Cyan comments on Open Thread: March 2010 - Less Wrong

5 Post author: AdeleneDawner 01 March 2010 09:25AM

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Comment author: Cyan 04 March 2010 02:43:30AM *  2 points [-]

the 4/3 claim for electro-magnetic mass

Wikipedia points to the original text of a 1905 article by Poincaré. How's your French?

Comment author: wnoise 04 March 2010 03:02:43AM 2 points [-]

Thanks. It's decent, actually, but there's still some barrier. Increasing that barrier is changes to physics notation since then (no vectors!).

Fortunately my university library appears to have a copy of an older edition of Rohrlich's Classical Charged Particles, which may help piece things together.

Comment author: Cyan 04 March 2010 03:26:46AM *  2 points [-]

Petkov wrote:

Feynman [wrote], ”It is therefore impossible to get all the mass to be electromagnetic in the way we hoped. It is not a legal theory if we have nothing but electrodynamics” [13, p. 28-4]; but he was unaware that the factor of 4/3 had already been accounted for [10]).

It's worth noting that Feynman's statements are actually correct. According to Wikipedia, the problem is solved by postulating a non-electromagnetic attractive force holding the charged particle together, which subtracts 1/3 of the 4/3 factor, leaving unity. Petkov doesn't explicitly say that Feynman is wrong, but his phrasing might leave that impression.

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