Confused about electrodymagnetism

Simon Bridge

Feynman pretty much describes everything we do in physics as a trick of calculation. Artithmatic is a trick of calculation, says he.

... and explains why you use the reverse time trick too.

Both authors do it, one casually assigns more "reality" to the model than may be warrented.

However, it may be a reasonable thing to do since, to a photon, no time passes, the particles are in the same place ... so one could argue the other way that there is a real ambiguity about which particle did the emitting and which the receiving. (Indeed both could be the same particle... but that is a different interaction again.) If you swap the roles over, then you've swapped cause and effect ... that's all the "backwards in time" means. Massive observers would still experience things happening forward.

(McIrvin's model of the interaction seems to have more physics in it though.)

Easy there - just because you happen to like the explanation does not mean it is true. All that "we just do the math backward" stuff could just be to stop people who think like you from running away? Or to keep the explanation in topic... McIrvin makes a lot of fudges on that page in the name of keeping things simple.

harrylin

Funny enough, in an earlier version of my reply I gave an example of a misunderstanding based on such a concept, but next left it out as it was not necessary to mention it, since I was asking a question (and next you provided a satisfying answer). Some people "explain" "spooky action at a distance" by saying that for a photon no time passes so that the whole universe can be reached "in no time" (I will not link to one of these sites as it likely would be categorized as "crank site" by the Mentors).

A photon is not a reference system, and no valid or useful reference can be set up in which a photon is in rest.
If you want to discuss or debate that, please go to http://www.physicsforums.com/showthread.php?t=235132 (indeed, the topic of observation at c is in the domain of the relativity forum and that thread is still open).

Note that I came to physicsforums because I would like to make sense of the predictions of QM, in the same way that I already understand SR and GR (no hocus-pokus). Consequently I have every reason to "run away" when people try to sell me ideas that do not make sense to me, and to say "thank you" when they refer to existing sensible explanations. And please don't confuse that with me trying to forbid you to think differently.
At first sight those admitted fudges of McIrvin are very innocent compared to what appears to be a super-fudge of Brown. McIrvin suggests that the trick (not "the model"!) is not OK if one doesn't remember "what's really going on".
Ah OK! No serious intention to link electrostatics to black holes and wormholes.

Simon Bridge

Yeah I've seen those things ... that way lies a minefield.Good grief - well, clearly the case not only can be argued, but is indeed being argued.

Not at all ... it is just that the same charge (hokus pokus) can be applied to GR/SR descriptions, and has been, and in much the same way as you have objected to a possible way that time could work.

There is a trick to getting your mind around GR which you appear to have "got" - the similar trick in QM is to realize that everything is statistical... so "opposite charges attract" on average: there is a chance they could repulse or just do nothing.

When you try to apply that to GR, all those deterministic things are only true on average, you get Field Theory and modern particle physics. But you lose a lot of the no-nonsense aspect of GR ... in a way it is what Bohr and Einstein spent all that ink arguing about isn't it?