We have a number of ‘North Poles’ on Earth. Above shows the sign at the Geographic North Pole. The magnetic North Pole is what your compass points to when you are trying to navigate using it. That is different from the geographical North Pole, which is defined differently. You might think that both of those points are fixed, but in fact both can move! The Geographic North Pole’s specific definition is “the point at which the Earth’s axis of rotation meets the Earth’s surface.” It is also the point directly above which is the Pole Star, Polaris. This point may seem as fixed as possible, but over the past few thousands of years the Earth’s axis of rotation has wobbled. This means that 5000 years ago, Polaris wasn’t our pole star. While the Egyptians were building the pyramids, a star named Thuban was the one sitting directly above our North Pole (in fact, the air shafts in the pyramids that confused historians for years allow us to view this star).
And, in another few thousand years, we will have another new pole star, Alderamin, followed by Deneb by 9.800AD. The geographic north pole moves slowly and on a 26,000 year cycle, as the Earth’s axis of rotation precesses gradually.
So, not as fixed as you might think! But it only changes a little bit over a long timescale. The magnetic north pole is a bit more of a wanderer. The reason the Earth has a magnetic field in the first place is its molten core of iron. The iron moves around in the core of the Earth, flowing in a convection current as heat escapes from the centre of the Earth. You can imagine the Earth’s magnetic field as an enormous bar magnet sitting through the earth. Where it comes out the top of the earth is the magnetic north pole, and where it sits at the bottom is the magnetic South Pole. Confusingly, the magnet would have its south pole at our north pole, but if you think hard enough, this makes sense. When we use a compass, the north of the compass needle faces north. Since opposites attract, the northern magnetic pole of Earth would have to be the south pole of the hypothetical bar magnet passing through earth.
The magnetic field of the Earth is very important to life on Earth. It not only allows us to tell what direction we are going in (even animals use the field for navigation), it protects us from the worst of the solar weather. Solar wind or weather occurs when highly charged particles are ejected from the sun. If these were to come towards Earth without its magnetic field, they would strip away parts of our atmosphere, including the ozone layer. This would expose all life on earth to potentially lethal amounts of UV radiation which causes cancer in humans by changing our DNA and suppresses immune systems. It also causes cataracts in animals and damages plants’ ability to photosynthesise. Basically, really bad.
So that’s why our magnetic field is important. But, as we’ve mentioned, it can change. The magnetic poles of the earth are currently moving faster than at any point in human history (well, since 1831, which is when the magnetic north pole was discovered). The magnetic field has been wandering for the last 180 years, but it has accelerated over the last few decades, travelling through Northern Canada towards Russia. The upshot of all this is basically that anything that uses the magnetic field to navigate will be going awry. In the US, the Federal Aviation Administration have renamed a bunch of Runways at airports, which are named after the direction they point. Seeing as compasses have been thrown off by a number of degrees since 1980, air traffic control in every country will have to recalibrate. But humans aren’t the only ones affected by this (albeit small) change. Migratory animals, such as birds and turtles might not be able to adapt to this change, may end up going off course.
Now, this all sounds very dramatic, but it will apparently change very little about our everyday lives (human lives. The animals may still be stuck). Smart phones and GPSs will be fine, particularly at latitudes as low as ours. No, what is more worrying is the event it potentially foreshadows – the complete flipping of the poles.
While Earth’s magnetic field can wander, a complete pole reversal sounds unlikely. It is however, entirely possible, and even (in geological time) very common. It has happened loads of times through Earth’s History, averaging out at about one every 400,000 years. But it’s been a while since the last one… try 780,000 years. Scientists can study sediments, lava flows and even human made objects to detect when there were past changes in the magnetic field. The only blip recorded in the last 780,000 years was a short-lived reversal of the field 41,000 years ago. So a reversal is entirely overdue. It’s very easy to panic when you hear this, with some scientists predicting mass loss of electricity and burnout of satellites and radio communicators, not to mention continental shift, making natural disasters such as earthquakes and tsunamis the norm. Higher amounts of UV light might be recorded, causing major ecosystem changes and species extinctions (sound familiar? Looking at you, climate change) But this is all entirely hypothetical. In fact, many scientists say we should all relax! While reversals do happen, they are not as abrupt as you might think. It could take over 10,000 years for a complete reversal to happen, so we’ll have plenty of time to prepare and get adapted to the new circumstances, whatever they may be. Plus we’ll likely have plenty of warning, as researchers studying past pole reversals say that much higher rates of change of the position of the magnetic poles forewarn unusual events. The field may seem like its moving fast now, but in the past it has oved up to ten times as fast, usually preceding weakening of the field in regions. This predicts a change in the field, either a complete reversal or a temporary shift such as that 41,000 years ago. Aside from all that, continents remained pretty well stuck in place during the last few pole reversals. Someone just got too excited when making predictions.
So, no immediate need to worry; scientists are monitoring the magnetic field of the earth daily at this point and while it is moving, there is no immediate cause for concern. Besides, humanity’s heading for many more pressing calamities; they may decide our fate long before we need to worry about pole reversal!