# Antimatter and matter

1. Jul 21, 2004

### garytse86

is there any particular reason that antimatter will annhilate matter?

This question has been bothering me for a while...

thanx

2. Jul 22, 2004

### vanesch

Staff Emeritus
In QFT, this is mathematically as evident as the answer to the question:
"is there any particular reason that the sum of a number and its negative give 0".
If you want a more intuitive answer, in QFT (which is a relativistic theory, so treats space and time in the same way ; just as you can go to the left or the right, you can go to the future or the past), antimatter going "forward" in time is the same as matter going "backwards" in time. You can hence view the matter-anti matter interaction as matter that came from the past into the future, and at a certain point, went back into the past again. You, as an observer, who travels forward in time you will see the two entities of the same matter particle in your slice of time, one going forward (the so-called particle) and another one (which is in fact the same one) going backward in time, but which you observe as an antiparticle going forward.
When you advance your timeslice, you'll come to the point where the particle "bounced back in time", which you, going forward, interpret as an annihilation.
In order to "bounce back", the particle has to interact with something, usually the electromagnetic field (otherwise it just goes on straight forward). This interaction causes the EM field to be excited, and so the net result you observe is a particle and an antiparticle meeting, disappearing and two photons to appear. The process is called an annihilation reaction.

cheers,
Patrick.

3. Jul 22, 2004

### garytse86

thanks a lot :) that was really helpful!

4. Jul 24, 2004

### VantagePoint72

Note that this explanation is from the point of view of a yet unproven theory...
From a superstring theory point of view, the cancellation is a result of two strings colliding, one oscillating in a way to be say an electron and the other oscillating in a way to be a positron. When they collide, they form one string. Just as two waves can be cancelled out if one's crests line up with the other's troughs, the opposite crests and troughs on the oscillating strings cancel out (even in the superstring realm, something can't vibrate in two directions at once). The resulting oscillation pattern of the new string is such that it has the properties of say, a photon, in which its vibrational energy that would correspond with its mass is used up entirely by quantum fluctuations. Therefore, its massless and due to it's specific vibration pattern has the properties of what we call a photon.

5. Jul 27, 2004

### Mk

Therefore if I am correct in saying that you just said when they collide it was as if they never existed, Only photons and phonons emerge, since one's going backwards in time and one is going forwards than all information would be destroyed, thus going against quantum theory

6. Jul 27, 2004

### Mk

That was a long sentance, if it was one...

7. Jul 27, 2004

### ZapperZ

Staff Emeritus
Photons and phonons emerge out of matter-antimatter anihilation? When did this happen?

Photon is its own antimatter. Phonon is quantized lattice vibration modes in materials. You have something weird mixing up in here that is causing a really bad diarrhea.

Zz.

8. Jul 27, 2004

### Mk

Phonon is kind of a particle of heat right? and Photon is a particle light kind of right? When mattaer-antimater collision accurs than the product is light and heat.

9. Jul 27, 2004

### ZapperZ

Staff Emeritus
Nope.

I have explained in my posting what a phonon is. You are confusing the IR part of the EM spectrum with lattice vibrations in a material. Phonons are a collective mode and can occur/exist only in a many-body interaction, NOT in a vacuum.

You should do background reading on what "phonons" are (a Solid State textbook would be a good start).

Zz.

10. Jul 31, 2004

### Mk

Well, the point was, heat and light emerge, and they don't exist after that? All information of the antimatter particle and the matter particle is lost?

11. Jul 31, 2004

### ZapperZ

Staff Emeritus
What heat?

Heat is defined either via statistical physics (which requires a medium that we don't have in vacuum), or IR spectrum. So where is this heat?

Where exactly did you get the idea that heat is a necessary component in a pair anhilation? We could have eliminated such long-winded discussion if you could have point out where you learned this.

Zz.

12. Jul 31, 2004

### Gokul43201

Staff Emeritus
No, information is not lost in a matter-antimatter annihilation. Energy and momentum are conserved, even in annihilations !