What Would Happen if We Drilled a Tunnel Through Earth?

What if you could journey through the very core of our planet? Inspired by the imaginative question from our curious friend, 11-year-old James, we embark on a thrilling thought experiment. We tackle the monumental challenges of drilling through Earth's diverse layers—from the rocky crust to the fiery mantle, and even the molten outer core to the solid inner core. With today's technology and these extreme conditions, it seems drilling through the Earth is merely a dream... or is it?

Episode Transcript

Hey there, curious minds, welcome to, I Wonder, the show where we explore the questions you've been wondering about. Today's question comes from James, who's 11 years old. James asked what would happen if you drilled a hole all the way through the arth. That is a wild thought, James. Imagine dropping something or even jumping into a hole that goes all the way from one side of the planet through to the other. Sounds like something out of a sci-fi movie. We love thought experiments like this. So let's explore the idea and break down the science of what would happen if we actually drilled a hole through the earth.

Before we talk about what would happen, let's think about whether it's even possible with today's technology. Drilling through the Earth would be a huge challenge, because our planet isn't just made of dirt and rock. Earth has several layers, each with different properties, and some of them would be almost impossible for any drill to actually get through. If we started drilling from the Earth's surface first, we'd go through the crust, which is the outmost layer and is only about 30-40 kilometers thick on average. This layer is rocky, relatively cool, so a powerful drill could theoretically get through it with some effort. But below the crust is the mantle, a layer that extends almost halfway to the Earth's center and is made of hot semi-solid rock that flows very slowly. Over time, temperatures in the mantle can reach thousands of degrees Celsius. That's That's way too hot for any regular drill. And it gets even more intense as we go on. Beneath the mantle is the outer core, which is made of molten iron and nickel and reaches temperatures of around 4,000 to 6,000 degrees whoa. And finally, at the very center, is the inner core, a solid ball of iron and nickel with temperatures as high as 9,000 degrees Celsius. These these temperatures and pressures would destroy any drill. So in reality, it's not possible to dig all the way through the Earth with our current technology.

But for the sake of experiment, let's imagine that we somehow had a magic tunnel that goes all the way through the Earth without collapsing or melting. How long do you think this tunnel would have to be? The Earth's diameter is about 12,742 kilometers, so this tunnel would be close to 13,000 kilometers long. It's a distance that's so massive that it's pretty hard to picture. And if you started digging the tunnel in North America, where would you come out? Well, you'd actually end up in the Indian Ocean. For example, a tunnel that starts in New York City would emerge southeast of Madagascar. If you began in Los Angeles, California, you'd also end up in the Indian Ocean near the coast of Namibia, Africa. Most places on land are directly opposite oceans, so there are very few points on Earth where a tunnel could connect two pieces of land.

Alright, now let's imagine jumping into this magical tunnel tunnel. Gravity would pull you downward, making your fall faster and faster. But how fast would you actually go? If there were air in the tunnel you'd quickly reach something called terminal velocity. This is the fastest speed an object reaches when gravity pulling it down is balanced by air pushing up against it. For a person, terminal velocity is usually around 200 kilometers per hour, that's about 120 miles per hour. So if the tunnel had air, you'd reach the speed and stay at it, never getting any faster.

But if the tunnel were a vacuum, meaning it had no air in it at all, things would get a lot more interesting. In a vacuum, there's no air resistance, so you'd keep accelerating all the way to the Earth's center. By the time you reached the core, you'd be moving at around 28,000 kilometers per hour that's 17,000 miles per hour. That's about as fast as a spacecraft orbits the Earth. Once you passed the center and began traveling toward the other side, gravity would start slowing you down until you eventually reached the opposite surface, where you'd come to a stop. But if you were in a vacuum tunnel with no air resistance, your journey from one side of the Earth to the other would take around 42 minutes. This is because of a type of movement called harmonic motion, which is similar to a swinging pendulum. Just as a pendulum moves back and forth, you'd oscillate through the tunnel, moving faster near the center and slowing down as you approached each end. Without air resistance, you'd keep swinging back and forth forever, taking 42 minutes to complete each journey. But with air resistance, your speed would slowly decrease and eventually you'd stop near the Earth's center, floating weightlessly as gravity pulled on you equally from all directions.

As cool as it sounds, a tunnel through the Earth would be extremely challenging and really dangerous to build. Just imagine the engineering problems. The heat and pressure would require materials far stronger than anything we currently have. Plus, if the tunnel passed through the molten outer core, it would likely collapse due to the intense conditions. Even if we managed to build it, maintaining such a structure would be nearly impossible due to the constant movement of tectonic plates in the crust and mantle. Oh yeah, and then there's the issue of safety. If anything went wrong in the tunnel, it would collapse, making it a major hazard. So it's a fun idea to imagine, but for now a tunnel through the Earth is best left to science fiction.

So if we can't drill to the center of the Earth, how do scientists know what's really down there? Geologists and seismologists use seismic waves, those are waves of energy created by Earthquakes or explosions. To study the Earth's interior, these waves travel through the Earth and by measuring how fast they move and how they change direction, scientists can learn about the different layers and what they're made of. For example, seismic waves move faster through solid rock then through molten metal, so scientists can identify where the solid and liquid parts of the Earth's interior are located. This is how we know about the crust, mantle, outer core and inner core, even though we've actually never visited them ourselves.

Here's a cool thought If you could travel to the center of the Earth, you'd experience some of the highest temperatures and pressures known on our planet. The pressure at the core is over 3 million times the pressure we feel at sea level and the temperature is as hot as the surface of the sun. The core is mostly iron and nickel compressed into a solid because of all that pressure. While we may never feel the Earth's core directly, learning about it through seismic studies and other scientific methods gives us a glimpse into the heart of our planet. It's amazing to think that we've learned so much without ever going there ourselves.

So, to answer James's question, if you drilled the hole all the way through the earth, it wouldn't be practical or even possible with today's technology. But if you could somehow create a magical tunnel, you'd experience gravity pulling you toward the center, where you'd be weightless. You'd reach incredible speeds up to 28,000 kilometers per hour if the tunnel were in a vacuum and travel from one side of the Earth to the other in about 42 minutes. If the tunnel was not a vacuum and had air resistance, then you would accelerate to terminal velocity around 200 kilometers per hour until you reached the center, at which point you'd float weightlessly as gravity pulled you equally in all directions.

Thanks again to James for such a mind-bending question and remember, if you have a question you're curious about, send it our way to www.iwonderpodcast.com and we might just feature it in our next episode of I Wonder. Until next time, stay curious and keep wondering.