Talk:James Chadwick

Encarta Encyclopedia
After comparing articles from Encarta Encyclopedia, and this one, Wikipedia, I noticed that the date of James Chadwick's death differed from one to the other. In Encarta, it said tha tChadwick died December 10th, whereas here it said July 24th. — Preceding unsigned comment added by 216.16.55.2 (talk) 23:32, 22 November 2004 (UTC)


 * I don't have encarta premium...so I can't check it myself, but if that's what it says on encarta, then I would say that encarta's wrong:: ODNB states 24 July 1974Cj1340 (talk) 14:16, 21 October 2014 (UTC)

Conflicting birth years
In the header (1891) and in the box on the right of the bio (1872). --125.60.241.188 (talk) 21:58, 30 September 2008 (UTC)

Cambridge
The Cambridge Section is word for word from its link. Is that okay? —Preceding unsigned comment added by 206.82.20.126 (talk) 17:10, 15 September 2009 (UTC)
 * No, word-for-word copying from sources is not OK, unless part of a direct quote or acknowledged copying from free-use (free under copyright rules, not just no-charge) sources. I rewrote the paragraph to avoid this problem. Thanks for pointing it out. --RL0919 (talk) 18:20, 15 September 2009 (UTC)

Incorrect text
The text formerly stated that Dr. Chadwick discovered nuclear fission and that he received the Nobel Prize for this. He did not, and I have corrected this. Dr. Chadwick discovered the neutron in 1932, and he won the Nobel Prize in Physics for this achievement in 1935. In any case, this was an eartshaking discovery, and it was one of the top discoveries in Physics between 1930 and 1941. There is no need to exaggerate about Dr. Chadwick.

Nuclear fission was not observed until about 1940 by Otto Hahn and his associates in Germany. Interestingly, based on the limited amount that he published. Hahn won the Nobel Prize in Chemistry in 1944, despite the fact that several Nobel Prize awards were cancelled during World War II. Meanwhile, during the Manhattan Project in America, a HUGE amound of progress was made in deep secrecy on nuclear fission, including the world's first nuclear reactor, which "went critical" in a chain reaction in December 1942. By the end of 1944, a HUGE amount of progress has been made towards producing atomic bombs in the United States, including large reactors in Washington State that were producing plutonium-239 by the kilogram. The nuclear reactor project in Chicago was carried out by a team lead by Enrico Fermi who has won the Nobel Prize in Physics in 1938, but the plutonium production, separation, and purification project was a completely American one lead by Glenn T. Seaborg, who later won the Nobel Prize in Chemistry in 1951 and General Leslie Groves. The separation of the minority of U-235 atoms by electromagnetic means in Tennessee relied on word that had been done by Ernest O. Lawrence, an American who had won the Nobel Prize in Physics in 1939.

A big step in nuclear physics from the British Isles came beginning in about 1946 (post-war), when John Cockroft (England) and Ernest Walton (Ireland), working together, made many discoveries in the transmutation of elements. They won the Nobel Prize in Physics in 1951. (The doubtless duplicated a lot of work that had been carried out in great secrecy by Seaborg, Lawrence, and others during the Manhattan project. For example, Seaborg was a member of the teams that discovered neptunium, plutonium, curium, americium, and several other transuranium elements. On the other hand, Cockroft and Walton might have made discoveries with some of the lighter elements.) 98.67.171.176 (talk) 03:17, 15 August 2012 (UTC)

Possible resources

 * J. Chadwick (1914). Intensitätsverteilung im magnetischen Spektrum von β-Strahlen von Radium B+C. Verh. d. Deutsch. Phys. Ges. 15, 383.
 * J. Chadwick, C. D. Ellis (1922). A Preliminary Investigation of the Intensity Distribution in the &beta;-Ray Spectra of Radium B and C. Proceedings of the Cambridge Philosophical Society 21: 274-80.
 * "magnetic beta ray" = Beta ray spectroscopy in a mag field?

Headbomb {talk / contribs / physics / books} 14:43, 14 August 2014 (UTC)

Chadwick and Rutherford and their students
I've been poking at the article on Norman Feather. The Chadwick article makes no mention of the education/advising of students such as Feather at Cavendish. This activity was important to Cavendish scientific goals, paid great dividends later on, and was an important aspect of Chadwick's activities at Cavendish. Chadwick and Rutherford looked after the doctoral students as a team - selecting research topics for them that were the focus of Cavendish interests at the time. Chadwick was famous for his student training laboratory in the attic of Cavendish. The article in Proc. Roy. Soc. on the neutron was actually one of a trio of papers, back-to-back (arrangedby Rutherford to be published in record time apparently), the second of which is by Feather on neutron induced disintegrations - the point being that Chadwick was not operating in a vacuum with his discovery of the neutron. Also, I suspect the experiment that prompted by the discovery of the neutron was by the Joliet/Curies, who misinterpreted the neutron as a gamma ray - if so then the Chadwick article has an error there. See Ettore_Majorana. The article might also benefit from a "See Also" section, that might include the link to e.g., well known Chadwick students like Feather. Just some thoughts... Bdushaw (talk) 07:15, 22 August 2014 (UTC)

See also the Feather Oral History regarding the neutron discovery, etc.: http://www.aip.org/history/ohilist/4599_1.html  Bdushaw (talk) 07:39, 22 August 2014 (UTC)

I should read things more carefully...I stand corrected on my comments above regarding students. (!) Bdushaw (talk) 07:47, 22 August 2014 (UTC)
 * Étienne Biéler did not have an article, so I created one for him. Hawkeye7 (talk) 11:51, 29 August 2014 (UTC)
 * The Joliet/Curies misinterpreted their results, and thereby missed out on the discovery. Hawkeye7 (talk) 09:57, 22 August 2014 (UTC)
 * Yes, but the measurement as they reported it was a direct spark to Chadwick to look for the neutron. He and Rutherford thought their interpretation was nonsense.  The earlier German result was also important, as the Chadwick article notes.  The Feather Oral History is fascinating.
 * ✅ Done. Hawkeye7 (talk) 11:48, 29 August 2014 (UTC)

Images
We were using the image from the Nobel site bio as our lead image. This seems to have been one of several portraits shot by Howard Coster as there's another one at the NPG. There was some discussion of this in the FAC and this came to head when it was deleted at commons yesterday. I'm making a note here so we can return to the matter when the copyright on those images expires.

I substituted a crop of the picture of Chadwick with Groves. This was in TIF format like the original, which we use in the section about the Manhattan Project. Today, these have been changed to equivalents in JPEG format. This is a compressed format which is supposed to save space and so load time. So it's puzzling that, for the lead image, the TIFF file is smaller than the equivalent JPEG — 686K vs 735K. I don't suppose it's a big deal but I'd like to understand this better. Andrew (talk) 11:55, 21 October 2014 (UTC)


 * As a result of the discussion at FAC we sent the image to a deletion review on Commons and it was decided to keep it. The image was subsequently used on the front page in good faith. It was deleted by a cowboy admin from Commons without discussion. I would like to see him desysopped and indefinitely blocked.


 * I've studied the image and it could have been by Howard Coster. It is different to the NPG image. Chadwick may have had it taken and submitted it to the Nobel Prize Committee. If it is indeed from the same series, then the NPG is wrong and the image is a decade older than the NPG thinks it is. Note that he looks older in the 1945 photograph (but is still wearing the same tie).


 * The copyright on the deleted image has already expired! If we assume that Howard Coster was the photographer, then the image copyright only lasted 25 years and expired in 1960. The 70 years from the author's death is only for artistic works; it is 50 years from publication otherwise. It was first published in Sweden, therefore uses the Swedish term, therefore is PD in the UK, which recognises the lesser term. Also in the US per URAA, as it was PD in 1996.

Hawkeye7 (talk) 12:58, 21 October 2014 (UTC)


 * There's an appeal process at Commons. If you're not content with the way they do things there, then images can be uploaded independently on Wikipedia.  I usually upload images here first and tag them with keep local so that a local copy is maintained too. Andrew (talk) 13:29, 21 October 2014 (UTC)
 * After a recent incident in which Commons replaced a DYK image with a pornographic one, I think I will follow your lead. Hawkeye7 (talk) 21:06, 21 October 2014 (UTC)

neutron as proton-electron composite
I've been contemplating the brief history of the neutron as a composite of the proton and electron from the time of its discovery until it was recognized as a thing on its own. I think this article has it about right with the emphasis on the mass of the neutron compared to proton. I write because the article states that both Bohr and Heisenberg saw the neutron as elementary, whereas I don't think Heisenberg did. There is a careful review at this reference, Brown and Rechenberg (1996) cited in the neutron article. This article cites Heisenberg's famous trio of papers - but those were rather tortured insofar as the electron was concerned. He still explicitly saw the neutron as a composite, I believe; or at least didn't quite know what to think. (Bohr I know nothing of.)  I would suggest a different approach, which I am considering for the neutron article - the 7th Solvay conference had this issue front and center. So one may discuss the issue generally, without claims as to who believed what (which is likely to be incorrect - these guys were nothing if not cautious and flexible). The second factor, which I think must be mentioned, was the Fermi paper where he described how beta decay can occur by the creation of an electron, thus finally explaining where those pesky electrons came from. The Chadwick and Goldhaber paper on the mass of the neutron seems to embrace this (correct) theory wholesale. Between the mass results and the Fermi paper, the neutron as a composite was finished. I know of no big paper in which this was explicitly concluded, though (other than Chadwick and Goldhaber), that the community embraced as the definitive statement.

On the Fermi paper, this article presently has "The continuous spectrum of beta radiation, which Chadwick had reported in 1914, was explained by Wolfgang Pauli in 1930 by recourse to another hypothetical neutral particle, which Fermi named the neutrino in 1934." That seems not quite right to me - Pauli suggested, with great tentativeness, the neutrino idea. Fermi put the neutrino on rigorous theoretical foundation. I think Pauli would object to the suggestion that he "explained", as too strong a word, but I can't really speak for Pauli, of course. Bdushaw (talk) 03:09, 9 February 2015 (UTC)
 * Falsch! Hawkeye7 (talk) 21:16, 10 February 2015 (UTC)

The biography of Lise Meitner has a discussion of the neutron as composite at the 7th Solvay conference. LINK to relevant paragraphs on googlebooks (what a resource!) Bdushaw (talk) 12:09, 9 February 2015 (UTC)

I've revised the Neutron page with a narrative that I think is correct, maybe. See what you think. One want to be brief, but also accurate...its a challenge. Bdushaw (talk) 03:55, 10 February 2015 (UTC)


 * I found a good article on the subject, I have reworked the text. Let me know what you think. I'm afraid the two of us may be sounding like Bohr and Heisenberg. Hawkeye7 (talk) 21:16, 10 February 2015 (UTC)


 * That's a nice article. It is looking good to me.  I made two small changes, the neutrino changes to fix what seemed to me to be a run on sentence; I've very hesitant to edit articles like this, since I know they have a fabric that only the regular editors know.  The gamma ray in question, 2.6 MeV from Th-232, is actually unique - it has about the strongest energy of any naturally occurring gamma ray and just enough energy to disintegrate a deuteron.  The next highest energy gamma ray doesn't have enough energy.  Chadwick and Goldhaber were lucky...  At that time, of course, one could only use the radiation that nature provided.  Now to blatantly plagiarize the new material over to the neutron article...  Bdushaw (talk) 00:17, 11 February 2015 (UTC)


 * Thanks. I had trouble with this section of the article, trying to explain this part to laymen while not over-simplifying. I'm still confused myself about how a neutron can have a magnetic moment when it has no electric charge. Hawkeye7 (talk) 02:09, 11 February 2015 (UTC)


 * Does the last section of neutron magnetic moment not answer the question? It is supposed to...  Took me a moment to get the Falsch reference.  Bdushaw (talk) 03:54, 11 February 2015 (UTC)
 * The last section of neutron magnetic moment doesn't explain it at all. I guess I'll have to look up the papers. Hawkeye7 (talk) 09:50, 13 February 2015 (UTC)


 * One more correction...so sorry... It appears that the measurements of the mass of the neutron were rather confused in the 1933-4 time frame - Chadwick, Curie, Lawrence.  The 1935 Chadwick/Goldhaber result was AFTER these and rather resolved the issue - this was the first accurate measurement.  I need to double check that, here is a LINK maybe.  Even the 1935 paper concludes with some ambiguity - they needed to know the masses of the deuteron and proton better.  But that 1935 paper got the right answer - 1.0084u or 1.0090u, depending on the value for the mass of the deuteron used (1.00866u is the correct answer). One element to the confusion is that Chadwick/Goldhaber published a preliminary paper in 1934 in Nature.  I suspect this 1935 paper is the more accurate measurement that confirmed the Curie value.  Need to check the sources.  Bdushaw (talk) 04:56, 11 February 2015 (UTC)
 * I've revised the narrative concerning the early measurements of the neutron mass over on the neutron page - that is a tricky one. I hope I got it right!  The reference to the biography of Lise Meitner was most helpful.  Also this LINK to an article by Goldhaber.  Bdushaw (talk) 05:59, 11 February 2015 (UTC)
 * Pais, "Inward Bound" p. 412 confirms that the Chadwick/Goldhaber estimates (1934/5) were the best early values. Bdushaw (talk) 06:52, 11 February 2015 (UTC)

I've reworked the paragraph on the estimation of mass; hope that's o.k. I believe it now reflects the sequence of events - the Chadwick/Goldhaber estimate was the first accurate value for the mass of the neutron. I was not sure of where the values for m_n came from in the original paragraph - I've included the values that I see in the original papers by Chadwick and Chadwick/Goldhaber. Bdushaw (talk) 05:52, 13 February 2015 (UTC)
 * It's really good. But Goldhaber's 1934 paper is no longer referenced. Hawkeye7 (talk) 09:41, 13 February 2015 (UTC)
 * I saw that - I don't know that reference, but it seemed to be misplaced; I don't think it has to do with the mass of the neutron, does it? Seems unrelated to deuteron/gamma ray work.  Bdushaw (talk) 10:51, 13 February 2015 (UTC)

Parallel discovery
Hans Falkenhagen discovered neutron in the same time as Chadwick.--79.119.208.152 (talk) 15:37, 25 February 2015 (UTC)
 * There is a high probability that this is an urban legend. This text (in German) describes that in spite of intensive investigations there is (till now) no reliable source to confirm this story. --Jkbw (talk) 21:33, 20 October 2016 (UTC)