The Earth's magnetic field is weakening, and has been for some time, which could indicate an impending reversal of the north and south magnetic poles. In any event, its strength is currently about average compared to the last few million years. It is true that some scientists believe the Earth is overdue for a geomagnetic reversal, because the last reversal, the Brunhes-Matuyama reversal, was 780,000 years ago. While reversals have occurred at varying times from several hundred to millions of years apart, it seems that on average they occur about every 400,000 years. However, most opinion suggests that a geomagnetic reversal takes an extended period, and does not just flip over. There are some computer models that suggest a fast flip could occur, but this seems not supported by observations of the earlier reversals. The present rate of weakening suggests a reversal could start in one to two thousand years time. There have been tens of thousands of these reversals in the Earth's history, and none has been linked with any extinction events. Certainly Homo Erectus and their forebears survived many reversals, so it is likely that the solar wind induces a magnetic field in the ionosphere to shield the Earth from damaging particles until the magnetic field is restored. OK; compasses will point the "wrong" way, but then magnetic north has been moving away from northern Canada towards Siberia for some time, currently at 40+km/year. Some "believers" suggest that a geomagnetic reversal, to which they often refer incorrectly as a polar shift, could be triggered by a massive solar flare. There is absolutely no evidence linking solar flares to a geomagnetic reversal. In any event, it appears that the solar maximum will peak in 2013, not 2012, although it is expected to produce some quite strong magnetic storms. Remember that solar flare cycles occur at much, much shorter time scales than geomagnetic reversals. Some also try and link this reversal with the Earth suddenly starting to spin on its axis in the opposite direction! They suggest that the surface of the earth will somehow become detached from the lower regions and start floating around or some such nonsense. Some suggest that the Earth will tip over through 90º; but they do not have any idea why or how. I am not joking; they really believe this stuff. These are probably the most ridiculous ideas I have heard in the whole 2012 scenario, which is itself full of utter garbage! There is a really good debunking of this aspect of 2012 idiocy at Universe Today.