Earth's Magnetic Field Magnetism – not your ordinary common or garden horseshoe magnets – but the big one, the Earth’s magnetic field. You may not realise it, but when you dig out your boy scouts compass the needle doesn’t point to the true north pole – it points to the magnetic north pole. In case you’re wondering, that’s slightly to the left and down a bit on a standard Mercator’s projection map. Magnetic north tends to wonder around a bit, and the exact lines of magnetic force, especially around the coast of Africa are a little warped. Now, however, the US National Oceanic and Atmospheric Administration (NOAA), scientists at the agency’s National Centers for Environmental Information (NCEI) bureau have had to update their World Magnetic Model (WMM) almost a year early because the magnetic pole is moving faster than predicted. In fact the pole seems to be doing a runner from the northern wilds of Canada over to the equivalent bits of Siberia. In fact the pole is currently moving at a rate of 34 miles a year. Add to that, the anomalies off the coast of Africa also seem to be changing more than would be expected. In fact, it seems that something important might be might be happening. The question is, what? Well, we don’t really know. What we do know is that, periodically, the magnetic north and south poles swap over. This is called a geomagnetic reversal, and, as far as we can tell, it’s occurred 183 times in the last 83 million years. The last time it happened was some 780 thousand years ago. The reversals are, apparently, statistically random, so predicting them is simply not possible. It may well be that we are due, perhaps even overdue, for another one soon... If that happens, no one is sure what its effects on the biosphere will be. But it is worrying, because we know that the Earth’s magnetic field protects us from all sorts of space born radiation hazards. We don’t even really know whether the reversal just snaps across, or whether the field weakens over an extended period until the reversal is complete. And, of course, it may not happen at all – no one really knows. Oh and by the way, new evidence suggests that humans can sense Earth’s magnetic field, so if there is a reversal, it probably won’t just be migrating birds that get confused... https://www.sciencealert.com/shifts-in-the-magnetic-field-force-changes-to-an-important-global-navigation-model-a-year-early
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