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From: JGA@MIT-MC.ARPA
Newsgroups: net.physics
Subject: Limit to photon frequency
Message-ID: <276@sri-arpa.ARPA>
Date: Fri, 14-Jun-85 15:38:40 EDT
Article-I.D.: sri-arpa.276
Posted: Fri Jun 14 15:38:40 1985
Date-Received: Mon, 17-Jun-85 04:07:48 EDT
Lines: 13

From:  John G. Aspinall <JGA@MIT-MC.ARPA>

    Date: Fri, 14 Jun 85 13:16:23 EDT
    From: John H. Heimann <jheimann at BBNCCY.ARPA>
    To:   physics at sri-unix.ARPA

    	All the discussion of limits to photon energy is predicated on the
    assumption that the limiting factor is gravity.  Wouldn't very energetic
    photons tend to lose energy through pair-production long before they could
    swallow themselves gravitationally?  

Most of the time, yes, but not under all circumstances.  Pair production
requires a nearby mass for momentum conservation.