My pleasure gentlemen.
Sorry to do this to you, but, while pondering the meaning of special and general relativity, have a think about the core of gravity, mass, matter...everything!
“In this way, Einstein’s gravity can easily be looked upon as a fictitious force; in that the force itself is applied to spacetime and not the objects within spacetime. Whereas Newtonian gravity states that objects apply the force of gravitation between masses; which is direct. In this simple way, we can now see that gravitation is not the force itself, but the outcome of mass applying an influence on spacetime. So if we now apply this information to the unification idea, we see that there may be an issue in attempting to unify the equations which describe our three particle forces (strong, weak and electromagnetic), with equations describing a ‘secondary affect’, gravitation. And although this concept has been well understood for some time, the simple fact that we really do not understand why or how mass exerts influence over spacetime is a good reason to suggest that unification won’t happen unless we can answer the how and why questions in the first place... It becomes a somewhat complex issue to visualize, however, there is something very important worth pondering, as it is at the very heart of gravitation and perhaps relates to the construction of reality itself. If all the laws are constant and consistent throughout the universe, and through the activity of gravitation, mass can be moved whilst in uniform motion – a change observed from a separate frame of reference, brought about from the presence of matter and the subsequent warping (negative divergence) of spacetime - then what does the warping, where does the energy come from? Einstein side-stepped this issue, by stipulating that there is no absolute space or time in which we can measure relative aspects against, but gravitation is a field, and if so, a field held within what then? This is precisely where Einstein proclaimed the importance of the synchronization of the clocks comes into play, as it provides a way-out of the logic labyrinth. Also, how the metric changes at each point is spacetime, it is a though spacetime knows how much mass is there in the first place, as well as the density. The metric specifies how much spacetime needs to bend at any given distance and Einstein did incorporate conservation into the metric (Einstein tensors include the Ricci tensors by Gregorio Ricci-Curbastro, which in turn, include the Bianchi identity which defines conservation), but here again we must recognize that mathematics is only a language used in order to describe a physical process, it is not the process itself. I’ll give you an example; Einstein’s formulas for relativity consist of many parts, each representing different functions, such as the Christoffel symbols (Elwin Bruno Christoffel’s work on tensors), these provide a means of inserting forces into spacetime, without being affected by any changing curvature, and the derivatives, which calculate how the curvature must change according to the metric. These are all amazing mathematical structures, but they are no more gravity than these words are your understanding of them; mathematics is a descriptive language, it is not a physical act. So could it be, that at the fundamental level, some hidden energetic process exists, which coordinates both the bending of spacetime and the unaccountable quantum behavior as we will soon see, and might that mechanism be involved with other mystery processes? Some of the most recent theories are taking into account that spatial dimensions are perhaps another manifestation of energy (beyond that of a stress-energy tensor and mass-energy content), and in the same manner that energy can be converted to matter and back again, so too could spatial dimensions be enfolding and unfolding energy into matter.”