Learn
What's really down there?
A tunnel to the other side of the world is impossible, but everything you would pass through is real. Start anywhere.
The journey down
Inside the EarthThe layers of the Earth, from crust to coreA guided trip through the Earth's crust, mantle, outer core and inner core: how deep each layer is, what it's made of, how hot it gets and how we know.
Layer 1 of 4The crust: the thin skin we live onEarth's crust is 5 to 70 km thick and less than 1% of the planet. Learn what it's made of, why continents and ocean floors differ, and how old the oldest rocks are.
Layer 2 of 4The mantle: solid rock that flowsThe mantle is 2,900 km thick and makes up 84% of Earth's volume. It is solid, yet it flows a few centimeters a year and drives earthquakes, volcanoes and moving continents.
Layer 3 of 4The outer core: a liquid metal oceanEarth's outer core is a 2,260 km thick ocean of liquid iron and nickel. Its churning creates the magnetic field that protects life on Earth.
Layer 4 of 4The inner core: a solid iron ball as hot as the SunEarth's inner core is a solid iron-nickel ball 1,221 km in radius, about 5,400 °C hot. Discovered by Inge Lehmann in 1936, it is still growing today.Records and places
The deepest holeThe Kola Superdeep Borehole: the deepest hole ever dugIn 1970 Soviet scientists started drilling toward the mantle. After 19 years they reached 12,262 m, still the deepest point humans have reached. Here is what they found.
The MohoThe race to drill into the mantleNobody has ever drilled through the crust into the mantle. The story of Project Mohole, the ships that tried, and the record core of mantle rock pulled up in 2023.
RecordsThe deepest places humans have ever reachedThe deepest cave, mine, ocean trench and borehole on Earth, compared side by side. The deepest of them all reaches 0.2% of the way to the center.
GeographyAntipodes: what's on the other side of the EarthYour antipode is the point exactly opposite you on the globe. Most are in the ocean. Only 15% of land has land on the other side. See the map and the famous pairs.
Remote placesPoint Nemo: the place farthest from landPoint Nemo in the South Pacific is 2,688 km from the nearest land. Old spacecraft are deliberately crashed there, and the closest people are often in orbit overhead.Science and physics
ScienceHow do we know what's inside the Earth?Nobody has been deeper than 4 km, yet we know the Earth has a liquid outer core and a solid inner core. Here is how earthquakes, meteorites and physics revealed it.
HeatWhy is the inside of the Earth still hot?About 47 terawatts of heat leak out of the Earth, roughly half left over from the planet's birth and half from radioactive decay. Why it has not cooled down in 4.5 billion years.
MagnetismThe magnetic field made by liquid ironEarth's magnetic field is generated by churning liquid iron 2,900 km down. It shields the planet, its poles wander, and every few hundred thousand years it flips.
PhysicsHow long would it take to fall through the Earth?Jump into a tunnel through the Earth and you'd reach the other side in about 38 to 42 minutes, hitting 28,000 km/h at the center. Here is the physics of the gravity train.
Quick facts15 surprising facts about the inside of the EarthThe center of the Earth is as hot as the Sun, the mantle may hold more water than the oceans, and the deepest hole ever dug covers 0.2% of the way. 15 facts, all sourced.