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Maybe the experimental apparatus is not objective. The quantities we choose to measure are dictated by our psychological and physiological limitations. The volu

Maybe the experimental apparatus is not objective. The quantities we choose to measure are dictated by our psychological and physiological limitations. The volume of a container is not objectively defined. An organism which lives at a faster time scale will see the walls of the container vibrating and oscillating. You must convince the organism to average these measurements over a certain time scale. This averaging throws away information. This is the same with other thermodynamic quantities.

deleted 2y ago
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kergonath 2y ago
> The quantities we choose to measure are dictated by our psychological and physiological limitations. No. The enthalpy changes measured by a calorimeter are not dependent on our psychological limitations. > The volume of a container is not objectively defined. Yes, it is, for any reasonable definition of "objective". We know how to measure lengths, we know how they change when we use different frames of reference so there is no situation in which a volume is subjective. > An organism which lives at a faster time scale will see the walls of the container vibrating and oscillating. This does not matter. We defined a time scale from periodic physical phenomena, and then we know how time changes depending on the frame of reference. There is no subjectivity in this, whatever is doing the measurement has no role in it. Time does not depend on how you feel. It’s Physics, not Psychology. > This is the same with other thermodynamic quantities. No, it’s really not. You seem to know just enough vocabulary to be dangerous and I encourage you to read an introductory Physics textbook.
- notfed 2y ago
  Sometimes I wish HN had merit badges. Or if you like, a device to measure the amount of information contained within a post.
  - kergonath 2y ago
    I am not sure it would help, I think it would just enhance groupthink. I like how you need to write something obviously stupid or offensive for the downvotes to have a visible effect and that upvotes have no visible effect at all. (Yes, it changes ranking, but there are other factors). People are less prejudiced when they read the comment than if they see that it is already at -3 or +5. Yes, it means that some posts should be more (or less) visible than they are but overall I think it’s a good balance. Besides, I am not that interested in the absolute amount of information in a post. I want information that is relevant to me, and that is very subjective :)
- whatshisface 2y ago
  The enthalpy changes measured by a calorimeter are dependent on the design of the calorimeter, which could have been a different piece of equipment. In a sense, that makes it dependent on the definition of enthalpy. If you introduced a new bit of macro information to the definition of an ensemble, you'd divide the number of microstates by some factor. That's the micro level equivalent of macroscopic entropy being undefined up to an additive constant. The measurables don't tell you S, they only tell you dS.
  - kergonath 2y ago
    > The enthalpy changes measured by a calorimeter are dependent on the design of the calorimeter, which could have been a different piece of equipment. Right, but that is true of anything. Measuring devices need to be calibrated and maintained properly. It does not make something like a distance subjective, just because someone is measuring it in cm and someone else in km. > If you introduced a new bit of macro information to the definition of an ensemble, you'd divide the number of microstates by some factor. That's the micro level equivalent of macroscopic entropy being undefined up to an additive constant. It would change the entropy of your model. An ensemble in statistical Physics is not a physical object. It is a mental construct and a tool to calculate properties. An actual material would have whatever entropy it wants to have regardless of any assumptions we make. You would just find that the entropy of the material would match the entropy of one of the models better than the other one. If you change your mind and re-run the experiment, you’d still find the same entropy. This happens e.g. if we assume that the experiment is at a constant volume while it is actually under constant pressure, or the other way around. > In a sense, that makes it dependent on the definition of enthalpy. Not really. A joule is a joule, a kelvin is a kelvin, and the basic laws of thermodynamics are some of the most well tested in all of science. The entropy of a bunch of atoms is not more dependent on arbitrary definitions than the energy levels of the atoms. > The measurables don't tell you S, they only tell you dS. That’s true in itself, the laws of Thermodynamics are invariant if we add a constant term to the entropy. But it does not mean that entropy is subjective: two observers agreeing that the thing they are observing has an entropy of 0 at 0 K will always measure the same entropy in the same conditions. And it does not mean that actual entropy is dependent on specific assumptions about the state of the thing. This is also true of energy, and electromagnetic potentials (and potentials in general). This is unrelated to entropy being something special or subjective.

deleted 2y ago

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kergonath 2y ago

> The quantities we choose to measure are dictated by our psychological and physiological limitations. No. The enthalpy changes measured by a calorimeter are not dependent on our psychological limitations. > The volume of a container is not objectively defined. Yes, it is, for any reasonable definition of "objective". We know how to measure lengths, we know how they change when we use different frames of reference so there is no situation in which a volume is subjective. > An organism which lives at a faster time scale will see the walls of the container vibrating and oscillating. This does not matter. We defined a time scale from periodic physical phenomena, and then we know how time changes depending on the frame of reference. There is no subjectivity in this, whatever is doing the measurement has no role in it. Time does not depend on how you feel. It’s Physics, not Psychology. > This is the same with other thermodynamic quantities. No, it’s really not. You seem to know just enough vocabulary to be dangerous and I encourage you to read an introductory Physics textbook.

notfed 2y ago
Sometimes I wish HN had merit badges. Or if you like, a device to measure the amount of information contained within a post.
- kergonath 2y ago
  I am not sure it would help, I think it would just enhance groupthink. I like how you need to write something obviously stupid or offensive for the downvotes to have a visible effect and that upvotes have no visible effect at all. (Yes, it changes ranking, but there are other factors). People are less prejudiced when they read the comment than if they see that it is already at -3 or +5. Yes, it means that some posts should be more (or less) visible than they are but overall I think it’s a good balance. Besides, I am not that interested in the absolute amount of information in a post. I want information that is relevant to me, and that is very subjective :)
whatshisface 2y ago
The enthalpy changes measured by a calorimeter are dependent on the design of the calorimeter, which could have been a different piece of equipment. In a sense, that makes it dependent on the definition of enthalpy. If you introduced a new bit of macro information to the definition of an ensemble, you'd divide the number of microstates by some factor. That's the micro level equivalent of macroscopic entropy being undefined up to an additive constant. The measurables don't tell you S, they only tell you dS.
- kergonath 2y ago
  > The enthalpy changes measured by a calorimeter are dependent on the design of the calorimeter, which could have been a different piece of equipment. Right, but that is true of anything. Measuring devices need to be calibrated and maintained properly. It does not make something like a distance subjective, just because someone is measuring it in cm and someone else in km. > If you introduced a new bit of macro information to the definition of an ensemble, you'd divide the number of microstates by some factor. That's the micro level equivalent of macroscopic entropy being undefined up to an additive constant. It would change the entropy of your model. An ensemble in statistical Physics is not a physical object. It is a mental construct and a tool to calculate properties. An actual material would have whatever entropy it wants to have regardless of any assumptions we make. You would just find that the entropy of the material would match the entropy of one of the models better than the other one. If you change your mind and re-run the experiment, you’d still find the same entropy. This happens e.g. if we assume that the experiment is at a constant volume while it is actually under constant pressure, or the other way around. > In a sense, that makes it dependent on the definition of enthalpy. Not really. A joule is a joule, a kelvin is a kelvin, and the basic laws of thermodynamics are some of the most well tested in all of science. The entropy of a bunch of atoms is not more dependent on arbitrary definitions than the energy levels of the atoms. > The measurables don't tell you S, they only tell you dS. That’s true in itself, the laws of Thermodynamics are invariant if we add a constant term to the entropy. But it does not mean that entropy is subjective: two observers agreeing that the thing they are observing has an entropy of 0 at 0 K will always measure the same entropy in the same conditions. And it does not mean that actual entropy is dependent on specific assumptions about the state of the thing. This is also true of energy, and electromagnetic potentials (and potentials in general). This is unrelated to entropy being something special or subjective.