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**Erwin Schrödinger proved that electrons could have the properties of either waves or particles, but are neither the one nor the other – a discovery that revolutionized physics.**

In the fall of 1921, Erwin Schrödinger was appointed to the chair for theoretical physics at the University of Zurich, a position that had been vacant since 1914. At that time no one imagined that six years later he would leave the University and the city hailed as a genius by luminary figures such as Albert Einstein and Max Planck, and celebrated as a star.

While at the University, Erwin Schrödinger revolutionized physics by creating a new atomic theory, a scientific breakthrough he achieved in the winter of 1925/26. In the summer semester of 1925, Erwin Schrödinger had read the doctoral thesis of a young Frenchman, Louis de Broglie, who proposed that matter – such as electrons – also possessed wave properties. This contradicted the prevailing opinion of leading physicists of the time, who assumed that electrons were particles.

Schrödinger focused intensively on Broglie’s proposition that all matter has wave properties. What were the properties of such waves of matter? Schrödinger spent Christmas and New Year 1925/26 studying the matter while on holiday in Arosa. This vacation was the beginning of his annus mirabilis, a phase, lasting some twelve months, of concentrated, creative work.

These efforts resulted in his first article, “Quantisierung als Eigenwertproblem. Erste Mitteilung” (Quantization as a problem of proper values, part one), which he sent to the Annalen der Physik on 26 January 1926. In this paper, he first formulated his famous wave equation, which has gone down in the annals of physics as the “Schrödinger equation.” The wave equation makes it possible to calculate the energy levels of electrons in an atom, thus solving one of the great problems in quantum physics.

After Schrödinger’s wave equation, nothing in the world of physics was the same again. The dispute as to whether quantum objects such as electrons, atoms or molecules were waves or particles was settled. In a surprising fashion, however: Schrödinger demonstrated that electrons could have the properties of either waves or particles, but are neither the one nor the other; their state can be calculated only with a degree of probability. For this discovery, Erwin Schrödinger was awarded the 1933 Nobel Prize in Physics.