  I study the physical meaning of Deformed, or Doubly, Special Relativity
(DSR). I argue that DSR could be physically relevant in a certain
large-distance limit. I consider a concrete physical effect: the gravitational
slowing down of time due to the gravitational potential well of a
massive-particle, and its effect on the dynamics of the particle itself. I
argue that this physical effect can survive in a limit in which gravitation and
quantum mechanics can be disregarded, and that taking it into account leads
directy to the Girelli-Livine DSR formalism. This provides a physical
interpretation to the corresponding 5d spacetime, and a concrete physical
derivation of DSR.
