How do we know what the core of the Earth is made of?

Question

The deepest hole dug by humans is 12 km deep, how do we know what is there 2900 km deep?

In: 1

Answer 1

Simplified and partially misleading, but scientists just take a guess.

Partially misleading because before they guess they look at all the things we can see from the surface. Magnetic fields, volcano contents, seismic reactions, geologic surveys, strength of gravity, etc. And quite a few scientists talk about it for a while before they come up with a best guess.

But even nowadays the guess is occasionally updated! In the last 2 years, the common theory is making room for a slightly different core than it was before because of new data.