Second law of thermo on a macroscopic scale

[flatmaster]

Thermodynamics makes good predictions for macroscopic experiments, but the actual physics is going on in the microscopic particular level.

The second law of thermo is often thrown around, usually by people who couldn't explain F=ma back to you.

My question is the way the second law used on the macroscopic scale ever relevant? I mean can it ever be used in a context where the mechanism for it's action is not on the microscopic particular level?

 

[buffordboy23]

Your thinking is kind of confusing. Initially, thermodynamics was worked out on macroscopic scales, so it must have been relevant. Later, the microscopic aspects (e.g. quantum states) were worked out and supported the macroscopic results. This is why it's such a successful theory.

Do you actually mean something different?

 

[astrokreng]

I understand your skepticism about the relevance of the second law of thermodynamics on a macroscopic scale. However, I assure you that the second law is just as applicable on a macroscopic scale as it is on a microscopic scale. In fact, it is precisely because of the interactions of microscopic particles that the second law can be observed and applied on a larger scale.

While it is true that the actual physics of thermodynamics occurs at the microscopic level, the second law is a fundamental principle that governs the behavior of macroscopic systems. This law states that in any closed system, the total entropy (or disorder) will always increase over time. This means that while individual particles may be moving in a seemingly random manner, the overall system will tend towards a state of higher entropy.

To give an example, think of a cup of hot coffee placed in a room at room temperature. The second law tells us that the heat from the coffee will naturally flow out into the room, eventually reaching a state of thermal equilibrium where the temperature of the coffee and the room are the same. This is a macroscopic observation that can be explained by the interactions of individual particles at the microscopic level.

So, to answer your question, yes, the second law of thermodynamics is relevant on a macroscopic scale and can be used in contexts where the mechanism for its action is not immediately visible. It is a fundamental principle that helps us understand and predict the behavior of complex systems, and its applicability extends beyond just the microscopic level.