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From: jhc@mtung.UUCP (Jonathan Clark)
Newsgroups: net.physics
Subject: Re: Quantum electrodynamics and Feynman diagrams
Message-ID: <608@mtung.UUCP>
Date: Thu, 10-Oct-85 14:21:59 EDT
Article-I.D.: mtung.608
Posted: Thu Oct 10 14:21:59 1985
Date-Received: Sat, 12-Oct-85 16:46:04 EDT
References: <326@bcsaic.UUCP>
Reply-To: jhc@mtung.UUCP (Jonathan Clark)
Organization: AT&T Information Systems Laboratories, Holmdel, NJ
Lines: 23
Summary: 

<>
Surely you are mixing up 'real' and 'virtual' photons. In
the case where the two charged particles act upon (repel or
attract) each other a 'real' photon is involved. Hence
energy and momentum transfer are allowed. 'Virtual' photons
are a mathematical tool (so what are 'real' photons,
right?) and only 'exist' for very short periods of time
(too short for God to notice).  It is not meaningful to
ascribe any properties to them, as they are not really
there (by definition). They are used to describe a
mechanism which explains things like pair production and
particle decay (sometimes the 'virtual' ones turn 'real').

Apologies for the extremely sloppy use of sundry terms in
this posting. I'm not trying to be rigorous, just to
enlighten the original poster a bit. Terms which should be
read with a pinch of salt are surrounded with apostrophes.
-- 
Jonathan Clark
[NAC]!mtung!jhc

Everyone was frightened of Doug. Even Dinsdale was
frightened of Doug. 'E used.... sarcasm.