Is the Earth heated from within?

Does any of that heat inside the Earth have an appreciable affect on the surface?

Would the Earth be different if it had a cold core?

we won't have plate tectonics and magnetosphere

>Would the Earth be different if it had a cold core?
Yes, because we would all die of radiation. The moving iron/metal creates the magnetic field.

Ouch. Why? Would the big block of iron-nickel at the core not still be magnetic if cold? I know Mars isn't.

Of course, most of the heat radiated into space billions of years ago, but the fact the mantle is still hot enough to boil your skin off in a second shows the earth is still heated.

>YFW earth is a sun of fire inside a sun of ice.

Yes, I assumed this was the case, but wondered if there is still an appreciable heat radiation happening and if so how much; is it making a difference to us/life on the planet?

>He still believes the Earth is a sphere with a molten core orbiting the sun

this, the Earth is hollow

Earth's surface heat flux comes from radioactive disintegration in the mantle (66%) and from the core cooling (33%). (Percentages are raw estimates and widely discussed.)

On the magnetic field thingy, a magnetic field comes from the movement of an electric charge (that's what an electromagnet does). So, if the core was fully solid, it couldn't convect enough to maintain such a magnetic field.
Btw, the reason of mars' lack of magnetic field isn't a fully solidified core as most think, but rather the lack of plate tectonics, which "keeps the heat in", and so doesn't make a temperature difference in the core high enough for it to convect. Mars' core is believed to be fully molten.
(Sory if badly explained, english isn't my mothertongue.)