I suspect you are correct -- anything on the boundary would have disappeared within microseconds, hence the possibility of pretty darn empty space for mucho light-years between matter & antimatter. However, this doesn't eliminate the possibility of relatively large pockets of antimatter. Even if the ratio of anti-matter to matter is only 1%, that's one heck of a lot of anti-matter, including the possibility of entire stars/galaxies of the stuff. The only thing I could think of would be a telescope sufficiently powerful to see a CPT experiment in action, but what would be necessary to convince one's self that it was the same experiment that one could conduct locally? I.e., since you don't have physical access to the particles involved in the experiment, how can you tell whether they are made of matter or antimatter? In other words, we've just begged the question. A related question: how close does a particle have to get to its anti-particle before it annihilates it? E.g., if one has a proton & an anti-proton, what length scale is safe, and what length scale is unsafe? I assume that uncertainty is at work here, so there is some non-zero probability of annihilation that goes up as the particles get closer? At 12:06 PM 6/30/2010, Joshua Zucker wrote:
On Wed, Jun 30, 2010 at 11:27 AM, Henry Baker <hbaker1@pipeline.com> wrote:
"How do we know whether something we're looking at in a telescope is matter or anti-matter?"
I think the main answer is that space isn't empty, and if there were a boundary between matter and antimatter anywhere we would see all the gamma rays coming from the annihilations at the boundary.
There aren't many other asymmetries!
--Josh