Paul Stowe wrote:
[about electrons as point particles]
Only an idiot would 'actually' think that particles have
zero volume. Try calculating the mean free path of point
particles. If one does they'll find it to be inifinite,
because zero volume particles result in zero area
cross-sections and without any cross-sectional area...

Only an idiot would 'actually' think he could make sensible statements
about physics while remaining willfully ignorant of the last 100 years
of physics.

In particular, modern physics (QED and the standard model) models
electrons exceedingly well as point particles. No measurements made to
date are inconsistent with that.

One can indeed calculate the mean free path of these pointlike electrons
in matter, and the results are definitely not "inifinite", and are
consistent with measurements. The mean free path of electrons in matter
depends strongly on their energy (in the rest frame of the matter in
question). Electrons are well known to lose energy while traversing
matter, and to multiple scatter; with sufficient energy they generate
electromagnetic showers.

There are numerous other particles we currently model as pointlike
particles (quarks, gluons, leptons, Higgs). None have infinite mean-free
path in matter, because they all couple to at least one field. Neutrinos
come closest to his guess above, and neutrinos have a mean free path in
rock of about a lightyear (!) -- still not infinite, and observed by
MANY experiments.


Tom Roberts