I think that Gravity is a constant, regardless of your position, as it is something that is determined by mass and your electromagnetic relativity to masses that are greater and lesser than your own - and fact this determines our ability, as a celestial body, to remain in orbit without hitting other planets/moons.
Each celestial body emits its own electromagnetic field, which repells the other electromagnetic fields and the basic rule is that the smaller mass will move out of the way of the greater mass. Ie, Jupiter didn't move out of Mars' orbit, Mars moved out of its orbit.
In saying this, i'm trying to demonstrate how Gravity therefore, is a constant, but centripetal and centrifugal forces are not necessaryily.
The inner section of the rim of a bicycle spins with the same inertia/gravity as the outer rim, regardless of how fast it is moving - as with the centre of the earth, which would have different forced being applied over different time and space relatives to the outer rim of the earth.
