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MOND and expansion of universe

  1. Jul 21, 2004 #1
    The gravitational force acting on a particle of mass m, on the
    surface of a sphere of radius 10^26 metres and with a mass of 10^52
    kg is given by
    G x10^52 m / (10^26) ^ 2

    The acceleration is given by G x10^52 / (10^26) ^ 2 = 10^ - 11 m/ s^2

    This is the magnitude of accleration at which modified newtonian dynamics
    becomes a mathematically accurate description of the velocities of stars in spiral galaxies.MOND describes a gravitational force that is stronger than
    the usual Newtonian expectation.As the universe expands beyond 10^26 metres,
    if MOND is valid as a force law,then we should expect the acceleration of the expansion of the universe at distances greater than 10^26 metres,to be slower than expected.Does anyone agree with this?
  2. jcsd
  3. Jul 22, 2004 #2
    Please clarify what this MOND is.
  4. Aug 22, 2004 #3
    The decceleration due to gravity at 10^26 metres is about 10^-11 m/s^2
    using the Newtonian calculation.
    This is of a similar order of magnitude to the acceleration
    of supernovae due to dark energy at this distance (10^-10 m/s^2).
    It is as though gravity has changed signs.This may be a trivial point or it may not.What if the gravitational force carrier comes in particles with two spin states (associated with mass and not charge),one spin positive and the other, of the same magnitude, but negative sign,which exist in a field (could be gravity's own field if force carriers self-interact like gluons), and the high energy spin state is becoming the low energy state, and the low energy state is causing gravitational repulsion (and will cause more repulsion as time goes on and more low energy states form).In a galaxy such as ours, anomlously high star velocities could then be caused by there being fewer low energy repulsive states than expected, and with all the
    radiation that a galaxy contains, most low energy spin states could be promoted to high energy states by the radiation.
  5. Aug 22, 2004 #4


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    The numerology version.
  6. Aug 22, 2004 #5
    Modified Newtonian dynamics.
    Basically the newtonian law F =ma can be modified to give a stronger gravitational
    force so that anomalously high orbiting velocities of stars in galaxies can be explained.
    The velocities should get smaller with increasing distance from the galactic centre
    but they don't - they stay constant.
  7. Aug 22, 2004 #6
    What if the source of this high perimeter orbiting velocity is due to external pressure, rather than internal attraction?
    We accept that space is expanding, but if the universe is stable, then the only option for the resulting pressure would be to affect existing structures.
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