Talk:Elementary charge

I would suggest that this article is removed because it will cause too much confusion. Since the discovery of quarks it is known that the electron charge is not the elementary charge of nature even though it remains a very useful quantity and outside particle physics is the smallest charge you will encounter. However calling it the elementary charge is wrong but describing 1/3e as the elementary charge will probably be confusing without a lot of discussion. Roger Moore 22:53, 11 November 2007 (CST)

• I understand that quarks are never free, so that the elementary ( = proton) charge is the smallest entity of free charge found in nature? Further, I would not delete this article, because the concept and name "elementary charge", although it may be a misnomer, is still ubiquitous in tables of fundamental physical constants [e.g. Physics Today, 56(8), p. BG8, (2003), http://iupac.org/goldbook/E02032.pdf and http://www.euronuclear.org/info/encyclopedia/e/elementarycharge.htm ], textbooks, and such. Why don't you add a paragraph with the latest particle physics views on the quark charge? It is not so difficult to understand, because everybody knows that atoms were once thought indivisible, and with higher observational energies they turned out not to be so. The same for atomic nuclei. Why would the elementary charge not show the same behavior (and still keep its name, like an atom is still called an atom)?--Paul Wormer 01:36, 12 November 2007 (CST)

• Generally quarks are not free but there is one known and one possible exception. The top quark decays too rapidly to hadronize so it does decay as a free quark (which is why it is interesting) and at very high energies a new state of matter, called the Quark-Gluon plasma may exist in which the quarks will likely have enough energy to be free. However I think the term elementary charge is going out of fashion because it is technically (although perhaps not practically) incorrect. The particle data group, for example, use the term "magnitude of electron charge" (W.-M. Yao et al., J. Phys. G 33, 1 (2006), http://pdg.lbl.gov/2007/reviews/contents_sports.html#constantsetc). I also checked a couple of the first year physics texts we used (Walker plus Cutnell and Johnson) and again they refer to it as "electron charge". Given that the term "elementary charge" does appear to be in use still in some circles I agree that the article should remain and I'll take up your challenge to add the particle physics background! Roger Moore 22:32, 12 November 2007 (CST)

• Just finished the edit so please look it over. My feeling is that, subject to your edits, I don't think there is much more to say on the subject so perhaps we should submit it for approval? Roger Moore 00:08, 13 November 2007 (CST)

The article is nice now, except for "some current literature". In my view the CODATA and IUPAC publications have lots of influence. On p. 5 of the very influential book of Jackson (Classical electrodynamics) we find "elementary charge" and I can quote many more sources. So I scratched "some". But to emphasize your point (which I of course agree with) I added "more properly". A thing that started to intrigue me during this discussion, and you will know the answer: why does a proton (3 quarks) have the exact same absolute value of charge as the electron (a lepton)? Are there any theories about it? About approval: do you have an editor in mind?--Paul Wormer 02:24, 13 November 2007 (CST)

Thanks - I definitely like your change. I agree with your points about IUPAC and CODATA but I would have though Jackson was old enough (at least the 1st edition) that quarks would have been very new at the time. Although 1974 is quoted as the date of the discovery it was several years before people were really convinced. Regarding the charge balance I can answer some of it. The global gauge symmetry of QED requires conservation of electric charge. Hence if we assume the universe started electrically neutral we must have an exact charge balance now. This is enacted down to small scale because the EM force is so much stronger than gravity and also has no range limit so any charge imbalance would be neutralized quickly. As to why the quarks have precisely 1/3 or 2/3 the charge on the electron nobody knows. I know of no reason why quarks could not have have +1e (up-like) and 0e (down-like) just like the leptons. I suspect there is a reason but I have seen no theories which even attempt to explain it. We do have some insight into why there have to be three generations (needed to allow a difference between matter and anti-matter) but not a real explanation. String theory might have some insight but I'm not a string theorist. I'll look into the approval process since I have not tried it before and I'll also try ot find a suitable editor, assuming that is needed. I think the approval process will send an email out to all editors - I'll know since I am an editor but obviously can't approve this particular article since I helped to write it. Roger Moore 11:36, 14 November 2007 (CST)