地心的英文：
geocentre

geocentric latitude [ longitude ]
地心纬度[经度]

The law of gravity
地心引力定律

It is deep in the bowels of the earth.
它在地心深处。

Anything that is dropped falls towards the centre of the earth because of the pull of gravity.
因为地心引力的缘故，掉下来的东西都向着地心方向坠落。

The fact that the gravity of the earth pulls everything towards the center of the earth explains many things.
地球引力把一切东西都吸向地心这一事实解释了许多现象。