The earth has been going through cycles of pole reversal once every 200,000 to 300,000 years. Sometimes, the attempt to switch poles fails and the poles return to their positions. One such failed attempt happened a few hundred thousand years ago. The last time the earth switched poles was around 780,000 years ago. That means that a pole reversal might be on our way soon.
Scientists are calculating using satellite data to figure out if a reversal is on its way for sure. If it is, it would mean trouble for humanity. When the poles switch, the magnetic field would decrease to one-tenth its original strength. The process of reversal may take many years to complete. The decreased field strength may lead to satellite failures, GPS failing and power shortages. However, experts believe that by the time such a reversal takes place, we would be ready.
Image courtesy: NASA Goddard
School of Science 