I've read that in GR, gravity isn't considered to be a force, or that it's considered to be a fictitious force because its force is relative to the mass of objects, similar to the reaction forces of objects due to acceleration when the force is applied by contact from another object. How is this different than the nuclear strong and weak forces, or how is it significantly different than eletrical forces which are relative to charge? The common factor I see here is that no contact is involved with these forces. Also even in GR, gravity is different than acceleration with respect to time dialation. In the case of gravity, the time dialation is fixed, while in the case of acceleration, the time dialation changes with respect to changes in speed. Say there are two clocks, one on the earth, and one in a rocket, both initially at the same altitude from the earth's center of gravity. The rocket takes off, and then "hovers" (staying in line with earth's orbital path around the sun is close enough). An observer will then note that the clock in the rocket is moving faster than the clock on the earth because of the difference in gravity (difference in intensity of the field to be techincal). Now the rocket starts to accelerate at 1 g in an orbital path around the earth, maintaining a constant distance from the earth's center of gravity. As the rocket increases speed, an observer will note that the rocket clock is slowing, while the earth clock remains running at a constant rate. From this, the observer can see that there is a difference in time dialation between gravity and acceleration.