ABRAHAM PAIS:
I have known a number of real important man. Bohr, Einstein I have known. Compare Niels Bohr with Mozart, and Einstein with God. It was a great privilige to live together with those people.

TITEL: Pais, Einstein, Bohr

ABRAHAM PAIS:
The debate between Einstein and Bohr was about Quantum mechanics, about the basics of quantum mechanics. It was a debate about the principles of the theory and I shall try to explain the most important point with the aim of a simple example. The simplest example what I can think about is of a particle that moves in a field of force that at a certain moment is here and moves with this speed. The classic theory says, from before the quantumtheory, says that if I know where the particle is at this place with this speed than I can tell at a later date that the particle is there and goes with that speed. That tells the classic theory. The quantum theory tells us that that is impossible. Because, tells the quantumtheory, the premisses are wrong. You can not, tells the quantum theory, you can not say of a particle that is exactly, at a certain moment at certain position with a certain speed. Technically this is expressed by the uncertainty relations, formulated by Heisenberg and futher developed by Bohr etc. The idea of non casuality in classical sense was something that Einstein never wanted to accept. In the beginning he asserted that the quantum theory wrong was. He tried to give counter examples. Those were all disapproved by Bohr.

COMMENTATOR:
How went the dialoque? Were they ever angry against each other?

PAIS:
Never angry. It was always friendly, but heat it. Both passions went up in their work. I mean, a good phsicist is a passionate man. That it is all cool, please do not believe a word about that. Passion is part of this.

COMMENTATOR:
Who attacked and who defended?

PAIS:
I mean, attack and defend, it was a dialoque, it went both ways. Einstein came with a counter example. Bohr went home, full with unrest en the next morning he came back and said: " "Einstein, you are wrong, wrong. It works. The uncertainty principle proves that it is not possible. And that continued for a number of years. It started in 1925, 1926 en it went through until 1930, 1931 and after that gave Einstein up with saying that the quantum theory was wrong. And after that he said: "The En daarna zei hij: "The quantumtheory is not wrong, he is even - as he later said - the quantumtheory is the best theory which is discovered in the twentieth century. He said so. But, he said, the theory is incomplete. There is a lowerlayer, below the quantum theory lies a secret theory which is currently not yet known. And that is the theory in which the causality is again repaired. That was, rougly described, the difference in opinion between those two.

Do you understand why such a genius physicist like Einstein never became a real supporter of the quantumtheory?

PAIS:
I have often thought about that and really I have never fully understood that. Einstein was a man with highly gifted liberties also in his scientific creativity. But in the case of the quantum theory he had a rigidity that did not fit with the rest of his existance. I have thought a lot about this and I can not give a good answer. I do not know. Simple, I do not know.

COMMENTATOR:
Do you held it for possible that over approximate a century, one will decide that Einstein was on the right track and that the quantum theory was not finished?

PAIS:
I have seen a lot in physics to say that someone has the last word in a part of science. On the other side I am convinced that at this moment the point of view of Bohr the only tenable is. There are modern experiments performed to try to show that alternatives of quantum mechanics maybe were beter as quantum mechanics. Those are very good experiments, which I fully respect, and those did show that that is not the case, quantum mechanics is still the winning theory.
This is not a completely satisfying answer, but believe me there is no better answer.

The above side contains a full CD with the interview
For the complete text of this transcript (in dutch) See: http://www.vpro.nl/attachment.db/transcript.htm?5206873
Usenet Discussion http://groups.google.com/groups?hl=en&lr=&scoring=d&q=%22Nicolaas+Vroom%22%2C+Pais

16 february 2002

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