So I was in the shower today...

[Zack]

Pressure in this sense is CAUSED by gravity. You may notice that vibrations don't tend to pass through liquids very well,. as the liquid absorbs it. Very dense solids of such size/mass as the core probably wouldn't vibrate either. Why not go watch "The Core" again and tell me how accurate you think it is. The outer core may not be dense, but more like a vapour of superheated gases eminating from the core due to possible fusion/fission reactions. So why doesn't the mantle and crust fall into the centre through the vapour? Perhaos it is at a very slow rate? My theory is that the outer layers of the earth are in ORBIT around the inner core, with a buffer of superheated gas vapour between them.

The movement causes a centrifugeal force upon the outsides of the planet. Well, why aren't we being thrown off at 1000km/h? Gravity. Stop the earth spinning and you lose the centrifuge... gravity seems that much stronger.

I wonder if astrophysicists have accounted for this too?

Oh yes.
Take a look at pulsars. They are spinning so fast, and these objects have small dimensions, that it tells you something about how dense they must be not to be torn apart by centrifugal forces.