The Leibniz Institute for Astrophysics Potsdam is the successor of the Astrophysical Observatory Potsdam (AOP) founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. It was here that the American scientist Michelson carried out his experiment in 1881 related to measuring the rotation of the Earth. He assumed that a light beam sent in the same direction that the Earth was moving around the sun should be slowed a little by the aether wind. The proof should be given by measuring the speed of light "upwind and downwind". The device he built was a half-silvered mirror which would split the beam into two luminous machined brass arms running in perpendicular directions, each a meter long. To keep the device steady and void of any influence, he put it here in the cellar of the Astrophysical Observatory. Unfortunalty, he didn't manage to prove his theory.
Source: George Johnson, 2011, The ten most beautiful experiments & Wikipedia