Talk:Neutron

Developing a "to do" list for this article

The article has been fairly stable lately (I've boldly archived what seemed like old and resolved discussions), but it seems there are still important tasks needed for the article. Perhaps we can communally make a list of what's still needed. (These first three items have nagged at me for years.) Bdushaw (talk) 12:26, 29 November 2023 (UTC)

• 1 Citations. The article often lacks citations for much of the discussion, and presently also includes citations in the lead. There is a lot of work needed to clean up the citations. These are often quite difficult, IMO - we've tried to write an article that introduces a complex topic in simple-to-understand language, and often finding a good citation for such simplifications is challenging. Even starting from an undergraduate text on Nuclear Physics would likely be overly complicated language. Nevertheless, citations needed.Bdushaw (talk) 12:26, 29 November 2023 (UTC)
• 2 Reconciling lead and text. Not a major task, but presently the lead involves material that has not been already included in the article itself. (e.g., Trinity Test, Chicago Pile)Bdushaw (talk) 12:26, 29 November 2023 (UTC)
• 3 I've mostly worked on the upper parts of the article. The parts further down regarding neutron sources and applications are out of my expertise. Those sections likely need a clean up. Indeed, I am wondering if perhaps this article ought to focus on just the neutron itself, and break out some of these sections into a new article on Neutron applications, say. Leaving a brief summary, much like the "Discovery" section was broken out.Bdushaw (talk) 12:26, 29 November 2023 (UTC)

  Completely agree about #1 and #2.

  Most sections the later half have existing articles, so rather than split, it makes more sense to me to move material out of this article and into the existing split-off ones. Make the sections more summary than mini-articles. I bet there are more split-off articles existing, eg I just linked Beta-decay.

  The "Description" section amounts to an extended lead; the entire article is a "description of the Neutron" right? The section could be a lower-level "Overview", but purpose of the section needs to be clarified.

  Having two decay sections is puzzling. There should be one, eg "Lifetime" or "Decay processes" section.

  "Intrinsic properties" should just be "Properties" and come before "Decay processes".

  The section on "Dineutrons" should be one sentence in "Properties". The 'Neutron compounds' section should be "Neutron stars" or "In neutron stars". Free dineutrons are barely notable but Neutron stars are a major aspect of neutron physics.

  There should be a section on neutron radiation hazards maybe as a rename of the odd "Protection" section.

  Good luck! Johnjbarton (talk) 15:34, 29 November 2023 (UTC)

Contemplating the article organization, I mostly agree with some of the suggestions by Johnjbarton. The "Description" section reads like an extended lead. The section "Beta decay and the stability of the nucleus" is really not about beta decay, but about how the neutron and proton build nuclei (with reference to beta decay) - the section wanders a bit. The section "Decay of the neutron by elementary particle physics" could really be "The neutron in the Standard Model" and include the quark discussion from "Description". I am not sure the lower sections (Neutron compounds and below) should be included/have such lengthy discussion. Should this article include a discussion on neutron detection?-(Philosophical question). Condense and farm out parts to other articles or new breakout articles? I am not entirely sure in how to proceed; I post this for comments/ideas. Bdushaw (talk) 20:07, 1 January 2024 (UTC)

First, I suggest leaving the intro work until it's clear what other changes make sense. Other changes might include moving material out of the intro. Once it is clear what the article will say, the intro can mirror it with brevity.

Second, references are important, so they should not be inadvertently deleted and purposeful deletions clearly described in the edit summary or Talk. Similarly any section without references are top priority for improvement.

Third, moving material from here into Main article if possible will improve both. If its just duplicate, then cut it here. I would avoid new breakout articles without building consensus: we have too many leaves and not enough sturdy branches. (Eg start a Talk item, explain why, and post it to the Physics talk for feed back.)

Fourth: just start.! If you make logical sized edits with descriptions, other editors can quickly revert if they don't agree and we can work it out.

Ok maybe you were looking for something more specific, but just start. For advice on a specific section, open a specific Talk topic. Johnjbarton (talk) 03:21, 2 January 2024 (UTC)

I noticed that you are "cutting" in one edit and "pasting" in another. It's much better if you can do this in one edit. Otherwise the edit history has large minus and large plus sized changes and that triggers bots and editors to check what goes on. Johnjbarton (talk) 15:35, 2 January 2024 (UTC)

Yes, I've run into trouble before as you say, but doing it this way is the only way I can keep track of things...it can get confusing in a hurry. I am careful to state what I am doing in the edit summary now to fend of mid-copy-paste reversions! Anyways, it has been a hatchet job so far of reformating/sketching a possible reorganization. Everyone should see how they like it - revert back to how it was if you are not happy with what I have in mind. Trying to get to a more conventional article format and organization. Not sure where to put "Discovery" - that might be better as a section further down in the article. Such large changes make a bit of a mess of the article, so more cleanup likely required. I've been able to remove quite a lot of redundancies so far. Stopping for now. Bdushaw (talk) 15:56, 2 January 2024 (UTC)

I hope to start working on improving the citations for the article in coming weeks. I still eye the lower half of the article - from Neutron compounds to temperature. I am not knowledgeable about these issues, but know enough to know these sections are bloated and disorganized...I may take a machete to these sections at some point, with the understanding, as mentioned above, that there will be no problem with reverting the hacks. For example, there is a (quite interesting) discussion of neutrons and their behavior on Mars that may or may not be warranted. It would be nice to bring this key article to "good article" status! Could it be possible? Bdushaw (talk) 10:31, 20 March 2024 (UTC)

It would be awesome if you moved most of the content in the "Neutron temperature" section to neutron temperature, leaving a single paragraph summary. Johnjbarton (talk) 15:42, 20 March 2024 (UTC)

comment

I propose to change

... is possible because the mass of the neutron is slightly greater than that of the proton.

to

... is possible because the mass of the neutron is slightly greater than that of a proton-electron free pair. 151.29.78.113 (talk) 09:26, 28 March 2024 (UTC)

Sorry I don't think either of these phrases are correct. These imply that energy is the only consideration in decay processes, but that is not true.

I reworked the section but I'm not happy with the result. I think the decay is more complex than a few sentences can convey. The previous text was also trying to talk about the possible application of the decay energetics to neutrinos physics but again not enough was said to make it clear. Johnjbarton (talk) 16:00, 28 March 2024 (UTC)

I agree. I have just proposed to refine the necessary condition that was far too sloppy. Thanks and good Easter. 151.29.78.113 (talk) 06:24, 29 March 2024 (UTC)

It took me a moment to realize what the original poster was referring to - it is true that for the neutron to decay its energy/mass must be greater than not just the proton, but the energy/mass of the separate proton+electron+neutrino. I am not yet sure how to phrase that in the text; with somewhat of a worry of getting too bogged down in details. There are a multitude of caveats with physical facts, to stop and describe them all in an article is often counterproductive. (On a nuclear scale the mass of an electron seems tiny.) (One could also refer to a "bound" proton+electron, which would "decrease" their total mass with the binding energy, etc.) Bdushaw (talk) 10:14, 1 April 2024 (UTC)

The "free" neutron - half time

If the mean lifetime is 879.6±0.8 s then the half time is 609.7±0.7, not 610.1±0.7 s. Maybe this was caused by using "ln(2) = 0.693". Mc22222 (talk) 12:19, 29 March 2024 (UTC)

 Done thanks Johnjbarton (talk) 17:25, 29 March 2024 (UTC)

A sentence on "free" proton decay

I restored the sentence noting that "free" proton decay is disallowed on grounds of energy. There are several concerns. Regarding "unsourced", I waive it away for now - as noted above, citations are generally needed, and hopefully will be provided this summer. The point may be "obvious", but, of course, "obvious" is in the mind of the beholder - it doesn't hurt to (re)state key points that may be obvious - our audience is general; some people will appreciate all the help we can give them. We have had 2-3 complaints on these Talk pages to the effect that "proton" decay does not occur, this with respect to the discussion further down regarding protons in the nucleus. A statement to this effect, acknowledging that "proton decay" does not occur, is therefore useful. Further, the reverted sentence serves as a lead in to that discussion further down regarding protons in the nucleus. Perhaps there is a better way to state the point (does it need its own paragraph?), but it seems important to retain an explicit statement of this fact. I am always open to convincing argument, however! Bdushaw (talk) 10:00, 1 April 2024 (UTC)

I think you could include a statement about the stability of products of the free neutron decay directly after describing those products. The stability of the products is physically significant (esp. regarding observing the products) whereas the "reverse reaction" is a made up thing.

For the purposes of the audience I think the energy carried away by the products is helpful to describe. The refs for neutron decay mention it, but they are advanced sources and what we need is something on the e=mc2 level. Johnjbarton (talk) 16:00, 1 April 2024 (UTC)

neutron "mean lifetime"

Perhaps this has been discussed already, but I've stepped in it just now...the controversy regarding the neutron's lifetime. There are discrepancies between the mean lifetimes of ultracold neutrons and "in beam" neutrons. Out of ignorance, I've just modified the numbers to the ultracold neutrons. We should decide what to do...and mention the controversy perhaps? I seek a consensus... Bdushaw (talk) 12:53, 1 April 2024 (UTC)

From the neutron lifetime article: "On 13 October 2021 the lifetime from the bottle method was updated to τ n = 877.75 s [13][1] increasing the difference to 10 seconds below the beam method value of τ n = 887.7 s [14][15]"...so our values should be updated. 10 s is no small number! Bdushaw (talk) 13:06, 1 April 2024 (UTC)

I took a stab at including a short paragraph on the issue...there does not seem to be much point in specifying a precise value for the lifetime just yet, given how the measured numbers are changing and conflicting! Bdushaw (talk) 13:42, 1 April 2024 (UTC)

The Particle Data Group value is the recognized standard and their value should be quoted. I updated the ref. However the current text has derived values so we have no idea if they are correct or not. Johnjbarton (talk) 15:12, 1 April 2024 (UTC)

But there is no "standard" value... The citation actually talks about averaging the "bottle" values with one of the "beam" values, but those values are different, hence shouldn't be averaged. Meanwhile, both values seem to be changing year by year! Bdushaw (talk) 15:19, 1 April 2024 (UTC)

The reverse reaction

I'm deleting for the second time this claim:

• The reverse reaction, that is, the decay of a free proton to a neutron, is energetically disallowed, unless additional energy is provided, such as from a high-energy collision of a proton with an electron or neutrino.

I believe the claim is correct but unreferenced. It is correct in the same way as "thing don't fall up" or "it's not dark when the Sun's out". If there is a reference that makes this point we should explain why it is significant. Johnjbarton (talk) 15:14, 1 April 2024 (UTC)

I commented above already under "A sentence on "free" proton decay". You've been harping on "unreferenced", but, as I have already acknowleged above a couple of times, supporting much of this article with proper citations will be an ongoing, lengthy task. I object to suddenly enforcing this standard just now without giving us the opportunity to work through this challenging problem. (Otherwise you'll just delete large sections of the article...to no purpose) Bdushaw (talk) 15:25, 1 April 2024 (UTC)

FWIW I don't delete just because things are unreferenced. I do delete quite a bit of unreferenced material because the content is confusing and without a ref I can't fix it.

I think this paragraph is superfluous. A ref might explain what makes the statement significant and then I could change the content. But it does not have a ref. If one shows up the content can be returned with further explanation. Johnjbarton (talk) 15:52, 1 April 2024 (UTC)

Why half-life?

I removed the free neutron half-life value then @Bdushaw put it back. The references provide the mean lifetime. Calculating then adding the half-life makes the article error prone (see discussion above under topic The "free" neutron - half time'). More important it is confusing for readers. "Why are there two such numbers? Why are they different?" The half-life is extraneous information. If a reader needs half-life it can be up to them to convert. Johnjbarton (talk) 15:19, 1 April 2024 (UTC)

We seem to be working at cross purposes, which I am sorry for. I think it is worthwhile to include both values (mean lifetime and half-life) as a service to the reader; I disagree with the idea of having the reader calculate it for themselves. It is not extraneous to the extent that readers may have encountered neutron "half-life" elsewhere and looked up this article for more information. Recall the reader level is the general public; few will know how to calculate half-life from mean lifetime. I'd be open to just including the value in the table at upper right. Or a brief sentence elucidating the difference. Bdushaw (talk) 15:31, 1 April 2024 (UTC)

Yes, I think we are considering the same kind of reader. But I don't think "both" is service, but a confusion because now they have to ponder two things.

With only the value given in standard refs we are also aligning with standard practice. If a reader only knows half-life from another source, the link to mean lifetime explains the difference. Johnjbarton (talk) 15:48, 1 April 2024 (UTC)