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Mar11-09, 03:05 PM
Sci Advisor
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Quote Quote by Bob S View Post
how would we determine whether some (half?) of the millions of galaxies we see through the Sloan Digital Sky Survey and other telescopes were made of antimatter?
You can't - the only reason to think they aren't is that you don't see the x-rays from where their anti-interstellar medium meets out interstellar medium.