I have read that the Earth has a semi-solid iron body at its core, even though that object is surrounded by liquid magma.... I'm wondering if this is because of a pressure (and resulting temperature) differential -- or if there is another reason.
1) Since the forces of gravity of a sphere are at equilibrium at the center of the sphere -- doesn't that mean that the pressure at the mass center of a planet would be zero -- since there would be no "force" to be distributed at that area?
If the answer to #1 is true, then it leads to these further questions....
2) At what point between the surface and the center of the planet would the pressure be the greatest?
3) Would the depth in the Earth, at the max. pressure point specified in #2, be where we would expect to find the central layer of the Earth's magma? -- (Since pressure generates heat, wouldn't that be the hottest point; from a "pressure variable only" view?).
4) Shouldn't it actually be cooler at the Earth's mass center, than at the max. pressure point specified in #2 -- since the pressure is lower at the mass center?
4.a) And could that center temperature be enough cooler that it allows a core body to semi-solidify?