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Antimatter and Gravity

  1. Jun 6, 2010 #1
    Standard physics texts assert that antimatter expresses a normal attractive gravitational force. Has this been proven by any experiments, or only asseted in the current theories? We know from experiments that antimatter has the opposite charge, but could it also have the opposite gravitational force?
     
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  3. Jun 6, 2010 #2

    Doc Al

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    We know what 'opposite charge' means, but what does 'opposite gravitational force' mean? Antimatter has mass, just like normal matter.
     
  4. Jun 6, 2010 #3
    Nobody seems to know for sure whether gravity is a "force" or whether it's just a skewed arrangement of spacetime
     
  5. Jun 6, 2010 #4

    Vanadium 50

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    If antimatter attracted differently than matter, this would appear as a composition dependent gravitational force and show up in Eotvos-type experiments. But no such effect is seen.
     
  6. Jun 6, 2010 #5
    If we define regular gravity as a warping of space in an 'down' direction, then the opposite gravitational force would warp it in the 'up' direction. I think that this would cause two antimatter masses to push away from each other. If this were true, then no antimatter stars could form, and only anti-hydrogen would exist after the Big Bang.
     
    Last edited: Jun 6, 2010
  7. Jun 6, 2010 #6
    Have there been Eotvos-type experiments using antimatter? I thought that because gravity is so much weaker than the electrical force, that this kind of experiment could only be done on an electically neutral mass like antihydrogen. I know that at CERN they have just begun to create antihydrogen, but I wasn't aware that they had done an Eotvos-type experiment.
     
  8. Jun 6, 2010 #7

    IIRC the only thing that could warp gravity up (that we currently know of) is exotic matter, which hasn't ever been proven to exist.
     
  9. Jun 6, 2010 #8
    This brings me back to my original question. I know that there is no proof that antimatter expresses an opposite gravitational force using exotic matter or whatever it might take. But on the other side, is there any proof that antimatter could absolutely NOT express an opposite gravitational force from normal matter?
     
  10. Jun 6, 2010 #9
    Hi sineal;
    To answer you directly.... No, antimatter's gravitational interaction has NOT been yet proven experimentally.

    Experimental delay, as you correctly deduced, has been due to the relatively large electromagnetic force (compared to the weakness of gravitational) which overwhelms any sensitive measurements.

    It is a very important experiment and needs to be done....
    The best hope will probably be using neutral cold antihydrogen; as you mentioned:
    http://www.fnal.gov/directorate/program_planning/Mar2009PACPublic/AGELOIFeb2009.pdf

    That would be anti-gravity and historically the arguments "against" have been to adddress the ANTI-gravity possibility.

    However, .....
    ... I agree with the Los Alamos guys that say the various arguments against "ANTI-gravity" have not been sufficient to " rule out a large anomalous gravitational response for the antiproton",...meaning there could still be the possibility for "non-Newtonian" and "non-Einsteinian" gravitational response....and so an experiment is "critical" for our improved knowledge of the gravitational force.
    A good review of the arguments and their statements are given here:
    http://www.sciencedirect.com/scienc...serid=10&md5=284661d6f21b4fdc7f31fdf766194aa0

    Creator
     
  11. Jun 6, 2010 #10
    Here are some experimental efforts described from:
    http://en.wikipedia.org/wiki/Antimatter#Origin_and_asymmetry



    Positron production at the Lawrence Livermore Lab is described further on ....I'm guessing once again that gravitational effects have so far been too small to detect...
     
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