# Anti matter ?

1. Dec 2, 2009

### Neopet

On the Earth, it is produced in tiny quantities in particle accelerators, but it's also produced say, in outer space as well ? is this true?
Are human being made of anti matter, or does it have to be produced purposely, and it exists naturally in outer space ?

2. Dec 2, 2009

### fatra2

Hi there,

You are asking too many questions at once. So I'll try to give an explanation that should answer most of the questions you asked.

Anti-matter is formed, just like matter, out of thin air, not really but very close to it. To be perfectly clear, photons carry energy. This energy can be transformed to create matter, following Einstein $$E = mc^2$$ where m stand for matter. But in the process of creating matter, anti-matter is also created, following many conservation principles related to quantum mechanics. OK anti-matter is produced at the same time as matter.

So as you said, matter and anti-matter is produced in accelarators, in outer space, but also inside your body and mine. That's right, when a photon (it has to have more than 1022keV) interacts with the matter in your body, pair-production (the term for creation of electron and positron) can happen. Therefore, anti-matter is continously created on Earth, and not just in special labs.

Now to make the little story complete, once anti-matter is created inside your body, it will very quickly interact with the matter around it, anhilating back into energy.

Hope this helps you a bit. Cheers

3. Dec 2, 2009

### QuantumPion

Some radioactive isotopes decay by positive beta decay. This is where a proton in the nucleus of an unstable isotope turns into a neutron, and emits a positron (anti-matter electron).

This is used for a special type of medical imaging called Positron Emission Tomography. A radionuclide which decays by positive beta decay is injected into the body. When a decay occurs, the positron that is emitted quickly runs into and annihilates an electron in the body. This creates a pair of gamma rays which pass through you and are detected by the machine. Because two gamma rays going in opposite directions are created when the positron annihilates, you can make a 3-d image of the inside of the body by carefully timing when the two gamma rays arrive at the detector.

4. Dec 2, 2009

### Neopet

AWESOME, just wondering if my line of reasoning was in the right direction , yeah thanks

5. Dec 2, 2009

### Bob S

Scientists at Fermilab ususlly have ~1 or 2 x 1012 anti-protons circulating in the Tevatron at 980 GeV, and up to 50 milliamps (circulating current) of anti-protons in the "stack" at 8 GeV. Check status at
http://www-bd.fnal.gov/notifyservlet/www?project=outside
CERN has produced anti-hydrogen (anti-proton plus positron) in very small quantities.
Bob S