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  • The Earth's magnetic north pole is shifting, and I mean that in two ways.

  • One, it's literally moving away from Canada and towards Siberia, and two, it's accelerating.

  • It's moving so fast now we've had to update our models of Earth's magnetic field ahead of schedule.

  • Why our magnetic poles move and flip has always been something of a mystery,

  • but now a team of researchers from Leeds University believe they've found the culprit: blobs.

  • Since the magnetic north pole was discovered in the 1830s, it's been moving.

  • Slowly at first, notching a top speed of at most 15 kilometers per year.

  • But since the 1990s that pace has picked up, and now it trucks across the arctic anywhere

  • from 50 to 60 kilometers per year.

  • I should mention that things can get a little confusing when we start to talk aboutnorth poles.”

  • The earth actually has several, depending on your definition.

  • There's the geographic north pole, where all lines of longitude we've drawn on

  • a globe converge.

  • The magnetic north poles don't align with the geographic north pole.

  • And yes I saidpoles,” because it turns out there are multiple magnetic north poles.

  • You've probably seen earth's magnetic field likened to a giant bar magnet in your

  • textbooks, with one north and one south pole, what's known as a dipole.

  • From a zoomed out view, like say in space, the earth's magnetic field appears to look

  • and act like a dipole, and the spot that best represents the northern dipole is off the

  • coast of Greenland.

  • However, on a finer scale the earth's magnetic field is more varied and complex than a giant

  • bar magnet, and there is a point where the earth's magnetic field is perpendicular

  • to Earth's surface.

  • If you were to stand over it with a compass, the needle would try and point straight down,

  • so it's called the dip pole.

  • So to recap there is a geomagnetic north dipole and a magnetic north dip pole and they are

  • different things that are in different places.

  • Got it?

  • Great, moving on.

  • Anyway the dip pole is the one that's on the move, and we think it's because of the

  • movement of the liquid iron in earth's outer core.

  • A few years ago, the researchers from Leeds suggested that jet streams of molten iron

  • were the culprit, but the idea was scrapped because the jets started accelerating years

  • after the pole's movement did.

  • So the scientists have turned their attention farther south to find the source of the movement.

  • The team from Leeds used 20 years of data collected by satellites, including European Space Agency's Swarm,

  • a trio in polar orbits that measure the strength and direction of earth's magnetic field.

  • They concluded that changes in flow at lower latitudes in the outer core have changed the

  • magnetic flux, or the number of field lines, in two blobby areas.

  • These blobs of magnetic flux are located underneath Canada and Siberia.

  • While Canada's blob has gotten weaker, Siberia's has gotten stronger.

  • This means Russia is winning the magnetic tug-of-war, and based on the team's models

  • it will continue to do so for at least a few more decades.

  • But the balance is fairly delicate, so a small change in the field could send the dip pole

  • back Canada's way.

  • Wherever it goes, it's important we keep tabs on it because its position is used to

  • update the World Magnetic Model, something used by all navigation systems that rely on

  • the geomagnetic field.

  • The World Magnetic Model is necessary to correct for local compass errors, and is used by the

  • U.S. Department of Defense, the U.K.'s Ministry of Defence, NATO, and even average everyday

  • smartphone users like you and me.

  • We update the model every 5 years, and actually updated it ahead of schedule because the dip

  • pole is dipping out so fast.

  • Still, the next time I'm late for something because my GPS took me on a weird route, I'm

  • going to blame the blobs and hope my boss buys it.

  • As if the whole multiple north poles bit weren't confusing enough, the magnetic north dip pole

  • is technically a magnetic south pole.

  • Think about it, why else would it attract the north pole of your compass?

  • To learn more about what's happening inside Earth's core and why our magnetic fields

  • are moving, check out Maren's video here.

  • Make sure to subscribe to Seeker to stay up to date on your magnetic field news.

  • Thanks for watching and I'll see you next time.

The Earth's magnetic north pole is shifting, and I mean that in two ways.


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B2 中上級

地球の磁北が動き続ける理由がついに判明 (We May Finally Know Why Earth’s Magnetic North Keeps Moving)

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    Summer に公開 2021 年 01 月 14 日