The Speed of Light is Constant
Constancy of the speed of Light is incompatible with Galilean Transformations, because they predict that speed of light varies depending on the Inertial Reference Frame
Firstly, from an Electromagnetics perspective
can be derived from Maxwell’s Equations, assuming an Inertial Reference Frame Secondly, Galilean Transformations can be modified to account for a constant
in all frames of reference as follows, resulting in the Lorentz Transformations