How has the inside of the Earth stayed as hot as the Sun’s surface for billions of years?
Shichun Huang does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
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Starting from the top down, there’s the crust, which includes the surface you walk on; then farther down, the mantle, mostly solid rock; then even deeper, the outer core, made of liquid iron; and finally, the inner core, made of solid iron, and with a radius that’s 70% the size of the Moon’s. The deeper you dive, the hotter it gets – parts of the core are as hot as the surface of the Sun.
As a professor of earth and planetary sciences, I study the insides of our world. Just as a doctor can use a technique called sonography to make pictures of the structures inside your body with ultrasound waves, scientists use a similar technique to image the Earth’s internal structures. But instead of ultrasound, geoscientists use seismic waves – sound waves produced by earthquakes.
