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The great philosopher Theophrastus once said, “Time is the most valuable thing a man can
spend.”
Theophrastus, of course, was an idiot, and had forgotten about Kohl’s Cash.
You try buying khakis with time and see how it goes.
But Kohl’s Cash has a problem: it’s dropping in value, because it’s only good for a certain
number of days, and since 2011, days have gotten shorter.
You see, back in 2011, LMFAO released the hit song “Party Rock Anthem,” which called
on everyone to party rock, to have a good time, and most importantly, to shake that.
Unfortunately, it turned out the earth loved “Party Rock Anthem” too, and when told
to shake that, took the instructions literally and caused an earthquake in Japan.
In addition to being the costliest natural disaster in history—the World Bank estimated
the damage at $235 billion—the 9.0 magnitude Tohoku earthquake also did a bunch of crazy
stuff to the earth: it cracked the sea floor, it broke icebergs and sped up glaciers 8,000
miles away in Antarctica, it reduced the gravity in Japan by thinning the earth’s crust,
and, finally, it even shortened the length of a day, something that usually only happens
once a year as part of a deep-state conspiracy to mess up my sleep schedule called “daylight
savings time.”
To understand how an earthquake managed to steal away your precious hours of shut-eye,
you first have to understand something called “The Moment of Inertia,” which sounds
like a Coldplay album from the late 2000s, but is actually a physics term for “the
torque needed for a desired angular acceleration about a rotational axis,” which is basically
fancy-talk for “how hard is it to make a round thingy go spin.”
When the earthquake quaked the earth and all, it redistributed mass closer to the earth’s
core, which decreased the earth’s moment of inertia.
To help illustrate, picture a figure skater pulling their arms close to their body to
speed up their rotation.
In the same way the figure skater spins faster when they pull their arms closer to their
body, the earth spins faster when an earthquake pulls mass closer to its center—of course,
this paragraph might have sounded similar to one 139 HAI episodes ago, but we’ll ignore
that.
As a result, days are now 1.8 microseconds shorter.
A microsecond, by the way, is one millionth of a second—for perspective, one microsecond
is how long it take for light to travel 300 meters.
For another perspective, one microsecond is how much time I spent trying to think of a
joke to put here before I gave up and moved on.
So 1.8 microseconds isn’t really that much, and actually, it’s natural for the length
of a day to vary—in a normal year, it can fluctuate as much as 0.34 milliseconds, mostly
due to changes in atmospheric winds.
While slight changes in the earth’ rotation speed are pretty common, the 2011 earthquake
had another, more unusual consequence: it shifted the earth’s axis.
To understand how it did that, we have to talk about a bunch of space and physics and
geophysics stuff, which is going to be confusing enough on it’s own, so for now we’re going
to take all the jokes and put them in a little box that we’ll keep in the corner of the
screen, and once we’re done explaining, we’ll open it.
Okay, so, the earth rotates around what’s called a rotation axis, which is an imaginary
line that runs through the north and south pole.
If you picture spinning a globe, the little rod it spins around is the rotation axis,
and the earthquake didn’t change that—the rotation axis can only be shifted by something
in space, like the moon or the sun or whatever.
But the Earth isn’t balanced along the rotation axis; it’s balanced along something called
the figure axis, which is an imaginary line that’s usually located about 10 meters from
the north-south rotation axis.
In theory, if the earth were a perfect sphere, the figure axis and the rotation axis would
be the same line, and the earth would spin smoothly, but the earth isn’t a perfect
sphere: there’s a bunch of stuff like glaciers and water sloshing around and changing atmospheric
pressure and also something called Ice Age Rebound, and the result of all those things
is that when the earth spins, it wobbles a little bit, and the earthquake seems to have
made that wobble worse, by moving the figure axis about six and a half inches further from
the rotation axis.
Okay now we’ll let out the jokes.
Let’s see what I missed.
Ice Age Rebound sounds like a Dreamworks movie, Drake meme about the axes, there’s a dance
called the wobble, could have worked that in, alright doesn’t seem like anything too
important, let’s keep going.
Now, you might be thinking “so what, the earth wobbles a little more now; who cares?”
Well first of all, I care; I made a whole video about it, so show some respect.
Second of all, this stock footage bear cares.
I paid for the stock footage so I get to decide what he cares about, and I’ve decided he
cares about earth wobbling.
And finally, the earth’s wobble matters a lot for NASA and other space agencies.
They have to account for the wobble when spacecraft plan their flight paths, because if they miscalculate
the earth’s rotation at launch, they could end up miles away from their intended destination.
But hey, if there’s one thing history has taught us, it’s that when explorers accidentally
end up in the wrong place, it turns out great for everyone involved.
Nobody ever gets enslaved, and the explorer who enslaved people definitely doesn’t get
a holiday named after them.
If you were enjoying a poorly-conceived holiday and needed something to watch, you might think,
“hey, I sure do wish all my favorite educational creators had gotten together to create a streaming
service where they’re able to make cool, fresh, and sometimes exclusive content without
worrying about demonetization or algorithms.”
Well guess what: your weirdly specific wish came true.
It’s called Nebula, and it’s got all our YouTube content, ad free and early, plus exclusive
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an incredible, backstabbing game show called Money, that I got to be part of.
The best way to get Nebula is through a bundle deal with CuriosityStream—the fantastic
documentary streaming service with thousands of great titles, including originals from
people like David Attenborough and Jane Goodall.
On there, you could even watch “Saving Tokyo,” which is about the massive infrastructure
projects they’re conducting to protect the city from earthquakes just like the one we
discussed.
Right now, for less than $15, you can get an entire year of CuriosityStream and Nebula
when you go to curiositystream.com/HAI, and you’ll be supporting the channel while you’re
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