How did scientists find out what layers exist under the Earth’s crust? How did they determine that Earth has a solid core?

Question

How did scientists find out what layers exist under the Earth’s crust? How did they determine that Earth has a solid core?

In: Earth Science

Answer 1

The first good evidence came when the Cavendish Experiment of 1797 measured the density of the earth at 5.4 times greater than water (the modern figure is 5.5). Now given that rocks generally have a density under 3, that meant the inside of the earth had to be different—much denser—than the crust we can see.