A generic nonparaxial model for pulse envelopes is presented. Classic Schro¨dinger-type descriptions of
wave propagation have their origins in slowly-varying envelopes combined with a Galilean boost to the
local time frame. By abandoning these two simplifications, a picture of pulse evolution emerges in which
frame-of-reference considerations and space-time transformations take center stage. A wide range of
effects, analogous to those in special relativity, then follows for both linear and nonlinear systems. Explicit
demonstration is presented through exact bright and dark soliton pulse solutions
