gravitation

The lumpy nature of the distribution of matter.

Theoretical physicists aren't forced to field the answer to this question at this moment in space time.

Yes. It's the LAW!!!

Yea Shul, I’ve often pondered that very q. Intuition suggests that matter pushes space out of the way, compressing it locally in what we call a gravitational field

If you do get the answer to your question, you will have halfway answered the question on what antigravity really is.

Space-Time is distorted by the presence of energy (matter is concentrated energy). Localized distortions of space-time (the gravity fields which surround objects) align themselves such that they are in the lowest energy (or highest stability) state. They accomplish this alignment by moving in relation to each other (free fall). If allowed to move without resistance their relational energy state is symmetrical and efficient (like a soap bubble forming a sphere). Those conditions produce the effect that we call gravity.