On 12/12/2012 09:04, Szczepan Bialek wrote:

The only "cause" of the metal core is the calculated density 5.5.

No, a metal core rather helps to explain the magnetic field. Plus,
analysis of earthquakes
gives good information on internal structure of the earth.

And we have had similar sensors on the moon, confirming the absence of a
metal core. One
of the surprises from the Apollo programme was how little "damping"
there was for lunar
vibrations set up by deliberately crashing the orbiter.