Monday, January 29, 2018

The Earth's magnetic poles are switching - just not quite yet

Difficult as it is to believe at first blush, the Earth's magnetic changes over the millennia, and the magnetic poles even completely switch from time to time. In fact, we are long overdue for a pole change.
In fact, the geological record shows us that the Earth's magnetic poles have reversed - so that the North pole becomes the South pole, and vice versa - many times over its history. On average, the poles flip every 200,000 to 300,000 years, which in geological terms is the merest blink of an eye. On many other occasions, it starts to flip but then doesn't succeed, snapping back again. The last such "excursion" (unsuccessful flip) was as recently as 40,000 years ago, around the time that anatomically modern humans were making cave paintings in southern Europe. The last time there was a complete pole switch (before which time, North was South and South was North), was around 780,000 years ago, though, long before Homo Sapiens arrived on the scene. We are, therefore, statistically long overdue for a full switch.
Is there any evidence of this happening? How would we know?
The Earth's magnetic field is generated by the spinning of its molten iron and nickel core. If sufficient energy is drained from the dipole at the edge of the molten metal core, then the dipole will be weakened enough for the poles to switch. Currently, the Earth's magnetic field is in fact weakening, and has lost about 10% of its strength over the last 200 years or so, The North magnetic pole is especially turbulent and unpredictable, and has moved by nearly 1,000km since it was first accurately identified in the early 19th century, and, what's more, its movement is accelerating (now around 60km/year). There is also a region between about Zimbabwe and Chile known as the South Atlantic Anomaly, where the magnetic field is already so weak that it presents a distinct hazard for satellites that orbit above it, and where the polarity is already reversed. However, if a switch is underway - and that is still no scientific consensus - bear in mind that the process could take many centuries.
As the magnetic field weakens during a switch, the least of our problems would be that compasses no longer work. The magnetic field shields the planet from harmful solar and cosmic rays, and so this protection - which stops our water from boiling away, and makes life on Earth possible - would also weaken. Gradually, our atmosphere would be stripped away, with disastrous consequences for the Earth's surface, rendering entire regions uninhabitable and causing mass species extinctions. Orbiting satellites would be the first to suffer from this radiation, affecting the satellite timing systems that control our electrical grids, and causing widespread crashes and blackouts. Our increasingly power- and technology-driven lives would be irrevocably impacted.
On the plus side, that same technology should allow us to monitor major changes in the magnetic field, and hopefully make compensatory changes to our satellites, electricity grids and communications networks. And, of course, we will have to prepare for a world where North is South and South is North. Hell, it could be the thing that finally brings us all together. At the very least, there is a good Hollywood blockbuster in this (I am surprised it has not already been made). And if you are really searching for a silver lining, take comfort in the knowledge that, as the magnetic field weakens, the Northern Lights should become increasingly dramatic and easily visible. Feel better?

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