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Thread: Matter and antimatter

  1. #1 Matter and antimatter 
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    Usually, in regular matter, electrons (Positrons) have a negative charge, and Protons have a positive charge. Antimatter, is composed of atoms which have the opposite charges of regular matter.

    Regular atom- Positron + Negative Proton
    Antimatter atom- Negative Electron + Positive Proton

    Matter and antimatter are asymmetric, the observable universe is composed almost entirely of matter. This means that during the formation of the known universe, there must have been a preference of matter over antimatter, but what was it? Besides the fact that interaction between matter and antimatter causes instability.

    Also, does any observable antimatter still exist in the universe, and can we observe it?


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  3. #2  
    Forum Radioactive Isotope MagiMaster's Avatar
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    You've got your atoms backwards. An atom of ordinary matter is composed of electrons, protons and neutrons. Anti-atoms would be composed of positrons (aka antielectrons), antiprotons and antineutrons.

    To answer your question though, yes, antimatter has been observed here on Earth. The various particle colliders produce small amounts of antimatter pretty regularly (although I don't know the details). Now, if you're asking has any large quantities of antimatter been observed in the universe, I don't think so, but I could be wrong.


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  4. #3  
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    Ahh, I see studying on my part is in order, thank you.
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  5. #4  
    Moderator Moderator Dishmaster's Avatar
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    There is a fundamental law of conservation of parity (even CP = charge + parity), that says that for every reaction of elementary particles, the net sum of particles and antiparticles stay constant. Example:



    A neutron (particle, neutral, baryon) decays into a proton (particle, positive charge, baryon) an electron (particle, negative charge, lepton) and an antineutrino (antiparticle, neutral, antilepton). In total, both the charges and particle numbers are the same on both sides. The same holds for baryon and lepton numbers, because antiparticles have a negative sign. Such conservation laws apply to all those reactions, although a violation of the CP symmetry shortly after the big bang is supected to be responsible for the overabundance of matter against antimatter in the universe.

    Another realm where matter and antimatter is present in the universe are the virtual particles. All the time, matter-antimatter pairs are created, even in a perfect vacuum. Normally, they annihilate immediately again, but in some cases - when they are separated quickly enough - they can become real. They are also thought to be responsible for the casimir effect in vacuum.
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