<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>How if the Earths core is hot does it create a magnetic field around earth, surely magnetism is destroyed by intense heat not created by it?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Heat would destroy bar-type magnets. But Earth's magnetism is not of that type. Theory says Earth's deep interior is a magnetic dynamo. In essence, this means that the organized motion of charges (i.e., currents) in the Earth's interior generate our magnetic field. These currents are made stronger by the intense core heat, not weaker.
I'm not altogether convinced by the dynamo theory because of its inductive-reasoning character. But I have no specific criticism to offer and nothing better to suggest in its place.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>Also, what are your views on the possibility of all fast spinning planets being hollow due to centrifugal force throwing all gasses / matter to the outer edges in the earths early stage of development?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
That idea arose from a misunderstanding of the laws of physics. At Earth's surface and the surfaces of all the planets, gravity is a stronger downward force than centrifugal force. That is fortunate because otherwise we might be thrown off into space.
As one goes down into the planet, on average, both gravity and centrifugal force drop off linearly with depth. [Centrifugal force [CF) is proportional to r (distance from center). Gravitational force (GF) is proportional to mass/r^2, where mass interior to radius r is proportional to r^3 for uniform density; so the net force is proportional to r^3/r^2, which is again just r.]
So if the planet had uniform density, and CF was less than GF at the surface, it must be less at every depth. But in reality, density increases toward the center, making GF larger than it would be for a uniform-density body, with no change in CF. This again works in the direction that GF is always greater than CF.
The fission theory for origin of planets and moons, which I favor, argues that as stars and planets cool and contract, they spin up until they finally reach overspin. If that happens, the most vulnerable places (the body's surface) will have CF > GF and will fission, creating one or two satellite bodies. But that process must work at the surface, not the interior, because of uniform or increasing density with depth. And we know that interiors are not hollow because of gravity field measurements made by observing natural moons or spacecraft moving in the body's gravitationl field. So despite entire books being written about "hollow planets", the idea is in hard conflict with the data in hand interpreted with the simplest models.
I, for one, do not favor replacing simple explanations with more complex ones, such as hollow planets that hide their mass distribution from observers by some subterfuge. -|Tom|-
