Talk:Uncertainty principle

Observer Effect

Is the quoted statement correct? Didn't the modern double-slit experiment, conducted sometime after the sited reference, reveal that it was not simply detecting the particle that collapsed the wave function but rather the observation of the result? Please help!

"It must be emphasized that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer." — Preceding unsigned comment added by 2a02:c7d:784d:5500:2c4b:22cc:fce5:28c0 (talk)

The ideal of the detached observer -iatrogenic Building Blocks

Hello there. In the section entitled 'The ideal of the detached observer', though Pauli mentions that he disagrees with Einstein's refutation of the uncertainty principle with respect to the observer influencing the thing observed, adding that he hopes his memory accurately reported their conversation, we do not hear Pauli's corrective to Einstein's attempt to refute the idea of something changing while/upon being observed. I'm sure his recall was perfectly good and it probably doesn't matter as the example cited, the position of the moon being unchanged whether we observe it or not (a bit like Bishop Berkeley's kitchen vanishing once he moves into the living room) is exactly (with all due respect to Einstein) the wrong scenario with which to test the hypothesis. A simpler scenario whereby an inspector is observing a junior teacher teach captures the theory a little more firmly. The inspector's presence distorts the lesson being given though s/he perhaps is unaware to what extent his presence changes the thing that he is observing. Descartes x/y axis assumes a new dimension Z, 'the catalytic observer' or perhaps better 'the subjective correlative' (to finesse T.S. Eliot), it seems to me (though I know nothing about physics). Another scenario might see an art gallery visitor standing before a classical painting and then an abstract painting, the former demanding no participation to consummate its meaning, the latter requiring some. (Unwelcome to settled tastes, the idea of the public participating in art is anti-elitist but nonetheless considered a necessary corrective to self serving elites.) Likewise, developments like Le Nouveau Roman require readers to augment their missing chapters to complete them, thereby assigning or allowing a role for the reader/observer (as Detective fiction does). These simple examples are part of an index of much heavier (complex) applications with respect to the manner in which our judgement is or becomes skewed in certain situations where we passively participate in let's say condemning lust while living a life of unwelcome and enforced celibacy. Our often failure to see that our own pathology (sorry) influences our view of the thing observed can get us into all kinds of trouble. Psychoanalysts have something called the object oriented question which is 'employed' on particularly resistant/ repressed individuals who will only surrender an image of their ego unwillingly and so such people speak through objects (as we all invariably do) to express themselves, so enabling the therapist to get an idea of their psychic composition. The therapist him or herself may possess all kinds of blocks to observing the patient in a clear light. These iatrogenic blocks provide a term which may help differentiate between Einstein's Moon and more subtle examples where the presence of the observer does impact the thing observed. So, I think this section needs a little finessing to either include Pauli's refutation or a better example might be found to expound the actual beneficial application whereby a scenario is altered by virtue of being a participant. I hope I haven't confused matters. Thank you. M.H. p.s. If you doubt the role of the observer, consider the oft told story of King Faisal waking disguised in the market to find out what his people were thinking, and saying. He knew that if he showed up as himself, he'd get a very different reception. 'The Deferential Equation', maybe. — Preceding unsigned comment added by 37.125.41.223 (talk)

Is the Uncertainty Principle a basic part of quantum mechanics?

The article states, "Introduced first in 1927 by the German physicist Werner Heisenberg." While that is technically true of HUP, the principle of complementary variables was discovered by Lagrange, Fourier, and others at the end of the 1700s or beginning of the 1800s, depending on whom you read. In the 1700s the heat equation and sound waves were the inspirations for discovering, among many other things, the inverse precision in the measurement of complementary variables, such as amplitude and frequency with respect to time.

I'm not sure why so many physicists have stated that Heisenberg's Uncertainty Principle (HUP) is a basic and unique part of QM. It is not any such thing. It is a red herring. It is a distraction. It is just plain wrong.

I would ask them, is the equivalent inverse precision principle due to Joseph Fourier (and others) between the amplitude and the frequency of an audio or electromagnetic signal also part of QM? Or can you physicists out there finally admit that the inverse precision of measurement of complementary variables is entirely due to the interdependence of the two variables, one of which is the derivative or the Fourier transform of the other?

The HUP is usually expressed as $\sigma _{x}\sigma _{p}\geq {\frac {\hbar }{2}}~~$. But this scales up without difficulty to the classical regime, in which complementary pairs of variables are not treated as a mystery, merely as the natural result of measurement: it takes one measurement in time to fix the position of a particle, but averaging many such measurements in time reduces the accuracy. Inversely, it requires averaging many measurements in time to measure velocity accurately, but measuring only once reduces the accuracy. It is impossible to measure position and velocity both accurately and no matter whether one or many measurements are made. The same is true of amplitude and frequency. The same is true for elementary particles as for whole planets. David Spector (talk) 16:47, 13 July 2023 (UTC)

The Uncertainty principle is certainly a basic part of QM and HUP is both basic and part of QM. There is a vast literature to support that point of view. Historically this results from the sudden and unexpected discovery that matter dynamics are governed by wave equations.

The understanding of the wave equation and the Fourier relations of course predate Heisenberg. That is why the HUP was so quickly part of QM discussions: this background was part of the education of all physicists at that time. The position-momentum relationship of course was not part of the older understanding as those wave equations did not have a position-momentum issue to be concerned with. And the specific HUP derivation could not have predated Heisenberg because the operator concepts (commutator) he used where only introduced by Schrodinger (as far as I know). Classical mechanics has Poisson brackets which Dirac eventually connected to the commutator relations.

Adding a section to this article on the Fourier relations would be great. I have not found a good reference for the connection between the earlier work and Heisenberg's work. Johnjbarton (talk) 14:38, 9 August 2023 (UTC)

History section contains original research.

The History section has two paragraphs that mention Fourier three times. The citation is to a work of Heisenberg:

Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik The English translation in 1983 (by Heisenberg?) is here: https://ntrs.nasa.gov/citations/19840008978

As far as I can tell, at no point in this article does the word "Fourier" appear. Johnjbarton (talk) 17:23, 9 August 2023 (UTC)

The excellent review by D. Sen points to Hardy's 1933 paper as the Fourier analysis.

Hardy, G. H., A theorem concerning Fourier transforms. J. London Math. Soc., 1933, 8, 227–231. Johnjbarton (talk) 18:56, 9 August 2023 (UTC)