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From: gjphw@ihuxm.UUCP
Newsgroups: net.physics
Subject: Light as the boundary between energy and matter
Message-ID: <939@ihuxm.UUCP>
Date: Mon, 26-Mar-84 22:33:06 EST
Article-I.D.: ihuxm.939
Posted: Mon Mar 26 22:33:06 1984
Date-Received: Tue, 27-Mar-84 01:47:48 EST
Organization: AT&T Bell Labs, Naperville, IL
Lines: 51



   Just to reveal my naivete to this forum, I would like to raise the issue of
 the classification of light (photons).  These thoughts were stimulated by some
 statements made during an anti-creationism presentation that I attended.

   At this presentation, it was pointed out that our traditional means of
 reasoning, through logic and mathematics, require that all entities be
 classified into groups or disjoint sets.  Despite this, nature more often
 displays a continuous distribution of characteristics that can make
 classification difficult.  One example is the archaeopteryx.  This is a
 creature from the late Jurassic period which possessed many skeletal
 characteristics of reptiles but it also had feathers.  Evolutionists might
 label this a transitional species while creationists assign the creature to
 one or the other group (reptile or bird) then criticize evolutionists for
 failing to supporting their theory with a transitional species.  Homo Erectus
 provides another example (is it human or is it ape).

   Anyway, I wondered if this failure to fit a neat classification could apply
 to light as well.  What are the characteristics of matter?  Matter can be
 identified by its locality, rest mass, momentum, and optional electric charge,
 along with a host of quantum numbers.  Anyone got any neat characteristics so
 that matter can be easily and unambiguously identified?

   Next, what are the characteristics of energy?  Surely it is not sufficient
 to say that energy merely lacks the characteristics of matter (does not have
 locality, does not have rest mass, does not have electric charge).  Any ideas
 that would allow me to unequivocally recognize an energy beast if it charged?

   Given these identifying characteristics, it may appear that light (photons)
 serves as a transitional entity.  Photons possess some of the character of
 matter (locality, momentum, helicity quantum number) and lack others (most
 notably, rest mass).  This transitional nature also clarifies the particle-
 wave dualism issue that seemed all the rage from Newton's time until Einstein.
 I have been taught that photons are energy packets that act like matter under
 certain circumstances (energy that looks like matter?).

   At one time, I thought that the emphasis given to the study of light merely
 derived from human psychology.  People, who can, use their eyes as their major
 sense organ (over 90% of most people's sensory input is through vision) and
 light is very important for vision.  However, if light lies at the transition
 between matter and energy, then its study would appear to have profound
 significance for our concepts matter and energy.

   Any thoughts?
-- 

                                    Patrick Wyant
                                    AT&T Bell Laboratories (Naperville, IL)
                                    *!ihuxm!gjphw