Inge Edler, a cardiologist, and Carl Hellmuth Hertz, a physicist, invented echocardiography at the University of Lund in Sweden in the early 1950s. They went to shipyards to study sonar, making the conceptual leap that if you can use ultrasound to see a ship five hundred meters away, maybe you can use it to see the heart, too, if only you could change the depth of penetration.
