>This is your opinion, you dont know how the inner core/mantle relationship
>works. Havent you ever heard of an expanding sun? Things expand when they
>cool. Anyway, this is just a theory to back up the fact that the earth was
>smaller a long time ago. So, doesnt it seem obvious that the core is
>expanding into the mantle? The core is 3 times denser than the mantle. You
>say that the mantle flows in and out of the core, which of course you dont
>know for sure, but if this is true, at the same time couldnt less and less
>mantle be flowing back into the core? Think yourself!
The mantle is less dense than the core primarily because it's made of
different
material. The core is solid metal, mostly iron. The mantle is rocks
like silicates and carbonates. Solid metal weighs quite a bit more those
rocks.
Moving material from the core to the mantle or vice versa wouldn't change its
density. It would be the same stuff. However, it would be nearly impossible
because of the weight difference. Since the stuff is molten (more or less)
the iron would just sink right back to the bottom.