Re: The Asymmetry of Radiation

RP wrote:
Nice article covering historical approaches to the problem of
radiation.

http://members.optusnet.com.au/~bhkellett/radasymmetry.pdf

I'll stand by my statements that:

1) energy isn't locally conserved, and

2) absorbers aren't necessary because there is nothing to absorb. The
electrons are simply responding to the local retarded field. If it
makes you feel better to call reaction to the ambient field
"absorption" of something, then that is your prerogative, but I
recommend against it, because it's an incorrect application of the
word.

Feynman, in an effort to provide for a time symmetry of em waves, as
presents itself in the field equations, was led to the conclusion
that
if waves can flow backward in time according to those equations, then
there must be charges in the future emitting these "advanced
waves," from which follows that there also must be something there in
the future to absorb the retarded waves. While the latter part of the
statement is just an incidental truth, he however incorrectly
concludes
from this that the future electrons are required to exist before
electrons in the present can even emit em waves. As a premise he
frames it as, "An accelerated point charge in otherwise charge-free
space does not radiate electromagnetic energy." which simply doesn't
follow. Well it actually does follow, but not for those reasons.

This is a bit different than what I claimed previously, which was "An
electron cannot react to any radiation that it emits". Which was
followed with the explanation that this is because there really is
nothing radiated by the electron, it simply jiggles, and distant
electrons jiggle in response at a later time.
That observation is also a famous line of Feynman's, in somewhat
different words.

The "wave" is a trick of Minkowskian space-time, and the success of
that trick relies upon our innate Galilean perspective on the
universe.
Direct particle interaction in Minkowskian space-time was also a
premise of Feynman's, which makes me wonder how absorber theory came
to
be.

I've copied the following from the PDF file above. Some of Feynman's
premises/conclusions:

"(1) An accelerated point charge in otherwise charge-free space does
not radiate electromagnetic energy.

(2) The fields which act on a given particle arise only from other
particles.

(3) These fields are represented by one-half the retarded plus
one-half
the advanced Li´enard-Wiechert
solutions of Maxwell's equations. This law of force is symmetric with
respect to past and future. :

(4) Sufficiently many particles are present to absorb completely the
radiation given off by the source."

(Wheeler and Feynman [1945], p. 160)


Now there really is no logical connection between these views and the
Minkowskian space-time view. Time symmetry is automatically provided
in that context, with no further modification necessary. Perhaps it is
the field equations that need revamping?

How would you revamp them to properly accommodate the asymmetry of
radiation?

I would amend (1) to read "electrons do not radiate electromagnetic
energy, period." Something "between", as he liked to put it, is
old-style thinking, and is even contradictory to his own premise of
direct action at a distance.

I would agree completely with (2), but would add "...through time".

I would amend (3) to read "These fields are full retarded when viewed
in forward time, and also full retarded when viewed in backward time."

I would amend (4) to read "There is no radiation given off by the
source, and thus it doesn't matter how many particles are present to
absorb it. The electron's field is already present at the detector, it
extends forward in time as it extends outward, giving the illusion of
a
propagational delay.

Hmm... But changes in the electron's field are not already present at
the detector. Move the electron and the detector doesn't know it moved
until some time later. I don't see any "illusion" here.

Our present moment is composed simultaneously of an infinite number of
past events.

True. Everything we sense or measure happened in the past wrt to "now".

FrediFizzx

Quantum Vacuum Charge papers;
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps
http://www.arxiv.org/abs/physics/0601110
http://www.vacuum-physics.com

.

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