  It is well-known that the straight gravity tunnel between any two different
positions on a non-rotating Earth, which has uniform density, is traversable,
i.e., an object initially at rest will reach its destination through the
gravity tunnel in both directions. Moreover, the time taken to fall is always
constant. These facts are no longer true if rotation is allowed. The aim of
this note is to derive the necessary and sufficient condition for
traversability of straight gravity tunnels through a rotating physical body
with spherically symmetric gravitational field. Fall-through times are
expressed in a closed form for linear and constant gravitational fields. In
conclusion, these models are compared to numerically obtained data using the
internal structure of the Earth.
