Matter and antimatter must interchangible

[houserichichi]

Chroot, thanks for the explanation. I had convinced myself muon-antimuon couldn't be produced but you've shed the light right on it for me! Thanks for the clarification folks!

 

[Invisible]

Does this sort of have something to do with a "Pair's Production"? I'm still in Physics 30, and we sort of learned something about this. I don't have my notes anywhere with me, but I'll explain what I remember by memory.

Annihilation: When matter and antimatter collide, matter is converted into energy. And then the next part, I seem to agree with Daniel about what he says that momentum is conserved.

Okay, say I have a high energy photon (ie. Gamma photon) and it strikes against a hard surface. Yes, both an electron and positron are created.

The Law Conservation of Charge in this case is that the existence of the negatively charged particle (an electron) from the collision of the gamma photon meant that there had to be another particle which was positively charged.

Law Conservation of Momentum (in this particle example):

- When matter and antimatter (electron and positron) collide, the total momentum before is zero.
- Yes, momentum has to be conserved, but in order for that to occur, two photons (agreeing with Daniel) must be produced which move in opposite directions, therefore, the total momentum of the photons is also zero!

Actually, I don't know if what I said has anything to do with it mainly because I'm still in high school... :-S

 

[houserichichi]

Sorry, this is back to something Chroot said:

If you smash a gamma ray into a piece of metal, you can create a wide variety of pairs (e+, e- or u+, u- or p+, p-, etc.). Each has its own statistical probability of being created, but all valid reactions are possible, given enough energy

So just to clarify, if we use a high enough energy in our experiment we could, in theory, create an e+/e- OR mu+/mu- OR tau+/tau- pair from two photons? If so could we ever be certain of the outcome or do we base our theory on the expected value of a probability, that is - we don't know for sure that an e+/e- pair will be created on each attempt if we so wish.

 

[shrumeo]

Howdy,

I'd like to know what happened at the beginning of the Universe then.
I'm under the impression that there was whole lots of matter and anti-matter at the time of the big bang, but there was a "slight" excess of what we call matter.

If there is such a thing as conservation of charge, then why was there an imbalance in the first place, and why can't we restore some of the imbalance?

 

[FZ+]

I'm under the impression that there was whole lots of matter and anti-matter at the time of the big bang, but there was a "slight" excess of what we call matter.

I don't think that is the general consensus. The general consensus - right now - is that there were equal amounts of antimatter and matter, but that symmetry is broken between the two - ie. antimatter is not exactly the same as matter, and for some reason, in our universe, decays a little more quickly. This is what leads to the imbalance. This, if I remember correctly, is borne out in a number of experiments which have illustrated broken symmetry, though results are not yet conclusive, since the effects observed do not fully account for the size of the imbalance.

Also, antimatter/matter imbalance is different from charge conservation. 1 proton + 1 antiproton -> 1 proton + 1 electron conserves charge, but still breaks the standard model.

 

[shrumeo]

I don't think that is the general consensus. The general consensus - right now - is that there were equal amounts of antimatter and matter, but that symmetry is broken between the two - ie. antimatter is not exactly the same as matter, and for some reason, in our universe, decays a little more quickly. This is what leads to the imbalance. This, if I remember correctly, is borne out in a number of experiments which have illustrated broken symmetry, though results are not yet conclusive, since the effects observed do not fully account for the size of the imbalance.

Also, antimatter/matter imbalance is different from charge conservation. 1 proton + 1 antiproton -> 1 proton + 1 electron conserves charge, but still breaks the standard model.

I see. Thanks for clearing that up. :shy:
It's not that there was more antimatter, it just decays (into?) quicker.
And there might have been simply a symmetry imbalance, not a charge imbalance.

 

[scarecrow]

I don't know enough about astro-physics, but after reading some stuff on this subject of anti-matter, it just came to me that if assuming Einstein's theory of space-time and his analogy of gravity to a trampoline (I would say blanket) and curved space...can't the universe be sitting on anti-matter and that is exactly what we feel as gravity.

Someone please set me straight. Thanks.