Mach, Ernst (1838–1916)

Perhaps best known as a founder of the field of philosophy of science, in which he held a chair at the University of Vienna, the Austrian physicist, mathematician, philosopher, and science historian Ernst Mach also had a major influence on the emerging discipline of physiological psychology as well as on the development of physics itself. Albert Einstein would later credit Mach's critique of Newtonian concepts of absolute time and space as a decisive influence on the development of relativity theory.

A prominent element in Mach's thought is anti-mechanism, or the refusal to accept the doctrine that reality, including psychic phenomena, consists essentially of matter in motion. Along with naturalism, the principle that nothing exists beyond nature, it was largely Mach's embrace of Darwinian evolution that shaped his ideas. According to Mach, human culture, science, mind, and the senses have an evolutionary history, and indeed knowledge itself is a product of biological evolution. The earliest organisms responded to simple experience, thereby constructing an elementary picture of the primordial world; out of these first interactions, more complex understandings emerged, forming innate capacities in our remote ancestors that gradually developed through adaptation into increasingly elaborate constructions. The acquisition of memory permitted greater scope for awareness of spatiotemporal relations than what is given direcdy to the senses; much later on, memory was greatly extended by the capacity to communicate culturally. For Mach, scientific activity is not only the product of biological evolution; it also serves to advance the evolutionary process by giving rise to further adaptations as new data are confronted and understood. from among all available ideas, whether derived logically or from dreams or fantasy, scientists select those theories that best fit the data. In this way science proceeds, as does biological evolution, by a process of selection.

After earning a degree in physics, Mach undertook studies in anatomy, physiology, and chemistry at the medical school of the University of Vienna, where he later designed and taught a course in physics for medical students. from the pioneering work of Gustav Fechner, the founder of experimental psychology, Mach learned that there are quantifiable thresholds of perception, in other words, that sensations can be measured. Thus, a mathematical relationship exists between the psychological realm and the physical. Here lay the key to an experimental methodology that would produce, in studies by Mach and his contemporaries and up to the present day, significant advances in the psychology of perception, including color, sound, space, and time.

Today Mach's name is commonly associated with measurements of the velocity of sound. The development in the mid-19th century of more powerful guns and cannons had led to the production of bullets and shells that traveled at speeds greater than that of sound vibrations. Mach's research into supersonic motion, published in 1877, helped to establish the field of modern [Page 802]aerodynamics; the Mach number, still in constant use by engineers, is the ratio of the speed of a projectile to the speed of sound.

Mach's investigations into optical phenomena included the discovery of so-called Mach bands, an effect of contrast perception that creates the illusion of narrow light and dark bands at the boundaries of contrasting areas. Of greater significance is Mach's more fundamental insight that perception itself is always relational; that is, we perceive not the world itself, but relations between sensations. Our senses have evolved to perceive contrasts between stimuli. It is the interaction of a new experience with the residue of a previous experience, or the difference between successive sensations, that forms the basis of perception.

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