Week 3 (March 23)

Readings (55 pages total):

Chapter 6: The Prince of Duality (pp. 143-153)

Chapter 7: Spin Doctors (pp. 157-176)

Chapter 8: The Quantum Magician (pp. 177-200)

Please refer to the Reading Guide for details on readings and Points to Ponder (also below)

Chapter 6: The Prince of Duality – Points to ponder:

Middle of p. 146: “theoretical constructions of science have no value unless they are supported by facts”. Agree or disagree? What are “facts” and how would they be arrived at? Can you think of any theories not based on facts?

Chapter 7: Spin Doctors – Points to ponder

- - We now have an atom with stationary states, four quantum numbers for each electron, and an exclusion principle. Does this seem like a viable model for atoms? Why or why not?

- - What conclusions do you draw from the unhappy story of Ralph Kronig and electron spin (pp. 173–175)?

- - Would you have been able to work with Pauli or someone like him?

Chapter 8: The Quantum Magician – Points to ponder

Apply Heisenberg’s idea that only observables matter to the Bohr model of the atom. What do you think is observable, and what is not?

There’s a quote by Galileo which states that ”Mathematics is the language with which God has written the universe”, and one by Dirac that “God used beautiful mathematics in creating the world”. Johann Wolfgang von Goethe, revered for his literature such as Faust, also pursued some science, and said that “physics must clearly differentiate itself from mathematics”. Do you think that one can you have physics without math, or physics that’s only math?

Supplementary:

The Discovery of Electron Spin Lecture by one of the discoverers, S. A, Goudsmit (8 pages)

Werner Heisenberg Exhibit in AIP (American Institute of Physics)

P. A. M. Dirac Talk by biographer Graham Farmelo: Video (45:43)

Werner Heisenberg's breakthrough on Helgoland, in his own words (translated):

"When the first terms [of the calculations] seemed to accord with the energy principle, I became rather excited, and I began to make countless arithmetical errors. As a result, it was almost three o'clock in the morning before the final result of my computations lay before me. The energy principle had held for all the terms, and I could no longer doubt the mathematical consistency and coherence of the kind of quantum mechanics to which my calculations pointed. At first, I was deeply alarmed. I had the feeling that, through the surface of the atomic phenomena, I was looking at a strangely beautiful interior, and felt almost giddy at the thought that I now had to probe this wealth of mathematical structures nature had so generously spread out before me. I was far too excited to sleep,and so, as a new day dawned, I made for the southern tip of the island, where I had been longing to climb a rock jutting out into the sea. "

– Werner Heisenberg: Physics and Beyond – Encounters and Conversations

(Der Teil und das Ganze – Gespräche im Umkreis der Atomphysik)

Werner Heisenberg (1901 - 1976)

The Memorial Inscription

"In June of 1925 the 23-year-old Werner Heisenberg succeeded here on Helgoland with the breakthrough in the formulation of quantum mechanics, the underlying theory of the laws of nature at the atomic level, which profoundly influenced human thought far beyond physics."

(My translation of the inscription)

Helgoland in the North Sea

Werner Heisenberg:

“The existing scientific concepts cover always only a very limited part of reality, and the other part that has not yet been understood is infinite. Whenever we proceed from the known into the unknown we may hope to understand, but we may have to learn at the same time a new meaning of the word ‘understanding’.”

1955-56 Griffolds lectures, University of St. Andrews, Scotland, later published in the book “Physics and Philosophy: The Revolution in Modern Science“ (1958).

Louis de Broglie

Interview with Louis de Broglie, 1967 (French with English Subtitles): YouTube video (13:44)

Updated Jan. 12, 2023

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