How is the core of the Earth kept hot?

[Forestman]

I know that the mantel of the Earth is kept hot by radioactivity, but is this also true for the core?

 

[sylas]

Yes.

Addendum. Most of the radioactivity is in the crust and the mantle; but this is still generating heat which contributes to keeping the core hot. For lots more detail see Probing Question: What heats the Earth's core? at physorg.com

So the core is not being kept hot by radioactivity in the core; the energy from decay in the mantle and crust is more important. I had to look this up also.

 

[Forestman]

Thanks sylas.

 

[budd]

does the Earth gain significant heat from the moon and the suns tidal pull?

 

[Xnn]

The link that sylas provided list 4 sources of heat within the earth.

Up to 90% of the heat is from radioactive decay.
About 5 to 10% is from friction caused by gravity.
About 5 to 10% is residual left over from the original formation of earth.
A small amount is latent heat released when molten materials turn into solids.

As I understand it, tidal push and pulls are part of the 5 to 10% gravity friction portion.