Re: PBS Einstein's big idea, E=m°c^2
- From: wadexkelman@xxxxxxxxxxx
- Date: 12 Oct 2005 20:01:24 -0700
I can't speak for Newton, but I believe Maxwell's equations are
invariant to motion of the observer because they incorporate a term
called magnetism. Magnetism, as a force, doesn't really have an
independent existence. It "arises" as a consequence of the finite
speed of light, and motion of the charge. The best illustration I have
seen of this is to imagine constant lines of force radiating out to
infinity in all directions from a stationary charge. If you quickly
move the charge to a new, stationary position, new lines of force will
again begin to propagate outward, again in straight lines, toward
infinity. However, the new lines are still continuously connected to
the old lines on a spherically expanding wavefront, sort of like what
you would get if you broke out the center of a wooden wagon wheel, and
displaced the central hub and inner spokes sideways, with rubber
connecting the broken ends of the spokes.
If you examine the direction of the rubber part of the spokes, or
the vector component of the connecting lines of force, you will find a
"force" whose direction and amplitude duplicates what is called
magnetism, a force "induced" by moving a charge from point A to point
B. (If you draw a picture of this and are a perfectionist, remember
that the centers of the two expanding spherical wavefronts are the
first and last positions of the charge, and that it takes time to move
the charge.)
You can also see from this analogy that if the speed of light were
infinite, magnetism would not exist.
Wade Kelman
.
- References:
- PBS Einstein's big idea, E=m°c^2
- From: salmonegg
- PBS Einstein's big idea, E=m°c^2
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