## ABSTRACT

This chapter presents the basics of special relativity (SR) using spacetime diagrams. It discusses length contraction, the converse of time dilation, a phenomenon students tend to find more confusing than time dilation. Length contraction can be more readily demonstrated using the Lorentz transformation. Time dilation and length contraction are each a consequence of the relativity of simultaneity. Both effects emerge from a comparison of events measured from reference frames in relative motion. In a frame at rest relative to clocks and rods, measurements taken at the same location and at the same time, are different from measurements made in a frame in which clocks and rods are in motion, the measurements of which occur at different locations and at different times. Spacetime diagrams were used to illustrate the basic effects of SR, the “ingredients” used in descriptions of processes in space and time: time dilation, length contraction, simultaneity, the Doppler effect, and the velocity addition formula.