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The Doppler Effect
Mach experimentally proved the Doppler Effect by using an apparatus with a whistle at one end that rotated on a vertical plane. When standing in the plane of axis no sound could be heard. However standing in the plane of rotation you could hear sound. The Doppler theory was discovered by Christian Doppler in 1841.
Pojman, Paul. “Ernst Mach.” Stanford Encyclopedia of Philosophy, Stanford University, 3 Mar. 2019, https://plato.stanford.edu/entries/ernst-mach/. -
Mach Bands
Mach believed that phenomena under scientific investigation could only be understood in terms of sensations, bringing us to his work on what became known as Mach Bands (an optical illusion triggered by edge detection in the visual system). He argued that this process does not all occur in the brain, which was significant in providing arguments against the current theories of of perception. Pojman, Stanford Encyclopedia of Philosophy, 3 Mar 2019, https://plato.stanford.edu/entries/ernst-mach/ -
Measurement of Sound Waves
In the years of 1873-1893, Ernst Mach created techniques to measure sound waves and wave propagation optically and photographically. Wave propagation is any bof the ways in which waves travel.
“Ernst Mach.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/biography/Ernst-Mach. -
The Mach Number
In 1877, Mach established the principles of supersonics and the ratio of the velocity of an object to the ratio of the velocity of the sound-which was deemed the 'Mach Number' which is extremely important because it is now used to denote the speed of a flying object in air medium. Essential to aerodynamics and aerospace engineers.
“Ernst Mach.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/biography/Ernst-Mach.