The Einstein-Podolski-Rosen Paradox
The orthodox quantum position states that the time-function characterises the individual system exhaustively. Margenau’s defence of this does not hit the essential aspects.
Niels Bohr is an “orthodox” quantum theoretician who does justice to the problem.
This view at the matter means that the paradox forces us to relinquish one of the two assertions=
- The description by means of the Psi-function is complete
- The real states of spatially separated objects are independent of each other
On the other hand, it is possible to adhere to (2), if one regards the Psi-function as the description of a (statistical) ensemble of systems (and therefore relinquishes (1) ).
However, this view blasts the framework of the “orthodox quantum theory.”
Margenau correctly says that quantum mechanics on the classical level it corresponds to ordinary dynamics.
If our concern is with macroscopic masses (billiard balls or stars), we are operating with very short de Broglie-waves, which are determinative for the behaviour of the center of gravity of such masses.
This why it is possible to arrange the quantum-theoretical description for a reasonable time in such a manner that for the macroscopic way of viewing things, it becomes sufficiently precise in position as well as in momentum.
It is true also that this sharpness remains for a long time and that the quasi-points thus represented behave just like the mass-points of classical mechanics. However, the theory shows also that, after a sufficiently long time, the point-like character of the Psi-function is completely lost to the center of gravity-co-ordinates, so that one can no longer speak of any quasi-localisation of the centers of gravity.
The picture then becomes, for example in the case of a single macro-mass-point, quite similar to that involved in a single free electron.
If now, in accordance with the orthodox position, I view the Psi-function as the complete description of a real matter of fact for the individual case, I cannot but consider the essentially unlimited lack of sharpness of the position of the (macroscopic) body as real.
On the other hand, however, we know that, by illuminating the body by means of a lantern at rest against the system of co-ordinates, we get a (macroscopically judged) sharp determination of position. In order to comprehend this I must assume that that sharply defined position is determined not merely by the real situation of the observed body, but also by the act of illumination.
This is again a paradox (similar to the mark on the paper strip in the above mentioned example). The spook disappears only if one relinquishes the orthodox standpoint, according to which the Psi-function is accepted as a complete description of the single system.
It may appear as if all such considerations were just superfluous learned hairsplitting, which have nothing to do with physics proper. However, it depends precisely upon such considerations in which direction one believes one must look for the future conceptual basis of physics.
I close these expositions, which have grown rather lengthy, concerning the interpretation of quantum theory with the reproduction of a brief conversation which I had with an important theoretical physicist. He= “I am inclined to believe in telepathy.” I= “This has probably more to do with physics than with psychology.” He= “Yes.”
The essays by Lenzen and Northrop both aim to treat my occasional utterances of epistemological content systematically.
From those utterances Lenzen constructs a synoptic total picture, in which what is missing in the utterances is carefully and with delicacy of feeling supplied.
Everything said therein appears to me convincing and correct.
Northrop uses these utterances as point of departure for a comparative critique of the major epistemological systems. I see in this critique a masterpiece of unbiased thinking and concise discussion, which nowhere permits itself to be diverted from the essential.
The reciprocal relationship of epistemology and science is of noteworthy kind. They are dependent upon each other.
Epistemology without contact with science becomes an empty scheme. Science without epistemology is — insofar as it is thinkable at all — primitive and muddled. However, no sooner has the epistemologist, who is seeking a clear system, fought his way through to such a system, than he is inclined to interpret the thought-content of science in the sense of his system and to reject whatever does not fit into his system.
The scientist, however, cannot afford to carry his striving for epistemological systematic that far. He accepts gratefully the epistemological conceptual analysis. But the external conditions set by the facts of experience, do not permit him to restrict himself too much in the construction of his conceptual world by the adherence to an epistemological system.
To the systematic epistemologist, the scientist would appear as a kind of unscrupulous opportunist.
The scientist would appear as=
- a realist insofar as he seeks to describe a world independent of perception
- an idealist insofar as he looks upon theories as the free inventions of the human spirit not logically derivable from what is empirically given
- a positivist insofar as he considers his theories justified only to the extent to which they furnish a logical representation of relations among sensory experiences
- a Platonist or Pythagorean insofar as he considers the viewpoint of logical simplicity as an indispensable and effective tool of his research
All of this are in Lenzen’s and Northrop’s essays.
E. A. Milne, G. Lemaitre, and L. Infeld mentions the cosmological problem.
Milne’s ingenious reflections have a theoretical basis that is too narrow. I believe it is impossible to get reliable theoretial results in the field of cosmology without general relativity.