1. The problem statement, all variables and given/known data A pendulum clock is adjusted so that it keeps excellent time on the ground. The clock is brought to a mine of depth h below the ground and then raised a height h above the ground to see the differences. In which case is the error larger? 2. Relevant equations T = 2π √(L/g) L = length of the pendulum g = gravity on earths surface T = period g = GMm/Re2 G = gravitational constant Re = earths radius M = mass of earth m = mass of pendulum (negligible) 3. The attempt at a solution g1 = GMm/(Re - h) g2 = GMm/(Re+h) g1 = GMm/(Re - h) is for the pendulum underground. Plugging into the period equation gives T = 2π (Re - h) √(L/GMm) g2 = GMm/(Re+h) is for the pendulum above ground. Plugging into the period equation gives T = 2π (Re + h) √(L/GMm) It's obvious that the pendulum will tick slower below ground and faster above - but what about the error? I think that the errors would be the same. The question seems to imply that they are not though. I think there is a factor that I am not taking into account?