Earth’s magnetic field does more
than makes compasses point north. It also protects us against dangers from
space, specifically solar wind and cosmic rays. Without our protective magnetic
shield, the solar wind could strip away much of our atmosphere, as occurred on
Mars. As the atmosphere diminishes, the oceans slowly evaporate and become lost
to space, as on Mars.
Earth’s hot, liquid-iron interior
generates our magnetic field. The liquid core of Earth gets so hot that
electrons are stripped off the molecules. As the charged particles spin around
with Earth’s rotation, it generates our lifesaving magnetic field. But, Mars,
being smaller, cooled long ago, the core solidified, and it no longer generates
a magnetic field, hence its cold, dry, virtually lifeless surface.
Earth’s magnetic field isn’t as stable as it might seem. Over long periods of time, it flips with magnetic north and south poles reversing. During that magnetic flip, the magnetic field can become significantly weaker.
Such a magnetic pole reversal
occurred 42,000 years ago. Researchers of the University of New South Wales studied the event. Chris Turney, a co-author of the
study, explained “Earth’s
magnetic field dropped to only 0 to 6% strength during the event. We
essentially had no magnetic field at all. Our cosmic radiation shield was
totally gone.” That event coincided with the extinction of many species,
including the Neanderthals. Scientists are still trying to work out just how
much the reversal affected those now-extinct species.
Although such magnetic reversals
generally occur on timescales of a few hundred thousand years, geoscientists
have found ample evidence that such a reversal may already be underway. Pole
wandering, or the movement of the magnetic poles, is more pronounced than in
the past. Over the last 170 years, Earth’s magnetic field strength has
decreased by 9%.
At the very least, a severely
weakened magnetic field can cause total malfunction of communications and all
other satellites and will be dangerous, perhaps even lethal, to any
astronauts. At its worst, it could dramatically increase animal extinctions and
severely affect human health. No one can say for sure if or when a magnetic reversal will occur,
how long it might take, and how long it would last. But, the geologic record
paints a potentially grim picture.
Each month, I write an
astronomy-related column piece for the Oklahoman newspaper. On the following
day, I post that same column to my blog page.
This is reprinted by permission from the Oklahoman and www.newsok.com.
