biep@cs.vu.nl (J. A. "Biep" Durieux) (06/18/87)
Thought this should be in sci.philosophy.tech (found in sci.physics). This article was <2182@mmintl.UUCP> from franka@mmintl.UUCP (Frank Adams). In article <587@sri-arpa.ARPA> JOHNSON%nuhub.acs.northeastern.edu@RELAY.CS.NET writes: >From: "I am only an egg." <JOHNSON%nuhub.acs.northeastern.edu@RELAY.CS.NET> > > 1) I create two half-wits, one is looking up the other down and > > 2) One hangs around where I will be able two measure it someday > while the other one takes off for parts unknown and > > 3) After a long time, less than the half-wit decay time, I measure > the one that stayed behind AND > > 4) VERY IMPORTANT: THERE WERE NO INTERACTIONS WITH EITHER HALF-WIT > WHILE I WAS WAITING, > >it now seems to me that I am simply looking at the state of the two >half-wit system as it existed at the time I created the two half-wits. >I don't see the problem. As far as I can tell there is no need for FTL >information transmission here at all. > > What am I missing? You're missing a major part of the experiment. If this were all that is going on, there would be no problem. The following analogy captures the essence of the situation, leaving out some complications which are irrelevant. Suppose I have lots of little boxes. Each box has three compartments -- one red, one green, and one blue. I take these boxes in pairs, and in each compartment, I either put a marble, or don't. If I put a marble in the red compartment of one of the pairs, I never put a marble in the red compartment of the other one, and likewise for the blue and green compartments. (For simplicity, I will assume that the marble I put in any compartment has the same color as the compartment.) Now, for each pair of boxes, you may choose one compartment in each to open, and see if there is a marble there. Having made this choice, you can *never* look at the other compartments. If you choose the same color compartment in each box, you will always find a marble in one of the boxes, and no marble in the other. Suppose you choose to examine the red compartment in one box, and the blue compartment in the other. If I were putting the marbles in randomly, you would expect to find a marble in each a quarter of the time, no marbles a quarter of the time, and exactly one marble half the time (a quarter each in the red compartment and the blue compartment). If I were always putting the red and blue marbles in the same box, you would expect to always find one marble -- half the time, and half the time blue. If I were always putting them in different boxes, you would always either two marbles, or none -- again, each is equally likely. As it turns out, the actual distribution is none of these -- you find exactly one marble 5 times out of 6. The conclusion is that I am putting the red and blue marbles in the same box 5 times out of six, and in different boxes 1 time out of 6. The exact same distribution is found if you choose to examine the red and green compartments. The same conclusion follows. Now, what can you expect if you choose to examine the blue and green compartments? Well, at one extreme, the cases where the red and blue marbles are in different boxes could be exactly the cases where the red and green marbles are in different boxes; each of these does happen 1/6 of the time. In this case, you would always find only one of the green and blue marbles. At the other extreme, the cases where the red and blue marbles are in different boxes could be entirely disjoint from the cases where the red and green marbles are in different boxes. In this case, 1/6 of the time the blue marble is alone, 1/6 of the time the green marble is alone, leaving 2/3 of the time that all three are together. Thus, ignoring the red one, one would expect to find exactly one of the blue and green marbles 2/3 of the time, and both or neither each 1/6 of the time. Other distributions of the three marbles will give chances between 2/3 and 1 that you will find exactly one marble; but there is no way that this will happen less than 2/3 of the time. But when you try it, you find exactly one marble only half the time! The conclusion is that I am *not* putting the marbles in before you decide which choices to make, but am somehow cheating, and putting the marbles in the second box you look at only *after* you look at the first box. Returning to the EPR experiment, the analogous conclusion would be that a signal must travel from the first box examined to the second one, before that one is examined. If the experiment is designed carefully, this will require faster-than-light communication. Most physicists prefer to say that the marbles aren't really in either box until the observation; there is no faster than light communication; there is just the observation. -- Frank Adams ihnp4!philabs!pwa-b!mmintl!franka Ashton-Tate 52 Oakland Ave North E. Hartford, CT 06108 -- Biep. (biep@cs.vu.nl via mcvax) Never define a word before you know its meaning
walton@tybalt.caltech.edu.UUCP (06/19/87)
I'd just like to add one comment to Biep's posting: while current
Aspect-ish experiments verify the predictions of standard QM, thus
showing there are no hidden variables, these experiments don't detect
all (or even a very large fraction) of the "somethings" emitted from
the source. Thus, it is still possible to argue that the somethings
which are detected are systematically different from the ones which aren't.
As always, we need better equipment.
Steve Walton, guest as walton@tybalt.caltech.edu
AMETEK Computer Research Division, ametek!walton@csvax.caltech.edu
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