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- Thread starter ugalpha
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Thank you!

- #2

Drakkith

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- #3

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The first principle it's never violated. It is described in the first postulate of thermodynamics, which is the conservation of energy postulate. The entropy is treated on the second postulate.

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The way I understand it, those laws are mutually excusive by experiments. That is, no experimental correlation where found between them. Hence we postulate, which is intuitive, that they are not related (see, for example, the kelvin statement of the second law).

- #5

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Most obviously, it directly contradicts the time-reversal invariance of all other laws (or, time-charge-parity reversal invariance if you want to be pedantic) which allows us to construct a system where it doesn't hold from every system where it does.

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But it is a very strong statistical law. You will not, for example, get a patent on the basis of demonstrated short-term violations of the second law of thermodynamics.The second law is actually just a statistical observation and not a real physical law, and is not true in every case.

Consider a box that contains molecules of gas. Imagine there is a plane that splits the box into two halves. What are the probabilities that all of the molecules are in the same half of the box, and that the two halves of the box contain more or less the same number of molecules? If there is only one molecule of gas in the box, the probabilities are tautologically 100% and 0%. Add another molecule. The probabilities are now 50% and 50%. The probability that all molecules are in the same half drops precipitously as you add more and more molecules to the box while the probability of a nearly equal distribution rises. With a mole of molecules, the first probability is essentially zero, the latter, essentially 100%.

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