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Gravity at a microscopic level

  1. Feb 24, 2009 #1
    Hi all,

    I was wondering what effect does gravity have on a subatomic particle? I know that physicists have been searching for a theory that combines quantum mechanics and gravity but at a smaller scale, I am guessing gravity has a tiny non zero force?

    If the answer is not known, could someone tell me what ongoing theories speculate about the nature of gravity at such small scales?
  2. jcsd
  3. Feb 24, 2009 #2


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    Well the most famous is of course string theory, and if you have not heard anything about candidates for gravity at quantum level this is nice introduction: http://en.wikipedia.org/wiki/Quantum_gravity

    You might also want to check out the forum beneath this one "Beyond the Standard Model", there might be similar questions asked there. Also try the search tool on this forum :-)
  4. Feb 24, 2009 #3

    Vanadium 50

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    People have measured the gravitational attraction of single neutrons.
  5. Feb 24, 2009 #4
    The first successful attempt at detection are referred to as the COW experiments (Collera, Overhauser , and Werner- 1975) and used neutron interferometry to show that earth"s gravitational potential changes the phase of the wavefunction of neutrons.

    It is more technically referred to as gravitationally induced quantum interference, and shows that both h and G are determinants of the neutron's behavior.
    Some have used this to demonstrate microscopic equivalence Princ. but I think the implications are deeper.
    It opened up some interesting areas of research.

    More recent "COW" Type exper....http://www.sciencedirect.com/scienc...serid=10&md5=a0b29ba6b79fd82e3b3c2fa17fcfaed2

    Last edited: Feb 24, 2009
  6. Feb 24, 2009 #5
    It would be interesting to find out exactly how it would work
  7. Feb 24, 2009 #6
    Re: Gravity at a microscopic level...Holy COW

    With respect to COW...In this article..Page 214- 215... For a particle in the earth's rotating/accelerating frame the neutron's Lagrangian, Hamiltonian, Eqns. of motion, and phase shift are developed.


    In other more recent exper., 'confined' neutrons falling in earth's g field are shown to be unable to fall continuously, but must take quantum jumps, and are not found at certain heights.....fitting QM expectations.

    see: http://www.nature.com/nature/journal/v415/n6869/full/415297a.html


    P.S. I think this thread should be moved to the quantum or gravitational physics section.
    Last edited by a moderator: May 4, 2017
  8. Feb 28, 2009 #7
    Related, unresolved issues are: Does gravity obey the inverse square law at sub atomic scales? Does gravity exist at sub Planck length scales??
  9. Feb 28, 2009 #8
    Do you mean one neutron being attracted by the earth, or the mutual gravitation between a pair of individual neutrons?
  10. Mar 1, 2009 #9

    Vanadium 50

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    One neutron and the earth.
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