What are the chances that the magnetic poles of earth will switch during the next decade?

  • If the event were to occur, what would be the effect to our civilization?
  • Would computer hard drives get erased by the magnetic force?
  • Would our navigation systems collapse because they can't handle a different pole configuration in a similar way as how the millennium bug might have caused problem if companies wouldn't have prepared for it?
  • They had to move a runway in Florida because of moving poles: news.yahoo.com/s/yblog_thelookout/20110107/sc_yblog_thelookout/… – Michael Pryor Mar 7 '11 at 20:47
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    @Michael: The runway wasn't moved, it was renumbered. From the Fox article, "The busiest runway at Tampa International will be re-designated 19R/1L on aviation charts. It had been 18R/36L". – Dave C Mar 13 '11 at 11:47
  • What if you spun a hard disk around right now... would it get erased? – Mateen Ulhaq May 7 '11 at 20:23

No, nothing would get erased, the magnetic forces are very weak, and pole reversals are slow affairs. It won't just flip from one second to the other, instead there is a period where there are no poles or very weak poles (or possibly many poles), that lasts for thousands of years.

The things we know will happen is that:

  • Compasses stops working. As the magnetic field weakens we and our electronic toys like GPS's etc need to stop relying on a compass to know the heading. This is not a big problem, most car GPS's already have no compass as the cars magnetism makes them useless anyway, as an example.

Then there are things that may happen:

  • With a weak or no magnetic field we might get a lot more particles and radiation from the sun. Extinctions have not been correlated with reversals, so they don't seem to be dangerous for life, but this could prove problematic for electronics, meaning we need to shield them better.

  • Birds that navigate with the help of the magnetic field may become confused. But they navigate with the help of other things as well, so they'll probably just compensate.

That's pretty much it, really.

In any case, it's highly unlikely to happen within the nearest couple of thousand years, so not our problem, really. :-)

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    Unless you are an highlander, which I am. ;) – Stefano Borini Mar 9 '11 at 1:00

Though magnetic reversal occurres fairly chaotically, chances are very, very slim.

Besides, the effects of such a reversal have been totally over-hyped. Should we experience geomagnetic reversal in our lifetimes (which we probably won’t), it is unlikely that we’ll be cooked alive by the Solar Wind, or be wiped out by cosmic rays. It is unlikely that we’ll suffer any mass extinction event (after all, early man, homo erectus, lived through the last geomagnetic shift, apparently with ease). We’ll most likely experience aurorae at all latitudes whilst the dipolar magnetic field settles down to its new, reversed state, and there might be a small increase in energetic particles from space (remember, just because the magnetosphere is weakened, doesn’t mean we wont have magnetic protection), but we’ll still be (largely) protected by our thick atmosphere. Good article by Ian O'Neill.


Pole reversals don't happen very often! They usually aggregate to a handful per million years. If we estimate the events to occur once every 200 000 years, say then the risk of that happening within the next decade is 0,005%.

Note that the last reversal was 780 000 years ago, so 200 000 years is an optimistic estimate.

As for the "what would happen if..."-part of your question, I find it too hypothetical for this forum. From the FAQ:

You should only ask practical, answerable questions based on actual problems that you face. … avoid asking subjective questions where …

  • we are being asked an open-ended, hypothetical question: “What if ______ happened?”

I don't find that part of the question appropriate for this site, and I think your comparison to the millenium bug is telling: it was more of a media craze than an actual concern; those of us who worked in IT at the time thought nothing of it.

  • Scenario planning is practical. It's a lot more practical then "Does the theory of Intelligent Design make any observable predictions?". – Christian Mar 7 '11 at 15:06
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    @Christian: I don't know what the ID question has to do with any of this. My answer was with regards to the question about pole reversal. I answered (roughly) the part about probability, the other part I didn't feel belonged here, not because it was out of scope, but because it was too open-ended and hypothetical. – David Hedlund Mar 7 '11 at 15:43
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    The point is that a lot of question on this website have no practical use. On Stackoverflow they would therefore be off topic because they lead to discussions. The FAQ of this website is simply a copy of the Stackoverflow FAQ and it doesn't make sense to apply this rule the same way for the questions on this site. – Christian Mar 7 '11 at 15:53

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