the amount of energy that is unavailable for work in a system. In simpler terms, it can be thought of as a measure of the level of chaos or unpredictability in a system.

Does Laplace's demon know about entropy?

According to the thought experiment, Laplace's demon has complete knowledge of the universe. This would include knowledge about the position and velocity of every particle, as well as the laws of physics governing their behavior. Therefore, it can be assumed that Laplace's demon also has knowledge about entropy.

Can Laplace's demon accurately predict the future based on its knowledge of entropy?

It is debated whether Laplace's demon, even with complete knowledge about the universe, could accurately predict the future. This is because of the inherent unpredictability of systems with high levels of entropy. While Laplace's demon may have knowledge of the current state of the universe, it is unable to account for future changes in entropy that may alter the predicted outcome.

How does the concept of Laplace's demon relate to determinism and free will?

Laplace's demon is often used to illustrate the concept of determinism, the idea that all events, including human actions, are determined by previous causes. This raises questions about the existence of free will. If the universe is entirely governed by the laws of physics, then some argue that free will may be an illusion. However, others argue that even with complete knowledge about the universe, it is impossible to accurately predict human actions due to the complexity of the human mind and the unpredictable nature of entropy.

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