If you drop an object through a hole in the Earth stretching from the North Pole to the South Pole, it would oscillate back and forth about 17 times per daypic.twitter.com/crCfBFK2qp
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What if the hole goes not from a pole to pole, but like a general chord, i.e. straight segment through the sphere?
then it would almost immediately collide with one of the walls due to the relative velocities of the CM of earth and the ball
