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From: Cramer%CSL60%ti-csl.csnet@CSNET-RELAY.ARPA
Newsgroups: net.physics
Subject: Re: Do Positrons Have Negative Mass?
Message-ID: <551@sri-arpa.ARPA>
Date: Tue, 17-Sep-85 11:16:00 EDT
Article-I.D.: sri-arpa.551
Posted: Tue Sep 17 11:16:00 1985
Date-Received: Sat, 21-Sep-85 04:31:41 EDT
Lines: 14

From:  Nichael 

>>How can we tell that Andromeda, say, is composed of matter and not
>>anti-matter?  What observational differences would there be between a matter
>>galaxy and an anti-matter galaxy?

The space between the Milky Way and Andromeda isn't a perfect vacumn.  Were
Andromeda made of anti-matter, there would have to be matter/anti-matter
frontier somewhere between us. I don't have any numbers to back this up,
but it seems that the resulting spike in the background radiation at
~1MeV would be easily observable.

						NLC
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