Modern Mind: An Intellectual History of the 20th Century (5 page)

Mendel’s theories were simple and, to many scientists, beautiful. Their sheer originality meant that almost anybody who got involved in the field had a chance to make new discoveries. And that is what happened. As Ernst Mayr has written in
The Growth of Biological Thought,
‘The rate at which the new findings of genetics occurred after 1900 is almost without parallel in the history of science.’
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And so, before the fledgling century was six months old, it had produced
Mendelism, underpinning Darwinism, and Freudianism, both systems that presented an understanding of man in a completely different way. They had other things in common, too. Both were scientific ideas, or were presented as such, and both involved the identification of forces or entities that were hidden, inaccessible to the human eye. As such they shared these characteristics with viruses, which had been identified only two years earlier, when Friedrich Löffler and Paul Frosch had shown that foot-and-mouth disease had a viral origin. There was nothing especially new in the fact that these forces were hidden. The invention of the telescope and the microscope, the discovery of radio waves and bacteria, had introduced people to the idea that many elements of nature were beyond the normal range of the human eye or ear. What was important about Freudianism, and Mendelism, was that these discoveries appeared to be fundamental, throwing a completely new light on nature, which affected everyone. The discovery of the ‘mother civilisation’ for European society added to this, reinforcing the view that religions evolved, too, meaning that one old way of understanding the world was subsumed under another, newer, more scientific approach. Such a change in the fundamentals was bound to be disturbing, but there was more to come. As the autumn of 1900 approached, yet another breakthrough was reported that added a third major realignment to our understanding of nature.

In 1900 Max
Planck
was forty-two. He was born into a very religious, rather academic family, and was an excellent musician. He became a scientist in spite of, rather than because of, his family. In the type of background he had, the humanities were considered a superior form of knowledge to science. His cousin, the historian Max Lenz, would jokingly refer to scientists
(Naturforscher)
as foresters (
Naturförster
). But science was Planck’s calling; he never doubted it or looked elsewhere, and by the turn of the century he was near the top of his profession, a member of the Prussian Academy and a full professor at the University of Berlin, where he was known as a prolific generator of ideas that didn’t always work out.
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Physics was in a heady flux at the turn of the century. The idea of the atom, an invisible and indivisible substance, went all the way back to classical Greece. At the beginning of the eighteenth century Isaac Newton had thought of atoms as minuscule billiard balls, hard and solid. Early-nineteenth-century chemists such as John Dalton had been forced to accept the existence of atoms as the smallest units of elements, since this was the only way they could explain chemical reactions, where one substance is converted into another, with no intermediate phase. But by the turn of the twentieth century the pace was quickening, as physicists began to experiment with the revolutionary notion that matter and energy might be different sides of the same coin.
James Clerk Maxwell,
a Scottish physicist who helped found the
Cavendish Laboratory
in Cambridge, England, had proposed in 1873 that the ‘void’ between atoms was filled with an electromagnetic field, through which energy moved at the speed of light. He also showed that light itself was a form of electromagnetic radiation. But even he thought of atoms as solid and, therefore, essentially
mechanical. These were advances far more significant than anything since Newton.
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In 1887
Heinrich Hertz
had discovered electric waves, or radio as it is now called, and then, in 1897, J. J.
Thomson,
who had followed Maxwell as director of the Cavendish, had conducted his famous experiment with a cathode ray tube. This had metal plates sealed into either end, and then the gas in the tube was sucked out, leaving a vacuum. If subsequently the metal plates were connected to a battery and a current generated, it was observed that the empty space, the vacuum inside the glass tube, glowed.
⁴⁴
This glow was generated from the negative plate, the cathode, and was absorbed into the positive plate, the anode.
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The production of cathode rays was itself an advance. But what
were
they exactly? To begin with, everyone assumed they were light. However, in the spring of 1897 Thomson pumped different gases into the tubes and at times surrounded them with magnets. By systematically manipulating conditions, he demonstrated that cathode rays were in fact infinitesimally minute
particles
erupting from the cathode and drawn to the anode. He found that the particles’ trajectory could be altered by an electric field and that a magnetic field shaped them into a curve. He also discovered that the particles were lighter than hydrogen atoms, the smallest known unit of matter, and exactly the same
whatever
the gas through which the discharge passed. Thomson had clearly identified something fundamental. This was the first experimental establishment of the particulate theory of matter.
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This particle, or ‘corpuscle,’ as Thomson called it at first, is today known as the
electron.
With the electron, particle physics was born, in some ways the most rigorous intellectual adventure of the twentieth century which, as we shall see, culminated in the atomic bomb. Many other particles of matter were discovered in the years ahead, but it was the very notion of particularity itself that interested Max Planck. Why did it exist? His physics professor at the University of Munich had once told him as an undergraduate that physics was ‘just about complete,’ but Planck wasn’t convinced.
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For a start, he doubted that atoms existed at all, certainly in the Newtonian/Maxwell form as hard, solid miniature billiard balls. One reason he held this view was the
Second Law of Thermodynamics,
conceived by
Rudolf Clausius,
one of Planck’s predecessors at Berlin. The
First Law of Thermodynamics
may be illustrated by the way Planck himself was taught it. Imagine a building worker lifting a heavy stone on to the roof of a house.
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The stone will remain in position long after it has been left there, storing energy until at some point in the future it falls back to earth. Energy, says the first law, can be neither created nor destroyed. Clausius, however, pointed out in his second law that the first law does not give the total picture. Energy is expended by the building worker as he strains to lift the stone into place, and is dissipated in the effort as heat, which among
other things causes the worker to sweat. This dissipation Clausius termed ‘entropy’, and it was of fundamental importance, he said, because this energy, although it did not disappear from the universe, could never be recovered in its original form. Clausius therefore concluded that the world (and the universe) must always tend towards increasing disorder, must always add to its entropy and eventually run down. This was crucial because it implied that the universe was a one-way process; the Second Law of Thermodynamics is, in effect, a mathematical expression of time. In turn this meant that the Newton/Maxwellian notion of atoms as hard, solid billiard balls had to be wrong, for the implication of that system was that the ‘balls’ could run either way – under that system time
was
reversible; no allowance was made for entropy.
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In 1897, the year Thomson discovered electrons, Planck began work on the project that was to make his name. Essentially, he put together two different observations available to anyone. First, it had been known since antiquity that as a substance (iron, say) is heated, it first glows dull red, then bright red, then white. This is because longer wavelengths (of light) appear at moderate temperatures, and as temperatures rise, shorter wavelengths appear. When the material becomes white-hot, all the wavelengths are given off. Studies of even hotter bodies – stars, for example – show that in the next stage the longer wavelengths drop out, so that the colour gradually moves to the blue part of the spectrum. Planck was fascinated by this and by its link to a second mystery, the so-called black body problem. A perfectly formed black body is one that absorbs every wavelength of electromagnetic radiation equally well. Such bodies do not exist in nature, though some come close: lampblack, for instance, absorbs 98 percent of all radiation.
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According to classical physics, a black body should only emit radiation according to its temperature, and then such radiation should be emitted at every wavelength. In other words, it should only ever glow white. In Planck’s Germany there were three perfect black bodies, two of them in Berlin. The one available to Planck and his colleagues was made of porcelain and platinum and was located at the Bureau of Standards in the Charlottenburg suburb of the city.
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Experiments there showed that black bodies, when heated, behaved more or less like lumps of iron, giving off first dull red, then bright red-orange, then white light. Why?

Planck’s revolutionary idea appears to have first occurred to him around 7 October 1900. On that day he sent a postcard to his colleague Heinrich Rubens on which he had sketched an equation to explain the behaviour of radiation in a black body.
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The essence of Planck’s idea, mathematical only to begin with, was that electromagnetic radiation was not continuous, as people thought, but could only be emitted in packets of a definite size. Newton had said that energy was emitted continuously, but Planck was contradicting him. It was, he said, as if a hosepipe could spurt water only in ‘packets’ of liquid. Rubens was as excited by this idea as Planck was (and Planck was not an excitable man). By 14 December that year, when Planck addressed the Berlin Physics Society, he had worked out his full theory.
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Part of this was the calculation of the dimensions of this small packet of energy, which Planck called
h
and which
later became known as
Planck
’s
constant.
This, he calculated, had the value of 6.55 × 10
^–27
ergs each second (an erg is a small unit of energy). He explained the observation of black-body radiation by showing that while the packets of energy for any specific colour of light are the same, those for red, say, are smaller than those of yellow or green or blue. When a body is first heated, it emits packets of light with less energy. As the heat increases, the object can emit packets with greater energy. Planck had identified this very small packet as a basic indivisible building block of the universe, an ‘atom’ of radiation, which he called a
‘quantum.’
It was confirmation that nature was not a continuous process but moved in a series of extremely small jerks. Quantum physics had arrived.

Not quite. Whereas Freud’s ideas met hostility and de Vries’s rediscovery of Mendel created an explosion of experimentation, Planck’s idea was largely ignored. His problem was that so many of the theories he had come up with in the twenty years leading up to the quantum had proved wrong. So when he addressed the Berlin Physics Society with this latest theory, he was heard in polite silence, and there were no questions. It is not even clear that Planck himself was aware of the revolutionary nature of his ideas. It took four years for its importance to be grasped – and then by a man who would create his own revolution. His name was Albert Einstein.

On 25 October 1900, only days after Max Planck sent his crucial equations on a postcard to Heinrich Rubens, Pablo Picasso stepped off the Barcelona train at the Gare d’Orsay in Paris. Planck and Picasso could not have been more different. Whereas Planck led an ordered, relatively calm life in which tradition played a formidable role, Picasso was described, even by his mother, as ‘an angel and a devil.’ At school he rarely obeyed the rules, doodled compulsively, and bragged about his inability to read and write. But he became a prodigy in art, transferring rapidly from Malaga, where he was born, to his father’s class at the art school in Corunna, to La Llotja, the school of fine arts in Barcelona, then to the Royal Academy in Madrid after he had won an award for his painting
Science and Charity.
However, for him, as for other artists of his time, Paris was the centre of the universe, and just before his nineteenth birthday he arrived in the City of Light. Descending from his train at the newly opened station, Picasso had no place to stay and spoke almost no French. To begin with he took a room at the Hôtel du Nouvel Hippodrome, a
maison de passe
on the rue Caulaincourt, which was lined with brothels.
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He rented first a studio in Montparnasse on the Left Bank, but soon moved to Montmartre, on the Right.

Paris in 1900 was teeming with talent on every side. There were seventy daily newspapers, 350,000 electric streetlamps and the first Michelin guide had just appeared. It was the home of Alfred Jarry, whose play
Ubu Roi
was a grotesque parody of Shakespeare in which a fat, puppetlike king tries to take over Poland by means of mass murder. It shocked even W. B. Yeats, who attended its opening night. Paris was the home of Marie Curie, working on radioactivity, of Stephane Mallarmé, symbolist poet, and of Claude Debussy and his ‘impressionist music.’ It was the home of Erik Satie and his ‘atonally
adventurous’ piano pieces. James Whistler and Oscar Wilde were exiles in residence, though the latter died that year. It was the city of Emile Zola and the Dreyfus affair, of Auguste and Louis Lumière who, having given the world’s first commercial showing of movies in Lyons in 1895, had brought their new craze to the capital. At the Moulin Rouge, Henri de Toulouse-Lautrec was a fixture; Sarah Bernhardt was a fixture too, in the theatre named after her, where she played the lead role in
Hamlet en travesti.
It was the city of Gertrude Stein, Maurice Maeterlinck, Guillaume Apollinaire, of Isadora Duncan and Henri Bergson. In his study of the period, the Harvard historian Roger Shattuck called these the ‘Banquet Years,’ because Paris was celebrating, with glorious enthusiasm, the pleasures of life. How could Picasso hope to shine amid such avant-garde company?
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