Where you'd actually end up by digging through the Earth

HostI spent a lot of time as a kid wondering what was directly under my feet. You look at a globe and it's so easy to assume there's a bustling city or some huge mountain range on the other side of the dirt. If I took a shovel to my backyard right now and just kept going, what are the odds I would actually pop out somewhere with people and buildings?

GuestHonestly, the odds aren't in your favor. Even though we think of the Earth as having plenty of land, about seventy percent of the surface is covered in water. But it's actually even more lopsided than that. Because of how the continents are spread out, only about four percent of the Earth’s surface has land directly opposite other land. We call these opposite points antipodes. So for almost everyone living in North America, Europe, or most of Asia, a straight tunnel through the center of the planet would just end up in the middle of a very deep, very cold ocean.

HostWait, only four percent? That feels incredibly low. If land makes up almost a third of the planet, I would've guessed the odds would be closer to that. Why do they drop so much when you go through the middle?

GuestIt's just the way the puzzle pieces fell. The land masses on our planet aren't balanced evenly at all. Most of the land is in the top half of the world, while most of the bottom half is just open sea. If you're standing in the United States and you start digging, you're not heading for a different culture or a new continent. You're heading for a really remote part of the southern Indian Ocean. You would be thousands of miles away from pretty much everything. It's a very lonely trip.

HostThat really kills the dream. I grew up hearing that if I just kept going, I would eventually end up in China. Is there anywhere in the states where that old story is actually true?

GuestNot even a little bit. For anyone in the northern half of the world, digging to China is a total impossibility. To actually come out in China, you would've to start your journey in South America, specifically in parts of Argentina or Chile. The closest landmass on the other side of a hole dug from the United States is actually the coast of Australia, but even then, most of us would miss it by hundreds of miles. The China thing is just a myth. It probably stuck around because China represented the most opposite culture people could think of historically, rather than anything based on a real map.

HostSo I would basically be swimming. But let’s say I could actually build this tunnel and survive the heat. I always figured that as you fall toward the center, gravity would just get stronger and stronger until it crushed you. Is that what I would feel?

GuestThat's the logical guess, but the reality is a bit of a surprise. On the surface, the whole weight of the Earth is beneath you, pulling you down. But once you're inside, something called the Shell Theorem kicks in. As you go down, all the dirt and rock that's now above your head starts to pull you back toward the surface. That upward pull begins to cancel out the downward pull from the mass below you. So, as you get deeper into the planet, gravity actually gets weaker.

HostThat's hard to wrap my head around. I would feel lighter the closer I got to the middle of the Earth?

GuestYou would. You would feel less and less weight as you fell. By the time you reached the very center of the Earth, you would be in a state of perfect weightlessness. You would be floating in the core because the weight of the entire planet would be pulling you in every single direction at the same time. The pull from the north would be the same as the pull from the south, and the same for every other side. You would just be drifting in the middle of the world with no sense of up or down.

HostIt's a bit of a lonely picture. Floating in the dark and then popping up in the middle of the ocean. Are there any lucky cities that actually have a land twin on the other side?

GuestThere are only a handful of perfect matches where land meets land. Spain and New Zealand are the big ones. If you started a hole in Madrid, you would surface very close to a small town called Weber in New Zealand. There are a few others, like Bogota in Colombia, which sits right across from Jakarta in Indonesia. Or Hong Kong, which is roughly opposite the Jujuy Province in Argentina. But for almost everyone else, the journey is a lonely one. If you dug from the center of London, you would come up in the water off the coast of New Zealand. From Tokyo, you would hit the Atlantic Ocean near the coast of Uruguay. It really shows how much our world is dominated by the deep.

HostThe reality is that we live on these small patches of land that are almost all backed by nothing but water.

GuestMost of the ground we walk on is just facing a vast, deep stretch of blue on the exact other side of the world.

HostMy backyard shovel feels a lot less like a way to explore the world and a lot more like a very long walk to a very lonely swim.