This is the book I wish I’d read before I read Carlo Rovelli. A very readable book that accesses archives of correspondence and records of conversations to make the emergence and codification of quantum theory into a warm, living thing. Almost gossipy, since Wolfgang Pauli was apparently universally considered to be a bit of a dick. And this made me laugh:
‘Princeton is a madhouse’ and ‘Einstein is completely cuckoo’, wrote Robert Oppenheimer. It was January 1935 and America’s leading home-grown theoretical physicist was 31.
It is, in fact, full of funny, human moments.
Paul Ehrenfest, sensing Einstein’s disbelief at the boldness of the Born-Heisenberg assertion that quantum mechanics was a closed theory, scribbled a note and passed it to him: ‘Don’t laugh! There is a special section in purgatory for professors of quantum theory, where they will be obliged to listen to lectures on classical physics ten hours every day.’
Also lots of instances of Pauli being amusingly awful to people. And, towards the back, Einstein finding new and interesting ways to fuck with Niels Bohr. He distrusted Bohr’s path to what became the Copenhagen Interpretation that froze quantum theory in place, for several reasons. You come to believe that one of those reasons was the mystic aura that Bohr took on.
According to the Copenhagen interpretation, a microphysical object has no intrinsic properties. An electron simply does not exist at any place until an observation or measurement is performed to locate it. It does not have a velocity or any other physical attribute until it is measured. In between measurements it is meaningless to ask what is the position or velocity of an electron. Since quantum mechanics says nothing about a physical reality that exists independently of the measuring equipment, only in the act of measurement does the electron become ‘real’. An unobserved electron does not exist.
And there it is in a nutshell. Kumar is excellent at showing the building blocks towards the Interpretation, the intellectual struggles and combat, and manages to always ground it in people and personalities. It’s a really fun read.