Three cases of frictionless movement of a body are analyzed in a fictional
tunnel (1) drilled along the Earth axis, (2) connecting two points on the same meridian,
with the tunnel parallel with the Earth axis, and (3) connecting two points on the
same Earth parallel. The time necessary for passing the tunnel is 42.25 min for cases
(1) and (2). In case (3), the time is subtly shorter due to the effect of the centrifugal
force. In all three cases, the body moves in a periodic harmonic motion, with the maximum
speed achieved in the center of the tunnel.