A science question

I have a science question. The Earth, as old as it is, is still quite hot in the middle. From what I understand, the crust is roughly 2-10 miles thick and the mantle is hundreds of miles thick before we get to the core. Volcanic activity shows us a hint of how hot be the innards. My question is this: Why does it take a planet so long to cool off? Anything baked in a ceramic kiln may glow red for a minute, yet may be cool in a day. If the earth is as old as they say, why is is still so darned hot on the inside?
Does anyone have an approximation of when the core will be cool to the touch? (Put in Geology?)This message has been edited by Phatboy, 01-26-2005 05:06 AM

Thanks for all of your replies! I never knew some of the science behind the innards of the planet!

Welcome to my evil lair...you will notice the spinning and very hypnotic disco ball as it pulls you in to my chamber of horrors...and in keeping true to the topic title, you will also notice my bubbling pit of very HOT MAGMA! Notice how the bubbles keep perfect tune to the hypnotic sounds of "Disco Hef" thumping in the background! AS WE enter my time machine, we will return to the middle ages where I will show you a much more stable time...how about a little D&D? This message has been edited by Phatboy, 01-27-2005 03:24 AM

LOL>>>I Knew that my Pac Man was fair game after I dissed your avatar! He is kinda corny, but He seems like a Phatboy just strollin around lookin for a discussion! I like him because he always smiles...something I need to work on!

I think that my science question was answered, Jar. The Universe is a fascinating place and to imagine that this dust speck of a planet that i am on is still so fascinating itself?! Still, my point of reference is not so much external as internal.Here is another question, however:
Have scientists ever dug deep enough to sample the mantle? In other words, can we ever probe beneath the crust? (of the Earth)