Re: Radiation Pressure

[Leigh Palmer <palmer@sfu.ca>]

> Hi all-
> 	Leigh Palmer writes:
> **********************************************************
> One might make the observation that light has no mass, therefore it
> has no electric charge because we have always observed charge is
> associated with particles that have mass. Reasoning of that sort
> closes the mind to the objective consideration of the properties of
> an as yet unobserved phenomenon.
> **************************
> 	While I can't disagree with the statement as it stands, I
> take exception to the "because we have always observed" part.  I
> have great difficulty with the concept of a massless charged
> particle.  That's because, as pointed out in the older E&M texts
> (see Heitler, for example) a localized charge has inertia.

Even light has inertia. Gedanken experiment: Take a mirrored box
full of dark. Measure its inertia. Fill it with light. Measure its
inertia again. Result: inertia (mass) has increased! You are correct;
we all have great difficulty with the concept of a massless charged
particle because we don't know of any. I'm afraid I haven't a copy
of Heitler at hand, but I'll guess what he points out is that when
one accelerates a charge it does work against "radiation resistance"
which is functionally inertia-like, since a mass also resists
acceleration.

Just extrapolate from muons and electrons to massless charged
particles. Never mind that they may not have been seen; I'm only
asking yout to conceive of them. You *can* do that.

> Thus,
> the "classical radius of the electron" is the radius of a sphere
> containing the charge on an electron, such that the sphere has
> inertia equal to the electron mass.

That's correct, and we know empirically (from Coulomb scattering
experiments) that the electron is a point charge a whole lot smaller
than that. If one extrapolates its electric field energy density to
zero radius the total energy does not converge. If one merely takes
it down to the radius to which the field is known to be Coulombic
then the total field energy exceeds mc^2.

> 	It is indeed fortunate that the "high temperature vacuum"
> of QCD, where all the particles are massless, is broken by the Higgs
> mechanism so that at low temperature (or, in "real life") all them
> charged guys pick up mass.  This fact enables me to live at peace
> with the universe (so far).

Jack, if that's "real life" to you we live on different planets. The
accommodations I have had to make to preserve my grip on reality are
large, but they do not yet subsume the Higgs mechanism or inflation.
I haven't yet come to conceptual accommodation with the nonrelativistic
quantum mechanics. There are guys out there who say they understand it
and then mouth nonsense about collapsing wave functions and other
Copenhagen nonsense. There may be hope for me yet, however. We have a
bright, young theoretician here called Howard Trottier who gave an
outstanding talk a couple of weeks ago about his area, lattice QCD. He
managed to turn on a few lights for me. Another Gegenbeispiel to
invalidate the superannuated canine conjecture!

Fortunately I am willing to go to my grave not knowing everything. I
will probably never be at peace with the universe as we describe it.

Leigh