I do not have a great math background. However, the more I read about Relativity, the more it appears intuitive. If I understand correctly, gravity is not yet fully understood, at least not as well as is velocity, distance and time differences in different relative frames. Any example I have ever seen explaining why a clock (matter) experiences v t and d differently as viewed by another frame, has used examples of the clock moving at some speed compared to the other clock, in whatever direction: there is always a change in distance between the two somewhere in the example, and a difference in speed(v). I guess thats why they are in different inertial frames. So it appears relativity differences in v t & d require a change in distance between the compared objects? Does it make sense then if you imagine a large planet (say the Earth) spinning on its axis, and imagine a rock sitting on the surface at the equator. Now imagine you could burry a rock of equal mass at a location* half way down between your surface rock and the exact center of the earth. As the earth rotates, the surface rock is moving thru space faster than the burried rock from the burried rocks perspective, but there is no change in the distance between the two rocks. However, are not the two rocks experiencing centrifugal force a little differently than one another? Are they part of the same inertial frame? Also, From The burried rock's perspectice:Is not the surface rock moving faster and further thru space? Would the surface rock's clock move slower? Would its mass increase per E=mc2)? In a rotating sphere, Is there more and more energy with each layer? (a layer being all rocks an equal distance from the center, along th equater. Can you consider each "layer" of a rotating sphere as described above its own seperate inertial frame? Using these ideas, If you imagine as described above that there is more and more mass (energy) in each layer away from the center of a rotating sphere, then as a whole, is the sphere in a state of energy imbalance? Would the energy want to "equalize" towards the center, thereby "pushing" all the rocks (Atoms?)together? If this "pushing" force were greater than was needed to keep the sphere in an energy equalibrium, would the force "look" for other mass(energy) to bring (pull?push) into the center? If light (energy) passed by would this force try to "grab" it? If Another planet came too close? The Moon? Even without rotation, is there more energy at the surface of a body of mass than in the center, if you apply these ideas to each individual atom as being a frame of referance, rather than the layers above. If you start at the center of any object, there will be more and more atoms at each spherically measured distance point, or layer, (measured in all directions - measured points of each layer would look like the shell of a sphere, each layer one atom bigger in an outwrd direction) away from that center. I think this model would lead to the same as above. Any thoughts. Am i an iiot?