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Non quantisation of gravity.

  1. Oct 29, 2011 #1
    Not sure if this should be in the quantum or classical forum, but as gravity has not been shown to be quantised yet...

    My question is this, seeing as there is no quantised theory of gravity yet, that would mean that if a single atom of say hydrogen residing on the surface of the Earth was moved radially away from the centre of the earth by a single angstrom unit, then it must be theoretically possible to calculate the increase in it's mass due to it's increased potential energy. Is this correct? If so how small is this number, in approximate orders of magnitude.

    If it is correct then the same must be true if instead of an angstrom unit it is moved by a mere Planck length.
  2. jcsd
  3. Nov 1, 2011 #2

    Jano L.

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    Why do you think the potential energy of small particle in a gravitational field would change its inertial mass? I think it will not.
  4. Nov 1, 2011 #3
    Are you suggesting that only it's gravitational mass that is increased? I just thought that potential energy manifested as mass increase, but maybe not for a subatomic particles maybe just for a system like a spring?

    But the main point I wish to understand is how it can be that there is any question that gravity is quantised. I mean how can it not be, if potential energy as a result of gravity is reliant on a measurement, and this measurement must necessarily be limited by the Planck length then gravity must be quantised, must it not?
  5. Nov 1, 2011 #4

    Jano L.

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    I think that neither inertial nor gravitational mass of the particle changes when it changes its position in gravitational field. In electrostatic field, particle has the same mass wherever it may be. It is the total mass of the whole system (source of the field) + particle that changes when the particle moves.

    Do you really think that potential energy is something that gets measured? I think it is just a theoretical concept, mathematically defined to be integral of motion of equations of motion.
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