[en] State-of-the-art timing technique is used to determine the 'speed of light' in an upper level undergraduate laboratory experiment. In this experiment we use the correlated 511 keV photons from positron annihilation obtained from a 100 μ Ci Na-22 source. The photons were detected by two BaF₂ scintillation detectors and, after careful time calibration of the entire counting system, the prompt coincidence peaks were each recorded as a function of the position of one of the detectors. As a result, the 'speed of light' was determined to be 3.002(16)^*10¹⁰ cm s^-1, which is very close to the defined value of 2.99792^*10¹⁰ cm s^-1. This experiment demonstrates the utilization of various nuclear instrumentation and timing equipment. (author)