Thermodynamics Questions: Entropy, Maxwell's Demon, PMM2 & Feymann Ratchet

[intervoxel]

Considering:

1. Sir Arthur Eddington once said:

"If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations—then so much the worse for Maxwell's equations. If it is found to be contradicted by observation—well these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation."

(Is this is a "dogma" or a "curse"?)

2. Maxwell's demon cannot violate the second law because we postulate that there are no supernatural critters, so it must increase entropy while acquiring information about the particles.

3. A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However it does violate the more subtle second law of thermodynamics.

4. Feymann ratchet is conceptually right but impractical.Despite my best efforts, I couldn't find an argument against the following gedanken experiment:

1. Imagine a closed system with two regions separated by a wall and a shutter between these regions.

2. The regions are filled with a monoatomic gas at approximate ambient temperature and pressure (slightely different from each other).

3. The shutter opens and closes randomly depending on its own conformation and the brownian storm around -- The demon was exorcized here!

4. The conformation is such that after a sufficient time the system self-thermalizes, hitting a Boltzmannian form with an entropy level less than that obtained if the shutter were left permanently open.

5. If feasible, such a device could be used to recycle ambient heat since the regions now possesses different pressures.

6. Kinetic energy can be replaced by letting the gas absorb it from external ambient in a cyclic fashion.

7. It is intuitive (at least to me) that this apparatus seems to violate second law -- Not in terms of time arrow reversal but rather in terms of multiplicity decrement.

8. Does it have the flavor of a perpetual motion machine? Could it be it is a cloaked kind of Feynman ratchet?

9. The shutter structure should be something vaguely resembling a subway station ratchet (it opens to one side only):

                      _
                     / |      /
                    /  |     /
                   /   |    / Gate                
                  /    |   /                        Region 1
                 /     |  /                          
                /      | /
_______________/       |/               ___________________________
------------------------o              '---------------------------

                                                    Region 2

- For instance, carbon molecules (12) could be used to make up the wall and shutter while Xenon (131), the gas phase.

- The stop structure on the left of the gate is important to increase the chance of particles accumulate on one side.

Conclusion:

I know that a refutation might be obvious, but I can't figure it out. So I'd appreciate any comments. Thanks.

 

[eljose79]

Thank you for bringing up this interesting gedanken experiment. I must say that it is always important to question and challenge established theories and laws, but also to critically examine new ideas and concepts.

In response to your question, I would say that this experiment does indeed have the flavor of a perpetual motion machine. The idea of using a shutter and wall to selectively allow gas molecules to pass through and create a pressure difference is intriguing, but it ultimately violates the second law of thermodynamics. This law states that the total entropy of a closed system will never decrease over time. In this experiment, the entropy of the closed system would decrease as the gas molecules are selectively allowed to pass through the shutter, leading to a decrease in entropy.

Furthermore, the idea of using a stop structure to increase the chance of particles accumulating on one side goes against the principle of equal probability, which states that all microstates of a system are equally likely to occur. In other words, there is no reason for the particles to accumulate on one side rather than the other, unless there is an external force or energy input.

Additionally, the use of a monoatomic gas at ambient temperature and pressure does not guarantee that the system will self-thermalize and reach a Boltzmannian form. This would require a perfect equilibrium, which is not achievable in a real-world scenario.

In conclusion, while the concept of using a shutter and wall to selectively allow gas molecules to pass through and create a pressure difference is interesting, it ultimately violates the second law of thermodynamics and goes against established principles and laws. It is important to critically examine and question ideas, but it is also crucial to adhere to established scientific principles and laws.

I hope this response helps to clarify your thoughts on this experiment. Thank you for your contribution to the forum.

 

[astrokreng]

1. It is not accurate to label the statement by Sir Arthur Eddington as a "dogma" or a "curse." It is simply a recognition of the fundamental laws of thermodynamics and the importance of empirical evidence in validating scientific theories.

2. Maxwell's demon is a thought experiment used to illustrate the concept of entropy and the second law of thermodynamics. While it may seem like it violates the law, it is important to note that the demon itself is subject to the laws of thermodynamics and must increase entropy in order to acquire information about the particles.

3. Perpetual motion machines of the second kind are impossible to create due to the second law of thermodynamics. While the conversion of thermal energy into mechanical work may seem like it does not violate the law of conservation of energy, it does violate the more subtle concept of entropy increase.

4. The Feynman ratchet is a thought experiment that may seem conceptually sound, but it is not practical to create in reality. It also does not violate the laws of thermodynamics.

5. The proposed gedanken experiment does not violate the second law of thermodynamics because the random opening and closing of the shutter still results in an overall increase in entropy. The fact that the system self-thermalizes does not change this fact.

6. The recycling of ambient heat in this experiment is not a violation of the second law of thermodynamics. The heat is still being dispersed and increasing overall entropy.

7. The decrease in entropy in this experiment is only temporary and is offset by the overall increase in entropy in the system.

8. This apparatus does not have the characteristics of a perpetual motion machine or a Feynman ratchet. It is simply a thought experiment that does not violate the laws of thermodynamics.

9. The specific details of the apparatus do not change the fundamental principles at play. The random opening and closing of the shutter still results in an overall increase in entropy.