Ernst Mach (1838-1916)
Knowledge and error flow from the same mental sources; only success can tell one from the other.
Ernst Waldfried Josef Wenzel Mach was an Austrian physicist and philosopher, noted for his contributions to physics such as the study of shock waves. The ratio of one's speed to that of sound is named the Mach number in his honour. As a philosopher of science, he was a major influence on logical positivism and American pragmatism. Through his criticism of Newton's theories of space and time, he foreshadowed Einstein's theory of relativity.
Ernst Waldfried Josef Wenzel Mach was born in Chrlice German: Chirlitz, Moravia then in the Austrian Empire, now part of Brno in the Czech Republic. His father, who had graduated from Charles-Ferdinand University in Prague, acted as tutor to the noble Brethon family in Zlín in eastern Moravia. His grandfather, Wenzl Lanhaus, an administrator of the Chirlitz estate, was also master builder of the streets there. His activities in that field later influenced the theoretical work of Ernst Mach. Some sources give Mach's birthplace as Tuřany German: Turas, now also part of Brno, the site of the Chirlitz registry-office. It was there that Ernst Mach was baptized by Peregrin Weiss. Mach later became a socialist and an atheist. His theory and life, though, was sometimes compared with Buddhism, namely by Heinrich Gomperz who addressed Mach as the "Buddha of Science" due to the phenomenalist approach of the "Ego" in his Analysis of Sensations.
Up to the age of 14, Mach received his education at home from his parents. He then entered a Gymnasium in Kroměříž German: Kremsier, where he studied for three years. In 1855 he became a student at the University of Vienna. There he studied physics and for one semester medical physiology, receiving his doctorate in physics in 1860 under Andreas von Ettingshausen with a thesis titled Über elektrische Ladungen und Induktion, and his habilitation the following year. His early work focused on the Doppler effect in optics and acoustics. In 1864, he took a job as Professor of Mathematics at the University of Graz, having turned down the position of a chair in surgery at the University of Salzburg to do so, and in 1866 he was appointed as Professor of Physics. During that period, Mach continued his work in psycho-physics and in sensory perception. In 1867, he took the chair of Experimental Physics at the Charles-Ferdinand University, where he stayed for 28 years before returning to Vienna.
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 were able to photograph the shadows of the invisible shock waves. During the early 1890s Ludwig was able to invent an interferometer which allowed for much clearer photographs. But Mach also made many contributions to psychology and physiology, including his anticipation of 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 non-acoustic function of the inner ear which helps control human balance.
One of the best-known of Mach's ideas is the so-called "Mach principle", concerning 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 himself, as, "When the subway jerks, it's the fixed stars that throw you down."
Mach also became well known for his philosophy, developed in close interplay with his science. Mach defended a type of phenomenalism recognizing only sensations as real. This position seemed incompatible with the view of atoms and molecules as external, mind-independent things. He famously declared, after an 1897 lecture by Ludwig Boltzmann at the Imperial Academy of Science in Vienna: "I don't believe that atoms exist!" From about 1908 to 1911 Mach's reluctance to acknowledge the reality of atoms was criticized by Max Planck as being incompatible with physics. Einstein's 1905 demonstration that the statistical fluctuations of atoms allowed measurement of their existence without direct individuated sensory evidence marked a turning point in the acceptance of atomic theory. Some of Mach's criticisms of Newton's position on space and time influenced Einstein, but later Einstein realized that Mach was basically opposed to Newton's philosophy and concluded that his physical criticism was not sound.
In 1898 Mach suffered from cardiac arrest 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.
Most of Mach's initial studies in the field of experimental physics concentrated on the interference, diffraction, polarization and refraction of light in different media under external influences. From there followed important explorations in the field of supersonic fluid mechanics. Mach and physicist-photographer Peter Salcher presented their paper on this subject in 1887; it correctly describes the sound effects observed during the supersonic motion of a projectile. They deduced and experimentally confirmed the existence of a shock wave of conical shape, with the projectile at the apex. The ratio of the speed of a fluid to the local speed of sound vp/vs is now called the Mach number. It is a critical parameter in the description of high-speed fluid movement in aerodynamics and hydrodynamics. Mach also contributed to cosmology the hypothesis known as Mach's principle.
Philosophy of science
From 1895 to 1901, Mach held a newly created chair for "the history and philosophy of the inductive sciences" at the University of Vienna. In his historico-philosophical studies, Mach developed a phenomenalistic philosophy of science which became influential in the 19th and 20th centuries. He originally saw scientific laws as summaries of experimental events, constructed for the purpose of making complex data comprehensible, but later emphasized mathematical functions as a more useful way to describe sensory appearances. Thus scientific laws while somewhat idealized have more to do with describing sensations than with reality as it exists beyond sensations.
The goal which it (physical science) has set itself is the simplest and most economical abstract expression of facts.
When the human mind, with its limited powers, attempts to mirror in itself the rich life of the world, of which it itself is only a small part, and which it can never hope to exhaust, it has every reason for proceeding economically.
In reality, the law always contains less than the fact itself, because it does not reproduce the fact as a whole but only in that aspect of it which is important for us, the rest being intentionally or from necessity omitted.
Mach's positivism also influenced many Russian Marxists, such as Alexander Bogdanov 1873–1928. In 1908, Lenin wrote a philosophical work, Materialism and Empirio-criticism published 1909, in which he criticized Machism and the views of "Russian Machists" His main criticisms were that Mach's philosophy led to solipsism and to the absurd conclusion that nature did not exist before humans. Lenin also cited in this work the concept of the 'ether', as the medium through which light waves propagated, and the concept of time as an absolute, concepts that were later proved wrong with further scientific developments.
Empirio-criticism is the term for the rigorously positivist and radically empiricist philosophy established by the German philosopher Richard Avenarius and further developed by Mach, which claims that all we can know is our sensations and that knowledge should be confined to pure experience.
In accordance with empirio-critical philosophy, Mach opposed Ludwig Boltzmann and others who proposed an atomic theory of physics. Since one cannot observe things as small as atoms directly, and since no atomic model at the time was consistent, the atomic hypothesis seemed to Mach to be unwarranted, and perhaps not sufficiently "economical". Mach had a direct influence on the Vienna Circle philosophers and the school of logical positivism in general.
To Mach are attributed a number of principles that distill his ideal of physical theorisation—what is now called "Machian physics":
- It should be based entirely on directly observable phenomena in line with his positivistic leanings
- It should completely eschew absolute space and time in favor of relative motion
- Any phenomena that would seem attributable to absolute space and time e.g., inertia and centrifugal force should instead be seen as emerging from the large scale distribution of matter in the universe.
The last is singled out, particularly by Albert Einstein, as "the" Mach's principle. Einstein cited it as one of the three principles underlying general relativity. In 1930, he stated that "it is justified to consider Mach as the precursor of the general theory of relativity", though Mach, before his death, would apparently reject Einstein's theory. Einstein was aware that his theories did not fulfill all Mach's principles, and no subsequent theory has either, despite considerable effort.
According to Alexander Riegler, Ernst Mach's work was a precursor to the influential perspective known as constructivism. Constructivism holds that all knowledge is constructed rather than received by the learner. He took an exceptionally non-dualist, phenomenological position. The founder of radical constructivism, von Glasersfeld, gave a nod to Mach as an ally.
In 1873, independently of each other Mach and the physiologist and physician Josef Breuer discovered how the sense of balance i.e., the perception of the head's imbalance functions, tracing its management by information which the brain receives from the movement of a fluid in the semicircular canals of the inner ear. That the sense of balance depended on the three semicircular canals was discovered in 1870 by the physiologist Friedrich Goltz, but Goltz did not discover how the balance-sensing apparatus functioned. Mach devised a swivel chair to enable him to test his theories, and Floyd Ratliff has suggested that this experiment may have paved the way to Mach's critique of a physical conception of absolute space and motion.
In the area of sensory perception, psychologists remember Mach for the optical illusion called Mach bands. The effect exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they contact one another, by triggering edge-detection in the human visual system.
More clearly than anyone before or since Mach made the distinction between what he called physiological specifically visual and geometrical spaces.
Mach's views on mediating structures inspired B. F. Skinner's strongly inductive position, which paralleled Mach's in the field of psychology.
In homage his name was given to:
- Mach, a lunar crater
- Mach bands, an optical illusion
- 3949 Mach, an asteroid
- Mach number, the unit for speed relative to the speed of sound
Mach's principal works in English:
- The Science of Mechanics. Translated by McCormack, Thomas J. 4th ed.. Chicago: The Open Court Publishing Co. 1919.
- "Photographische Fixirung der durch Projectile in der Luft eingeleiteten Vorgänge". Sitzungsber. Kaiserl. Akad. Wiss., Wien, Math.-Naturwiss. Cl. in German. 95 Abt. II: 764–780. 1887. with Peter Slacher
- The Analysis of Sensations 1897
- Popular Scientific Lectures 1895
- "Space and Geometry from the Point of View of Physical Inquiry". Monist. 14 1: 1–32. 1903. doi:10.5840/monist190314139. ISSN 0026-9662. with S.J.B. Sugden
- History and Root of the Principle of the Conservation of Energy 1911
- The Principles of Physical Optics 1926
- Knowledge and Error 1976
- Principles of the Theory of Heat 1986
- Fundamentals of the Theory of Movement Perception 2001
Mach reflection effects