April 22nd, 2012

Apollo 4 on column of fire

The point of all this

Before I attempt to sleep I want to get some clarifications of http://chemoelectric.livejournal.com/1026770.html out there. It is hard to follow the arguments Bell is making in part because, in a way, they are too stupid to believe someone would make them.

Physicists stipulate that the electrons or photons in the EPR experiment have correlated properties due to being produced at the same time and place in the same particle source, and so the interactions of these particles with physically separated detectors also are correlated. This is not in dispute. What is in dispute is whether it is possible, at least in principle, to come up with a more fundamental theory than quantum mechanics, in which all the effects are propagated in the normal, intuitive way, at speeds less than or equal to the speed of light. (This is, after all, a problem about the propagation of light!)

Bell’s argument proceeds more or less as follows: (1) The correlated particles reach the detectors, where they proceed to cause correlated detector results. (2) In classical physics, Detector A is distant from Detector B and therefore has no effect on it; likewise Detector B is distant from Detector A and can have no effect on it. (3) Therefore the readings at Detector A and Detector B are ‘independent’ and we can write P(AB|background conditions) = P(A|background conditions)P(B|background conditions). (4) From this we can deduce certain mathematical expressions that are violated by actual experiments, which instead show exactly the correlations stipulated in step (1). (5) Therefore (2) is wrong, and indeed Detector A does affect Detector B, in an exact instant, across any distance whatsoever; and vice versa, in a special, quantum mechanical way. This is ‘quantum non-locality’. Furthermore it is impossible to explain the correlations as effects propagated at or below light speed, and you shouldn’t even try to do so; to do so would be like trying to make a perpetual motion machine or square the circle.

What is actually wrong, however, is step (3), which is nothing but a formal expression of one of those logical fallacies you can find catalogued on websites such as Wikipedia and Nizkor.
Apollo 4 on column of fire

Motivation for the argument that quantum mechanics _does_ involve "spooky action at a distance"

Why are scientists so desperate, in the first place, to show that quantum mechanics involves what I think Einstein-Podolsky-Rosen called ‘spooky action at a distance’? A hint comes from one of my college physics professors, the best damn teacher I ever had, but despite being a good teacher he had a fondness for using QM to say ‘Nyeah! Nyeah!’ to Albert Einstein. The mythical Einstein is an Olympian figure, whom I imagine a lot of people would like to defeat in mental battle. (The actual Einstein was an above average theoretical physicist who had gone to a public engineering school. You’d probably never hear of him, if he tried to break into the field now.)

Another possible factor is that quantum mechanics historically developed in a suck-up atmosphere of leader and bootlicking minions, and the suck-up cultural aspect remained, except, as with the Church, the great leader became replaced by an institutional orthodoxy.

Another factor may be that Einstein himself primed people into believing ‘anything goes’ in physics. This is a complex subject, for which I refer to (the difficult and also pop-up ad laden site) http://nonloco-physics.0catch.com/
Apollo 4 on column of fire

Fun with reading

I’m re-reading Kracklauer Elder and Younger’s paper on the Twin Paradox at http://nonloco-physics.0catch.com/ and came across this lovely sentence:

A moment’s reflection convinces one that as a result of this alternate
Ansatz, ‘simultaneous’ events in any frame must be those on a worldline parallel to the pure space-like axis.

I had to draw a picture in my head, in that non-euclidean Minkowski geometry, to realize this was saying simply that time and simultaneity work exactly the way we commonly imagine them to work. :) (Actually the non-euclideanness is irrelevant in this case.)
Apollo 4 on column of fire

As I said, catalogued at Nizkor

Bell’s error in writing P(AB) = P(A)P(B): http://www.nizkor.org/features/fallacies/ignoring-a-common-cause.html

Actually his error is the contrapositive of this (‘A cannot cause B, therefore A and B are not connected’).

When someone commits one of these catalogued errors, in a way it is not a big deal; they are catalogued because they are so common. Many of them are a challenge to avoid. More interesting, I think, is the psychology behind the whole scandal. To quote ET Jaynes in ‘Clearing up mysteries::

[S]omehow, many physicists became persuaded that the success of the QM mathematical formalism proved the correctness of Bohr's private philosophy, even though hardly any { even among his disciples { understood what that philosophy was. All the attempts of Einstein, Schrödinger, and others to point out the patent illogic of this were rejected and sneered at; it is a worthy project for future psychologists to explain why.
In part it may be that Bohr was some kind of modernist:

Since today some think that merely to verify the correlations experimentally is to refute the
EPR argument, let us stress that EPR did not question the existence of the correlations, which are
to be expected in a classical theory. Indeed, were the correlations absent, their argument against the
QM formalism would have failed. Their complaint was that, with physical causation unavailable,
only instantaneous psychokinesis (the experimenter's free{will decision which experiment to do) is
left to control distant events, the forcing of S2 into an eigenstate of either q2 or p2. Einstein called
this ‘a spooky kind of action at a distance’.

To understand this, we must keep in mind that Einstein's thinking is always on the ontological
level; the purpose of the EPR argument was to show that the QM state vector cannot be a
representation of the ‘real physical situation’ of a system. Bohr had never claimed that it was,
although his strange way of expressing himself often led others to think that he was claiming this.
From his reply to EPR, we nd that Bohr’s position was like this: ‘You may decide, of your
own free will, which experiment to do. If you do experiment E1 you will get result R1. If you
do E2 you will get R2. Since it is fundamentally impossible to do both on the same system, and
the present theory correctly predicts the results of either, how can you say that the theory is
incomplete? What more can one ask of a theory?’

While it is easy to understand and agree with this on the epistemological level, the answer that
I and many others would give is that we expect a physical theory to do more than merely predict
experimental results in the manner of an empirical equation; we want to come down to Einstein's
ontological level and understand what is happening when an atom emits light, when a spin enters a
Stern-Gerlach magnet, etc. The Copenhagen theory, having no answer to any question of the form:
‘What is really happening when - - - ?’, forbids us to ask such questions and tries to persuade
us that it is philosophically naïve to want to know what is happening. But I do want to know,
and I do not think this is naïve; and so for me QM is not a physical theory at all, only an empty
mathematical shell in which a future theory may, perhaps, be built.

My own attitude is indeed that a scientific ‘theory’ is not actually a theory unless it has the ontological character. A purely epistemological ‘theory’ is not a theory; it is a phenomenological law, a kind of pre-Newtonian regression. It is Kepler’s elliptical orbits, without comprehension of why and how planets move in elliptical orbits around the sun. A theory, on the other hand, gives you a kind of metaphorical picture of how the world works; if for no other reason, it is necessary for science to do this to satisfy the same deeply human urges that used to explain day, night, rain, and drought as the activities of divine beings. But we could always let religions continue to fill that gap, even if they do a halfass job of it. Perhaps more important is that a purely epistemological theory is a dead end for future scientific development; the human brain simply cannot function most efficiently unless it can picture what it is thinking about.