(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?
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,
For Ask an Astrophysicist