collapsing quantum wave function

From: Norman Samish <>
Date: Thu, 9 Jun 2005 16:09:15 -0700

Jonathan Colvin wrote: "If I take a loaf of bread, chop it half, put one
half in one room and one half in the other, and then ask the question "where
is the loaf of bread?", we can likely agree that the question is ill-posed."

Depending on definitions, this may indeed be an ill-posed question. On the
other hand, with appropriate definitions, the question might be answered by
"The loaf is half in one room and half in the other," or "The loaf no longer

This reminds me of my problems trying to understand "the collapsing quantum
wave function." I've heard of Schrödinger's Cat, which I'm told is half
alive - half dead until the box is opened and the cat is observed. This
observation "collapses the quantum wave function," and the cat at that point
is either alive or dead.

Here's a variation. Is my interpretation correct?

Suppose we take ten apparently identical ball bearings and put stickers on
each with the identifiers "1" through "10." We leave the room where the
balls with stickers are, and a robot removes the stickers and mixes the
balls up so that we don't which ball is which. However, the robot remembers
which sticker belongs on which ball. We come back into the room and pick
one ball at random to destroy by melting it in an electric furnace. If at
this point we ask "What is the probability that the destroyed ball is ball
'3'?" we can truthfully answer "My memory tells me that the destroyed ball
has a one in ten probability of being '3.' "

However, by reviewing the robot's record we can see that "6" was, in fact,
the one destroyed.

Does this mean that the quantum wave functions of all ten balls collapsed at
the moment we viewed the record and observed what happened to "6"? Or did
the wave function never exist, since the robot's record always showed the
identity of the destroyed ball, irrespective of whether a human observed
this identity or not?
Received on Thu Jun 09 2005 - 19:15:28 PDT

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