A SECOND LOOK AT THE SECOND LAW : CAN ANYTHING HAPPEN IN AN OPEN SYSTEM ?

Math Dept., Texas A&M University ^ | Granville Sewell

[Doctor Stochastic]

Perhaps I'm not being clear. The entropy of a system in a given state does not depend on the path the system takes to get to that state.

A system may proceed from state (T1,V1) to (T2,V2) by reversible, random, irreversible, deterministic or any other process. The entropy at (T2,V2) will be the same no matter what path is taken.

[grey_whiskers]

The author is merely assuming "air" and adds that it is a 'simple' example. While some elements of air are monatomic (ex noble gases), the other elements (obviously more) are diatomic elements hydrogen, nitrogen, oxygen etc...

Sigh. Have you ever heard of quantum mechanics, and quantization of rotation or vibration of polyatomic molecules?

There are partition functions to describe the relative populations of molecules in the various internal states, too.

This is important because the molecules can exchange energy with one another (including changing their translational kinetic energy) upon collisions.

In other words, stating merely the velocity and positions of the molecules is not enough to specify the exact state of the system precisely. Only to a certain degree of approximation...which is why I mentioned monatomic gases.

Thermodynamics can be used to describe the probability of a certain arrangements of entities compared to another, and which general direction those arrangments are most likely to move in without interference.

In particular, the assumption is made of so-called "equal a priori probabilities". That is, all of the microstates are assumed to be "equally likely"--energetic considerations excluded. Then for each different macrostate, there is some set of microstates which gives rise to that macrostate. The idea being that the macrostates which have the largest number of contributing microstates yada yada. There is an analogy to the combinatorics of arriving at a given total when rolling a pair of dice, but on a much larger scale.

There is an Organizer outside of nature who interfered when the world was created.

I agree completely, but the sentence seems like a non-sequitur given the rest of your post. For the nonce, what is problematical is that the physical evidence which we have of the Earth and the cosmos does not match what we would expect from things, *if* the Creator made them in the way some folks interpret Genesis, *and* if we assume that the laws of nature (including physics, chemistry, etc.) have remained in operation in their present form from the word GO.

Cheers!

[FreedomProtector]

"In other words, stating merely the velocity and positions of the molecules is not enough to specify the exact state of the system precisely. Only to a certain degree of approximation...which is why I mentioned monatomic gases."

I believe the author was providing a simplified example for conceptual learning, not a precise definition or a precise description.

In particular, the assumption is made of so-called "equal a priori probabilities". That is, all of the microstates are assumed to be "equally likely"--energetic considerations excluded. Then for each different macrostate, there is some set of microstates which gives rise to that macrostate. The idea being that the macrostates which have the largest number of contributing microstates yada yada. There is an analogy to the combinatorics of arriving at a given total when rolling a pair of dice, but on a much larger scale.

Partition functions serve the purpose of not overcounting microstates.