Editing Ernst Mach (section)

=== Professional research ===
In 1864, Mach became professor of mathematics at the [[University of Graz]] after having declined a chair in surgery at the [[University of Salzburg]]. In 1866 he was appointed professor of physics. During this period, Mach continued his work in [[psycho-physics]] and in sensory perception. In 1867, he took the chair of experimental physics at the [[Charles University|Charles-Ferdinand University]], where he stayed for 28 years before returning to Vienna.<ref name="Reichenbach" /> In 1871 he was elected a member of the [[Royal Bohemian Society of Sciences]].<ref>{{cite book |editor1-last=Blackmore |editor1-first=John |title=Ernst Mach: A Deeper Look |date=1992 |publisher=Springer |page=34}}</ref>

Mach's main contribution to physics involved his description and photographs of spark shock-waves and then ballistic shock-waves. He described how when a bullet or shell moved faster than the speed of sound, it created a compression of air in front of it. Using [[schlieren photography]], he and his son Ludwig photographed the shadows of the invisible shock waves. During the early 1890s Ludwig invented a modification of the [[Jamin interferometer]] that allowed for much clearer photographs.<ref name="Reichenbach">{{cite journal |last1=Reichenbach |first1=H |title=Contributions of Ernst Mach to Fluid Mechanics |journal=Annual Review of Fluid Mechanics |date=January 1983 |volume=15 |issue=1 |pages=1–29 |doi=10.1146/annurev.fl.15.010183.000245 |bibcode=1983AnRFM..15....1R |url=https://www.annualreviews.org/doi/abs/10.1146/annurev.fl.15.010183.000245 |access-date=23 February 2023|issn=0066-4189}}</ref> But Mach also made many contributions to psychology and physiology, including his anticipation of [[Gestalt psychology|gestalt]] phenomena, his discovery of the [[oblique effect]] and of [[Mach bands]], an inhibition-influenced type of visual illusion, and especially his discovery of a [[Vestibular system|non-acoustic function]] of the inner ear that helps control human balance.

One of the best-known of Mach's ideas is the so-called [[Mach's principle|Mach principle]], the physical origin of inertia. This was never written down by Mach, but was given a graphic verbal form, attributed by [[Philipp Frank]] to Mach: "When the subway jerks, it's the fixed stars that throw you down."
<!--In this form its incompatibility with Einstein's conviction of the universal retardation of distant action is apparent. As an experimental physicist Mach tended to think that scientific theories were only provisional and had no lasting place in physics. This attitude made it hard for him to accept Einstein's special theory of relativity, especially since the second axiom seemed like an absolute of the kind Mach opposed, which was criticized in the preface to a posthumously published book on light which appeared in 1921.-->

[[File:Photography of bow shock waves around a brass bullet, 1888.jpg|thumb|upright=1.2|Ernst Mach's historic 1887 photograph ([[shadowgraph]]) of a bow shockwave around a supersonic bullet{{sfn|Anderson|1998|loc= Chapter 3|p=65}}]]

In 1900 Mach became the [[Godparent|godfather]] of the physicist [[Wolfgang Pauli|Wolfgang Ernst Pauli]], who was also named after him.<ref>{{cite book |last1=Gieser |first1=Suzanne |title=The Innermost Kernel Depth Psychology and Quantum Physics - Wolfgang Pauli's Dialogue with C.G. Jung |date=2005 |publisher=Springer |page=12}}</ref>

Mach was also well known for his philosophy, developed in close interplay with his science.{{efn|name=interdependency}} He defended a type of [[phenomenalism]], recognizing only [[sensation and perception psychology|sensations]] as real. That position seemed incompatible with the view of atoms and molecules as external, mind-independent things. After an 1897 lecture by [[Ludwig Boltzmann]] at the [[Austrian Academy of Sciences|Imperial Academy of Science]] in [[Vienna]], Mach said, "I don't believe that atoms exist!"{{sfn|Yourgrau|2005|p=}}
[[File:Mach, Ernst (1905).jpg|thumb|Ernst Mach in 1905]]
In 1898, Mach survived a paralytic stroke, and in 1901, he retired from the University of Vienna and was appointed to the upper chamber of the Austrian Parliament. On leaving Vienna in 1913, he moved to his son's home in [[Vaterstetten]], near [[Munich]], where he continued writing and corresponding until his death in 1916, one day after his 78th birthday.<ref name="Reichenbach"/>