Geomagnetism: "Magnetic Pole Holds Elusive Allure"

"Magnetic Pole Holds Elusive Allure"
by the Sydney Morning Herald

"The Hollywood disaster movie 2012 got a lot of things wrong, an expert on the Earth's magnetism tells Steve Meacham. Dr Charlie Barton - the Australian scientist who 10 years ago became the closest anyone has been to the constantly moving south magnetic pole - has never seen Roland Emmerich's apocalyptic adventure movie 2012, starring John Cusack. He knows the film was much criticised when it opened last year, particularly by scholars, who objected to it portraying ancient Mayan mathematicians prophesying 2012 as the date of the end of the world as we know it. But Barton's reasons for not seeing it are different: the science is flawed.

Sure, says the Canberra-based geomagnetist, sun spots and other solar activity have an immense - and little-understood - effect on the Earth's ability to sustain human life. And yes, it is true (as the movie shows) that the planet's magnetic poles will eventually reverse as a result of dramatic changes in its molten core, leading to north becoming south and vice versa. Barton also concedes that a switch of magnetic poles is well overdue. According to geological evidence, the poles trade places every 250,000 years on average. The last time it happened? About 780,000 years ago. The magnetic poles - the two points where the Earth's magnetic field is exactly vertical to its surface - have fascinated mankind since 1600, when an English physician, William Gilbert, deduced that the Earth itself acts as one great magnet.

In an age before the global positioning system, when navigators relied on compasses, the precise locations of the two magnetic poles were of far more practical use than the whereabouts of the geographical poles, around which the planet spins. Eventually, scientists worked out that the Earth's magnetic field was caused by a liquid - molten iron - sloshing around the core. But since the liquid was constantly moving, so were the magnetic poles. In fact, in the past century the south magnetic pole has drifted an estimated 1140 kilometres north-east - from the continent of the Antarctic to the open sea. Some experts conclude that, in 300 years, it could reach Adelaide.

"Quest for the South Magnetic Pole" is the title of an exhibition developed in Adelaide and opening in Sydney on Friday at the Australian National Maritime Museum. Australians, not surprisingly, have led the way with expeditions to research the south magnetic pole. The trio credited with ''discovering'' it were members of Ernest Shackleton's 1907-09 expedition to become the first to reach the geographical south pole.

Two Australians, Douglas Mawson and T.W. Edgeworth David, plus a Scot, Alistair Mackay, got within 130 kilometres of the magnetic pole and planted their flag, an event that was honoured on a stamp earlier this year. The conditions they endured were recorded by the Australian photographer Frank Hurley in another attempt by Mawson's first Antarctic expedition of 1911-14. By contrast, Barton admits he did it easy in 2000. He cracked open a bottle of champagne and enjoyed a meal with adventurer Don McIntyre and others aboard the Sir Hubert Wilkins when he came the closest humans have ever been to the south magnetic pole - 1.6 kilometres.

Barton, a visiting fellow at the Australian National University, will talk to museum members and the public about his part in the quest tomorrow. He will explain how his electronic, 3D compass - officially known as a fluxgate magnetometer and unofficially as "Charlie's Angel" - came to be a centrepoint of the exhibition. ''I was looking for a very cheap way of being able to make very sensitive measurements of the horizontal aspects of the magnetic field,'' Barton says. ''As you get closer to the magnetic pole, the horizontal measurements get weaker and weaker because the field turns exactly vertical when you are at the pole.''

His 25-year quest to get closer than anyone else to the pole was realised when McIntyre allowed him to piggyback on his 2000 expedition to Antarctica. But despite the complex science, Barton admits one factor in finding the pole: ''You have to be just plain lucky.'' Describing conditions as a reverse ''perfect storm'', Barton says, ''When you get sunspots, they can change the [position of] the magnetic poles on a quiet day by 20 kilometres. On a typical day that becomes 50 kilometres. And on a disturbed day by up to 1000 kilometres or more. We were extremely lucky because we had abnormally quiet conditions.'' But, of course, if he were to go back to the same spot 10 years later, the magnetic pole will have moved.

Getting back to 2012 and some of the doomsday theorists, Barton admits ''we are three times overdue'' for the south and north magnetic poles to switch. Those who support the theory that we may be going through such a switch point out that in the past, the Earth's magnetic field has become weaker and weaker before the switch takes place - a transition that takes an average of 5000 years. Barton concedes the Earth's magnetic fields have weakened in the past 2000 years. Both magnetic poles are further away from their geographical equivalents than usual. Five degrees of the Earth's surface is considered normal; the gap is now 10 degrees.

The end is nigh, then? ''Would you like me to tell you why we're not going to see the magnetic poles reversing?'' Barton says. ''Ten degrees away from the geographical poles isn't that unusual. And while the south magnetic pole is moving northwards, so is the north magnetic pole. They are not converging. 'The weakening of the magnetic field is also spurious, because 2000 years ago the Earth's magnetic fields reached an extraordinary high value - 12 units. It has now relaxed to eight units, but the average value recorded [in the geological record] is four units.'' So we are safe? At least until 2012. ;-) "

- http://www.sott.net/

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