John,
You and I differ in the following way. You, stick to physics. In this you still say that "space" is out there and you are content with this. I say "space" does not exist. "Space" is about knowing or conceiving a group of point as being at the same moment. No two points are at the same moment. The concept of "spacetime" is a bridge we built between the real universe and our reality in order to keep doing physics. The universe does not have this requirement.
The gravitational attraction between two celestial bodies is not direct or instantaneous. Each body affects its surrounding, and this effect is communicated from close to close around it, into the distance until touching the other body. At no moment is one body directly affecting the other.
We may understand better what the universe is and how it works if, for a moment, we step outside of physics. If we consider what IS instead of what APPEARS to be.
Also; -- "There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements.
(https://www.scientificamerican.com/article/why-is-the-earths-core-so/
(PV = NrT is not part of it)
Thanks,
Marcel,