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## Matter and Energy

If matter is just a frozen form of energy and you can create energy by combining a particle and an antiparticle like an electron and a positron does that mean there is a way to form matter from energy theoretically? I am still in high school and dont think I understand how all this works and any answers would be appreciated.

2. Originally Posted by notayankeesfan
... I am still in high school and dont think I understand how all this works and any answers would be appreciated.
Welcome. The paths of energy converting to matter and vice-versa are fairly well documented ... in particle physics. Your question about it being a frozen form of energy is hard to answer definitively because it seems to about something at a finer level of detail than we have theory to support. If String Theory (or something like it) gets worked out we might have answers ... or not.

When two particles interact, there is a chance that they will change to lower mass particles and release energy in the form of photons (which maybe you'd consider to be particles also, but we rarely talk about photons as matter). Sometimes when two photons interact, if they have enough energy, they will give off a pair of particles, and the photons will have less energy of their own.

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There are certain things that must be conserved still, like momentum and charge. Quantum mechanics has its own quanties that must be conserved. That doesn't stop you from creating particles though.

If you can smash an electron fast enough with a positton, you can get heavier particles. You'll also get the corresponding anti particle. The energy it takes to do this comes from speed, or kinetic energy.

Unlike the universe which appears to be all matter, when you create your own you get half matter and half antimatter. Roughly speaking that is.

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What E=mc2 says is that matter can be considered as an equivalent amount of energy not that matter is "a frozen form of energy".
Pair production is a common way of creating matter from energy (a gamma ray produces an electron and positron).
High energy particle accelerators such as the LHC and the Relativistic Heavy Ion Collider create particles from the energy of the colliding particles.

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Thanks for the replies, does this mean that every piece of matter in the universe has a corresponding antiparticle somewhere?

6. Originally Posted by notayankeesfan
Thanks for the replies, does this mean that every piece of matter in the universe has a corresponding antiparticle somewhere?
No, that's possible, but there may be some good reasons that that isn't the case. So, we don't know that one either.

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It would appear that the universe cheated a bit by having antimatter not act exactly the same way as matter. It's part of something called CPT violation and that's a hairy topic to be studying.

Just be advised that we create pairs of particles, not just more matter. Check out "pair production" for more.

Not too long ago, a team at the LHC accelerator produced anti-hydrogen. That would be an anti-proton with a positron. That's right, the nucleus is negative and the orbiting particle is positive. Ain't that neat? Theoretically you can make anything out of antimatter, just keep it away from normal matter.

8. Originally Posted by notayankeesfan
Thanks for the replies, does this mean that every piece of matter in the universe has a corresponding antiparticle somewhere?
It's a good question. What's interesting is that though there are particle collisions that create both matter and antimatter, the universe around us is made up predominantly of matter, and nobody really knows why. There are scientists whose careers are based on trying to find out why. So it's not something you will get an easy answer to.

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Originally Posted by notayankeesfan
Thanks for the replies, does this mean that every piece of matter in the universe has a corresponding antiparticle somewhere?
Taking the basic rules from the Standard model then the answer to that would have had to have been "yes" - this was a problem for a long time because if there were bits of the universe that were dominated by antimatter you would expect to see some very characteristic photons coming from areas where the matter/antimatter zones were touching. There was no evidence of this.

Then something called CP-violation was discovered in the sixties. It did take nearly forty years to get a final definitive proof of this, so it was a fairly subtle effect. The upshot was that antimatter and matter did not always behave in the same way and in some classes of interaction you could actually end up with more matter than antimatter, despite starting with equal amounts. The mechanisms we understand that do this are not enough to account for the fact that matter dominates the universe but establish the principle that some particle interactions can produce more matter than antimatter - now the search is on for exactly how this happened in the very early universe. So now we can say that the answer to your question is "probably not".

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Does this mean to conform to the law of Conservation of Mass that antiparticles have negative mass

11. Originally Posted by notayankeesfan
Does this mean to conform to the law of Conservation of Mass that antiparticles have negative mass
If an anti-particle had negative mass, and it hit a particle, how much mass would be available to release as photons?

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I thought a photon had no mass and was just a package of energy

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What do you mean by "negative mass"? The inertial
masses of antiparticles are very well known to be the
same as those of their ordinary matter counterparts.
Gravitational mass of antimatter has not yet been
measured. It should be measured in another three
years or so.

-- Jeff, in Minneapolis

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I was wondering that if an antiparticle was a complete "opposite" of a normal one ie. opposite charge, opposite mass etc

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Originally Posted by notayankeesfan
Does this mean to conform to the law of Conservation of Mass that antiparticles have negative mass
Mass is not conserved - energy is (locally). You can make massive particles from photons and photons from massive particles. In conservation terms mass is just a form of energy.

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My recollection is that two photons are very unlikely to
interact unless another, massive particle is nearby. Two
gamma rays (high-energy photons) will interact near an
atomic nucleus to form particle-antiparticle pairs. Going
from massive particles to photons is simpler and much
more probable than the reverse, but the same amount
of energy is transformed either way.

-- Jeff, in Minneapolis

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My recollection is that two photons are very unlikely to
interact unless another, massive particle is nearby. Two
gamma rays (high-energy photons) will interact near an
atomic nucleus to form particle-antiparticle pairs.
Indeed, it is required to conserve momentum in pair production. Not sure if it is also required for the production of composite particles like protons - the interactions are far more complicated there.

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Originally Posted by notayankeesfan
I was wondering that if an antiparticle was a complete "opposite" of a normal one ie. opposite charge, opposite mass etc
All the quantum numbers are reversed, but mass is supposed to be the same. As Jeff mentioned, there is a team working on measuring mass of antimatter.

Negative mass is something that everyone asks about, but no one has ever seen. Kind of like a magnetic south pole without a north pole. There are no magnetic monopoles, and there are no negative mass particles. Any particle said to have negative mass is likely to be an accounting thing.

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