Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA
Path: utzoo!linus!philabs!cmcl2!seismo!brl-tgr!gwyn
From: gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>)
Newsgroups: net.physics
Subject: Re: A question about mass and energy
Message-ID: <49@brl-tgr.ARPA>
Date: Sun, 21-Jul-85 00:55:43 EDT
Article-I.D.: brl-tgr.49
Posted: Sun Jul 21 00:55:43 1985
Date-Received: Mon, 22-Jul-85 04:18:54 EDT
References: <378@sri-arpa.ARPA> <11562@brl-tgr.ARPA> <1014@mhuxt.UUCP>
Organization: Ballistic Research Lab
Lines: 18

> > Indeed, a propagating plane electromagnetic
> > wave violates both but does carry energy as given by its Poynting
> > vector.

>     A propagating electromatic wave -- an electric field and a
> magnetic field chasing each other through free space -- a 'photon', right?

No.  I was taking about something much "bigger" than a photon.

> > In particular, the electromagnetic field is just a
> > cloud of "photons", which are particles, and subsidiary particles.

>     What about the electromagnetic field which makes up a photon?  How
> can this be 'just a cloud of photons'?

Every elementary particle can be thought of as "made" of an infinite
number of others (subject to definite rules!).  Again, I was talking
about a macroscopic E-M field, though.