00:00Doctor, I can't understand what's going on.
00:03I feel dizzy and, ugh, how do I say it, I'm tilted.
00:08It didn't happen overnight, like, I didn't wake up and couldn't stand straight.
00:12No, one day, I felt that my axis had shifted by 1 inch.
00:17Another day it was 2 inches.
00:19And once, you won't believe it, it was 31.5 inches!
00:24That's alarming!
00:25What if I accidentally turned upside down and all my inhabitants fall off my surface?
00:30Ah, dear Earth, we ran some tests and are ready to explain an unfortunate combination
00:36of factors that has affected your axis.
00:38The last one will perhaps be the most unexpected and upsetting.
00:43It all started back in March 2011, when a devastating magnitude 9 earthquake struck
00:49off the coast of Japan.
00:51It was so powerful that not only did it shift Earth's axis, but it also shortened the
00:56length of the day.
00:59This earthquake displaced our planet's axis by approximately 6.5 inches and may have moved
01:04Japan's main island by about 8 feet.
01:09Like other similarly massive earthquakes, it also altered Earth's rotation speed.
01:14To make it easier, let's compare it to a spinning ice skater.
01:19When a skater pulls their arms close to their body, they spin faster by concentrating their
01:23mass near the axis of rotation.
01:27Something similar happens during the most powerful earthquakes.
01:30They shift Earth's mass closer to its rotational axis, causing it to spin faster and shortening
01:37the day length.
01:38The calculations showed that the Japanese earthquake sped up Earth's rotation by about
01:431.8 microseconds, which is about 1.8 millionths of a second.
01:49Not a big deal, but at the end of the day, every nanosecond counts.
01:55For comparison, the infamous Indonesian earthquake shortened the length of a day by 2.68 microseconds.
02:03It struck on December 26, 2004, at 058 UTC.
02:09The epicenter lay off the western coast of northern Sumatra, Indonesia.
02:14This powerful undersea earthquake triggered devastating tsunamis that swept across the
02:19Indian Ocean, causing widespread destruction and immense loss of life in countries like
02:25Indonesia, Sri Lanka, India, and Thailand.
02:29Even coastal areas as far as East Africa had severe damage.
02:34The Earth's magnitude, initially recorded at 9.0 on the Richter scale, was later adjusted
02:41to between 9.1 and 9.3, making it the most powerful earthquake ever recorded in Asia.
02:49The faulted, that's when Earth's crust completely breaks and its parts slide past
02:54each other, lasted between 500 and 600 seconds, and it was the longest duration ever observed.
03:02The immense force of the quake caused the entire planet to vibrate by at least half
03:07an inch and triggered other earthquakes as far away as Alaska.
03:12All that immense energy the earthquake released caused subtle, but quite measurable changes
03:18to Earth.
03:19The shift in mass slightly changed the planet's rotation, shortening the day.
03:24It also caused a small wobble in Earth's axis, from 1 to 2.4 inches, toward 145-degree
03:32east longitude.
03:34So when it comes to changes in Earth's rotation speed and axis, it's all about the redistribution
03:40of mass.
03:42This can happen naturally, through disasters, but human activities can also trigger it.
03:49Take the Three Georges Dam for instance.
03:52This massive structure across the Yangtze River in China's Hubei province may seem
03:57to be an engineering triumph, but it's pretty ambiguous.
04:02Finished in 2012 after nearly 20 years, this massive dam is 7,660 feet long and 607 feet
04:11high.
04:12And yes, and yes, it is so big that it can affect the way our planet spins.
04:19Its reservoir is capable of holding 9.5 cubic miles of water, has enough mass to slightly
04:26alter the Earth's rotational inertia, slightly slowing the planet's rotation.
04:32According to NASA, the Three Georges Dam reservoir could shift Earth's pole position by almost
04:381 inch and increase the length of a day by 0.06 microseconds.
04:45Dams aren't the only worry.
04:47If polar ice melts, water rushes into the oceans, hiking up sea levels, especially near
04:52the equator.
04:54This mass shift slows Earth's spin way more than dams do.
04:58You won't feel it day to day, but it can affect ultra-precise equipment, such as atomic
05:03clocks.
05:05To fix this, scientists suggested a negative leap second, making a minute 59 seconds, to
05:11balance Earth's spin changes.
05:14Ok, so you're thinking you've got nothing to do with all those tilts.
05:20You don't build dams, right?
05:22Good news, if you take regular showers, you're part of it too!
05:27Every time you turn on the tap, you're affecting Earth's tilt just a tiny bit.
05:32Thing is, our planet is always shifting and adapting, so even small actions like using
05:38water can influence its orientation.
05:41Over the past two decades, groundwater pumping has caused the Earth's tilt to shift by 31.5
05:48inches.
05:49This water redistribution is equal to about 0.24 inches of sea level rise.
05:56It turns out that among climate-related causes, groundwater redistribution has the largest
06:01impact on the drift of Earth's rotational pull.
06:06But what is groundwater?
06:08It's the water stored beneath the Earth's surface, filling the spaces in soil, sand,
06:13and rock.
06:15It comes from rain and other precipitation that seeps into the ground, collecting in
06:19underground reservoirs, aquifers.
06:23Unlike rivers and lakes, groundwater stays below the surface, acting like a natural water
06:28reserve.
06:29Thanks to it, we have a steady supply even during dry periods.
06:34Many people, especially in rural areas, rely on groundwater as their main source of drinking
06:40water.
06:41Farmers use it to irrigate crops, while industries depend on it for manufacturing and cooling
06:46systems.
06:48It sounds pretty harmless, doesn't it?
06:50How can something so useful cause our planet to shift?
06:53Well, a study covering data from 1993 to 2010 revealed that we've pumped about 2,150 gigatons
07:02of groundwater in that time.
07:05And this large-scale water removal has shifted the Earth's tilt and rotation.
07:11After we use groundwater, much of it eventually flows into the oceans, contributing to rising
07:17sea levels.
07:19In areas like western North America and northwestern India, people use a lot of groundwater, and
07:26it may have a connection to these shifts.
07:28Yikes, let's face it, all these findings are rather disturbing.
07:34But you know, understanding the impact of groundwater use is already a huge step in
07:39the right direction.
07:40Hey, I'm not done yet!
07:43This tilting issue isn't just about stuff happening on Earth.
07:46We also need to look at space.
07:49We've talked a lot about water, right?
07:52Well you know that the Moon has a big role in that.
07:55Its gravity is super important for forming tides and all that.
07:59So one more thing that affects our planet a lot is the gradual movement of the Moon
08:04away from Earth.
08:07These two bodies interact gravitationally, which makes Earth's rotation slow over time,
08:12even though significant events like earthquakes occasionally speed it up temporarily.
08:18How did we figure it out?
08:20Glad you asked!
08:22Once someone paid attention to ancient corals.
08:26After analyzing them, scientists realized that Earth had once rotated much faster.
08:32The thing is, corals grow by laying down thin layers of calcium carbonate.
08:37They do it daily, and variations reflect seasonal changes.
08:42By counting these layers, scientists have calculated the number of days in a year millions
08:47of years ago.
08:49They found that Earth had about 420 days per year 444 to 419 million years ago.
08:58But over time, the Moon's influence had caused Earth's rotation to slow.
09:03And now we only have 365 days in a year.
09:08I feel robbed, you know?
09:11At the moment, the Moon is moving 1.5 inches away from Earth each year.
09:16That's about the same speed at which your fingernails grow.
09:20Astronomers have figured it out with the help of special mirrors placed on the Moon during
09:24the Apollo missions.
09:26For over 50 years, researchers have been sending laser beams to these mirrors and measuring
09:32the time it took for the light to bounce back.
09:35In any case, dear Earth, at the moment, your condition isn't critical.
09:40As for your inhabitants, they won't fall off your surface.
09:44All thanks to your gravity, pulling them toward your center.
09:47Just don't switch it off, and everything's gonna be fine!
09:51That's it for today!
09:52So hey, if you pacified your curiosity, then give the video a like and share it with your
09:56friends!
09:57Or if you want more, just click on these videos and stay on the Bright Side!
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