3 ms·

> can the "result" of any thought experiment be surprising, not what you expected? Isn't Schrödinger's cat the classic example of this? Physicists at the time

by n4r9 4y ago

> can the "result" of any thought experiment be surprising, not what you expected? Isn't Schrödinger's cat the classic example of this? Physicists at the time typically thought of quantum effects (like superposition) as being confined to the microscopic realm. Schrödinger pointed out that if you take the principles of quantum theory as serious and objectively ontological, then you end up with macroscopic superpositions.

narag 4y ago
The problem is that you can't know if the cat is dead or alive unless you open the box. Schrödinger conceived the experiment to "show" that the premises lead to an absurd result: that the cat is dead and alive at the same time. But now people either consider it plausible (in multiple universes or depending on observer) or try to explain how superposition is lost before it reaches macroscopic objects.
- n4r9 4y ago
  Right, I agree with everything you say. To me that means the thought experiment was extremely valuable, because it generated a great refinement of our ontological ideas.
  - narag 4y ago
    It's funny because the author's idea was to discredit the notion altogether, so it's relevant because it failed to do that. The core of Mary's adventures is a false dicotomy: that matter is the only component of physical reality. But processes, structure and energy flow are as real as matter. Actually, at a very small scale, matter seems to be exactly that. So as usual with all these dualism "enigmas", the only problem is starting from an old perspective that doesn't play well with current knowledge. Consciousness seems to be a complex physical process seen from inside itself. There's no mistery or toughness in that, except that we can't compare it with anything else. We can't use the inside and ouside outlooks at the same time. But Wittgenstein already stated that more than a century ago.
    - n4r9 4y ago
      But... none of this makes thought experiments any less helpful or valid. If anything, the fact that Schrodinger's cat achieved the opposite goal implies that it touched on hidden fundamentals in quantum theory.
MrPatan 4y ago
Why is the cat never assumed to be able to be an observer? Or the flask with poison? I always assumed everybody understood "observer" to be shorthand for "some entity that irrevocably changes state because of the quantum events", but I'm starting to realize that lots of people, even the famous physicists responsible for the theories and experiments, may understand "observer" as "Human being, with a conciousness". I'm just a layman with a layman's understanding of quantum shenannigans, but.... am I too far off here?
- n4r9 4y ago
  > some entity that irrevocably changes state because of the quantum events Yes, "observer" is ambiguous at best. One query with your proposed definition is: what do you mean by "irrevocable"? If you believe that the quantum state (wavefunction) is objective and independent - and does not collapse but evolves reversibly according to the Schrodinger equation - then nothing is irrevocable, it's just a technical challenge of "can we reverse the evolution of this patch of the universe". Yes, there is this decoherence process, but even that is reversible if you expand your "patch of the universe" sufficiently. Not many famous physicists believe human consciousness is required for a physical quantum collapse process to occur. John Bell put it nicely: > Was the wave function waiting to jump for thousands of millions of years until a single-celled living creature appeared? Or did it have to wait a little longer for some highly qualified measurer—with a PhD? You might be interested to know that people have wondered about what happens if you replace the cat by something that is definitely an "observer": https://en.wikipedia.org/wiki/Wigner%27s_friend https://en.wikipedia.org/wiki/Wigner%27s_friend . Until the friend (F) tells Wigner (W) the outcome that he experienced when measuring a photon (P), then Wigner supposes that F is quantum entangled with P, i.e. they are in a joint superposition of states. However, the friend supposes that P is in a definite state.
  - MrPatan 4y ago
    > what do you mean by "irrevocable"? Very good point, who knows! I guess whatever the universe can't pretend didn't happen, like a photon being absorbed and re-emited by an electron. Which, what does that even mean? I don't know! Does anyone? I don't know!

by n4r9 4y ago

narag 4y ago

The problem is that you can't know if the cat is dead or alive unless you open the box. Schrödinger conceived the experiment to "show" that the premises lead to an absurd result: that the cat is dead and alive at the same time. But now people either consider it plausible (in multiple universes or depending on observer) or try to explain how superposition is lost before it reaches macroscopic objects.

n4r9 4y ago
Right, I agree with everything you say. To me that means the thought experiment was extremely valuable, because it generated a great refinement of our ontological ideas.
- narag 4y ago
  It's funny because the author's idea was to discredit the notion altogether, so it's relevant because it failed to do that. The core of Mary's adventures is a false dicotomy: that matter is the only component of physical reality. But processes, structure and energy flow are as real as matter. Actually, at a very small scale, matter seems to be exactly that. So as usual with all these dualism "enigmas", the only problem is starting from an old perspective that doesn't play well with current knowledge. Consciousness seems to be a complex physical process seen from inside itself. There's no mistery or toughness in that, except that we can't compare it with anything else. We can't use the inside and ouside outlooks at the same time. But Wittgenstein already stated that more than a century ago.
  - n4r9 4y ago
    But... none of this makes thought experiments any less helpful or valid. If anything, the fact that Schrodinger's cat achieved the opposite goal implies that it touched on hidden fundamentals in quantum theory.

MrPatan 4y ago

Why is the cat never assumed to be able to be an observer? Or the flask with poison? I always assumed everybody understood "observer" to be shorthand for "some entity that irrevocably changes state because of the quantum events", but I'm starting to realize that lots of people, even the famous physicists responsible for the theories and experiments, may understand "observer" as "Human being, with a conciousness". I'm just a layman with a layman's understanding of quantum shenannigans, but.... am I too far off here?

n4r9 4y ago
> some entity that irrevocably changes state because of the quantum events Yes, "observer" is ambiguous at best. One query with your proposed definition is: what do you mean by "irrevocable"? If you believe that the quantum state (wavefunction) is objective and independent - and does not collapse but evolves reversibly according to the Schrodinger equation - then nothing is irrevocable, it's just a technical challenge of "can we reverse the evolution of this patch of the universe". Yes, there is this decoherence process, but even that is reversible if you expand your "patch of the universe" sufficiently. Not many famous physicists believe human consciousness is required for a physical quantum collapse process to occur. John Bell put it nicely: > Was the wave function waiting to jump for thousands of millions of years until a single-celled living creature appeared? Or did it have to wait a little longer for some highly qualified measurer—with a PhD? You might be interested to know that people have wondered about what happens if you replace the cat by something that is definitely an "observer": https://en.wikipedia.org/wiki/Wigner%27s_friend https://en.wikipedia.org/wiki/Wigner%27s_friend . Until the friend (F) tells Wigner (W) the outcome that he experienced when measuring a photon (P), then Wigner supposes that F is quantum entangled with P, i.e. they are in a joint superposition of states. However, the friend supposes that P is in a definite state.
- MrPatan 4y ago
  > what do you mean by "irrevocable"? Very good point, who knows! I guess whatever the universe can't pretend didn't happen, like a photon being absorbed and re-emited by an electron. Which, what does that even mean? I don't know! Does anyone? I don't know!