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 works… but 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, called
“cores,” 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 last “major 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 changed… allowing
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!
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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!
