Lets say that you have a valley 6 miles deep. Next to it, is a mountain 6 miles high. Assume that you have a measuring device that is capable of measuring infinitesimal differences in gravity. The entire area is made of the same material, from the top of the mountain right down to the core of the earth. Assume that all other conditions are also equal. You take one measuring device and place it in the bottom of the valley, and you place another measuring device at the top of the mountain. Would gravity measure more at the top of the mountain or the bottom of the valley? Or would it be exactly the same at both places?