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Gravity at atomic levels, first time post

  1. Oct 27, 2003 #1
    I have very little training in the area of Physics, but enough to understand most of what is said on this forum. This is a first time post.

    My question has to do with gravity on an atomic level. This question is for those of you familiar with trying to combine all four natural forces.

    First these are a few things I understand to be true:
    1 Gravity is the weakest of the 4 natural forces.
    2 The current problem with the unified field theory is combining all 4 forces into one equation.
    3 We can currently combine strong nuclear force, weak nuclear force, and electromagnetism into one equation.
    4 Gravity is actually the result of a body of mass bending space-time.

    My question is this…
    Is space-time elastic and if so does it have a critical mass needed to bend it?

    For instance if a bowling ball or a cannon ball is set on a trampoline, the trampoline will bend. But, if a grain of sand is set on a trampoline it will not bend the material. Could this example parallel real space-time? A star has enough mass to curve space-time, while and atom or a particle does not. I believe that if this is the case, that a lot of the problems due to using gravity on an atomic level would be solved.

    This may not be a new idea. I have not the foggiest. Please lead me to any research already done on the subject or give me your own expertise on the subjuct.

    Thank you,
  2. jcsd
  3. Oct 27, 2003 #2
    In general relativity, any amount of mass-energy will curve spacetime. It is not really correct to think of spacetime curvature as "elasticity".

    I don't know any theories which introduce a mass cutoff in the source of gravity. It would be very difficult to construct a theory, to explain in any kind of natural way how individual atoms do not gravitate, but a large collection of individual atoms does gravitate. Moreoever, we have no evidence of such a cutoff.
  4. Oct 27, 2003 #3


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    A small correction: no. 3 is not correct, you can combine electromagnetism and the weak nuclear force intgo the electroweak theory, but you cannot combine this with the strong nuclear force which is explained by quantum chromodynamics, though QCD and the electroweak theory make-up what is known as the stadard mnodel (to be unifired into some yet-unknown 'grand unified theory').

    In general relativity there is no minimum mass required to bend space-time. General relativity cannot howver be the full picture as it is incompatible with quantum theory, so how exactly v.small masses affect space-time is unkown, though seeing as the curvature of space-time is what virtually defines mass in GR yu'd have to ask the menaing of a mass that doesn't cause such curvature.
  5. Oct 27, 2003 #4
    I did not know that, is there any further reading you can point me to
  6. Oct 27, 2003 #5


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    Staff: Mentor

    That CAN be true, but it isn't always true, In a trampoline, a grain of sand will most certainly push down the trampoline, just by an amount too small to measure. Springs can be coiled with a force pushing the coils together, which is where the initial force required to move them comes from. Its part of the equation for force on a spring. But not all springs act that way.

    Interesting possibility though (sorry, but I can't comment on the validity of it - out of my field).
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