The north and south poles might flip in the next 1000 years

http://www.observer.co.uk/international/story/0,6903,837058,00.html
<font size=5>Sun's rays to roast Earth as poles flip </font>

Robin McKie, science editor
Sunday November 10, 2002
The Observer

Earth's magnetic field - the force that protects us from deadly radiation bursts from outer space - is weakening dramatically.
Scientists have discovered that its strength has dropped precipitously over the past two centuries and could disappear over the next 1,000 years.

The effects could be catastrophic. Powerful radiation bursts, which normally never touch the atmosphere, would heat up its upper layers, triggering climatic disruption. Navigation and communication satellites, Earth's eyes and ears, would be destroyed and migrating animals left unable to navigate.

'Earth's magnetic field has disappeared many times before - as a prelude to our magnetic poles flipping over, when north becomes south and vice versa,' said Dr Alan Thomson of the British Geological Survey in Edinburgh.

'Reversals happen every 250,000 years or so, and as there has not been one for almost a million years, we are due one soon.'

For more than 100 years, scientists have noted the strength of Earth's magnetic field has been declining, but have disagreed about interpretations. Some said its drop was a precursor to reversal, others argued it merely indicated some temporary variation in field strength has been occurring.

But now Gauthier Hulot of the Paris Geophysical Institute has discovered Earth's magnetic field seems to be disappearing most alarmingly near the poles, a clear sign that a flip may soon take place.

Using satellite measurements of field variations over the past 20 years, Hulot plotted the currents of molten iron that generate Earth's magnetism deep underground and spotted huge whorls near the poles.

Hulot believes these vortices rotate in a direction that reinforces a reverse magnetic field, and as they grow and proliferate these eddies will weaken the dominant field: the first steps toward a new polarity, he says.

And as Scientific American reports this week, this interpretation has now been backed up by computer simulation studies.

How long a reversal might last is a matter of scientific controversy, however. Records of past events, embedded in iron minerals in ancient lava beds, show some can last for thousands of years - during which time the planet will have been exposed to batterings from solar radiation. On the other hand, other researchers say some flips may have lasted only a few weeks.

Exactly what will happen when Earth's magnetic field disappears prior to its re-emergence in a reversed orientation is also difficult to assess. Compasses would point to the wrong pole - a minor inconvenience. More importantly, low-orbiting satellites would be exposed to electromagnetic batterings, wrecking them.

In addition, many species of migrating animals and birds - from swallows to wildebeests - rely on innate abilities to track Earth's magnetic field. Their fates are impossible to gauge.

As to humans, our greatest risk would come from intense solar radiation bursts. Normally these are contained by the planet's magnetic field in space. However, if it disappears, particle storms will start to batter the atmosphere.

'These solar particles can have profound effects,' said Dr Paul Murdin, of the Institute of Astronomy, Cambridge. 'On Mars, when its magnetic field failed permanently billions of years ago, it led to its atmosphere being boiled off. On Earth, it will heat up the upper atmosphere and send ripples round the world with enormous, unpredictable effects on the climate.'

It is unlikely that humans could do much. Burrowing thousands of miles into solid rock to set things right would stretch the technological prowess of our descendants to bursting point, though such limitations do not worry film scriptwriters. Paramount's latest sci-fi thriller, The Core - directed by Englishman Jon Amiel, and starring Hilary Swank and Aaron Eckhart - depicts a world beset by just such a polar reversal, with radiation sweeping the planet.

The solution, according to the film, to be released next year, involves scientists drilling into Earth's mantle to set off a nuclear blast that will halt the reversal.

Given that temperatures at such depths rival those of the Sun's surface, such a task would seem impossible - except, of course, in Hollywood.

Guardian Unlimited © Guardian Newspapers Limited 2002

 

The August issue of Discover had a very interesting article about that.

Nuclear Planet
Is there a five-mile-wide ball of hellaciously hot uranium seething at the center of the Earth?

What is Earth? Poets say it's a celestial sapphire, a cerulean orb. Astronomers say it's a medium-size planet orbiting an average star. Some environmentalists say it's Mother. Biologists say it's life's only known home. But the most scientifically precise definition may prove to be the one that no one suspected. Earth, says geophysicist J. Marvin Herndon, is a gigantic natural nuclear power plant. We live on its thick shield, while 4,000 miles below our feet a five-mile-wide ball of uranium burns, churns, and reacts, creating the planet's magnetic field as well as the heat that powers volcanoes and continental-plate movements. Herndon's theory boldly contradicts the view that has dominated geophysics since the 1940s: that Earth's inner core is a huge ball of partially crystallized iron and nickel, slowly cooling and growing as it surrenders heat into a fluid core. Radioactivity, in this model, is just a supplementary heat source, with widely dispersed isotopes decaying on their own, not concentrated.
If Herndon's theory is true, it would be the biggest news in geophysics in decades. "I would rank it right up there with plate tectonics as one of the truly great discoveries," says Hatten Yoder, director emeritus of the Geophysical Laboratory of the Carnegie Institution of Washington. The idea also has immediate implications for human beings and all other living things on Earth. While it leaves open the question of whether nuclear fission is a sensible way to make power, it does at least mean that fission is a natural, even essential process. "We owe our very lives to it," Herndon says. That subterranean nuclear reaction, he says, is the dynamo that powers Earth's magnetic field, which protects us from the ravages of the sun.
"Solar radiation would have stripped off our atmosphere long ago without the repulsion provided by the field," says nuclear engineer Daniel Hollenbach, Herndon's collaborator at the Oak Ridge National Laboratory. "We absolutely depend on it."
Herndon recently put forth what he sees as the most compelling argument for his theory in a paper published in the Proceedings of the National Academy of Sciences. Using computer simulations that Hollenbach helped him run at Oak Ridge, Herndon showed how software that tracks fuel usage at nuclear power plants indicates that a "planetary-scale geo-reactor" could indeed have been blazing away for 4.5 billion years, the widely accepted estimate of Earth's age, at heat levels that match Earth's actual output of roughly four terawatts. Moreover, such a reactor would vary in intensity— sometimes strong, sometimes weak, sometimes shutting down altogether— which could explain why Earth's magnetic field has periodically waxed, waned, and reversed through the millennia.

The rest of the 6 page article is here: http://www.discover.com/aug_02/featplanet.html