Abstract
Can we make a wave relive its past life ? The development of genuine " time-reversal mirrors ", in the field of ultrasound and electromagnetic waves, has enabled us to experimentally test the reversal of wave time in a wide variety of propagation media. These mirrors send a wave " in reverse " back to its original source, whatever the complexity of the propagation medium. This instrument not only sheds new light on the problem of the irreversibility of time in physics, it already has numerous applications : therapy, medical imaging, telecommunications, seismology, home automation, underwater acoustics.
