Heisenberg Re-read

You should absolutely reread some books you got acquainted with during school days when being old and gray. The Bible and Goethe's Faust belong in this category, among many others. 

Up to now, I didn't count Werner Heisenberg's The Part and the Whole*, a book I read as a young physicist, but admittedly, I was mistaken.

*Titled relatively commonplace: Physics and Beyond in the English translation

This year my annual bicycle tour will take me to Franconia. Wulf, a former classmate and retired College teacher for German and biology, organizes these yearly trips. He does a marvelous job on these tours. While cycling during the day, we learn about birds and plants along the way. Wulf also prepares a reading for the evenings, always choosing an author and topic relevant to the region we are cycling.

Apparently, no famous regional authors were connected with Würzburg, but Werner Heisenberg, Nobel prize winner in physics, was born in this town in 1901. Since I had contributed to the evening entertainment on past bicycle tours too - although with mixed success - Wulf asked me whether I would be willing to read something Heisenberg wrote. 

To this end, I took his autobiography from the shelf and noticed it had been published in 1969, making it more than 40 years since I first read it.

What is comprehension in physics? Are we satisfied with understanding a phenomenon when it is possible to describe it by a mathematical formalism? Although such an understanding will allow us to do calculations and make predictions, the situation remains unsatisfactory. It turns out that terms and definitions of our daily experience will break down when we try to describe phenomena in the atomic world.

A cartoon by N. Harding shows Erwin Schrödinger clueless.
The equation named after him allows for calculating
discrete quantum states using wave mechanics.

One famous example is the physical description of light. While in the 17th Century, Christiaan Huygens' wave theory of light had beaten Isaac Newton's corpuscular theory, modern physics eventually englobed both ideas and speaks about a particle-wave duality. 

This is not a fight between scientists but an attempt to explain the physics of light with pictures taken from our everyday experiences. In subatomic physics, we need this complementary description. 

One of Heisenberg's leitmotifs is the problem of comprehension and that our language cannot describe the phenomena in atomic physics in an inherently consistent way. 

Following my 40-year experience in the subatomic world, it was fascinating to reread his book.

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