Antimatter is mysterious, dangerous, and rare. In fiction, it's at the core of Isaac Asimov's positronic brains, the engines on the Enterprise, and the bomb in Dan Brown's Angels and Demons. But in the real world, antimatter is fairly mundane stuff. If the entire universe turned into antimatter, we'd barely notice. Or would we?
Top image: NASA/Hubble.
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.