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The Question

(Submitted March 05, 1998)

I read in a text somewhere that a theory exists that at the moment of the Big Bang, there was a powerful expulsion of matter and antimatter in opposite directions at enormous speeds. Doesn't this mean that, also in theory, there are antimatter galaxies somewhere? How well respected is this theory in the scientific community, and what do you personally think of it?

The Answer

You are correct in that we do believe that equal amounts of matter and anti-matter were created in the big bang. However today we see no strong evidence for anti-stars or anti-galaxies. When matter and anti-matter meet they turn into energy and we know what range that energy this energy should be seen. Although some anti-matter events are seen, they are not enough to assume that half the cosmos is anti-matter. The amount of anti-matter observed can be explained by processes that have occurred since the big bang.

So where is the anti-matter? There is no reason to think that they could have/would have separated at the time of the Big Bang, like you suggested. One theory states that anti-matter decays slightly faster than matter. Before the matter and anti-matter had a chance to recombine, some of the anti-matter decayed. So when they recombined, there was some matter left over which formed our universe.

Hope this helps,

Jeff Silvis
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