Talk:Neutron

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Former good article nominee Neutron was a Natural sciences good articles nominee, but did not meet the good article criteria at the time. There are suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
June 16, 2012 Good article nominee Not listed
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Wikipedia Version 1.0 Editorial Team / v0.5 / Vital
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GA Review[edit]

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This review is transcluded from Talk:Neutron/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: StringTheory11 (talk · contribs) 04:46, 14 June 2012 (UTC)

I will review this article. StringTheory11 04:46, 14 June 2012 (UTC)

I am sorry, but I will have to quick-fail this article due to a SEVERE lack of sources and bad prose. I feel that I have to downgrade this article to a C, which I have done. StringTheory11 18:01, 17 June 2012 (UTC)

GA review – see WP:WIAGA for criteria

  1. Is it reasonably well written?
    A. Prose quality:
    B. MoS compliance for lead, layout, words to watch, fiction, and lists:
  2. Is it factually accurate and verifiable?
    A. References to sources:
    B. Citation of reliable sources where necessary:
    C. No original research:
  3. Is it broad in its coverage?
    A. Major aspects:
    B. Focused:
  4. Is it neutral?
    Fair representation without bias:
  5. Is it stable?
    No edit wars, etc:
    Requesting semi-protection due to vandalism
  6. Does it contain images to illustrate the topic?
    A. Images are copyright tagged, and non-free images have fair use rationales:
    B. Images are provided where possible and appropriate, with suitable captions:
  7. Overall:
    Pass or Fail:

A few preliminary points to work on:

  • There is a citation needed in the lead. This will need to be fixed.
  • The references in the "further reading" section are not complete.
  • Refs 1, 2, 8, 10-13, and 17 need to be more than bare URLs.
  • Many refs need access dates.
  • This article has many unreferenced paragraphs. I am of the opinion that every paragraph should have at least one reference before an article is a GA.
  • I would rename "sources" to "natural sources", and move all artificial source info into "production". Also, the section needs to be expanded.
  • Many subsections in "intrinsic properties" are too short to comfortably be sections. I believe that if a section only has one paragraph, it is not worthy of a section. Either expand these or merge then with other sections.
  • "Neutron compounds" should be a subsection of "intrinsic properties".

More to come later. StringTheory11 04:21, 16 June 2012 (UTC)

CPT violation[edit]

I would suggest to either remove or rephrase the sentences

The fractional difference in the masses of the neutron and antineutron is (9±6)×10−5. Since the difference is only about two standard deviations away from zero, this does not give any convincing evidence of CPT-violation.[1]

The reason is, that I find it somewhat missleading for the non-expert to read this value of (9±6)×10−5. If one is not familliar with the way of how confidence intervalls are build what a standart deviation is and does not read the lengthy article linked to in the next sentence this gives a wrong impression. It would maybe be helpful to write something like, that this does not show that this value is non-zero and hence does not allow to conclude that CPT symmetry is absent. Regards, Falktan (talk) 20:40, 19 June 2012 (UTC)

Interactions[edit]

It says one of the interactions is Electromagnetic, but it's neutral and not affected by the electromagnetic force. It's composed of quarks that are, but it's a neutral particle. ScienceApe (talk) 19:44, 20 June 2012 (UTC)

I think thats ok: The neutron has a magnetic dipole moment and hence interacts with magnetic fields. Regards, Falktan (talk) 12:01, 21 June 2012 (UTC)
What does that mean? ScienceApe (talk) 16:44, 21 June 2012 (UTC)
It means that each neutron acts like a little magnet. Put it in an inhomogeneous magnetic field (one that has a gradient) and it will experience a force. That's an electromagentic interaction. SBHarris 20:34, 21 June 2012 (UTC)
So then by implication it should be possible to collimate neutrons into a beam correct? ScienceApe (talk) 20:28, 22 June 2012 (UTC)
In theory, yes. [1] It's been difficult in practice since the magnetic moment is so small. SBHarris 20:33, 22 June 2012 (UTC)

Neutron lifetime[edit]

The neutron lifetime should be updated as it was lowered by the Particle Data Group to 880.1 s. see: http://pdg.lbl.gov/2012/listings/rpp2012-list-n.pdf — Preceding unsigned comment added by 138.246.2.58 (talk) 10:06, 21 March 2013 (UTC)

It should also be mentioned that the two main methods for measuring neutron lifetime give apparently consistently inconsistent results, the current best results for the "beam" method being 887.7 ± 2.3 s, see http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.111.222501 --Ørjan (talk) 05:46, 3 December 2013 (UTC)

That's a ever-so-slightly eye-raising for physicists in the field, but it's certainly not much cause for a concern on Wikipedia. 880.1 ± 1.1s and 887.7 ± 2.3 s fall within about 2.2σ of each other. Headbomb {talk / contribs / physics / books} 06:01, 3 December 2013 (UTC)
Oh I see, you meant beam lifetime vs bottle lifetime. Yeah something could be mentioned about that I supposed. Headbomb {talk / contribs / physics / books} 06:01, 3 December 2013 (UTC)

How does the quark structure model quantitatively account for the neutron lifetime?--188.26.22.131 (talk) 10:31, 3 December 2013 (UTC)

For something "ever-so-slightly eye-raising for physicists in the field", the paragraph in PDG sounds rather desperate. They "once again call upon experimenters to clear this up" and they are clearly unhappy with not having been able to quote a satisfactory interval since 2006. If you are happy to quote "just under 15 minutes", the problem goes away of course, but you cannot then quote "881.5±1.5 s" in brackets as if the 1.5s were just a regular standard deviation. The value is given with the rather unusual qualification of "we can think of nothing better to do" and "Note that the error includes a scale factor of 2.7. This is a jump of 4.2 old (and 2.8 new) standard deviations. This state of affairs is a particularly unhappy one, because the value is so important."

Under "mean life time", it should be noted that "the state of affair is a particulalry unhappy one" because experimenters for close to a decade haven't been able to decide whether the lifetime is about 880 or about 885 seconds. --dab (𒁳) 12:03, 18 January 2014 (UTC)

Magnetic field influence[edit]

The article should mention if there is some influence on neutron lifetime by magnetic fields. (a neutron beam in magnetic field for instance)--193.231.19.53 (talk) 10:11, 7 January 2014 (UTC)

Thermal Neutron[edit]

The comment:

"thermal neutrons have a much larger effective cross-section than faster neutrons"

does not appear to be correct. This is insinuating that the cross-section is a property of the neutron. The cross-section is a property of the material whereas the effective relative velocity between the neutron and the target nucleus changes the cross-section. This is most easily reflected in the 1/v dependence, save for nuclear resonances. — Preceding unsigned comment added by Jesse.johns (talkcontribs) 00:51, 30 November 2013 (UTC)

The cross section is a property of the SYSTEM of particles, not either alone. I will fix it. SBHarris 06:45, 3 December 2013 (UTC)

De-(un)-archiving[edit]

Arhive 2 of this talk page has not many valid reasons to exist, most of it is relevant to present discussions, it should be unarchived, but I don`t know how.--188.26.22.131 (talk) 10:02, 3 December 2013 (UTC)

All these discussions are stale and several years old. If you have specific comments, feel free to unarchive specific threads (like I did below), but the bulk of these discussions should stay archived. Headbomb {talk / contribs / physics / books} 13:45, 3 December 2013 (UTC)

Magnetic moment[edit]

Un-archived from /Archive 2 on 3 December 2013.

How is explained the nonzero magnetic moment of the neutron, unusual for a electrically neutral particule?--MagnInd (talk) 10:24, 6 August 2010 (UTC)

Neutrons are not fundamental particles. They have electrically charged quarks inside of them. Dauto (talk) 15:25, 30 August 2011 (UTC)

How about Rutherford model? How do the models account quantitatively for the observed magnetic moment of the neutron in comparison one to the other?--188.26.22.131 (talk) 10:14, 3 December 2013 (UTC)

Is there any published comparative quantitative explanation of the magnetic moment by quark model and Rutherford model to decide which one is best? Or at least just of a quantitative account of the magnetic moment by the quark structure model?

I'll rephrase my edit to my first edit, whithout the claim of experimental support for Rutherford model, to which I understanding user Headbomb objects.--188.26.22.131 (talk) 10:29, 3 December 2013 (UTC)

This material simply is unfit for Wikipedia. First you say Rutherford's model is derelict, then follow up with a "well the jury is still out on this". Rutherford's guess was made at a time when no one knew of quarks, he did the best with what he had around at the time. But the jury has been in on this for 50+ years, and what accounts for the neutron's magnetic moment are the intrinsic magnetic moment of quarks. See doi:10.1007/BF02760010 and references therein. Headbomb {talk / contribs / physics / books} 13:31, 4 December 2013 (UTC)
I haven't said is derelict, just considered so. A more cautious phrasing is needed. The issue in discussion here is not wether or not neutron is made of quarks, but the explanatory power of structure models formulated over the time since the prediction and discovery of the neutron.--188.26.22.131 (talk) 10:55, 16 December 2013 (UTC)

text/reply brought from Wikiproject Physics:

Has anyone any objection to the above proposal of a more cautious wording?--193.231.19.53 (talk) 10:00, 17 December 2013 (UTC)
Yes. The Rutherford model explains nothing because it is wrong. Headbomb {talk / contribs / physics / books} 15:08, 17 December 2013 (UTC)

end of brought text — Preceding unsigned comment added by 188.26.22.131 (talk) 14:18, 20 December 2013 (UTC)

I have noticed this discussion and also the article proton spin crisis which I understand is an unsolved puzzling problem. Is there an article that tries to treat proton spin crisis based on quark structure of the proton?
As a remark, it appears from the Nuovo Cimento source that the quark structure model create more problems than it solves. It would interesting to see if there is a calculation of magnetic moment of the neutron based on the Rutherford model. If there is, a comparison between the models in regard to explanatory power would be useful.--193.231.19.53 (talk) 09:51, 5 December 2013 (UTC)
Only a quantitative comparative test of the explanatory power of two structure models would allow the categorical conclusion that neutron consist of quarks, if the quark structure has a better quantitative explanatory power. It seems that a comparative test of the two models has not been done. Therefore both structure models should be presented in the article.--193.231.19.53 (talk) 11:04, 10 December 2013 (UTC)
No. That neutrons are made of quarks has been established since the 1960s. Please stop wasting editor's time. Headbomb {talk / contribs / physics / books} 14:23, 10 December 2013 (UTC)
This is not waste of time, it is a legitimate aspect of scientific investigation procedure, by another name an application of the scientific method. The claim that neutrons are made of quarks has been established since the 1960s has little scientific support from the point of view of exaplanatory power. I have asked you if you aware of data regarding magnetic moment of quarks. You have rather dismissed the issue on a rather superficial analysis, so the quantitative account of magnetic moment by quarks is not very clear. The statement about the explanatory power of the two models should in the article. A clarification is needed, in the 1960s hypotheses about quarks were formulated, not established categorically.--193.231.19.53 (talk) 15:32, 10 December 2013 (UTC)
It is indeed a waste of time (see WP:CHEESE). The existence of quarks (and likewise that neutrons are made of quarks) has been established beyond a shadow of doubt since the late 1960s. Headbomb {talk / contribs / physics / books} 15:43, 10 December 2013 (UTC)
Comparing this discussion with WP:CHEESE is ridiculous.--193.231.19.53 (talk) 10:17, 17 December 2013 (UTC)
As stated above, the present discussion is not about wether or not neutron is made of quarks.--188.26.22.131 (talk) 10:58, 16 December 2013 (UTC)

text brought from Wikiproject Physics:

Rutherford's article from 1920 concerning prediction of a neutron has been brought to my attention long before the recent mention of someone like Santilli by Headbomb. If someone like Santilli considers worth buiding upon Rutherford's hypothesis, that is an entirely different aspect.--193.231.19.53 (talk) 10:09, 17 December 2013 (UTC)
There are a fair number of arguments that show that a neutron cannot be made of a proton+electron. Consider the following:
  1. Decay of a neutron yields a proton, electron, and an electron anti-neutrino. Now, maybe you could argue that the protron and electron are somehow "stuck together" in the neutron, but surely you agree that nothing can possibly confine the neutrino to the neutron? Remember, neutrinos are perfectly capable of penetrating light years of matter.
  2. Even the notion that a proton and electron could stick together is flakey, because of the Heisenberg uncertainty principle. It is quite simply inconceivable that an electron can be confined to the volume of a neutron.
  3. The electron is not subject to the strong force, so it can not be made to "stick" to the proton. Electromagnetic associations of protons and electrons are known as "hydrogen atoms".
  4. These arguments show that the electron and anti-neutrino could not have pre-existed as neutron constituents. The only explanation that makes sense is that the electron and the anti-neutrino were created during the decay event. Do you need more proof? I got more proof.
Stigmatella aurantiaca (talk) 00:00, 18 December 2013 (UTC)
As for arguments relating to the magnetic moment, see SSM Wong (1998), "Magnetic Dipole Moment of the Baryon Octet", Introductory Nuclear Physics, § 2.8, pp. 48ff, ISBN 978-0471239734  (or any other intro to nuclear physics textbook, really).Headbomb {talk / contribs / physics / books} 03:10, 18 December 2013 (UTC)
Wong ref--193.231.19.53 (talk) 10:32, 13 May 2014 (UTC)
It turns out that the quark model cannot account for neutron magnetic moment, just for the ratio of magnetic moments of proton and neutron.--193.231.19.53 (talk) 11:51, 13 May 2014 (UTC)

Neutron mass measurement[edit]

The article should present the methods for measuring the mass of the neutron and the (tacit) assumptions (if there are) involved in measuring.--5.15.206.141 (talk) 12:33, 3 January 2014 (UTC)

Magnetic moment of an elementary neutron[edit]

I am puzzled by the discussion of the non-zero magnetic moment, which considers only the Rutherford model of the 1920s and the quark model of the 1960s which is now accepted. Historically there was a 30-year period, roughly 1934-1964, when the neutron was considered to be an elementary particle, and known to have spin 1/2 which excluded the Rutherford model. Quarks of course had not yet been thought of. So my question is: if a neutral elementary particle cannot have a magnetic moment, then how was the magnetic moment of the neutron explained during this period?? Dirac66 (talk) 02:36, 16 January 2014 (UTC)

Perhaps it wasn't explained at all, even the quarks at present have a weak explanatory power as can be seen from the mentioned source fron Novo Cimento. Or perhaps the Rutherford model has not been fully replaced until the conceptualisation of quarks.--188.26.22.131 (talk) 11:02, 27 January 2014 (UTC)

Synthesis from proton and electron[edit]

What conditions are necessary for the occurence of synthesis of free neutron from proton and electron?--188.26.22.131 (talk) 15:41, 7 February 2014 (UTC)

Radius[edit]

What methods are there for determining the radius of a neutron?--188.26.22.131 (talk) 12:48, 28 March 2014 (UTC)

Per wp:talk page guidelines, please take this to wp:Reference desk/Science. - DVdm (talk) 12:51, 28 March 2014 (UTC)
But perhaps this question should be considered as a suggestion for addition of content to the article. A more correct phrasing would be Can we add a section to the article to consider what methods there are for determining the radius of a neutron? Dirac66 (talk) 15:45, 28 March 2014 (UTC)
Or, equivalently, should the article give some estimate of the effective size of the neutron? (e.g. effective density in a nucleus, average internal quark separation, etc.) Intuitively, there might be various measures of this, since it is not a point particle like an electron. Yet, at a glance, the article seems to make no mention of any size-related figure. —Quondum 17:46, 28 March 2014 (UTC)
Yes, I think the article should, and I'll try to spare some time to do that soon. Dan Gluck (talk) 14:40, 20 June 2014 (UTC)