I’ve heard this claimed in some SF stories, but I’m not so sure it’s true, assuming we’re talking about anti-protons. First there’s the issue that antiprotons don’t annihilate directly into energy (because they’re composite objects made of quarks), they go through intermediate reactions which produce various mesons, etc. Secondly, if an antiproton collided with a nucleus of any element other than hydrogen, the energy released would be more than the total binding energy of the entire nucleus; result, nucleus blasted into fragments, including presumably some high-energy neutrons and unstable isotopes. Lastly, even pure gamma rays can in some instances pump a nucleus into an unstable state that either transmutes or rereleases gamma radiation with a certain decay rate.
Now maybe if you could arrange for your antiprotons to annihilate mostly with protons (liquid hydrogen or a hydrogen-rich compound like water or polyethylene) the difficulites listed might be minimized. Has anyone done some research on this?
Yeah, I’d say that it would be proportionately a lot cleaner than any A-bomb per blast payoff, or H-bombs, (which would probably pump out HUGE amonts of alpha particles, since that’s basically the end product of a basic fusion reaction,) but not nearly as clean as chemical explosives. Of course, you need to figure out exactly what terms you’re defining cleanliness on - gamma rays count as radioactivity themselves, I believe, and most of the energy of an antimatter reaction would be released in the gamma range of the UV spectrum.
Most of those conclusions would seem to hold pretty well even if the ‘antimatter’ was a fairly mixed assortment of antiprotons, antineutrons, and antielectrons, forming stable atomic structures in reverse, instead of pure antiprotons.
A particle doesn’t have to have a charge to have an antiparticle. A neutron is made up of an up quark and two down quarks. An antineutron is made of an anti-up quark and two anti-down quarks.
Antimatter is about more than just charge. Everything (except mass) which can be reversed, is reversed. Of particular interest here is a quantity called baryon number, which is +1 for protons and neutrons, but -1 for antiprotons and antineutrons. Baryon number is (for all practical purposes) conserved in all physical processes. So, for instance, a neutron can decay into a proton, an electron, and an antineutrino, since both sides of the equation have baryon number +1 (electrons and (anti)neutrinos have a baryon number of 0, so they don’t count). But an antineutron can’t decay into a proton etc., since there you’d be going from a baryon number of -1 to +1 (but an antineutron can decay into an antiproton, a positron, and a neutrino).
I find it hard to believe that an antimatter bomb would be “clean”. As others have already stated, you generate lots of particles/antiparticles, and your explosion will put out lots of alpha and beta particles as well as gamma rays.
Ignore the alpha and beta – but those high-energy gamma rays are going to activate non-radioactive substances that are around. So unless you’re setting off your antimatter bomb in space, you’re going to have a fallout problem.
Ah, I should have known that someone would post before me about the quarks. That’s true, but I think it misses the meat of the issue. Neutrinos, for instance, are not made of quarks or any other charged particle, and appear to be truly fundamental (at least, until you get down to the string level), but there may (or may not: It’s a subject of some debate) still be a distinction between neutrinos and antineutrinos. In this case, the distinction would be something called lepton number, which is analogous to baryon number, but applies to electrons and neutrinos (and similar particles) rather than to protons and neutrons and the like. A neutrino has lepton number +1, while an antineutrino has lepton number -1.
