Which Way Does Your Compass Point?
Over four billion years ago, Mars had an atmosphere. It was a living planet with water and possibly even some manner of life. However, four billion years ago Mars lost its magnetosphere, the electromagnetic field that protects the planet from solar wind and other cosmic radiations. Without that electromagnetic field the planet slowly died. Now four billion years later the lush and thriving planet Earth is witnessing a drastic decrease in the strength of its own magnetosphere. According to some scientists it has dropped as much as 10% over the last 300 years. Is Earth beginning to die?
The short emphatic answer is "NO." Although, some researchers do not deny that difficult changes are ahead for the next several hundred years as the magnetic poles of the planet perform a routine reversal that is long overdue. They are in resounding agreement that the world is not coming to an end. To understand what all this means and how it will effect the human race, it is important to first understand what all these terms mean. All the answers begin within the core of the Earth. The hot molten Iron core, to be precise.
An Electromagnet is quite simply a magnet created by the flow of an electrical current around a metal core. One can easily create a very simplistic electromagnet by wrapping a nail with thin-coated copper wire and connecting the ends of the wire to a standard D size battery. Voila--an electromagnet. On a global scale think of the earth's hot, molten Iron core as the nail, and visualize invisible wires of free-flowing electrons surging through the center of the Earth, in through the North pole and out through the South. The Earth is the electromagnet. The magnetic energy created extends outward for thousands of miles into space, and that magnetic energy is the Magnetosphere of the Earth. This inward flow at the North is what causes a permanent magnet (like the one in your compass) to point North.
The direction a compass points is called "Magnetic North" and does not align perfectly with "True North," which is denoted by the 'North Star' and also differs from "Grid North," the North marked on global maps. In fact, Magnetic North is not stationary at all and differs as much as 3 degrees every hundred years. Until, that is, the poles reverse and the electric current flows in at the South pole and out through the North, which would then cause a compass to point South. It would seem, by the compass reading, that the Earth had flipped on its head--but that is not the case. Only the electrical flow has reversed and this, scientists found has happened throughout the Earth's history approximately every 250,000 years.
The last time the Earth's Magnetic core reversed the flow was over 750,000 years ago. How do they know this? According to the NOVA Special "Magnetic Storm", scientists have been using Hawaii for decades to study the Earth's core and it's Electromagnetic Field. Hawaii's perpetual volcanic flow is a 5.5million year record of the Earth's Electromagnetic field. The lava from the core contains particles called Magnetite which, as the lava cools, align themselves with 'Magnetic North.' By examining layers of lava, which date back hundreds of years, they have learned just how dramatically "Magnetic North" has changed over time. It was learned that the weakest records of the electromagnetic field always preceded one of the Magnetic Pole Reversals, a decline of as much as 80-90%. The Earth's current field is in decline of only 10% but continuing to drop at an increasing rate. So the evidence would suggest that as our Electromagnetic field continually decreases, that the Earth is preparing to make just such a reversal.
NOVA's one hour special is filled with information but is rather sensationalized with a threat of apocalypse that they only then dismiss as rubbish and disprove. Segueing between scientists and sources with an awful soundtrack, it's nearly unbearable to watch unless the science itself holds ones interest. If the depth of intrigue is no more than a few factoids to share, then the all too brief documentary may suffice. Others with a more piqued curiosity may want to do as I have done, and delve into the dozens of websites and books on the subject, including NASA's own. There is far more to be learned about this fascinating phenomena without melodramatic threats or tongue-in-cheek quips about a world-wide aurora display being the human races' compensation for mass-increases in cancer deaths. The director might as well have ended with a dramatic refrain. The most strenuous moments of a Magnetic Pole Reversal would not affect the planet until many generations from now, and as one scientist proudly remarked, "by then we'll know how to handle it."