Main Question or Discussion Point
This thread was snipped and moved from the thread "conflict between electrodynamics and classical relativity" orignally posted by michael879.
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dunno specifically what you mean by the "first principle of SR". if you mean that the laws of physics are exactly the same for any inertial observer, i would agree and say that this is a fundamental axiom. but if it is that the speed of electromagnetic waves(a.k.a. "light") are the same for any unaccelerated observer, i would say that given the axiom that the laws of physics are the same, then it is that Maxwell's equations are those laws of physics that, if identical in every respect for any and every inertial observer, is the principle from where you deduce that the speed of light in vacuo is the same for every observer.I do not agree that the first principle of SR can be deduced from Maxwell's equations.
No. We're not talking about moving objects or collisions but light being emitted. In the frame of the guy lighting the candle Maxwells laws work and the speed of the light is c in that frame.Do you understand that in general, when calculating the behavior of moving objects, there is no need to use multiple frames?
but that concept of "aether" was an unnatural workaround or "kludge" concocted so that the pre-Einstein guys could get a grip on how E&M was propagating. they fully thought that the velocities added in such a way that the two observers would have to observe the speed of that beam of light to be different, just as you and i would if you, traveling in a 100 km/hr vehicle tossed out, in front of you, a ball at a speed (observed by you and others in your vehicle) at 40 km/hr. i, standing at the side of the road, would observe that ball to move at 140 km/hr. they thought that logically, it would be the same for light, but the only way for that to happen is for there to be a stationary frame of reference for light to travel in (and the name for that was the "aether") and that was a concoction, a kludge. all's Einstein did was toss that kludge out and then ask, "if both observers are absolutely equal qualitatively, and observe the same speed for that propagating EM wave, what parameter (that was thought to be invariant) must give for that to happen", and the answer he came up with is time (or rate of clock ticking) and length colinear with the direction of motion, and inertial mass (defined to be momentum divided by velocity, and not to be confused with invariant mass), and energy, etc. all of those things have to be observed differently for the two different observers in order for them to perceive the speed of propagation of the EM wave to be the same.But you guys are using post-Einstein ideas, mainly 'no aether'.
We're talking about moving charges. Do you think Maxwell's laws are incapable of predicting the speed of electromagnetic waves emitted by an oscillating charge whose average position (i.e. not worrying about the small motion caused by the oscillation) is moving in the frame you're using (the frame where you assume Maxwell's laws are correct), without transforming into the frame where the charge's average position is at rest? Do you think that in order to calculate the magnetic field of a moving charge, you need to transform into a frame where it's at rest? Maxwell's laws work just like classical dynamics or every other set of laws in physics--you never need to switch reference frames to predict what will happen, although in some cases it might make the math simpler.No. We're not talking about moving objects or collisions but light being emitted.
In relativity, yes. But before relativity, physicists imagined that Maxwell's laws wouldn't work in that guy's frame unless he was at rest relative to the aether.Mentz114 said:In the frame of the guy lighting the candle Maxwells laws work and the speed of the light is c in that frame.
cross product of vectors (specifically in Maxwell's Eqs. the cross product with the "del" or "nabla" operator which defines the "curl" operation).In Maxwell laws, what does x mean ?
probably there are posts in the past here that would help. i dunno.Supose a photon emitted by an atom.
The atom is moving in relation to other atom buts it is at rest respect to
The photon is an entity different from the atoms ( It has energy, wrote
The photon ( or the wave ) is moving in relation to what ? To itself ?
May be the atoms dissapear after the photon is created.
I think this is basic for all the argument of ( special ) relativity
and I wish to find a link where this is explained ( whithout complex
If somebody could help me, thanks.
Aren't you disagreeing about Maxwell's laws, though? You seemed unconvinced that Maxwell's laws could give you the speed of an electromagnetic wave from a moving emitter without the need to transform into the emitter's frame, and you also seemed unconvinced that Maxwell's laws demand the speed of the wave from a moving emitter would be c in any frame where these laws hold.Guys, please lay off me ! I'm not disagreeing with anything you say. We were talking about how these ideas evolved - I hope there's no argument about relativity going on here.
It would greatly enhance my education to see this properly demonstrated - with a luminiferous aether and pre-SR concepts.Posted by JesseM
Maxwell's laws demand the speed of the wave from a moving emitter would be c in any frame
Maxwell's laws are just defined by a set of equations (relating the electric field, the magnetic field, and the distribution and motion of charge), they have nothing to do with whether you believe in aether or not. The aether concept is just the idea that these equations are only obeyed in the rest frame of the aether, and in other frames electromagnetism would obey different equations (Maxwell's laws modified by a Galilei transformation). Relativity says that these equations are obeyed in every inertial frame.It would greatly enhance my education to see this properly demonstrated - with a luminiferous aether and pre-SR concepts.