What is the context of observation in this video?

[Ken G]

Ken G; You missed it. The shoes do not get split at the ***start*** they get split ***during*** their travel.

I see no difference. You shake the cargo bay of an airplane **during** travel and some shoes fall out. Bell's theorem is much more subtle than the example you gave (it requires the qubit concept, not just any old rule for making widely separated lights go on in a correlated way).

 

[kaonyx]

The example I gave my friend was originally published in NewScientist magazine as exactly the way that Bell's theorem challenges common sense. If you like I can find the back issue for you to read.

 

[Ken G]

No what you said is certainly not how Bell's theorem challenges common sense. This is what you said:

Suppose that only after comparing these data sets side by side, over lunch, the physicists discover that there seems to be a rule operating between the labs.
It doesn't actually matter what the rule is, but let's make one up...

So no, it certainly does matte what the rule is. It has to be a rule of a very special kind, a correlation that is impossible in the "matching shoes" sense. It has to be a correlation that only comes up in wave mechanics, and only when noncommuting observations are done. It's very subtle indeed, and if New Scientist doesn't know that, at least we should.

 

[kaonyx]

It is very simple. A formula carried by a particle (eg. programmed into it is some way) (or that carries some kind of knowledge of its history) is an example of "hidden local variables".
One prediction of Quantum Mechanics is that the results between the two labs can be correlated (or anti-correlated - its much the same idea) in various surprising ways. (No the details don't matter here - if you really want you can look them up).

Bell's theorem states simply that there DO exist correlations that you can detect that CANNOT be explained by hidden local variables. These correlations are simple things, as I explained. They are not high tech magical things - and yes they can be reduced down to such mundane events as the colours of twinkling lights.

If a particle was programmed like a spreadsheet cell formula for example, then we can find simple correlations between the results of two labs that that could not be explained by any kind of formula or information or rule carried by each particle alone.
Even if we knew the formulas or rules or knowledge carried by both particles, it would not be enough.
So you see that not only is Bell's theorem extremely simple, it is extremely powerful in limiting what is knowable.

And incidentally Einstein relativity tells us that there is no "global spreadsheet in the sky" either, because that would require a preferred frame of reference or faster than light transfer of information. This latter idea might seem like an out, but actually it creates even worse paradoxes.

The relevance to observation here is of course that the experimenter, in the act of choosing where and when to determine the properties of one particle, has "acted without acting" in determining the properties of its twin.

 

[Ken G]

Yes, I can now agree with these corrected statements about Bell's result, except the last two sentences, which I can't judge because I don't know what they are saying. I would not say that any experimenter is determining the properties of the twin particles, as "determining" is often used to mean "influences" or "causes". I would say that the experimenter is gaining information about one particle by looking at the other. The nature of that information has surprising nonlocal characteristics (it isn't carried by the particle), but gaining information about one thing by looking at something else that has been coupled to it is not by itself anything so surprising.

 

[kaonyx]

You don't think so?

 

[ATOMS13]

How exactly do we exert energy on an electron by looking at it?

To observe an electron we have to use a microscope.. By using this microscope we exert energy..this energy, electrons, interact with what we are observing and there by "change" it