Re: Particle Visualization



Monitek wrote:
> "PD" <TheDraperFamily@xxxxxxxxx> wrote in message
> news:1117573328.198051.145710@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >
> >
> > Monitek wrote:
> >> "PD" <pdraper@xxxxxxxxx> wrote in message
> >> news:1116642764.925698.47790@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> >
> >> > Nick wrote:
> >> >> PD wrote:
> >> snip-----------------------
> >> >> > Small detail. Electrons and positrons have electric charge. Photons
> >> >> and
> >> >> > neutrinos do not.
> >> >>
> >> >> Photons are not electromagnetic?
> >> >>
> >> >
> >> > yes but they are not charged. which means there is no trilinear photon
> >> > coupling.
> >> >
> >> > PD
> >> >
> >> > [snip]
> >> >
> >>
> >> If photons are not electromagnetic:
> >
> > Reading comprehension problem. Photons are electromagnetic, but they
> > are not charged.
> >
> >>
> >> a) What are photons?
> >
> > The carriers of the electromagnetic interaction. The carrier does not
> > need to carry charge itself. The charge identifies the *strength* of
> > the coupling between a (fermion) particle and the appropriate (boson)
> > carrier of the interaction.
>
> Are ther 2 kinds of photon one for positive charge and one for negative
> charge?

No, there is one kind of photon, the same for positive and negative
charge.

> Do the photons travel at the speed of light?

Yes.

>
> > Think of it as how often the vertex
> > happens.
> >
>
> I do not understand the relevance of this statement.

I wasn't sure you would. It's a reference to Feynman diagrams. A
Feynman diagram is a little schematic of an interaction, where the
different parts of the schematic represent terms in an algebraic
expression which allows you to calculate the rate at which that
interaction occurs. For example, a diagram like a "Y" might have for
the three legs an incoming electron, an outgoing electron, and an
emitted (or absorbed) photon, and the point where the emission (or
absorption) occurs is at the junction of the "Y" -- the vertex. The
term corresponding to the vertex is proportional to the charge of the
electron. The stronger the charge is, essentially, the more frequently
the vertex will occur during an electron's path through spacetime.

Note that the charge is carried by the electron in this case, which is
codified in the rule that vertices happen on electron lines but never
on photon lines. You can't have a "Y" with just photons on the three
legs. On the other hand, the statement that the electron has charge
means *nothing more* than the fact that it does have vertices where
photons are emitted or absorbed. That is, the answer to the question,
"What is charge, anyway?" is simply that it is a flag that the particle
that bears it participates in such interactions.

>
> >>
> >> b) From what are the electromagnetic properties of EMR produced?
> >
> > Too vague. I don't know what you mean by "electromagnetic properties".
> >
> >
>
> One can measure the electrostatic field associated with EMR.
> One can measure the magnetic field assoiated with EMR.
> "electromagnetic properties" is a phrase which encompasses both properties.
> My question is : Where do the electromagnetic properties associated with EMR
> arise from?
> If the photon has no charge (I note the word 'need' as used above leaving
> open the option for a charged photon), then the "electromagnetic properties"
> must arise from something else. If so what could that something else be? On
> the other hand if the photon is charged then one does not have to look for
> something else to derive the electromagnetic properties of EMR.
>

No, and this is simple to explain. You are under the impression, it
appears, that the only sources of electric and magnetic fields are
charges. This is not so. If you open a textbook to the chapter on
Faraday's law and Maxwell's equations, you will see that there are
other sources for electric and magnetic fields; namely, a changing
magnetic field is a source of an electric field, and a changing
electric field is a source of a magnetic field. This, in fact, is the
key thing that lets electric/magnetic fields propagate *together*
through space, without carrying charge with them. The fact that the
fields are periodic (oscillating) is central to this, because
oscillating fields are constantly changing, which is required for them
to continue to feed each other.

The fact that there are non-charge sources for electric and magnetic
fields came as quite a surprise to Faraday, but experiments don't lie.
Likewise, the fact that the mathematical solution to propagating,
chargeless fields happened to propagate at a speed that was numerically
close to the measured speed of light came as quite a surprise to
Maxwell, but it too was verified later in experiment.

This sequence of stunning revelations completely changed everything in
physics. Indeed, of the four fundamental interactions, the
electromagnetic interaction is the *only* one that we freely exploit at
will. (Some will include gravity in that category, but if we didn't
happen to have a fairly huge source of a gravitational interaction
nearby, it'd be useless to us.)

PD

.

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