How do scientists know about the core of the Earth?
We know about the Earth’s core because of what it is, what it did, and what it does. And as a result, all life on Earth can be grateful that the core exists. The core is the spherical region of the Earth that begins about halfway down to Earth’s center. Above the core and below a relatively thin crust is a very thick “mantle”. Although the core is far from us, and completely inaccessible to our touch, there are many indirect ways to learn about it. Earth’s gravity, for example, tells us how massive the Earth is (6 trillion trillion kilograms); that mass implies, given the Earth’s size, that each cubic meter of its volume contains, on average, about 5500 kilograms. But rocks on Earth’s surface (and in the mantle) are typically only half as dense as that; to boost the average, the core must be made of very dense stuff. Since iron is the most abundant of all heavy elements in the Universe, it is reasonable to propose that our core is mainly iron. There is other evidence in favor of an iro
