Monday, September 11, 2006

MPR - When your compass points South

For me - This is one of the most distracting scientific (PH) ever. And it may be that our planet is on the verge of it happening again! I'm no scientist though, so in this particular blogisode, I am going to input various segues about MPR and you can come up with your own assessments and contributions, by all means, comments are welcome! There will be updates on MPR added frequently - please stop back in to see if this blogisode has been updated.

First off - Its very important to state why it is our magnetic field and our magnetosphere are so important to our survival. You may be wondering what drives our magnetic poles, our magnetic field and our magnetosphere - let me take a minute using the PBS Nova Website to explain - This isn't my explanation, you can read it for yourself here

What Drives Earth's Magnetic Field?

When an electric current passes through a metal wire, a magnetic field forms around that wire (see diagram at right). Likewise, a wire passing through a magnetic field creates an electric current within the wire. This is the basic principle that allows electric motors and generators to operate.

In the Earth (see image below right), the liquid metal that makes up the outer core passes through a magnetic field, which causes an electric current to flow within the liquid metal. The electric current, in turn, creates its own magnetic field—one that is stronger than the field that created it in the first place. As liquid metal passes through the stronger field, more current flows, which increases the field still further. This self-sustaining loop is known as the geomagnetic dynamo.

Energy is needed to keep the dynamo running. This energy comes from the release of heat from the surface of the solid inner core. Although it may seem counterintuitive, material from the liquid outer core slowly "freezes" onto the inner core, releasing heat as it does so. (High pressures within the Earth cause material to freeze at high temperatures.) This heat drives convection cells within the liquid core, which keeps the liquid metal moving through the magnetic field.

The so-called Coriolis force also plays a role in sustaining the geomagnetic dynamo. Our planet's spinning motion causes the moving liquid metal to spiral, in a way similar to how it affects weather systems on the Earth's surface. These spiraling eddies allow separate magnetic fields to align (more or less) and combine forces. Without the effects caused by the spinning Earth, the magnetic fields generated within the liquid core would cancel one another out and result in no distinct north or south magnetic poles.


If all the compasses in the world started pointing south rather than north, many people might think something very strange, very unusual, and possibly very dangerous was going on. Doomsayers would have a field day proclaiming the end is nigh, while more rational persons might head straight to scientists for an explanation.

Fortunately, those scientists in the know—paleomagnetists, to be exact—would have a ready answer. Such reversals in the Earth's magnetic field, they'd tell you, are, roughly speaking, as common as ice ages. That is, they're terrifically infrequent by human standards, but in geologic terms they happen all the time. As the time line at right shows, hundreds of times in our planet's history the polarity of the magnetic shield ensheathing the globe has gone from "normal," our current orientation to the north, to "reversed," and back again.

The Earth is not alone in this fickleness: The sun's magnetic shield appears to reverse its polarity approximately every 11 years. Even our Milky Way galaxy is magnetized, and experts say it probably reverses its polarity as well. Moreover, while a severe weakening or disappearance of the magnetic field would lay us open to harmful radiation from the sun, there's little evidence to date that "flips" per se inflict any lasting damage (seeImpact on Animals).

It might sound as if scientists have all the answers regarding magnetic reversals. But actually they know very little about them. Basic questions haunt researchers: What physical processes within the Earth trigger reversals? Why do the durations and frequencies of both normal and reversed states seem random? Why is there such a disproportionately long normal period between about 121 and 83 million years ago? Why does the reversal rate, at least during the past 160 million years, appear to peak around 12 million years ago?

All these questions remain unanswered, though experts like Dennis Kent, the Rutgers University geologist who supplied NOVA with updated figures for the time line, are hard at work trying to answer them. In the meantime, not to worry. Reversals happen on average only about once every 250,000 years, and they take hundreds if not thousands of years to complete.

Even the weakening currently under way may be a false alarm. The field often gets very weak, then bounces back, never having flipped. As Ron Merrill, a magnetic-field specialist at the University of Washington remarked when asked whether we're in for a reversal: "Ask me in 10,000 years, I'll give you a better answer." So hang on to your compass. For the foreseeable future, it should work as advertised.—Peter Tyson

Quoted From - Earth Magnetic Field Reversal - by: by Mary-Sue Haliburton - Pure Energy Systems News

Seeing the powerful earthquakes such as the December 26th, 2004 event that triggered the tsunami disaster, people are looking for possible causes for the apparent instability of earth's crust. "End-times" alarmists and backyard researchers believe that the predicted imminent reversal of the earth's magnetic field may be a significant clue to these eschatological-scale events.

Scientists have been observing changes in the direction of earth's magnetic field which took place recently as well as in the distant past. NASA’s website features a map showing the gradual northward migration of the north magnetic pole in the past century and a half. Since more than double the time interval has elapsed since the last reversal, compared to the time lapse between the previous two pole reversals, some believe we may be overdue for the next north-south flip. (1,2) However, though the interval between reversals of the Earth’s magnetic field can be as short as 5,000 years, it can also be as long as 50 million years. There does not seem to be any logic or rule governing the planet’s behavior.

It is not only the direction but also the strength of this magnetic field that is a concern. In the time of dinosaurs, at an estimated 2.5 gauss, it was eighty percent stronger than it is now. This may have been one of the reasons such gigantic life forms thrived. It is now accepted that a catastrophic event ended the reign of giant reptiles. However, they did not re-evolve to equivalent dimensions. And the disappearance of mammalian “mega-fauna” in more recent times is still considered to be a mystery. The mastodons and mammoths would have towered over modern elephants. Why are there so few large terrestrial animals today?

To continue reading this articles please Click Here


Post a Comment

<< Home