The Purest Soul in Physics
I have just finished reading Graham Farmelo’s “The Strangest Man, The Hidden Life of Paul Dirac, Mystic of the Atom.” It was a very enjoyable book for me. I read Schrodinger, Heisenberg and Bohr’s biographies in the early 1009’s – almost 20 years ago now. And I read Einstein and Feynman when I was younger still. Many of these people figure prominently in Dirac’s biography. Reading this book made me feel like I am spending time with old friends after a long absence. This is a very well written book – the writer is witty, and has a wry sense of humors. His way of putting things is very catchy – I have been posting some of these on Facebook as I read along. I have listed a few of the quotes at the end of this post.
While I had read every book Dirac has ever written, I had not understood his way of doing physics until reading this book. I could see the symptoms (results?) of it from the end product – especially the clarity of structure and the mathematical reasoning – when I read his book “Principles of Quantum Mechanics.” Now I understand better how he thought about it, and in what ways his way of doing physics was different from the other two inventors of quantum mechanics – Schrodinger and Heisenberg.
Pages 76 to 283 of the book cover the years from 1925 to 1935. The rest of the book covers the remaining 72 years of his life. The most fun parts of the book for me were these 10 years of his life. I plotted this graph of the number of weeks covered per page (on average) in each chapter of the book (on a logarithmic scale to show the “fine structure”). The x-axis shows the chapter numbers. The lower the point in the graph, the more detailed coverage a period of Dirac’s life gets. You can see the dip in chapters 8 and 9, this is when he was developing quantum mechanics, and the dip in chapter 18 covers his Nobel Prize ceremony in December 1933. The other exciting periods (dips in my graph) are chapter 11 – discovery of the Dirac equation, and chapters 15-17 – the development of quantum field theory. These are well covered in the book and are exhilarating to read.
Dirac helped develop quantum mechanics with Schrodinger and Heisenberg, then showed that their different formulations were mathematically equivalent. He showed the analogy of quantum mechanics with classical mechanics, and laid the foundation for Feynman’s 3rd formulation of quantum mechanics, invented the Dirac equation for the electron, helped develop quantum field theory and quantum electrodynamics, and was the first to describe particles as strings – a precursor to today’s string theory. But the boldest and most imaginative of his work is arguably the prediction of anti-matter. He did this at a time when only electrons and protons were known, and no one believed any other particles exist. Almost all the prominent physicists at the time said that he was wrong. But time would prove him right shortly. But like Einstein, he spent the later years of his life in search of a theory of reality that he would not find, as he ignored more and more what others were discovering in physics. And like Einstein, towards the end of his life, he considered himself a failure.
The title of this book comes from Neils Bohr who called him “the strangest man” to visit Bohr’s institute. Bohr has also called Dirac the “purest soul” in physics. And Einstein called him a genius! There is a good review of this book by the New York Times.
Quotes:
That first paper was a piece of academic throat-clearing.
He looked as if he had absconded from the captaincy of a herring trawler. [Neils Bohr]
He had not once asked after his family on his postcards, which each had the warmth of a stone.
He was an amateur scholar of the playwright Moliere, an accomplished interpreter of Chopin and the only member of the physics department to wear a dog collar. [George Lamaitre]
Dirac was listening to the dons reflecting on the pleasures of coining new a word, and, during a lull in the conversation, piped up with four words: “I invented the bra.” There was not a flicker of smile on his face. [Dirac notation]
When the wife of one of the Institute’s mathematicians asked Dirac how he was settling in at Princeton, he looked dumbfounded and leaned sharply away from her, as if she were a leak in a sewer. [Avoiding strangers]
