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Questions about anti-matter

  1. Oct 12, 2006 #1
    Hello all, I'm new here, and I don't know where to post this. So please move if in the wrong section.

    I'm a 15 year old and I know nothing of this, I've read some articles but it still confuses the hell out of me.

    I'm wondering what it's all about, how it's formed and what happens to matter inside it and around it.
     
  2. jcsd
  3. Oct 12, 2006 #2

    Astronuc

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    Anti-matter has much the same properties as matter, the differences being in the polarity, e.g. spin. When an anti-particle meets a particle of the same type, e.g. electron meets positron or anti-proton meets proton, the particle pair annihilates. The electron and positron annihilate producing two gamma rays of equal energy. The proton and antiproton annihilate into a meson shower.

    Antimatter can be produced on earth by high energy collisions in the laboratory or in the upper atmosphere where high energy protons collide with protons (hydrogen) or perhaps atomic nuclei in the air. The collision transforms the kinetic energy of the high energy particle into a particle-antiparticle pair. As far as we know, anti-particles are created in pair with particles. Ostensibly, similar processes occur in some natural cosmological phenomena.

    In nature, there is very little anti-matter in our part of the universe, as far as we can tell.

    One big question still unresolved asks whether or not equal amounts of matter and anti-matter were created in the beginning of the universe, and if so, where did the anti-matter go.

    http://hyperphysics.phy-astr.gsu.edu/Hbase/particles/antimatter.html
     
    Last edited: Oct 12, 2006
  4. Oct 12, 2006 #3
    Isn't a positron also briefly formed in some MR applications?
     
  5. Oct 12, 2006 #4

    Danger

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    I'm not sure about in MR, but a PET scanner is based upon Positron Emission Tomography. Unfortunately, I don't know at this point how it works. I'll have to look into that.
     
  6. Oct 12, 2006 #5
    So, with the spin, does that mean that if matter electrons spin clockwise, then anti-matter electrons spin anti-clockwise?
     
  7. Oct 13, 2006 #6

    Danger

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    Not just electrons/positrons. The anti-particles of neutral particles have an inverted I^3 (vertical component of isotopic spin). Best leave the explanation of that to someone more qualified.
     
  8. Oct 13, 2006 #7
    Has anyone ever discovered this anti-matter as if in obtained it!??
     
  9. Oct 13, 2006 #8

    LURCH

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    Yes, antimatter has been produced in colliders.
     
  10. Oct 14, 2006 #9
    have anybody read the dan brown book "angles and demons" ?


    i was wondering whether like in that novel ---is it true that anti matter is highly unstable and very destructive etc., etc.!??


    to tell you the truth, this book is the thing that inspired me to make physics part of my future career.
     
  11. Oct 14, 2006 #10
    Antimatter, as has been explained, annihilates the first 'real' matter counterpart it touches. It's very difficult to contain any realistic quantity of antimatter, and the quantities we're talking about are tiny, tiny fractions of micrograms produced in the entire history of man-made particle physics experiments.

    If you could - hypothetically - generate on the order of kilograms of antimatter and store it in a 'bomb' - it would be immensely destructive. A few dozen kilograms of antimatter would probably excavate an area the size of a small country down to the bedrock and wipe out everything in line of sight with a burst of extreme-hard gamma rays. As I recall, the mass-energy conversion of a modern nuclear warhead is either 0.3 or 0.03% of the fusionable matter inside. An antimatter bomb would have a conversion rate of 200% on its payload - every particle contained within it, and a partner for each of those particles in whatever it hits.

    That technology, thankfully, is way, way beyond us. You'd need to be doing something funky with a neutron star or running dozens of supercolliders continually for thousands of years to generate that much antimatter.
     
  12. Oct 14, 2006 #11
    wow....so we shall wait for another millenium!?

    hahax

    anyways, is this under quantum physics!?(which branch of physics is this!?)

    particle physics then!?---they have always facinated me!
     
  13. Oct 14, 2006 #12

    ZapperZ

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    Please note that "antimatter" is well-known and have been produced under many circumstances. It is not always under the highly exotic situation of particle accelerators. We use positrons in nuclear medicine, especially when you have PET Scans.

    So we know so much about it than we can USE it. That is always a good sign that the idea is well-matured and well-verified.

    Zz.
     
  14. Oct 14, 2006 #13

    Astronuc

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    Fortunately, mankind only produces fractions of picograms of antimatter over long periods of time. KG of antimatter would be extraordinarily destructive anywhere on earth. Not only gamma-rays, but showers of mesons in the intermediate period.

    As Danger and Zapper mentioned Positron Emission Tomography (PET or PET scan) is an important diagnostic technique in which a positron-emitting isotope is placed in a patient. The annhilation gamma-rays are then detected where the PE isotope accumulates.

    http://en.wikipedia.org/wiki/Positron_emission_tomography
    http://www.radiologyinfo.org/en/info.cfm?pg=PET&bhcp=1
    http://www.triumf.ca/welcome/petscan.html
    http://neurosurgery.mgh.harvard.edu/pet-hp.htm
    http://www.nuc.ucla.edu/pet/
    http://www.bnl.gov/CTN/PET.asp

    Nuclear magnetic resonance uses the fact that proton spins can be flipped in a magetic field and the resonance depends on the compound in which the proton (nucleus of hydrogen atom) is situated.

    http://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
    http://www.cis.rit.edu/htbooks/nmr/contents.htm
    http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/nmr1.htm
    http://www.cns.uni.edu/~macmilla/mcmurry/mcmurry_chapter_13/index.htm

    With regard to the electron spin, I beleive electrons are considered right-handed, which means they would have spin clockwise if one observes in the direction of travel, or counter-clockwise if observed in direction opposite direction of travel. See discussion on spin here - http://hyperphysics.phy-astr.gsu.edu/Hbase/particles/neutrino3.html

    See this comment - "The term "electron spin" is not to be taken literally in the classical sense as a description of the origin of the magnetic moment described above. To be sure, a spinning sphere of charge can produce a magnetic moment, but the magnitude of the magnetic moment obtained above cannot be reasonably modeled by considering the electron as a spinning sphere. " in http://hyperphysics.phy-astr.gsu.edu/hbase/spin.html#c4

    See also - http://en.wikipedia.org/wiki/Spin_(physics)

    http://www.lorentz.leidenuniv.nl/history/spin/spin.html

    The discovery of the electron spin by Samuel Goudsmit
    http://www.lorentz.leidenuniv.nl/history/spin/goudsmit.html
     
    Last edited: Oct 14, 2006
  15. Oct 14, 2006 #14
    With the proton accelerators, is that the same thing they are doing to try and find 'strings' of energy?

    And thanks Astronuc, I will surely read those.
     
  16. Oct 14, 2006 #15

    Astronuc

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    I am not aware of any experiments at the moment that are designed to test the concepts in 'string theory', at least that is the comment I have heard recently. I'll leave it to someone else to indentify any string theory related experiments.

    You're welcome.
     
  17. Oct 14, 2006 #16

    ZapperZ

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    String theories (and there are TONS of different versions of it) make no unique testable predictions at the scale of energies we can achieve at any and future colliders. They do, however, depend on the existence of the Higgs boson (often, several different generations of them), which is one of the tests that is achievable with LHC, but at the scale predicted within the Standard Model.

    All other inquiries regarding String should be addressed in the Beyond the Standard Model forum, not in here.

    Zz.
     
  18. Oct 15, 2006 #17
    another question---is this under hyper physics or quantum physics?
     
  19. Oct 15, 2006 #18

    ZapperZ

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    "Hyper physics"?

    Zz.
     
  20. Oct 15, 2006 #19
    i don't know....someone mentioned it earlier.
    I'm not sure whether it was in this thread or another.
    Anyway, under what branch of physics does study on anti-matter and all these sub-atomic particles fall into!?

    Ty
     
  21. Oct 15, 2006 #20

    ZapperZ

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    Quantum mechanics, Quantum field theory, etc...

    Zz.
     
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