Brass bullet in supersonic flight through air

Brass bullet in supersonic flight through air. This photograph, visualized by the schlieren method, was made by Ernst Mach in Prague in the winter of 1888. this print has been enlarged some thirty times, from a negative less than 5 mm in diameter. (The vertical White lines are fixed wires.) A year earlier Mach had published the first such photographs ever taken, showing the bow shock wave. Five years later he obtained quantitative measurements of the strength of the shock wave using the device developed by his physician son Ludwing that is now known as the Mach-Zehnder interferometer. Photographs from the archives of the Ernst-Mach-Institut, Freiburg i. Br., Germany, courtesy of A. Stilp.