7 ms·

I think the point is the model though - if a system's behavior can be modeled/described classically, it's a bit silly to to call it a "quantum" system in the sa

I think the point is the model though - if a system's behavior can be modeled/described classically, it's a bit silly to to call it a "quantum" system in the same way that it's reductive to say Biology is just applied particle physics. Sure, but that's not a very useful level of abstraction.

jessriedel 2y ago
If you want to understand the transition between a fundamental theory and its effective description in some limiting regime, you need to be able to describe a system in the limiting regime using the fundamental theory. It's not "silly" to talk about an atom having a gravitational field even if it's unmeasurably small (currently).
- empyrrhicist 2y ago
  Lol, so you've got a working theory to bridge the quantum and classical worlds? That is, you've figured out how to make general relativity and quantum mechanics emerge from a more fundamental theory? Somebody get this person a Nobel! We're at the phase where we know the world is quantum, but we also simply don't have the ability to bridge that set of observable phenomena to what we know about macroscopic things. That's what makes this exercise "silly".
  - nico 2y ago
    No need to be sarcastic. We are trying to develop ideas and have a conversation We are not trying to prove who is right and who is wrong Regardless of whatever the mainstream agreement in physics might be regarding a preferred model for reality, everyone experiences reality directly, without any need for science or math. And they can express those experiences and ideas in their own way If you don’t agree with someone else’s ideas, please just explain why politely, and also maybe even try to understand their point of view. What would things look like if they were actually right? How might theirs be a good idea? Thank you
    - empyrrhicist 2y ago
      I'm not trying to be mean, it just struck me as kind of a funny position. "If you want to understand the transition between a fundamental theory and its effective description in some limiting regime, you need to be able to describe a system in the limiting regime using the fundamental theory" Like, that's well and good, but in general we just can't do that without hand-waving, period. This is true all over the place (biology/physics, psychology/neuroscience/physics). It's sort of true, but not in a useful way.
      - jessriedel 2y ago
        Rigorous things can be done in physics and mathematics, and the fields benefit greatly from this.
        empyrrhicist 2y ago
        What does that even mean, and how is it a response to my point that choosing an appropriate level of abstraction for the problem at hand is a good idea?
        jessriedel 2y ago
        You said > in general we just can't [describe a system in the limiting regime using the fundamental theory] without hand-waving, period...It's sort of true, but not in a useful way. And I am saying that it in fact can be done, and has been done, in physics and math in a very non-hand-waving way. One can show rigorously when a certain abstractions is accurate.
        empyrrhicist 2y ago
        Well... sure, but I think you're still almost purposely missing the point. Take this example - can we prove that a system of differential equations emerges in a meaningful way from discrete systems? Yes, obviously. That's a far cry from the OP's "if you think about it, all things are quantum", which is where this thread started and what I'm talking about. It also illustrates the actual point pretty well - when you have a good set of differential equations that describe observed phenomena, that higher level of abstraction gives MORE insight into the processes at play, even when we know that it emerges from something more fundamental. Only when that model is a poor approximation do we need to appeal to the more fundamental regime (or when that fundamental regime is what we're studying).
  - jessriedel 2y ago
    You're confusing the quantum-classical transition with the quantum-gravity to classical-gravity transition. (People understood the relativistic-Galilean transition before they understood the QFT-classical-field-theoy transition.)

jessriedel 2y ago

If you want to understand the transition between a fundamental theory and its effective description in some limiting regime, you need to be able to describe a system in the limiting regime using the fundamental theory. It's not "silly" to talk about an atom having a gravitational field even if it's unmeasurably small (currently).

empyrrhicist 2y ago
Lol, so you've got a working theory to bridge the quantum and classical worlds? That is, you've figured out how to make general relativity and quantum mechanics emerge from a more fundamental theory? Somebody get this person a Nobel! We're at the phase where we know the world is quantum, but we also simply don't have the ability to bridge that set of observable phenomena to what we know about macroscopic things. That's what makes this exercise "silly".
- nico 2y ago
  No need to be sarcastic. We are trying to develop ideas and have a conversation We are not trying to prove who is right and who is wrong Regardless of whatever the mainstream agreement in physics might be regarding a preferred model for reality, everyone experiences reality directly, without any need for science or math. And they can express those experiences and ideas in their own way If you don’t agree with someone else’s ideas, please just explain why politely, and also maybe even try to understand their point of view. What would things look like if they were actually right? How might theirs be a good idea? Thank you
  - empyrrhicist 2y ago
    I'm not trying to be mean, it just struck me as kind of a funny position. "If you want to understand the transition between a fundamental theory and its effective description in some limiting regime, you need to be able to describe a system in the limiting regime using the fundamental theory" Like, that's well and good, but in general we just can't do that without hand-waving, period. This is true all over the place (biology/physics, psychology/neuroscience/physics). It's sort of true, but not in a useful way.
    - jessriedel 2y ago
      Rigorous things can be done in physics and mathematics, and the fields benefit greatly from this.
      - empyrrhicist 2y ago
        What does that even mean, and how is it a response to my point that choosing an appropriate level of abstraction for the problem at hand is a good idea?
        jessriedel 2y ago
        You said > in general we just can't [describe a system in the limiting regime using the fundamental theory] without hand-waving, period...It's sort of true, but not in a useful way. And I am saying that it in fact can be done, and has been done, in physics and math in a very non-hand-waving way. One can show rigorously when a certain abstractions is accurate.
        empyrrhicist 2y ago
        Well... sure, but I think you're still almost purposely missing the point. Take this example - can we prove that a system of differential equations emerges in a meaningful way from discrete systems? Yes, obviously. That's a far cry from the OP's "if you think about it, all things are quantum", which is where this thread started and what I'm talking about. It also illustrates the actual point pretty well - when you have a good set of differential equations that describe observed phenomena, that higher level of abstraction gives MORE insight into the processes at play, even when we know that it emerges from something more fundamental. Only when that model is a poor approximation do we need to appeal to the more fundamental regime (or when that fundamental regime is what we're studying).
- jessriedel 2y ago
  You're confusing the quantum-classical transition with the quantum-gravity to classical-gravity transition. (People understood the relativistic-Galilean transition before they understood the QFT-classical-field-theoy transition.)