On Thu, 20 Nov 2003 17:46:55 -0600, "Steve Nosko"
wrote:


The NOVA the other evening said it is something like 200 to 700 million
years, I believe. (May have the multiplier wrong, but the significant digit
is what they said)

Off by three orders of magnitude. The average (100K-200K) is lower
than what has been observed (700K) since the last flip.


So, if the earth keeps on turning as it always has, the magnetic
polarities will continue their reversals as throughout history when man
did not exist or was too primative to record such events.
Best regards, Richard Harrison, KB5WZI

The NOVA was not too clear about how a rotating molten conductor
creates a field, but once you get one, I can understand how the field and
current in the core can cross couple and keep each other going.

Hi Steve,

This is an example of how generators used to work (when the battery
was dead). The "residual" magnetism within the iron bulk presented
enough excitation for a formerly motionless coil to cause current to
be generated. That current was then used in the excitation coil to
build a field that in turn created more current for a larger
excitation field - and so on. The term in electronics is called
variously as "bootstrapping," "fly-back," "buck-boosting," or
"bucking."

73's
Richard Clark, KB7QHC