  The parallel globe is an old, very simple and ingenious device that, when
systematically employed in astronomy classes, becomes a teaching tool with
great potential. Properly oriented according to the local meridian, this
instrument allows us to follow the shadows in any region of the Earth that is
illuminated by the Sun, as well as offering a clear view of the terminator, the
fast-moving grey line that divides the day from the night on our planet. With
knowledge of the shadows, it is possible to estimate the latitude of a site and
to infer local solar time anywhere in the planet's sunlit hemisphere.
Furthermore, by using the parallel globe we may understand simply the existence
of regions in which objects sometimes do not cast shadows, and also other
regions which, on the contrary, sometimes become "long-shadow" countries. In
this work, we first review the device and the basics of its assembly and
operation. In the second part, we describe in detail some activities targeted
to facilitate its use in the classroom, which our research group has been
developing during teacher training workshops.
