"Copenhagen" by Michael Frayn

Why did Werner Heisenberg visit Niels Bohr in Copenhagen in 1941? This three-hander play, first performed at the National Theatre in London, England in 1981, explores this meeting.

It was, of course, the height of the Second World War and both Nazi Germany and the Allies were trying to develop the Atom bomb. Heisenberg was working on nuclear fission in Germany, Bohr, with a mixed Jewish ancestry, was living in Denmark under Nazi occupation (he escaped to Sweden later in the war). Did Heisenberg ask Bohr whether it would be morally wrong for a physicist to create a bomb? When, later, he asked Speer for money to pursue his research he,  possibly deliberately, asked for less than he would need. 

The meeting was complicated by the fact that Bohr, one of the father's of the quantum atom, had been Heisenberg's mentor in the 1920s when quantum physics was experiencing revolutionary new ideas almost monthly. This was the period when Heisenberg, seeking solitude on a rocky island in Heligoland, invented the matrix-maths solution to quantum mechanics which would later be superseded by Schrodinger's wave mechanics. It was also when Heisenberg announced his Uncertainty Principle and when they together created the Copenhagen Interpretation of quantum mechanics.

The play mostly explores the relationships between the two men, and Bohr's wife Margarethe. Inevitably it involves some quantum physics. I used to teach Physics and I have always struggled to understand quantum mechanics (as did most of the scientists of the time, one of the reasons why the Copenhagen Interpretation was needed to explain what the mathematics and experiments 'meant'). So this play was always going to be difficult. There were times when it managed slightly over-simplified but nevertheless very clear explanations and there were times, for example when mentioning Complementarity, when it seemed to duck the issue entirely.

Here is my understanding of Complementarity. Heisenberg's Uncertainty Principle (better called his Indeterminacy Principle) is a mathematically proved conclusion that some system's (for example an electron) have paired properties (for an electron, its position is paired with its momentum) which are linked in that the more precisely you measure one of these properties the less precisely you are able to measure the other. In the play, Heisenberg explains it thus: “You can never know everything about the whereabouts of a particle, or anything else ... because we can't observe it without introducing some new element into the situation, an atom of water vapour for it to hit, or a piece of light - things which have an energy of their own, and which therefore have an effect on what they hit.” (Heisenberg, Act 2) But the principle is more fundamental, it isn't simply an experimental error that could somehow be circumvented but a property of nature. Nevertheless, the Uncertainty Principle is one aspect of Complementarity. Another is the fact that an electron can behave both as a wave or as a particle ('wave-particle duality') and which behaviour it adopts appears to be determined by the way it is being observed. Thus Complementarity seems to be the idea that there are two versions of truth and both are true although neither can be true at the same time.

Selected quotes:

• “If you don't know how things are today you certainly can't know how they're going to be tomorrow.” (Heisenberg, Act 2)
• “If it's Heisenberg at the centre of the universe, then the one bit of the universe that he can't see is Heisenberg.” (Margarethe, Act 2)
• “If you are doing something you have to concentrate on you can't also be thinking about doing it, and if you’re thinking about doing it then you can't actually be doing it.” (Margarethe, Act 2)

March 2025; 96 pages

Published by Methuen Drama in 1998

I saw this play at the Grove Theatre in Eastbourne on Wednesday 9th April 2025

This review was written by the author of Bally and Bro, Motherdarling  and The Kids of God

"Seven brief lessons on Physics" by Carlo Ravelli

This was the last book read by my dad before he died. He was an electronics engineer all his life. He worked on radar during World War II. Later he worked on the very first computers, meeting Alan Turing and Norbert Weiner. After that he researched radiocarbon dating, discovering that a fragment of wood found on Mount Ararat wasn't old enough to come from the Ark, and finally he worked as part of the team that created radio-controlled clocks.

In fewer than 80 pages, Rovelli talks about General Relativity, Quantum Physics, Cosmology, Particle Physics, Loop Quantum Physics, Thermodynamics and the nature of time, and Ourselves; I have taught Physics for 33 years and I have been a human for even longer and yet I still, repeatedly, learned fascinating things from this brilliant book. Plus it is superbly written and it tells so eloquently of the joys and challenges of being a scientist.

Just some of the brilliant insights from this wonderful little book.

• "the gravitational field is not diffused through space; the gravitational field is that space itself." (p 6) This is a triumph of Descartes over Newton: a vortex space rather than one filled with action-at-a-distance. Space undulates. :
• light curves round heavy objects
• time goes more quickly at altitude
• black holes exist
• "space cannot stand still; it must be expanding" (p 8)
• "space moves like the surface of the sea" (p 9)
• "Why does the periodic table have this particular structure, with these periods, and with the elements having these particular properties? The answer is that each element corresponds to one solution of the main equation of quantum mechanics." (p 15)
• "an electron is a series of jumps from one interaction to another. When nothing disturbs it, it is not in any particular place. It is not in a 'place' at all." (p 15)
• Loop Quantum Gravity proposes that space is quantised in very small linked rings: "Space is created by the linking of these individual quanta of gravity" (p 41) 
• "The passage of time ... is born in the world itself in the relationship between the quantum events that comprise the world and are themselves the source of time." (p 42). 
• "Our universe may have been born from a bounce in a prior phase, passing through an intermediate stage in which there was neither space nor time." (p 47)
• "How the gravitational field behaves when it heats up is still an unsolved problem. ... when heat is diffused to the gravitational field, time and space themselves must vibrate ... what is a vibrating time?" (p 56)
• "There is a detectable difference between the past and the future only when there is flow of heat. Heat is linked to probability; and probability in turn is linked to the fact that our interactions with the rest of the world do not register the fine details of reality ... due to the limitations of our consciousness we only perceive a blurred vision of the world, and live in time." (p 60)
• "The heat of black holes is a quantum effect upon an object, the black hole, which is gravitational in nature. ... The heat of black holes is like a Rosetta Stone of physics, written in a combination of three languages - Quantum, Gravitational and Thermodynamic - still awaiting decipherment in order to reveal the true nature of time." (p 62)
• "We are like an only child who on growing up realizes that the world does not revolve around them alone, as they thought when little. They must learn to be one among others. Mirrored by others, and by other things, we learn who we are." (p 65)
• "All things are continually interacting with each other, and in doing so each bears the traces of that with which it has interacted: and in this sense all things continuously exchange information about each other." (p 68)
• "It would be absurd to ask whether 'I' can do something different from what the whole complex of my neurons has decided: the two things ... are the same." (p 71)
• "Our reality is tears and laughter, gratitude and altruism, loyalty and betrayal, the past which haunts us and serenity." (p 74)
• "We are nature, in one of its innumerable and infinitely variable expressions." (p 74)
• 
  
• "And to the very last: doubt." (p 19)

What a way for my dad to end his reading career.

Magnificent. July 2017, 79 pages

"The Structure of Scientific Revolutions" by Thomas Kuhn

I first read this book, which was published in 1962, when I was studying the History and Philosophy of Science at Cambridge in 1987-8. It was a revolutionary thesis. This is the third edition (1996) which adds a postscript to respond to some of the issues that its original publication raised.

Science, Kuhn suggests, does not make steady progress closer and closer to the truth. Rather, it is oscillates between a 'normal' phase during which scientists solve problems and a 'revolutionary' phase when scientific certainties are thrown out of the window and a radically different understanding is born.

He calls the framework within which normal science is done a 'paradigm' and the revolution a 'paradigm shift'. There are many similarities between the way science develops during a paradigm shift and the way students learn if we assume the 'threshold concepts' theory of learning.

For example, In the 1880s physicists were complacently expecting that soon their classical models would be able to explain all that needed to be explained. They were refining them and making them a little more accurate. There were a few clouds on the horizon. Maxwell's equations suggested that light was an electromagnetic wave but no one could detect the 'aether', the postulated medium through which the e-m waves must ripple. The 'ultra-violet catastrophe' was the theoretical model of the atom which predicted that when you heated something up it should glow purple before it glowed red and at some stage it would radiate infinite amounts of energy in the ultra-violet part of the spectrum. And the photo-electric effect was an experiment which suggested that the energy of the electrons emitted from a surface when light was shone on it was not linked to the brightness of the incoming light. But these were blips and no-one seriously doubted that classical physics would soon be able to solve these problems.

In fact the failure to detect the aether was explained once Einstein had discovered his theory of Special Relativity with its bizarre claims that the speed of light was the fastest possible speed, the simultaneity was relative, that time slowed down as you got faster and that mass and energy were inter-convertible. The ultra-violet catastrophe gave rise to the weird world of Quantum Physics and the photoelectric effect was the key evidence for wave-particle duality which shortly led to de Broglie's claims that particles could behave like waves.

In some ways this makes Science a little like the pile of sand as explained in the book Ubiquity. As grain after grain is added to the pile it becomes more and more unstable. Sometimes there are slight slips; at other times there are near-catastrophic landslides.  Or science is like the punctuated equilibrium model of evolution as described in John Gribbin's brilliant Deep Simplicity. Most of the time evolution just contributes a little variation which make organisms marginally better adapted to their evolutionary niches. But when there is a major ecological catastrophe, evolution goes wild to fill the new ecological niches that have been created.

Kuhn writes with elegance and power. This is a very convincing thesis that had a major impact on the history and the philosophy of Science.

March 2015; 210 pages

"How to teach Quantum Physics to your dog" by Chad Orzel

A research scientist explains the basic principles of quantum physics to Emmy, a dog more concerned with chasing bunnies and evil squirrels.

I did some physics for my degree (which was before some of the stuff in this book was discovered) and I have taught A-level Physics for many years so I understand some of the basic principles. Nevertheless, Orzel gave me a better understanding of the Uncertainty Principle (certainly better than Michael Frayn's who confuses Uncertainty and Chaos Theory in his book The Human Touch) and its necessary consequences: zero-point energy, quantum tunnelling and virtual particles. He also writes very clearly about the difference between the Copenhagen and the Many-Worlds interpretations of the Schroedinger's Cat problem. I'm not sure I was convinced by the Quantum Zeno effect; I'm not sure I understood it properly. I might have to read through this section again. I certainly failed to understand how Bell's Theorem proves that Quantum Theory is a non-local model and how that in turn leads to quantum teleportation; I vaguely understood that quantum teleportation transmits states not particles but I got completely lost as to what this meant.

So I basically got the stuff I understood a bit before and failed to properly grasp the stuff that was new to me. That means that this is not the best explained Physics book I have ever read although, to be fair, it must be the most ambitious. It's like one of those Olympic dives where you have to assess both degree of difficulty and success in carrying out the dive. I guess this means it gets high but not perfect marks.

The dog? The dog helps in the way that ad breaks help in difficult documentaries. The dog gave my brain a chance to make a cup of mental tea and rest a while before coming back to full exertions. Lots of ads are funnier though.

July 2014; 265 pages

"50 Physics Ideas you really need to know" by Joanne Baker

Since I am a Physics teacher I am perhaps not the expected audience for this book.

There were some sections which I felt were rather poorly explained such as the Ideal Gas Law. And the section on Hooke's Law seemed to muddle other ideas in with it. And the book opens with Mach's principle which I have always understood to be essentially about the strange equivalence of gravitational and inertial mass whereas Baker is linking it to frames of reference.

So I was disappointed at the start.

But when it got into quantum theory and strong theory and cosmology I was much more interested and I believe I started learning things I hadn't know before. Now I was frustrated that there wasn't more detail in the explanations.

You can't win!

May 2010; 203 pages