|MadSci Network: Physics|
Hello, Albert - No, as far as we know, antimatter is affected by gravity in the same way as matter. This is inherent in the equations that describe particles and antiparticles (there is only one value for the mass, and it's a positive number), and also in the equations of general relativity. There was an experiment done to test this, but it was inconclusive (these experiments are *very* hard, as the only antimatter we have created in the laboratory is single particles, and the gravitational effects are tiny). There is no reason to think that the equations are wrong, and a lot of reasons to thing that they are right (since they work so well at predicting so many phenomena), but it would be nice to test this particular prediction directly. Here are some Web pages about antimatter: http://phyhp.phy.ncku.edu.tw/chinese/uw_physics/grav_antimatter.html Does Antimatter Fall Up or Down?, from the Physics FAQ. http://pdg.lbl.gov/cpep/antimatter.html The antimatter page from the Particle Data Group's particle physics tutorial. If you are interested in particle physics at all, this whole tutorial is excellent! http://image.gsfc.nasa.gov/poetry/ask/a11025.html Does Antimatter Produce Antigravity?, from Ask the Space Scientist. It is in any case not likely that antimatter galaxies exist; galaxies are not all that far apart from each other, and collide frequently (over their life cycle). If a matter and antimatter galaxy were to collide, we would see annihilation radiation, which has not been observed. For more information, see the Cosmology FAQ: http://donald.phast.umass.edu/~linder/faq.html
Try the links in the MadSci Library for more information on Physics.