by Philipp Blom
Curie investigated all known elements and made two crucial discoveries: in addition to uranium, thorium, too, appeared to give off radiation; moreover, despite their very different chemical properties different compounds containing the two elements showed the same amount of radiation. Curie concluded that it was not the molecular structure of a radioactive substance that determined the strength of the radiation, but the amount of uranium or thorium contained in it. In other words: as uranium and thorium are specific atoms, part of the periodical table, the radiation had to be a property of the atom itself and not of the molecular structure. This was a revolutionary discovery: if atoms, until then considered the smallest possible unit of all matter, could give off rays, their structure had to be more complex than previously realized.
Of all natural radioactive substances tested, pitchblende, a uranium-rich mineral found mainly in Joachimsthal (today’s Jáchymov in the Czech Republic), appeared to be the most likely candidate for further research, especially because it had a puzzling quality: it was more radioactive than pure uranium itself, an indication that it contained other, hitherto unknown, elements. Together with her husband Pierre, who abandoned his own research to work together with his wife, Marie now set out to procure large amounts of pitchblende (a generous though not disinterested donation of the ore from the Austro-Hungarian Academy of Sciences was a great help) and to break them down into their individual elements by grinding them, dissolving them in acid and crystallizing different compounds, again and again. One of these compounds stood out, and in 1898 the Curies felt confident enough to present their research claiming that ‘we thus believe that the substance that we have extracted from pitchblende contains a metal never known before, akin to bismuth in its analytic properties. If the existence of this new metal is confirmed, we suggest that it should be called polonium after the name of the country of origin of one of us.’ Later in the same year they published a second finding: barium compounds, they wrote, contained another, even more highly radioactive new element, which they named radium.
The Nobel Prize
The doctoral thesis by the young scientist Marie Curie outlining the discovery of a new element with unknown qualities caused a sensation in scientific circles. The members of the Académie des Sciences in Paris thought such brilliance was worth a Nobel Prize, but not to the young woman. They recommended Pierre Curie and Henri Becquerel for a joint award, and the Swedish Academy consented. Monsieur Curie was duly notified by mail - and refused to accept the award. He was honoured to be proposed, he replied to the Prize-givers, but the most important contribution was his wife’s and he could not be so distinguished without her. After some hurried negotiations, the committee agreed and Pierre was allowed to share his part of the Prize with his wife, who became joint laureate in the 1903 Nobel Prize for Physics for the discovery of radium.
Marie was so dogged by ill health that she could not travel to Stockholm for the awards ceremony, and once again her husband showed himself loyal. Two years later, in 1905, they made the journey together to accept the prize. In his acceptance speech, Pierre outlined the hopes and the fears connected with the new element:
... radium could become very dangerous in criminal hands, and here the question can be raised whether mankind benefits from knowing the secrets of Nature, whether it is ready to profit from it or whether this knowledge will not be harmful for it. The example of the discoveries of Nobel is characteristic, as powerful explosives have enabled man to do wonderful work. They are also a terrible means of destruction in the hands of great criminals who are leading the peoples towards war. I am one of those who believe with Nobel that mankind will derive more good than harm from the new discoveries.
The Nobel Prize brought international fame to the Curies and also finally allowed them to work under better conditions after Pierre was appointed to a professorship, which included his own laboratory, at the Sorbonne. Sudden fame also had its unwelcome aspects. The media were interested in the couple, in the discovery, in the extraordinary woman who had beaten the men at their game through sheer intelligence and almost superhuman perseverance. There were dinners and ceremonies, interviews, visiting journalists - all of them annoying distractions from research. With its seemingly miraculous qualities, radium had captured the public’s imagination.
The Curies were happiest away from this circus, immersed in their research. Pierre even strapped a glass with uranium salts to his right arm to observe the effects and found that they produced a burn leaving a grey scar that would not heal even after six weeks; he also liked to carry around a small amount of uranium in his waistcoat pocket to illustrate its phosphorescent properties to friends. Without knowing it, the Curies were inexorably poisoning themselves with massive doses of radioactivity.
When catastrophe struck one of science’s greatest teams, however, radiation played a part only in so far as it had exhausted Pierre Curie. In 1906, on Maundy Thursday, he crossed a busy road. It was raining and his umbrella prevented him from seeing a military supply wagon coming towards him. He walked right into the horses and was thrown to the ground. One of the vehicle’s rear wheels crushed his skull. A few days after his funeral, his distraught wife wrote in her notebook: ‘My Pierre, I am constantly thinking of you. My head burns like fire and I feel I am losing my mind. I cannot understand how it can be that I have to live without seeing you, without smiling at the dear companion of my life.’ Marie did live on, constantly pursuing her research, despite years of ill health and a wave of hostility directed against her by the French conservative press. She went on to be awarded a second Nobel Prize in 1911 for her research into radioactivity. Her death in 1934 was caused by radiation-induced leukaemia.
The Dissolution of Certainty
Science is a good place for outsiders. An unusual vantage point sometimes allows one to see things other people cannot see. Marie Curie had fought her way from her native Poland into the heart of the French scientific establishment. Another scientist of genius had begun his life on a New Zealand potato farm. A precocious boy and gifted researcher, he had studied in Christchurch and applied for a scholarship at Cambridge. Legend has it that he was out in the fields harvesting when news of his successful application came. He straightened himself and said: ‘That’s the last potato I’ve ever dug.’
Ernest Rutherford (1871-1937) investigated the phenomenon of radiation in order to understand the nature of matter itself, the structure of the atom. In experiments conducted together with the young Danish scientist Niels Bohr (1885-1962), Rutherford had observed that an ultra-thin gold foil exposed to radiation would allow most of the alpha rays (one of three kinds of radiation emitted by radioactive substances) to pass through, while a small number of alpha particles appeared to bounce off the surface of the foil. Only one explanation was possible, Rutherford thought, namely that atoms were not what they had been thought to be. Until then, atoms had, to use his own image, been imagined like plum puddings: solid and homogenous, with a few electrons scattered inside like sixpences and sultanas. No such atom, however, would let the relatively weak alpha rays pass through. This would be possible only if an atom actually was mostly empty space, more like a solar system than a plum pudding, its entire mass compressed in a sunlike core ten thousand times smaller than the orbit of the electrons circling around it and defining the volume of the atom. Matter, it turned out, was neither solid nor still, and was, at least in part, a state of energy, constantly in movement. There was, in fact, nothing stationary in the world at all - at an atomic level, everything was velocity and energy, constellations of myriads of particles swirling and hurtling through empty space, bombarding and interfering with one another, and possessed of limitless energy and electric charge.
The relationship between matter and energy, or the convergence of the two, was also the subject of the after-hours work of another scientific outsider, an ‘Expert 3rd Class’ at the Swiss Office for Intellectual Property in Berne, 26-year-old Albert Einstein (1879-1955). From the perspective of a
theoretician, he formulated a view of the world that reinforced the findings of the likes of Röntgen, Rutherford and the Curies. His doubts, however, did not concern a mere trifle like the composition of matter, but rather, the nature of time and space itself. After Einstein, the world was simply not the same as before.
Theoretical advances and improved instruments, the observation of distant stars and of electromagnetic fields had pushed the physical concepts of the day to their limits and exposed gaps in the current scientific models of the world. One problem especially troubled scientists: to explain the movement of light and electrical waves through space, science had long postulated the existence of a medium, ether. Just as sound impulses make the air vibrate but cannot travel in a vacuum (the absence of gases), light waves and electricity, which can travel through a vacuum, must surely need the invisible ether as a propagating medium.
Detecting this ether and proving its existence therefore became one of the prime challenges of physics. The most famous of these attempts was the Michelson-Morley experiment. If the earth moved through cosmic ether in its orbit around the sun, the two scientists hypothesized, then the different velocities of the earth hurtling through the ether on its elliptical orbit (faster as it swings towards the two extremes, slower as it almost reaches them) should result in different measurements for the speed of light as seen from the earth, just as a cyclist moving against the wind would feel a higher wind speed than another cycling with the wind. Just as the two cyclists driving through the storm in opposite directions could determine the speed of the gale by meeting in a pub and comparing notes, using their variant measurements by adding or subtracting their own speeds from the wind speed they each measured during their ride to arrive at the real speed of the wind, Michelson and Morley thought that they could determine the speed of the earth relative to the ether by exploiting the differences in the speed of light measured.
Michelson and Morley’s experiment had been based on one of the fundamental principles of classical physics, the so-called Galilean invariance. During the seventeenth century, the Italian physicist Galileo Galilei had postulated that the laws of physics were the same for all observers, independent of their movement through time and space. If a man fell from the tower of Pisa and was observed by a second man standing on the ground, they would both measure the same time for the fall (though the faller might have other things to worry about than to get out a watch), as time was an absolute factor for both of them.
The experiment was carried out with the most sophisticated instruments constructed especially for the purpose, but the result was always unsatisfying. Independent of the velocity of the earth in its orbit, the time of day or of year, the measured speed of light was always the same. If the speed of light, however, was independent of the speed of the planet from which it was observed, one of two things had to be true: either the experiment was flawed due to an unknown cause, or the laws of physics did not work under all circumstances as they had been defined by Newton and Galileo. Scientists had reached an impasse: descriptions of moving bodies, of the nature of space and of time were at odds with the phenomena observed. Regarding the speed of light and its movement through space of time, physics had lost the ability to make accurate predictions, the very definition of a scientific proposition.
An unlikely
revolutionary:
Albert Einstein.
Einstein’s genius lay in his intellectual courage to abstract a theory of space and time from observable reality, to dare to think the unthinkable. Albert Michelson, whose experiment proved so obstinately fruitless, had given a perfect example of the conviction of many of the day’s physicists when he claimed in 1899: ‘The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote ... Our future discoveries must be looked for in the sixth place of decimals.’ Six years before physics was to be thrown wide open to an entirely new understanding of the world, one of its main protagonists regarded the case as closed.
Intellectually rebellious from his earliest youth, Einstein was simply not intimidated by this orthodoxy. If Michelson and Morley had not found what they had been looking for, he realized, it was because they had been thinking too small, had not emancipated their analysis from the realm of human experience. Consider the unfortunate Italian falling from the leaning tower of Pisa and his friend watching him. The time of his fall might seem the same to both of them, as the distance from the ground and the speed of the fall are minute in a cosmic context, but when translated to a larger scale a very different picture would emerge.
If the faller had survived his accident but then had the bad luck to be loaded into an early spaceship and launched towards a distant star at, let us suppose, half the speed of light, something very strange would happen: while the astronaut himself would notice no difference in the passage of time, the clocks on board his ship would seem to be slower than those of an observer on the ground. Imagine a new constellation in the sky: a chain of twinkling watches set into the universe at regular intervals. The astronaut’s own pocket watch (which, miraculously, was not damaged after falling from the leaning tower) would continue to mark time as usual, and a stationary observer looking at two equidistant celestial clocks would equally see them ticking steadily, showing the same time, because the light travelling from the clocks to his eye would take the same amount of time. On the spaceship, however, it would be a different story: passing one clock, the spaceship would meet the light travelling towards it from the second clock halfway (it travels at half the speed of light) and would therefore receive its signal earlier, and so for every clock along the way. For the traveller on board, the clocks outside the ship would move fast and time would elapse more quickly, while it remained constant on board.
The stationary observer would notice the opposite effect: time in the spaceship would seem dilated, an effect that would increase as the spaceship approached the speed of light. Time, in fact, is not an absolute value, with clocks ticking the same way for all of us. It is relative, depending on the movement of each observer, even though this effect only becomes relevant at very high speeds. A person falling off the tower of Pisa might not measure time differently from an observer, but a person in a spaceship would.
This elegant notion allowed Einstein to explain why Michelson and Morley had not been able to measure variances in the speed of light relative to the speed of the earth. While measured time is relative to the measurer, the speed of light is, in fact, a constant, and the dilation of time at high velocities means that the speed of light is not relative to the velocity of the observer, but is always measured with the same value: 299,792,458 metres per second. No object with mass can actually attain this speed (it would require infinite energy to do so), but the closer an object gets to it, the slower time moves relative to a slower or stationary observer, cancelling out the differential between its movement, relative to the speed of light. While the movement of the earth through space-time is vastly slower than that of light, a minimal time dilation reverses any possible variations in light speed as measured on earth.
Published in 1905 in the journal Annalen der Physik, the Special Theory of Relativity, as it came to be called, made the youthful patent clerk a star in scientific circles. Einstein had emancipated space and time from human experience, from old ways of understanding the world. He had chosen logical consistency over perception. Previous theories could not work, he had demonstrated, because they had been based on a wrong conception of space and time, a conception based on the small bandwidth of speeds much lower than the speed of light. What makes Einstein’s contribution all the more significant is the fact that most of the mathematical and physical concepts underlying his theory were already in existence, but none of his colleagues had had the intellectual courage to go the one decisive step further, into the unknown. Scientists like the Curies and Rutherford, the German
Max Planck and the Danish Niels Bohr had begun to show that the nature of matter was not what it appeared to be. Now, space and time themselves had been transformed.
There is an obvious kinship between Einstein’s radical relativity of space and time and Ernst Mach’s epistemological impressionism, which we encountered in the last chapter and which reduced the world and even the self to an aggregate of individual sensations which might give the impression of being solid and fixed, but are nothing of the kind. Another philosophical parallel, or precedent, for it had been published fifteen years before in 1889, was the great work Essais sur les données immédiates de la conscience (published in English as Time and Free Will) by the Frenchman Henri Bergson (1859-1941), who argued that time was being held hostage by space. Measuring time in terms of movement in space, on the face of a clock, was to make time, the duration of pure experience, of pure quality, subject to the tyranny of quantity, of counting and weighing. Pure duration as it is experienced, Bergson wrote, had nothing to do with space, or with the distance between one minute notch and another on a dial. The experience of duration was quite different, though: a constant dilation and contraction, now flashing by, now passing excruciatingly slowly:
If I follow my eyes to the dial of a watch, the movement of the hand which corresponds to the oscillations of the pendulum, I do not measure duration, as one might believe; I am limited to counting simultaneous moments, which is very different. Outside of me, in space, there is never anything but a single position of the hand and of the pendulum, because nothing remains of their previous positions. Inside me, there is a continuous process of organization and of mutual penetration of facts in my consciousness, and this constitutes true duration.