Tag Archives: Manjit Kumar

The Witches’ Sabbath

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Manjit Kumar.JPGThis week’s guest blogger is Manjit Kumar. Manjit’s book, Quantum: Einstein, Bohr and the Great Debate,is about the nature of reality, and was shortlisted for the 2009 BBC Samuel Johnson Prize for Non-fiction. He writes and reviews regularly for a variety of publications, including The Guardian, The Independent, The Times and the New Scientist. He used to edit a journal called Prometheus that covers the arts and sciences, and he was also the consulting science editor at UK Wired.

The first Solvay Conference on Physics, held in Brussels

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Left-to right standing – Robert Goldschmidt, Max Planck, Heinrich Rubens, Arnold Sommerfeld, Frederick Lindemann, Maurice de Broglie, Martin Knudsen, Fritz Hasenöhrl, Georges Hostelet, Edouard Herzen, James Hopwood Jeans, Ernest Rutherford, Heike Kamerlingh Onnes, Albert Einstein, Paul Langevin. Seated – Walther Nernst, Marcel Brillouin, Ernest Solvay, Hendrik Lorentz, Emil Warburg, Jean-Baptiste Perrin (reading), Wilhelm Wien (upright), Marie Curie, Henri Poincaré.

In June 1911 Albert Einstein was a professor of physics in Prague when he received a letter and an invitation from a wealthy Belgium industrialist. Ernst Solvay, who had made a substantial fortune by revolutionizing the manufacture of sodium carbonate, offered to pay him one thousand francs if he agreed to attend a ‘Scientific Congress’ to be held in Brussels from 29 October to 4 November. He would be one of a select group of twenty-two physicists from Holland, France, England, Germany, Austria, and Denmark being convened to discuss ‘current questions concerning the molecular and kinetic theories’. Max Planck, Ernest Rutherford, Henri Poincare, Hendrik Lorentz and Marie Curie were among those invited. It was the first international meeting devoted to a specific agenda in contemporary physics: the quantum.

Planck and Einstein were among the eight asked to prepare reports on a particular topic. To be written in French, German, or English they were to be sent out to the participants before the meeting and serve as the starting point for discussion during the planned sessions. Planck would discuss his blackbody radiation theory, while Einstein had been assigned his quantum theory of specific heat. Accorded the honour of giving the final talk, there was no room on the proposed agenda for a discussion of his light-quanta – better known these days as photons.

‘I find the whole undertaking extremely attractive,’ Einstein wrote to Walter Nernst, ‘and there is little doubt in my mind that you are its heart and soul.’ Nernst with his love of motorcars was more flamboyant than the staid Planck, but was just as highly respected – in 1920 he was awarded the Nobel Prize for chemistry for what became known as the third law of thermodynamics. A decade earlier, in 1910 he was convinced that the time was ripe to launch a cooperative effort to try and get to grips with the quantum he saw as nothing more than a ‘rule with most curious, indeed grotesque properties’. Nernst put the idea to Planck who replied that such ‘a conference will be more successful if you wait until more factual material is available’. Planck argued that ‘a conscious need for reform, which would motivate’ scientists to attend the congress was shared by ‘hardly half of the participants’ envisaged by Nernst. Planck was sceptical that the ‘older’ generation would attend or would ‘ever be enthusiastic’. He advised: ‘Let one or even better two years pass by, and then it will be evident that the gap in theory which now starts to split open will widen more and more, and eventually those still remote will be sucked into it. I do not believe that one can hasten such processes significantly, the thing must and will take its course; and if you then initiate such a conference, a hundred times more eyes will be turned to it and, more importantly, it will take place, which I doubt for the present.’

Undeterred by Planck’s response, Nernst convinced Solvay to finance the conference. Interested in physics, and hoping to address the delegates about his own ideas on matter and energy, Solvay spared no expense as he booked the Hotel Metropole. In its luxurious surrounding, with all their needs catered for, Einstein and colleagues spent five days talking about the quantum and, as Lorentz said in his opening remarks, the reasons why the ‘old theories do not have the power to penetrate the darkness that surrounds us on all sides’. However, he continued, that the ‘beautiful hypothesis of the energy elements, which was first formulated by Planck and then extended to many domains by Einstein, Nernst, and others’ had opened unexpected perspectives, and ‘even those who regard it with a certain misgiving must recognize its importance and fruitfulness.’

‘We all agree that the so-called quantum theory of today, although a useful device, is not a theory in the usual sense of the word, in any case not a theory that can be developed coherently at present,’ said Einstein. ‘On the other hand, it has been shown that classical mechanics…cannot be considered a generally useful scheme for the theoretical representation of all physical phenomena.’ Whatever slim hopes he abhorred for progress at what he called ‘the Witches’ Sabbath’, Einstein returned to Prague disappointed at having learnt nothing new. ‘The h-disease looks ever more hopeless,’ he wrote to Lorentz after the conference.

Nevertheless, Einstein had enjoyed getting to know some of the other ‘witches’. Marie Curie, whom he found to be ‘unpretentious’, appreciated ‘the clearness of his mind, the shrewdness with which he marshalled his facts and the depth of his knowledge’. During the congress it was announced that she had been awarded the Nobel Prize for chemistry. She had become the first scientist to win two, having already won the Physics prize in 1903. It was a tremendous achievement that was overshadowed by the scandal that broke around her during the congress. The French press had learned that she was having an affair with a married French physicist. Paul Langevin was another delegate at the congress and the papers were full of stories that the pair had eloped. Einstein, who had seen no signs of a special relationship between the two, dismissed the newspaper reports as rubbish. Despite her ‘sparkling intelligence’, he thought Curie was ‘not attractive enough to represent a danger to anyone’.

The Solvay Congress was the end of the beginning for the quantum. It dawned on physicists that it was here to stay and they were still struggling to learn how to live with it. When the proceedings of the conference were published it brought to the attention of others, not yet aware or engaged in the struggle, what an immense challenge it was to successfully do so. The quantum would be the focus of attention at the fifth Solvay conference in 1927. What happened in the intervening years is, as they say, history.

The Meeting of Minds

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Manjit Kumar.JPGThis week’s guest blogger is Manjit Kumar. Manjit’s book_, Quantum: Einstein, Bohr and the Great Debate, is about the nature of reality, and was shortlisted for the 2009 BBC Samuel Johnson Prize for Non-fiction. He writes and reviews regularly for a variety of publications, including The Guardian, The Independent, The Times and the New Scientist. He used to edit a journal called Prometheus that covers the arts and sciences, and he was also the consulting science editor at UK Wired._

I first saw the photograph of those gathered at the fifth Solvay conference, which was held in Brussels from 24 to 29 October 1927, in a biography of Albert Einstein. This was in 1979, when I was just 16. I wondered what brought these people together, and soon learned that the picture included most of the key players involved in the discovery of the quantum, and the subsequent development of quantum physics. With 17 of the 29 invited eventually earning a Nobel Prize, the conference was one of the most spectacular meetings of minds ever held.

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When I was 18, I was given a print of the above photograph as a present. Many years later I began to think about it as a possible starting point for a book about the quantum. In the photograph there are nine seated in the front row. Eight men, and one woman; six have Nobel Prizes in either physics or chemistry. The woman has two, one for physics, awarded in 1903, and another for chemistry, awarded in 1911. It could only be Marie Curie. In the centre, the place of honour, sits Albert Einstein. Looking straight ahead, gripping the chair with his right hand, he seems ill at ease. Is it the winged collar and tie that are causing him discomfort, or is it what he has heard during the preceding week? At the end of the second row, on the right, is Niels Bohr, looking relaxed with a half-whimsical smile. It had been a good conference for him. Nevertheless, Bohr would be returning to Denmark disappointed that he had failed to convince Einstein to adopt his Copenhagen interpretation_ of what quantum mechanics revealed about the nature of reality.

Instead of yielding, Einstein had spent the week attempting to show that quantum mechanics was inconsistent, that Bohr’s ‘Copenhagen interpretation’ was flawed. Einstein said years later that:

This theory reminds me a little of the system of delusions of an exceedingly intelligent paranoic, concocted of incoherent elements of thoughts.

It was Max Planck, sitting on Marie Curie’s right, holding his hat and cigar, who discovered the quantum. In 1900 he was forced to accept that the energy of light, and all other forms of electromagnetic radiation, could only be emitted or absorbed by matter in bits, bundled up in various sizes. ‘Quantum’ was the name Planck gave to an individual packet of energy, with ‘quanta’ being the plural. The quantum of energy was a radical break with the long-established idea that energy was emitted or absorbed continuously, like water flowing from a tap. In the everyday world of the macroscopic, where the physics of Newton ruled supreme, water could drip from a tap, but energy was not exchanged in droplets of varying size. However, the atomic and subatomic level of reality was the domain of the quantum.

Bohr discovered that the energy of an electron inside an atom was ‘quantised’; it could possess only certain amounts of energy and not others. The same was true of other physical properties, as the microscopic realm was found to be lumpy and discontinuous. Not some shrunken version of the large-scale world that we humans inhabit, where physical properties vary smoothly and continuously, where going from A to C means passing through B. Quantum physics, however, revealed that an electron in an atom can be in one place, and then, as if by magic, reappear in another without ever being anywhere in between, by emitting or absorbing a quantum of energy.

By the early 1920s, it had long been apparent that the advance of quantum physics on an ad hoc, piecemeal basis, had left it without solid foundations or a logical structure. Out of this state of confusion and crisis emerged a bold new theory; known as quantum mechanics_, with Werner Heisenberg and Erwin Schrödinger,Schr%C3%B6dinger third and sixth from the right in the back row, leading the way. In 1927 Heisenberg made a discovery. It was so at odds with common sense that he initially struggled to grasp its significance. The uncertainty principle said that if you want to know the exact velocity of a particle, then you cannot know its exact location, and vice versa.

Bohr believed he knew how to interpret the equations of quantum mechanics; what the theory was saying about the nature of reality. Questions about cause and effect, or whether the moon exists when no one is looking at it, had been the preserve of philosophers since the time of Plato and Aristotle. However, after the emergence of quantum mechanics they were being discussed by the twentieth century’s greatest physicists.

The debate that began between Einstein and Bohr at the Solvay conference in 1927, raised issues that continue to preoccupy many physicists and philosophers to this day; what is the nature of reality, and what kind of description of reality should be regarded as meaningful?

‘No more profound intellectual debate has ever been conducted’, claimed the scientist and novelist CP Snow. ‘_It is a pity that the debate, because of its nature, can’t be common currency_.’

When Einstein and Bohr first met in Berlin in 1920, each found an intellectual sparring partner who would, without bitterness or rancour, push and prod the other into refining and sharpening his thinking about the quantum. ‘It was a heroic time,’ recalled Robert Oppenheimer, who was a student in the 1920s. ‘It was a period of patient work in the laboratory, of crucial experiments and daring action, of many false starts and many untenable conjectures. It was a time of earnest correspondence and hurried conferences, of debate, criticism and brilliant mathematical improvisation. For those who participated it was a time of creation.’

Planck, Einstein, Bohr, Heisenberg, Schrodinger, Born, Pauli, De Broglie, Dirac, the leading lights of the quantum revolution, are all there in that picture.