The direction of north and south we take for granted, but magnetic north and south have switched places in the past and may do so again in the near future.
The Earth's magnetosphere is what generates the Earth's magnetic poles. It also protects us from harmful solar wind emanating from the Sun and radiation from outside our solar system. It sheathes the Earth and extends outside the atmosphere. This is why missions to the moon and other planets are plagued by radiation but orbiting missions less so.
Origin of the Magnetosphere
At the center of the Earth is a core of iron and other heavy metals. Iron is a magnetic metal and this is what produces the magnetosphere. The Earth is unusual to have so much iron at it's core. It is now widely believed from the findings of the Apollo missions that this a result from a collision with another object during the Earth's formation. A majority of heavier elements combined from both objects to make the Earth, and a lot of the lighter elements combined to make the Moon.
The Dynamic Magnetic Field
The magnetosphere is not quite a perfect sphere. It's more like an apple, with the poles where the stem of an apple is. It constantly changes shape and strength, and different patches can favor different magnetic directions. The magnetic field varies and shifts on a small scale. If the field is chaotic enough it is believed that a geomagnetic reversal may occur.
History of Geomagnetic Reversal
Scientists know that reversals have occurred many times in the past. The direction of magnetic grains laid down successively in the Earth's crust, particularly the sea floor are a primary piece of evidence. When the rock is new and molten the grains are free to align themselves with the prevailing magnetic field. As the rock cools, the grains are frozen in time. As the sea floor expands outward (in the Atlantic), it is regularly striped with rock oriented in different directions. This indicates that the magnetic poles have reversed many times throughout the Earth's history.
Current Reversal?
Currently the magnetic field is experiencing a period of weakening. This may be a precursor to a reversal (and we are overdue for one). If a reversal does occur, it won't happen overnight but gradually over months or years. It is unlikely that there will be any dire or drastic side effects. There may be a slight rise in the per capita cancer rate due to a weaker magnetic field. We may also be able to see the northern lights at lower latitudes, and if you own a compass, it will have difficulty finding north until the magnetosphere settles.
