Gravity at very large distance

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Is gravity at very large distances zero?

ie g = (k(m1 m2)/r^2) - k1 (you can also use the relativity formule for gravity here if you want)where k1 is some constant that makes gravity zero when (k(m1 m2)/r^2) reaches some threshold value

so if I had and electron 10^6 billion light years from another electron (ie the opposite ends of the universe or the furtherest distance possible (you choose)).

Now let's assume electron 1 is doing work, through gravity, on electron 2. I was wondering would the energy associated with the work electron 1 does on electron 2 be smaller than the smallest indivisibe unit of energy, which I think is planks constant?. Of course this assumes energy is quantised.

If you assume 2 photons can have a gravitational effect on each other then you can replace electron 1 and 2 with photon 1 and 2 at opposite ends of the universe.
 
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Using the inverse square law on 2 electrons 13.5 billion light years apart you get a force of 3.4x10-123N. I guess this would make the question pointless because by trying to measure the force QM laws would change your results any way. There isn't much point thinking about gravity in that way.
 
Those electrons would be via entangled, and gravity is universal.
 
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