Can You Drill Through Earth? | Through the Core

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What Happens if You Drill Through the Earth?</h4>

Planet Earth weighs about 6 sextillion tons. It has a surface area of 197 million square miles, and a diameter of between 7,900 and 7,926 miles. If it were possible to drill through it, you’d pass through the crust, the mantle, the outer and inner cores, and then the same again in reverse. Would you make that journey?

Earth’s underground environments are a mostly unknown world. There are thousands of complex cave systems, full of strange creatures that never see the light of day, with some leading so far down that no human has yet explored them. But, at these absolute extremes, if we did explore them, then how far could we really go?

This is Unveiled, and today we’re answering the extraordinary question; what happens if you drill through the Earth?

First off; what is the Earth actually made of? At its simplest, it consists of crust, either oceanic or continental, with sections (known as tectonic plates) covering the entire surface. The crust is then always made of rock, but of different rocks in different places and at different layers. Below this topmost layer there’s the mantle, which is Earth’s magma source. And then, finally, we have the core, both the inner and outer. The core is thousands of miles down, incredibly dense, and billions of years old. Here, at the heart of our planet, it’s made of super-hot, super-dense iron and nickel, and temperatures can be more than 10,000 degrees Fahrenheit.

We know, then, that inside the Earth isn’t exactly a welcoming place. But, nevertheless, humans are still intrigued by all that’s below us. Ideas about the Earth perhaps being hollow and hosting unknown ecosystems have appeared in science fiction for a long time. And although the Hollow Earth Theory doesn’t actually hold up, there certainly ARE strange and genuine underground realms that are intriguing, even bewitching. The deepest known natural cave on Earth is Veryovkina Cave in Eastern Europe. At about ten miles long and more than 7,000 feet deep, it’s an extreme and unique environment. If it were an ocean instead of a cave, its depth would put it firmly in what’s known as the bathypelagic zone, with pressure hundreds of times greater than what’s found at the surface. Unfortunately, and perhaps unsurprisingly, some explorers have died inside Veryovkina Cave. Ultimately, though, it’s very likely that Veryovkina is even deeper than we currently know. And also that there are other, far deeper cave systems out there that haven’t even been discovered yet. What really puts the scale of the Earth into perspective, however, is that in all cases we are still a long way away from reaching down into even Earth’s second layer, the mantle. Let alone further still, to the core and out the other side.

Do man-made caves offer any improvement? To some degree, yes. Veryovkina Cave is about 1.3 miles deep, but the deepest mine in the world, the Mponeng gold mine in South Africa, is almost double that, reaching 2.5 miles. If we abandon traversable underground systems - i.e., if we look at the deepest locations, but ones that humans can’t travel down into - then we come to what’s truly the deepest man-made hole in the world, the Kola Superdeep Borehole in Russia. It is more than 7.6 miles deep and is a real benchmark in the field, given that it was a drilling project conceived solely to see how deep it was possible to drill into Earth’s crust. Thankfully, the borehole is only about 9 inches wide and is now sealed off, so there’s no danger of anybody falling into it. But, even if you did, you’d still (and again) be WAY off of how deep you’d need to go to reach the core, or to emerge out the other side. There’s simply nothing on Earth currently that takes us even close.

The middle of the core is about 4,000 miles below the surface, meaning we’d need to dig an 8,000-mile tunnel to punch through to the other side of our planet. The longest, still-in-use tunnel in general (going across the Earth and not down into it) is the Delaware Aqueduct in the US. But it is only about 85 miles long. We’d need, then, almost 100 times more, and it would all have to withstand untold pressure and temperature. In reality, drilling through the Earth - as simple as it sounds - isn’t something that’s yet technologically possible for humanity.

But, say that money is no object, some kind of tech solution is discovered, and that the entirety of our species has (for some reason) decided that we really, REALLY need to create this passage. What then?

First, we’d need a material not only to build the tunnel out of, but also our drilling apparatus. Again, that material would need to be capable of withstanding extreme temperatures and depth. There are those highs of around 10,000 degrees Fahrenheit, while the pressure would top out at about 3.6 million atmospheres. For context, the deepest known point in the ocean, Challenger Deep in the Marianas Trench, has about 1,000 atmospheres of pressure. Even it just isn’t comparable. When thinking of materials that could work, you might immediately go to diamond… which can cope with up to five times as much for the pressure. However, the melting point of diamond is a paltry 7,200 degrees Fahrenheit, so it would inevitably melt part way through our journey. Which is a shame, because a diamond drill for a diamond tunnel seems like it would be a pretty cool thing. Scientists HAVE researched this specific problem, however, and have before come up with a new material that combines “hafnium”, nitrogen and carbon – hafnium being a lesser-known transition metal. But even this fares only slightly better than diamond, with a melting point of 7,460 degrees. Even our most thoroughly researched, custom materials can, then, only get us to the “edge” of Earth’s core. And, of course, only in theory. Staging any kind of practical test for what we’d need - some kind of new wonder-metal or element - is basically impossible.

But, hypothetically, say we DO have such a material. What other obstacles would our Earth-splitting tunnel face? The consistency – or, rather, inconsistency - of Earth is another problem. Drilling through rock is one thing - and, in fact, is the only thing we know - but eventually, you get to the mantle, full of heavy, molten lava. So, in carving our tunnel we would need a craft that can drill through the ground, yes. But it would then need to become the most extreme submarine ever, capable of wading through magma. And then it would need all those temperature and pressure resistance qualities, in order to survive the core. Anything that could do all of that would be some machine!

But, hypothetically, say we DO have such a machine. Next, we’d have severe navigation problems, since there would be literally zero visibility for the very vast majority of our mission. And then, the heat remains a major issue, even with an indestructible, hypothetical wonder-material. Because just because something won’t melt when subjected to thousands of degrees, doesn’t mean it won’t get so hot inside that humans can’t survive. The conditions on the inside of our tunnel through the Earth would be hellish. More than that, they would boil you alive. So here’s hoping we develop some ultra-advanced climate control systems, as well.

But maybe we have all of that, too. We’ve got our tunnel made from an impossible material, the incredible machine needed to actually build it, some super-advanced air conditioning, and some sort of vehicle that can withstand the entire journey. How long would that journey take? Again, we have 8,000 miles to traverse. The fastest train in the world is currently the Shanghai Maglev in China, which travels at 286 miles per hour. At that constant speed, we’re talking nearly 28 hours to tunnel through the planet. Which is longer than it would take to just fly between the two points on an airplane. 

But here’s where one final (and crucial) consideration comes into play. Because when drilling through the Earth, we’re actually not beholden by how fast trains (or anything) can move on the surface. The force of gravity messes all that up. As it’s pulling everything directly towards the core all the time, we know that the journey to the center of the Earth would, in reality, be much shorter. It would potentially take less than an hour. However, there’s a catch, and a big one. Because, with gravity pulling you in, how can you ever hope to get away? Your journey from the center of the Earth - the second half in terms of plain distance - just isn’t going to happen. Unless you manage to conduct the entire journey also in a total vacuum, then no matter what you do, gravity will always mean that it’s actually impossible for you to leave. So, even if you have managed to build a tunnel to withstand the pressure which means that you haven’t been crushed… you’d still find yourself hopelessly cast adrift, trapped in a tomb of your own making, waiting to starve and eventually die. Which… isn’t really the ending we were hoping for.

But, what do you think? Would digging a tunnel through the Earth be worthwhile, or would it just be completely absurd, even if it WERE possible? For now, the want to explore is usually to be applauded… but, sometimes, even the most fundamental laws of physics are telling you that it’s probably a bad idea. And that’s what would happen if you drilled through the Earth.