Mach (ernst mach, 1838? 19 16) Austrian-Czech physicist, psychologist and philosopher. Mach number and Mach band effect are named after them. Mach believes that the world is composed of a neutral "factor", and both material and spiritual things are the complex of this factor. The so-called elements are color, sound, pressure, space and time, which is what we usually call feeling. In his view, matter, movement and law are not objective things, but useful assumptions in people's lives; The law of causality is the product of human psychology and should be replaced by functional relationship. Therefore, the world is expressed as a functional relationship between elements, and science can only describe it but not explain it. The description should follow the "thinking economy principle", that is, the most perfect statement of empirical facts with the least amount of thinking. The idea of 1 mach played a certain role in Einstein's creation of general relativity. General relativity is a radical innovation of the basic concepts of classical mechanics. Mach emphasized that the law of science is a summary of observation, not a preconceived truth. He disagreed with the concepts of absolute space and absolute time contained in Newtonian mechanics. Einstein's theory of relativity proved his point. Mach 2 created an influential philosophy of science in the 20th century, holding that the laws of science are the summary of facts obtained from experiments, and these laws were created to make people understand complex data more easily. Therefore, the relationship between scientific laws and reality is not as close as that of thinking. Mach agrees with Boltzmann's philosophy, but opposes him and others who advocate the atomic theory of physics. Because the atom is too small to be observed directly, and there was no specious atomic model at that time; The hypothesis of atoms is not very reliable in Mach's view, probably because he thinks it is not economical enough. Mach directly influenced the logical positivism of Vienna School. Einstein praised him as a pioneer of relativity.