Re: antimatter and mass

Hi Koa,

First of all, please allow me to apologize for the delay in responding to your question; I was on a short trip when this question came in. Circumstances conspired against us but let's get right to it now. Those are very good questions you asked but I'm surprised that you're learning about these things in chemistry class, instead of a physics class. But I guess things have advanced quite a bit since I was struggling through high school!

Okay, on to your first question. Antiparticles definitely have a "positive" mass. I'm not sure what a "negative" mass would be at all but, in essence, antimatter particles have the opposite charge but the same mass as their "regular" matter analogs. Now, as to the conservation of mass in positron emission: this has to do with Einstein's famous mass-energy relation, namely, E=mc^2. Some of the mass of nucleons is "used" to help keep the nucleus together; i.e., it's used as binding energy. This is explained much more fully at this site.

Your other question is a lot harder to answer satisfactorily. Basically, it comes down to some very messy and very complicated implications of quantum mechanics. These essentially say that even vacuums are subject to certain quantum fluctuations. These fluctuations are what cause the creation of matter/anti-matter pairs of particles. The weird thing about this quantum effect is that this happens in completely empty space with nothing around... not even gamma rays! It's only when these pairs of particles (e.g., positrons-electrons) meet that they annihalate one another and produce energy (usually gamma rays). Of course, gamma rays that are energetic enough (> than about 1MeV) can also be made to produce electron-positron pairs and so these two processes are considered equivalent.

I hope this helped with your questions and that you continue your search for answers. If you have any further questions, please don't hesitate to drop me a line here or at science@zentropy.com and I'd be more than happy to go into this in more detail with you.

Best regards,

Rick.