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Earth Once Had Many Magnetic Poles

While humans have been trying to find their way around and then find their way back for eons, the simple navigational aid known as the compass wasn’t invented by the Chinese until around 200 BC. What took so long? Did it have anything to do with the fact that Earth once had multiple magnetic poles that would have driven compasses, sailors and nomads crazy?

It actually happened a lot earlier that 200 BC, according to Peter Driscoll, a researcher at the Carnegie Institution of Science and author of a new study in the journal Geophysical Research Letters. While studying geothermal records going back 4.5 billion years, he noticed massive fluctuations in magnetic field directions and numbers beginning around 650 million years ago. The cause of these fluctuations required a change in thinking.

An illustration by Peter Driscoll of ancient Earth's multiple magnetic field compared to today's two-pole status.

An illustration by Peter Driscoll of ancient Earth’s multiple magnetic field compared to today’s two-pole status.

The north and south poles are where they are because of the Earth’s molten iron core rotating around a solid inner core. Laboratory models and simulations of this have been consistent in showing a “stable dipole field” – two poles at either end. So what caused what looks like multiple poles 650 million years ago?

Driscoll speculated that this might be when the Earth’s core went from completely liquid to having a solid inner core. Feeding that idea into existing models and into new 3-D dynamo simulations, which model the generation of magnetic fields by strong fluid motions, Driscoll found that Earth had two poles a billion years ago, went to multiple poles around 600 million years ago and then back to the current two poles some time after that.

An illustration of a Snowball Earth

An illustration of a Snowball Earth

While having two poles to control our compasses is nice (at least when you can’t get a GPS signal), the real benefit of Earth’s magnetic field is protecting the planet from cosmic radiation. If the multiple-pole theory holds true, it could explain severe climate fluctuations during the Neoproterozoic Era when the so-called Snowball Earth period – a near-frozen era of global glaciations – is believed to have taken place.

Multiple poles means weak magnetic fields to repel cosmic radiation

Multiple poles means magnetic fields too weak to repel cosmic radiation

It looks like you should continue to use your GPS to keep from getting lost but keep a compass around to warn of glaciers, magnetic field fluctuations and more.

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Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.
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