  A map is discussed that connects, in 1+1 dimensions, Galilei's relativity to
Einstein's special relativity. By means of this map it is possible to derive
special-relativistic formulas from the corresponding Galilean ones. Beyond
being interesting on its own, this map is also significant with respect to a
recent debate on the extension of relativistic symmetries to the Planck scale
(especially in the framework of the so-called doubly special relativity). The
map in fact provides an explicit example of how can be misleading to interpret
a mathematical correspondence between two relativity schemes as an argument in
favor of their physical equivalence.
