Talk:Rutherford scattering experiments

Non-scientific use of significant figures.

The section on the impulse model uses an inappropriate number of significant figures creating the impression that 1) the model is somehow amazing accurate and 2) that the mass of the atom is significant. Neither of these are true. Rutherford's own paper only uses 2 figures.

The current text directly contradicts physics: it attempts to show that the mass effect of gold is significant, but it was not historically and the impulse model assumes infinite mass for the target.

To account for finite mass, the reduced mass can be used (with a reference) and if Aluminum is used for the example a significant effect will be shown, as was noted by Rutherford on page 385. Johnjbarton (talk) 14:28, 1 June 2024 (UTC)

I am not even sure what calculations Rutherford used. I think it's enough that it be consistent with the history, not a perfect reflection. Kurzon (talk) 14:50, 1 June 2024 (UTC)

Rutherford's calculation are in his paper, and in particular he considers the effect of finite mass on page 384 in the section "Alteration of velocity in an atomic encounter". The content is not consistent with history, that is exactly my point. Johnjbarton (talk) 15:02, 1 June 2024 (UTC)

My changes to the article to correct this error have been reverted by @Kurzon. I want to know why.

A scientific model typically start with conceptual ideas that approximate a physical scenario. The ideas generate a mathematical model which leads to calculations. The results of the calculation, being numerical can be exact as far as mathematicians are concerned. But this article is about physics and the model is an approximation to an immensely complex physic system. It is inappropriate and incorrect to write three significant figures for a result that is this crude. The model prediction is about 0.02 degrees, not 0.0186 degrees. Johnjbarton (talk) 18:09, 18 June 2024 (UTC)

@Kurzon Once again I had to fix the article for this error. Please stop. Johnjbarton (talk) 22:17, 5 August 2024 (UTC)

@Johnjbarton: I looked through some history books and it seems that while Perrin and Rutherford knew each other they didn't collaborate much. Still, I'd like to know how Rutherford knew that atomic radii were on the order of 10^-10. It's a pity that you had to delete that information because I think it's interesting for readers to know where scientists got these measurements and how, though perhaps you are correct that they belong in another article, perhaps History of atomic theory. Kurzon (talk) 12:25, 2 June 2024 (UTC)

@Kurzon Just want to point out that this reply belongs on the topic "Historical measurements of the variables".

You have reverted may change to the significant figures without discussion. I continue to disagree with the content. Johnjbarton (talk) 14:01, 2 June 2024 (UTC)

Considering I'm working with an incomplete picture of what happened, I think it's OK for me to fill in a few gaps in the mathematics with educated guesses, so long as I get the maths and the physics right. Kurzon (talk) 16:19, 2 June 2024 (UTC)

I disagree, it is not OK. Your "fill in" is incorrect. Using an approximate model, adjusting it for an insignificant factor, and then using lots of significant figures to make it look significant is not correct.

And it so unnecessary! The recoil effect was discussed by Rutherford using Aluminum. Just put my text back and change your formula to use Al mass in the second case.

If your picture is incomplete, then omit it. Don't add stuff that is wrong. Johnjbarton (talk) 00:26, 3 June 2024 (UTC)

Ok Kurzon (talk) 00:28, 3 June 2024 (UTC)

Why the Thomson model was wrong

@Johnjbarton: A week or so ago you complained that the material I put on the Thomson model was wrong somehow. I think we should do a section on it, and I invite you to lay it out, since you understand the history better. Kurzon (talk) 18:14, 30 July 2024 (UTC)

Our treatment of the case against the Thomson model is spread out in the article. It is discussed in "Legacy", "Comparison to JJ Thomson's results" and some implicit parts of the experiment. Perhaps we need to rearrange the content to address the Thomson model head on.

I am opposed to a mythological discussion of how the Rutherford experiments devastated Thomson's model. It's not what happened. That's half the reason I'm against a scattering theory section on Thomson model; the other half is its distraction from the article main content.

Rutherford's scattering model deposed Thomson's scattering model, but the physics community did not understand the power of scattering models at the time. So the implications for atomic models did not sink in. In addition, Rutherford's atomic model had no electrons, it's not a replacement.

Do you think it would help to subdivide the Legacy section into "Particle scattering" and "Demise of the Thomson model"? That would draw attention to the two aspects and give them focus. The latter section could include more modern perspective. Johnjbarton (talk) 18:45, 30 July 2024 (UTC)

Let me study the matter a little further until I fully understand what you're talking about. Kurzon (talk) 11:33, 31 July 2024 (UTC)

Page 19:

• Kragh, Helge (2012). Niels Bohr and the Quantum Atom: The Bohr Model of Atomic Structure 1913–1925. Oxford University Press. ISBN 978-0-19-163046-0.
• "Shortly later Thomson’s picture of the atom faced a new and grave difficulty, namely its inability to explain the scattering experiments with alpha rays performed in Manchester by Hans Geiger and Ernest Marsden under Rutherford’s supervision (see Section 1.5). Although these experiments were highly important, the demise of the Thomson atom was not simply caused by them. The refutation of the classical Thomson process was a gradual process, during which anomalies and conceptual problems accumulated until most physicists, including Thomson himself, realized that it could not be developed into a satisfactory state."

Johnjbarton (talk) 01:37, 2 October 2024 (UTC)

Right... if the electrons circulate in the positive sphere, shouldn't they lose energy to electromagnetic radiation? Kurzon (talk) 06:47, 2 October 2024 (UTC)

No.

• Wheaton, Bruce R. (1992). The tiger and the shark: empirical roots of wave-particle dualism (1. paperback ed., reprinted ed.). Cambridge: Cambridge Univ. Press. ISBN 978-0-521-35892-7.

Page 113

• "In the article in which Larmor derived expression 5.5, he went on to suggest that radiative losses might drop almost to zero for atomic systems with more than one electron. This would be true as long as the vector sum of all electron accelerations remains zero, a situation most easily achieved when two electrons describe the same circular orbit at opposite ends of a diameter. J. J. Thomson developed this idea in 1903 for radiation from multi electron orbits, finding that the energy radiated per electron drops by a factor of roughly 1,000 for each additional electron in the ring when the particles move at a velocity of 0.01c."

Johnjbarton (talk) 16:13, 2 October 2024 (UTC)

A historical narrative for why the scattering result surprised Rutherford

@Johnjbarton: You rejected the stuff I previously wrote for Why the Thomson model was wrong. Let's talk about a more historically accurate one, then.

I looked through the 1968 paper by Heilbron you shared with me and on page 270 he addresses beta particle scattering in the Thomson model, offering two equations:

$\tan(\varphi /2)=(e_{1}e_{2})/(m'v^{2}p)$

and

$\sin ^{2}(\varphi /2)=(1+p^{2}m'^{2}v^{4})/e^{4})^{-1}$

The first one is pretty much what we produced in the article, in your write-up of Rutherford's equations and my write-up of the Hyperphysics/Beiser stuff. The second one confuses me. I'm not sure where to go from here. I found a 1906 paper by Thomson which Heilbron says is important.

https://gilles.montambaux.com/files/histoire-physique/Thomson-1906.pdf

Kurzon (talk) 10:37, 1 August 2024 (UTC)

@Kurzon I'm confused by your questions.

First "why the scattering result surprised Rutherford". Rutherford worked on scattering for probably 30 years so I'm unsure what result you have in mind, but I suppose it relates to the invented-history around the often repeated cannon ball quote and Geiger-Mardsen's results.

The 1909 Geiger-Mardsen result obviously did not surprise Rutherford: he proposed the experiment. Most experiments confirm existing ideas and so it was in this case per Heilbron and other references. However, the cannonball comment (many years after the fact) does make sense of the events between 1906 and 1909, during which time Rutherford and Geiger did many scattering experiments under the influence of Thomson's atom model. Their results did not make sense given the model. The results in around 1908 were to demonstrate that alpha particles scattered at all: that was surprising given Thomson's model. Hence the title of Geiger paper "On the Scattering of α-Particles by Matter". So yes Rutherford was overall "surprised" by the scattering results, but not by the Geiger-Mardsen result per se.

As discussed in Plum pudding model, Thomson's scattering model had three parts: 1) electron-electron Coulomb scattering (your formula above) 2) positive sphere (largely ignored by Thomson), 3) multiple scattering. The third one was essential. Let me repeat it: the multiple scattering in Thomson model was essential. Without multiple scattering Geiger's 1908 results invalidate Thomson's model. Crowther's work was exactly on this issue. Geiger's thickness dependence experiments aimed at testing the multiple scattering. That is why Rutherford's 1911 paper focuses on multiple scattering as discussed in the section "Comparison to JJ Thomson's results". He invalidates multiple scattering most of all.

But this kind of invalidation in 1911 is very weak. The experiments are crude. The sources are diffuse and poorly understood. They don't know what alpha and beta particles really are. They don't know what atoms or solids really are. One bit of new evidence against the only atomic model existing does not instantly elevate an alternative.

Most especially Thomson had established that his model had potential to explain chemistry via arrangement of the electrons. In comparison, Rutherford's model explained some experiments Geiger did which no one else performed and few understood. Rutherford's model had no electrons and the only existing model for electrons with a compact positive core was the already dismissed Saturnian model. So the 1911 paper was really only of interest to physicists like Wilson interested in scattering.

Thomson's model was not "wrong" until Bohr added new the electron model to Rutherford's nucleus. During this time it was not like Thomson's model was widely used. The very existence of atoms was still being debated.

The scattering formula in Thomson's "On the number of corpuscles in an atom" is a minor step in his analysis of absorption. Historically absorption, related to Geiger's thickness experiments, was critical in understanding the physics. However modern texts make more of Coulomb scattering because it is simpler. I don't know what trig relations connect the tangent and sin forms in Heilbron's paper on 270, but as far as I can make out Heilbron is just trying to explain where the sin formula in Thomson's paper could have come from. I don't think it is otherwise significant. Johnjbarton (talk) 17:21, 1 August 2024 (UTC)

I think I'm getting what you say. On the plum pudding article, and in Beiser, its says that the odds of a particle being deflected by more than 90 degrees after 10,000 collisions is negligible. But what about ten million collisions? If an atom contains many thousands of electrons instead of just a hundred or fewer, then the plum pudding model could produce strong deflection of alpha particles. Kurzon (talk) 16:07, 2 August 2024 (UTC)

Yes, that is one example of the many poorly known issues at the time. Geiger spent a lot of time on thickness dependence experiments for this reason. By doubling the thickness you double the number of collisions and can create a graph. Crowther had done this for beta scattering and used it to support Thomson, but his data was inaccurate for a critical range, affecting the conclusion (this from Heilbron) around p279. Johnjbarton (talk) 17:19, 2 August 2024 (UTC)

OK if I wanted to rewrite the stuff in the plum pudding model article to make it more historically accurate, what should I do? Kurzon (talk) 18:06, 2 August 2024 (UTC)

I think the plum pudding model is pretty good now. We could add a paragraph on how the beta scattering results only apparently supported Thomson's model. Beta scattering was much less sensitive to the effects Rutherford saw with alpha particles, beta scattering turns out to be quite complex, and Crowther's experiments were inaccurate in just the range that showed important effects. If you think this would be valuable I can find the refs.

Heilbron spends much of his 1968 article discussing how Rutherford had to address Crowther's results after 1906. That is, the dramatic reduction in the number of electrons discovered by Thomson did not eliminate the multiple scattering concept. They did not have good data on scattering by angle as implied by our scattering model presentations. They had a narrow cone of angles and variation with material and thickness. Within this range of data Thomson's model works. It was only the large angle scattering and careful work with thicknesses done by Geiger that showed the model fails. The quality data for this came out in Geiger's 1913 paper. Johnjbarton (talk) 16:19, 3 August 2024 (UTC)

The first three paragraphs of the Heilbron 1968 paper summarize the role of multiple scattering. Johnjbarton (talk) 18:18, 3 August 2024 (UTC)

Explicit interjection of link to (trivial) trig page

Several times @Kurzon adds something like:

• This next part makes several references to Wikipedia's list of trigonometric identities.

Why? This is among the most trivial bits of related material, not a major issue that needs to be called out. Each and every use of a trig identity can be link inline in the text. This is out of character for the article or article in general. I will keep removing this. Johnjbarton (talk) 17:49, 1 August 2024 (UTC)

I think it's useful to students to have this resource pointed out. You take this knowledge for granted. Kurzon (talk) 18:47, 1 August 2024 (UTC)

First this is not a textbook. Second an injected explicit link like this is lazy and not helpful to any readers, especially students. There are hundreds of formula on that page.

Any step in the article which is not clear to a typical reader should be clarified. An explicit link followed later by a series of obscure steps does not clarify.

To this point, you removed my description of secant which, in my opinion, is obscure for readers. Most readers will understand sin, cos, tan, maybe cot, but the rest are rarely used. My original version had links for steps. When you add new trig steps, add the appropriate links. An explicit statement that "reader, you need to learn a hundred or so trig identities to follow this" is not helpful. Johnjbarton (talk) 19:01, 1 August 2024 (UTC)

In fact I can't figure out the section that discusses the OA SA $\Phi$ geometry now. Johnjbarton (talk) 19:14, 1 August 2024 (UTC)

Writing this article (and I wrote most of it) was a learning process for me, I didn't take physics in college. I think that makes me well equipped to empathize with the laymen. I remember the parts where I stumbled. So maybe I should write the explanation and you should check it to see if I got the physics right. I wasn't aware that Wikipedia even had a list of trigonometric identities until I started studying Rutherford's work, and that was one of many stumbling blocks I had to overcome. I want to make that block easier for those who come after me. Kurzon (talk) 20:08, 1 August 2024 (UTC)

I don't see the connection. The explicit link to the overall page does not aid in understanding. If you don't know that trig identities exist, the explicit link sentence is a completely mysterious interjection. If you do know the exist, the list of 100 does not help.

The links like cotangent double angle formula lead you directly to the appropriate section.

I don't understand why you would be against that. And the OA SA geometry would be much clearer if we use sin/cos/tan and triangle sides. People who take trig learn the "opposite over hypotenuse" rules but not the reciprocal functions like secant/cosecant. Johnjbarton (talk) 21:10, 1 August 2024 (UTC)

What do you think of it now? Kurzon (talk) 16:43, 7 August 2024 (UTC)

I'm unsure which aspect you are asking about. The wikilinks for trig are fine now. I think the derivation of the SO SA bits could be a bit clearer with a dedicated diagram showing the right triangles, but I don't think this is essential.

I think overall the article is in excellent condition. Perhaps neither one of us is happy with the process but we can be proud of the net result. Johnjbarton (talk) 16:56, 7 August 2024 (UTC)

Oh come on, don't you have an appetite for argument? Kurzon (talk) 19:55, 7 August 2024 (UTC)

Feedback on current state

@Headbomb and Materialscientist: Johnjbarton is satisfied with this article, how about you guys? Kurzon (talk) 08:13, 11 August 2024 (UTC)

Unsourced statements

@Gog the Mild and SchroCat: Which unsourced statements did you have in mind? Kurzon (talk) 08:45, 15 August 2024 (UTC)

It sounds obvious, but the ones without citations at the end. These are more obvious when the sentence at the end of the paragraph - check out those paragraphs which don't have a citation at the end (both paras of the Alpha particles section, two of those in the Rutherford, Geiger, and Marsden section), etc. - SchroCat (talk) 08:56, 15 August 2024 (UTC)

Man, FA process is not worth this. Kurzon (talk) 11:41, 15 August 2024 (UTC)

Quite possibly not, but it is something required of every FA, indeed of every article; we are just a bit more formal about it at FAC. See WP:WHYCITE and WP:PROVEIT. Note "Any material lacking an inline citation to a reliable source that directly supports[b] the material may be removed and should not be restored without an inline citation to a reliable source" which is policy. Any drive-by editor could delete all of the statements in question, irrespective of the article's FAC/FA status, and if you can't be bothered to add citations there would be nothing you could do about it. Gog the Mild (talk) 11:57, 15 August 2024 (UTC)

I assume that the abbreviation in the above content "FA" means Wikipedia:Featured articles Johnjbarton (talk) 15:21, 15 August 2024 (UTC)

@SchroCat says

• "It sounds obvious, but the ones without citations at the end."

Can you help me understand "the ones"? Sentences? paragraphs? sections?

• "...Alpha particles section..."

? The whole article is about about alpha particles, can you narrow this down? Johnjbarton (talk) 15:12, 15 August 2024 (UTC)

@Gog the Mild says in an edit summary:

• Needs more citations. See talk page

But I don't see any additional information in the Talk page. Where would I look? Johnjbarton (talk) 15:14, 15 August 2024 (UTC)

The second comment of this section. Ie [1]. Gog the Mild (talk) 15:21, 15 August 2024 (UTC)

Kurzon, It's not necessarily about the FA process: it's about an article that doesn't even reflect the core policy of Wikipedia:Verifiability.

Johnjbarton The two unsourced sentences that stand out for me in the Alpha particles section are "Protons and neutrons had yet to be discovered, so Rutherford knew nothing about the structure of alpha particles." and "The scattering of alpha particles was expected to be similar. Rutherford's team would show the scattering model to be incorrect because the model of the atom was incorrect." Every piece of information needs to be supported by a reliable source (that's the verifiability policy), and these are the obvious ones there. The entire first paragraph of the Scattering theory section is also unsourced, as is the quote calling Rutherford the "the father of nuclear physics". These are the obvious ones that stand out and are examples only, rather than an exhaustive summary. Cheers - SchroCat (talk) 15:24, 15 August 2024 (UTC)

(edit conflict) Taking just the section "Alpha particles and the Thomson atom", the following statements are not cited:

• Protons and neutrons had yet to be discovered, so Rutherford knew nothing about the structure of alpha particles.
• The scattering of alpha particles was expected to be similar.
• Rutherford's team would show the scattering model to be incorrect because the model of the atom was incorrect.

The whole first paragraph of "Scattering theory and the new atomic model" is uncited.

There are many other cases.

Gog the Mild (talk) 15:30, 15 August 2024 (UTC)

You are going to think that we are being awkward, but if you are still considering FAC - and I hope you are - you will not wish to put in a load of work to get over one hurdle, to then fall at the next similar one. You need where possible to use modern sources and/or sources by third parties. There are various reasons for this, including "it is a thorough and representative survey of the relevant literature." Gog the Mild (talk) 15:43, 15 August 2024 (UTC)

@Gog the Mild

• "You need where possible to use modern sources and/or sources by third parties."

I don't understand what you are saying. Is this a paraphrase of WP:PSTS? So by "third parties" you mean secondary sources? Johnjbarton (talk) 16:03, 15 August 2024 (UTC)

Partly yes, it is a reference to PSTS, partly it refers to the part of the FAC criteria I quote. Certainly if this comes back to FAC I would be querying every cite to Rutherford, Geiger or Marsden, or older than about 30 years as to whether each is, in context, a HQ RS secondary source. And overall the article needs to be a thorough and representative survey of the relevant literature. There is a plentiful modern(ish) literature on this, it needs to be reflected in the article - over and above PSTS. Gog the Mild (talk) 16:19, 15 August 2024 (UTC)

@Gog the Mild

• There is a plentiful modern(ish) literature on this

If you have any good secondary references please let me know. Johnjbarton (talk) 17:08, 15 August 2024 (UTC)

@Gog the Mild @SchroCat I have addressed each item you listed and many more. Of course I cannot address:

• "There are many other cases."

If you add Template:cn markers in the article I will fix them.

I would like to remove the Template:more footnotes tag. Johnjbarton (talk) 23:43, 16 August 2024 (UTC)

OK, I've added several more using the {{citation needed span}} template. Unfortunately this doesn't work with the maths template or markup, so I've had to leave that out and just focus on the text elements. Much of the maths will also have to be supported, given it's showing us what's in the textbooks. I hope this all helps! - SchroCat (talk) 14:28, 17 August 2024 (UTC)

The math stuff shouldn't require citations for every paragraph since it's not facts but mathematical reasoning. Anyone with a maths or physics degree can verify the maths without sourcing. Kurzon (talk) 14:36, 17 August 2024 (UTC)

I would argue that it does need it. Although you may be right, not everyone who reads this article will have a maths or physics degree. Think: if this gets to FA, it will appear on the main page where a large number of people will read it - the vast majority won't have maths or physics degrees, and the only thing that gives them comfort that the material is correct is the little blue superscript number at the end of it showing it's supported by a reliable source. - SchroCat (talk) 14:43, 17 August 2024 (UTC)

@SchroCat Thanks! I have add refs for your marks.

• "Unfortunately this doesn't work with the maths template or markup..."

Simply placing Template:citation needed aka Template:cn on the end of the line preceding a formula works as this is where a citation would be set. Johnjbarton (talk) 17:28, 17 August 2024 (UTC)

I have added more than 30 refs in the last few days. Again I ask @Gog the Mild to remove the Template:more footnotes. I don't think it serves any purpose. The criteria:

• "This template indicates that the article cites a sufficient number of reliable sources, but uses an inappropriate combination of inline citations and general references. All material in articles must be verifiable, but outside of featured articles and good articles Wikipedia does not require the use of inline citations except to support direct quotations, material that has been challenged or is likely to be challenged and contentious material about living persons."

does not apply as far as I can tell. Johnjbarton (talk) 23:44, 19 August 2024 (UTC)

Major unexplained changes.

@Kurzon is making significant changes with no explanation. We've worked hard on this article and I don't agree with the changes. Johnjbarton (talk) 15:23, 16 August 2024 (UTC)

Shouldn't we show some equations for the Thomson scattering? Anyway, there is an issue I'd like you to help me with on the plum pudding model Talk page. Kurzon (talk) 17:51, 16 August 2024 (UTC)

• Shouldn't we show some equations for the Thomson scattering?

We should have at most a summary of the content in Plum pudding model. You have deleted the scattering model content in that article so I cannot understand why you would want to increase it here. Johnjbarton (talk) 18:12, 16 August 2024 (UTC)

Well we can leave this argument for another time. Kurzon (talk) 18:48, 16 August 2024 (UTC)

Multiple scattering Rutherford's paper

@Johnjbarton: In his 1911 paper, Rutherford explains how Thomson's equations can't be adapted to explain his experimental data and he mentions multiple scattering. Kurzon (talk) 11:05, 18 August 2024 (UTC)

Yes, and that is what the article says. Johnjbarton (talk) 15:31, 18 August 2024 (UTC)

The plum pudding stuff should be here

@Johnjbarton, Headbomb, and Materialscientist: We really ought to move the stuff about why the plum pudding model was wrong from the Inconsistency_of_the_plum_pudding_model article to this one. They go together. Kurzon (talk) 16:13, 20 August 2024 (UTC)

I disagree completely. Instead we should fix the content in Plum pudding model so it no longer focuses on "wrong" but focuses on the article topic, Thomson's model of the atom and his evidence to support it. I have already tried to do that and was reverted. Chronologically, historically, and logically each model is developed against the evidence at hand. When new evidence emerges, new models are forced to be created. Attempting to describe Thomson's scattering model by assuming Geiger/Marsden results is not going to make sense. When Thomson wrote his 1910 paper there was no large angle scattering data as far as he was concerned. Once we present Thomson's model the way he presented it, then we can have a short summary of the Rutherford's team's new results. Johnjbarton (talk) 16:37, 20 August 2024 (UTC)

Yeah, wasn't that what I did? Kurzon (talk) 08:43, 21 August 2024 (UTC)

Why do you disagree? Kurzon (talk) 17:34, 24 August 2024 (UTC)

@Kurzon Content primarily about the plum pudding model belongs in the plum pudding model article. It's up to you to justify what is an illogical partial merger.

Thomson's atom model was not refuted by scattering theory. New experimental evidence built the case for a compact nucleus and Bohr showed how a quantized orbit could explain spectra. Thompson's scattering model is historically important in supporting his atom model and by being first. It belongs where it is. Johnjbarton (talk) 22:04, 24 August 2024 (UTC)

I'm honestly baffled as to why you don't agree with what I tried to do, because I don't disagree with the historical narrative you just gave me. Kurzon (talk) 03:13, 25 August 2024 (UTC)

The title of this Topic is "The plum pudding stuff should be here". But we have an article about Plum pudding model. Why would we move that content in to this article?

The only reason you have given, is that you want "stuff about why the plum pudding model was wrong". We already have two paragraphs of background discussing the plum pudding model, a section Alpha particles and the Thomson atom, a subsection Comparison to JJ Thomson's results, and two other places where the comparison is discussed. That is more than enough stuff, or even a bit too much. On the other hand we have very little about other nuclear models. Johnjbarton (talk) 16:11, 25 August 2024 (UTC)

I guess because before you came along (at my request) this article had a section with some maths on why the Thomson model was wrong, and I want to restore that. Kurzon (talk) 17:36, 25 August 2024 (UTC)

I have reorganized the Plum Pudding model article to combine the two 1910 discussions, place the content in chronological order, and fix up the section heading to match. I think more can and should be done but that discussion should be on the Talk page of that article. Johnjbarton (talk) 23:51, 24 August 2024 (UTC)

More refs added

I added 2 refs and reworded a sentence based on Template:cn notations by @AirshipJungleman29. Please review to ensure I addressed the issues. Johnjbarton (talk) 02:43, 22 August 2024 (UTC)

YouTube video

This just happened to pop up on my YouTube feed this evening: How Rutherford Split the Atom for the First Time https://www.youtube.com/watch?v=dHrX1U7KCis RoySmith (talk) 01:07, 10 September 2024 (UTC)

A very nice video with only a couple of minor (and typical) errors.

These later experiments are covered to some extent on Proton#History and Ernest Rutherford. You could add the video as an External Link to one of these.

I originally thought to extent the Experiments section here this article is focused on Rutherford's discovery of the atomic nucleus. In fact I wonder if we should change the name of this article to "Discovery of the atomic nucleus". Johnjbarton (talk) 03:23, 10 September 2024 (UTC)

What are those minor errors? Kurzon (talk) 08:03, 10 September 2024 (UTC)

Near the beginning the video describes Rutherford's atom as having orbiting electrons, but that was Bohr's work. Near the end Wilson's cloud chamber is invented around 1919, but in fact it was in use in 1911. The details of the "whose first" bits are I believe a bit disputed but I've not read up on that. Minor stuff, the video is excellent. Johnjbarton (talk) 14:59, 10 September 2024 (UTC)

A new section which is not correct.

I have deleted most of a paragraph in "Scattering theory and the new atomic model". It starts with an assertion of contrast without meaning:

• At the atomic scale, the concept of "solid matter" is meaningless,

This is misleading because the nature of the forces does not change with scale. High speed alpha particles penetrate "solid matter" just like they penetrate atoms.

• the alpha particle will not bounce off the atom ...According to Thomson's calculations,

Thomson says nothing about alpha particles bouncing or otherwise, see

• Heilbron, John L. (1968). "The Scattering of α and β Particles and Rutherford's Atom". Archive for History of Exact Sciences. 4 (4): 247–307. doi:10.1007/BF00411591. ISSN 0003-9519. JSTOR 41133273. Page 277
  • "He unveiled the new approach on February 21, 191O, in a paper delivered to the Cambridge Philosophical Society under the title, "The Scattering of Rapidly Moving Electrified Particles." The title is in fact quite misleading: Thomson did not consider α particles, nor did he take loss of speed into account, as Wilson's results required for a general treatment; the new theory therefore applied only to the deflection of β so thin as to make the velocity degradation negligible."

By the way, Thomson viewed the alpha particle as an atom, on the same scale as say gold atoms, not as a charged particle on the same scale as beta particles.

I also do not think this section is needed: what problem does it solve? Johnjbarton (talk) 15:29, 17 September 2024 (UTC)

I watched a video by Neil DeGrasse Tyson which described the Rutherford experiment. He says that Rutherford discovered that matter was mostly empty because almost all the alpha particles went through the gold foil as opposed to all of them bouncing back like a mirror reflects light. I wanted to clarify that he always expected all of the alpha particles to go through, he didn't expect a few of them to be reflected back. Kurzon (talk) 15:38, 17 September 2024 (UTC)

It is true that Rutherford was "surprised" by the backscattering in some way, because through out the 1900's decade he was learning new things about alpha particles. Everything was a surprise. But you have to ask yourself: why did Rutherford recommend Marsden's reflection experiment? Rutherford clearly knew by the time of the 1908 experiment that alpha particles do not obey the expectations set by Thomson's model. Recall that these are very tedious experiments, so much so that Rutherford himself was unable to complete them. These people were not just trying reflection for the fun of it. The evidence shows that from 1905 on they were trying to understand why some alpha particle scattering was contrary to the existing model. The reflection results were absolutely unexpected, but not by Rutherford: he chose to do the experiment to look for the effect.

But this is not related to the text I deleted. That text was about Thomson and calculations that he did not do. Johnjbarton (talk) 03:45, 18 September 2024 (UTC)

https://youtube.com/shorts/iVpRtVJ5Uys?si=5IOmIE7m4b47hMKK Kurzon (talk) 16:05, 17 September 2024 (UTC)

I don't want to mislead readers, rather I want to lead them away from the simplistic descriptions they were taught in high school. I see a lot of videos on YouTube by Indian professors that do not do justice to the history. Kurzon (talk) 18:06, 17 September 2024 (UTC)

Ok so I just told the non-simplistic story in a different and more historically accurate way. Johnjbarton (talk) 15:56, 18 September 2024 (UTC)

Put plum pudding stuff here

I don't feel like this article is complete if the plum pudding stuff isn't here. That's like half the story. Kurzon (talk) 15:28, 25 September 2024 (UTC)

I don't agree and I don't think it's a close call.

• The article topic is the Rutherford scattering experiments. Rutherford's 1911 paper is relevant because it provides a model to explain the scattering experiment results. The Thomson scattering theory was designed to explain beta scattering. There is no evidence that Thomson ever expected his scattering theory to apply to Rutherford's data.
• If we want to say more about the plum-pudding model, then the best place to start is more discussion in Plum pudding model of the beta experiments.
• The content you describe as "plum pudding stuff" already exists in Plum pudding model, so you are essentially merging. I think we have two strong balanced articles. Taking content from one and putting here just makes this one too long and that one too weak.
• Details of Thomson's scattering model are important in the context of the beta experiments, Thomson's model, and the times represented. But after the Geiger-Marsden result, the details are not helpful because its clear that the model does not work. That is why Rutherford starts his 1911 paper with the quick calculation on turning alpha particles.
• The article already has two sections of details on scattering models. Don't think readers need more, especially when the content is available in one click.

Johnjbarton (talk) 16:12, 25 September 2024 (UTC)

• Rutherford cites Thomson's equations in his 1911 paper. That's the connection.
• I'm not merging, I'm repeating, or perhaps doing a partial transfer.
• The details help students understand the reasoning behind the plum pudding model's demise. It's there for historical reasons. This article is a history article.
• I'll delete the section based on the Hyperphysics site. It's redundant.

Kurzon (talk) 16:49, 25 September 2024 (UTC)

• Rutherford's discussion of Thomson's equations is similar to what we have now; his citation is comparable to our wikilink. Rutherford does not reproduce Thomson's derivation and neither should we.
• The content needs more context (beta scattering issues) which can be added in its current location.
• I object to the concept that Thomson's analysis is primarily valuable because it was "wrong". It was justified by the evidence of the time. Students can read the plum pudding model for both the detailed model and its historical context. The role of beta scattering on motivating Thomson's model should be covered in Plum pudding model. In this Rutherford article we can do many different things to improve the historical accuracy. For example this article over emphasizes the intensity vs angle data but historically the thickness and material dependence were just as important (the angle data was not very good until 1913).
• The second scattering model based on the Beiser reference is helpful for students as you previously discussed not being familiar with the scattering from a central potential assumed by Rutherford's approach.

Johnjbarton (talk) 18:14, 25 September 2024 (UTC)

• Thomson's model became wrong after Rutherford's alpha scattering evidence came in. If we want to show how the model was correct before that, we can certainly go into detail in the plum pudding model article.
• Once I brushed up on hyperbolic geometry, I edited your write-up to make it more accessible, filling in some gaps in your explanation. I believe it is now adequate.

Kurzon (talk) 19:30, 25 September 2024 (UTC)

@Headbomb and Materialscientist: Would you guys care to comment? I think this article needs to take a look at the plum pudding model to complete the story. It doesn't have to be as detailed as the plum pudding article itself, it just needs the maths. Kurzon (talk) 21:36, 25 September 2024 (UTC) @Headbomb and Materialscientist: Take a look at my revision and tell me what you think. https://en.wikipedia.org/w/index.php?title=Rutherford_scattering_experiments&oldid=1247703064 Kurzon (talk) 14:26, 26 September 2024 (UTC)

I agree the plum pudding stuff needs to be there. Literally every introductory textbook on the subject matter contrast Rutherford with Thomson. Explaining what Thomson model predicted and how it fails to account for large angle deflection is critical. Headbomb {t · c · p · b} 16:24, 26 September 2024 (UTC)

The article already contrasts Rutherford and Thomson models:

• Rutherford_scattering_experiments#Thomson's_model_of_the_atom
• Rutherford_scattering_experiments#Alpha_particles_and_the_Thomson_atom
• Rutherford_scattering_experiments#Scattering_theory_and_the_new_atomic_model
• Rutherford_scattering_experiments#Alpha_particle_reflection:_the_1909_experiment
• Rutherford_scattering_experiments#Rutherford's_Structure_of_the_Atom_paper_(1911)
• Rutherford_scattering_experiments#Comparison_to_JJ_Thomson's_results

The proposal by @Kurzon is to included a detailed presentation of Thomson's beta scattering theory.

@Headbomb Can you cite some text books that present Thomson's beta scattering theory? Johnjbarton (talk) 16:54, 26 September 2024 (UTC)

I don't have my textbooks with me, but Hyperphysics has the relevant math. Headbomb {t · c · p · b} 17:04, 26 September 2024 (UTC)

The reference used by the Hyperphysics site for Rutherford scattering is the Beiser textbook. That was the basis for our section "‎An alternative method to find the scattering angle". That section was deleted without an edit summary by @Kurzon.

The Hyperphysics site coverage of Rutherford scattering does not include the 1910 beta scattering paper of Thomson. That is the content being proposed now.

If I understand correctly, @Headbomb would support the addition of the content similar to Hyperphysics, which is "‎An alternative method to find the scattering angle" content, not the beta scattering content I oppose. Johnjbarton (talk) 16:13, 27 September 2024 (UTC)

I deleted the Hyperphysics stuff because it was redundant. Kurzon (talk) 08:24, 29 September 2024 (UTC)

It was not redundant. Johnjbarton (talk) 17:54, 29 September 2024 (UTC)

But you end up with the same formula. Kurzon (talk) 18:14, 29 September 2024 (UTC)

Beiser's book does a simplistic mathematical description of scattering in the Thomson model, then it goes into the Rutherford model. Before Johnjbarton came along, that's what this article did, and it lacked Rutherford's scattering model. Thanks to Johnjbarton we now have both, and makes sense to have both in this article. I don't propose eliminating the plum pudding model article, I just want to copy the maths stuff. Kurzon (talk) 17:48, 26 September 2024 (UTC)

Recent addition has serious errors.

The content added in this edit has many errors. I started to correct them but this content is in my opinion inappropriate for this article per the ongoing discussion on the topic #Put plum pudding stuff here. So rather than invest a lot of time correcting this I will just annotate it. Johnjbarton (talk) 03:18, 27 September 2024 (UTC)

I gave up even commenting. Johnjbarton (talk) 03:37, 27 September 2024 (UTC)

Hey I am glad you're paying attention. Since I copied this stuff from the plum pudding article, that article always had these errors and they're finally getting fixed. Kurzon (talk) 04:18, 27 September 2024 (UTC)

So you added content you knew was incorrect. Johnjbarton (talk) 16:20, 27 September 2024 (UTC)

There's always errors that escape my notice. Kurzon (talk) 16:30, 27 September 2024 (UTC)

Best notation for mean of a square root?

What's the best notation for expressing the mean of ${\sqrt {L}}$? Would it be ${\overline {\sqrt {L}}}$ or perhaps $({\sqrt {L}})_{\mu }$ Kurzon (talk) 05:08, 27 September 2024 (UTC)

Comments

@Tjlafave: What do your students think of this article? Kurzon (talk) 10:49, 29 October 2024 (UTC)