Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: kenhikage on 05/10/2010 06:21:57
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I have two questions about anti-matter:
1) When matter (or particles) comes into contact with antimatter (or antiparticles), both are destroyed. Where does that energy go?
2) Why isn't it accepted that antimatter produces anti-gravity?
I came across these questions when pondering dark energy and the (apparent) matter-antimatter disparity. I think you can follow my reasoning.
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Energy is transferred in the creation of photons and neutrinos.
Antimatter may possess an antigravitional field but most physicists agree that the probability for such thing is very low. There is no absolute proof yet...
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Antimatter exhibits the same attractive gravitational field as matter and there is no reason to expect that it would do otherwise the symmetries are not in that direction.
When similar matter and antimatter particles annihilate they turn into energy in the form of photons if the interaction is at low energy but at very high energies a whole range of lighter particles may be created essentially out of the quantum mechanical vacuum.
The fact that such matter antimatter collisions can produce a wide range of particles is a clear indication that everything is essentially made of the same stuff.
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It is comforting that matter and antimatter are made of the same, albeit differently flavored, quarks.
So, given that both types of matter are mutually destructive, do they "try" to "stay away" from each other as like poles of a magnet do? To spell out my idea, could dark energy be that missing disparity of anti-particles in the form of antimatter?
I suppose I'm assuming that light doesn't interact with antimatter, which may be baseless.
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Antimatter has precisely the same physics and chemistry as matter so the interactions with light are just the same. A photon from a piece of matter can interact normally with a piece of antimatter. The reason for this is a photon is its own antiparticle. One photon can cancel out another completely for an instant (inside the energy uncertainty time) but the result is almost always two exactly similar photons travelling in the same directions that they were before. The exception is for very high energy photons that are disturbed by the presence of other matter which can generate other particles.
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As far as the Sydney lecture is concerned. The description seems to have been a bit hyped up. My understanding of what they are talking about is detecting gamma rays with the frequency (energy) associated with electron positron annihilation. this is a clearly observable spectrum line and shows very high energy material is involved. this is what one might expect with material orbiting and colliding very close to the event horizon of a black hole. The antimatter is produced by the process of pair production where high energy gamma rays and particles interact with each other to produce electron - positron pairs the positrons are antimatter and will interact with the next electron they meet to create the spectrum line. this may be a very useful tool for exploring high energy events throughout the universe.
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The mass of an antiparticle is the same as, not the opposite of, the mass of the particle. Therefore, because gravity depends on mass, its gravity should also be the same.
Paricles and antiparticles do not generally repel; indeed, they tend to attract because if charged they will have opposite charge.
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I see, so their mass is the same, but their charge is opposite. How about their spin?
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The spin is the same but the main properties of spin are associated with the orientation of the particle not its existence
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For antimatter to produce antigravity it would have to generate a negative pressure. This would be indistinguishable from a description of dark energy. If this were true then annihilation of matter with antimatter would not be possible since antimatter would repel its matter counterpart. Since annihilations have been observed then it appears that no such antigravity mechanism exists.
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We now have research into neutron-antineutron oscillations. This could lead to new physics and modifications of the standard model.
https://arxiv.org/abs/0902.0834
http://www.phys.utk.edu/neutron-summer-school/lectures/snow.pdf
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The Alpha experiment at CERN is measuring the gravitational acceleration of hydrogen and anti-hydrogen.
In their 2013 paper, the experimental errors were larger than the 9.8m/s2 they were trying to measure.
Antihydrogen is very hard to handle - it is uncharged, so you can't easily hold it in a magnetic bottle, and it annihilates on contact with normal matter.
But their experiments are continuing with larger samples and refined techniques.
https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter#Cold_neutral_antihydrogen_experiments
http://alpha.web.cern.ch/node/248
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If antimatter had anti-gravity, it would lead to violations of energy conservation as a positronium atom could then be moved to any height in a gravitational field without any net input energy (despite the fact that the photons emitted by the decay of positronium would have their energy affected by the gravitational potential).