The Last Word has been discussing how and when Earth鈥檚 magnetic field flips. I know the odds are huge of such a flip in my lifetime, but what would happen to an aircraft in flight if north and south swapped ends?
鈥� If Earth鈥檚 magnetic field flipped while you were flying in an aircraft, you wouldn鈥檛 notice anything unusual, for two very good reasons.
First of all, commercial planes don鈥檛 use magnetic compasses for navigation. Instead, they use GPS for positioning and guidance, which is so accurate that an aircraft can land without pilot intervention. Even before the arrival of GPS, inertial navigation systems were used, which determine the path of an aircraft by measuring its acceleration along multiple axes, and computing its position from that.
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The second reason why you won鈥檛 notice anything is that the magnetic field doesn鈥檛 flip immediately. Instead, it slowly changes over a period of 1000 years or more. The magnetic poles are always moving around; usually they move very slowly, whereas during a reversal they just drift further and faster than usual, until eventually they settle in a reversed polarity.
Studies of old lava flows have shown that the magnetic field can drift as much as 6 degrees per day during a reversal period. However, even this extreme case would amount to only 3 degrees over a 12-hour flight.
As for aircraft communications, Earth鈥檚 magnetic field has very little effect on that too. It is possible that, as the poles drift, a plane might find itself under an aurora in an unusual location away from the poles. Even then, because the drift is slow and because satellites check for the solar storms that cause auroras, the pilot would almost certainly have advance warning.
Herman D鈥橦ondt, Newtown, New South Wales, Australia
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This article appeared in print under the headline 鈥淚n-flight entertainment鈥�