Cesium clock
When moving at high velocities, our perception of time is changed. Time moves slower. Events which are perceived to be simultaneous in one frame of reference, may not appear so from another frame of reference.
These slides present a (handwaving) overview of simultaneity and time dilation. The concepts of rest and moving frames are also introduced. Note that students are not required to recall the derivation of these equations.
kirrawee high physics 