Re: Various questions
- From: Oh No <NotI@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 10 Apr 2007 14:33:49 +0000 (UTC)
Thus spake "G. Ralph Kuntz, MD" <grk@xxxxxxx>
I am NOT a physicist, but I am interested in particle physics.
Does the electron have a size or is it a "point" object? If so, its
density should be infinite since it has mass in a zero volume.
This is very much a matter of interpretation. It always surprises me
when field theorists, who seem to disregard interpretational and
foundational issues as not physics and not sensible, give field
theoretic interpretations which don't make sense in terms of what is
known of foundations of quantum mechanics.
In the orthodox interpretation of quantum theory it only makes sense to
talk of an observable quantity when a measurement is done. From that
point of view the electron is sizeless. The fundamental interaction
between electrons and photons obeys a locality condition, showing that
when an electron is confined to a particular position (e.g. by
measurement) then the interaction at a photon must be at that position.
While perfect confinement to a point is not possible (because of energy
considerations) it seems to me the best way to interpret this condition
is to say that an electron is point-like. I use point-like, rather than
point, because the position of a point is generally thought to be well
defined, whereas the position of an electron is not.
How do forces work at the sub-atomic level? If two electrons approach
each other, I understand that the like negative charges repel each
other, but what imparts the "thrust" to move them apart? Or an
electron and a proton - what causes them to move toward each other? I
know that the standard model says that the particles exchange photons,
but why does this exchange cause them to move toward or away from each
other?
Because position is not well defined a photon can be exchanged taking
negative momentum between an electron and a proton. One way to think of
this is to recognise that the force between an electron and an electron
is repulsive, as one would expect. In the Feynman-Stuckelberg
interpretation a positron is an electron going backwards in time.
Reversing time for one particle also reverses the direction of the
resulting force, so that there is an attractive force between particles
of opposite sign.
Do the photons "bend" space - as in general relativity?
qed uses flat space, but the energy in photons does bend space in
general relativity. We don't have a unification of these theories.
Is mass quantized? When new virtual particles are created, say an
electron and anti-electron (positron), why do they always mass exactly
the same amount and not 99% or 102% of the "standard" mass?
Every electron is identical to every other. Mass is a fundamental
property of an elementary particle. For virtual particles one has a
choice of definition. Either one must say mass is "off mass shell", or
one must say energy is not conserved between measurement. The former way
of describing things is normal, but my own interpretation is that the
latter is more accurate.
I am reading Brian Greene's book "The Elegant Universe" and it is
leading to more questions than answers. Good book, though!
String theory is based on assumptions about the mathematical structure
of quantum field theory which I do not believe can be justified from a
study of foundations of quantum theory.
Regards
--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email
.
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