Brace yourselves for gravitational waves

[Excited Penguin]

@Vorlon, let me get a bit technical to answer your question, if it is unintelligible I wil elaborate.

Yes, so in general relativity, the thing that carries the dynamics and contains the degrees of freedom of spacetime, is the so called metric tensor - a matrix of 10 numbers which tell us how far away two neighboring points in coordinate space are from each other physically. In approximately flat space and using standard cartesian coordinated, this metric tensor has just four components which boil down to telling you how to measure time and space distances.

It is these entries of the metric which get modified by masses and energy and thus mediate gravitation and also determine the movement of objects, and they are also the thing which the Einstein field equations determine. If you start with the metric for flat space,  and then consider small deviations from that and plug that into the Einstein field equations, you notice that these small deviations adhere to something like a complicated version of Maxwell's equation, and hence have wave solutions , sourced by changing mass and energy distributions.

I think I became a little smarter just reading this.