Freethought & Rationalism Archive

Normal · 08-04-2003, 08:49 PM

Schr�dinger's cat

Why is the cat not considered an observer?

Kat_Somm_Faen · 08-04-2003, 09:01 PM

Hmmm well does a particle count as "knowing" if it exists?

Analogies break down at certain levels, of course. And what if the cat is dead?

This is reall just trying to explain "our" point of view.

Normal · 08-04-2003, 09:03 PM

Why not?

The screen that an interference pattern shows up on in the double slit experiement is considered an "observer".

echidna · 08-04-2003, 09:44 PM

It just depends how wide you want to cast your wave equation. Aquinas might have said that it encompassed the entire universe. Mind you, that's one hell of a wave equation.

Jesse · 08-04-2003, 09:45 PM

All that's important is that the cat is completely isolated from interactions with the outside world which could transmit information about its state to observers outside (such isolation of macroscopic systems is not really possible in practice, although perhaps we could imagine a cat simulated on a quantum computer). As long as a system is isolated, the outside world should treat it as being in a superposition of states, regardless of whether the system is a cat or a human being...see the "Wigner's friend" thought-experiment:

http://www.wikipedia.org/wiki/Wigner's_friend

Normal · 08-04-2003, 09:50 PM

Quote:

Originally posted by echidna
It just depends how wide you want to cast your wave equation.

But the only wave equation relevent is the one interacting with the geiger counter, which the cat can observe.

Normal · 08-04-2003, 09:52 PM

Quote:

Originally posted by Jesse
All that's important is that the cat is completely isolated from interactions with the outside world which could transmit information about its state to observers outside (such isolation of macroscopic systems is not really possible in practice, although perhaps we could imagine a cat simulated on a quantum computer). As long as a system is isolated, the outside world should treat it as being in a superposition of states, regardless of whether the system is a cat or a human being...see the "Wigner's friend" thought-experiment:

http://www.wikipedia.org/wiki/Wigner's_friend

But why isn't the cat a good enough observer to know that the geiger counter has been triggered and the poison gas killed it? Why can't the cat observe it's own death?

Wyz_sub10 · 08-04-2003, 10:05 PM

Quote:

Originally posted by Normal
But why isn't the cat a good enough observer to know that the geiger counter has been triggered and the poison gas killed it? Why can't the cat observe it's own death?

I thought it had been recognized that this example was a problem, as the cat is indeed an observer.

Normal · 08-04-2003, 10:09 PM

Quote:

Originally posted by Wyz_sub10
I thought it had been recognized that this example was a problem, as the cat is indeed an observer.

What effect does this have on the MWI ?

Kat_Somm_Faen · 08-04-2003, 10:10 PM

A dead cat can "observe" in the lose definition of the word. Its molecules are experincing stuff happen - like rotting.

This is meant to be an a-n-a-l-o-g-y not a real thing. Analogy can not present the entire set of counsequences in a situation.

If a particle with no self-awarenes can "observe" so can a dead cat too.

But the cat is taken as a single entity in a sense it is isolated from the "observer" ie. guy outside of a box.

08-04-2003, 08:49 PM	#1
Normal Senior Member Join Date: May 2003 Location: Canada Posts: 639	Schr�dinger's ignorant cat? Schr�dinger's cat Why is the cat not considered an observer?

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08-04-2003, 09:01 PM	#2
Kat_Somm_Faen Veteran Member Join Date: Jun 2001 Location: Boulder, Colorado Posts: 3,316	Hmmm well does a particle count as "knowing" if it exists? Analogies break down at certain levels, of course. And what if the cat is dead? This is reall just trying to explain "our" point of view.

08-04-2003, 09:03 PM	#3
Normal Senior Member Join Date: May 2003 Location: Canada Posts: 639	Why not? The screen that an interference pattern shows up on in the double slit experiement is considered an "observer".

08-04-2003, 09:44 PM	#4
echidna Veteran Member Join Date: May 2001 Location: Melbourne, Australia Posts: 2,832	It just depends how wide you want to cast your wave equation. Aquinas might have said that it encompassed the entire universe. Mind you, that's one hell of a wave equation.

08-04-2003, 09:45 PM	#5
Jesse Moderator - Science Discussions Join Date: Feb 2001 Location: Providence, RI, USA Posts: 9,908	All that's important is that the cat is completely isolated from interactions with the outside world which could transmit information about its state to observers outside (such isolation of macroscopic systems is not really possible in practice, although perhaps we could imagine a cat simulated on a quantum computer). As long as a system is isolated, the outside world should treat it as being in a superposition of states, regardless of whether the system is a cat or a human being...see the "Wigner's friend" thought-experiment: http://www.wikipedia.org/wiki/Wigner's_friend

08-04-2003, 10:10 PM	#10
Kat_Somm_Faen Veteran Member Join Date: Jun 2001 Location: Boulder, Colorado Posts: 3,316	A dead cat can "observe" in the lose definition of the word. Its molecules are experincing stuff happen - like rotting. This is meant to be an a-n-a-l-o-g-y not a real thing. Analogy can not present the entire set of counsequences in a situation. If a particle with no self-awarenes can "observe" so can a dead cat too. But the cat is taken as a single entity in a sense it is isolated from the "observer" ie. guy outside of a box.

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