TOEPLER

GERMANY (see also List of Individuals)

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7.9.1836 Brühl-Bonn/D - 6.3.1912 Dresden/D

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The scientific investigation of the nature of shock waves started 140 years ago with the advent of the Schlieren Method which was developed around 1860 by August Toepler. Whereas first observations were directed to heat and flow phenomena, Toepler immediately turned to air shock waves generated by electric sparks, and subjectively studied their propagation, reflection and refraction. His delay circuit in the microsecond regime allowed varying electrically delay times between spark generation, shock wave and second spark acting as a flash light source in his Schlieren setup. In 1870, Toepler together with Boltzmann extended the visualization to weak sound waves at the threshold of hearing. Toepler's pioneering Schlieren method stimulated Ernst Mach (1838-1916) and his collaborators to objectively investigate the nature of shock waves: They improved Toepler's time delay circuit, continued to study shock wave reflection, introduced shadowgraphy as a modification of the Schlieren method and photographed the propagation of shock waves.

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Toepler began his professional career as a chemist at the Agricultural College in Poppelsdorf on the Rhine. He completed his studies as a chemist at the Royal Technical Institute, Berlin in 1858. In 1859 he joined the department of agricultural chemistry and there was a lecturer in physics and chemistry from 1862 to 1864. He submitted his PhD thesis to the University of Jena on an efficient water pump. Toepler invented the Schlieren method around 1860 although the French physicist Foucault had published on a similar, yet distinctly different method to visualize density gradients in transparent objects of any state of aggregation. Toepler from the very beginning realized that the method was universally suitable in science and illustrated the versatility of his approach with practical examples.

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_{Anonymous (1910). Prof. Dr. August Toepler. Umschau 14: 500. P}

_{Krehl, P., Engemann, S. (1995). August Toepler - the first who visualized shock waves. Shock Waves 5: 1-18. P}

_{Poggendorff, J.C. (1898). Toepler, August Josef Ignatz. Biographisch-Literarisches Handwörterbuch 3: 1355-1356; 4: 1510; 5: 1261, 7a Sup.: 692. Barth: Leipzig, with bibliography.}

_{Toepler, A. (1864). Beobachtungen nach einer neuen optischen Methode. Cohen: Bonn. Toepler, A. (1866). Vibroskopische Beobachtungen über die Schwingungsphasen singender Flammen mit Benutzung des Schlierenapparates. Poggendorffs Annalen 128: 126-139.}