Wikipedia talk:WikiProject Physics/Archive February 2018

Meissner effect vs Shubikov states

An IP has pointed out that the images in Meissner effect, the ones with a levitating magnet, are not consequence of this effect but mostly due to vortex lines and type II superconductors [1]. I don't know enough about superconductors to be sure that Meissner it is not related. Does anyone here know something about this phenomena? --MaoGo (talk) 15:42, 2 February 2018 (UTC) If you take a look into the talk page of Meissner effect, you'll see it is a recurrent dilemma between the definitions of superdiamagnetism and Meissner, and flux pinning levitation and Meissner levitation. --MaoGo (talk) 16:54, 2 February 2018 (UTC)

Most superconductors show some degree of Meissner effect, that is a partial expulsion of magnetic field, if the magnetic field is below the critical value. For Type II that critical value is really low, so flux lines are usually present in the material. The pinning of flux lines is also a result of the Meissner effect; flux lines penetrate some regions and are excluded from others. So the repulsion producing the levitation does come from the Meissner effect. But the stable levitation, so that the magnet doesn't slide off the superconductor, comes from flux pinning, for example, as modeled in [2]. It would be good to explain this in the article. Alternatively, if we had a picture of a magnet floating above a type I superconducting material below the critical field, that is more of a pure Meissner effect, in that almost all the magnetic flux is pinned outside the superconductor. Such demonstrations need to be in a bowl, so the magnet doesn't slide off. --Mark viking (talk) 19:16, 2 February 2018 (UTC)

Wikipedia:Village_pump_(policy)#Rfc:_Change_default_<math>_to_be_inline

Please comment on the proposal. Thank you for your attention.--Debenben (talk) 23:06, 6 February 2018 (UTC)

Article Quantum foam

https://wiki.riteme.site/wiki/Quantum_foam

The article is misleading. First it contains a lot of falsehoods (the way the Heisenberg uncertainty principle is cited, the way virtual particles are claimed to be actual particles, the way the Casimir effect is cited as supporting this, when it's entirely explained by quantum electrodynamics, ...), secondly it gives the impression that this is part of the current understanding in modern physics, rather than a historical idea. It needs some serious reworking (ie rescue what's relevant regarding the keyword "quantum foam", remove all the "factoids" that have been added mixing it with "ordinary vacuum fluctuations" (or better the vacuum state in quantum field theories), and have a much shorter article or outright delete it if it turns out too little relevant information is left.) 92.196.78.139 (talk) 12:58, 9 February 2018 (UTC)

I made some edits. It could use more work, though. XOR'easter (talk) 17:58, 9 February 2018 (UTC)

Thanks for pointing out the problems. In what sense is it historical? Experimental evidence sets limits, but we don't yet have a good theory of quantum gravity that explains this away these fluctuations. Such fluctuations still exist in some string theories of spacetime, e.g., [3]. --Mark viking (talk) 18:33, 9 February 2018 (UTC)

Jean-Pierre Petit

Over at the Fringe Theories Noticeboard, there's a bit of chatter about Jean-Pierre Petit, a "French astrophysicist/cosmologist with a section of fringe and conspiracy views that are not explicitly identified as fringe or conspiracy". It's also incredibly promotional about obscure and grandiose cosmological speculations, and suffers pretty badly on the grammatical side. (When I say "obscure", I mean that the paper which the article promotes has received a grand total of 13 citations by the incredibly permissive standards of Google Scholar. Only 3 of those 13 are not self-citations, and 2 of those appear to be duplicates. The article even admits, "Despite being peer reviewed, this non-standard cosmological model has not triggered much interest in the scientific community throughout the years".) XOR'easter (talk) 23:59, 11 February 2018 (UTC)

Real number#In physics

What about the "slow motion edit warring" at Real number#In physics? "This approach removes the real number system from its foundational role in physics", really? Boris Tsirelson (talk) 19:13, 12 February 2018 (UTC)

Yeah, I've seen all sorts of speculations about how the real numbers might be only approximately valid, but it's all just, well, speculations. I'd be fine with removing that whole paragraph. XOR'easter (talk) 22:59, 12 February 2018 (UTC)

I replied at Talk:Real_number#In_physics...or_not?. --Mark viking (talk) 23:37, 12 February 2018 (UTC)

Paradox of radiation of charged particles in a gravitational field

This physical paradox article has a lot of problems. I just wanted to ask you if it is ok to erase the whole new proposal section as it is completely unsourced. Also does anyone has a reference to Feynman's work about this paradox? --MaoGo (talk) 16:08, 13 February 2018 (UTC)

I'd erase both the "new proposal" section and the one purporting to be about Feynman; the latter looks to be dropping his name onto an unconnected ramble in order to lend it authority. My guess is that if he did say something pertinent, it'd be in the Feynman Lectures on Gravitation, so when I get a chance I'll dig up my copy and check. XOR'easter (talk) 17:16, 13 February 2018 (UTC)

The new proposal looks like unsourced original research and with out reliable source, should go. While the Wheeler-Feynman absorber theory did indirectly address this problem (e.g., An arxiv paper that contains a review of the problem, page 15), the section goes beyond their work into synthesis territory. It should probably be be cut or deleted, too. --Mark viking (talk) 20:18, 13 February 2018 (UTC)

Delete No place for OR. Xxanthippe (talk) 21:40, 13 February 2018 (UTC).

New proposal deleted. Feynman section waiting for confirmation. --MaoGo (talk) 12:54, 14 February 2018 (UTC)

I found my copy of the Feynman Lectures on Gravitation and looked up everything it says about electrodynamics. Nothing in it makes the article section more tenable. I agree that the section goes "into synthesis territory" and should be removed. In fact, the section is so confused as to be backwards: The Wheeler–Feynman absorber theory postulates that a charge does not interact with its own field. XOR'easter (talk) 15:08, 14 February 2018 (UTC)

Wikipedia:Articles for deletion/Emil Martinec

The article on Emil Martinec has been nominated for deletion. XOR'easter (talk) 20:00, 14 February 2018 (UTC)

Wikipedia:Articles for deletion/Grae Worster

There's an AfD on Grae Worster, a fluid dynamicist. XOR'easter (talk) 15:33, 16 February 2018 (UTC)

Graphic worker

Hi
I'm a graphic worker here (and commons) and I would be interested in working with this project. You can view stuff I have made here Goran_tek-en/Gallery because I want you people working here to see if my line of work is something that you think could be useful for you. Please ping me, thanks. --Goran tek-en (talk) 16:41, 18 February 2018 (UTC)

Article needing expert input: Mutual energy principle

This is a new article which claims to show why Maxwell's equations are wrong, based on the work of Shuang-ren·Zhao. I think it would benefit from some independent expert commentary.--Gronk Oz (talk) 14:16, 19 February 2018 (UTC)

It doesn't need commentary, it needs deleting. XOR'easter (talk) 17:34, 19 February 2018 (UTC)

Indeed. Near as I can tell it's entirely one guy's theory and not backed up by independent sources. Primefac (talk) 17:36, 19 February 2018 (UTC)

It looks to be exactly the kind of thing the WP:NOR policy was invented to stop. XOR'easter (talk) 17:38, 19 February 2018 (UTC)

The article in question should be entirely and summarily deleted. It is incoherent and idiosyncratic, and cannot be repaired piecemeal. It cannot be saved by saying 'Oh, it's just that the author is not fluent in English'. It mixes quantum and classical ideas as if they belonged to the same paradigm. It is more or less pure OR. This is currently obvious from its being a very long article that is the work of a sole author.Chjoaygame (talk) 17:39, 19 February 2018 (UTC)

It's too bad FRINGE doesn't fall within the range of WP:G3. Primefac (talk) 17:47, 19 February 2018 (UTC)

Thanks, everybody - that's just the sort of expert response I was hoping for. (I was trying to be polite and not introduce any bias.)

And thanks to Chjoaygame for nominating it for deletion - you can express your opinion there at Wikipedia:Articles for deletion/Mutual energy principle. --Gronk Oz (talk) 04:41, 20 February 2018 (UTC)

Attention needed: Quantum gravity

I don’t know enough to do it, but the following text in Quantum gravity needs editing: - “While confirming consistencies in quantum mechanics and gravity at reasonable energies, it lacks near or above the fundamental cutoff of our effective quantum theory of gravity, assumed at the Planck scale, and needs more study. The problem of combining quantum mechanics and gravity becomes an issue only at very high energies, and may require a new way of thinking. . . . Deriving a valid quantum gravity theory at the highest energy scales assumes that such a simplistic and elegant theory. Accordingly, studying symmetries and other clues offered by current theories that might suggest ways to combine them into a comprehensive, unified theory seems logical.”

Thanks — Jo3sampl (talk) 10:26, 22 February 2018 (UTC)

Perhaps it is too much to expect clear writing in an article about a subject which has no empirical basis and is purely an inconsistent speculation currently. JRSpriggs (talk) 16:44, 22 February 2018 (UTC)

That whole section is confusingly written, enough so that it's hard to tell whether what it is claiming is correct or not. One of the more clear things I've read on the topic is actually a blog post [4], which in this case I think meets the WP:BLOGS standard, being authored "by an established expert on the subject matter". XOR'easter (talk) 22:06, 22 February 2018 (UTC)

The entire "Overview" section was ... really crufty, with lots of oddities wedged in, and needless restatement of things said elsewhere in the article. I tried to edit it into an actual overview. XOR'easter (talk) 17:03, 24 February 2018 (UTC)