Last modified on 13 May 2014, at 19:50

John Stewart Bell

John Stewart Bell, 1988

John Stewart Bell (June 28 1928October 10 1990) was an Irish physicist who worked in the field of particle physics at CERN, and who developed one of the most important theorems of quantum physics, Bell's Theorem.

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  • Theoretical physicists live in a classical world, looking out into a quantum-mechanical world. The latter we describe only subjectively, in terms of procedures and results in our classical domain.
    • "Introduction to the hidden-variable question" (1971), included in Speakable and Unspeakable in Quantum Mechanics (1987), p. 29
  • The concept of 'measurement' becomes so fuzzy on reflection that it is quite surprising to have it appearing in physical theory at the most fundamental level... does not any analysis of measurement require concepts more fundamental than measurement? And should not the fundamental theory be about these more fundamental concepts?
  • A final moral concerns terminology. Why did such serious people take so seriously axioms which now seem so arbitrary? I suspect that they were misled by the pernicious misuse of the word ‘measurement’ in contemporary theory. This word very strongly suggests the ascertaining of some preexisting property of some thing, any instrument involved playing a purely passive role. Quantum experiments are just not like that, as we learned especially from Bohr. The results have to be regarded as the joint product of ‘system’ and ‘apparatus,’ the complete experimental set-up.
    • "On the impossible pilot wave" (1982), included in Speakable and Unspeakable in Quantum Mechanics (1987), p. 166
  • I am a Quantum Engineer, but on Sundays I Have Principles.
    • Opening sentence of his "underground colloquium" in March 1983, as quoted by Nicolas Gisin in an edition by J. S. Bell, Reinhold A. Bertlmann, Anton Zeilinger (2002). Quantum [un]speakables: from Bell to quantum information. Springer. p. 199. ISBN 3540427562. 
  • While the founding fathers agonized over the question 'particle' or 'wave', de Broglie in 1925 proposed the obvious answer 'particle' and 'wave'. Is it not clear from the smallness of the scintillation on the screen that we have to do with a particle? And is it not clear, from the diffraction and interference patterns, that the motion of the particle is directed by a wave? De Broglie showed in detail how the motion of a particle, passing through just one of two holes in screen, could be influenced by waves propagating through both holes. And so influenced that the particle does not go where the waves cancel out, but is attracted to where they cooperate. This idea seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored.
    • "Six Possible Worlds of Quantum Mechanics" (1986), included in Speakable and Unspeakable in Quantum Mechanics (1987), p. 191
  • Is it not good to know what follows from what, even if it is not necessarily FAPP? [FAPP is Bell's suggested abbreviation of "for all practical purposes."] Suppose for example that quantum mechanics were found to resist precise formulation. Suppose that when formulation beyond FAPP was attempted, we find an unmovable finger obstinately pointing outside the subject, to the mind of the observor, to the Hindu scriptures, to God, or even only Gravitation? Would that not be very, very interesting?
    • Quoted in "Quantum Enigma: Physics Encounters Consciousness", by Rosenblum, B. and Fred Kuttner (2006)

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