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Like the plot of a sci-fi B movie, something weird is happening deep
underground where the constant spin of Earth's liquid metallic core generates
an invisible magnetic force field that shields our planet from harmful
radiation in space. Gradually, the field is growing weaker. Could we be heading
for a demagnetized doomsday that will leave us defenseless against the lethal
effects of solar wind and cosmic rays? "Magnetic Storm" looks into our
potentially unsettling magnetic future.
Scientists studying the problem are looking everywhere from Mars, which
suffered a magnetic crisis four billion years ago and has been devoid of a
magnetic field, an appreciable atmosphere, and possibly life ever since, to a
laboratory at the University of Maryland, where a team headed by physicist Dan
Lathrop has re-created the molten iron dynamo at Earth's core by using 240
pounds of highly explosive molten sodium. The most visible signs of Earth's
magnetic field are auroras, which are caused by charged particles from space
interacting with the atmosphere as they flow into the north and south magnetic
poles.
But the warning signs of a declining field are subtler—though they are
evident in every clay dish that was ever fired. During high-temperature baking,
iron minerals in clay record the exact state of Earth's magnetic field at that
precise moment. By examining pots from prehistory to modern times, geologist
John Shaw of the University of Liverpool in England has discovered just how
dramatically the field has changed. "When we plot the results from the
ceramics," he notes, "we see a rapid fall as we come toward the present day.
The rate of change is higher over the last 300 years than it has been for any
time in the past 5,000 years. It's going from a strong field down to a weak
field, and it's doing so very quickly."
At the present rate, Earth's magnetic field could be gone within a few
centuries, exposing the planet to the relentless blast of charged particles
from space with unpredictable consequences for the atmosphere and life. Other
possibilities: the field could stop weakening and begin to strengthen, or it
could weaken to the point that it suddenly flips polarity—that is, compasses
begin to point to the South Magnetic Pole.
An even older record of Earth's fluctuating field than Shaw refers to shows a
more complicated picture. Ancient lava flows from the Hawaiian Islands reveal
both the strength of the field when the lava cooled and its orientation—the direction of magnetic north and south. "When we go back about 700,000
years," says geologist Mike Fuller of the University of Hawaii, "we find an
incredible phenomenon. Suddenly the rocks are magnetized backwards. Instead of
them being magnetized to the north like today's field, they are magnetized to
the south."
Such a reversal of polarity seems to happen every 250,000 years on average,
making us long overdue for another swap between the north and south magnetic
poles. Scientist Gary Glatzmaier of the University of California at Santa Cruz
has actually observed such reversals, as they occur in computer simulations (view one in See a Reversal).
These virtual events show striking similarities to the current behavior of
Earth's magnetic field and suggest we are about to experience another reversal,
though it will take centuries to unfold.
Some researchers believe we are already in the transition phase, with growing
areas of magnetic anomaly—where field lines are moving the wrong way—signaling an ever weaker and chaotic state for our protective shield.
Geophysicist Rob Coe, also of the University of California at Santa Cruz, may
have even found a lava record in Oregon that charts the magnetic mayhem that
ensues during a period of reversal. The picture that emerges may not be up to
Hollywood disaster standards, but considering that human civilization has never
had to cope with such a situation before, it could be an interesting and
challenging time.
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Is the magnetic shield (shown in blue above) that protects our planet from harmful radiation originating in the sun about to undergo a major transformation?
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