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Properties of anti-matter

  1. Aug 24, 2012 #1
    As the positron has a positive charge and is the mirror of the electron and the antiproton is negative and a mirror of the proton, will then anti-matter produce anti-gravity. If not then why not? Is this linked to the photon pairing of electron and positron?
     
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  3. Aug 24, 2012 #2

    mathman

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    I'll turn the question around. Why should it produce antigravity? Gravity depends on mass and energy - whether the stuff is matter or antimatter doesn't matter.
     
  4. Aug 24, 2012 #3
    I am assuming that you mean because the charges balance out there will be the same net effect? if so have anti-matter molecules been created yet?
     
  5. Aug 24, 2012 #4

    Bill_K

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    :confused: No balancing is involved. The mass of an antiparticle is positive. The energy of an antiparticle is positive. The effect of gravity on an antiparticle is in the same sense (attractive) as the corresponding particle. Particles attract particles. Particles attract antiparticles. Antiparticles attract antiparticles.
     
  6. Aug 24, 2012 #5
    I notice that anti-helium-4 nuclei have been produced now.
     
  7. Aug 25, 2012 #6

    BruceW

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    in response to the original question, anti-particles have opposite 'charge' of the normal particles. There are several different kinds of 'charge', including electrical charge and lepton number, etc. But mass is not one of these types of 'charge'. So the mass of anti-particles is the same as mass of normal particles.
     
  8. Aug 25, 2012 #7
    Thanks. I believe some of the proposals at CERN are to detect if there is even a negligibly small repulsive force. They don't seem to favour this though. I wonder what they will find to explain the discrepancy between the amounts of matter and antimatter in the universe.
     
  9. Aug 25, 2012 #8

    Bill_K

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    The CERN experiment is called AEgIS. See here and here. They will use a beam of antihydrogen atoms.
     
  10. Aug 28, 2012 #9
    Would someone please explain? Based on BruceW, Bill_K comments... it appears our universe does not have "conservation of mass" as a basic law of particle interaction - two particles can anihilate with mass disappearing. Since mass is in many ways equivalent to energy, is there a discrepancy here and how is this normally explained (or is it an unsolved problem)? Thanks
     
  11. Aug 29, 2012 #10

    BruceW

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    When two particles annihilate, some other form of energy must be given off. For example, photons, which carry the energy away.
     
  12. Sep 2, 2012 #11
    What I am trying to grasp is the electron/positron pairing in photons when matter and anti matter annihilate. When photons are released from matter only what are they then composed of? Electrons only?
     
  13. Sep 3, 2012 #12

    BruceW

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    eh?! Let's say that an electron and positron collide and annihilate. This means that the electron and positron disappear. But then two photons will appear instead. (And in higher-energy collisions, other massive particles can be created).

    So in the simple case, we start off with an electron and a positron, and we end up with two photons. These photons are not composed of anything.
     
  14. Sep 3, 2012 #13
  15. Sep 3, 2012 #14

    Drakkith

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  16. Sep 3, 2012 #15
    Well high energy photons can produce an electron and a positron pair. From where?
     
  17. Sep 3, 2012 #16

    Drakkith

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    From the energy they possess. That's all I know. Particle creation can happen according to some very complex rules, but it all comes down to having enough energy/mass to create the new particles.
     
  18. Sep 3, 2012 #17
    Sorry I should have said earlier composed from electron energy only.
     
  19. Sep 3, 2012 #18
    Generating a positron from a collision with matter seems only feasible if matter and antimatter have a connection beyond simple annihilation. Do quarks and anti quarks co-exist in some sense?
     
  20. Sep 3, 2012 #19

    Drakkith

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    I'm unsure as to what you are asking. I know of no "connection" between matter and antimatter other than what the standard model of particle physics tells me.
     
  21. Sep 3, 2012 #20
    Well if you think about it a high energy photon hitting matter should produce two electrons as it has not hit anti matter. It makes sense that a photon hitting anti matter would generate the electron's anti particle, the positron. Yet here we have a positron being produced by a photon hitting matter. If an electron will annihilate a positron how can they both be produced without an immediate annihilation taking place? They are after all produced by the same photon. This can be explained I suppose by them leaving in opposite directions. However, we now are in the position where this positron will quickly annihilate with another electron. This will produce two photons, not one, so how did one photon gain the ability to produce the electron and positron if annihilation does not produce a single photon?
     
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