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30/08/2014

„Stephen Hawking. A Life in Science” – Fragmente 2


Din cartea: „Stephen Hawking a Life in Science” – Michael White and John Gribbin. John Henry Press.2002.

Electrons and atoms are not like tiny snooker balls bouncing around in accordance with Newton’s laws.

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…in a small city in Hertfordshire a seventeen-year-old schoolboy named Stephen Hawking was getting ready for the Oxford entrance examination in a large, cluttered bedroom in his parents’ rambling Edwardian house.

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Stephen and his father settled on the first alternative, and he was entered for the examination toward the end of his final year at St. Albans School. The intention from the start was that he was going for a scholarship, the highest award offered by the university.

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Stephen insisted that he wanted to read mathematics and physics, a course then known as natural science. His father was unconvinced; he believed there were no jobs in mathematics apart from teaching. Stephen knew what he wanted to do and won the argument; medicine had little appeal for him. As he says himself: My father would have liked me to do medicine. However, I felt that biology was too descriptive, and not sufficiently fundamental. Maybe I would have felt differently if I had been aware of molecular biology, but that was not generally known about at the time.1

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The entrance examination was pretty tough. It was spread over two days and consisted of five papers in all, each of which was two and a half hours long. These included two physics and two mathematics papers, followed by a paper that tested candidates on their general knowledge and awareness of current affairs and world issues. A typical question would have been something like “Discuss the possible short-term global consequences of Fidel Castro’s takeover of Cuba.”

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Little did he know that he had scored around ninety-five percent in both his physics papers, with only slightly lower percentages in the others. A few days after the second interview the all-important letter fell on to the Hawkings’ doormat. University College was offering him a scholarship. He was invited to enroll at Oxford University the following October, the only condition being that he obtain two A Level passes in the summer.

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In the late fifties and early sixties, Oxford, as a microcosm of British society, was on the brink of great change. When Hawking arrived at the High on his first October Thursday as an undergraduate, the university had in many respects changed little since his father’s time or, indeed, for the past few hundred years. University discipline had relaxed somewhat since the end of the war. Before then, students had been forbidden to enter the city’s pubs and could, if caught, be expelled from them by the university police, known as the Bulldogs. Women were not allowed in male students’ rooms without written permission from the dean, who would specify strict time limitations and conditions in a letter sent to the head porter, who would then rigorously uphold the dean’s instructions. All this changed when servicemen returning from the war entered the university either as freshmen or to restart courses interrupted by the fighting.

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Most Oxford colleges are built in the form of a number of quads, each with a lawn at the center and paths around and across the grass. From the quads, staircases lead off into the buildings, and the students’ rooms are on a number of levels up to the top of each staircase.

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The intake at Oxford was still largely male and from the country’s private schools, and the majority of those were from the top ten, including  Eton, Harrow, Rugby, and Westminster.

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A simple point of reference illustrates the changes about to hit Oxford soon after Hawking went up, encapsulated by one of his contemporaries. “When we arrived in Oxford,” he said, “anybody who was anybody rowed and never wore jeans. When we left, anybody who was anybody never rowed and did wear jeans.”

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Despite its many charms, Hawking’s first year at Oxford was, by all accounts, a pretty miserable time for him. Very few of his school contemporaries and none of his close friends from St. Albans had gone up the same year.

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The prevailing attitude at Oxford at that time was very anti-work. You were supposed either to be brilliant without effort or to accept your limitations and get a fourth-class degree. To work hard to get a better class of degree was regarded as the mark of a gray man, the worst epithet in the Oxford vocabulary.2

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They were all or nothing, the focal point of the whole three years of study. Hawking once calculated that during the entire three years of his course at Oxford he had done something like 1,000 hours’ work, an average of one hour per day—hardly a foundation for the arduous finals. One friend remembers with amusement, “Towards the end he was working as much as three hours a day!”

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He had applied to Cambridge to begin Ph.D. studies in cosmology under the most distinguished British astronomer of the day, Fred Hoyle. The catch was that to be accepted for Cambridge he had to achieve a first-class honors degree, the highest possible qualification at Oxford.

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The chief examiner asked him to tell the board of his plans for the future. “If you award me a first,” he said, “I will go to Cambridge. If I receive a second, I shall stay in Oxford, so I expect you will give me a first.” They did.

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It has been said that Cambridge is the only true university town in England. Oxford is a much larger city and has, lying beyond the ring road, heavy industrial areas nestling next to one of Europe’s largest housing estates. Cambridge is altogether quainter and more thoroughly dominated by academia. Although evidence suggests that the University of Cambridge was established by defec-tors from Oxford, both seats of learning were created at around the same time in the twelfth century, using as their model the University of Paris. Like Oxford, Cambridge University is a collection of colleges under the umbrella of a central university authority. Like Oxford, it attracts the very best scholars from around the world and has a global reputation, paralleled only by its great rival and historical twin a mere eighty miles away. And, like Oxford, it is steeped in tradition, drama, and history.

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Stephen Hawking, B.A. (Hon.), arrived in Cambridge in October 1962, exchanging the scorched, barren landscape of the Middle East for autumnal wind and drizzle across the darkening fields of East Anglia.

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In the days leading up to his move to Cambridge, with the world outside looking set to tear itself apart, Stephen Hawking was gradually becoming aware of an inner personal crisis. Toward the end of his time at Oxford he had begun to find some difficulty in tying his shoelaces, he kept bumping into things, and a number of times he felt his legs give way from under him. Without a drink passing his lips he would, on occasion, find his speech slurring as though he were intoxicated. Not wanting to admit to himself that something was wrong, he said nothing and tried to get on with his life.

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He had originally chosen to go to Cambridge University because at the time Oxford could not offer cosmological research and, most important, he wanted to study under Fred Hoyle, who had a worldwide reputation as the most eminent scientist in the field.

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When Stephen returned to St. Albans for the Christmas vacation at the end of 1962, the whole of southern England was covered in a thick blanket of snow. In his own mind he must have known that something was wrong. The strange clumsiness he had been experiencing had occurred more frequently but had gone unobserved by anyone in Cambridge. Sciama remembered noticing early in the term that Hawking had a very slight speech impediment but had put it down to nothing more than that.

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He returned to Cambridge and awaited the results of the tests. A short time later he was diagnosed as having a rare and incurable disease called amyotrophic lateral sclerosis, or ALS, known in the United States as Lou Gehrig’s disease after the Yankee baseball player who died from the illness. In Britain it is usually called motor neuron disease.

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One of the amazing ironies of the situation was that Stephen Hawking just happened to be studying theoretical physics, one of the very few jobs for which his mind was the only real tool he needed. If he had been an experimental physicist, his career would have been over.

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In the twice-daily ritual, well established at the Cavendish and carried over to Silver Street, everyone would meet at 11 a.m. for coffee and 4 p.m. for tea to exchange their latest thoughts and ideas.

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During his first two years at Cambridge, the effects of the ALS disease rapidly worsened. He was beginning to experience enormous difficulty in walking and was compelled to use a stick in order to move just a few feet.

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Over the course of the talks at King’s, Roger Penrose had introduced his colleagues to the idea of a space-time singularity at the center of a black hole, and naturally the group from Cambridge was tremendously excited by this.

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Hawking peered through the window, watching the darkened fields stream past and the juxtaposition of his friends reflected in the glass. His colleagues were arguing over one of the finer mathematical points in Penrose’s discussion. Suddenly, an idea struck him, and he looked away from the window. Turning to Sciama sitting across from him, he said, “I wonder what would happen if you applied Roger’s singularity theory to the entire Universe.” In the event it was that single idea that saved Hawking’s Ph.D. and set him on the road to science superstardom.

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Applying singularity theory to the Universe was by no means an easy problem, and within months Sciama was beginning to realize that his young Ph.D. student was doing something truly exceptional. For Hawking this was the first time he had really applied himself to anything. As he says: I . . . started working hard for the first time in my life. To my surprise, I found I liked it. Maybe it is not really fair to call it work. Someone once said, “Scientists and prostitutes get paid for doing what they enjoy.”11

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The final chapter of Hawking’s thesis was a brilliant piece of work and made all the difference to the awarding of the Ph.D. Doctors and Doctorates 73 work was judged by an internal examiner, Dennis Sciama, and an expert external referee. As well as being passed or failed, a Ph.D. can be deferred, which means that the student has to resubmit the thesis at a later date, usually after another year. Thanks to his final chapter, Hawking was saved this humiliation and the examiners awarded him the degree. From then on the twenty-three-year-old physicist could call himself Dr. Stephen Hawking.

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Obviously, since it could emit no light, such an object would be black, which is why the American relativist John Wheeler dubbed them “black holes” in 1969. But although it was well known that the general theory made this prediction, at the time Hawking was completing his undergraduate studies and moving on to research no one took the notion of black holes seriously. The reason is that there are very many known stars that have more than three times the mass of our Sun.

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But quantum theory said that there is a way to make a star denser than a white dwarf. If the star were squeezed even more by gravity, the electrons could be forced to combine with protons to make more neutrons. The result would be a star made entirely of neutrons, and these could be packed together as closely as the protons and neutrons in an atomic nucleus. This would be a neutron star.

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The density of the matter in a neutron star, in grams per cubic centimeter, would be 1014—that is, 1 followed by 14 zeros, or one hundred thousand billion. Even an object this dense would not be a black hole, though, for light could still escape from its surface into the Universe at large.

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The quantum equations said, in fact, that there was no way that even neutrons could hold up the weight of a dead star of 3 solar masses or more and that, if any such object were left over from the explosive death throes of a massive star, it would collapse inward completely, shrinking to a mathematical point called a singularity. Long before the collapsing star could reach this state of zero volume and infinite density, it would have wrapped space-time around itself, cutting off the collapsar from the outside Universe.

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if it were possible to squeeze our own Sun down into a sphere with a radius of about 3 kilometers, it would become a black hole. So would the Earth, if it were squeezed down to about a centimeter. In each case, once the object had been squeezed down to the critical size, gravity would take over, closing space-time around the object while it continued to shrink away into the infinite density singularity inside the black hole.

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The mid-sixties turned out to be one of the most important times in Stephen Hawking’s life. Having become engaged to Jane, he realized that he would need to find a job very quickly if they were to be married. After obtaining a doctorate, the next stage in the career of any academic is usually to secure a fellowship, accompanied by a grant, in order to continue research.

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Fellowship is considered a great honor and a means by which academics may continue with their research and be paid for it. In return, a college gains prestige if one of its fellows turns out to be highly successful.

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The couple was married in July 1965 in the chapel of Hawking’s postgraduate college, Trinity Hall. It was not a typical “academic” wedding, but neither was it, by any means, a society occasion. Both sets of parents were ordinary, middle-class people.

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Of course they both knew, as did all the others on that day, that Stephen might die within a short time. In fact, according to the medical predictions he was already living on borrowed time.

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At the DAMTP and in Cambridge academic circles, Hawking was beginning to cultivate a “difficult genius” image, and his reputation as successor to Einstein, although embryonic, was already beginning to follow him around. People who knew him in those days remember him as a friendly and cheerful character, but already his natural brashness, coupled with his physical disabilities, was beginning to create communication difficulties with many of those around him.

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Both Jane and Stephen knew that they should not waste any time in starting a family once they were married, and their first child, a boy they named Robert, was born in 1967.

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Hawking was working harder than he had ever worked before, and it was paying dividends. In 1966 he won the Adams Prize for an essay entitled “Singularities and the Geometry of Spacetime.”

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He spent most of this time in collaboration with Roger Penrose, who was by then professor of applied mathematics at Birkbeck College in London. One of the major difficulties the two of them faced was that they had to devise new mathematical techniques in order to carry out the calculations necessary to verify their theories—to make them empirically sound and not just ideas. Einstein had experienced a similar problem fifty years earlier with the mathematics of general relativity. He, like Hawking, was not a particularly brilliant mathematician. Fortunately for Hawking, however, Penrose was. In fact, he was fundamentally a mathematician rather than a physicist, but at the deep level at which the two subjects become almost indistin-guishable.

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Hawking’s way of working is largely intuitive—he just knows if an idea is correct or not. He has an amazing feel for the subject, a bit like a musician playing by ear. Penrose thinks and works in a different way, more like a concert pianist following a musical score. The two approaches meshed perfectly and soon began to produce some very interesting results on the nature of the early Universe.

20/07/2014

„Stephen Hawking. A Life in Science” – Fragmente 1


Din cartea:” Stephen Hawking a Life in Science” (Michael White and John Gribbin), John Henry Press.2002.

At the age of twenty-one Hawking discovered that he had the wasting disease ALS, also called motor neuron disease, and he has spent much of his life confined to a wheelchair.

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She asks the professor if he believes that there is a God who created the Universe and guides His creation. He smiles momentarily, and the machine voice says, “No.”

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He has been made a CBE—commander of the British empire—and then companion of honour by Queen Elizabeth II and has written a popular science book, A Brief History of Time, which stayed on the best-seller list for five years from 1988 to 1993 and has to date sold over ten million copies worldwide.

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It is perhaps one of those oddities of serendipity that January 8, 1942 was both the three-hundredth anniversary of the death of one of history’s greatest intellectual figures, the Italian scientist Galileo Galilei, and the day Stephen William Hawking was born into a world torn apart by war and global strife. But as Hawking himself points out, around two hundred thousand other babies were born that day, so maybe it is after all not such an amazing coincidence.

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Stephen’s mother, Isobel, had arrived in Oxford only a short time before the baby was due. She lived with her husband Frank in Highgate, a northern suburb of London, but they had decided that she should move to Oxford to give birth.

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When he was two weeks old, Isobel Hawking took Stephen back to London and the raids. They almost lost their lives when he was two, when a V2 rocket hit a neighbor’s house.

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Hawking was eight when the family arrived there. Frank Hawking had a strong desire to send Stephen to a private school. He had always believed that a private school education was an essential ingredient for a successful career. There was plenty of evidence to support this view: in the 1950s, the vast majority of members of Parliament had enjoyed a privileged education, and most senior figures in institutions such as the BBC, the armed forces, and the country’s universities had been to private schools.

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Stephen, he decided, would be sent to Westminster, one of the best schools in the country.

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When he was ten, the boy was entered for the Westminster School scholarship examination. Although his father was doing well in medical research, a scientist’s salary could never hope to cover the school fees at Westminster—such things were reserved for the likes of admirals, politicians, and captains of industry. Stephen had to be accepted into the school on his own academic merit; he would then have his fees paid, at least in part, by the scholarship.

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St. Albans School had 600 boys when Stephen arrived there in September 1952. Each year was streamed as A, B, or C according to academic ability. Each boy spent five years in senior school, progressing from the first form to the fifth, at the end of which period he would sit for Ordinary (O) Level exams in a broad spectrum of subjects, the brighter boys taking eight or nine examinations. Those who were successful at O

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He passed easily and, along with exactly ninety other boys, was accepted into the school on September 23, 1952. The fees were fifty-one guineas (£53.55) a term.

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St. Albans School proudly boasted a very high intellectual standard, a fact recognized and appreciated by the Hawkings very soon after Stephen started there. Before long, any nagging regrets that he had been unable to enter Westminster were forgotten. St. Albans School was the perfect environment for cultivating natural talent.

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Much remembered and highly thought of was a master fresh out of university named Finlay who, way ahead of his time, taped radio programs and used them as launch points for discussion classes with 3A. The subject matter ranged from nuclear disarmament to birth control and everything in between. By all accounts, he had a profound effect on the intellectual development of the thirteen-year-olds in his charge, and his lessons are still fondly remembered by the journalists, writers, doctors, and scientists they have become today.

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English schoolboys attending the private schools of the 1950s had little time for girls in their busy program, and parties were single-sex affairs until the age of fifteen or sixteen. It was only then that they would have the inclination and parental permission to hold sherry parties at their houses

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Frank Hawking kept meticulous accounts of everything he did in a collection of diaries maintained until the day he died. He also wrote fiction, completing several unpublished novels. One of his literary efforts was written from a woman’s viewpoint. Although Isobel respected his efforts when she read it, she believed that it was unsuccessful.

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Michael Church describes how he felt an indefinable intellectual presence when it came to discussing matters vaguely mystical or metaphysical with Stephen. Remembering one encounter, he says: I wasn’t a scientist and didn’t take him remotely seriously until one day when we were messing around in his cluttered, joke-inventor’s den. Our talk turned to the meaning of life—a topic I felt pretty hot on at the time—when suddenly I was arrested by an awful realization: he was encouraging me to make a fool of myself, and watching me as though from a great height. It was a profoundly unnerving moment.2

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In the spring of 1958, Hawking and his friends, including new recruits to the group, Barry Blott and Christopher Fletcher, built a computer called LUCE—Logical Uniselector Computing Engine. In the 1950s in Britain, only a few university departments and the Ministry of Defence had computers.

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Hawking and his friends received their first exposure to the press when the local newspaper, the Herts Advertiser, covered the story of the “schoolboy boffins” building their newfangled machine.

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When scientists refer to the “classical” ideas of physics, they are not referring back to the thoughts of the Ancient Greeks. Strictly speaking, classical physics is the physics of Isaac Newton, who laid the foundations of the scientific method for investigating the world back in the seventeenth century.

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two revolutions, the first sparked by Einstein’s general theory of relativity and the second by the quantum theory. The first is the best theory we have of how gravity works; the second explains how everything else in the material world works. Together, these two topics, relativity theory and quantum mechanics, formed the twin pillars of modern twentieth-century science. The Holy Grail of modern physics, sought by many, is a theory that will combine the two into one mathematical package.

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the discovery of pulsars, in 1967, the year Stephen Hawking celebrated his own twenty-fifth birthday. These objects are now known to be neutron stars, the collapsed cores of massive stars that have ended their lives in vast outbursts known as supernova explosions. It was the discovery of pulsars, collapsed objects on the verge of becoming black holes, that revived interest in the extreme implications of Einstein’s theory of gravity, and it was the study of black holes that led Hawking to achieve the first successful marriage between quantum theory and relativity.

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Hawking was already working on the theory of black holes at least two years before the discovery of pulsars, when only a few mathematicians bothered with such exotic implications of Einstein’s equations,

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But within ten years, observations made by Edwin Hubble with a new and powerful telescope on a mountaintop in California had shown that the Universe is expanding.

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One of the people instrumental in establishing this “wave-particle duality” of light was Einstein, who in 1905 showed how the way in which electrons are knocked out of the atoms in a metal surface by electromagnetic radiation (the photoelectric effect) can be explained neatly in terms of photons, not in terms of a pure wave of electromagnetic energy. (It was for this work, not his two theories of relativity, that Einstein received his Nobel Prize.)

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The German physicist Werner Heisenberg established in the 1920s that all observable quantities are subject, on the quantum scale, to random variations in their size, with the magnitude of these variations determined by Planck’s constant. This is Heisenberg’s famous “uncertainty principle.” It means that we can never make a precise determination of all the properties of an object like an electron: all we can do is assign probabilities, determined in a very accurate way from the equations of quantum mechanics, to the likelihood that, for example, the electron is in a certain place at a certain time.

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