On 03/01/2010 10:54, andrew wrote:
Andrew Gabriel wrote:

The only way to use these is in nuclear reactors. The Sun is
one, the earth itself is one, and we have built our own too.


Parts of the earth were some sort of self moderating chain reaction but I
thought that was no longer self sustaining and it's just the decomposition
of unstable elements formed from then that keeps the middle warm now?

The mantle is kept hot by the radioactive decay of elements (mostly
uranium I think) which would have sunk down when the whole earth was
molten (as the iron did - hence the iron core of the planet).

You may also be thinking of the natural uranium reactor at Oklo, in
Gabon, about 2 billion years ago.

--
Tim

"That excessive bail ought not to be required, nor excessive fines
imposed, nor cruel and unusual punishments inflicted"

Bill of Rights 1689