From: utzoo!decvax!duke!phs!jfh
Newsgroups: net.space,net.physics
Title: Equivalence of Mass and Energy
Article-I.D.: phs.648
Posted: Sun Aug  8 17:56:57 1982
Received: Mon Aug  9 04:48:57 1982



	I wish to respond to Bob Morris' comments (floyd.428).  First,
however I want to say that the first sentence of my reply ("Surely you jest!!")
was unwarranted, and I apologize to him for it.

	I have no quarrel with either the assertion that the center of mass
does not change during a supernova explosion (within limits of asymmetries),
or with relativistic mechanics. However, I believe that Morris has made some
erroneous assumptions.

	    "Again, during a supernova explosion, the change in
	     mass is zero, both instantaneously and long term."

Consider the fusion of four hydrogen atoms to form helium.  (I know the
overall reaction is much more complicated than this makes it sound, but
please bear with me.  This is an approximation for illustration only.)
The mass of a hydrogen atom is 1.00797 atomic mass units (amu), so four
of them comprise a total mass of 4.03188 amu.  However, a helium atom
has a mass of only 4.0036 amu.  (data from Handbook of Chemistry and Physics,
46th edition)  This leaves a difference of 0.02828 amu, which is converted
to energy in accordance with Einstein's equation.  Surely no one will
argue that the mass of four hydrogen atoms is equal to the mass of one
helium atom.


	    "Photons do just as good a job of causing gravitation
	     as anything else of the same mass."

This is the statement to which my original reply was directed.  Photons have
no REST mass; hence the are able to move at the speed of light.  I believe
that this is a requirement for any entity which can attain this velocity, since
it can be demonstrated that any massive body would require infinite energy
input to reach light speed.  I certainly do not deny that photons possess
energy, and that this energy is equivalent to a certain mass.

	However, while I acknowledge that energy and mass are equivalent, it
appears to me that Morris is claiming that energy and mass are the SAME.
It is not at all clear to me that this is a defensible position. Does a
body composed of a certain number and type of particles become more massive
if it is strongly heated (vibrational energy is presumably also equivalent
to mass)?  The crux of the matter seems to reside in the (paraphrased)
question asked by Mike Knudson (ihnss.126), "Does energy exert gravity?"
Specifically, is it possible for photons to emit gravitons, or is this
property reserved to those particles with non-zero rest mass?

	It is equally unclear that I have illuminated the situation at all.
One could presumably argue in the fusion example that as long as you were able
to contain all the energy in a closed system things haven't really changed.
Does the ability to emit gravitons "define" mass?  Comments on these questions
or on my interpretation of the arguments are welcome.  Although I saw the
announcement of net.physics a few minutes ago, I am also posting this to
net.space also, just in case.


						Fran Heidlage
						duke!phs!jfh