- 6 months ago
What's really down in the deep Earth?
Have you ever thought, “what if I just dug a really really deep hole?”
Well, the USSR actually did. The hole they dug is deeper than the deepest part of the ocean. It’s deeper than Mt. Everest is tall! They began digging it in the 1970s as part of a space race, but down. The United States only got to 600 ft before pulling funding. But the USSR kept going for 20 years. They made it about a third of the way through the Earth’s crust and then STOPPED.
But what if… you just… kept... digging?
If you dug a hole to the center of the Earth, what would you find? What would happen to you? And what does our newest tech tell us is REALLY down below your feet?
In this video, we’re going on a journey to the center of the Earth…
Chapters:
0:00 What if you dug a hole to Earth’s core?
1:05 What happens when I start digging?
1:36 What are the deepest made-made things?
2:25 What is the deepest hole humans ever dug?
3:03 What happens in the mantle?
3:45 Why is the Earth hot?
4:38 What did we used to think was inside the Earth?
5:06 How do we know what’s inside the Earth??
5:59 What’s inside the core?
6:26 Um, the magnetic field switches direction??
7:13 Why is the Earth in layers?
8:53 What’s at the center of the Earth?
9:46 Earth’s core spins at its own rate??
10:52 What don’t we know?
11:33 Subscribe to support Huge If True!
Bio:
Cleo Abram is an Emmy-nominated independent video journalist. On her show, Huge If True, Cleo explores complex technology topics with rigor and optimism, helping her audience understand the world around them and see positive futures they can help build. Before going independent, Cleo was a video producer for Vox. She wrote and directed the Coding and Diamonds episodes of Vox’s Netflix show, Explained. She produced videos for Vox’s popular YouTube channel, was the host and senior producer of Vox’s first ever daily show, Answered, and was co-host and producer of Vox’s YouTube Originals show, Glad You Asked.
Have you ever thought, “what if I just dug a really really deep hole?”
Well, the USSR actually did. The hole they dug is deeper than the deepest part of the ocean. It’s deeper than Mt. Everest is tall! They began digging it in the 1970s as part of a space race, but down. The United States only got to 600 ft before pulling funding. But the USSR kept going for 20 years. They made it about a third of the way through the Earth’s crust and then STOPPED.
But what if… you just… kept... digging?
If you dug a hole to the center of the Earth, what would you find? What would happen to you? And what does our newest tech tell us is REALLY down below your feet?
In this video, we’re going on a journey to the center of the Earth…
Chapters:
0:00 What if you dug a hole to Earth’s core?
1:05 What happens when I start digging?
1:36 What are the deepest made-made things?
2:25 What is the deepest hole humans ever dug?
3:03 What happens in the mantle?
3:45 Why is the Earth hot?
4:38 What did we used to think was inside the Earth?
5:06 How do we know what’s inside the Earth??
5:59 What’s inside the core?
6:26 Um, the magnetic field switches direction??
7:13 Why is the Earth in layers?
8:53 What’s at the center of the Earth?
9:46 Earth’s core spins at its own rate??
10:52 What don’t we know?
11:33 Subscribe to support Huge If True!
Bio:
Cleo Abram is an Emmy-nominated independent video journalist. On her show, Huge If True, Cleo explores complex technology topics with rigor and optimism, helping her audience understand the world around them and see positive futures they can help build. Before going independent, Cleo was a video producer for Vox. She wrote and directed the Coding and Diamonds episodes of Vox’s Netflix show, Explained. She produced videos for Vox’s popular YouTube channel, was the host and senior producer of Vox’s first ever daily show, Answered, and was co-host and producer of Vox’s YouTube Originals show, Glad You Asked.
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LearningTranscript
00:00If you've ever thought, what if I just dug a really, really deep hole?
00:04That's what the USSR did right here.
00:06That hole is deeper than the deepest part of the ocean.
00:09It's deeper than Mount Everest is tall.
00:11They started digging it in the 1970s as part of basically a space race, but down.
00:16The United States only got to 600 feet before pulling funding,
00:19but the USSR kept going for 20 years.
00:23They made it about a third of the way through Earth's crust, and then it stopped.
00:29But what if you just kept digging?
00:33If you dug a hole all the way to the center of the Earth, what would you find?
00:38What would happen to you?
00:40And what does our newest tech tell us is really going on down below our feet?
00:44Let's take a look at what's inside.
00:46Journey to the center of the Earth.
00:47Went where no human being had ever set foot.
00:49We're still falling!
00:51The center of the Earth.
00:52The heat and the pressure.
00:53What's underneath the Earth's crust is different.
00:55The deeper you go into the Earth, the hotter it gets.
00:58That's wild.
01:08Imagine we go outside, and we just start digging.
01:11At about 50 meters deep, we might start to feel the temperature go up.
01:14Every kilometer through the crust is about 25 degrees Celsius hotter.
01:17Right now, we're inside the crust.
01:19On land, it's typically less than 40 kilometers deep, which is less than the length of a marathon.
01:23We're passing through soil and layers of hard rock past precious metals and fossils.
01:28And as we get deeper, we start to see all kinds of impressively deep things that people have built.
01:32Like there's the Kemioka and Sanford research labs that do dark matter and neutrino physics research.
01:37Or there's China's insanely deep nuclear command bunker.
01:41There's the deepest cave we've ever discovered.
01:43Plus some of the deepest mines in the world.
01:45As we go deeper, temperature and pressure continue to rise.
01:48But by this point, unprotected just in the Earth, we were crushed and crispy a while ago.
01:54To go farther, let's equip ourselves with an imaginary drilling machine that's immune to any temperature or pressure.
02:00Now, finally, at 12.2 kilometers, we reach the deepest point humans have ever dug.
02:06This is that hole the USSR dug, the Kola Superdeep Borehole.
02:10They didn't put any humans down here. This equipment was operated remotely.
02:13To get so deep, these scientists had to invent new equipment and drilling methods to pierce through the thick, hot, pressurized rock.
02:18Along the way, they discovered new fossilized organisms dating back 2 billion years.
02:23And found there was water, much deeper than scientists previously thought.
02:26We actually emailed three of the scientists who worked on this project, and one of them told us, quote,
02:31The Russians tried several times to get down past the maximum depth that they had reached.
02:35But each time, the new hole tended to collapse.
02:38This was a moonshot, which will never be repeated or surpassed.
02:42This is so cool.
02:43But the craziest part is, this deepest hole that humans have ever dug is only 0.2% of the way to the center of the Earth.
02:52Time to go deeper.
02:54At about 30 to 50 kilometers down, we notice that the rock around us is changing.
03:01We're crossing into the mantle.
03:03At first, the rock around us looks really brittle, like the crust, but denser.
03:07But as we get a little deeper, as the temperature rises over 1,300 degrees Celsius, something weird starts to happen.
03:14The rock around us starts to look like hot plastic.
03:18Here, the temperature is higher than the melting point of the rock, but the pressure is so high that it's still keeping the rock solid.
03:25It's gooey.
03:26We're now starting to push through even hotter material.
03:29It's slowly inching from the bottom of the mantle toward the top in these giant convection currents over millions of years.
03:36And you might be wondering, why is the Earth hot?
03:39Well, it's partly radiation, and partly leftover heat from when the Earth formed by meteorites smashing against each other over and over again.
03:46The Earth is cooling very, very slowly, but we don't need to worry about that.
03:51It's going to take billions of years.
03:53In the meantime, this stirring of hot goop brings enormous amounts of heat from the center toward the crust.
04:01But hang on, how do we know that?
04:04If humans have only ever been 12 kilometers down, how do we know that?
04:09Yeah, that's a great question.
04:11That's Dr. Megan Newcomb, a geologist and volcanologist at the University of Maryland.
04:15She told me that studying the deep Earth is like being a detective.
04:19We can't get there, so we have to put together all of these indirect pieces of evidence to work out what's going on down there.
04:26Ancient scientists had a lot of theories about what was going on down there.
04:29Some thought the Earth contained a central fire with underground lakes and lava chambers.
04:34Some thought it was hollow, maybe a set of concentric shells with life on each ring.
04:38This is the basis for the hollow Earth in the Godzilla movies.
04:41Isaac Newton suggested that based on observable gravity, the stuff in the center must be denser than the stuff at the top.
04:47But it wasn't until the early 20th century that scientists could prove that the Earth had a central core, and that there were several different layers above it.
04:54These breakthrough discoveries were thanks in large part to earthquakes.
04:58During an earthquake, we feel it up here, but it's also sending seismic waves down.
05:03They are just like sound waves, but there are two main varieties.
05:06There's P waves and S waves.
05:09P waves can travel through liquids and solids, but S waves can only travel through solids.
05:13They also behave differently depending on the density of the rock that they're moving through.
05:16Which means that by measuring what waves end up at different detectors all over the surface, scientists can understand what's going on between them.
05:24That's one big way that we've learned about how the mantle differs from the crust, and it also taught scientists something else.
05:30We find this S wave shadow on the opposite side of the planet that tells us that for some reason the S waves couldn't propagate all the way through the Earth.
05:40And that tells us that there's a liquid layer down there.
05:43That liquid layer is part of what we now call the outer core.
05:50We've now crossed into a liquid soup of metals, cooking at around 4,400 degrees Celsius.
05:56Here, temperature has won the fight against the pressure, and we should all be extremely grateful for the hot metal soup down there.
06:02Because its constant churning generates enormous electric currents, which in turn create the magnetic field around the Earth.
06:08And without that, cosmic radiation would just end all life as we know it on the surface.
06:12But this gets weirder.
06:13Our magnetic field sometimes actually just reverses.
06:18The North and South Poles slowly swap places.
06:22And we know that because...
06:25You can actually read off all of those magnetic reversals on the ocean floor.
06:29Yeah.
06:30As basalt is erupted along our mid-ocean ridges, it freezes in a record of what the magnetic field was at that time.
06:37And as the plates continue to get created and pulled apart, we can read them off like a barcode.
06:43So what you're telling me is there's a barcode for our magnetic fields at the bottom of the ocean, and scientists have learned to read it.
06:51Mm-hmm.
06:52Excellent.
06:53You can read this too.
06:54It flipped here.
06:55It flipped here.
06:56It flipped here.
06:57The last reversal was around 780,000 years ago.
07:00When will it flip next?
07:01We're not sure.
07:02But I had a much more basic question about all of this.
07:05Why is the Earth in layers?
07:07You're gonna like this one.
07:08At the beginning, we were a magma ocean.
07:12The entire Earth was molten liquid.
07:15During that time, the densest materials, which are the iron, metal, and sand conformed the core.
07:22And then the lightest minerals floated to the top and the densest minerals settled to the bottom.
07:29And so we've segregated by density.
07:32Okay, we've almost made it through all of those layers.
07:34We are deep inside the Earth's outer core.
07:37And then you hit something.
07:39Hang on, though.
07:40If you're going on a real-life adventure, you might want to take this.
07:43This is my water bottle.
07:44This is the Lark PureViz 2.
07:46And what's cool about it is that when I press this, it's purifying the water inside.
07:52It uses UV light to break down the chemical bonds of bacterial DNA, specifically E. coli and salmonella.
07:57That keeps the inside clean compared to a water bottle without that.
07:59In this example here, they swab the inside of two water bottles used for four weeks.
08:03Lark is on the left and a water bottle like the one I used to have is on the right.
08:06Then they waited to see what bacteria grows from each.
08:08And... blech.
08:09The PureViz 2 also has a plant-based filter that removes pollutants.
08:14So better taste, healthier water.
08:16Plus, and this is my favorite part, it helps me remember to drink enough water.
08:19This is my real data from the last week.
08:21You can see I'm hitting my goal almost every day.
08:24The way this works is it has a little sensor in the cap that measures the water level inside after each sip.
08:29So I get real-time insights on my progress.
08:31The light ring on the cap will light up to remind me to drink water.
08:34And you can set the frequency of that in the app.
08:36So I have mine set to every hour.
08:38And it has a double wall insulation that keeps water cool for 24 hours.
08:41If you want to check it out, there's a link in my description.
08:44Now, back to the story.
08:49At the very center of our planet, there is a solid metal ball that's almost as hot as the surface of the sun.
08:57And for a long time, we didn't know it was there.
08:59We assumed that everything in the core was molten, because why would it be solid?
09:03But then, these two scientists were studying more of those seismic waves.
09:06And they noticed that when those waves got to the center, they started to act weird.
09:11Waves were being bent and reflected by something in the middle.
09:14The math only made sense if there was a solid core inside the larger liquid one.
09:18Other scientists confirmed this theory, with more precise recordings of the waves and better computational models.
09:23So why is it solid?
09:25Well, it turns out that the pressure here is so insanely high that the iron atoms literally can't move.
09:32And what's even stranger is that more recently, scientists have found slight discrepancies in the data
09:37that seem to show Earth's core is rotating at a different rate than we are at the surface.
09:44And that rate changes.
09:47It is speeding up and slowing down separately from what we're doing up here.
09:52Because...
09:54Why not?
09:55Very precise seismic data and computer models of our magnetic fields show that the Earth's inner core
10:00seems to be speeding up and slowing down on a roughly 70-year cycle.
10:03You might have seen headlines that the Earth's core is reversing, but that's not true.
10:07It's just that if you were on the outside of the inner core and I'm on the surface,
10:11it would look to me like you were going the opposite direction if you're slowing down,
10:16even if we're both moving the same direction.
10:18But this iron core is no match for our magical digger.
10:21We are going straight through it until finally...
10:24We did it.
10:25We made it to the very center.
10:27We are now 6,400 kilometers from the surface.
10:32The pressure around us is 3.6 million times what it is on the surface.
10:38But in lots of ways, what's around us right now is still a big mystery.
10:42Like, is there an inner inner core?
10:44Some scientists think that there might be.
10:46There's new seismic data that suggests that the iron atoms are packed differently way on the inside,
10:51but others aren't so sure that that's enough to call it a new layer.
10:54We've been wrong before, but we're becoming better detectives.
10:57Can we predict the Earth's magnetic field and when it might flip?
11:00Scientists are building experiments that mimic the inner Earth to learn more.
11:03Now the cutting edge is finding new ways to analyze seismic waves with better computational models
11:08and even finding ways to replicate the deep Earth conditions here on the surface.
11:12We are a curious species, locked on the outside of our own home.
11:16And we're doing everything we can to peek inside.
11:20That's what's so cool about science and technology.
11:22It lets us explore strange new worlds, including the one right below your feet.
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