How Much Does Antimatter Weigh?


Dr. Dave Goldberg in io9:

Our own Charlie Jane Anders wanted to know:

Last week, researchers announced they had found a method of measuring the gravitational mass of antihydrogen. Does this mean we can WEIGH ANTIMATTER? Or, if not, what does it actually mean?

Before getting into the nitty-gritty, let me assuage your curiosity with a) Yes, but at the moment we can only guess its weight with the accuracy of the world's worst carnival barker, and b) If it turns out that antimatter weighs more or less (or god forbid, the negative) of ordinary matter, it means that we've got to seriously rethink what we know about gravity.

But before getting into any of that, let me say a word or two about what antimatter actually is.

A quick antimatter primer

Every type of particle in the universe has an antiparticle – a sort of evil twin version of itself, with the opposite electrical and nuclear charges. An electron, for instance, has its counterpart, the positron, which has a positive electric charge, rather than a negative one. A proton has the boringly named “antiproton” with a negative charge. In fact, antimatter is so similar to ordinary matter that a few particles, notably the photon and the Higgs Boson, seem to be their own antiparticles.