Talk:Brownian motion

make page (in 2025): Brownian battery

Is related to:

• Physicists build circuit that generates clean, limitless power from graphene
  

by University of Arkansas - phys.org — Preceding unsigned comment added by 2a02:587:410b:c290:5918:f010:9a03:72e9 (talk) 23:10, 3 October 2020 (UTC)

Statistical mechanics theories

Einstein's theory

In the subsection Brownian_motion#Einstein's_theory, at the first line of the Taylor Series expansion, we have the following equality:

$\rho (x,t)+\tau {\frac {\partial \rho (x)}{\partial t}}+\cdots =\rho (x,t+\tau )=\int _{-\infty }^{\infty }\rho (x-\Delta ,t)\cdot \varphi (\Delta )\,\mathrm {d} \Delta =\mathbb {E} _{\Delta }[\rho (x-\Delta ,t)]$

On the right hand side, why do we have $\rho (x-\Delta ,t)$ insted of $\rho (x+\Delta ,t)$?, since Einstein himself derived the Diffusion Equation from $f(x,t+\tau )=\int _{-\infty }^{\infty }f(x+\Delta ,t)\cdot \varphi (\Delta )\mathrm {d} \Delta$.

Zaphodxvii (talk) 04:31, 31 December 2020 (UTC)

References

UiawsbdNicoDude

To editor UiawsbdNicoDude: Wikipedia takes a dim view of self-proclaimed experts because we only regurgitate sources. If you have a disagreement with content, please explain if you think a cited source is not reliable, if you think the content does not accurately summarize what the source says, or if you have better sources. I ask all new editors to temper their enthusiasm with humility, as we have a system here that has worked for twenty years and we do not need your lack of collaboration. (I am not watching this page, so please ping me if you want my attention.) Chris Troutman (talk) 04:36, 2 December 2022 (UTC)

Article issues and classification

Greetings. The article has been tagged since 2012 with "citation needed". The B-class criteria (#1) states, The article is suitably referenced, with inline citations. It has reliable sources, and any important or controversial material which is likely to be challenged is cited.

There is also a "needing clarification" tag since April 2010 and "too technical" since June 2011. Criteria #4 states, The article is reasonably well-written and #6 states, The article presents its content in an appropriately understandable way.

There are many unsourced paragraphs and the article fails the B-class assessment. -- Otr500 (talk) 08:07, 27 February 2023 (UTC)

The last paragraph of the history section claims that Einsteins 1905 paper and Smoluchowskis 1906 paper present Brownian motion as proof that molecules exist. I have now, for another reason read those papers, and at no point is the existence of molecules questioned, or considered necessary to be proven. Both papers already work within the assumption that molecules exist. -- 141.76.69.115 (talk) 09:55, 21 June 2024 (UTC)

This is why Wikipedia relies on secondary sources. The papers indeed "assume" molecules. Based on this assumption, the physical model of Brownian motion makes certain predictions which match critical experimental evidence which otherwise is not explained. Retrospectively, historians trace the acceptance of molecules to the realization that these papers provide a good model, and hence molecules became broadly accepted. That is how physics proceeds. Primary sources should not be the basis of claims in Wikipedia. Johnjbarton (talk) 14:46, 21 June 2024 (UTC)

I think then a secondary source should be cited there. 141.76.69.115 (talk) 08:14, 2 July 2024 (UTC)

Instantaneous velocity of a Brownian particle

What is the instantaneous velocity of a Brownian particle modeled by a Wiener process? Clothclub (talk) 18:33, 11 January 2025 (UTC)

Proposed summary for technical prose

I've been using Google's Gemini 2.5 Pro Experimental large language model to create summaries for the most popular articles with {{Technical}} templates. This article, Brownian motion, has such a template in the "Riemannian manifold" section. Here is the paragraph summary at grade 5 reading level which Gemini 2.5 Pro suggested for that section:

Imagine a tiny speck moving around randomly, like dust dancing in a sunbeam. This is called Brownian motion. Usually, we think about this happening on a flat surface, like a piece of paper. Scientists have a special math rule to describe this flat movement. But what if the speck is moving on a curved surface, like the outside of a ball? Scientists can change the math rule slightly to work for curved surfaces too. This helps them understand how the speck would jiggle and move randomly even when it's not on a flat place.

While I have read and may have made some modifications to that summary, I am not going to add it to the section because I want other editors to review, revise if appropriate, and add it instead.

For this particular case, I am not so sure that "dust dancing in a sunbeam" is actually Brownian motion, and not air currents and turbulence which are much larger scale phenomena. But perhaps someone can think of a better analogy, or perhaps the flawed example still serves to explain the section in non-technical terms for the layperson, without confusing expert readers? I'm really not sure about this one.

This is an experiment with a few dozen articles initially to see how these suggestions are received, and after a week or two, I will decide how to proceed. Thank you for your consideration. Cramulator (talk) 12:42, 2 April 2025 (UTC)

This is not well-written professional encyclopedic prose (although the section on Riemannian manifolds is terrible for other reasons). Tito Omburo (talk) 15:49, 2 April 2025 (UTC)

If this paragraph were added I would revert it immediately as inappropriate to the section and unsourced.

If you want to pass some time, try asking your LLM for the reliable sources backing the claims emitted. Be as critical as you would if a human made the claims and produced the refs. In my experience Gemini only provides plausible answers, not correct ones, and does not actually have good sources. When pressed it will produce the sources in a Wikipedia article that I have added as if it used them ;-). Johnjbarton (talk) 16:04, 2 April 2025 (UTC)