Re: Photon, Momentum, Mass
- From: bz <bz+spr@xxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 1 May 2007 04:17:34 +0000 (UTC)
Tom Roberts <tjroberts137@xxxxxxxxxxxxx> wrote in
news:blyZh.3252$HX7.1200@xxxxxxxxxxxxxxxxxxxxxxxxxx:
bz wrote:
As I understand it, Einstein's 1905 paper was inspired, in part, by the
paradox that a stationary wire and a moving [magnetic] field produced
the same effect[current in the wire] that a moving wire and a
stationary [magnetic] field produced.
You make a small but important error: it was a _magnet_, not a "magnetic
field".
Ah ha! I had missed that point. :)
I see no reason that either magnetic or electric fields can not move.
Because the definition of a field is "a function on the manifold". In SR
the manifold is 4-dimensional spacetime. So a field is necessarily a
function of position and time in that 4-d spacetime. "motion" is defined
as a change in position over time, but in a 4-d spacetime manifold there
is no way to apply that to a field (function of position and time).
I have a bit of a problem 'thinking' in 4-d spacetime. :)
Changes in the field can move, because one can plot the position of a
peak or valley as a function of time, and it is a smooth curve, just as
it would be for a particle in motion.
Good point, or line. :)
EM waves consist of both moving together.
No. EM waves consist of VALUES of both E and B moving together.
I think that Tom's point was that in order to linearly accelerate
electrons (charged particles), we need an electric field
component(charge) behind them.
That was one point. The other is that fields inherently are incapable of
"motion" -- the concepts are incommensurate.
Thank you for taking the time to correct my errors.
I enjoy learning, even if I seem to be a bit slow at times to do so, thanks
for being 'pickey'. :)
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz+spr@xxxxxxxxxxxxxxxxxxxx remove ch100-5 to avoid spam trap
.
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