Question: what exactley is antimatter?

Dean Whittaker answered on 16 Jun 2010:

Antimatter is.. well… the opposite of matter. Basically the standard model says that for every particle that exists, there exists an exact opposite particle with the same mass. If they come into contact then they turn into energy. However, if you take energy, you can create a matter – antimatter particle pair.

We create (and use!) antimatter all the time. Positrons are very useful for probing into materials. Our university does it. A positron is an antielectron. That means it has positive charge instead of negative charge and some other things are different in the details.

Nobody really knows why the universe is full of matter and not antimatter. There’s plenty of theories though. We can’t have antimatter naturally because it’d meet matter at some point and dissapear. But why did matter win during the big bang?