It's more about the parent physics, than about the daughter, geology.
In one word, it is gravity, In one phrase, light things float, heavy things sink.
A hollow earth contradicts everything known or ever observed about gravity, therefore every appeal to a hollow earth is an appeal to magic.
As to present knowledge, it is essentially known that the outer core is liquid is due to the actions of pressure waves relative to shear waves. Liquids do not transmit shear waves. That is why an earthquake on the opposite side of the earth shows a giant hole when the profile of such an upset is compared through several geographically distant geophysical stations.
As to the inner core being solid, this is due to the observed reflection of pressure waves going from solid to liquid, to solid under all experimental conditions, therefore it is presumed that the same attributes of sound waves act the same in the deep earth as it acts everywhere else.
There you go, either physics or what Holden Caufield referred to as 'phonies.'
The idea of the sacred is quite simply one of the most conservative notions in any culture, because it seeks to turn other ideas - uncertainty, progress, change - into crimes.
Salman Rushdie
This rudderless world is not shaped by vague metaphysical forces. It is not God who kills the children. Not fate that butchers them or destiny that feeds them to the dogs. It’s us. Only us. - the character Rorschach in Watchmen
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