If the core is 1,000 miles in diameter, the forces required
to actually tumble the semi-solid material, overcoming the
friction with mantle and the gyroscopic forces would be so
great that the Earth would not survive. In fact, I have a
theory.

The planet Venus orbits the Sun in the same direction as all
the other planets, but it rotates backward. I think Venus
was a wanderer and struck the Earth, knocking it into the 23
incline, slowing Venus enough to be captured in the Sun
gravity as an orbiting planet and also giving Venus its
backward rotation. This collision also created the Moon.


--
James H. Macklin
ATP,CFI,A&P

"Bob Fry" wrote in message
...
| "RR" == Ross Richardson
writes:
| RR What this program stated and I had read it
elsewhere, is the
| RR magnetic core within the earth had flipped every
200K to 700K
| RR years. Geologist know how to figure this out from
core
| RR samples.
|
| Not from core samples. We've come nowhere near the
earth's core.
| Rather, from now-solid rock that was previously molten and
iron
| particles free to align to the earth's magnetic field; get
enough of
| those samples which were molten at different geologic
periods and you
| can figure out the history of the earth's magnetic field.