A taste of Fabry and Perot's discoveries

One century ago, Fabry and Perot invented the interferometer which bears th eir name. The instrument was the culmination of two centuries of related wo rk on light and its interaction with both matter and itself. Today, hundred s of scientists throughout the world use this interferometer daily, perhaps without giving any thought to its ingenious inventors. Fabry and Perot bui lt the instrument, produced theoretical studies and developed methods of an alysis; but it was in using it for major scientific discoveries that the in strument would definitively remain synonymous with their names. They studie d physics, astronomy and geophysics and strongly contributed to narrowing t he gap between physics and astronomy so giving meaning to a new science eme rging at the beginning of the century, i.e. astrophysics. Their major works remain the determination of the temperature and kinematics of the Orion ne bula, the measurement of the gravitational redshift of light and a contribu tion to the standard metric system. Other discoveries of theirs are less kn own: the determination of the altitude and thicknesses of the atmospheric o zone layers; the calibration of the flux of the Moon, the Sun, stars and th e Milky Way; the improvement of stellar spectro-photometry; the development of electrometers to measure weak potentials; the elaboration of an atlas o f emission lines; the laboratory verification of the Doppler-Fizeau princip le and much more.