卡文迪扭秤实验.jpg
The most important constant in Earth science is the mass of Earth. From this mass, scientists got the average density of Earth, which is about 5.5ton/m^3.
The average density of rocks near the top ground is about 3ton/m^3.
On the basis of these 2 densities, we got the current Earth model.
200 years ago, Mr Henry Cavendish got the mass of Earth in his experiment (Cavendish torsion balance experiment). The value he got is almost no different from current value.
We have to confess his experiment is too simple. Can we really believe he could actually get the mass of Earth with 4 lead balls and a torsion balance. If the mass of Earth is wrong, then a lot of theories in Earth science will collapse.
The mass of Earth is very important, we should make sure it's correct before we use it.
Please remember we still have no idea what the mass the The Himalays is.
Jin Guangnian