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Classical and modern physics

Classical physics and Modern physics could be merged into Classical and modern physics as their distinction is a defining feature of both topics. See also Distinction between classical and modern physics. fgnievinski (talk) 05:34, 3 February 2025 (UTC)

Not necessarily against the merge, but if the merge happens, I suggest starting from the Modern physics article and incorporating other content. Headbomb {t · c · p · b} 11:24, 3 February 2025 (UTC)

Merge. Looks like a win to me. Johnjbarton (talk) 15:45, 3 February 2025 (UTC)

Not a fan of the merge, both could be expanded into their proper article. Maybe a history article.--ReyHahn (talk) 18:24, 3 February 2025 (UTC)

What additional content could be added to these articles that would be unique to them as topics but would not fit on a merged page? We already have history of classical mechanics, history of electromagnetism, etc, and history of physics, so the unique historical content for both separate articles amounts to the transition. Johnjbarton (talk) 18:43, 3 February 2025 (UTC)

Is "modern physics" really well-defined enough to merit an article? By having a "modern physics" page, aren't we imposing a distinction that the physics community itself hasn't really codified? Both Classical physics § Comparison with modern physics and Physics § Distinction between classical and modern physics are unsourced and could well be called WP:SYNTH; they read like Wikipedia from 20 years ago. Modern physics should probably be a redirect to an appropriate section of Physics or History of physics. XOR'easter (talk) 21:08, 3 February 2025 (UTC)

There are many notable books with "Modern physics" in their title. As sample of the preface shows, eg "We wanted to highlight the conceptual breakthroughs represented by relativity and quantum mechanics...". I suppose there are fewer with "classical physics" as such, say rather than "classical mechanics" or "classical electrodynamics". But then:

• Thorne, K. S., Blandford, R. D. (2017). Modern Classical Physics: Optics, Fluids, Plasmas, Elasticity, Relativity, and Statistical Physics. United States: Princeton University Press.

And there are articles like:

• Misner, Charles W., and John A. Wheeler. "Classical physics as geometry." Annals of physics 2.6 (1957): 525-603.

These are clearly notable topics.

The size of the two existing articles does suggest a possible merge into Physics.

Interestingly ngrams for two terms peaked in the 1940-1960 time frame Johnjbarton (talk) 23:51, 3 February 2025 (UTC)

Both "classical" and "modern" are qualifiers that seem to be highly context-dependent. Thus, the distinction between made by the qualifier "classical" in mechanics is usually the nonrelativistic/relativistic split, and is orthogonal to the the "classical" that is used for the nonquantum/quantum split. To conflate these due to the sharing of a qualifier word would be a grave error. Oh, and here we have "Modern Classical Physics". I think this should close the case that these can be considered opposites. Let's just remove the synth (both articles) by editors who have been misled by the terminology, as well is the section in Physics. That some authors use it in titles is meaningless: they just mean it in their context. The ngram also suggests that the terminology could not gain traction, likely due to its vagueness. —Quondum 00:22, 4 February 2025 (UTC)

Sorry I strongly disagree. The sources clearly support the idea that classical physics is nonrelativistic and non-quantum. That they are orthogonal simply means you can combine them. I have read this modern/classical dichotomy in many sources.

"Modern Classical Physics" explains itself quite clearly in its preface. You can read it in the Google Books preview. It is modern treatment of the topic "classical physics".

Ngrams says both are used as much as "astrophysics" or "quantum physics". These are notable topics. Johnjbarton (talk) 01:13, 4 February 2025 (UTC)

Okay, so you contend that "classical physics" just means the same as the "classical mechanics" of the diagram in the lead of Classical physics, and the description in its lead is hogwash. That could be the case, but it would require a rewrite. —Quondum 01:28, 4 February 2025 (UTC)

No, that is not what I said. FWIW I altered the caption on the diagram you mentioned. It is not a source I use to support my case. Johnjbarton (talk) 01:40, 4 February 2025 (UTC)

Incidentally, the preface of the book that you linked says "This is a book about classical physics—a name intended to capture the pre-quantum scientific idea, augmented by general relativity. Operationally, it is physics in the limit that Planck's constant h → 0." This seems to very clearly include general relativity in "classical physics". This is not compatible with your statement The sources clearly support the idea that classical physics is nonrelativistic and non-quantum. And however you look at it, the text of the lead of Classical physics does not square with this either. —Quondum 02:01, 4 February 2025 (UTC)

Sorry, I parse the sentence differently. I read "This is a book about classical physics—a name intended to capture the pre-quantum scientific idea" and "This is a book about classical physics augmented by general relativity". The rest of the preface is consistent with the intro to Classical physics. To be sure, general relativity is often described as a "classical" theory because it is has not been quantized and yet it is "modern" in being developed in the revolutionary period of physics. Whittaker's history has Classical Theories and Modern Theories, with general relativity in the latter as another example. This lack of crisp division does not change the use of "modern physics" vs "classical physics". Maybe I read too many histories: I thought these categories were well known. Johnjbarton (talk) 02:44, 4 February 2025 (UTC)

Saying that $\hbar \to 0$ is the classical limit means that general relativity is classical. That's pretty unambiguous. The Misner and Wheeler source given above also includes general relativity within classical physics. Not including relativity under the "classical" umbrella seems less common, but it does happen; see [1][2][3] and arguably [4]. XOR'easter (talk) 03:55, 4 February 2025 (UTC)

@Fgnievinski I have added content to History of physics § Division into classical and modern and reworked the last parts of the Physics § History, then moved and refocused Physics § Distinction between classical and modern physics. Much of this based on input from this discussion. I now believe your original goal of placing "classical" against "modern" to highlight their definitions is covered by the two articles History of physics and Physics. Consider dropping your proposal and restarting one to merge these two articles in Physics which can now be easily accomplished. Johnjbarton (talk) 03:02, 10 February 2025 (UTC)

Thank you for your work. I agree the content and sourcing of the new section History of physics#Division into classical and modern. So your suggestion is to merge both Classical physics and Modern physics into Physics or History of physics? fgnievinski (talk) 02:31, 14 February 2025 (UTC)

Physics. Neither Classical physics nor Modern physics have history. Johnjbarton (talk) 03:15, 14 February 2025 (UTC)

Understood, thank you. I asked because of the new section in History of physics. Anyways, I've taken the liberty of creating Classical and modern physics as a plausible redirect to the corresponding section in Physics. I assume folks who disputed the notability of the two concepts would be pleased with folding the stand-alone articles into a section of an existing article. It's either that or nominating the offending articles for deletion. If the section eventually grows substantially, it could be split off as originally proposed. fgnievinski (talk) 06:02, 14 February 2025 (UTC)

I've dumped everything at Draft:Physics#Core theories, in case anyone wants to have a go at trimming the duplicated material. fgnievinski (talk) 03:05, 18 February 2025 (UTC)

Oppose because in common scientific discourse, the distinction is not between classical and modern. It is between classical and quantum. Aseyhe (talk) 03:35, 21 February 2025 (UTC)

Opposing the merger implies keeping the existing articles on Modern physics and Classical physics as is? fgnievinski (talk) 05:40, 21 February 2025 (UTC)

Modern physics could be merged. The issue with classical physics is that "classical" is also part of a different dichotomy: classical vs quantum. $\hbar \to 0$ is the standard meaning of "classical" in communications among physicists, at least in my field -- in the sense that if I hear "classical" in a talk or read "classical" in a journal article, I know immediately that it means not quantum. Basically, I think we need a page that can be linked when discussing phenomena or methods being classical in the $\hbar \to 0$ sense. Admittedly, the current classical physics page needs some work to clarify the different usages of the term. Aseyhe (talk) 05:59, 21 February 2025 (UTC)

In particular: we have quantum physics, and we have semiclassical physics, and to complete this, we should also have classical physics. Aseyhe (talk) 06:02, 21 February 2025 (UTC)

I see that there is also classical mechanics. It suffers from the same problem as classical physics (in that it says relativity is not classical, which is wrong in a lot of contexts), but perhaps we only need one of the two, and classical physics could redirect to classical mechanics (as is the case with the quantum versions). Aseyhe (talk) 06:06, 21 February 2025 (UTC)

Strongly oppose merge: As some people have said, Classical physics is a well defined category in and of itself; non-quantum physics. It is a term widely used (at least in high energy physics/theoretical physics) to mean that.

Oppose redirect of classical physics to classical mechanics; they are not the same thing. Classical mechanics is a pretty small part of classical physics. The latter is an umbrella term for a LOT of stuff: classical mechanics, electrodynamics, thermodynamics etc. General Relativity is also classical! So that is a very bad idea.

Arguments from "its too short" are (imo) not relevant. Its too short not because it doesnt warrent an article, but rather because noone bothered to write it. The solution is to write the article. If the General Relativity page was short I would say extend it, rather than merge it with Gravity. We should rather come together as a community and make the articles better. Not merge them.

Modern physics on the other hand is a more nebulous term to which I will not comment whether it warrents an article or should rather be a subsection in the physics page, the latter of which I could see as a decent idea. OpenScience709 (talk) 20:00, 7 April 2025 (UTC)

There was a quote in modern physics that used to clearly indicate what it was about, but it got removed. The quote was:

“ The term "modern physics", taken literally, means of course, the sum total of knowledge under the head of present-day physics. In this sense, the physics of 1890 is still modern; very few statements made in a good physics text of 1890 would need to be deleted today as untrue...

On the other hand... there have been enormous advances in physics, and some of these advances have brought into question, or have directly contradicted, certain theories that had seemed to be strongly supported by the experimental evidence.

For example, few, if any physicists in 1890 questioned the wave theory of light. Its triumphs over the old corpuscular theory seemed to be final and complete, particularly after the brilliant experiments of Hertz, in 1887, which demonstrated, beyond doubt, the fundamental soundness of Maxwell's electromagnetic theory of light. And yet... these very experiments of Hertz brought to light a new phenomenon—the photoelectric effect—which played an important part in establishing the quantum theory. The latter theory... is diametrically opposed to the wave theory of light; indeed, the reconciliation of these two theories... was one of the great problems of the first quarter of the twentieth century. ” — F. K. Richtmyer, E. H. Kennard, T. Lauritsen, Introduction to Modern Physics, 5th edition (1955)

Headbomb {t · c · p · b} 04:52, 4 February 2025 (UTC)

References

Modern physics is a well-used term as it is used in many textbooks and physics courses. It comprises anything that includes quantum and/or relativity (SR and/or GR). Classical physics is an odd one in the sense that it refers to physics that it not modern. To me classical mechanics is about mechanics (forces and motion and maybe gravity). Thermodynamical and electrical phenomena that does not need a quantum/relativistic model would be still classical physics but not necessarily classicla mechanics.--ReyHahn (talk) 08:33, 4 February 2025 (UTC)

We have three discussions here

1. Are "modern physics" and "classical physics" notable?
2. What do "modern physics" and "classical physics" mean?
3. Should the articles be merged?

If we could agree to the merge then we would have only one place to work out what sources say the terms mean. As this is a history concept rather than a math or science fact, definition might differ in details. If we find sources, then we will know the topic is notable. Since I am in favor of merge (which could be undone in the future if the amount or character of the content changes) I hope someone will put forward a case against a merge. Johnjbarton (talk) 17:50, 4 February 2025 (UTC)

Indeed, "modern physics" usually is taken as relativity + quantum mechanics: Relativity and Quantum Mechanics: Principles of Modern Physics. Sometimes "modern" is expanded to include statistical thermodynamics: Modern Physics: Introduction to Statistical Mechanics, Relativity, and Quantum Physics. Bear in mind it's almost a century old concept, re: Planck's The Universe In The Light Of Modern Physics (1931). The distinction between modern physics and classical physics seems a notable concept: On the Co‐Creation of Classical and Modern Physics, Worldviews and physicists’ experience of disciplinary change: on the uses of ‘classical’ physics, Relativity, quantum physics and philosophy in the upper secondary curriculum fgnievinski (talk) 02:23, 5 February 2025 (UTC)

Using a quote from a 1955 book to say what "modern" physics is ... that just doesn't sit right. But if we do take it as accurate, then that quote is an argument that we don't need a "modern physics" article at all, and it should just redirect to Physics.

I think that trying to decide what to merge into what before solidly establishing the definition(s) of these terms is putting the cart before the horse. We don't need to agree to the merge in order to have only one place to work out what sources say the terms mean; we have a central spot for discussion right here. XOR'easter (talk) 19:35, 5 February 2025 (UTC)

I'm not sure why it doesn't sit right, the meaning of modern physics hasn't changed since then. As for redirecting to physics, that would be the wrong outcome.

This is an article that concerns terminology and history, and that's how things should be approached. What do the terms mean (and what do they not mean), and how did they arise. Classical physics is whatever we had circa 1890 and before, modern physics comes from incorporating advances from quantum physics and relativity (statistical mechanics are modern to the extent that they incoporate quantum physics in them, i.e. FD and BE statistics, E = hν, etc...). And that taking the limits h → 0 / v/c → 0 often lets you find classical behaviour from modern results. It's also why classical electrodynamics isn't usually considered part of modern physics, while it has relativity built in, it predates 1890 or so.

This is a hugely notable topic that should be treated with the weight it deserves. To this day you have courses in virtually every physics department called Modern Physics that deal with this, and plethoras of textboox on the topic. Headbomb {t · c · p · b} 19:56, 5 February 2025 (UTC)

On the contrary, the 1955 book is exactly the right time frame for a definition of "modern physics". The topic is not "21st century physics". Rather it is a widely used historical term that arose to identify the era of physics which followed the discovery of quantum mechanics and relativity. We already have more than enough sources to establish that. (This is an argument in my mind for a merge: contrasting "classical physics" with "modern physics" will help avoid conflating "modern physics" with "21st century physics"). Johnjbarton (talk) 19:57, 5 February 2025 (UTC)

We can't say that the definition hasn't changed without more recent sources that indicate that the definition hasn't changed. Nothing here so far has convinced me that we need an article called modern physics, rather than a paragraph in Physics explaining the usage of that term. The existence of books or college courses with that as a name doesn't mean that giving it a stand-alone page is the most conceptually clarifying way to present the material encyclopedically. XOR'easter (talk) 20:08, 5 February 2025 (UTC)

Here is some of the table of contents from

• Krane, K. S. (2019). Modern Physics. United Kingdom: Wiley.

1. Some Deficiencies of Classical Physics 1

1.1 Review of Classical Physics 3

1.2 Deficiencies in Classical Concepts of Space and Time 11

1.3 Deficiencies in the Classical Theory of Particle Statistics 13

In a certain sense the meaning of "modern physics" has changed: it has new stuff. But the contrast point with classical has not changed. Johnjbarton (talk) 23:10, 5 February 2025 (UTC)

Let me propose a different version of XOR'easter's suggestion: we could merge Classical physics and Modern physics into a section of Physics and, if it unbalances the article, we can split out Classical and modern physics Johnjbarton (talk) 04:44, 6 February 2025 (UTC)

I agree merging at a section Physics#Classical and modern physics would be a useful first step. Just notice Physics has several pertinent subsections:

• Physics#Classical
• Physics#Modern
• Physics#Classical theory
• Physics#Modern theory
• Physics#Distinction between classical and modern physics

So much for disputable notability! fgnievinski (talk) 02:54, 7 February 2025 (UTC)

A standalone article, with a summary in physics, seems a much better solution. Headbomb {t · c · p · b} 03:03, 7 February 2025 (UTC)

Is there enough to say to warrant a standalone article? I'm finding it hard to see how that would work. XOR'easter (talk) 01:45, 8 February 2025 (UTC)

That doesn't establish notability; that just establishes that the article Physics is badly organized. (Which I guess shouldn't be a surprise. Like every other old article on a broad topic, it's accumulated every passing whim for 20 years, and few if any expert editors have volunteered the time to shape it up.) XOR'easter (talk) 01:47, 8 February 2025 (UTC)

The proposal of a merge into a common section presupposes agreement that they belong together, an idea that has not achieved consensus. Indeed, it makes about as much sense as in a world where all sheep happen to be black, defining blackness as being a sheep. There is an error of semantics. If, around 1900, "modern physics" had been defined as what seemed to be the conception of physics then, we would be chastising them for hubris in retrospect. Just because we can find sources that demonstrate that modern physics currently enbraces quantum physics as mainstream does not allow us to define "modern physics" as quantum physics, for example. Let our failed logic not lead us into the same hubris. And Fgnievinski, pointing to the existence of some sections establishes notability ... how? (Don't answer: the question is rhetorical.) —Quondum 15:00, 8 February 2025 (UTC)

Textbook titles are marketing and branding. Within our grad-student lounge, there are about a dozen different books all named University Physics. Should we infer that their tables of contents define the sum total of all physics that is taught at universities? What we need are sources that say, explicitly, in the text, Modern physics is... and/or Classical physics is.... Then we can summarize those sources and see how much verbiage is due. If reliable sources do not take the time to define what modern physics means, overtly and explicitly, then we don't do that, either. We don't need a section, let alone an article, to say that "modern physics means physics as practiced in the modern age"; that's just putting a noun and an adjective together. XOR'easter (talk) 15:54, 8 February 2025 (UTC)

Right now, Physics says that Classical physics is generally concerned with matter and energy on the normal scale of observation. The term normal here is ... less than precise. More fundamentally, if General relativity is one of the cornerstones of classical physics [5], or if Classical physics is defined as the physics where Planck’s constant can be approximated as zero [6], etc., then we can't exclude GR from the "classical" column. On the other hand, some authors might exclude it, e.g., While general relativity replaces the scalar gravitational potential of classical physics by a symmetric rank-two tensor... [7]. Or, Classical physics assumed that space is immutable and its geometry obeys the Euclidean postulates [8]. Or, Perhaps surprisingly, it will emerge that while in many respects, the nature of time in general relativity is yet further removed from the nature of time in classical physics than it is in special relativity, there are also respects and circumstances relative to which general relativity supports temporal notions closer to those of classical physics than any that can be found in special relativity [9]. We can't just follow our own idiosyncratic preferences here, or pick the first book that comes to hand. XOR'easter (talk) 18:00, 8 February 2025 (UTC)

The significance of the books on "Modern physics" to the topic is derived not from the title, but from the content of their prefaces which specifically address the split we are discussing. I won't say every preface, but many. On the opposite side, I guess books on "University physics" will commonly include topics of we would call classical physics. You might look in their preface for an explanation.

Sources can and so take time to define modern physics, repeatedly referring to the 1900-1910 period. Some of these sources (some taken from this thread) are now cited in our articles.

We should not assert that "modern physics means physics as practiced in the modern age" as that is contrary to many mainstream sources. Johnjbarton (talk) 19:50, 9 February 2025 (UTC)

• Merge but only because the two articles are short, both refer to one-another, and are attempting to illustrate the contrast between the 19th and 20th century. The two articles together, are more about the history of science, rather than distinguishing "what is classical, as opposed to quantum". Distinguishing "classical", "quantum" and "relativity" is a more difficult and arcane discussion. For example: once you start studying e.g. the Standard Model, you eventually realize that half or 2/3rds of it is "classical" in that the definitions of fiber bundles and connections needed for su(3) x su(2) x u(1) require exactly zero quantization (i.e. do not invoke the Weyl algebra for their description.) The Clifford algebra approach to spin, and the construction of Dirac spinors as a product of two Weyl spinors is also 100% "classical": you can build spinors on any Riemannian manifold in any dimension whatsoever, nothing quantum about it; its "just" geometry. Also, curiously, most of relativistic cosmology (wait... why is that a red link???) is "classical" in that you can derive relations like PV=nRT (as needed for e.g. baryon acoustic oscillations) without having to use any general or even special relativity: you can do this using just Newtonian physics i.e. using a "classical" derivation (but you do need Plank/Boltzmann to do it...) The phase-change between 19th and 20th century physics requires a good history article. But this is different from sketching the difference between "classical" topics like geometry and "quantum" topics like deformations of algebras is much more difficult. Worthy of it's own article. 67.198.37.16 (talk) 22:41, 14 March 2025 (UTC)

  Yes and classical field theory is, well, classical. Tree-level calculations of the Standard Model are classical calculations. Spinors are classical objects. But thats because we do have a clear definition of what classical means: Its the $\hbar \rightarrow 0$ limit. It should not be defined in contrast to modern physics and the fact that it is is a problem with the page as currently witten. Not the topic. So again, I oppose merge. The classical physics page is just badly written. Let's rewrite it. OpenScience709 (talk) 20:13, 7 April 2025 (UTC)

Nuclear spin temperature in Orders of magnitude (temperature)

Hi. While I have a scientific background (molecular biology) I am not a physicist so I'd like to understand something. In Orders of magnitude (temperature) one of the entries is relative to a nuclear spin temperature. Does it make sense to include it in the list? I cannot really understand if it is really a "normal" temperature or if it is best treated as another concept that can be described as a temperature in terms of units/thermodynamics but is actually separate (or maybe the question doesn't make sense either). Thanks a lot! cyclopia^speak! 10:29, 24 February 2025 (UTC)

I think it depends on how you look at it. The absolute temperature of a bulk material as a whole, as ordinarily understood, cannot be negative. However some subsystems, like the nuclear spins, can be at negative temperature (and therefore not in thermal equilibrium with the material as a whole). --Trovatore (talk) 19:55, 24 February 2025 (UTC)

Remember that a 'negative' temperature is actual hotter than any positive temperature. It is a population inversion where more states are at a high energy level than at a low energy level. JRSpriggs (talk) 04:00, 27 February 2025 (UTC)

The negative temperature entries do not belong on the scale, IMO. The whole concept seems to be a rather abstract parameter, and is out of place on a scale of "real" temperatures. —Quondum 13:53, 27 February 2025 (UTC)

As well as echoing User_talk:Quondum, I would like to echo User:Trovatore: "The absolute temperature of a bulk material as a whole, as ordinarily understood, cannot be negative. However some subsystems, like the nuclear spins, can be at negative temperature (and therefore not in thermal equilibrium with the material as a whole)." I would emphasize that the subsystems are systems only virtually or metaphorically: they are not thermodynamic systems in themselves, because they are not in thermodynamic equilibrium; it follows that they do not have thermodynamic temperatures as properly defined. Their temperatures are virtual or solely theoretical or analogical.Chjoaygame (talk) 03:36, 28 February 2025 (UTC)

Hmm. I think it's fair to say that, if you take a broad enough view, nothing is in thermodynamic equilibrium. If a subsystem is in approximate equilibrium on a short time scale, it's still reasonable to apply thermodynamic terminology to it. So I'm not sure that negative temperatures are more "metaphorical" than everyday temperatures. As far as I can tell, the whole field of thermodynamics is sort of inherently fuzzy (if I'm wrong about that I'd be curious to know).

That said, I don't have a strong opinion on whether negative temperatures should appear on this particular table. --Trovatore (talk) 05:28, 28 February 2025 (UTC)

It goes a bit far to say "the whole field of thermodynamics is sort of inherently fuzzy." Thermodynamics has a logical structure that is worth understanding. Einstein said of classical thermodynamics that, within its domain of applicability, it is the only area of physics that will never fall. I think that quantum mechanics is something like that too, though I think that Einstein didn't see it as I do.

"if you take a broad enough view, nothing is in thermodynamic equilibrium." True enough, but Einstein did add the modification "within its domain of applicability."

"I'd be curious to know." The basic logic of thermodynamics refers to idealized systems that are in thermodynamic equilibrium. The key idea of thermodynamics is the pair (temperature, entropy). For a closed system (no transfer of matter), this corresponds to the distinction between transfer of energy as heat and as thermodynamic work. You can call it "sort of inherently fuzzy" if you like, but I like it, and I don't find it fuzzy, and it is useful. Its analogue shows up in quantum mechanics as the difference between reversible and irreversible changes of state. The possibility of non-equilibrium thermodynamics is still a twinkle in the eyes of a few physicists; we are waiting for more.Chjoaygame (talk) 04:21, 1 March 2025 (UTC)

As I mentioned on Talk:Orders of magnitude (temperature), the negative temperatures should be clearly separated from the rest of the table. These temperatures are clearly not comparable. If they were simply comparable we would not need a whole bunch of physics papers to address the meaning of negative temperature.

I tried change the table but it seems that someone is guarding it. Johnjbarton (talk) 18:17, 28 February 2025 (UTC)

Should I open an RfC at the article's talk page? –LaundryPizza03 (dc̄) 04:53, 4 March 2025 (UTC)

My understanding of the negative nuclear spin temp controversy is that there was an off-by-one error in the computation of the entropy. If you add one to the count of the number of states, you get a very small but finite positive temp; if you don't, then you get a negative temp. It's a controversy because there are two different ways of counting, which differ by one. ... at least, that's where it stood in "popular media", about a decade ago. I'd tripped over it trying to get a good definition of entropy for the systems I was studying. Which turns out to be very difficult. Which is why its a controversy. ... Was a controversy. Has it cleared? Is there consensus? 67.198.37.16 (talk) 23:05, 14 March 2025 (UTC)

Nonlinear electrodynamics

I recently have been looking for info on nonlinear electrodynamics (NED), and when I clicked on the nonlinear electrodynamics link through the Born-Infeld model wiki page, I was redirected to nonlinear optics, which is obviously not a good redirect. I removed the redirect, but this left an empty page; it does seem to me that there should be a NED page, but I am certainly not qualified to make one. I put a deletion proposal on the page with attached reasoning, but after reading Wikipedia:Deletion_policy and Template:Expert_needed I'm no longer convinced that this was the right thing to do. How can I "request a page" from someone with NED experience (or something along these lines)? Eiis1000 (talk) 21:26, 9 March 2025 (UTC)

I have reverted the change, as the user's method of requesting deletion is entirely against the deletion policy. A redirect like this should be discussed at Redirects for discussion. Jalen Barks (Woof) 21:39, 9 March 2025 (UTC)

Maybe redirect to Born–Infeld model. Xxanthippe (talk) 22:05, 9 March 2025 (UTC).

Thank you for fixing it and showing the right way to resolve the problem! Eiis1000 (talk) 10:34, 10 March 2025 (UTC)

I created an RfD entry for it here.--Srleffler (talk) 22:17, 9 March 2025 (UTC)

Request for comments on Draft:Monolithic active pixel sensor

I have recently created a new page Draft:Monolithic active pixel sensor (my very first one) and I would be glad to get your feedback on the contents. MiljenkoSuljic (talk) 09:10, 12 March 2025 (UTC)

RfC: what next with Electron microscope, an entry page for a range of techniques

I am starting an informal RfC (i.e. not actually going to a full {{RfC}}) on how to proceed with the entry page for a wide range of electron microscope pages. It is not in the greatest of shape, I have been slowly chipping away at it although it still needs work and sources. Please post to Talk:Electron microscope#RfC: what next with this page if this is in your area of interest. Ldm1954 (talk) 19:35, 13 March 2025 (UTC)

Kalusa-Klein pages

Samuel Adrian Antz has recently created several pages all on similar topics:

• Kaluza–Klein metric – Five-dimensional metric
• Kaluza–Klein–Christoffel symbol – Five-dimensional Christoffel symbol
• Kaluza–Klein–Einstein field equations – Five-dimensional Einstein field equations
• Kaluza–Klein–Riemann curvature tensor – Five-dimensional Riemann curvature tensor

There is also an older (2006) page: Kaluza–Klein theory – Unified field theory which is far, far more extensive.

In terms of new page review, are these notable enough by themselves, and is it really appropriate to have them as seperate pages which are somewhat extended definitions? Comments and/or edits welcome. Ldm1954 (talk) 17:45, 21 March 2025 (UTC)

@Ldm1954 Before creating the articles, I have indeed thought about alternatively just expanding Kaluza–Klein theory, but I eventually decided to create own articles for the following two reasons:

• Kaluza–Klein theory doesn't cover plenty of details about the above topics and is already a pretty long article.
• I still plan to extend all four articles with a more detailed calculations. For example, for Kaluza–Klein–Christoffel symbol more about the geodesic equation and for Kaluza–Klein–Riemann curvature tensor more about how the ordinary Riemann curvature tensor, Ricci tensor and Ricci scalar are included. I have already found sources for all of this, but due to different conventions, I first want to go through the calculations by hand myself to verify everything, which will still take a bit of time.

I hope it's acceptable with the latter point. I've already kept fully sourced articles unpublished for more than a year since I still wanted to add details, only to then wonder why since they could have helped others sooner and others could also have helped to expand them. Comments to this are of course also welcome. Thanks for your help! Samuel Adrian Antz (talk) 19:16, 21 March 2025 (UTC)

I strongly recommend collapsing the metric and the Christoffel pages into one. And maybe even the curvature tensor page in with these two. These are effectively just pages on kinematics; they need to use a common, consistent notation. From direct experience, trying to keep notation in sync across different WP articles is a big pain in the butt. Having the field equations in a distinct page is a fine idea; dynamics is clearly distinct from kinematics.

I also strongly recommend adding David Bleeker's book "Gauge Theory and Variational Principles" (1982) Addison Weseley as a reference. The PDF is freely available. It has a particularly clear and elegant derivation of Kaluza-Klien in Chapter 9. I just pulled it off the shelf and looked and snickered to myself -- "clear and elegant", that is, if you read and understood the rest of the book. But no, seriously, it really is quite clear and elegant. The deerivation is in coordinate-free notation, as opposed to the notation you're usig in these new articles. Which is why I recommend collapsing the three kinematics articles into one: it will allow a statement of the same ideas in both coordinate-free, and coordinate notation, a side-by-side comparison. Note that most, even the vast majority of other Wikipedia articles on geometry use coordinate-free notation, so being able to resolve that notational tension in one article is nice (instead of splattering it across three). 67.198.37.16 (talk) 03:48, 22 March 2025 (UTC)

p.s. Another reason to prefer coordinate-free notation is it makes it easier to add a spin structure to the exposition, along the lines of Seiberg-Witten or however it is done these days. Spin structures are cool, they really help simplify and clarify a lot of old physics ideas about spin. (Bleeker, for example, didn't know about them, and thus his tortured exposition of the Dirac eqn.) Don't leave home without it. 67.198.37.16 (talk) 03:59, 22 March 2025 (UTC)

This many articles creates an illusion of importance. The articles use the same sources and should be merged. Johnjbarton (talk) 22:31, 22 March 2025 (UTC)

@Ldm1954 @Johnjbarton (@67.198.37.16 if that works) Given that I already thought about just expanding Kaluza–Klein theory and all of you agree to have a merge, let's continue to discuss how to do that. I'm quite fond of the above idea to merge three of the articles into one about kinematics and have the field equations, the longest article among them, separated. But what would the title of the kinematic article then be? Are there different suggestions? (Also, I'll probably add the changes I mentioned as soon as possible, probably within the next two to three weeks, so that if a merge hasn't happened until then, we'll have a better overview.) Samuel Adrian Antz (talk) 00:28, 24 March 2025 (UTC)

I am abstaining on this; I posted here to get input as I was not comfortable reviewing the pages as part of WP:NPP, they are too far into my oceans of incompetence. Ldm1954 (talk) 00:40, 24 March 2025 (UTC)

Perhaps we should continue this on Talk:Kaluza–Klein theory. In my opinion the first priority should be to improve that core article. To be honest, the level of detail in the newly added articles isn't really appropriate for Wikipedia. Any reader interested in this level will seek out text book. What is much more important is to relate the concepts to other topics in Wikipedia. The easy navigation across a large web of related material is where Wikipedia shines. Johnjbarton (talk) 01:04, 24 March 2025 (UTC)

I am out of my depth on the detail, and will not start a discussion on the talk page. I will however, add my support to Johnjbarton's perspective here in terms of what does and does not belong on WP. We should take care to avoid text-book-like material. For a topic such as this, which is not very active, one should start questioning whether anything that does not fit reasonably into the main article should be there. —Quondum 14:05, 28 March 2025 (UTC)

Firsly: The articles really do not need to exist as distinct articles. Each one of them is just one of the objects from the classic Kaluza-Klein theory, titled as "Kaluza-Klein"+Insert object name here. They are not notable in and of themselves as distinct entities from the theory. This is an important distinction. For example, Chern–Simons theory is a theory which is notable. The Chern–Simons form is a specific p-form which was originally formulated in the theory, but now refers to a wider class of things used in far more places and so is notable in and of itself. This is not the case with any of the four articles created.

Secondly: Part of the problem is that "Kaluza-Klein theory" can refer to two things; one is the original proposal by Kaluza and Klein of compactification of a 5D spacetime on a circle. But these days it also refers more generally to any compactification procedure and the effective theory that results from it. I was annoyed about this issue in the past but didn't have time to solve it.

Thirdly: What to do? We need a dedicated article on the original KK theory 5D -> 4D. These four articles would just provide information into that (although like the Riemann tensor and Christoffel symbols are a bit irrelevant I would say). Then we need a parent article concerning KK theories generally. We could have compactification (physics) be that since that is really just another name for this (although gramatically used differently; one is a theory, the other more a procedure).

Actually yeah. I think thats the best solution. Make compactification a main parent article (since there is A LOT to be said about it; it should really be an entire category. I haven't gotten around to writing articles in that area yet :|). Move any irrelevant info from KK theory article there, and make KK theory article mainly deal with the original 5D->4D theory. And move the (notable) info from the 4 KK articles into the KK theory article OpenScience709 (talk) 19:47, 7 April 2025 (UTC)

Possible COI editing on Chaos theory and Lorenz system

I posted a topic on possible COI editing on WP:WikiProject Mathematics over here. If anybody could contribute to this discussion, that would be a big help. Truthnope (talk) 23:40, 24 March 2025 (UTC)

Please post your comments on the content of Chaos theory in Talk:Chaos theory. I know the math project likes to have big discussion on the project page but not so other Wiki projects. Johnjbarton (talk) 15:28, 27 March 2025 (UTC)

Category:Hypothetical processes has been nominated for discussion

Category:Hypothetical processes has been nominated for possible deletion, merging, or renaming. A discussion is taking place to decide whether it complies with the categorization guidelines. If you would like to participate in the discussion, you are invited to add your comments at the category's entry on the categories for discussion page. Thank you.

Expert input is requested from participants regarding the best way to organize Category:Hypotheses. –LaundryPizza03 (dc̄) 05:52, 27 March 2025 (UTC)

Good article reassessment for Weak interaction

Weak interaction has been nominated for a good article reassessment. If you are interested in the discussion, please participate by adding your comments to the reassessment page. If concerns are not addressed during the review period, the good article status may be removed from the article. Onegreatjoke (talk) 22:54, 28 March 2025 (UTC)

Kinetic term

This interesting stub has been unsourced for 15 years. Can somebody please add reliable sources to this? Thanks in advance. Bearian (talk) 02:07, 30 March 2025 (UTC)

I applied WP:PROD, this is not a thing. Johnjbarton (talk) 03:33, 30 March 2025 (UTC)

Definitely not a thing.--ReyHahn (talk) 08:16, 30 March 2025 (UTC)

Ok. Bearian (talk) 01:45, 31 March 2025 (UTC)

• There are some articles linking to it, some of those articles should be reviewed or have links redirected to kinetic energy.--ReyHahn (talk) 15:08, 2 April 2025 (UTC)

The PROD succeeded but I asked that it be restored after @OpenScience709 pointed to a reliable source that, among other things says "We do not usually talk about kinetic and potential energy in quantum field theory. Instead we talk about kinetic terms and then about interactions, ...". So evidently within quantum field theory this is a thing.

So far I am not convinced that this is a topic that deserves a full page so I have proposed to merge it into Lagrangian (field theory). Johnjbarton (talk) 23:47, 6 April 2025 (UTC)

I'm a bit bemused that you are going to that trouble. The term has no clear standalone meaning, and as such there should never have been a page with that title. However, merging it as you propose makes sense. —Quondum 00:01, 7 April 2025 (UTC)

Well I don't know enough about QFT to be sure so I wanted to let the process run. Johnjbarton (talk) 01:05, 7 April 2025 (UTC)

Yeah it does have standalone meaning as "the set of terms formed from bilinears of fields, usually excluding the mass terms". OpenScience709 (talk) 05:41, 7 April 2025 (UTC)

OpenScience709, "standalone in a niche field", perhaps. Bilinears of fields include all the things that we call energy, stress and momentum, for example. "Usually excluding the mass terms" is useless. It is not a topic that anyone not in that niche field could be expected to recognize. Your definition doesn't even make sense. Your have not provided any sourcing in the face of no-one confirming your claim, which suggests that you might be in WP:SYNTH territory. If the average physicist from any field does not react with "I know exactly that term means", it is not a good candidate as an article title. I suggest that you get some direct support from people in this forum to show that you are not pushing your own conceptions. —Quondum 16:00, 7 April 2025 (UTC)

@Quondum Uhm. A physicits from a certain field will not know "exactly" what each term means in all other areas of physics... They will know their own area, and some general physics. That's about it.

But as for the accusation of WP:SYNTH or "pushing my own conceptions": M.D. Schwartz in Quantum Field Theory and the Standard Model states the following on pages 30-31: "We do not usually talk about kinetic and potential energy in quantum field theory. Instead we talk about kinetic terms and then about interactions, for reasons that will become clear after we have done a few calculations. Kinetic terms are bilinear, meaning they have exactly two fields." "Anything with just two fields of the same or different type can be called a kinetic term. The kinetic terms tell you about the free (non-interacting) behavior. Fields with kinetic terms are said to be dynamical or propagating. More precisely, a field should have time derivatives in its kinetic term to be dynamical. It is also sometimes useful to think of a mass term, such as $m^{2}\phi ^{2}$, as an interaction rather than a kinetic term".

Kinetic terms are mentioned and used in pretty much all QFT textbooks. Anyone who studied QFT would have encountered kinetic terms. Thats not a niche requirement. OpenScience709 (talk) 16:46, 7 April 2025 (UTC)

QFT is a niche field in WP. Even as far as most physicists are concerned, it could be regarded as niche. Very few physicist that have no insight into QFT would even be able to determine what area of physic was being referred to when "kinetic term" is mentioned. Also that these "are a reasonably wide range of things" violates the guideline WP:NOTDICT: an article is about a specific concept, not a range of things that happen to share a name. Anyhow, we have established that you consider the term to be specific to QFT. It strikes me that authors (including Schwartz) will use terms like this and define these as they go for use in their text; this does not make these terms into candidates for standalone definitions in WP. Even your quotations are fuzzy: characterizations, not definitions. It seems from your quotes that what is being gotten at is the decomposition of a bilinear expression into so-called kinetic and interaction summands. This decomposition would appear to be for convenience in a text or discussion; I would also guess that this decomposition cannot be done canonically. If this decomposition is "a thing", then the title would not be "Kinetic term". —Quondum 17:24, 7 April 2025 (UTC)

@Quondum Ok then whats your point. There are many, many Wikipedia articles on physics that a physicists couldnt place from the title alone unless they happen to be an expert in that area or one closely related to it.

Again, kinetic terms are a specific concept. One that is WIDELY used to refer to the exact same class of terms. Schwartz isnt using this ad hoc as you seem to imply. The definition also isn't fuzzy.

Here is a very incomplete list of textbooks that explicitly use the term "kinetic term" to refer to the exact same type of Langrangian terms:

• QFT by Peskin and Schroeder (considered the go-to QFT textbook, along with the more recent Schwartz)
• QFT by Srednicki
• Classical Field Theory by Nastaste
• A Modern Introduction to Quantum Field Theory by Maggorie
• QFT lecture notes by David Tong (basically the go-to lecture notes on QFT)

The third QFT classic, by Weinberg, doesnt explicitly call them kinetic terms, but thats cause Weinberg is generally notationally clunky and a bit dated (but still excellent content-wise).

Your claim that "kinetic term" is an ad hoc definition that is ill defined doesn't make much sense from how widely it is used (but not defined since it is standard terminology) in academic papers. Just have a look on arXiv and look for papers with "kinetic term" in them. They are all refering to the exact same thing. 85 of them have it in the title alone (again they refer to the exact same concept). Lets compare that to papers having "kinetic energy" in the title which is 476. So this is SO WIDELY USED that its only 6 times less common than literally kinetic energy. It is a crude measure yes. But it does indicate something. OpenScience709 (talk) 17:48, 7 April 2025 (UTC)

I do not find that we are able to communicate in a productive way, so I'll leave you to your own perceptions. I will simply reiterate that editing WP is a collaborative exercise, and hopefully you will seek a consensus. —Quondum 21:13, 7 April 2025 (UTC)

How to write standalone math formulas

I was recently called out by an user for writing equations using a colon as ":<math>E=mc^2</math>" as in

$E=mc^{2}$,

however the suggested method per MOS:INDENT and WP:FORMULA is to write in as "<math display="block">E=mc^2</math>" no colon, as in

$$E=mc^{2}$$,

which includes two additional line breaks. I have issues with the recommended case because it sometimes throws the comma outside the equation into a new line (depending on the app), it gives trouble with the visual editor and the spacing is inconsistent (for example in mobile it is not indented). What's the best practice here? I am told that the colon version breaks html codes but I have never seen that issue. Also the colon version is used almost everywhere. Should I raise this issue to WP:MOS?--ReyHahn (talk) 08:11, 7 April 2025 (UTC)

Please do. I'm definitely not going to start writing "<math display="block">E=mc^2</math>". It ruins both punctuation and alignment, and moreover is more inconvenient to type than ":<math>E=mc^2</math>". Tercer (talk) 09:53, 7 April 2025 (UTC)

I too have once been "called out" once about this a while back. I see that it is mentioned as producing "invalid HTML" at MOS:MATH#Using_LaTeX_markup, but it is used extensively without any drive to reformat all pages that use it. <math display="block"> has its own problems (irksome line spacing, as well as browser-dependent line breaking before and after it, e.g., on Brave, it simply merges inline with the adjacent lines). Looking at MOS:INDENTGAP, it is the colon's use for indentation generally that is the problem, unrelated to line content, so to make any sense, one would have to eliminate colon indentation everywhere. In any event, if it produces broken markup, this should be fixed by the wiki processing, not by arcane rules for workarounds of problems. Apologies for the rant, but AFAICT the case against moving away from colon-indentation of LaTeX is pretty solid. —Quondum 16:36, 7 April 2025 (UTC)

Our pages should adopt the same approach used in the rest of Wikipedia.

This week the display block feature has been altered by a software change in MediaWiki. So any examples or comparisons done since last Thursday should be disregarded. Johnjbarton (talk) 18:15, 7 April 2025 (UTC)

Green's function: dimensional inconsistencies and wrong scaling

See here. Aldiviva (talk) 14:04, 7 April 2025 (UTC)