On Wed, 25 Oct 2006 17:14:05 -0700, Bob Fry
wrote:

"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.

Core samples as in core samples, but not samples from the core.
Core samples are just samples cut with a circular or pipe like drill
from which they remove the "core". Much like coring an apple.


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.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com