Wikipedia talk:WikiProject Physics/Archive September 2011

Reciprocal lattice

my ques is whether we place one point for each set of planes at a distance ( 2 pi times) 1/d on the normal from the origin to the planes or is it one point for each plane to obtain RECIPROCAL LATTICE??

d stands for interplanar distance

59.94.182.124 (talk) 17:42, 7 September 2011 (UTC) neha handa

Questions like this should be directed to the Reference Desk, rather than here; this page is for discussing article maintenance, mostly. --Christopher Thomas (talk) 19:23, 7 September 2011 (UTC)

First Law of Thermo - help

I need help with a well-meaning editor on First law of thermodynamics, who makes statements like:

To insist, as you seem to want to do, on the opening statement of an article on the first law of thermodynamics carrying the message of the principle of the conservation of energy is to push your particular point of view, so as to emphasize the more general law and to distract attention from the particular law which is actually the subject of the article. Your point of view includes the view that the first law of thermodynamics has a core in the law of conservation of energy. That is not what actually distinguishes the first law of thermodynamics and therefore does not have a preemptive claim to primary emphasis in a neutral article.

Thanks PAR (talk) 01:06, 12 September 2011 (UTC)

User:Marshallsumter

FYI, an astrophysics editor has had his articles mass deleted, see Category:Articles created by User:Marshallsumter, which contains a list of deleted articles (no actual articles are categorized there, as they have been deleted). This was done for copyright violations. You might be interested in creating new articles in place of the deleted ones. 76.65.129.5 (talk) 05:26, 13 September 2011 (UTC)

See Wikipedia:WikiProject Astronomy/User:Marshallsumter Incident Article Fix-up Coordination Page for further actions regarding cleaning up the edits to articles this user did not create. (Note that at WT:AST there is already mention of an action requiring the removal of over half the content of an article due to the inappropriate additions by Marshallsumter) 76.65.129.5 (talk) 04:31, 15 September 2011 (UTC)

Real space

Currently the article Real space exists as a stub, which is nothing more than a remark about terminology. I can't escape the feeling that this should redirect somewhere it is discussed in more context. I can't quite find a proper target though. Any ideas?TR 09:13, 14 September 2011 (UTC)

I can't think of anything sensible; let's just leave it alone for now.
― A. di M.​_plé​^dréachtaí 20:29, 14 September 2011 (UTC)

I've formatted and tagged it for now. What else can we do? Can we find references? Bearian (talk) 20:42, 14 September 2011 (UTC)

I think any textbook mentioning reciprocal space will mention real space too. (I can't recall hearing real space specifically as opposed to Minkowski space (simply space, three-dimensional space, or if you want to get pedantic space-like hypersurface being usually used instead), nor as opposed to Hilbert space (physical space, coordinate space or stuff like that).
― A. di M.​_plé​^dréachtaí 10:21, 16 September 2011 (UTC)

Lindblad superoperator

Hello. I found this new article tagged as {{db-a1}}. I admit, the article is incomprehensible also to me, however, G-scholar gives a lot of links for this term, and I think it should be properly discussed. Is there any valuable information for this project? Btw, the page is completely unreferenced. Thanks for any help. Regards. --Vejvančický (talk | contribs) 14:16, 14 September 2011 (UTC)

Btw, I asked also at Wikipedia talk:WikiProject Mathematics, but this is probably the correct forum for this topic. --Vejvančický (talk | contribs) 14:16, 14 September 2011 (UTC)

This should be integrated in an article on decoherence theory. If people want to work on this, but lack the indepth knowledge, this is a good introductory text. Count Iblis (talk) 16:16, 14 September 2011 (UTC)

Again, I've formatted it. I can't say that I'm an expert on this, but I'll try to work on it later. Bearian (talk) 20:45, 14 September 2011 (UTC)

Physics world article

Hi all, wikiproject physics was mentioned in a recent physics world article, if you are a member of the Institute of Physics then you can read the article here: http://physicsworld.com/cws/article/indepth/47019 (actually even if you aren't a member I think you may still be able to register and read the article anyway. There is an associated blog here: http://physicsworld.com/blog/2011/09/become_a_wikipedian.html . It's nice to know that the general physics community are now talking about Physics articles on wikipedia. Polyamorph (talk) 14:54, 16 September 2011 (UTC)

A little bit overenthusiastic, isn't it? I don't think Wikipedia is that awesome. In particular, I'm surprised they chose Introduction to special relativity as an example: it's one of the worst “Introduction to” articles, IMO. (I set out to improve it a few years ago, but I never got around to come up with anything decent.)
― A. di M.​_plé​^dréachtaí 10:26, 18 September 2011 (UTC)

I don't think it's overenthusiastic. The IOP is all about promoting physics so their articles on public outreach tend to be enthusiastic, but this is a good thing IMO. Perhaps they could have consulted wikiproject physics before writing the article for a better choice of articles, but then again it's better to have an outside perspective, since most wikipedia users are not involved with editing. Polyamorph (talk) 10:50, 18 September 2011 (UTC)

Literature of phase boundaries

Literature of phase boundaries is a new article. The format---including getting the software to number the references, if that is appropriate in this case---could use some work by someone skilled in Wikipedia's conventions for this sort of thing.

Are there particular lists that should link to this?

And which articles should link to this? The links still need to be put there. Michael Hardy (talk) 16:05, 20 September 2011 (UTC)

Nice to have literature to refer to, however, I don't think it warrants it's own article. Would be better to transfer the content to talk or userspace and use the references to help improve existing articles. Polyamorph (talk) 11:31, 24 September 2011 (UTC)

Michelson–Gale–Pearson experiment

See Wikipedia:Peer review/Michelson–Gale–Pearson experiment/archive1.

Discussion consolidated at the above link. Headbomb {talk / contribs / physics / books} 15:29, 25 September 2011 (UTC)

Really crazy stuff possibly going on

What do you think of this? My first thought was that there must have been some kind of glitch, but according to rumours people have known about this anomaly and tried to explain it for several years. (Also, they're changing the schedule of the first day of the national congress of the Italian Physical Society next Monday, in order to fit in it a one-hour talk about that.) Do you think it would be premature to mention that in WP articles (e.g. Unsolved problems in physics)? (As for me, I can't wait for the talk on Monday to hear what people think might be going on. A part of me believes/hopes that there must be some not-so-crazy explanation for that.)
― A. di M.​_plé​^dréachtaí 19:10, 23 September 2011 (UTC)

It already has brief mention in the neutrino article. Until it's confirmed independently, to this level of precision, by other labs, that's sufficient mention IMO. According to the press release yesterday, the FTL measurement is expected to be the result of systematic errors rather than actual FTL travel, but they're having trouble pinning down what the systematic error is (obvious possibilities were ruled out). --Christopher Thomas (talk) 20:51, 23 September 2011 (UTC)

On this topic, could the project members keep an eye open for well meaning but completely unbalanced additions by runby editors going of the media hype? TR 22:15, 23 September 2011 (UTC)

I already had to remove a paragraph in Special relativity on it.

Most likely it is a mistake of some kind. Otherwise, neutrinos would be tachyons which would allow an effect to precede its cause. A failure of SR would be far less likely than either of those, IMHO. JRSpriggs (talk) 06:34, 24 September 2011 (UTC)

It probably is an error, however it is being reported by the mainstream press and other reliable sources. Although it clearly doesn't warrant article re-writes, it does deserve a mention. Polyamorph (talk) 07:05, 24 September 2011 (UTC)

I can see why you removed the arxiv reference, however the BBC references only goes to show how notable the "discovery" is. I think the paragraph was well sourced, not sure if it belongs in special relativity but it is sufficiently notable and sufficient sources had been given in that case. If not then there are numerous other sources that could be provided instead including e.g. nature news http://www.nature.com/news/2011/110922/full/news.2011.554.html . I agree we should be careful though to make sure the claim is discussed according to WP:DUE. Polyamorph (talk) 07:12, 24 September 2011 (UTC)

Oh sorry I didn't see Christopher Thomas's comment that it is already mentioned in the neutrino article. I agree that this is sufficient mention so it's right to remove it from special relativity. Cheers, Polyamorph (talk) 07:14, 24 September 2011 (UTC)

Tachyon neutrinos (while retaining Lorentz invariance) wouldn't behave like that: less energetic neutrinos such as those in SN1987A would have to travel even faster, but those travelled within a few parts per billion of c. (Unless antineutrinos have different m² than neutrinos or stuff like that, which I would regard as somewhat less crazy than Lorentz violations.) Still, such a collaboration looking for systematic errors for years and failing to find an error one order of magnitude larger that the sum in quadrature of all the errors they did find is also somewhat crazy. Someone in the internet suspects a software bug, but in my experience data with that kind of errors often look quite ‘unnatural’ and these data don't to me. Right now my money would be 10% on Lorentz violation, 40% on crazy proprieties of neutrinos, and 50% on experimental errors (25% of which on stuff like someone deliberately messing up with the GPS system – the US military used to officially do that, but in such a way I think we would have detected, so if this is the answer they must be doing it in a more subtle way.)
― A. di M.​_plé​^dréachtaí 11:26, 24 September 2011 (UTC)

FWIW, I have requested semi-protection of Speed of light and Neutrino. DVdm (talk) 09:18, 24 September 2011 (UTC)

Mass–energy equivalence is also receiving some attention from well meaning anon and newly created accounts. Polyamorph (talk) 09:29, 24 September 2011 (UTC)

If you read the article, you'll see that measuring the time of flight is a tour de force. Unlike the distance measurements, what they had to do here is not yet routine to the accuracy necessary for this experiment. With clocks at different locations being involved, they had to account for many more factors than in case of measurements involving only one clock. All sorts of delays when signals travel through the electronic equipments now don't cancel anymore. Also simply reading off the time of events in CERN from the clock there that is synchronized using the same GPS signals as used to synchronize the LNGS clock is already quite difficult. They did perform a direct measurement to compare both clocks to each other via a third device that was physically transported from CERN to LNGS to check if this is done correctly, but this was a one off measurement. Count Iblis (talk) 16:32, 24 September 2011 (UTC)

Those delays when signals travel through the electronic equipments were each measured several times with three different methods which agreed with each other, and, if I understood today's talk (which was streamed from Gran Sasso to L'Aquila through a very poor internet connection, with a very loud mains hum, and the speaker was speaking English with such a strong Italian accent I started to wonder if he was doing that on purpose) correctly, the physically transported clock thing was done as an extra precaution after they were already quite confident of the synchronization, which turned out to be about 2.4 ns off.
― A. di M.​_plé​^dréachtaí 19:39, 26 September 2011 (UTC)

Magnetically Inflated Cables

described here from the StarTram concept www.niac.usra.edu/files/studies/final_report/1133Powell.pdf Is it a new idea, does it deserve an article ? Since i do not have the capability to understand the science behind the paper, can someone be nice and point me in the right direction for vulgarization ? --Beaucouplusneutre (talk) 21:21, 26 September 2011 (UTC)

The StarTram article sounds like a sales pitch for this particular group's magnetic launch scheme. I've tagged it as such, so that someone with time on their hands can tone it down a bit.

With regards to the magnetically inflated cables redlink, the concept is fine, but I don't think it'll pass the notability guideline for its own article (that would require more than one person or research group to be writing about it). The core concept is the same as the one they propose to use for lifting the end of the gen-2 magnetic launcher: run current through a superconducting loop of wire, and magnetic forces will push outwards on the loop (making it fully expand into a ring shape if it wasn't already expanded). What the cable paper is proposing is to build large kevlar balloons in any desired shape (along the same lines as inflatable space habitat proposals), but to "inflate" them by running current through wire loops embedded within them instead of by filling them with gas.

I hope this gives you enough context to help! --Christopher Thomas (talk) 00:01, 27 September 2011 (UTC)

Planck length article template locks in eroneous value

article value correct, box value wrong. Talk page had this noted 12 March 2010 but not fixed as yet. Might need template write access to fix.

See CODATA2010 to verify,

http://physics.nist.gov/cuu/Constants/Table/allascii.txt

Planck length 1.616 199 e-35 0.000 097 e-35 m — Preceding unsigned comment added by 69.234.106.21 (talk) 04:08, 28 September 2011 (UTC)

Dark matter and black holes (again)

An editor has recently inserted mention of primordial black holes as a dark-matter candidate into Dark matter (edit | talk | history | protect | delete | links | watch | logs | views). I seem to recall a lengthy discussion of that topic from a few months ago, with the removal or substantial downsizing of mention of that claim, but I'm having trouble finding the threads in question (might have been at one of the black hole / primordial black hole / micro black hole / black hole with a side of fries articles, or the MACHO article, or elsewhere). If anyone else feels up to vetting the addition, by all means do so, as my understanding was that microlensing experiments had ruled out most forms of such claim and failed to provide actual evidence for any form of that. ObCaveat: I am not an astronomer or astrophysicist. --Christopher Thomas (talk) 20:03, 26 September 2011 (UTC)

Found at least one of the threads: Talk:Dark matter#Lack of evidence for WIMPs. --Christopher Thomas (talk) 18:11, 29 September 2011 (UTC)

Images from arxiv papers

Hi there,

Just a quick question, are images within a pre-print paper in ArXiv considered as released into the public domain? A couple of images from the OPERA neutrino paper have found their way in the CERN Neutrinos to Gran Sasso article and I am unsure of the correct attribution. Regards ^Khukri 05:57, 29 September 2011 (UTC)

No. The copyright of images of articles on Arxiv are property of their authors (or in some cases their employer). So, unless the images have been explicitly released to the public domain, they are not free to use.TR 06:02, 29 September 2011 (UTC)

Cheers ^Khukri 06:46, 29 September 2011 (UTC)

Article assessment

As of yesterday ALL articles in the WikiProject Physics have both quality and importance assessments! Special thanks to user:meno25 for his tireless activity in assessing the last 1000 or so stubs! TR 05:59, 29 September 2011 (UTC)