Talk:Wigner's friend
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[edit] Superposition
Can someone link this word in the article to what it means? Eg is it Quantum_superposition. I am trying to understand this page but am stuck on superposition. Crackerlacken
—Preceding unsigned comment added by Crackerlacken (talk • contribs) 03:48, 9 January 2008 (UTC)
I have some ideas:
1) Instead of a friend, have the machine produce either a 2 000-gram or a 2 001-gram bag of sand. You cannot tell which the bag is merely by picking it up... but will picking up the bag collapse the wave function? Will weighing the bag on an accurate scale collapse the wave function?
2) Have the machine produce a bag containing either 50 003 or 50 008 ball bearings (of non-uniform weight). Will (a human) counting the ball bearings collapse the wave function? If it is known that the person who counts the ball bearings tends to make errors in counting, will his attempt at counting still collapse the wave function? Will merely looking at each of the ball bearings in turn, without (consciously) counting them, collapse the wave function?
Suppose we have a machine count the ball bearings. Let us say that it is a mechanical device, with a mechanical counter. If you look at all of the digits of the counter except the last digit, will this collapse the wave function? If you look at the right-hand half of the right hand digit (since "3" and "8" have similar-looking right-hand halves), will this collapse the wave function?
Number 2 is not at all what I call farfetched. I have, at times, tried counting things several times, and got different answers. I began to honestly wonder if the number of (macroscopic) items in a bag had to be "fixed", or if it could be "fuzzy" in a quantum sort of way.
[edit] "Alive cat" as direct quote?
There is the line "alive cat/happy friend,". Was the term "alive cat" actually used in any source material? Typically English treats "alive" as a predicate adjective which may not precede a noun; we would rather say "the living cat" or "the cat is alive", but not "the alive cat". samwaltz 19:18, 18 January 2007 (UTC)
[edit] Amend second par for clarity
The following par was the 2nd one of this article. I have replaced it with the one below it, for reasons given at the end.
It posits a friend of Wigner who performs the Schrödinger's cat experiment while Wigner is out of the room. Only when Wigner comes into the room does he himself know the result of the experiment: until this point, was the state of the system a superposition of "dead cat/sad friend" and "alive cat/happy friend," or was it determined at some previous point?
It posits a friend of Wigner who performs the Schrödinger's cat experiment after Wigner leaves the laboratory. Only when he returns does Wigner learn the result of the experiment from his friend, that is, whether the cat is alive or dead. The question is raised: was the state of the system a superposition of "dead cat/sad friend" and "live cat/happy friend," that was only determined when Wigner learnt the result of the experiment, or was it determined at some previous point?
1.“he himself” is confusing. It is not immediately apparent whether the pronoun refers to Wigner or his friend. I have made “he” unambiguously refer to Wigner.
2. I have made it manifest that Wigner learns the result of the experiment from his friend, not from direct observation.
3.I have remedied stylistic awkwardness of last part of sentence.
4.I have substituted “live cat” for “alive cat”. Myles325a 02:29, 17 August 2007 (UTC)
[edit] What about the consciousness of Wigner's friend?
An element of this thought experiment that I found puzzling is that it is Wigner's friend who first learns of the result of the experiment. If thought experiment is designed to illustrate that consciousness has a privileged function in collapsing the wave function, then is it not Wigner who collapses it first? In that case, Wigner has come too late to collapse it himself.
Otoh, suppose Wigner's friend had no idea of what the experiment involves. He only has to push a hutton, and tear off a print-out produced automatically by a printer attached to the box, upon the completion of the experiment. This printout contains a coded message detailing the result of the experiment. In such a case, we might posit that if Wigner's friend can read and understand the message, the act of reading collapses the wave function and the cat can be said to definitely dead or alive. But if he cannot, then it is Wigner himself who collapses the wave function when he returns and reads the printout himself. Myles325a 02:59, 17 August 2007 (UTC)
[edit] Recent Rewrite
The recent re-write is not good. It is completely idiosyncratic and reads like a personal essay. 1Z (talk) 22:17, 10 January 2008 (UTC)
[edit] What the hell is a bad world count?
I'm not asking for a lecture on MW. I've been studying it for years, and I'v eenver heard the term. 1Z (talk) 22:31, 10 January 2008 (UTC)
