Solar radiation constantly bombards Earth, and Earth’s magnetic field repels it. According to a new study, our planet’s protective shield might weaken far more quickly and unpredictably than scientists previously thought.
Like the invisible force shield around the Death Star, Earth's magnetic field surrounds and protects our planet from the hottest, most statically charged particles the sun can throw our way. This shield — the natural product of molten iron swirling around the planet's core — has had our backs for billions of years, and prevented Earth from becoming an irradiated, electrified wasteland. Every now and then, though, that shield lets down its guard.
A few times every million years or so, Earth's magnetic field reverses polarity. Imagine a giant bar magnet inside our planet got flipped upside down; iron molecules in Earth's outer core would switch direction, the magnetic North Pole would become the magnetic South Pole, and the invisible currents of energy that make up our planet's magnetic armor would tangle and break, potentially reducing the shield's protective strength by up to 90 percent, previous studied have suggested. [6 Visions of Earth's Core]
Luckily, full reversals are uncommon and unfold slowly over thousands of years. (The last full reversal occurred about 780,000 years ago.) But according to a new study published Monday (Aug. 20) in the journal Proceedings of the National Academy of Sciences, partial or temporary shifts in Earth's magnetic poles can occur much, much faster than was previously thought possible — potentially, within a single human lifetime.
n the new study, an international team of scientists analyzed 16,000 years of geomagnetic history coded into the atoms of an ancient stalagmite in China. This story written in stone told them that once, about 98,000 years ago, the planet's magnetic field suddenly flipped polarity in as little as 100 years — roughly 30 times faster than the generally expected rate, and 10 times faster than what was thought to be the fastest rate possible.
"The record provides important insights into ancient magnetic field behavior, which has turned out to vary much more rapidly than previously thought," study co-author Andrew Roberts, a professor of Earth sciences at Australian National University, said in a statement.