Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!vax135!cornell!uw-beaver!tektronix!hplabs!sri-unix!FAILOR%LLL@LLL-MFE.ARPA From: FAILOR%LLL@LLL-MFE.ARPA Newsgroups: net.physics Subject: Re: Do Positrons Have Negative Mass? Message-ID: <553@sri-arpa.ARPA> Date: Thu, 19-Sep-85 15:20:00 EDT Article-I.D.: sri-arpa.553 Posted: Thu Sep 19 15:20:00 1985 Date-Received: Mon, 23-Sep-85 00:26:36 EDT Lines: 25 From: Bruce Failor To: Physics@SRI-UNIX.ARPA In-Reply-To: Message from "Physics@SRI-Unix" of Thu 19 Sep 85 00:50:28-PDT By the way, does anyone know how good a vacuum intergalactic (and interstellar) space is, say in protons or electrons per cc? According to what I have heard, it is mainly H. One of the professors on a friend's oral examination committee asked a question about the time of arrival of high energy photons. The prof maintained that the arrival time was a function of energy with a threshold at the energy required to produce an electron-positron pair. If pair production is the process that causes the lag, there needs to be protons or other nuclei available to allow for momentum and energy conservation. He stated that the high energy photons produce pairs which in turn annihilate which in turn produce pairs, etc. Since matter travels at less than the speed of light, the photons that spend the most time as electon-positron pairs will experience the most time lag. Has anyone else heard of this/know of references to actual measurements? Bruce Failor ------- Brought to you by Super Global Mega Corp .com