Thermodynamics as probability rather than unbreakable law?

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Discussion Overview

The discussion revolves around the nature of the second law of thermodynamics, particularly its probabilistic interpretation in the context of statistical mechanics. Participants explore the implications of viewing thermodynamic laws as statistical rather than absolute, with references to entropy and fluctuations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the high esteem given to the second law of thermodynamics and seeks clarification on the probability of it being violated, referencing a statement from their lecturer about a very low probability of such an event occurring.
  • Another participant explains that the most likely state of a system is the one that can be achieved in the greatest number of ways, using examples of gas mixing and card shuffling to illustrate this concept.
  • A further contribution suggests that the probability of gases remaining separated is much lower than that of a shuffled deck of cards ending up in perfect order, indicating a difference in the number of possible states.
  • One participant notes that the second law is statistical in nature and mentions the Fluctuation theorem, which describes the probability of observing entropy fluctuations contrary to the predictions of the second law.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and interpretation of the second law of thermodynamics, with some agreeing on its statistical nature while others focus on the implications of probability. No consensus is reached regarding the exact probability of violations or the implications of these interpretations.

Contextual Notes

Limitations include the lack of specific definitions for terms like "probability" in this context and the unresolved mathematical steps needed to calculate exact probabilities related to entropy and thermodynamic laws.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of physics, particularly those studying thermodynamics and statistical mechanics, as well as individuals curious about the philosophical implications of scientific laws.

mitcho
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Excuse me if this is a really ignorant question but I tried searching google but all I got was debunking thermodynamics/creation arguments. My physics lecturer the other day was saying that in third year statistical mechanics we will be shown how to derive a formula giving the probability for the second law of thermodynamics. He said the probability of it being broken was somewhere in range of it happening once in the age of the universe to the power of 100 or something. Does anyone know this exact probability? Also, why is the second law of thermodynamics given such a high esteem as a law. I saw a quote that I can't remember word for word but something like "If you theory opposes Maxwell's equations then all the worse for Maxwell but if it opposes the second law of thermodynamics then all you can do is bow in shame". Any insight would be appreciated.
Thanks.
 
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I'm not an expert on entropy, e.t.c. But I do know that:
The most likely state is the one which can be made by the greatest number of different ways.
For example, if you start off with two separated gases, then remove the partition between them, the most likely outcome is that they will mix. But there is an extremely small probability that they will stay separated.
As another example, if you shuffle a pack of cards, they are most likely to end up in an order with no particular pattern. But there is a very small probability that they will end up in perfect suit and number order.
 
Clearly, the pack of cards in perfect order is far more likely to happen than the gases staying separate because there are a very large number of gas molecules.
You could work out the exact probability by counting the number of different states which can lead to each possibility.
 
The second law is indeed only statistical in nature. In particular, the Fluctuation theorem quantifies the probability that one will observe a fluctuation in entropy in the opposite direction that the second law predicts.
 

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