Wikipedia talk:WikiProject Physics/Archive January 2008

Mathematics in articles

I've now read through about 50 of the articles in Project Physics, and I have some suggestions. Hopefully, the rest of you won't mind if I incorporate some of them into the articles. The content is excellent in the articles I've read so far, although there are some serious problems with readability in a good percentage of them. I think one major source of the readability problem is the method of incorporation of the mathematical equations. Many of the articles use mathematical symbols and methods that are far above the comprehension of the average reader (which is understandibly necessary considering the complexity of the topics discussed), but do not provide adequate explanation of even what type of mathematics is being used (vector calculus, linear algebra, complex analysis, differential geometry, etc.), to say nothing of the conventions being employed in the equations (vector, matrix and tensor notations, differentials, compact summations, complex numbers, etc.). I would like to insert cross-references to math articles on a lot of these, at least directing the reader where to begin if they wish to decipher the math, and perhaps add some more intuitive explanations to complement the mathematial ones, where appropriate. If there are any objections, please feel free to discuss/revert as you all see fit.Kevin Borland, Esq. (talk) 11:07, 2 January 2008 (UTC)

That sounds like a good idea, if it can be done without breaking the flow of the article too much. The rarity of such explanations now is not due to any policy against it, but rather to a lack of enough available time for those expert enough to do it. JRSpriggs (talk) 03:30, 3 January 2008 (UTC)

I'll be working on it. I started a little bit with Angular momentum operator.Kevin Borland, Esq. (talk) 04:06, 3 January 2008 (UTC)

Sounds good, especially the bit about cross-references to math articles. My only concern would be that you might dumb things down or add too much verbiage to articles where obscure symbols and gobs of equations are necessary and appropriate. It's all judgement calls, of course. Gnixon (talk) 06:16, 8 January 2008 (UTC)

Help with an article

We meed people willing to push back against New Age psuedoscience pushers at Talk:Consciousness causes collapse. Thanks. ScienceApologist (talk) 20:08, 9 January 2008 (UTC)

LHC help

It looks like the LHC article has come to the attention of a certain W.L. Wagner and a few others in the same way as the RHIC did. I would appreciate the input of members of this project on the safety concerns section, I am trying to be objective with regards to the fears, but I'm seeing more and more original research and unproven bunkum being added. I am now being accused of censorship, conflict of interest and have been threatened by supposed media interests. Please see the talk page and any help would be appreciated. Cheers ^Khukri 09:36, 6 January 2008 (UTC)

Perhaps someone with an interest in high energy physics would consider expanding that section of Physics, which is pretty thin right now. Gnixon (talk) 14:53, 18 January 2008 (UTC)

Peer review

Wikipedia:Peer review/Force. Please comment. Thanks. ScienceApologist (talk) 16:45, 11 January 2008 (UTC)

ScienceApologist seems to have become inactive, so let me take up is call for help at Force. Help appreciated. Gnixon (talk) 14:52, 18 January 2008 (UTC)

"The best possible unification for any collection of physical theories"

The article on consequence operators cites a paper with the above title, as well as two more by the same author. Therefore the article is listed in Category:Theoretical physics, although its subject is really somewhere between pure mathematics, mathematical logic and philosophy. I would appreciate it if a theoretical physicist could comment on the article's talk page. --Hans Adler (talk) 19:29, 21 January 2008 (UTC)

To me, the article looks like mathematical logic rather than any kind of physics. The fact that the subject is mentioned in a source on physics is irrelevant. JRSpriggs (talk) 03:06, 22 January 2008 (UTC)

Thanks, that's what I expected. I already know that the mathematical citation index of this author is marginal (not surprising, given his style) and have removed all the mathematical content accordingly. Is there something like MathSciNet where I can check this for theoretical physics? Since the author is an ex-editor I want to act in a revision proof way. --Hans Adler (talk) 12:45, 22 January 2008 (UTC)

V-Process

Hello, just wondering if anyone know what it is. I have stumbled on it and never heard of it. The Abundance of Interstellar Fluorine and Its Implications

Uncertain if Template:Nuclear processes template should have a section for V-Process. Marasama (talk) 06:52, 22 January 2008 (UTC)

Pseudoscience

Hi, I am a member of the Physics wikiproject at the Spanish wiki. I've seen the wikiproject here takes some sort of action towards pseudoscience as is listed in the scope of the wikiproject: "Watching out for pseudoscience in physics articles and categories". So I want to know exactly what does "watching out" mean here, or what are the actions you take towards pseudoscience. This is because I consider it is a relevant issue for physics here in wikipedia and elsewhere, but it worries me that some of these actions may be taken as a violation of NPV, particularly if we impose the scientific views in pseudoscientific articles, when there is people ready to take the positions of pseudoscience. Also what is your experience with dealing with this people? I ask all of this because I am considering to propose something similar to what you do here in the Spanish wiki. --Homo logos (talk) 00:25, 25 January 2008 (UTC)

Science is not a "neutral point of view": it has a very strong and slanted point of view, namely the "scientific point of view". The steps taken here are usually:

• Promptly remove any pseudoscientific content that finds its way into legit science articles. This can often lead to edit battles.
• Clearly label articles about pseudoscience topics as being about pseudoscience, and place them in Category:Pseudoscience. This is even more likely to lead to edit wars, which can sometimes last for months or years.

Particularly vulnerable are articles in any way related to general relativity (because some need to prove themselves as being smarter than Einstein, or have mechanisms for time travel, etc.) and also quantum mechanics, and in particular, interpretations of quantum mechanics (because quantum measurement is inherently mysterious, and attracts amateurs, many of them well-meaning, but without knowledge.)

Note also: some editors tackle subject matter that is over their heads, and thus make innocent mistakes. Again, this seems most frequently the case in gravity and QM: a few semesters in college or having read a book is really not enough to write on these topics.

Particularly tiresome are the advocates of perpetual motion machines, the electric universe cosmology, etc, as many of the involved editors want to present these topics as science, not pseudoscience. And then there's intelligent design. Sheesh ... linas (talk) 04:11, 27 January 2008 (UTC)

I quite agree with you science is not about a NPOV, but still that is not necessarily the opinion of the admins here, don't they help in these edit wars you describe? I confess that is my main preocupation: the reaction the authorities may have, whether they endorse or not the scientific POV. --Homo logos (talk) 15:56, 27 January 2008 (UTC)

It's true that all notable POV on a given subject must be reflected in an article. The trick is that the scientific POV is always far more notable than the pseudoscientific POV. In many cases this means that it doesn't even need to be mentioned in the article; if it's notable for having a large number of supporters, then it can be mentioned in the article, but it can also be explicitly stated that it is generally considered either disproven or nonscientific by the majority of the scientific community. (Look at the mentions of creationism in the evolution article, for instance.)

Consequently, the general society of editors will be on your side if you choose to fight the insertion of pseudoscience into science articles. My own personal experience is that you should not "engage" the pseudoscientists in talk page discussions about the science itself; once it's clear that they are pushing for an unbalanced POV, don't feel compelled to defend mainstream science on discussion pages. --Starwed (talk) 04:58, 28 January 2008 (UTC)

If the pseudoscientific POV is notable, inclusion with a scientific rebuttal may help the reader. Explaining why perpetual motion machines don't work is better than ignoring them. Jehochman ^Talk 05:15, 28 January 2008 (UTC)

Just don't use Wikipedia to educate readers about why pseudoscience is wrong. The encyclopedia can't explain wny perpetual motion machines don't work, but if a notable source has done so, it makes sense to present that point of view. Everything attributed, of course. Gnixon (talk) 14:30, 28 January 2008 (UTC)

Thak you all, your replies were most useful.--Homo logos (talk) 00:28, 29 January 2008 (UTC)

Quarks and gluons

Small Essay I did which may be useful to take parts from for use on Quark/Gluon articles. References at bottom.

Background

As the detection of subatomic particles became more advanced during the 1950s a large number of new particles called hadrons, a collective term for protons, neutrons and other particles governed by the strong nuclear force, were discovered. The hadrons can be categorised into two types: mesons comprised of two quarks and baryons made of 3 quarks. Due to the number of different hadrons’ detected it seemed unlikely that all were fundamental particles. This idea was bolstered by Robert Hofstadter of the Stanford Linear Accelerator Center who in 1956 discovered a scatter pattern for the proton which implied that it was not a point particle, but made of other constituent parts1.

As a result of these observations a number of different theories were postulated. Amongst these theories was the quark model developed independently by Murray Gell-Mann and Yuval Ne’eman2 who noticed a mathematical relationship or multiplet when they grouped mesons or baryons with the same spin.

Initially there were only thought to be three quarks: the up with charge +2/3 and the down and strange both with charge -1/3. However, as particle accelerators became more powerful the heavier, more energetic; charm, top and bottom quarks were added to the model, eventually completing the family of quarks as shown in table 1. It is important to note that the masses of quarks are inferred as they can never be isolated (see colour confinement) to measure their mass directly.

Quark Generation Symbol Spin Charge Baryon Number Mass Up 1st u 1/2 +2/3 1/3 360 MeV Down 1st d 1/2 -1/3 1/3 360 MeV Strange 2nd s 1/2 -1/3 1/3 540 MeV Charm 2nd c 1/2 +2/3 1/3 1500 MeV Top 3rd t 1/2 +2/3 1/3 175 GeV Bottom

3rd b 1/2 -1/3 1/3 5 GeV Table 13

As quarks make up the hadrons which are held together by the strong force there must be an associated force carrier which transmits the strong force between quarks. This was given the name “gluon”.

Quark Properties

Spin and Colour

By knowing that 3 quarks make a baryon whose smallest possible spin is ½ and 2 quarks make a meson with integer spin, the quark model implies that each quark must have a spin ½.4.

The S= 3/2 baryon, Δ++ consists of three identical u quarks. However, by the Pauli Exclusion Principle no particles of half integer spin are allowed to occupy the same quantum state at the same time5. This problem was resolved in 1965 when Oscar W. Greenberg and Moo-Young Han with Yoichiro Nambu independently proposed another quantum number for the quark thus ensuring the Pauli Exclusion Principle was observed. This abstract mathematical quantity was given the name “colour charge” although is often just referred to as colour. The different colours for quarks are red, blue and green whilst anti-quarks have conjugated colours: anti-red, anti-blue and anti-green6.

The group of Han and Nambu went further by also suggesting an octet of bosons7; the gluons colour be responsible for quark interactions. These gluons interact with quarks by also carrying colour charge. They are bi-coloured containing both colour and anti-colour charge required for a quark interaction. Quark-gluon interactions can be better understood by using a pictorial representation called Feynman diagrams.

                         Figure 13

In figure 1 (where time goes from left to right) we can see that the change from a green to blue quark requires a gluon to be produced which takes the colour away from the green quark and replaces it with blue colour. The result is a green-antiblue gluon being produced. The gluon is then responsible for the reverse reaction converting the blue quark into a green one on the right hand side. Reactions like these are responsible for binding the quarks together in mesons and baryons and consequently holding the protons and neutrons in nuclei together.

Colour Confinement

Unlike other fundamental particles quarks have the unusual property that they cannot be found in isolation and are always found within mesons or baryons. This is supported by the failure of numerous experiments to find a free quark. Combinations of quarks are only allowed if the sum of their colour is neutral or “white”. In mesons this occurs by having a quark/anti-quark grouping of the same colour whilst baryons are a combination of the 3 colour or anti-colour quarks to produce white.

When trying to overcome the strong force to separate quarks it is found that the amount of energy required incredibly large and does not decrease with distance - unlike the other fundamental forces. As quarks separate, the gluon fields form tubes (or strings) of colour charge which act like rubber bands pulling the quarks back together. The size of this force is so large that any attempt to try and separate quarks from each other instead results in a new meson being created from the vacuum. This is because the energy required to separate the quarks to a viewable distance is larger than the pair production energy of a quark-antiquark pair i.e. new matter is created from this energy.

Figure 316: An attempt to pull apart a meson results in new matter being created. Here the green represents the colour force field.

Discoveries of Other Quarks

The Charm

As discussed earlier, it was initially believed only three quarks: the up, down and strange existed. These had been much easier to detect given their relatively low energies. However in 1970 a collaboration of Sheldon Glashow, John Iliopoulos and Luciano Maiani8,15 recognized the need for a fourth quark called the charm “to understand the symmetry structure of the weak force”4. This particle was confirmed in 1974 when two groups one at Brookhaven National Laboratory and the other at the Stanford Linear Accelerator Centre both spotted a large peak in the number of partials detected when a positron and electron were smashed together at an energy of 1550MeV/particle. The particle detected turned out to be a charm/anticharm meson providing direct evidence of the existence of the charm quark and thus completing the second generation of quarks.

Whilst the confirmation of the charm quark was taking place theorists Makoto Kobayashi and Toshihide Maskawa were already postulating a third generation of quarks9. They found that with only two generations of quarks certain particle interactions could not be fitted into the standard model. However they suggested this would be possible by increasing the number of quark species to six.

The Bottom

The bottom quark b was found at Fermilab near Chicago in 1977. The experiment led by Nobel laureate Leon Lederman was studying electrons and muons produced in the collisions of the primary proton beam of 400-GeV with a fixed target10. By plotting a graph of frequency of occurrence against mass a peak was detected at 9.5GeV see figure 3.

Figure 3

This was the detection of a new particle “upsilon”, the heaviest sub-nuclear particle ever seen11 at the time. This upsilon particle consists of a bottom quark together with its corresponding antiquark so halving this mass of the upsilon gives a mass of GeV for b.

The Top

The final quark to be found was the top quark t. It was surprisingly difficult to find and it was over 15 years from the detection of the bottom quark before the top was finally discovered. Again this particle was discovered at Fermilab but this time in its more recent particle accelerator the Tevatron, to date the world’s most powerful particle collider. The top was finally discovered in 1995 with a mass of 175GeV. This figure is incredibly large and equivalent to the mass of a gold atom – far more than anyone could have predicted. Due to its size, the top’s lifetime is only s and therefore its detection had to be inferred from the jets of particles it decayed into (figure 3).

Figure 313 Violent collision between a proton and an antiproton (center) creates a top quark (red) and an antitop (blue). These decay into other particles, typically producing a number of jets and possibly an electron or positron.

Into the Future

Next year sees the completion of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. This will become the world’s most powerful particle accelerator with maximum collision energy of 1150 TeV12. As a comparison 1TeV is the energy of motion of a flying mosquito which the LHC condenses into a space a million million times smaller than a mosquito. A number of experiments will take place but one of the most important will be to try to find the particle for mass – the Higgs Boson. Without our knowledge of subatomic particles this type of experiment would not be possible and in the next few years quantum theory (including quarks and gluons) will come under its greatest experimental scrutiny yet.

There are also searches at present for a “pentaquark” consisting of 5 quarks – four regular quarks and one anti-quark. Some researchers already claim to have spotted this particle but may other physicists dispute these results. There are many pentaquark searches ongoing at present and it will be some time yet before we know whether they really do exist.

Conclusions

The development of the quark and gluon model since its conception in the 1960’s, has been one of the greatest achievements of modern physics. In a relatively short space of time we have a much clearer understanding of what happens at the lowest levels of the physical world. It is even more impressive when one considers the weirdness of matter at this level (in particular colour confinement) and the ability of theorists to produce elegant solutions to these obscure quantum phenomena.

The size, scale and collaboration of experiments to search for elementary particles has been unprecedented in the world of science and this trend looks set to continue in the near future.

References:

1) Review of Modern Physics Vol 28 No. 3, Electron Scattering and Nuclear Structure, Robert Hofstadter, July 1956.

2) University Physics with Modern Physics, 11th Edition 2003, by Hugh D. Young & Roger A. Freedman, Addison Wesley, 080538684X

3) Http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

4) In search of the ultimate building blocks, Gerard’t Hooft, Cambridge University Press 1997, ISBN 052157883.

5) http://crunch.ikp.physik.tu-darmstadt.de/nhc/pages/lectures/rhiseminar07-08/bauer.pdf

6) http://blueflag.phys.yorku.ca/yhep/colour.html

7) http://prola.aps.org/pdf/PR/v139/i4B/pB1006_1

8) http://scienceworld.wolfram.com/biography/Iliopoulos.html

9) CP Violation in the Renormalizable Theory of Weak Interactions by M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 49, 652 (1973)

10) Elementary-Particle Physics, Elementary-Particle Physics Panel, National Research Council, Published 1986

11) http://www.fnal.gov/pub/inquiring/physics/discoveries/bottom_quark.html

12) http://public.web.cern.ch/Public/Content/CHapters/AskAnExpert/LHC-en.html#q9

13) Scientific American September 1997 The Discovery of the Top Quark, http://www.pas.rochester.edu/~tipton/sa_top.pdf

14) http://www.medbib.com/Upsilon_particle

15) S. L. Glasghow, JIliopoulos, and L. Maiani, Phys. Rev. D 2, 1285 (1970)

16) http://particleadventure.org/frameless/quark_confinement.html

Other Sources Consulted:

Rohlf, James William, Modern Physics from a to Z0, Wiley, 1994

http://www.physics.gla.ac.uk/lattice_EU_network/physics_world.pdf

http://en.wikipedia.org/

The Discovery of Quarks, Michael Riordan, Science, New Series, Vol. 256, No. 5061 (May 29, 1992), pp. 1287-1293 —Preceding unsigned comment added by Icedbun (talk • contribs) 10:08, 29 January 2008 (UTC)

Anomalous photovoltaic effect

My wife created an article - Anomalous photovoltaic effect.

I helped her with Wikipedia technicalities, but i don't know anything about physics, so i can't help her improve it more.

Here are some things with which you might help:

• It needs assessment - is it acceptable per "no original research"? The article is based on her master's thesis, but it is referenced.

• It needs context - at least an opening paragraph. She is not familiar with the Wikipedia style for opening paragraphs and will appreciate help with that.

Thanks in advance. --Amir E. Aharoni (talk) 16:37, 29 January 2008 (UTC)

Reminder of the Philip Greenspun Illustration project

Hi. You may be familiar with the Philip Greenspun Illustration Project. $20,000 has been donated to pay for the creation of high quality diagrams for Wikipedia and its sister projects.

Requests are currently being taken at m:Philip Greenspun illustration project/Requests and input from members of this project would be very welcome. If you can think of any diagrams (not photos or maps) that would be useful then I encourage you to suggest them at this page. If there is any free content material that would assist in drawing the diagram then it would be great if you could list that, too.

If there are any related (or unrelated) WikiProjects you think might have some suggestions then please pass this request over. Thanks. --Cherry blossom tree 16:54, 29 January 2008 (UTC)

Idea: infobox or navbox for history of physics?

I was reading the plum pudding model article, and thought, "wouldn't it be nice to have a little infobox or navigation box summarizing the discovery-sequence of physics? So you would have something like this: {{History of Physics}}

And you could do this evolutionary list for other theories in physics, but this one just seemed to stand out for me. Anyhow, I was wondering what people thought of it, or if it had been thought of before, and shot down for any reason. Rhetth (talk) 02:27, 28 January 2008 (UTC)

Interesting idea. I would title it "Atomic models" or something similar, since "History of atomic physics" is broader than a list of models. Gnixon (talk) 14:32, 28 January 2008 (UTC)

Done. Also, this could be part of a broader physics navbox to include lists of other stepping-stone models and even experiments (such as the Oil-drop experiment, Gold foil experiment), but then aren't these experiments just the evidence for the models they begat? Anyhow, I'm just throwing around ideas for concise, informative, useful boxes of information which could help summarize and educate laypeople (myself included). Also, I'm interested in considering infoboxes[1] which might be a better tool. If you've got an opinion, please opine. — Rhetth (talk) 01:52, 30 January 2008 (UTC)

Update: As I've done some research, there is already a Template:History_of_science, but it is more of a navbox for general histories. Alternatively, there are various timelines, including physics, but these timelines are a bit overloaded with information, quite difficult for a layperson to understand what it's all about. So I'm thinking of something more concise, yet informative. Something which will draw laypeople into the fields of science, piquing interest and allowing a simple introduction to physics, for example. —Preceding unsigned comment added by Rhetth (talk • contribs) 02:54, 31 January 2008 (UTC)

Aurora (astronomy) article

Considering this is B-Class under the grading scheme, please can some experienced editors help me get this to WP:GA status. Thanks, --Solumeiras (talk) 15:19, 31 January 2008 (UTC)