Of course, most of you know that a GPS can stop working if the batteries fail, or if the device loses communication with the satellite(s) that it receives its information from, but a compass should always work without fail right?
Very few people, if you asked them, would be aware that the Earth’s magnetic field reverses itself every several thousands of years — or that partial reversals happen with even greater frequency…
… When this reversal takes place, not even a standard mechanical compass would be able to determine true north. In fact, the compass would reverse — telling you that south is north and vice-verse. GPS’s, satellites, and most all other electronics could easily be damaged due to the protective properties that the magnetic field affords us (further explained below.)
Other concerns related to a full or partial magnetic field reversal
This magnetic field acts as a protective shield, circulating a magnetic field between the north and south pole, which protects the Earth from radioactive energy streaks from outer space; much of which emanates from the sun…
… This means higher radiation levels overall on the entire planet; possibly leaving the world less-inhabitable than it is when the field is normal.
The last full reversal of the Earth’s magnetic core happened 780,000 years ago, and lasted for 3-5000 years before returning to normal. Partial reversals, which are also called “Laschamp events” happen with even greater frequency and are even more unpredictable. A Laschamp event (name after the place in France where the phenomenon was discovered back in the 60′s) can happen anytime, and would make our delicate “electronic society” vulnerable to the radiation effects mentioned earlier.
The last Laschamp event happened approximately 40,000 years ago (soon after humans first inhabited Europe) and only took 450 years to complete a full reversal. This incident was confirmed by samples taken from core samples in the Black Sea, along with samples from the North Atlantic and South Pacific oceans.
Magnetic fields created by “roiling”
The magnetic fields on our planet are created by the turbulent, swirling movement of the earth’s outer liquid core (referred to as “roiling”) and the process is as of yet, an unpredictable process for the scientific community to unravel. Furthermore, scientists don’t really know the widespread, long-term effects of such an event on civilization or the ecosystem, making this another variable that can effect the future of mankind.
Original Source: http://www.space.com/18202-earth-magnetic-field-reversal.html