Talk:Classification of electromagnetic fields

message: This article could use some kind of introduction that at least explains the basics to a lay person who is trying to understand if there are different types of electromagnetic fields, and if so, how they differ, and what the practical categories "look like". This article only seems to discuss the maths of it, and leaves me with a lot of questions: Are there static and dynamic electronamagnetic fields? How does the wavelength of the proton relate to the intensity of the field relate to the number of photons? Real world examples? 83.47.201.5 (talk) 04:57, 30 March 2020 (UTC)
thread_title: Simple language

message: I had been monitoring this article, but I am leaving the WP and am now abandoning it to its fate.
Just wanted to provide notice that I am only responsible (in part) for the last version I edited; see User:Hillman/Archive.  I emphatically do not vouch for anything you might see in more recent versions.
Good luck in your seach for information, regardless!---CH 23:03, 30 June 2006 (UTC)
thread_title: Students beware

message: The article says that when Q is non-zero, E and B will be "proportional" in some inertial frame.  Does that mean that they will be aligned (i.e., parallel or anti-parallel) in that frame, but not necessarily of the same magnitude?  Thanks—Quantling (talk) 01:10, 11 September 2010 (UTC)
thread_title:  Non-zero value for ''Q'' = '''E''' · '''B''' 

message: I rewrote this section to be fuller and more logically complete. But still is not satisfying, to me. The basic problem I have with it is that I cannot see the theorem, yet. 
(1) First, it would be nice to know the rank in all cases, including the case of a null bivector. Is the case labelled "non-simple" exactly the case where F is non-simple? Then this should be stated explicitly.
(2) Second, it would be a lot easier to understand if canonical forms (or canonical examples) were given, and the theorem said (or were applied so as to say) that every bivector can be brought into one of these forms. The current version is about 70% of the way there, but it doesn't actually tell you what the bivectors look like. To get there, you have to think it out in your head. Which is to be avoided!
(3) It would be a good idea simply to prove the theorem.
(4) Naturally, it would be nice to amplify the following section (with the E's and B's) so that it connects more strongly with the "classification theorem". The section introduces the invariants |E|^2 - |B|^2 and E⋅B but only fleetingly relates them to the principal null directions -- still without actually giving a concrete form.
Don't |E|^2 - |B|^2 and E⋅B come from a canonical complex structure on the bivectors (given by the Hodge star operator) as the real and imaginary parts of an invariant, complex-valued quadratic form equivalent to z12 + z22 + z32? Or not? It would be nice if this were stated somewhere. Perhaps in the article in bivectors, and referred to  in this article.
(5) A final point -- the direction of my changes has actually exacerbated a problem the article already had, namely a long discursive chatty setup of the math before the theorem is stated. There is something to be said for a crisp presentation of a theorem, followed by the extended explanation. 
178.39.190.161 (talk) 13:22, 1 June 2015 (UTC)
thread_title:  Rewrite of section on "classification theorem"