Wikipedia talk:WikiProject Physics/Archive May 2010

This is an archive of past discussions about Wikipedia:WikiProject Physics. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

Physics portal

I think part of the introduction in the Physics Portal could use a re-write. The best introduction might be something similar to the introduction in the actual Physics article. Also, although there is a quest to "unify forces" with one theory, I don't percieve this as the main goal of physics, and I am not sure that it should be termed as the "biggest goal". There is a lot of other work going on besides trying to discover a unified theory. Also, I don't think it is necessary to state that "it can be thought of as a foundational science, upon which stands 'the central science' of chemistry, and the earth sciences, biological sciences, and social sciences". I don't think this is exactly correct. The other sciences seem to accomplish their research without specifically refering to Physics on a regular basis, imho. However, there is an interrelationship, which may be a more accurate way of stating this idea. Please feel free to correct me if I have an incorrect perception here.

And of course I don't see, exactly, where physics is foundational to the social sciences. Maybe from the deterministic view of classical physics? Also, the Portal needs a selected article and selected photo. Personally, I could do that, for the time being, if no one objects. There seem to be plenty of available physics articles, imho. ----Steve Quinn (formerly Ti-30X) (talk) 06:48, 28 April 2010 (UTC)

I agree about "main goal": those who are trying to work out how high-temperature superconductivity works or how to get more energy from nuclear fusion than you need to get it started don't give a damn about how to unify the Standard Model with general relativity.

As for the social sciences, I guess the point is that the mathematical methods of physics can be applied to them. (I once attended a seminar which described a model (worked out by a physicist) describing stock market fluctuations pretty well. (Not to mention the importance of aerodynamics and Fourier analysis, respectively, in articulatory and acoustic phonetics...) But saying that physics is the "central science" of social sciences sound like too wide a stretch, IMO. ― ___A._di_M. (formerly Army1987) 11:38, 28 April 2010 (UTC)

The "do you know" entry on the temperature of the Big Bang appears to be wrong. It says "that the Big Bang's temperature was about 1,800,000,000,000,000,000,000,000,000,000 °F (18 ²⁸ °F) when it was born?". This leaves out "×10" from "18×10²⁸". Also the long version of the temperature is ten times the abbreviated version.

More to the point, how can the Big Bang be said to have any specific finite temperature? My understanding was that it fell from infinity. JRSpriggs (talk) 01:04, 29 April 2010 (UTC)

My thanks to Steve Quinn (talk · contribs) for fixing this problem. JRSpriggs (talk) 00:14, 30 April 2010 (UTC)

@JRSpriggs: E=mc², then if the temperature was infinite now we could have an infinite mass in the universe, that isn't true. --Aushulz (talk) 11:13, 30 April 2010 (UTC)

To Aushulz: I was not saying that the temperature was infinite at any time after the creation event. I was saying that however large a finite temperature one specifies, there was a time before which the temperature of the universe was hotter than that.

Also, the (non-gravitational) energy of the universe might very well be infinite, if the universe is infinite in spatial extention. All that we can say is that, after the creation event, the energy in any finite volume is finite. JRSpriggs (talk) 00:56, 1 May 2010 (UTC)

I personally think that the universe can't have a infinite extention, cause it's expanding from a little original area. The evidence that it's expanding correspond to the fact that it isn't yet infinite, but it try to reach an infinite extension. I never studied astrophysics or quantomechanics, so probably my opinion is wrong or incomplete, but I remember that there is a open disputy regard to the finity or infinity of universe, isn't it? Well, perhaps I am going off-topic...

However I think that the value of temperature you said correspond to a particular interval of time when a particular type of particle was created. If that is the littlest possibly particle, maybe that temperature correspond to the initial temperature, but we can't know what was before that time... (a universe of energy? or the end of another universe, in a cyclic perspective? or an infinite temperature?) --Aushulz (talk) 01:49, 1 May 2010 (UTC)

I believe that the character of the Big Bang at the earliest moments, finite or infinite, is really unknown. In the older, pre-inflation, picture, we thought the geometry would be positively or negatively curved, or flat, depending on the mass density relative to the energy of the expansion. The flat or negatively curved cases had infinite spatial extent (and thus infinite mass, given finite non-zero density). Those three geometries would not have changed since the earliest times, meaning if it were infinite now, it would have been infinite from the beginning, despite the tendency of some (mostly journalists, I guess) to say the universe was "small" at the moment of the BB. It was "small", of course, relative to its current spatial extent, but not necessarily absolutely. Things have gotten a lot more complex in the last thirty years, what with with inflation and cosmic acceleration, but I think this basic uncertainty remains. It's pretty flat now, we know that; and so, very much larger than we can see, even looking back to the CMB horizon. What was "possible" at the earliest times is mysterious, because we do not know the fundamental physics then, only that our current "laws" must break down somehow. It is surely true that no definite temperature can be assigned to the earliest moments (when the excitation and particle energies were higher than our current experimental experience goes). This is obviously well beyond my own conceptual horizon, perhaps someone really expert in the field can clarify the issues. Wwheaton (talk) 16:36, 2 May 2010 (UTC)

Thank you for explanation. Now it's more clear for me. :) --Aushulz (talk) 23:39, 2 May 2010 (UTC)

User10 5 and his theory on the gravitational constant

Can someone have a look at Special:Contributions/User10_5? According to his user page, a "Theorist, Mathematician, Programmer, Engineer", with "a theory on the gravitational constant". His most recent edit looked like totally wrong, and was reverted. I'm looking at his first edits now. This is probably that "new theory on the gravitational constant". Of course it is unsourced and original research, so it can be removed as such, but can someone have a look at whether it is just nonsense as well? A look at the other contributions might be in order as well. DVdm (talk) 16:21, 1 May 2010 (UTC)

Talk:Leptogenesis (physics)

A discussion is going on about whether the article is misleading on the relation between the SM and leptogenesis. It's very civil and clueful, so don't worry about getting involved in some annoying edit war with cranks. Headbomb {talk / contribs / physics / books} 11:07, 29 April 2010 (UTC)

Anyone? Headbomb {talk / contribs / physics / books} 12:02, 3 May 2010 (UTC)

I'd go with "the Standard Model predicts no mechanism able to change the lepton number (that is the number of leptons minus the number of antileptons)", or something like that. ― ___A._di_M. (formerly Army1987) 12:57, 3 May 2010 (UTC)

Your comments requested

We really need input from other people on the isotope and nuclide talk pages and the possibilities of their merger, transfer of info from one to the other, or continued split with few changes. Please see talk:isotope. S B H arris 18:45, 1 May 2010 (UTC)

I don't think that much more can be said about isotopes than that they are nuclides with the same Z, can it? ― ___A._di_M. (formerly Army1987) 12:50, 3 May 2010 (UTC)

Not if you want the word "nuclide" (the physicist term) to bear the entire burden of the term (and forget that "isotope" is the earliest historical term, and the one still used most often by chemists). But it's a valid viewpoint. Please go to TALK:Isotope and express it. Right now we have a lot of opposition from one person to removing any info from the isotope article, even though one possiblity is indeed to cut it down to one paragraph (or one line). S B H arris 16:48, 3 May 2010 (UTC)

Can someone check this edit on Pion?

Specifically this. Headbomb {talk / contribs / physics / books} 21:26, 2 May 2010 (UTC)

FWIW, google books with items "pion decay "weak interaction" boson" produces this: Neutral pion via electromagnetic reaction into two photons. The charged pion via weak interaction to muon an mu-neutrino. DVdm (talk) 21:53, 2 May 2010 (UTC)

It has always been my understanding (ca late 1960s) that the π° decay goes by the E-M interaction, while the charged pion decay is by the weak interaction. The obvious "reason" would be that lepton number is conserved except in the weak interaction, and there is no way a charged pion can decay into lighter particles without violating lepton number conservation. So E-M is ruled out by the non-existence of suitable lighter decay products. The π° —> 2γ decay does not violate lepton conservation, so it can go by the ~10⁸ stronger (& thus faster) E-M process, since it is not forbidden. This is a pretty feeble, superficial explanation, but at least it is easy to remember. Wwheaton (talk) 01:59, 3 May 2010 (UTC)

The neutral pion consists of a particle (up-quark or down-quark) and its anti-particle (anti-up-quark or anti-down-quark respectively) with no net spin. So there is no barrier to their decay into two photons with opposite spins. This is the main process. Weak decay via Z⁰ is also possible, but less common. In that case, the result would likely be an electron and a positron or a neutrino and an anti-neutrino.

Lepton number is also conserved in decay of charged pions. But electromagnetic decay is not possible (because the photon is not charged). So the process is: π^– (anti-up-quark + down-quark) goes to W^– (minus much energy) which goes to μ^–+anti-ν_μ, a weak process. The reason that the weak process is slower is that it requires tunneling through a large potential barrier since the W particle has much more mass than the pion. JRSpriggs (talk) 06:45, 3 May 2010 (UTC)

Thanks, and apologies for my stupidity in forgetting to count the neutrino, etc .... :) Wwheaton (talk) 17:41, 3 May 2010 (UTC)

Newton's laws of motion

~~Could someone please look at Talk:Newton's laws of motion#Edit request from Elobroxium, 3 May 2010 please.~~

~~And please remove this if it has been dealt with. Thanks, Chzz ► 14:36, 3 May 2010 (UTC)~~ Done Chzz ► 14:45, 7 May 2010 (UTC)

Resolved

What to do with the Nuclear energy article?

Looking at Wikipedia:WikiProject Physics/Popular pages sorted by assessment level, I found Nuclear energy with a "merge" tag to Binding energy, but no discussion about that on either talk page.

I agree that Nuclear energy should be merged somewhere, but Binding energy is a title which makes the article appear to have a much broader scope than that. So I'd propose this course of action:

merging the present Nuclear energy article and sections 2 to 4 of Binding energy into a new article Nuclear binding energy (currently a redirect);
making Nuclear energy a dab page, listing Nuclear binding energy, Nuclear power and Nuclear Energy (sculpture);
adding summaries of Nuclear binding energy, Electron binding energy, Gravitational binding energy, Bond energy (am I missing any?) to Binding energy;
if the article created at point 1 is short enough, merging it into Nuclear force.

Do you think it's a good idea? — Preceding unsigned comment added by A. di M. (talk • contribs)

Just get rid of the thing. This is a short article that doesn't say anything that isn't individually in the nuclear energy section of binding energy, or the relative sections of radioactive decay, atom, stable isotope, energy and a number of other places this chart is used. Any redirect could be to any of these sections (since a redirect can GO to just a section of another wiki).
Moreover, THIS article is badly named. I expected it to be about nuclear reactor technology or nuclear power.
So I suggest it not be merged (in this cases a euphemism) but deleted, and any uses of it elsewhere in other wikis as a target, be redirected to Binding_energy#Nuclear_binding_energy_curve. S B H arris 15:12, 3 May 2010 (UTC)
I still think that Binding energy is too focused on one particular type of binding energy, given its title, so I stand by my plan (even if the contribution of Nuclear energy to the merger of point 1 would be zero). ― ___A._di_M. (formerly Army1987) 16:00, 3 May 2010 (UTC)
I think it is a good proposal, with clear article names. /Pieter Kuiper (talk) 16:12, 3 May 2010 (UTC)

What's a good proposal? There is nothing clear about the name "nuclear energy." The Sun is powered with nuclear energy. So is radioactive decay and plate tectonics. In English, "nuclear energy" is usually used by people who mean "fission-powered electrical generation." So this is a good term for a dab page, but since it's so nondescript, it's not very useful for much else. S B H arris 16:33, 3 May 2010 (UTC)

The proposal is to make "nuclear energy" a disambiguation page... ― ___A._di_M. (formerly Army1987) 19:03, 3 May 2010 (UTC)

In my personal experience, "nuclear energy" means "fission-powered electrical generation" much much more often than any other definition. So I would vote for redirect to nuclear power, plus an extra {{otheruses}} template at the top of the nuclear power article that says ""Nuclear energy" redirects here. For other uses, see Nuclear energy (disambiguation)". --Steve (talk)

Speaking as a fairly naive observer, I tend to agree. I certainly the overwhelming majority of searches will be intending nuclear power. Links are possibly another matter — if it's going to be an ongoing problem that physics authors link nuclear energy when they mean something other than nuclear power, that would be an argument for the dab page. --Trovatore (talk) 21:33, 3 May 2010 (UTC)

By glancing at Special:WhatLinksHere/Nuclear_energy, I guesstimate that about 80% of the links are supposed to be about nuclear power. So a redirect might be a good idea. ― ___A._di_M. (formerly Army1987) 11:49, 4 May 2010 (UTC)

OK, I've been bold.[1][2][3][4]. This didn't involve creating any new pages, so anyone can revert. ― ___A._di_M. (formerly Army1987) 14:44, 4 May 2010 (UTC)

Talk:Alfvén wave-faster than speed of light?

Alfvén wave is faster than speed of light? Newone (talk) 10:09, 11 May 2010 (UTC)

Does anything travel at that speed? If not, no problem. JRSpriggs (talk) 11:13, 11 May 2010 (UTC)

An item of interest

I came just came across a physics textbook (online), which appears to have been co-authored by John Henry Poynting and Sir Joseph John Thomson, published in 1907. I was thinking that maybe the physics community here would be interested, because these are two well known and notable physicist. Perhaps it is not a surprise that the name of the book is "A textbook of Physics, Volume 1 " (link provided). According to the preface, this is supposed to be one in a series of physics textbooks. The preface states that this book was to be followed by other books which seperately dealt with the following subjects: Heat, Magnetism, Electricity and Light. However, I don't know how the intention for a series turned out. The preface also gives an overview of the scope of subject matter covered in the book, which is interesting (to me). A book dealing with "Sound" had, by this time, already been published. ----Steve Quinn (formerly Ti-30X) (talk) 01:36, 17 May 2010 (UTC)

WP:PRIZE

By the way, if you don't know, there's a WikiProject Awards and prizes. So if you come across articles on physics medals or other awards, do 'em a favour and tag the page with {{WP Awards}}. I'm sure they'll appreciate it. Headbomb {talk / contribs / physics / books} 01:45, 17 May 2010 (UTC)

Unreferenced Biographies of Living Persons

The WikiProject Unreferenced Biographies of Living Persons (UBLPs) aims to reduce the number of unreferenced biographical articles to under 30,000 by June 1, primarily by enabling WikiProjects to easily identify UBLP articles in their project's scope. There were over 52,000 unreferenced BLPs in January 2010 and this has been reduced to 32,665 as of May 16. A bot is now running daily to compile a list of all articles that are in both Category:All unreferenced BLPs and have been tagged by a WikiProject. Note that the bot does NOT place unreferenced tags or assign articles to projects - this has been done by others previously - it just compiles a list.

Your Project's list can be found at Wikipedia:WikiProject Physics/Unreferenced BLPs. As of May 17 you have approximately 66 articles to be referenced. The list of all other WikiProject UBLPs can be found at Wikipedia:WikiProject Unreferenced Biographies of Living Persons/WikiProjects.

Your assistance in reviewing and referencing these articles is greatly appreciated. If you have any questions, please don't hestitate to ask either at WT:URBLP or at my talk page. Thanks, The-Pope (talk) 17:43, 17 May 2010 (UTC)

WP:JCW help

There's a new WP:JCW report.

Out of the 500 most highly cited missing journals, here's a few that fall into our scope, or near our scope.

See the writing guide if you need help with those. Some of these might be better as redirects (Guide to redirects). Feel free to remove those which you think are too far from physics from the list. Headbomb {talk / contribs / physics / books} 07:06, 20 May 2010 (UTC)

Duffy's constant

The new article titled Duffy's constant is an orphan: no other articles link to it except the list of mathematics articles, where the link was put there by a bot. Michael Hardy (talk) 04:42, 11 May 2010 (UTC)

The article is worthless. I suggest it be deleted. Xxanthippe (talk) 05:49, 11 May 2010 (UTC).

It's a hoax. 0 hits on google or google books, except wikipedia-related. And it was written by someone whose username is almost "Duffy" and who has no other edits: Duffadious (talk · contribs). --Steve (talk) 05:51, 11 May 2010 (UTC)

I proposed the article for deletion. -- Crowsnest (talk) 06:43, 11 May 2010 (UTC)

Sent to speedy. Someone block that guy 19 ways to hell. Headbomb {talk / contribs / physics / books} 11:24, 11 May 2010 (UTC)

I know the guy who created the page - it was partly a joke but it was also a serious idea. It is a useful constant that saves a multiplication of two other ones in a formula much the same way that the Boltzmann constant does.... lordmwa (talk) 19:42, 25 May 2010 (UTC)

User:Systemizer

Systemizer (talk · contribs) is active again, this time inserting WP:OR into Dark energy (edit | talk | history | protect | delete | links | watch | logs | views), Cold dark matter (edit | talk | history | protect | delete | links | watch | logs | views), and probably elsewhere. They've been repeatedly warned about doing this, but blank their talk page after most warnings are added. Someone else can handle cleanup on this, as I'm busy enough with other obligations to have had to curtail my wiki activities again. As a clear violation of Wikipedia policies is occurring, and the user has been repeatedly warned, this can probably go straight to WP:AIV (after adding more warnings, unblanking the old warnings, and so forth; make sure to hardlink versions of his talk page with warnings, as he'll blank them again). --Christopher Thomas (talk) 16:38, 30 May 2010 (UTC)

Thanks for the fast response! Now it's just a cleanup issue. --Christopher Thomas (talk) 22:33, 30 May 2010 (UTC)