From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Defining Photons
Date: 26 Jul 92 20:18:23 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
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Keywords: Relating photons E=MC^2 criticism
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In article <3942@cruzio.santa-cruz.ca.us>, snarfy@cruzio.santa-cruz.ca.us writes...
> 
>       If you are a college professor , the taxpayers  or  students  pay
>       you to enlighten and clarify issues pertaining to your specialty.
>       Why then have you not yet found a word other than ``particle'' to
>       describe  that  which has no mass , to differentiate it from that
>       which does?.  I think it's because some of you  would  prefer  to
>       confuse people rather than teach them. The photon, as a concept ,
>       would  be  more accurately described as a ``phenomena'' given the
>       difficulty  you  have  manipulating  it  the  same   way   as   a
>       ``particle''   mathematically.  (multiplying  by  zero  ,for  one
>       thing).
> 
>      I find it odd that you have a job.
> 
>          Jim Ostrowski

Sorry, Jim.  No one is paid to enlighten you.  That's your problem.  If you
can't yet understand why physicists insist on calling photons a particle
then perhaps you should examine your own shortcomings rather than taking
foolish potshots at someone who was obviously willing to take the time
to engage you in discussion on the question.  Isn't this what you wanted
in the first place?

Now for some physics:  Photons (and other bosons) are particles.
But they *do* have an important property which distinguishes them from 
other particles.  The question is - what does the classical limit of these
things look like?  For most particles, say an electron, you approach
the classical limit by increasing the energy of the particle - putting
it in a higher quantum level.  For photons, you don't increase the energy
of a single particle,  but rather increase the occupation number of a given
energy state.

Photons behave classically when there are alot of them around.  Electrons
behave classically when one of them is at high energy.  This is a fundamental
difference, which emerges directly from the different methods of quantization
used for fermion and boson fields, and directly leads to the dramatic
classical difference between EM fields and lumps of matter.  But in the
quantum regime this distinction blurs considerably, leading physicists to 
class all these objects - photons and electrons and everything else, together
as particles.

Notice that masslessness have nothing to do with these questions.  It a matter
of spin, not mass.  Massive bosons, such as the W or Z, if we were able 
to make enough of them to produce a semiclassical state, would behave much
like photons, not at all like electrons.  

-Scott
--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver
Newsgroups: sci.physics