Wikipedia talk:WikiProject Physics/Archive December 2021

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Poynting's theorem

I had a go at cleaning this one up. It still needs some work, but I clarified some text, replaced the tortured derivation with a slightly less tortured one following Jackson, and got rid of an overly technical section at the bottom which didn't seem necessary or sufficiently sourced. I'd appreciate a second pair of eyes, since I haven't actually used this stuff directly in a long time. PianoDan (talk) 22:43, 3 December 2021 (UTC)

@PianoDan: The definition and derivation are certainly clear, but will need inline citations. Poynting's theorem#Alternative forms should have a second copy of Ref. 6; I'll correct this now. –LaundryPizza03 (d c̄) 01:46, 4 December 2021 (UTC)

Are inline citations required for things like vector identities that are found elsewhere on Wikipedia? This is the first derivation I've put up, so I'm not sure where you need external references, and where you can just point to the entry for, say, Faraday's Law. Thanks! PianoDan (talk) 15:56, 4 December 2021 (UTC)

Cheerios Effect

Had a whack at cleaning this article up. It's still got loads of room for improvement, and could do with a better illustration, but I think it's OK to pull the maintenance tag at this point. PianoDan (talk) 23:27, 6 December 2021 (UTC)

Italics on jargon

In Wikipedia:Manual_of_Style/Text_formatting#Words_as_words, more specifically in MOS:TERM, it says:

A technical or other jargon term being introduced is often being mentioned as a word rather than (or in addition to) playing its normal grammatical role; if so, it should be italicized or quoted, usually the former. The first occurrence of a technical term should also usually be linked if the term has its own article (or section, or glossary entry) corresponding exactly to the meaning when used in the present article.

I was wondering about the threshold of technicality for considering a term commonplace or jargon in physics? For example, should each term in Glossary of physics be formatted in italics upon first occurrence in every physics article? Maybe exclude terms in the List of physics concepts in primary and secondary education curricula?

For example, take the lead sentence in the article about Interferometry:

"Interferometry is a technique in which waves are superimposed to cause the phenomenon of interference, which is used to extract information."

My inclination would be to add italics around "interference", perhaps also in "superimposed". How would you interpret MOS:TERM for physics articles? I remind colleagues that WP:MOS is not a strict policy, it's a guideline: "best practices supported by consensus. Editors should attempt to follow guidelines, though they are best treated with common sense, and occasional exceptions may apply." Thank you for your thoughts. fgnievinski (talk) 04:23, 6 December 2021 (UTC)

The question here is are you using words as words, or are you using them as regular terms? It's the difference between "The velocity of the car is 10 m/s" and "The word velocity, from the latin velocitas, indicates the ratio of distance traveled per interval of time." Headbomb {t · c · p · b} 06:35, 6 December 2021 (UTC)

The difficulty is when the usage of WP:WORDSASWORDS is not signaled so clearly. For example, if you remove "the word" from your second example, would you still italicize "velocity"? If so, does that imply adopting both italics and boldface (or italics and double quotes, as given at the end of MOS:TERM) in the lead sentence of all articles defining a term or concept in physics -- for example, would you recommended doing so in the article about Velocity? fgnievinski (talk) 15:23, 6 December 2021 (UTC)

Returning to the original example, in which terms seem to be mentioned instead of simply used (and they're not defined either): would you italicize "interference" in the lead sentence of the article about Interferometry? Here's another example, from Velocity:

The scalar absolute value (magnitude) of velocity is called speed... If there is a change in speed, direction or both, then the object has a changing velocity and is said to be undergoing an acceleration.

Can we distill clearer guidelines and examples for the application of MOS:TERM in physics? I'm concerned its literal application might result in overemphasis if all key terms mentioned in an article lead section are highlighted. fgnievinski (talk) 15:23, 6 December 2021 (UTC)

I think part of the problem with that example sentence in Interferometry is that it's just... not a great sentence. The word "interference" is entirely superfluous the way that sentence is currently structured, which is bad because you'd expect the word that interferometry is derived from to do a bit more heavy lifting in defining the term.

Interferometry is a technique which uses the interference of superimposed waves to extract information.

I just updated the page to the above - As it's structured now, I think that it fits the WP:WORDSASWORDS example of panorama/panning almost exactly. I'm a bit confused by your question on the second example - are you saying that that example uses the italicization correctly as described in WP:MOS? If so: I agree - but if it was phrased

then the object is said to be undergoing an acceleration

, it would be more clear that the word acceleration is being defined here and should be italicized ( I just updated that one too). In both cases, I think the cause for confusion is the poor style of English that plagues a lot of physics literature (i.e. not just a wiki problem) - if it's not clear from a given sentence which words are being defined or otherwise being used as WP:WORDSASWORDS, it's just a bad sentence and should be rewritten, not a physics-specific jargon issue. - car chasm (talk) 02:56, 7 December 2021 (UTC)

My usual practice on Wikipedia is to italicize new terms being introduced only if they are not linked. Putting a term that is already blue and underlined in italics just to emphasize it seems excessive.--Srleffler (talk) 02:13, 7 December 2021 (UTC)

Beta Decay Transition

I'm thinking about attacking this one next, but before I start working on it, I wanted to ask - do we think this is even the best name or location for this information? The creator of the page seemed to want somewhere to discuss the difference between Fermi and Gamow-Teller transitions in beta decay. Is having a page titled "Beta decay transition" the best way to do that? Should there instead be one page each for the two types? Should this information (or some subset) just be on the main "Beta Decay" page? Or some other configuration I'm not thinking of? What are folks' thoughts on the best place to put this stuff? PianoDan (talk) 19:11, 7 December 2021 (UTC)

There's some prior discussion of the article structure here: Talk:Beta_decay#Types_of_beta-decay_transitions PianoDan (talk) 19:25, 7 December 2021 (UTC)

Optical Unit

Had a go at this one. I think it's as good as it's going to get at this point - although I do find these units used quite a bit in the literature, there's not much by way of discussion of the units themselves. I asked a question about the future of the article on its talk page. PianoDan (talk) 21:07, 9 December 2021 (UTC)

Cauchy stress tensor page may have component indexes swapped

The wikipedia Cauchy_stress_tensor page includes many examples of:

\quad T_{j}^{(n)}=\sigma _{ij}n_{i}

Here the tensor has an index that is the second of the component indexes (in this case $j$ ) whereas in other literature I see the tensor uses the first of the component indexes ( $i$ ) so that the tensor is shown as:

\quad T_{i}^{(n)}=\sigma _{ij}n_{j}

(note the index of the unit vector

n

changes to

j

)

Similarly, the first diagram on the page (shown below) has the same problem where I would expect the components of $T_{1}$ to be $\sigma _{11}$ , $\sigma _{21}$ and $\sigma _{31}$ and not $\sigma _{11}$ , $\sigma _{12}$ & $\sigma _{13}$ .

I think the diagram could also be improved by showing the unit vectors as $n_{1}$ , $n_{2}$ & $n_{3}$ instead of $e_{1}$ , $e_{2}$ & $e_{3}$

A similar diagram on the main tensor page seems to have the component indexes shown in the way that I would expect.

References:

ocw.mit.edu marine-hydrodynamics lecture-notes (section 1.7.2)

auckland.ac.nz Cauchy_Stress_Tensor (equation 3.3.4) — Preceding unsigned comment added by ParticleHorizon (talk • contribs) 13:27, 12 December 2021 (UTC)

Ideas to clean up atomic orbitals and add a new page

Hello all, I am a new contributor here at Wikipedia.

I have been interested in cleaning up and condensing the information about Hydrogen orbitals for sometime and I have started to put some work towards it. Right now there are at least 3 pages with information on Hydrogen orbitals: Atomic orbital, Hydrogen Atom, and Hydrogen-like atom. The expression for the ideal, non-relativistic hydrogen atom appears on two of these pages, and visualization and discussion of atomic orbitals appears on all of these. Some of the information is redundant, and some of the information is unique. Some information is missing such as a clear authoritative comparison of complex and real orbitals and a short *general* discussion of the relationship between quantum numbers and the shapes of both real and complex orbitals. One final issue. On the pages with the expression for the wavefunction there seems to be a continuous edit war regarding a convention choice for the definition of the Laguerre polynomial.

I propose a new page to address all of these problems. The page would be a gallery of atomic orbitals. It would be focused on the solution to the Schrodinger equation for they hydrogen atom. The formula for the solution will appear at the top of the page along with a discussion of the quantum numbers and how they effect the geometry of the solutions. There will be a clear discussion of the complex and real solutions to the Schrodinger equation and the relationships between them.

Finally, the main purpose of the page will be to hold a large number of visualizations of atomic orbitals. There can be a discussion of different visualization techniques and then tables of a large number of orbitals. This serves a number of purposes. (1) visualization of a large number of atomic orbitals will allow readers to learn about and predict patterns within atomic orbitals (2) The other pages with similar information may be able to offload some visualization to the page to saves space on their page for more article-specific content. (3) The visualizations can appear unburdened by any need of brevity to fit within another article.

I have already drafted a version of this page using code I have developed to generate these visualizations. See the page here: Draft:Gallery of Atomic Orbitals. I would deeply appreciate any feedback anyone has on this overall project and the specific draft page. So far I have focused on this new page. I imagine a next step would be cleanup of the existing pages.

Thanks for any responses! I am very excited to be joining this community!

Twistar48 (talk) 16:06, 12 December 2021 (UTC)

Thanks for being pro-active about improving Wikipedia! If you haven't already, I'd make sure to carefully check this against WP:MOS and WP:GALLERY. Gallery pages are generally discouraged, but this might be an exception.

In terms of the page content, I don't think it's correct to use references as part of a sentence, for example: ".. the solutions are given by ^[1][2][3]." You should try to make all of the text complete sentences.

I'd also think carefully about the difference in writing style between an encyclopedia article and lecture notes or a text book. PianoDan (talk) 19:56, 13 December 2021 (UTC)

@PianoDan: Thank you very much for your feedback! I will make the editorial changes you suggest and work to make the article compliant with WP:MOS. I also appreciate the feedback about encyclopedia writing style vs lecture/textbook. The latter is more natural for me and I have more experience with it. I will work on the article's style.

Specific feedback about content of the article and how it compares/contrasts to that in other articles would be appreciated as well. I think there is some overlap between this article and others, but I strive to make this article focused and concise, while I feel some of the other articles have ballooned a bit to cover a wide range of topics in ways that themselves already have some redundancies. Twistar48 (talk) 06:17, 15 December 2021 (UTC)

Wikipedia:Articles for deletion/Enzo Tonti

This deletion discussion may be of interest to the community here. XOR'easter (talk) 03:20, 16 December 2021 (UTC)

Dark energy

IP users at this page keep asserting, without a source, that dark energy, particularly the cosmological constant version, violates conservation of energy because the total amount of it increases as space expands. No article in Category:Dark energy seems to discuss this apparent paradox. How do academic sources resolve it? –LaundryPizza03 (d c̄) 06:39, 14 December 2021 (UTC)

There may be problems with defining total energy in the general theory of relativity. Wiser counsel needed. Xxanthippe (talk) 08:34, 14 December 2021 (UTC).

This is a perennial controversy in general relativity. If you define energy from the usual stress–energy tensor, then it is not conserved. A pair of orbiting black holes will lose energy by emitting gravitational waves and eventually collide. This is well-established experimentally. Now, personally I find it silly to call this a violation of conservation of energy, because it clearly went to the gravitational waves, and in fact one extracts energy from them when you detect them with LIGO. The problem is that it's really not easy to define the energy of the gravitational radiation. The usual way is with a stress–energy–momentum pseudotensor, which is not a tensor, but a pseudotensor, which is not covariant, and leads to all sorts of trouble. If you can stomach that, then energy is conserved. The venerable Physics FAQ explains it well. Tercer (talk) 09:36, 14 December 2021 (UTC)

See the section Friedmann–Lemaître–Robertson–Walker metric#Cosmological constant and the immediately following section Friedmann–Lemaître–Robertson–Walker metric#Newtonian interpretation. The dark energy increases due to the work done by the expansion of the universe against the tension which pervades space. Since the universe is infinite, it makes no sense to talk about the total energy of the universe. The conservation of energy makes sense only when applied to a finite region (whether constant in size or expanding does not matter). JRSpriggs (talk) 21:05, 14 December 2021 (UTC)

Another way to look at it is: the increase in positive energy (dark energy) is balanced by the increase in negative energy (gravitational potential energy). JRSpriggs (talk) 21:26, 14 December 2021 (UTC)

Okay, until a source is found that specifically discusses this notion of energy conservation in GR with regards to dark energy, I've created an FAQ on the talk page. Does it make sense, and should it have ref tags? It would be best to ensure that WP:OR is not violated here. Are there any other FAQs that you think should be clarified w.r.t. this topic? –LaundryPizza03 (d c̄) 08:02, 16 December 2021 (UTC)

Number states

Would someone from the project please look at Draft:Number states and make a recommendation? DGG ( talk ) 06:36, 15 December 2021 (UTC)

I don't see a problem in principle with having an article specifically about photonic number states. However, the draft is pretty bad, and the material it contains duplicates what we already have at Fock state and quantum harmonic oscillator. I would delete the draft and redirect it to Fock state. Tercer (talk) 10:36, 15 December 2021 (UTC)

Agree. WP:Nottextbook. Xxanthippe (talk) 21:46, 15 December 2021 (UTC).

done. DGG ( talk ) 07:31, 18 December 2021 (UTC)

"Algebra of physical space"

These appear to be rather grandiose portrayals of some rather marginal ideas in the geometric algebra tradition:

Algebra of physical space (edit | talk | history | links | watch | logs)
Dirac equation in the algebra of physical space (edit | talk | history | links | watch | logs)

Thoughts? XOR'easter (talk) 17:52, 17 December 2021 (UTC)

Also this:

Spacetime algebra (edit | talk | history | links | watch | logs)

It seems like we have more pages than strictly necessary devoted to something that's never really caught on. XOR'easter (talk) 17:52, 18 December 2021 (UTC)

A quick investigation shows that these pages were mostly written by the SPAs Rcabrera, Cabrer7, 137.207.80.65 (talk), and 24.57.20.112 (talk), which are all operated by the same person. I'm not in the mood of cleaning up this mess, though. An easy thing to do would be to redirect Dirac equation in the algebra of physical space to Algebra of physical space. Tercer (talk) 13:30, 19 December 2021 (UTC)

That seems like a good first step, at least. Duly redirected. XOR'easter (talk) 03:48, 20 December 2021 (UTC)

Multiphysics

The page Multiphysics could stand some attention. It seems to be what happens when you leave different usages of a buzzword together in the fridge for too long. XOR'easter (talk) 22:33, 24 December 2021 (UTC)

Dear lord. That's.... quite something. It's a shame it's probably a notable concept, because AfD would be so much easier than riding a lawnmower into THAT thicket. I'll give it some thought next week after the holiday. PianoDan (talk) 22:42, 24 December 2021 (UTC)

Should it perhaps be renamed multiphysics analysis or multiphysics simulation to narrow the topic and clarify the scope?--Srleffler (talk) 03:41, 25 December 2021 (UTC)

I could get on on board with that, depending on what the references support. PianoDan (talk) 16:04, 25 December 2021 (UTC)

Yes, that sounds reasonable. XOR'easter (talk) 16:33, 25 December 2021 (UTC)

Here's a draft: User:PianoDan/sandbox Got rid of all the meaningless doublespeak, and there wasn't THAT much left. It could certainly be expanded, but for now, this strikes me as more encyclopedic. Any major concerns before I put it back in article space? @XOR'easter:, @Srleffler:? PianoDan (talk) 22:53, 28 December 2021 (UTC)

Looks good to me. The references need work (it looks like the arXiv item might have been published formally later [1]), but fixes like that can be done in mainspace. XOR'easter (talk) 22:58, 28 December 2021 (UTC)

Looks good.--Srleffler (talk) 03:55, 29 December 2021 (UTC)

OK, I've brought the short version back over to mainspace, moved the page to multiphysics simulation, and done some additional cleanup. XOR'easter (talk) 04:44, 29 December 2021 (UTC)

Thanks! PianoDan (talk) 17:20, 29 December 2021 (UTC)

Digital philosophy

The page Digital philosophy (despite the name, mostly about fringe universe-as-computer speculations) had been in a bad state with no efforts to improve it months after being tagged, so I went ahead with the Gordian-knot approach. Further suggestions on what to do with it are welcome. XOR'easter (talk) 18:13, 28 December 2021 (UTC)

Srleffler, your changes look good. Thanks. XOR'easter (talk) 19:32, 28 December 2021 (UTC)

It seems that the more popular name for use of computers in philosophy is computational philosophy; for instance there is an SEP article on Computational Philosophy that looks like it includes the use of computers to investigate the network models of philosophy mentioned in Digital philosophy. It may be best to merge this article into the computational philosophy article. --{{u|Mark viking}} {Talk} 19:37, 28 December 2021 (UTC)

That's not a bad idea; thanks for the suggestion. XOR'easter (talk) 21:00, 28 December 2021 (UTC)

I proposed the merger on the page. While I was at it, I also proposed merging Digital physics into Simulation hypothesis.--Srleffler (talk) 21:23, 28 December 2021 (UTC)

I ended up pruning the physics section of Simulation hypothesis quite a bit. It appears to have been original research by a single-purpose account.--Srleffler (talk) 22:08, 28 December 2021 (UTC)

An entertaining old quote I found: In many respects this point of view may be nothing more than a result of the fact that the notion of computation is the disease of our age—everywhere we look today we see examples of computers, computation, and information theory and thus we extrapolate this to our laws of physics. Indeed, thinking about computing as arising from faulty components, it seems as if the abstraction that uses perfectly operating computers is unlikely to exist as anything but a platonic ideal. Another critique of such a point of view is that there is no evidence for the kind of digitization that characterizes computers nor are there any predictions made by those who advocate such a view that have been experimentally confirmed. [2] XOR'easter (talk) 22:50, 28 December 2021 (UTC)

It reminds me of how in the steam age they conceptualized lots of things as being like steam engines. We are all prisoners of our time.--Srleffler (talk) 18:31, 29 December 2021 (UTC)

The word "digital" implies the Turing machine, which has a finite set of states and a finite set of state transitions (and an infinite tape). This is in contrast to quantum computers, which have an uncountable number of state transitions (an uncountable number of operator (mathematics)) acting on an uncountable space (complex projective space, in the case of QM), organized into finite-length strings of operations applied in sequence. There is no "tape"; the no-cloning theorem implies that there cannot be a tape. In summary: we can have "computers" that are not "digital", and conflating the two concepts leads to popular misconceptions and confusions. We may live in a simulation, but the simulation hypothesis does not suggest that it is digital. 67.198.37.16 (talk) 17:57, 30 December 2021 (UTC)

I imagine most editors here understand this. Digital physics is a really stupid idea, but it appears to be a notable stupid idea.--Srleffler (talk) 04:35, 31 December 2021 (UTC)

Actually, quantum mechanics is no counterexample. One just needs to use a quantum Turing machine instead of a classical one. It seems a really deep fact of Nature that all of physics can be efficiently simulated with a universal digital quantum computer. In principle one might need the continuum, or a non-programmable computer. Tercer (talk) 18:52, 31 December 2021 (UTC)

It seems a really deep fact of Nature that all of physics can be efficiently simulated with a totally imaginary device, that we imagine to be capable of simulating all of physics.--Srleffler (talk) 23:33, 31 December 2021 (UTC)

Nothing imaginary about quantum computers, the theory is clear that they are possible and good prototypes already exist. Tercer (talk) 23:35, 31 December 2021 (UTC)