Reconstruction of the Michelson Experiment 1881

The Potsdam Michelson Experiment 1881 In 1880 Albert Abraham Michelson won a stipendia (US Navy) for a sabbatical in Europe. He worked in interferometry at the Physics Institute in Berlin, headed by Helmholtz. During this time an „Ether“ was assumed as the carrier medium for the propagation of light.

The rotating Earth orbiting the Sun „Ether wind“ 30 km/s

During his time in Berlin, the idea appeared to try an experimental determination of the „Ether wind“ using highly precise interferometry. Michelson preestimated the magnitude of the expected interferential effect as just detectable. The needed instrumentation has been manufactured by Schmidt&Hænsch Berlin. A first attempt in the cellar of the Physics Institute´in January 1881 failed due to vibrations, caused by „too dense traffic“ along the „Reichstagsufer“ in Berlin. A first evaluable measurement was conducted in the basement vault beneath the East tower of the Astronomical Observatory Potsdam.

Experimental Assumptions Assumption: „Ether“ is fixed in relation to the Sun.  seasonal differences in the direction of the „incident Ether flow“  daytime differences (between parallel and orthogonal) Assumption: Galilei‘s Transformation is unlimited valid  all velocities are added universly  different light propagation dependend on daytime resp. the angular orientation of the instrumentation to the „Ether wind“

Deflected beam  perpendicular to the Ether arrives earlier Expected Result Deflected beam  perpendicular to the Ether arrives earlier

Deflected beam  parallel to the Ether arrives later Expected Result Deflected beam  parallel to the Ether arrives later

Deflected beam  perpendicular to the Ether arrives earlier Expected Result Deflected beam  perpendicular to the Ether arrives earlier

The observed interferential image Expected Result The observed interferential image Deflected beam  parallel to the Ether arrives later should be changed by Earth‘ rotation resp. turning the entire Instrument

Observed Result Herewith the Michelson Experiment as the ´most import Zero-Result´ of the classic experimental physics became an imprtant basis of the Special Relativity Theory. The expected shift of the interferential „frings“ could not be observed. Michelson concluded: „The hypothesis of an fixed „Ether“ is errornous.“ Not before Einstein postulated in 1905: „... light is always propagated in the vacuum with a certain velocity V independent from the relative motion of the emitting body...“ this result could be interpreted correctly. An „Ether“ was no more necessary.

Quo vadis, Michelson? Michelson 1881 and Michelson-Morley 2005 1881 Δv = ±10 km·s-1 Δv = ±10 m·s-1

In 2005 a group of physicist won the Nobel prize ...for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique...