On the pull
Question: If you could journey to the centre of the Earth, what would be the
sensation of gravity at various points on the way down, and at the centre?
Answer: This problem piqued the curiosity of no less a physicist than Isaac
Newton, who of course solved it in his Principia (Book 1, theorem 33).
If you are at the centre of the Earth you are pulled equally in all directions,
so you are in fact weightless. Higher up, at radius R from the centre,
Newton found that the attractions of the materials in the hollow…
