“…a detailed mathematical discussion shows that whatever kind of wave-packet we select to represent the electron, the product of the two uncertainties of position and momentum can never be less than h, which is precisely what Heisenberg found…”

— James Jeans

Physics and Philosophy (1942)

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James Jeans 54

British mathematician and astronomer 1877–1946

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“Now, a symbol is not, properly speaking, either true or false; it is, rather, something more or less well selected to stand for the reality it represents, and pictures that reality in a more or less precise, or a more or less detailed manner.”

Pierre Duhem (1861–1916) French physicist, historian of science

[U]n symbole n'est, à proprement parler, ni vrai, ni faux; il est plus ou moins bien choisi pour signifier la réalité qu'il représente, il la figure d'une manière plus ou moins précise, plus ou moins détaillée...
[Pierre Maurice Marie Duhem, translated by Philip P. Wiener, The Aim and Structure of Physical Theory, Princeton University Press, 1991, 069102524X, 168]
Notice sur les Titres et Travaux scientifiques de Pierre Duhem rédigée par lui-même lors de sa candidature à l'Académie des sciences (mai 1913), The Aim and Structure of Physical Theory (1906)

“Heisenberg’s starting point was the philosophical judgment, that a physical theory should not concern itself with things like electron orbits in atoms that can never be observed. This is a risky assumption, but in this case it served Heisenberg well.”

Steven Weinberg (1933) American theoretical physicist

Source: Lectures on Quantum Mechanics (2012, 2nd ed. 2015), Ch. 1: Historical Introduction

“The quantum world is a world of waves, not particles. So we have to think of electron waves and proton waves and so on. Matter is 'incoherent' when all its waves have a different wavelength, implying a different momentum. On the other hand, if you take a pure quantum system – the electrons in a superconducting magnet, or the atoms in a laser – they are all in phase with one another, and they demonstrate the wave nature of matter on a large scale. Then you can see quite visibly what matter is down at its heart.”

Carver Mead (1934) American computer scientist

"An Interview with Carver Mead", American Spectator, Sep/Oct2001, Vol. 34 Issue 7, p68.

“The main result reached by the new theory was that the classical mechanics can be made to account for the whole range of spectral phenomena, provided entirely new meanings are given to such symbols as p and q which had hitherto been taken to describe the position and motion of the electron…. The most significant of the new properties is that the product pq is no longer the same as the product qp - in other words the order in which the two factors are multiplied together is no longer a matter of indifference. The difference between pq and qp is found to be always the same, being Planck's constant h multiplied by a numerical multiplier.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“The more precise the measurement of position, the more imprecise the measurement of momentum, and vice versa.”

Werner Heisenberg Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik

Initial statement of the Uncertainty principle in "Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik" in Zeitschrift für Physik, 43 (1927)
Variant translation: The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa.
As quoted in "The Uncertainty Principle" at the American Institute of Physics http://www.aip.org/history/heisenberg/p08.htm

“Nothing is less real than realism. Details are confusing. It is only by selection, by elimination, by emphasis, that we get at the real meaning of things.”

Georgia O'Keeffe (1887–1986) American artist

“The words "position" and "velocity" of an electron… seemed perfectly well defined… and in fact they were clearly defined concepts within the mathematical framework of Newtonian mechanics. But actually they were not well defined, as seen from the relations of uncertainty.”

Werner Heisenberg (1901–1976) German theoretical physicist

Physics and Philosophy (1958)
Context: The words "position" and "velocity" of an electron... seemed perfectly well defined... and in fact they were clearly defined concepts within the mathematical framework of Newtonian mechanics. But actually they were not well defined, as seen from the relations of uncertainty. One may say that regarding their position in Newtonian mechanics they were well defined, but in their relation to nature, they were not. This shows that we can never know beforehand which limitations will be put on the applicability of certain concepts by the extension of our knowledge into the remote parts of nature, into which we can only penetrate with the most elaborate tools. Therefore, in the process of penetration we are bound sometimes to use our concepts in a way which is not justified and which carries no meaning. Insistence on the postulate of complete logical clarification would make science impossible. We are reminded... of the old wisdom that one who insists on never uttering an error must remain silent.

“It would, however, be wrong to think of an electron as a bullet-like structure with tentacles sticking out from its surface. We can calculate the mass of the bullet, and also the mass of the tentacles. The two masses are found to be identical, each agreeing with the known mass of the electron. Thus we cannot take the electron to be bullet plus tentacles… The two pictures do not depict two different parts of the electron, but two different aspects of the electron. They are not additive but alternative; as one comes into play, the other must disappear.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“In the interior of the atom, Bohr had tried the plan of retaining the particle-electron and modifying the classical mechanics. Heisenberg took the opposite course, his procedure amounting in effect to retaining the classical mechanics, at least in form, and modifying the electron. Actually, the electron dropped out all together, because it exists only as a matter of inference and not of direct observation. For the same reason, the new theory contains no mention of atoms, nuclei, protons, or of electricity in any shape or form. The existences of all these are matters of inference, and Heisenberg's purely mathematical theory could no more make contact with them than with the efficiency of a turbine or with the price of wheat.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“… mediocre people find their way into positions of authority… because when it comes to even the most important positions, our selection decisions are a good deal less rational than we think.”

Malcolm Gladwell book Blink

Source: Blink: The Power of Thinking Without Thinking

“…a detailed mathematical discussion shows that whatever kind of wave-packet we select to represent the electron, the product of the two uncertainties of position and momentum can never be less than h, which is precisely what Heisenberg found…”

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