Read Kim Stanley Robinson's "Mars Trilogy". All your questions will be answered, and in the context of entertaining sci-fi no less!
This looks interesting! Tnx!
SeraphimLabs, I did find
that Earth's Interior documentary, and added the link at the bottom of this post.
It said Earth's core is super-hot ultra-compressed metal and it generates a magnetic field by spinning.
Either by that alone or possibly also by interacting with the Sun's field.
If you don't mind, I'll branch out here and mention the EU (Electric Universe) theory, which is that the Sun is powered not by fusion, but by vast external galactic electrical fields.
The idea is that, from Earth, the field is too dilute and spread out to detect, and the Earth and planets too small to attract enough electrical flow to 'light them up'.
But the Sun is large enough to attract sufficient electrical flow to cause it to light up.
To me, three phenomena support this idea:
1) The Sun's corona is at a million degrees, far hotter than its surface.
The corona is outside of the Sun's surface.
Logically, the closer to the Sun you go, the hotter it should be, not cooler.
2) Sunspots, 'holes' in the Sun's surface, and 'windows' to its interior, are cooler and show black in images.
If the Sun was internally powered, I should expect sunspots to show hotter.
3) Barred spiral galaxies.
On Earth, nature abhors a barred spiral; whirlpools in water, in tornadoes, in hurricanes, do not have barred spirals.
Yet there are vast spiral galaxies which support barred spirals; I think this may be connected to EU theory too.
Anyways, that's the EU theory for you.
Edit - Update: Inside Planet Earth