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Einstein's Cat
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I am aware of the Second Law of Theromodynamics and I understand it to a certain extent, although still I am burdened with the frustration of being ignorant to why such a law exists. Please assist me.
Why does this irreversibility exist?QuantumQuest said:It is an empirical finding and it is accepted as an axiom of thermodynamics. Its microscopic origin is explained by statistical thermodynamics. It basically has to do with the irreversibility of a thermodynamical process, something observed in our macroscopic reality.
Einstein's Cat said:Why does this irreversibility exist?
So in this perspective, entropy is a property of an observer? For example, at any moment I could look inside and know the exact state, and hence claim the entropy is zero, but for you the entropy would still be nonzero. So the entropy is "of me" or "of you" and not "of the dice." But in thermodynamics entropy is presented as a state variable, isn't it? The entropy is "of the state of the system" and not "of me" or "of you."Khashishi said:If you know the initial state exactly, then the initial entropy is 0. As time passes, you know less and less about the state of the dice, and entropy increases.
Nathanael said:So in this perspective, entropy is a property of an observer?
So would you disagree with Khashishi in saying "If you know the initial state exactly, then the initial entropy is 0." ?DrStupid said:No, it is a property of the system. In statistical thermodynamics the entropy of a macro-state depends on the logarithm of the number of the possible micro-states. In Khashishi's example the initial macro-state is "1" facing up for all dices. As this macro-state has only a single micro-state it's entropy is zero.
Nathanael said:whereas Khashishi said the entropy is zero because we know exactly what all the dice are.
This quote gives me the impression that it was a more general statement, but perhaps it was meant only for the specific example of all 1s.Khashishi said:Entropy can be thought of as your lack of knowledge about a system. If you know the initial state exactly, then the initial entropy is 0.
Nathanael said:I appreciate your clarification of entropy as the logarithm of the number of micro states which produce a certain macro state.
Irreversibility is the result of (a) viscous dissipation of mechanical energy to internal energy, associated with rapid deformation of a material (b) dissipation of temperature gradients, associated with rapid (spontaneous) conduction of heat in a material, (c) dissipation of concentration gradients, associated with (spontaneous) diffusional transport and mixing of chemical species in a material, and (d) dissipation of chemical potential driving force resulting from (spontaneous) chemical reactions in a system.Einstein's Cat said:Why does this irreversibility exist?
How would one determine such a probability?DrClaude said:Heat could flow from a cold body to a hot one, but the probability of that happening is so small that in practice, it will never be observed.
By considering the multiplicity of each macrostate (i.e., the number of microstates associate with each macrostate).Einstein's Cat said:How would one determine such a probability?
The 2nd law of thermodynamics is a fundamental principle in physics that states that the total entropy (disorder) of a closed system will always increase over time. This means that energy will naturally flow from a state of higher concentration to lower concentration, resulting in a decrease in usable energy.
The 2nd law of thermodynamics has many practical applications, such as in the design of engines and refrigeration systems. It also helps us understand why certain natural processes, such as diffusion and heat transfer, occur in a particular direction.
The 1st law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted. The 2nd law, on the other hand, deals with the direction of energy transfer and how it affects the overall entropy of a system.
Entropy is a measure of the disorder or randomness in a system. The 2nd law of thermodynamics states that the total entropy of a closed system will always increase, meaning that the system will become more disordered over time. This is because energy tends to spread out and become more evenly distributed, leading to an increase in entropy.
No, the 2nd law of thermodynamics is a fundamental law of nature and cannot be violated. It has been extensively tested and confirmed through numerous experiments and observations. However, there are certain processes that may appear to violate the law, but they are actually following it when considering the entire system and its surroundings.