Erwin Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics. The philosophical issues raised by his 1935 “Schrödinger's cat” thought experiment perhaps remain his best known legacy, but the Schrödinger equation, which he formulated in 1926 to describe the quantum state of a system, is his most enduring achievement at a more technical level. It is celebrated as one of the most important achievements in 20th Century physics, and it revolutionized quantum mechanics and earned Schrödinger a share in the 1933 Nobel Prize in Physics.
Erwin Rudolf Josef Alexander Schrödinger was born on 12 August 1887 in Vienna, Austria (Austria-Hungary at that time). His father was an Austrian Catholic and his mother was an Austrian-English Lutheran, and Schrödinger grew up speaking German and English. He attended the Akademisches Gymnasium high school in Vienna from 1898 to 1905, and then studied at the University of Vienna between 1906 and 1910 under Franz Serafin Exner and Friedrich Hasenöhrl, as well as conducting experimental work with K.W.F. Kohlrausch. From an early age, Schrödinger was strongly influenced by the philosophy and Eastern religion of the Austrian philosopher Arthur Schopenhauer.
In 1911, Schrödinger became an assistant to Exner at the University of Vienna, earning his habilitation in 1914. During World War I, between 1914 and 1918, he participated in war work as a commissioned officer in the Austrian fortress artillery, and after the War, in 1920, he married Annemarie Bertel. The same year, he became the assistant to Max Wien at the University of Jena, and then quickly obtained a series of promotions, working in the universities of Stuttgart, Breslau and finally Zürich in 1921.
In 1926, Schrödinger published a remarkable series of four papers in the prestigious “Annalen der Physik” journal, which marked the central achievement of his career, and which were at once recognized as having great significance by the international physics community:
- a paper on wave mechanics, in which he derived what is now known as the Schrödinger equation, an equation that describes how the quantum state of a physical system changes over time, and giving the correct energy eigenvalues for a hydrogen-like atom with one electron. This paper has been universally celebrated as one of the most important achievements of the 20th Century, and created a revolution in quantum mechanics.
- a paper solving the quantum harmonic oscillator, the rigid rotor and the diatomic molecule, and giving a new derivation of the Schrödinger equation.
- a paper showing the equivalence of his approach to that of Heisenberg, and giving the treatment of the Stark effect (the shifting and splitting of spectral lines of atoms and molecules due to the presence of an external static electric field).
- a paper showing how to treat problems in which the system changes with time, as in scattering problems.
In 1927, Schrödinger succeeded Max Planck at the Friedrich Wilhelm University in Berlin, and his career seemed to be flourishing. However, when Adolf Hitler seized power in 1933, Schrödinger decided to leave Germany as a protest against the anti-Semitism of the Nazi regime, and he settled in Oxford, England, becoming a Fellow of Magdalen College at the University of Oxford. Soon after, he received the 1933 Nobel Prize in Physics, shared with Paul Dirac, “for the discovery of new productive forms of atomic theory”.
His position at Oxford, though, did not work out (it is likely that his unconventional personal life - he lived with two women, his wife, Annemarie Bertel, and his pregnant mistress, Hilde March - did not meet with acceptance in the proper Oxford of the 1930s). He was offered a permanent position at Princeton University in the United States in 1934, but he did not accept it, and again his lifestyle may have posed a problem. In the end, he took up a position at the University of Graz in Austria in 1936.
Somewhere in the midst of all these tenure issues, he found time for an extensive correspondence with his personal friend Albert Einstein and, as a result, he proposed in 1935 what has become known as the “Schrödinger's cat” thought experiment or paradox in order to illustrate the problem of the so-called “Copenhagen interpretation” of quantum mechanics (as propounded by Niels Bohr and Werner Heisenberg). The thought experiment proposed a scenario in which a cat was hidden in a sealed box, where the cat's life or death was dependent on the state of a particular sub-atomic particle. According to the Copenhagen interpretation, the cat remains both alive and dead until the box is opened, and it is the act of measurement that causes the calculated set of probabilities in the wave function to “collapse” to the value defined by the measurement.
In 1939, after the unification of Austria into Greater Germany, Schrödinger's known opposition to Nazism and his earlier flight from Germany led to threats and eventually to dismissal from his job at the University of Graz (despite his public recantation, which he later much regretted). He was under orders not to leave the country, but he and his wife managed to escape to Italy, and from there to visiting positions in Oxford University and Ghent University.
In 1940, he accepted an invitation to help establish an Institute for Advanced Studies in Dublin, Ireland, and he became the Director of the School for Theoretical Physics there. He remained in Dublin until his retirement in 1955, during which time he became a naturalized Irish citizen. He continued his scandalous involvements with students, however, fathering at least two children by two different Irish women.
During his time in Dublin, he wrote about 50 further publications on various topics, including his explorations of unified field theory. His important 1944 book “What is Life?” discussed the idea that life feeds on negative entropy, and introduced the concept of a complex molecule containing the genetic code for living organisms. Schrödinger's speculations about how genetic information might be stored in molecules gave James Watson and Francis Crick the inspiration to research the gene which led to the discovery of the DNA double-helix structure.
In 1956, Schrödinger returned to Vienna. He continued to court controversy, including his refusal to speak on nuclear energy at a major energy conference due to his skepticism about it (he gave a lecture on philosophy instead), and his turn, late in life, away from the wave-particle duality espoused by mainstream quantum mechanics in favour of the wave idea alone.
Schrödinger died of tuberculosis on 4 January 1961 in Vienna, at the age of 73.