Ernst Mach

1. Ernst Mach By Sarah Black

2. Background • In college, Mach studied and received a degree in physics, and after college he was employed as a lecturer for students in Vienna. • While there, he became interested in physiology and studied under Carl Ludwig.  They questioned the accepted truths of the field and instead began to emphasize the importance of applying the theories of physics and chemistry to biology.  • He thus became involved in a variety of classes, from physics to anatomy to psychology.  He was interested in and would contribute to all of these fields later in his life.  

3. The Doppler Effect • In Mach's time, the Doppler Effect was very new and controversial.  Two notable physicists challenged the theory, so Mach attempted to prove it experimentally.  • "A six-foot tube with a whistle at one end was mounted so as to rotate in a vertical plane. When the listener stood in the plane of the axis of rotation no changes in pitch could be heard. But if the observer stood in the plane of rotation, fluctuations in pitch that corresponded to the speed of rotation could be heard. The application of this work to Doppler effects with light remained controversial, but Mach is regarded as one of the first to realize the possibility of studying a star's spectrum to understand its movements" -- Stanford Encyclopedia of Philosophy

4. The Speed of Sound • In 1860, new gun and artillery technologies were developed.  • These new technologies had two very new effects: there was a second "boom" after the gun had been fired, and the wounds created by the bullets were far more devastating and resembled craters. • The reason for these new effects baffled many scientists, until Mach finally discovered that they were traveling faster than sound vibrations. • He investigated and, by 1885, had developed his ideas of supersonic motion. • He developed the Mach Number -- the ratio of the speed of sound in a given medium to the speed of the projectile.   • However, the speed of sound depends on the density of the given medium, so Mach Numbers change for every given situation.  So, this seemed to follow with his philosophical views and the theme of many of his contributions to science -- the Mach Number (Mach 1) is relatavistic.

5. Philosophy • Described his "awakening" to his philosophical ideas at age 15 after reading Kant's Prolegemena to any Future Metaphysics thus:  The book made at the time a powerful and ineffaceable impression upon me, the like of which I never afterwards experienced in any of my philosophical reading...On a bright summer day in the open air, the world with my ego suddenly appeared to me as one coherent mass of sensations, only more strongly coherent in the ego. Although the actual working out of this thought did not occur until a later period, yet this moment was decisive for my whole view. • Mach discovered that, in a sense, the human eye has a mind of its own. (Mach Bands) • We as humans are not perceiving reality directly, but instead are experiencing relations of stimuli.   • He believed that all of reality was dependent on one's sensations.  This indicated that different people, who all obviously have somewhat different sensations, being human, could perceive reality differently, according to these minor differences in their sensations.  • This led him to a direct philosophical contradiction with the absolutes of Newtonian physics.  He became one of Newton's first critics, and because of his relativistic philosophical views, he is also considered one of the first developers of the notions that Einstein would later investigate more fully.  

6. Mach Bands • Optical illusions! • Light or dark stripes are seen near the edges of images that have changing light gradients, even though they are not really there. • This reinforced Mach's idea that the human eye and brain do not perceive reality directly, but only  relations of stimuli. • Though he was never able to produce theories of relativity as Einstein did, the discovery of Mach bands furthered his ideological foundation for relativity that Einstein would later build upon. 

7. Mach was the first serious challenger to the widely accepted ideas of Isaac Newton.  His philosophical views on the world and his contributions to science all hinted at something relativistic.  This laid the foundation that would spark Einstein's interest years later and lead him to explore further and develop his own theories of relativity.