Re: the energy

[Leigh Palmer <palmer@SFU.CA>]

Sorry, folks. I'm still catching up.

On 21-Oct-04, Michael Edmiston wrote:

> Prior to Rick Tarara's response (below) I was about ready to ask if
> we've been watching too many movies like "The Matrix."  I guess I'll
> ask
> that anyway.  And I also second John D's closing remark, that it
> pointless to get too hung up on this.
>
> I would like to make a few more comments about the idea of
> inter-conversion and the idea of flow.  I understand the points Jim and
> Leigh have made.  I don't argue, yet I do argue.  The problem is what
> choice of words do we want to use to describe some of the things we see
> (or think we see).
>
> A photon is traveling in some region, and all of a sudden...  poof...
> the photon is gone and in its place we see a positron and an electron.
> We discover this is energy related because not any photon can do this.
> The photon must have an energy of  at least 1.022 MeV which is the
> E=mc^2 equivalent of the rest mass of the positron and the electron.

I certainly dispute that this process can occur. The process you
propose can't have an energy threshold because if it had such a
threshold it could happen in any inertial frame of reference, including
all those frames in which the photon has an energy less than 1.022 MeV.
It is a good example to make my point that in no sense does the photon
(a real entity in my cosmology) *possess* some substantial component
which we call *its* energy. The very fact that its energy could be
different for observers in different frames should raise doubts about
its reality.

Now, it is more conventional to say that the pair production process
you propose can't happen because it would violate the law of
conservation of translational momentum, but as you see it is easier
and, in my opinion, more elegant to prove its impossibility if one is
not burdened with the idea that, somehow, the photon possesses
something real.

(N.B. Two 511 keV photons colliding head on might produce this result,
of course.)

> In a proton-rich nucleus it would be more energetically favorable if
> one
> of the protons could become a neutron, and it will do this if it can
> capture an orbital electron, in which case we have beta decay of the
> electron-capture variety.  However, if the proton-rich nucleus has
> enough energy (compared to the nucleus that would result from
> converting
> a proton to a neutron), it doesn't need to wait for an orbit electron
> to
> wander too close.  It can just make the electron by converting some of
> its energy into pair production.  Of course the nucleus doesn't want
> the
> positron, so it just spits it out, and we have beta-decay of the
> positron-emission variety.
>
> Oh my.  I have committed all kinds of heresy here.  I'm converting
> energy to mass.  Electrons are wandering too close.  Nuclei want or
> don't want things and spit things out.

From a theology web site on denial of faith:

"Mortal sin committed directly against the virtue of faith, and, if the
heresy is outwardly professed, excommunication is automatically
incurred and membership of the Church forfeited."

You may have sinned, Michael, but your sin is venial, and if you have
told your students already that this is merely a useful figure of
speech, those capable of understanding will not be harmed. There is no
sin committed against those who are invincibly ignorant, so you are
absolved. I use the idea of energy transfer, etc., myself. It is
certainly a useful way to describe Nature, provided one does not lose
sight of its limitations. I am suggesting here that a significant
*caveat lector* (or *caveat auditor*) be included in the curriculum at
some early point in the university physics course, and preferably on
more than one occasion.

> I understand the need to be careful with our words.  But let's not get
> to the point that we can no longer communicate.  Did my paragraphs
> about
> pair production communicate the idea, or are they so flawed with
> imperfect notions of physics that it would be better that I never said
> them?

To the contrary; you have provided me with an excellent illustration of
the unreality of the energy and the error to which one may be led by
thinking otherwise. I had not thought of this one before, and I thank
you for it.

> Michael D. Edmiston, Ph.D.
> Professor of Physics and Chemistry
> Bluffton University
> Bluffton, OH 45817
> (419)-358-3270
> edmiston@bluffton.edu

Leigh