(2 of 2)
If there are galaxies and anti-galaxies, there must be some force that has separated matter and antimatter. Anti-gravity might do it (the two kinds of matter repelling each other), but Dr. Segrè thinks not. He and many of his colleagues are looking for another segregating force. He admits that it will be hard to find, but he points out that it will also be hard to prove that antimatter was not created along with ordinary matter. Both are equally stable when left to themselves, and the physicists' cherished laws of symmetry suggest that they should have been created in equal amounts.