

Hot, Cold and Warm Ideas in Particle Physics 
Richard Feynman: "The possibility exists, therefore, that gravity itself is a pseudo force"
Let's imagine for a moment that electons have a negative charge and a positive mass, while protons have a positive charge and a negative mass.
The magnitude of the proton's mass is larger than the magnitude of the electron's mass, that much is known and is not disputed. This means that electrons move quickly in response to an electrostatic force, while protons move much more slowly.
We also know that electrons are attracted to protons and repelled by each other, again this is not disputed.
The crux of the matter is that if protons have a negative mass, they move away from electrons and not towards them. Because protons are much heavier, they don't move very far in response to orbiting electrons, but we expect them to move in the opposite direction to what is predicted by standard physics.
So what?
Well, if we put a large group of atoms near to another large group of atoms, an interesting thing happens.
The electrons are on the outside of the atoms and so come closer to their counterparts in the other group, at least when they're on the inwardfacing part of their orbits. This means that the net effect of the other group being there is to make the electrons move away from the other group, given that electrons repel each other.
The protons experience the same phenomenon, and move away from the electrons in the other group. However, the protons are heavier and so don't move as far. The net effect is that the electrons tend to displace towards the outwardfacing side. But given that protons move away from electrons, and their own electrons are much closer than the ones in the other group, they experience a net acceleration towards the other group after all. The electrons follow suit.
Could this be an alternative explanation for gravity?
When the groups of atoms are far apart, the electrons are displaced by a tiny angle towards the far side of the protons (on aggregate). The net acceleration is governed by the sine of this angle, which is proportional to the angle itself. The angle increases as the groups become closer together, but still remains tiny over a vast range of distances, because the gravity effect is small in magnitude. This leads to an inverse square law for anything other than small distances.
However, for small distances, the angle becomes larger and so the sine of the angle is no longer proportional to the angle itself, tending towards a maximum value of 1. In this case, the net acceleration experienced by the protons takes on a maximum value that is independent of distance.
With a bit of imagination, could this provide an alternative explanation for: