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Does Antimatter exist in the universe anymore?

  1. Oct 21, 2014 #1
    If Antimatter was completely annihilated after the Big Bang, how is it that we have studied it. As well as artificially created it? If we cant create normal matter, why would we be able to create antimatter? And since we can, why doesn't it immediately get annihilated from the contact of the matter?
     
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  3. Oct 21, 2014 #2

    mathman

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    Positrons are antimatter (widely used in medical devices). Antimatter has been created in laboratories.
     
  4. Oct 21, 2014 #3

    SteamKing

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    It depends on what you mean by 'create' matter. We can certainly transmute elements by using atom smashers, and there are nuclear reactions in which antimatter can be created momentarily before it annihilates with regular matter. What is difficult to do is to contain and accumulate significant quantities of antimatter with current technology.
     
  5. Oct 21, 2014 #4
    Hi Nova! There is an ongoing collaboration called ALPHA which studies antimatter;
    Home page: http://alpha.web.cern.ch/
    How Alpha works: http://alpha.web.cern.ch/howalphaworks
    And a clip from that page, showing some of the equipment:


    EDIT:
    This clip was better (description of equipment and techniques):
     
    Last edited: Oct 21, 2014
  6. Oct 21, 2014 #5

    Drakkith

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    The simple fact is that we can create both matter and antimatter. We do this all the time in particle colliders.

    If we say "shortly" instead of "immediately", then it usually does. The exceptions are when we store antimatter in order to study it.
     
  7. Oct 21, 2014 #6

    e.bar.goum

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    Not only do we routinely create matter and antimatter in particle accelerators, and store it in traps or rings, it's important to note that antimatter is created by nature all the time. Nuclei that are proton rich compared to stable nuclei decay via positron - anti-electron - emission!

    Linked is a chart of all known nuclei, the number of protons are on the y axis, the number of neutrons on the x axis. The black squares are the stable isotopes, and everything that is coloured pink is a nucleus that decays via positron (β+) emission. http://upload.wikimedia.org/wikipedia/commons/7/79/NuclideMap_stitched_small_preview.png
     
  8. Oct 22, 2014 #7

    Orodruin

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    In addition to what has already been said, we are also constantly bombarded with anti-matter in cosmic rays. For example, the AMS-02 experiment has measured the positron fraction in the electron and positron cosmic ray flux (see, e.g., http://www.ams02.org/wp-content/uploads/2013/03/Press_2.jpg). Between 5 and 15 percent of the total flux is positrons, depending on the energy you are looking at.
     
  9. Oct 22, 2014 #8

    e.bar.goum

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    Also, there is the suggestion that to solve the baryon asymmetry problem, you can have large portions of the universe composed of antimatter, as opposed to matter. It's not a terribly popular view, and it's not supported by some observational evidence, but it's not completely laughable either.
     
  10. Oct 22, 2014 #9

    Chronos

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    The original photon-baryon ratio of the early universe is totally dependent on matter - antimatter annihilations.
     
  11. Oct 22, 2014 #10
    wouldn't helium be a better option than hydrogen? you get to study even anti neutrons..
     
  12. Oct 22, 2014 #11

    phinds

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    Who are you quoting? That is, who SAID it is hydrogen? I'm not finding that in the thread. Please use the quote button. Thanks.
     
  13. Oct 23, 2014 #12

    Chronos

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    Anti matter is created continuously in the universe, just not in large quantities and it tends not to escape annihilation for very long. In the very early universe it is believed to have been almost as abundant as regular matter. There was, however, an imbalance that permitted a relatively miniscule amount of regular matter to survive annihilation. The reason for this is a mystery. All we know is it occurred before atoms had a chance to form.
     
  14. Oct 23, 2014 #13
    But antimatter and matter share the same properties right? So wouldn't it not make sense due to law of conservation?
     
  15. Oct 23, 2014 #14

    Orodruin

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    Generally, antiparticles have the same mass as their corresponding particles, but carry opposite quantum numbers (such as electric charge). Assuming that you have enough available energy and momentum to create the particle-antiparticle pair, no conservation laws are being violated.
     
  16. Oct 24, 2014 #15

    vela

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    What would make sense? Conservation of what?
     
  17. Oct 25, 2014 #16
    I keep seeing the word "create" over and over again. It is counter-intuitive. We should not be able to create matter, it exists and we are allowed to shape it, transform it, but not create it.
     
  18. Oct 25, 2014 #17

    Drakkith

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    That is simply not correct. Matter can be created and destroyed and it happens all the time. There's nothing counter-intuitive about it.
     
  19. Oct 25, 2014 #18
    But matter is destroyed, its converted into energy via E=mc2 right?


    Just like what others said, it depends on the law of conservation of what. The law of conservation of charge holds because the particle-antiparticle pair have the same charge magnitudes but with opposite polarity (eg +e for a positron and -e for an electron). An annihilation of a particle-antiparticle pair does maintain conservation of energy and linear momentum, but the opposite phenomenon, called pair production (where a photon materializes into a particle-antiparticle pair), there must be a nearby massive object (eg. a nucleus) to maintain the law of momentum and energy conservation. The nucleus must be involved to carry away part of the initial photon momentum.
     
  20. Oct 25, 2014 #19

    Nugatory

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    Google for "pair production" - this is the process by which energy on the form of photons turns into an electron and an anti-electron.
     
  21. Oct 25, 2014 #20

    phinds

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    Wrong. That is the theoretical maximum energy that can be extracted if you could create a 100% efficient process. Atom bombs, for example, as WAY far from 100% When matter is forced to change states, it is converted into many things, energy just being one of the possible ones, and it is usually as light and heat and other forms of matter. The heat is, I think, the main energy that one thinks of in atom bombs although there's a lot of light as well. I'm not sure what kind of particles are left over from the blast.
     
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