The main feature of this book is the emphasis on "practice". This approach, unusual in the relativistic literature, may be clarified by quoting some problems discussed in the text: - the analysis of rocket acceleration to relativistic velocities - the influence of gravitational fields on the accuracy of time measurements - the operation of optical rotation sensors - the evaluation of the Doppler spectrum produced by the linear (or ro- tional) motion of an antenna or scatterer - the use of the Cerenkov effect in the design of millimeter-wave power generators - the influence of the motion of a plasma on the transmission of electrom- netic waves through this medium. A correct solution of these (and analogous) problems requires the use of re­ lativistic principles. This remark remains valid even at low velocities, since first-order terms in (v/c) often playa fundamental role in the equations. The "applicational" approach used in the text should be acceptable to space engineers, nuclear engineers, electrical engineers, and more generally, ap­ plied physicists. Electrical engineers, in particular, are concerned with re­ lativity by way of the electrodynamics of moving bodies. This discipline is of decisive importance for power engineers, who are confronted with problems such as - the justification of a forcing function (-D~/Dt) in the circuit equation of a moving loop - a correct formulation of Maxwell's equations in rotating coordinate systems - the resolution of "sliding contact" paradoxes - a theoretically satisfying analysis of magnetic levitation systems.