Talk:Niels Bohr

Should we change his title from “ Theoretical Physicist” to “Theoretical and Nuclear Physicist”?

At the beginning, it says he is a Danish theoretical physicist, but he is also a nuclear physicist. He did both, but I feel that he was actually mainly a nuclear physicist, because a lot of his work was centered around the structure of atoms and such. Einstein3.1415926535! (talk) 20:46, 21 January 2025 (UTC)

The neutrino

The article refers to the neutrino as Fermi's concept. He coined the phrase "neutrino" (Italian: little neutral one) to distinguish it from the neutron, recently discovered by James Chadwick. But the idea was Pauli's. Per George Gamow in Thirty Years That Shook Physics: "Pauli, who could not be called conservative in any sense of the word, was nevertheless strongly opposed to Bohr's view [that the conservation of energy was violated in beta decay]. He preferred to assume that the balance of energy violated by the continuity of β-ray spectra was re-established by the emission of some other kinds of yet unknown particles which he called 'neutrons.' The name of this 'Pauli neutron' was later changed to 'neutrino after Chadwick's discovery of what today we call the neutron." Yes, Pauli neutron. Gamow goes on: "As the years passed, more and more evidence was accumulated in favor of Pauli's neutrinos." Again, Pauli neutrinos.

Here is the letter by Pauli outlining his prediction of the neutrino ("Dear Radioactive Ladies and Gentlemen,...") To wit: "As the bearer of these lines, to whom I graciously ask you to listen, will explain to you in more detail, because of the 'wrong' statistics of the N- and Li-6 nuclei and the continuous beta spectrum, I have hit upon a desperate remedy to save the 'exchange theorem' (1) of statistics and the law of conservation of energy. Namely, the possibility that in the nuclei there could exist electrically neutral particles, which I will call neutrons, that have spin 1/2 and obey the exclusion principle and that further differ from light quanta in that they do not travel with the velocity of light. The mass of the neutrons should be of the same order of magnitude as the electron mass and in any event not larger than 0.01 proton mass. - The continuous beta spectrum would then make sense with the assumption that in beta decay, in addition to the electron, a neutron is emitted such that the sum of the energies of neutron and electron is constant." Note that in 1930 they were called neutrons and not neutrinos, the term coined by Fermi.

Fermi did do more than just name neutrinos, however, per Gamow: "Another important work was the formulation of the mathematical theory of particle transformation, involving the emission of mysterious chargeless particles proposed earlier by Pauli."

So give credit to Fermi for coining the phrase and working out the math, but the idea of a massless (or nearly massless) neutral particle was Pauli's. Charlie Faust (talk) 23:36, 13 March 2025 (UTC)

Per Wikipedia: "In 1930, Pauli considered the problem of beta decay. In a letter of 4 December to Lise Meitner et al., beginning, "Dear radioactive ladies and gentlemen", he proposed the existence of a hitherto unobserved neutral particle with a small mass, no greater than 1% the mass of a proton, to explain the continuous spectrum of beta decay. In 1934, Enrico Fermi incorporated the particle, which he called a neutrino, 'little neutral one' in Fermi's native Italian, into his theory of beta decay. The neutrino was first confirmed experimentally in 1956 by Frederick Reines and Clyde Cowan, two and a half years before Pauli's death. On receiving the news, he replied by telegram: 'Thanks for message. Everything comes to him who knows how to wait. Pauli.'" Charlie Faust (talk) 23:39, 13 March 2025 (UTC)

And, look here: "The neutrino was postulated first by Wolfgang Pauli in 1930 to explain how beta decay could conserve energy, momentum, and angular momentum (spin). In contrast to Niels Bohr, who proposed a statistical version of the conservation laws to explain the observed continuous energy spectra in beta decay, Pauli hypothesized an undetected particle that he called a 'neutron', using the same -on ending employed for naming both the proton and the electron. He considered that the new particle was emitted from the nucleus together with the electron or beta particle in the process of beta decay and had a mass similar to the electron." (Emphasis added.)

As a great man said, "Everything comes to him who knows how to wait." Charlie Faust (talk) 23:47, 13 March 2025 (UTC)

My apologies. I was familiar with Fermi's theory of Beta decays (having brought Fermi's article to featured). Thanks for that. (If you are looking for something to do, Pauli's article needs work.) Hawkeye7 (discuss) 00:43, 14 March 2025 (UTC)

Thank you. And yes, Pauli's article does need work; there was nothing about the neutrino in the lead until I added it.

Thank you for your work on Fermi! A great man. Charlie Faust (talk) 14:11, 14 March 2025 (UTC)

The Music of the Spheres

I added: "Einstein wrote: "That this insecure and contradictory foundation [of physics in the years from 1910 to 1920] was sufficient to enable a man of Bohr's unique instinct and tact to discover the major laws of the spectral lines and of the electron shells of the atoms together with their significance for chemistry appeared to me like a miracle—and appears to me like a miracle even today. This is the highest form of musicality in the sphere of thought."

This was removed. That's a mistake. It's an elegant tribute from one genius to another. And two geniuses with very different views of quantum theory. Einstein made that comment when he was 70, long after he was "spooked" by the developments of quantum mechanics. Even then, he appreciated the early successes of quantum theory, and the genius of Bohr. Charlie Faust (talk) 14:20, 14 March 2025 (UTC)

Maybe it doesn't belong under "Accolades". Maybe it belongs under "Bohr model", to show how it was received. But it belongs in the article. Einstein's description of Bohr's model in terms of "musicality" is apt, given the parallels between acoustics and optics, and the way Bohr's model accounted for the Balmer series of Hydrogen. You might even call Einstein's comment "the highest form of musicality in the sphere of thought." Charlie Faust (talk) 15:05, 14 March 2025 (UTC)