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Aidyan

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- Thread starter Aidyan
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In summary: In the context of thermodynamics, this is the phenomena where particles or systems approach a so-called "critical point", at which changes in the system's properties become irreversible and far-reaching.

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Aidyan

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For me the very immediate discovery is the necessity to assume the indistinguishability of particles, because otherwise entropy turns out to be not an extensive quantity as it should be (Gibbs's paradox).

Also statistical physics and thermodynamics helped to discover that the classical models are all inadequate to understand matter on a fundamental level and that quantum theory is needed. Of course, that's true from the very birthday of quantum theory, which is December 14, 1900 when Planck introduced the quantization of the exchange energy of electromagnetic waves with matter to explain the black-body spectrum, which he discovered before by analyzing the high-precision measurements by Rubens and Kurlbaum at the Phyikalisch-Technische Reichsanstalt. This was famously further worked out by Einstein, leading to the idea of "wave-particle duality" for em. waves and later also of "particles" like the electron, which finally lead to the development of modern quantum theory, and only with quantum theory all the fundamental laws of thermodynamics, particularly the third Law (Nernst's Law) can be explained.

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marcusl

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There are also specific problems that can only be solved statistically. For instance, if the motion of gas molecules is random, why doesn't the air in the room you are sitting in occasionally and randomly move to the opposite side, leaving you gasping? Stat mech gives the answer in terms of numbers of microstates, which lead to probabilities. The probability of that happening is something like 10^-80, which is so stupendously small that we needen't worry--we can "breathe easy." (If we checked the air every microsecond during the 4.5 billion year age of earth, that's still only 10^23 opportunities for a suffocation event. Checking a million rooms on a million earth-like planets gets us up only to 10^34. We'd need to wait another 10^46 microseconds or another 10^32 years to expect to see one event. We can say that the probability of occurence is indistinguishable from impossible.)

Similar considerations describe the reasoning behind the 2nd law of thermodynamics and the arrow of time. The 2nd law isn't actually a law that entropy can never increase, but a statement of improbability that involves numbers so fantastically small that it might as well be a certainty. As for the time arrow, the reason that a gas let out of a container into a room doesn't randomly return to the container is due to the same improbabilities. Time reversal is not impossible in a system at equilibrium, but it might as well be.

Similar considerations describe the reasoning behind the 2nd law of thermodynamics and the arrow of time. The 2nd law isn't actually a law that entropy can never increase, but a statement of improbability that involves numbers so fantastically small that it might as well be a certainty. As for the time arrow, the reason that a gas let out of a container into a room doesn't randomly return to the container is due to the same improbabilities. Time reversal is not impossible in a system at equilibrium, but it might as well be.

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andresB

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Aidyan said:...and especially if it was able to explain properties of matter that in the conventional thermodynamic theory were previously not explainable? If so which?

Thermal Fluctuations.

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atyy

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Aidyan said:and especially if it was able to explain properties of matter that in the conventional thermodynamic theory were previously not explainable? If so which?

Classical statistical mechanics is able to explain universality in critical phenomena, and calculate the critical exponents.

Classical statistical physics is a branch of physics that studies the behavior of large systems of particles using statistical methods. It is based on the laws of classical mechanics and is used to explain the macroscopic properties of matter. On the other hand, thermodynamics is a branch of physics that deals with the relationships between heat, energy, and work. It is based on the laws of thermodynamics and is used to study the behavior of macroscopic systems in equilibrium.

Yes, classical statistical physics can predict newer phenomena. It is a powerful tool that has been used to explain a wide range of phenomena, from the behavior of gases to the properties of solids and liquids. By using statistical methods, classical statistical physics can make predictions about the behavior of large systems of particles, even if the individual particles are not well understood.

Yes, thermodynamics can predict newer phenomena. It is a fundamental theory that has been used to explain many natural processes, such as phase transitions, chemical reactions, and heat transfer. Thermodynamics provides a framework for understanding the behavior of macroscopic systems and can make predictions about their properties and behavior.

Classical statistical physics and thermodynamics are closely related and work together to explain the behavior of physical systems. Classical statistical physics uses statistical methods to describe the behavior of large systems, while thermodynamics provides the laws that govern the behavior of these systems. Together, they provide a comprehensive understanding of the macroscopic properties of matter.

No, classical statistical physics and thermodynamics have their limitations and cannot be applied to all physical systems. They are most effective in describing macroscopic systems in equilibrium, and may not be applicable to systems that are far from equilibrium or at the quantum scale. In these cases, other branches of physics, such as quantum mechanics, must be used to accurately describe the behavior of the system.

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