Book 12, Question 69
How Do Scientists Know What Is Inside Earth When Nobody Has Ever Dug That Deep?
Nobody has ever dug anywhere near the center of Earth, and the deepest hole ever drilled is only about 12 kilometers deep. Scientists learn what is inside by studying earthquake waves that travel through the whole planet. The waves bend, speed up, and slow down in different layers, and that reveals what is down there.
More fun facts
- Earth's center is about 6,400 kilometers (3,977 miles) beneath our feet.
- The deepest humans have ever drilled is just over 12 kilometers (7.6 miles).
- Except for the crust, no one has ever explored Earth's layers in person.
- Scientists learn about the inside of Earth by studying how earthquake waves travel through it.
- Earthquake waves change speed and behavior when they hit layers of different density.
- Isaac Newton and others learned about the core and mantle using Earth's total density and gravity.
Sources: Science News Explores, Smithsonian Magazine, National Geographic
Questions kids ask
What are Earth's layers?
From deepest to shallowest: inner core, outer core, mantle and crust.