Did you know that the Earth's magnetic field reverses itself periodically, so compasses that point North today will one day point to the South?
An artist's rendition of the Earth's magnetic field being affected by the Sun (click for image)

The Earth's magnetic poles are distinct from its spin poles which are more familiar to us from globes and other maps. A magnetized bit of iron, such as a compass needle, orients itself to point toward magnetic north, not true north. The north magnetic pole currently lies off the northern coast of Canada, but it is moving rapidly, at about 10 km/yr, toward Siberia. These changes may be indicative of am impending "pole flip" in which, roughly every 300,000 years, the Earth's magnetic field reverses itself. After a reverse, a compass needle would point south instead of north. By looking at how natural magnets like iron orient themselves in volcanic rocks that cooled at different times, we can determine when pole flips actually occurred. The last one was about 750,000 years ago, meaning that we are overdue for another. For more on Earth's shifting magnetic field click here.

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