5 ms·

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 "som

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!
- MrPatan 4y ago
  And thanks for engaging with the question. Another problem I have with this is I never see this problems spelled out. It's hard to tell, with such difficult subjects, the difference between "I don't know" and "Nobody knows". On top of that, people like to pretend they know. And some other people do really believe they know even if they don't, just because they know a dictionary definition, or something.

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!
MrPatan 4y ago
And thanks for engaging with the question. Another problem I have with this is I never see this problems spelled out. It's hard to tell, with such difficult subjects, the difference between "I don't know" and "Nobody knows". On top of that, people like to pretend they know. And some other people do really believe they know even if they don't, just because they know a dictionary definition, or something.