Antimatter creation/annhilation efficiency

OK, according to conservation of energy, it’s impossible to get more energy out of a system than you put into it. Presumably, this would apply to the annhilation of artificial antimatter with natural matter: the energy equivalency of the antimatter annhilated would be less than the energy expended in the charge reversal process. HOWEVER, what if you include the energy equivalency of the pre-existing matter? No need to expend any energy on it before you annhilate with the antiparticle.


A) Does this defy conservation of energy in any way?

B) Is it possible to get the efficiency of a matter/antimatter conversion process to take less than twice the equivalent energy of the mass being converted?

Energy is mass, and mass is energy. It’s always conserved without exception, as far as we know. To create one gram of antimatter takes one gram’s worth of energy (1g * c^2 = 10^17 Joules). It takes the same amount of energy to create a gram of normal matter. Mix them together to annihilate, and you get two grams worth of energy back.

The problem is that you can’t just make antimatter. You have to make matter and antimatter in equal amounts, thus you don’t get to save half the energy by making just the antimatter and then destroying it with some spare matter you have lying around.

So, you are already just breaking even. Throw in some inefficiency in collecting the gamma rays from the annhilation process and you’re well on your way to obeying the laws of physics.

To answer your questions, then:
a) If you could do what you suggest, yes it would violate conservation of energy. It would also violate conservation of “particleness” or what is called Charge Conjugation. You can’t change matter into antimatter or antimatter into matter, and if you create or destroy stuff it has to be equal parts of each.[sup]*[/sup]

b) No.

[sup]*[/sup]So, how did we end up with so gosh darn much matter and no antimatter? This law (CP invariance) is broken in some very minor ways in certain esoteric particle reactions such as neutral kaon decay. Enough to result in a preponderance of matter in the universe, but I doubt you could take advantage of it for your purposes. First, the bias is very small. Second, you want antimatter and the bias is towards matter. Finally, particle physics is never able to create just certain particles - if you find a particle that decays into antimatter more often than it does matter, you’ll end up spending many many times more energy generating other particles and just plain heat and radioactive concrete trying to get them. So, you still are out of luck.

Absolutly! It also violates the conservation of mass principle. Two conservations laws (conservation of energy and conservation of mass) are approximations of a more fundamental law – the conservation of mass-energy. The whole point of E = m c[sup]2[/sup] is that mass and energy are equivalent. The amount of energy you create is equal to the amount of mass you lose divided by c[sup]2[/sup]. Matter/anti-matter annilation is an example of a process that violates both conservation of mass and conservation of energy, but not of conservation of mass-energy.

No. You cannot just convert matter to anti-matter. That would violate the first law of thermodynamics.[list=1]Thermodynamics[]You can’t win.[]You can’t break even[/list=1]

This is correct. But just to be perfectly clear, you must note that you are not permitted to create just antimatter, you have to create one gram of antimatter and one gram of matter at the same time. You can’t save half the energy cost by using leftover matter you have in your basement.

Has this been proven beyond doubt? It sure looks like our universe has more matter than antimatter. If so it should be possible to make one without the other. But of course, you’re right for the reactions we know about.

Dude, read my first post in this thread, especially the last part of it. In short, there are some known reactions with a bias towards matter, but it’s not enough to allow you to violate conservation of energy.

Although, if you could create plain antimatter, I guess you’d just be borrowing the exising matter from the big bang and you’re still not violating conservation of energy. However, you are still out of luck because of how weakly CP invariance is violated.

Yeah, I don’t see any reason that the creation of antimatter alone would be any reflection on conservation of energy. You have energy before and energy after-- same amounts. It doesn’t matter if the energy is in a mass form or a non-mass form.

The trouble with creating antimatter without matter comes from the need to conserve quantum states.

"Two conservations laws (conservation of energy and conservation of mass) are approximations of a more fundamental law – the conservation of mass-energy. " – DrMatrix

I think it is more accurate to say that the conservation of energy law absorbed the conservation of mass law when relativity hit the scene. So it is really one law-- conservation of energy.

“Energy is mass, and mass is energy.” – scr4
I don’t think that is totally true, except when you regard the universe as a whole.

I think it makes a lot more sense to regard mass as a property of energy that can be observed when it is possbile for an aggregate collection of energy to be observed as stationary. Energy forms like heat, nuclear force potentials and such can have mass ascribed to them. Free EM (photon) energy and kinetic energy cannot have mass ascribed to them, unless you are viewing the whole universe as a single “thing”.

I’m trying, but I just can’t see how converting matter to antimatter would violate the first law of thermodynamics.

The bolded part is, I think, the key here. Exactly what charge reversal process are you referring to? If God gave you a “charge reversal machine” that changed matter to antimatter, that wouldn’t violate the conservation of energy; an antimatter rock has as much energy as a normal matter rock of the same size. If you put them together, you get a huge explosion, but the energy for it is just the energy contained in the rocks’ rest mass.

So the answer to A) is “no”, and the answer to B) is, well, what “matter/antimatter conversion process”?

It seemed to make sense at the time. But you’re right. I don’t know what I was thinking.

Could Hawking radiation be used to convert matter to anti-matter? Create a small black hole using matter. The Hawking radiation should be equal parts matter and anti-matter. You’ve converted matter to matter and anti-matter. Of course, you have the problem of how to create a small black hole, how to contain it, etc.

What matters as far as creating anitmatter is that all of the elements involved at the beginning and the end need to end with the same net totals for quantum values (charge, spins, etc). I don’t see any other restriction.

Hey, don’t some stellar fusion reactions create a positron without creating an electron? I think that is a perfect example of the creation of antimatter without creating matter, and I am pretty sure it is real and common. :slight_smile:

Not exactly. The charge is conserved by the conversion of a proton to a neutron whenever the positrons are created, and the other quantum properties such as spin, lepton number, etc. are conserved by the creation of a neutrino (or would that be an anti-neutrino?)

HOWEVER: I thought it was theorized that quarks can be converted into leptons, and vice-versa; the mechanism leading to the speculative proton decay. I’ve also read that magnetic monopoles, if they exist, could catalyze such decay. In theory then, you could break protons down into positrons (or build anti-protons out of electrons) with only the need to generate counterbalancing neutrinos, which would not use much of the total energy involved.

Matter and energy are not things they’re properties of a system. If you define your system to include all the products of the interacting particles then the mass and energy remain the same.

Probably just a misunderstanding there, Lumpy, all I was saying was that those quantum values needed to be conserved through the process. I didn’t mean to suggest any further restrictions.

And Ring, while the energy will remain the same, the mass might not remain the same. Also, be careful not to synonymize “matter” and “mass”. :slight_smile:

No, that’s not quite true. If you are consistent in defining your system the mass must remain the same. I certainly did not synomize(sic) matter and mass. In fact no one has ever managed to define just what matter is, whereas mass (in SR) is precisely defined as the magnitude of energy momentum four vector.

Okay Ring, then when you have a system that is producing gamma radiation thru nuclear decay, you don’t see that as a decrease in mass? If not, please explain.

This is also not exactly correct. Again, if you consistently define your system both properties of the system remain the same, and are not interchangeable.

Take two photons with parallel velocities – the system has energy but no mass. Now take two photons with antiparallel velocities – the system now has both mass and energy.

The local mass defect is a result of the energy loss – not the cause (the binding energy increases and the potential energy energy decreases), however the system mass and energy remain the same. There is no conversion of mass to energy.