Precision interferometry: from Michelson to gravitational waves

Full text: Exactly 75 years ago, Michelson built his wonderful optical 'Foucault pendulum', a Mach-Zehnder type interferometer with which he measured the rotation of the Earth. The experiment was based on his 1904 predictions, and was a very clever extension of Sagnac's interferometer. The results confirmed his early stationary ether model and relativity. The final precision achieved was an unprecedented 1/100 waves, corresponding to a relative change in length of the two 3100ft long optical paths, δL/L of about 6 x 10-12. The physical size of this interferometer was comparable to some current designs of gravitational wave interferometers, yet we are now building such interferometers with design strain sensitivities, δL/L of 10-22, while still making use of the same fundamental idea of looking at fringe shifts of optical radiation. This improvement in sensitivity of at least ten orders of magnitude is a most remarkable achievement, with most of the action having occurred since the invention of the laser. I shall trace this chain of intellectual achievements in experimental physics and technology, including the first laser gravitational wave interferometer, sensitivity δL/L of 10-14, and discuss the progress in interferometer design, which is enabling current attempts of gravitational wave detection and astronomy. The latest approach to gravitational wave interferometers, the ultimate limitations, and some of the ongoing contributions to this technology by the members of the Australian Consortium of Interferometric Gravitational Wave Astronomy (ACIGA) will be included