# Tag Info

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### Why were 20th Century German scientists so impressive?

The general question is difficult to answer. Why were the British and Dutch scientists of 17-th century so impressive? Why was French science of the 18-th and 19-th century so impressive, especially ...
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### What was different about Planck's quantization of light compared to Einstein's?

Unlike Einstein, Planck did not quantize electromagnetic waves themselves, only the exchanged energies, and even them only statistically. So the other two questions have no satisfactory answer because ...
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### Why do many names of technical and scientific subjects end with "ics"?

It is not random. These names are of Greek origin, and -ic or -ics are Anglicizations of the Greek suffix -ikos, which meant "pertaining to". In other languages it can be rendered as -ika or -ica, ...
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### How did Planck derive the black body radiation formula without using the Bose statistics?

Bose derived the black body radiation formula in early 1924 by considering the ideal gas of light quanta. Nothing could be further from Planck's mind in 1900. The idea of light quanta did not appear ...
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### How did group theory enter quantum mechanics?

From Pais's book Inward Bound, chapter 13: Wigner had become interested in $n>2$ identical particle problem. He rapidly mastered the case $n=3$ (without spin). His methods were rather laborious; ...
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### What equation is Stephen Hawking most noted for?

One can only speculate what Hawking will be remembered for, but according to NYT in 2002 he apparently expressed a wish to have what he saw as his biggest accomplishment engraved on his tombstone (...
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### What did Schroedinger try to say with the cat thought experiment?

One can simply read what Schroedinger said, English translation of his paper The Present Situation in Quantum Mechanics (1935) by Trimmer is available on Jstor. The cat paradox is presented as part of ...
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### Why did Einstein help in the development of the Quantum theory if he didn't agree with it?

Einstein made a number of contributions of momentous importance to quantum theory in the 'early days'. In 1905, his famous annus mirabilis, he published a paper on the photo-electric effect that laid ...
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### Which physicist is this quote attributed to?

Max Planck, Scientific Autobiography and Other Papers (Westport, CT: Greenwood, 1949), pp. 33-34:A new scientific truth does not triumph by convincing its opponents and making them see the light, but ...
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### Why did Einstein oppose quantum uncertainity?

I am not sure what "explain it like a story" means, but the Bohr–Einstein debates is perhaps the most dramatic story of Einstein making his dissatisfaction known. Pais's scientific biography ...
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### Did light bulb companies commission Planck to study black body radiation?

Sounds like we're all on the same page. But FWIW: In all my research for that Planck book (2015), I found no evidence that he was commissioned, contracted or paid by light bulb (or similar) companies ...
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### Why isn't Feynman's path integral taught more widely and earlier in today's academic physics curricula?

I do not agree with the statement, that the lack of mathematical rigor is a major reason for not teaching the path integral formalism in quantum mechanics. The common physicist is normally not ...
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### Why did Einstein help in the development of the Quantum theory if he didn't agree with it?

It's not true that Einstein rejected quantum mechanics completely. He acknowledged that it gave numerically accurate predictions in a wide variety of cases, as did any competent physicist by 1935. In ...
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### What theories preceded the wave, particles and duality models of light?

The wave and the particle (or corpuscular) theories of light go back to the 17-th century and are often associated with Huygens and Newton, respectively, as their founders. What preceeded them was ...
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### How did quantum mechanics operators come into being?

It is a good question, how such a weird theory could be invented:-) In its present form the theory was developed by Dirac (physicist) and von Neumann (mathematician). von Neumann essentially ...
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### Was Dirac really trying to take the square root of the Klein-Gordon operator?

One routinely speaks of the Dirac operator as a square root of the Laplacian (or Dalembertian as the case may be), and Dirac himself rather supports this heuristic in his Recollections of an exciting ...
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### Who coined the term ''Born's rule''?

I wonder why the insistence on the (English) word rule, especially as German wikipedia translates / redirects it to interpretation. Isn’t it enough for your purposes to see it stated, named and ...
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### What actually led Feynman to the path integral formulation of quantum mechanics?

It was Dirac's paper The Lagrangian in Quantum Mechanics. He gave more than just a remark about $\exp{iS/\hbar}$, he described the general structure of the path integral expression for the transition ...
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### Why didn't the phase space formulation of Quantum Mechanics get the upper hand?

This is what they call a "good question", as the expression goes. I and my collaborators had it in the mid 1990s, and about a 3rd of the audience in my colloquia ask it to themselves and me, ...
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### Were there serious attempts to model the photoelectric effect classically?

"Serious" in the OP sense is probably too high a bar. In 1900-s the situation was very much in flux as to what classical physics could and could not explain. Even Planck's and Einstein's ...
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### Why were 20th Century German scientists so impressive?

Given the historical circumstances the German education system might or might not have played a significant role in the formation of these scientists. In his collection of essays entitled "Brocas ...
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### How did gyromagnetic ratio come up before quantum mechanics, and who introduced it?

This is a very good question, I wish it got more attention. My answer will only be partial for I had difficulty finding early details on gyromagnetic effect and ratio. The concept comes up every time ...
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### What is the original source for Einstein's description of entanglement as "Spooky Action at a Distance"?

Einstein was bothered by "action at a distance" long before the 1935 EPR paper, and it was not specific to entanglement. In his debates with Bohr at the 1927 Solvay congress he used the single slit ...
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### How did Stern or Gerlach, of Stern-Gerlach experiment, create individual silver atoms? How were they accelerated?

Atomic spectroscopy was very advanced 100 years ago (1920s) and we must appreciate their intelligence. If a metal like silver is being heated to the extent of boiling in high vacuum, all you get is ...
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### How did Planck calculate the Planck constant?

See How did Planck derive the black body radiation formula without using the Bose statistics? for general circumstances of Planck's discovery. Specifically, Planck was trying to reproduce the ...
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### Who was the first to say "Shut up and calculate!"?

Some centuries before Mermin, Leibniz in the 17th century was seeking a solution to some of the denominational quarrels that were plaguing his generation by envisioning a calculus ratiocinator that ...
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### Who was the first to say "Shut up and calculate!"?

Mermin has a thorough analysis[1] and traces the phrase to himself in a 1989 Physics Today column [2] & makes a strong case that the numerous attributions to Feynman are mistaken. [1] Could ...
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### Origin of operators in quantum mechanics

From where did the concept of operator in quantum mechanics came, historically? This was a gradual development started by Heisenberg's insight. He invented (infinite) matrices (without any prior ...
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