1. The problem statement, all variables and given/known data State two postulate that underlie the Special Theory of Relativity 3. The attempt at a solution From the notes I have from the lecturer. It says: The principle of relativity: The laws of physics must be the same in all inertial reference frame. The constancy of the speed of light: the speed of light must be the same in all inertial frames, regardless of the velocity of the observer or the velocity of the source emitting the light. My question is: For the first statement, how do I use an example to explain this? Because I'm not too sure about "the law of physics" really means.