This painting on a wall along the railway line on Burgemeester Reigerstraat shows Buys Ballot (1817-1890), professor at Utrecht University. In 1845, he was the first person to demonstrate the Doppler effect. You hear this effect when, for example, an ambulance or police car drives past: the sound of the siren seems lower once the vehicle has passed. The Austrian physicist Christian Doppler predicted this effect in 1842. Three years later, Buys Ballot decided to test the theory in an experiment. He arranged a group of horn-players in an open train carriage, which then travelled past a group of observers in Utrecht at high speed. This scene is depicted on the wall. It was painted by the Utrecht artists’ collective called De Strakke Hand.

> Discover this wall on Burgemeester Reigerstraat 9