Hi, I’m Digby! Want to know what’s under your feet?
Learn what’s under your feet
Quick, fun explainers about the planet you’d be digging through, from the crust to the core.
Data stories
Explainers
- Where would you end up if you dug a hole through the Earth?Dig straight down through the center of the planet and you’ll pop out at the exact opposite point, your antipode. For most people that’s the middle of an ocean. Here’s where every part of the world comes out.
- Could you really dig a hole to China?Generations of American kids were told that if you dug deep enough you’d reach China. Here’s where you’d actually come out, and why nobody will ever make the trip.
- Earth’s layers: what you’d dig through on the wayThe crust, mantle, outer core and inner core, explained in the order you’d hit them if you tunneled straight through the planet.
- How long would it take to fall through the Earth?Jump into a frictionless tunnel through the center of the planet and you’d pop out on the other side about 38 minutes later. Here’s why, and why the answer is 42 minutes for a planet like a bowling ball.
- What is an antipode?Your antipode is the point on the exact opposite side of the Earth. Here’s how to find it, why it’s usually in the ocean, and which cities are almost perfect opposites.
- The deepest hole ever dug, and why it stoppedThe Kola Superdeep Borehole went 12 km into the Earth, hit rock hotter than anyone expected, and still only got about 0.2% of the way to the center.
- How do we know what’s inside the Earth?Nobody has ever been deeper than about 12 km, yet we know the core is iron and partly liquid. Here’s the detective work, from earthquake waves to space rocks to squeezing iron in a diamond vise.
- Why is Earth’s core so hot?The center of the Earth is roughly as hot as the surface of the Sun, 4.5 billion years after the planet formed. Here’s where all that heat came from, and why it hasn’t leaked away.
Quick facts
- Only about 13% of land has land on its exact opposite side. Most tunnels end in the ocean.
- Dig straight down from almost anywhere in the United States and you come out in the Indian Ocean, not China.
- To actually dig through to China, you’d have to start in Argentina or Chile.
- Córdoba, Spain and Hamilton, New Zealand are almost perfect opposites, only about 13 km off.
- The deepest hole ever drilled, Russia’s Kola Superdeep Borehole, reached 12,262 m. That’s about 0.2% of the way to Earth’s center.
- Earth’s inner core is around 5,000–6,000 °C, about as hot as the surface of the Sun.
- Falling through a frictionless tunnel straight through Earth would take about 38 minutes.
- Earth is slightly squashed: a tunnel from pole to pole would be about 43 km shorter than one through the equator.
- Compared to the whole planet, the crust you live on is about as thin as the skin of an apple.
- The mantle makes up about 84% of Earth’s volume.
- Nobody has ever seen Earth’s core. We know the outer core is liquid because one kind of earthquake wave (S-waves) can’t pass through it.
- Inge Lehmann discovered Earth’s solid inner core in 1936 by studying earthquake waves.
- Earth’s magnetic field comes from liquid iron churning in the outer core.
- Pressure at Earth’s center is about 3.6 million times the air pressure around you right now.
- Walking to the other side of the world is about 20,000 km. Tunneling through the middle is only about 12,700 km.
- The inner core is about 70% as wide as the Moon.
- Most of Tonga’s opposite side lands in the Sahara, in Algeria. digthru.to is a Tongan web address.