[Towertalk] Magnetic North (sorry to start this again!)

[kk9a@arrl.net]

In the future, every compass on Earth may point south
because the world's magnetic field could flip. However,
researchers said there's no danger of airplanes, migrating
sea turtles or other magnetism-dependent navigators
suddenly getting lost -- this reversal will take place over
thousands of years, if it happens at all.
    Molten, flowing metal in the Earth's core generates much
of the planet's magnetic field. Like any magnet, the Earth's
magnetic field has two poles -- compass needles point
magnetic north while their other ends aim south.
     But within the past 150 years, the Earth's magnetic
"polarity" has precipitously declined -- the magnetic field
has not weakened, but compasses are less likely to point
 north.
     "This is an amazingly rapid change," said geophysicist
Peter Olson of Johns Hopkins University in Baltimore. At its
current rate of decrease, Olson said polarity would vanish
"early in the next millennium."
     Earth's magnetic field has reversed before. However, it
last happened 780,000 years ago -- soon after the island
of Hawaii emerged from the sea.