Question: What is antimatter?

Derek McKay-Bukowski answered on 10 Jun 2011:

Ah! This is a good challenging question, and very difficult to explain. There is actually a grand symmetry in nature. It seems that for almost all fundamental particles of a given mass and charge, there is a counterpart, which is the same mass, but opposite charge. Protons and electrons are NOT examples of this. They have opposite charges, but the mass is different. The opposite of the electron is the positron… it has the same mass as the electron, but a POSITIVE charge. Put a positron and an electron together and they annihilate each other… leaving no residual mass, only a couple of gamma rays. This is all hard-core particle physics (which is not my speciality), so I find this extremely difficult to understand too.

In fact, there is a whole copy of regular particles in the antiparticle world. You could have an anti-proton, a positron (anti-electron) and thus make an anti-hydrogen atom. (Just don’t let it near any regular matter, or it would find opposite particles to annihilate with!)

One of the great unsolved puzzles of cosmology is why the universe has so many particles. At this stage, no one has come up with a good explanation of why the universe formed with such an imbalance between the two (although it is just as well that it did!).

Finally… to finish with a joke.

Q: What are ants made of?
A: Antimatter.