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  • In 1600, William Gilbert published a paper detailing how Earth behaves as a giant magnet.

  • That seems like a long time ago, but in geologic time, that's nothing.

  • It's taken hundreds of years to understand how Earth's magnetic field worksbut now

  • that we do, scientists are trying to find hints from Earth's history that might reveal

  • the future of this ever-changing invisible field all around us.

  • Specifically, archaeologists are studying the handles of ancient pottery.

  • Yeah.

  • But before I can explain it, we have to get to how the field affects you.

  • Scientists believe Earth's magnetic field is generated by the spinning of the Earth's

  • core.

  • Our planet's magnetic field is super important, as it blocks harmful rays emanating out of

  • the sun from hitting us on the ground, destroying the possibility of life as we know it.

  • No big deal.

  • It's always around us, and it strengthens and weakens over time -- sometimes, it even

  • flips.

  • If it were to flip, the magnetic north pole would become the south, and suddenly all magnetic

  • compasses in the world would be backwards.

  • Everything else would be fine though.

  • It's not like it would turn off and back on.

  • NASA knows a magnetic field flip happens about every two to three hundred-thousand years.

  • We know the magnetic field has flipped, because there's evidence in the geologic record.

  • Scientists pulled lava from the Mid-Atlantic Ridge, where two tectonic plates meet.

  • The ridge is spreading, giving easy access to very old, cooled lava flows.

  • Minerals embedded in the lava are sensitive to Earth's magnetic field as the lava cools,

  • so, by collecting samples of lava, calledcores,” and analyzing the rock...

  • I think you see where this is going

  • It reveals a record of Earth's magnetic field over hundreds of thousands of years.

  • This shows the lastmajor field flip was about 780,000 years ago.”

  • The problem is, cooling lava rock can't be precisely dated...

  • Lava rocks don't have timecodes or calendar reminders detailing when they oozed and then

  • cooled.

  • Geologic timescales can encompass thousands of years at a time, meaning we know this lava

  • cooled within a few millennia of whatever

  • So, while these rocks can give us an ancient picture of the magnetic field, imagine a pictures

  • that is really zoomed out, or blurry!

  • We definitely would need a better image to fully understand whats happening.

  • Now, a paper published in the Proceedings of the National Academy of Sciences in February

  • 2017, found a way to enhance this hypothetical image by using ancient pottery.

  • Clay is also subject to the same Earth's magnetic field record keeping, but the dates

  • are far more precise.

  • So, by analyzing the clay in 67 jar handles from the Iron Age kingdom of Judah, archaeologists

  • have found evidence of the magnetic field strength rising and falling over the 600 years

  • preceding 200 BCE!

  • All from jar handles made of clay!

  • The results were so clear, they could map the field picture down to a span of give or

  • take 15 years.

  • Imagine how much clearer a 15 year picture is compared to a 1000 year picture from geologic

  • time!

  • It looks like Earth's magnetic field strength was super high in the 8th century BCE, then

  • weakened from the 6th to 2nd century BCE.

  • The kicker for making this picture so clear, was the precise dating on the jar handle because

  • of royal stamps present on the handles of these 67 jars.

  • . Similar to how writing technology has gotten better since the Sumerians in 3000 BCE; over

  • time, stamp technology has changedallowing the archaeologists to give atmospheric and

  • cosmological scientists a leg up in studying magnetic fields by precisely dating when things

  • changed, and of, by proxy, giving physicists studying the interior movement of the Earth

  • a little bit of help too.

  • A magnetic field flip is coming!

  • Exact magnetic north has moved more than 600 miles further north since it was first pegged

  • in the early 19th century, first at about 10 miles per year , and now closer to 40 miles

  • per year!

  • On top of that, the field has lost “10 percent of its strength over the last two centuries

  • This causes more vibrant aurora, but don't fret.

  • The field continues to shield the surface of the planet from harmful charged particles,

  • and has the thick atmosphere to catch any that may eek through.

  • Long story short, go take a pottery class.

  • You might help scientists thousands of years in the future!

  • We can't do episodes like this without our sponsors.

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  • home or work.

  • When the magnetic field flip does happen.

  • Earth's magnetic north will become magnetic south, and all the compasses in the world,

  • and any technology based on that, would be backwards!

  • You want to know more about our magnetic field reversals?

  • Tara's got you, right here.

  • Got a science question?

  • Let us know down in the comments and please subscribe so you get more videos from us.

  • Thanks for watching!

In 1600, William Gilbert published a paper detailing how Earth behaves as a giant magnet.

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B2 中高級 美國腔

地球的磁场将要翻转,这就是我们所知道的(Earth's Magnetic Field Is Going To Flip, Here's How We Know)

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    joey joey 發佈於 2021 年 04 月 28 日
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