Einstein and Heisenberg - Konrad Kleinknecht ***

The debates between Einstein and Niels Bohr over quantum physics are well documented, as are the letters that Einstein exchanged with Max Born on the subject, from which many of Einstein's famous quotes are taken. However, less has been said about the opposing views of Einstein and Werner Heisenberg. To make matters more interesting, though both were German physicists, while Einstein would leave Germany forever as a result of the rise of the Nazis, Heisenberg would continue to thrive under the Nazi regime, working on the failed attempt to create a German nuclear weapon.

With this interesting background in mind, I was looking forward to reading Konrad Kleinknecht's book, subtitled 'the controversy over quantum physics'. There is no doubt that Kleinknecht, a professor of experimental physics, knows the science, and there is some interesting material on the development of quantum physics, particularly around the distinction of approach between more philosophical types like Bohr and the more practically-minded approach of some of the other physicists working in the field.

One problem with the book is the way that the timeline jumps around. Heisenberg was a generation younger than Einstein, so the attempt to develop pictures of them in parallel results in a fractured view of the history. For example, we go straight from what Heisenberg was doing in 1921 to Einstein's annus mirabilis of 1905. Later on, it's almost as if we transition to a different book that has been added on to the rest. From chapter 5 onwards there was a significant amount of material that has already been mentioned in earlier chapters. This book would benefit from a good edit.

Another issue is that there is variability in the accuracy of content. One of the good things about Kleinknecht's approach is that he gives us interesting background material, such as a photograph of the Einstein home in Munich and the original manuscript of the uncertainty principle. These parts feel well-researched and with the precision we would expect from an academic. But then, in describing Einstein's paper 'Does the inertia of a body depend on its energy content', Kleinknecht tells us the form in which Einstein presented the information from his most famous equation, but uses E and c, where Einstein used L and V. It would have been both interesting and more accurate to mention this.

Kleinknecht goes on to say 'And further, he writes: "An appreciable decrease in the mass of the radium must result. This observation is amusing and intriguing; but whether the Lord God laughed about it, and has been leading me around by the nose is something I cannot know."' The trouble is, in producing this equation, Einstein wasn't talking about radium, and the closest he comes in the paper is to say 'Perhaps it will prove possible to test this theory using bodies whose energy content is variable to a high degree (e.g. salts of radium).' While Einstein may have written the remarks attributed to him by Kleinknecht, it wasn't in this paper.

A couple of other examples. The Big Bang is said to be 13.8 billion years ago in one part of the book and 13.2 billion in another. And the historical context is way out when we are told that the idea of nuclear fusion in the stars 'was recognised by Hans Albrecht Bethe and Carl-Friedrich von Weizsäcker in 1937' when Eddington suggested fusion was the power source of stars in 1920. There is something of a mix of over-simplification of the history and lack of explanation of technical complexities. For example, on the over-simplification side, there is no mention of Hilbert's attempt to beat Einstein in coming out with a general relativity paper first, and the description of Heisenberg's role in the war would have benefited from content from the transcripts of the secretly recorded Farm House discussions after the war. A good example of the over-use of technical terms without sufficient explanation was when we are told 'In two communications to the Annalen Der Physik on the quantisation as an Eigen-value problem, Schrödinger extended this conception by showing one could construe the Bohr electron orbits in the atom by requiring the the length of the orbit be a [sic] integer multiple of the wavelength, that is, that the electron waves fit within the orbit.' This could do with considerable unpacking in a book that is supposed to be accessible to non-physicists.

Overall, then, there is some good content here, but this book really needs a thorough edit to put it into final form.

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Review by Brian Clegg