Question: Where is antimatter found most commonly?

Evan Keane answered on 21 Jun 2011:

First of all we should clarify what anti-particles are. If we have a particle, for instance a proton, it has an anti-particle which is identical except for one thing – it has the opposite electric charge. We call this an anti-proton, and there are anti-electrons too (commonly called “positrons”) and neutrons are there own anti-particles. Ok?

That’s anti-paricles – but what is anti-matter? Well that is atoms made of these anti-particles. Lets think of the one which is the easiest to make. The simplest matter atom is hydrogen. It has one proton and one electron. So to make anti-hydrogen you need an anti-proton and an anti-electron (a positron). Oh ya … I forgot to mention the complication … when particles and anti-particles meet they ANNIHILATE each other! So you can see it is tough to make anti-matter as you cannot touch it against anything (even the air!) which has matter in it or it will annihilate!

Imagine how hard it is to make anti-hydrogen! Where do you keep it? In a jar? … oh but the jar is made of matter and so it can’t touch the anti-matter! Physicists have to come up with all types of tricks to keep the anti-hydrogen from annihilating and the record for keeping it stable is 15 minutes.

So we get to the answer – anti-matter does not really occur commonly anywhere. Anti-particles occur very often (usually positrons), especially we see them a lot in astronomy, but they quickly annihilate when they meet regular particles and certainly well before they can form an anti-matter atoms. The reason why there is more matter than anti-matter in the Universe is a something we don’t know. There is no explanation yet in physics as to why this is the case. Maybe you can figure it out if you are a physicist! You would probably get a Nobel Prize if you did! 😀