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Asked by wizzyg12 to Sam on 28 Jun 2013.
Question: What is antimatter?
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Sam Geen answered on 28 Jun 2013:
So Claire would have been ideal to answer this question as the place she works makes it!
Antimatter is like normal matter but with an opposite charge. When it contacts normal matter it annihilates both and emits energy according to E=mc^2. It was predicted by Paul Dirac, who was from Bristol, when he realised that the quantum physics equations could also have antielectrons as well as electrons. It can be made when two particles collide at high speed. No one knows why the universe is made of matter and why there was more matter than antimatter.
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Claire commented on :
Jumping in here just cause 🙂
Every particle has an antiparticle – an electron has an antiparticle called a positron. A proton has an antiparticle called an antiproton. You can even make anti-atoms by combining antiprotons and antielectrons together, the difference is that the nucleus would negatively charged instead of positive.
We get a lot of antimatter produced in our collisions along with matter – it comes from conservation of charge. If the collison had zero overall charge to begin with, you can create electrons but then you have to create positrons too in an equal amount so that the overall charge is still zero.
These antiparticles just end up in our detector with the normal stuff. In fact, it’s pretty difficult to collect antimatter because it can’t touch anything made with normal matter – it annihilates (explodes) in a flash of energy.
And this is where the problem with the universe comes in. When the universe was created, matter and antimatter would have been created in equal amounts, and so it should all have annihilated and left a universe of just plain energy. But somehow we got some matter left over (only 1 in a billion particles, but still an excess)… so what happened to the antimatter?
We don’t know yet, but one of the LHC experiments (LHCb) is trying to find this out!