The year was 1925. Werner Heisenberg was just 23. A student of Niels Bohr in Copenhagen and now, of Max Born in Gottingen.
Ernst Mach, often called the Buddha of Science, was an Austrian physicist of the 19th century. Heisenberg embraced Mach's dictum that theories should avoid any concepts that cannot be observed, measured or verified. He avoided the concept of electron orbits, which cannot be observed.
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