10 From Heisenberg to Yukawa

Our last five remarkable physicists were born in the seven years between 1901 and

1907. They came from Austria, England, Germany, Japan and America.

Werner Heisenberg (1901–1976)

In the great revolution of fundamental physics which started with the ideas

of Planck and culminated with the impressive breakthrough of the 1920s,

and in the completed framework of quantum mechanics, Heisenberg made

many important contributions. Among these there were two, the basic

treatment of quantum transitions and the formulation of the uncertainty

principle, that were so original and impressive that they came close to the

popular image, so often unrealistic, of great new concepts growing out of the

thoughts of a single individual of genius. In the two years from 1925 to 1927,

which saw the emergence of a new set of principles of physics, which have

since then been refined and widely applied but not fundamentally changed,

the steps taken by Heisenberg were large and decisive.

Werner Karl Heisenberg was born on December 5, 1901 in the elegant

Wu¨ rzburg suburb of Sanderau. The family moved to Munich in 1910 and he

came to regard it as his home town, retaining throughout his life an intense

affection for the city. His father August, the son of a master locksmith, was a

domineering man of great vigour. Werner had a younger brother, Karl, who

later emigrated to America and became wealthy, as well as three sisters

and an elder brother, Erwin, who became an industrial chemist. August

himself held the chair of mediaeval and modern Greek philology at the

university and later became professor of Byzantine studies. We know little

about his wife Anna (n ´eeWecklein), except that her father, a Greek scholar,

was headmaster of the renowned Maximilian Gymnasium in Munich, the

school that her son Werner attended.

Disabling allergies and illnesses recurred throughout Werner’s life; at

the age of five he nearly died of a pulmonary infection. He was a sensitive

youth, who sought security in mathematics and in other formal subjects

such as grammar and science. He distinguished himself early at school, particularly

in mathematics: none of the work seemed to cause him any great

344 From Heisenberg to Yukawa

effort. He showed an early interest in physics and was particularly fascinated

by the possibility of applying mathematics to practical situations. When the

First World War began, his father August, being a reserve officer, was called

up; after a brief experience of combat at the front he was transferred to garrison

duty in Munich. The gymnasium building was commandeered and the

students spent much of their time on paramilitary training, leaving them

with little time for schoolwork. In the spring of 1918 boys as young as sixteen

were drafted for auxiliary service, and Werner was sent to work on a

farm. This involved long hours of manual labour, which left him too tired to

read at night the books he had brought with him, such as the philosophical

works of Kant.

When the First World War ended in November 1918, conditions in

Germany were chaotic, with political authority passing back and forth

between different factions. At one point Heisenberg and other boys worked

as messengers for a group that was trying to restore law and order in the

city. The duties were not onerous and he was able to make progress with

his reading, in which philosophy played an important part. More than

did the farmwork, this provided many contacts and later friendships with

young men of a similar age, with whom he had many earnest discussions.

The youth movement in Germany included various such groups of young

Werner Heisenberg (1901–1976) 345

people who were dissatisfied with what their elders had made of the world

and who were impatient with old customs and old prejudices. They felt an

emotional need for a new leader who would restore Germany’s greatness, to

whom they would give total commitment. In his autobiographical writings

Heisenberg is studiously vague about which particular group he belonged

to, but it was probably the Weisser Ritter, a group that was strongly antagonistic

towards science, especially physics. Thus Heisenberg had to choose

between two extremes, both of which seem to have attracted him.

After graduating from the gymnasium in 1920, Heisenberg matriculated

at the University of Munich. During the first two years there, he

submitted four promising research papers on physics. His mathematical

background was uneven; he knew a lot about number theory but had

only just encountered calculus. When he came across Weyl’s book Raum–

Zeit–Materie, he was both attracted and repelled by the sophistication of

the mathematical arguments and the underlying physical concepts. With

the idea of becoming a mathematician, he went to ask Ferdinand von

Lindemann, the old-fashioned professor of mathematics, for permission to

attend his seminar, even though he was a mere freshman. As soon as he

mentioned having read Weyl’s book, von Lindemann turned him down.

After this rebuff Heisenberg applied to Sommerfeld, a friend of his

father’s, and was immediately accepted. Sommerfeld was not only a great

theoretical physicist with extensive experience in all parts of the subject and

an intimate knowledge of its frontiers, but also probably its greatest teacher.

His seminars and colloquia attracted students and young scholars from far

afield, even from America, and helped to make Munich a world centre for

theoretical physics. Often before or after a colloquium Sommerfeld could be

seen at the Hofgarten cafe discussing problems with members of the audience

and covering the marble tables with formulae. Sometimes he would

invite them to join a skiing party on the Su¨ denfeld, two hours by train from

Munich, where he was part owner of a ski-hut. In the evenings, after a simple

meal, the talk would turn to mathematical physics; and this was when

receptive students might learn what he was currently thinking about. The

forbidding martial impression made by Sommerfeld initially very soon gave

way to a feeling of benevolence and helpful authority. He trained nearly a

third of Germany’s professors of physics; four of his former students were

awarded Nobel prizes. Theoretical physics is a subject that attracts youngsters

with a philosophical mind who speculate about the highest principles

without sufficient foundations. It was just this type of beginner that he

knew how to handle, leading them step by step to a realization of their lack

346 From Heisenberg to Yukawa

of actual knowledge and providing them with the skill necessary for fertile

research.

As soon as Heisenberg became a student at Sommerfeld’s institute

he met the brilliant Wolfgang Pauli, another student, who was somewhat

senior to him and became his mentor. Their close friendship, during which

they frequently exchanged views about major mathematical, physical and

philosophical problems, lasted until the death of Pauli in 1958. Despite

having completed an able thesis on hydrodynamics, Heisenberg only just

succeeded in passing his doctoral examination, because his strengths on

the theoretical side of physics were offset by a poor performance on the

experimental side.

Sommerfeld took Heisenberg to the Georgia Augusta to listen to a

two-week series of seminar talks by Bohr, who made a deep impression on

Heisenberg. When Sommerfeld went for the winter semester 1922/3 to the

University of Wisconsin as a visiting professor, he arranged for Heisenberg

to spend this period with Max Born at Go¨ ttingen. Born was enthusiastic

about the young man and before long they were collaborating on research.

‘Heisenberg is at least as talented as Pauli’, Born reported to his friend

Einstein, ‘but personally more pleasant and delightful. He also plays the

piano very well.’ ‘I have grown very fond of Heisenberg’, he confided to

Sommerfeld, ‘he is liked and esteemed by us all. His talents are extraordinary,

but his friendly, modest attitude, his good spirits, his eagerness and

enthusiasm are especially pleasing.’ He described Heisenberg as looking like

a simple peasant boy, with short fair hair, clear bright eyes and a charming

expression.

The next year, after habilitating at G¨ ottingen at the unusually early

age of twenty-two, Heisenberg spent the summer vacation with friends from

the youth movement on a walking tour and then went to Copenhagen as a

research associate. He already knew how deeply Bohr understood the problems

of physics, and how much he could learn from him. Their discussions,

often conducted on walks in the countryside, also ranged over many other

fields of human life and affairs, and here Bohr’s wisdom and warmth made a

deep impression on his young disciple. They went on a walking tour of

Sjaelland, the island on which the Danish capital is situated. When he

returned the following year, Bohr wrote that ‘he is as congenial as he is

talented’ and ‘in spite of his youth he has succeeded in realizing hopes

of which earlier we hardly dared dream . . . in addition his vigorous and

harmonious personality makes it a daily joy to work together with him

towards common goals.’ Heisenberg later said that in Go¨ ttingen he learned

Werner Heisenberg (1901–1976) 347

mathematics, in Copenhagen physics. The affection and mutual respect

he and Bohr felt for each other continued to deepen over the next fifteen

years.

In 1925, at the age of twenty-three, Heisenberg wrote the paper that

laid the foundations of quantum mechanics on which subsequent generations

have built. This was not just an extension or elaboration of the work

of others, but an unexpected, radical new departure, which abandoned the

basic notions of the old classical physics, such as electrons moving in orbits,

replacing them by a much more abstract description. Less than a year later

Schro¨ dinger, as we know, published his theory of wave mechanics, which at

first appeared to be an alternative theory to Heisenberg’s. However, the two

theories turned out to be essentially the same. Schro¨ dinger’s mathematics

is in many ways easier to handle, but both points of view are needed in order

to develop a real understanding of the physical world.

In 1927 Heisenberg was offered chairs in both the Universities of

Leipzig and Zu¨ rich; he chose the former and became the youngest full professor

in Germany. At his first seminar he had an audience of two, but soon

students and other collaborators were attracted, and frequently senior visitors

attended. His duties were not light. It was then normal for the professor

to give the main undergraduate lectures in theoretical physics, usually on

a four- or six-semester cycle, and to set examinations on the course-work,

which he had to mark. There were also the usual faculty and committee

meetings, but, in spite of these demands on his time, Heisenberg was always

accessible to his students. He remained as before – informal and cheerful in

manner, almost boyish, with a modesty that verged on shyness. His weekly

seminar was preceded by tea, and for this he would go out to a nearby bakery

for some pastries. After a strenuous discussion, and during other free periods,

the whole group would descend to the basement and play table tennis.

Heisenberg was a very good player and could beat everyone else, until a

Chinese physicist arrived, who was equally skilful, if not more so.

Problems, difficulties and new ideas in physics were debated very

intensely. Heisenberg was able to help his students particularly through his

powerful intuition. Usually he did not pay too much attention to the mathematical

details of their work, as long as they could see where they were

going, but he needed to grasp the physics of their problem himself. Once he

had done so, he was usually able to guess the answer, and he was usually

right. Naturally Heisenberg’s own output of papers during this period did not

match the pace of previous years; a further distraction was a lecture tour

of the USA in 1929. Quantum mechanics was now essentially complete,

348 From Heisenberg to Yukawa

and the next task was to work out its consequences and to see how it

would explain the many mysteries, paradoxes and contradictions in atomic

physics. He found that it was an exhilarating experience to see how easily

the solutions to the old puzzles fell into place.

When Hitler seized power in Germany and the Nazi ideology took

hold in the universities, Heisenberg, like many other academics, was deeply

shocked by the anti-intellectual attitude of the regime. In a book of reminiscences,

published in 1969, he describes an imaginary conversation with

a student who is a leader of the Hitler Youth. One feels that, while formally

maintaining his refusal to have anything to do with Nazi gatherings and

other activities, he can see something to admire in the ideas of his companion.

The student himself deplores the anti-Semitism and other destructive

features of the movement, but insists that its essential aim is to create a

better world, to fight corruption and dishonesty, and to restore respect for

Germany.

However, the disastrous aspects of Nazi policies began to dominate

to such an extent that Heisenberg and a few colleagues soon started to talk

of resignation. He went to see Planck about this; his advice was to remain.

However many professors resigned, he said, it would not affect Nazi policy.

Heisenberg would have to emigrate, Planck went on, and while undoubtedly

he would find a position abroad, he would be taking it away from someone

else who was being forced to leave Germany. The present regime was bound

to end in disaster, Planck concluded, and after that happened people like

Heisenberg would be needed as leaders.

Many German physicists faced the same problem as Heisenberg; other

than those dismissed or expecting to be dismissed, hardly any decided to

leave. Of those who remained, von Laue was outstanding for his uncompromising

stand, his proud aloofness and his refusal to cooperate with the

regime. To have taken that position was not in Heisenberg’s character. In

referring to his attraction to military service, which involved annual training

as a reservist, he remarked that ‘it is nice not to have to think, for a

change, but only to obey’. He tried to carry on as before, to maintain the

old atmosphere, in spite of the loss of his Jewish colleagues; he commented

that he rather envied them, since they had no choice. This was not the only

occasion when he displayed amazing insensitivity to the effects of Nazi

persecution on individuals.

In 1933 Heisenberg was awarded the prestigious Max Planck medal of

the German Physical Society. No Nobel prize for physics had been awarded

in 1931; the 1932 prize had been deferred and now it was announced that

Werner Heisenberg (1901–1976) 349

this had been awarded to Heisenberg. Meanwhile the grip of the Nazis on

German science was steadily tightening. Visits by German scientists to

foreign countries required official approval, likewise visits by foreign scientists

to Germany. Although the Nazis had reservations about Heisenberg’s

political attitudes, his prestige was such that he was seldom if ever refused

permission to travel. Mainly through visits to Copenhagen, he kept in touch

with the latest ideas in physics.

In 1935 Heisenberg was proposed for the chair in Munich in succession

to Sommerfeld, who was retiring. This was an attractive opportunity, both

because it meant succeeding his respected teacher and particularly because

of his fondness for the city. However, the proposal was attacked by those who

opposed relativity and quantum theory as ‘Jewish physics’. The authorities

ruled against his appointment in favour of a nonentity. After this personal

attacks on Heisenberg became more virulent, until eventually instructions

from a high party level put an end to them and Heisenberg was appointed

after all.

By this time Heisenberg had found added strength and support; in

January 1937 he had made the acquaintance of Elisabeth Schumacher,

daughter of the great Berlin economist, and they were married three months

later. Although it was a successful marriage, Heisenberg always put his

career first. Twins, a son Wolfgang and a daughter Anna Maria, were born

in 1938; eventually there were to be seven children, all of whom shared

their parents’ love of music. Of the twins, Anna Maria Hirsch became a

physiologist while Wolfgang, a lawyer by training, worked for a foundation

concerned with science and politics. Jochen became an experimental physicist

at MIT while Martin became a professor of biogenetics. Barbara Blum

married a physicist. Christine Mann became a teacher and her husband a

physiologist. The youngest, Verena, became a technician in a physiology

laboratory.

By the summer of 1939, when it was clear that war was inevitable,

Heisenberg purchased a country house at Urfeld, in the Bavarian Alps, as

a refuge for his family (there were at this stage three children) in case of

need. He revisited the USA and lectured at the universities of Michigan and

Chicago, where many of his old friends and colleagues tried to persuade him

to leave Germany because of the impending disaster, in which his presence

could not achieve anything. However, Heisenberg did not agree; above all, he

believed that leaving would be disloyal to the young people in his research

group, who would rely on him for guidance in keeping science going and

whose responsibility it would be to rebuild science after the war. These

350 From Heisenberg to Yukawa

young people could not find positions abroad as easily as he could, and he

would feel that he was taking an unfair advantage.

When the war came, Heisenberg was appointed chief technical consultant

for research on nuclear fission after being excused normal military service

on medical grounds. For the next five and a half years this took up most

of his time and energy. He developed the theory of a nuclear reactor. Experiments

indicated that a system of uranium metal and heavy water of suitable

size could sustain a chain reaction. A successful experimental reactor could

have been constructed, but much more time would have been needed to produce

anything of practical value. The type of reactor the American physicists

constructed had been dismissed as impracticable because Heisenberg had

miscalculated the critical mass required; since atomic research was everywhere

top secret by this time, mistakes were liable to remain uncorrected.

It has been suggested that Heisenberg deliberately made the production of

an atomic bomb appear impracticable, because he did not want the Nazis to

have such a weapon, but the evidence for this is unconvincing. As regards

atomic energy, for Germany this was a long-term project and unlikely to

affect the outcome of the war.

Heisenberg had reported as early as December 1939 that, although

energy could be generated from ordinary uranium if it were used in conjunction

with heavy water or graphite to slow down the neutrons, it would

be necessary to use enriched uranium-235 to produce an explosive. These

two lines of attack became the chief objectives of the German atomic-energy

programme and for a year or two progress was remarkably rapid, in spite of

rather lukewarm official backing. Heisenberg was at first a consultant to

the Kaiser Wilhelm Institute for physics in Berlin-Dahlem, where much of

the research was being done, and during that time he continued to live in

Leipzig, where some unrelated work was being done at the physics institute.

The Kaiser Wilhelm Institute had been placed under military control

but, after reorganization, in 1942 it was returned to the Kaiser Wilhelm

Gesellschaft and Heisenberg was appointed Director. He was also appointed

full professor at the University of Berlin and elected to the Berlin Academy.

When he moved to the German capital in the spring of 1943, his family

went to live in their country house in Urfeld, but later that year, when the

air raids became more intense, the laboratory was evacuated to Tailfingen.

Several reactor experiments were set up but none actually achieved

criticality; indeed, the final experiment under Heisenberg’s control was carried

out only a few weeks before the arrival of Allied troops. It came close

to being critical and it became clear that a small increase in scale would

Werner Heisenberg (1901–1976) 351

achieve that state, but time was running out; the end of the war was near

and there could be no chance of practical results before then. It was not

known in Germany that Fermi had already achieved a chain reaction in

Chicago three years earlier.

As soon as Germany had fallen to the Allied forces, an Anglo-

American team searched Heisenberg’s office and other places where work

on the nuclear project might have been carried out, and concluded that the

Germans had got nowhere near producing a bomb. However, to avoid the

risk that the German nuclear physicists might be taken to the Soviet Union,

ten of them, including Hahn and Heisenberg, were rounded up and escorted

to Britain, where they were interned in Farm Hall, a pleasant manor house

in the Cambridgeshire village of Godmanchester. Although they were still

under guard, the internees enjoyed a good deal of freedom. Their rooms were

bugged and it was hoped to learn from their conversations something about

secret research in Germany, especially research into atomic energy. It was

there that they heard in August 1945 the news of the atomic bomb used

against Japan and realized that the Americans were far ahead. The German

scientists were not only amazed that this revolutionary weapon of destruction

had been produced but also mystified as to how it had been possible.

Why did Heisenberg work for his country on atomic energy, and why

was the total achievement of the German project so slight? As regards the

first question, Heisenberg was a patriot, technically in the army, and wanted

Germany to win the war. It might have been different if the work had come

close to making an atomic bomb, but it did not. He wrote ‘We knew then

that one could in principle make atomic bombs, and knew a realizable process,

but we regarded the necessary technical effort as rather greater than

in fact it was.’ As regards the other question, the basic reason for the slow

progress was that the work was not pursued with urgency. The authorities

never instructed their scientists to make an all-out effort and did not give

them the support and services such an effort would have required. Even

the USA, with far greater industrial resources, without serious shortages

and without interruption by air raids, was not able to make atomic bombs

until after the end of the war in Europe. Also, to generate electricity by

atomic energy was hardly a top priority in war-time. Moreover, there were

errors, misjudgements and omissions, both in the scientific work and in the

organization and planning

Although the subsequent German work on atomic energy was not

in the short term aimed at producing weapons, Heisenberg and his colleagues

were aware of the fact that they were working on a programme that

352 From Heisenberg to Yukawa

could lead to that result. For example, a nuclear reactor, intended to produce

power, could be converted into an explosive device. They decided to

consult Niels Bohr, and in October 1941 Heisenberg went to Copenhagen;

by this time Denmark was under German occupation, and the visit was by

no means welcome. Just what was said is disputed, but it seems clear that

they parted with Bohr so angry that he never forgave Heisenberg.

After the war, Heisenberg cited the meeting as evidence of his reluctance

to help Hitler create the ultimate weapon of mass destruction. The

purpose of his visit to Copenhagen, he suggested, was to share his qualms

over nuclear weapons. In Bohr’s recollection, on the other hand, Heisenberg

said that ‘There was no need to talk about details, since you were completely

familiar with them and had spent the past two years working more or

less exclusively on such preparations.’ He concluded that under Heisenberg

everything was being done in Germany to develop atomic weapons.

Either account could be inaccurate. Bohr was known as being better at

talking than listening, and he could have misunderstood what Heisenberg

said to him. Of course, Bohr was a citizen of a peaceful country, occupied

without provocation by the armies of a hateful regime, and Heisenberg,

although an old friend and disciple, was also a citizen of the occupying

power. Soon after Heisenberg’s visit the Germans occupied the Bohr Institute

and, as we know, the Jewish or partly Jewish members, including Bohr

himself, fled the country. There was a plan to appoint Heisenberg as director

and staff it with German scientists, so as to coerce the remaining Danish

scientists into contributing to the German war-effort. Heisenberg succeeded

in preventing this happening.

In the autumn of 1943 Heisenberg visited occupied Holland. During

the visit he took a walk with an old friend and colleague from Copenhagen,

in which Heisenberg began to talk about history and world politics. He

explained that ‘It had always been the historical mission of Germany to

defend the West and its culture against the onslaught of eastern hordes and

the present conflict was one more example. Neither France nor England

would have been sufficiently determined and sufficiently strong to play a

leading role in such a defence, and so, perhaps, a Europe under German

leadership might be the lesser evil.’

At the end of the war in Europe, German scientists were dispersed,

laboratories were closed and many of the cities in which they were located

were severely damaged. The Allied armies which had occupied the country

were trying to get life back to normal. In the British zone, at least, the policy

was to encourage the leading German scientists to resume their research and

Paul Dirac (1902–1984) 353

teaching. With their agreement, G¨ ottingen was chosen as the best place to

serve as the centre for the rebuilding of scientific research. They gathered

there, under the auspices of what was now the Max Planck Gesellschaft. At

first this functioned only in the British zone, but after a time it was able to

extend its activities over the whole of Western Germany.

During the Go¨ ttingen period Heisenberg devoted much of his time

and energy to questions of the future organization of science in the Federal

Republic. He made a major contribution to the decision to start a nuclearreactor

programme. Whereas he pleaded strongly in favour of nuclear power,

he opposed, equally strongly, any suggestion that Germany should make or

acquire atomic bombs. In the autumn of 1958 the Max Planck Institute

for physics and astrophysics, which Heisenberg had directed in Go¨ ttingen,

moved to Munich and he was able to return to the city he had always loved.

He remained director of the institute until his retirement in 1970. After

that most of his writings were reviews or essays of a general nature; his

reputation outside Germany was clouded by his failure to explain his wartime

record satisfactorily. Five years later his health began to decline, and

he died of cancer on February 1, 1976, at the age of seventy-four.

Heisenberg was undoubtedly a great physicist, the creator of quantum

mechanics. Nevertheless, the account he gave of his work during the

war, and his justification for it, are open to question; the whole truth may

never be known, but there is considerable evidence to suggest that he would

have regarded it as his patriotic duty to organize the production of atomic

weapons, which might have affected the outcome of the war. When it was

clear that Germany was going to be defeated, he told a Swiss colleague that

‘It would have been so sweet if we had won.’

Paul Dirac (1902–1984)

Paul Dirac was a theoretical physicist in the same class as the best in Europe;

according to Bohr he had the purest soul of them all. He contributed as much

as anyone to the establishment of the new science of quantum mechanics.

Between the ages of twenty-three and thirty-one he unveiled an original

and powerful formulation of the theory, a primitive but important version

of quantum electrodynamics, the relativistic wave equation of the electron,

the idea of antiparticles and a theory of magnetic monopoles.

The future physicist was born on August 8, 1902 in Bishopston, a

suburb of the city of Bristol. His mother Florence (n ´ee Hilton), the daughter

of a ship’s captain, came from Liskeard in Cornwall. His father Charles

was brought up in the French-speaking Valais region of Switzerland but

354 From Heisenberg to Yukawa

emigrated to England in the 1880s and supported himself by giving French

lessons. They had three children, the eldest being Reginald, who was two

years older than Paul, and the youngest Beatrice, four years younger. All

three were registered at birth as Swiss citizens, but they and their father

relinquished Swiss citizenship and became British in 1919. Although he

had lost touch with his own parents, who were originally French, Charles

wished his children to speak French at home and speak it correctly. ‘My

father made the rule that I should only speak to him in French’, recalled

Paul later on. ‘He thought it would be good for me to learn French in that

way. However, since I found I couldn’t express myself in French, it was

better for me to stay silent than talk in English. So I became very silent

at that time – that started very early.’ His mother, who had worked in the

library of Bristol University before marriage, could hardly speak French at

all and so she usually took meals separately with the other children.

From 1896 Charles had been teaching in the Merchant Venturers

Technical College in Bristol; after this was taken over by Bristol University,

part of it was hived off to become a secondary school, which was where

Charles now taught French. He had the reputation of being exceptionally

strict in class. He was an outstanding linguist, able to speak eight or nine

Paul Dirac (1902–1984) 355

languages, and an enthusiast for Esperanto. Although he cared about his children

and their future careers, he succeeded in alienating his sons. Reginald,

the elder, wanted to be a doctor; his father Charles made him study mechanical

engineering. After graduating from Bristol University with a third-class

degree, Reginald took a job as a draughtsman at an engineering works, but

gave it up and three months later committed suicide at the age of twentyfour.

Paul’s relations with his father were always chilly. After he grew up

they had little personal contact, although Charles was proud of his son’s

success and tried to understand what he did. When Paul was awarded the

Nobel prize and was told that he could invite his parents to attend the ceremony

in Stockholm, he chose to invite only his mother. He rarely visited

Switzerland, because he associated it so much with his father. As a young

man Paul never had a girl-friend and seems to have had a rather platonic

conception of the opposite sex for some time. He confided to a friend:

‘I never saw a woman naked, either in childhood or in youth . . . The

first time I saw a woman naked was in 1927, when I went to Russia with

Peter Kapitza. She was a child, an adolescent. I was taken to a girls’ swimming

pool, and they bathed without swimming suits. I thought they looked

nice.’

Paul’s mathematical ability became apparent even at primary school.

He went on from there to the college where his father taught, at the age

of twelve. Although the academic standards there were high, the teaching

had a vocational orientation. Modern languages were taught for use,

metal work was in the syllabus, as was shorthand, but classics and literature

were not. However, the school was particularly strong in mathematics

and science. Paul was soon so far ahead of his class in mathematics that

he was allowed to work largely on his own. He was recognized as a boy of

exceptional intelligence; Paul’s schoolfellows remember him as silent and

aloof.

After leaving school in 1918, Dirac entered Bristol University, where

he studied electrical engineering. In 1921, after graduating, he looked without

success for work as an engineer. He won an exhibition to St John’s

College, Cambridge, but did not take it up because he could not afford

the additional expense of being a Cambridge undergraduate. Then he was

offered two years’ free tuition by Bristol University to return and study

mathematics, where, unlike at Cambridge, he would be able to economize

by living at home. This he accepted and, after a brilliant performance in

the final examination, was awarded a government grant that enabled him

356 From Heisenberg to Yukawa

to go up to Cambridge as a graduate student. Two years later he was given a

more generous award from the Commissioners for the 1851 Exhibition. At

Cambridge his research supervisor was Rutherford’s son-in-law Ralph

Fowler, who recognized in Dirac a student of exceptional ability. Before

long Dirac was publishing research, first on statistical mechanics and

then on quantum mechanics. At that time the Bohr–Sommerfeld quantum

theory was the best available theory of atomic phenomena, but it had many

shortcomings and contradictions. He attempted to find ways of improving

it, but without success.

Dirac first met Bohr in May 1925 when the latter gave a talk in

Cambridge on the fundamental problems and difficulties of quantum

theory. He said later that ‘people here were pretty much spell-bound by

what Bohr said . . . while I was very much impressed by him his arguments

were mainly of a qualitative nature, and I was not able really to pinpoint

the facts behind them. What I wanted was statements which could

be expressed in terms of equations, and Bohr’s work very seldom provided

such statements.’ In the summer of 1925 Heisenberg came to address the

Kapitza Club, which had become the unofficial Cambridge forum for discussing

modern physics. Afterwards Dirac said that he did not remember

him talking about the new ideas in his great paper that laid the foundations

of quantum mechanics; the subject of his talk was something less

exciting. However, when Fowler received the proofs of the paper on quantum

mechanics and showed them to Dirac, he soon realized its revolutionary

significance.

Dirac’s first paper on quantum mechanics, the basis for his Ph.D.

thesis of 1926, paralleled much of what was being done at the same time

elsewhere, but he followed it up with more innovative work that immediately

attracted the attention of theoreticians everywhere. Born was about

to leave on a visit to America when ‘The day before I left there appeared a

parcel of papers by Dirac, whose name I had never heard . . . Never have I

been so astonished in my life: that a completely unknown and apparently

young man could write such a perfect paper.’ Fowler arranged for Dirac to

spend some time first in Copenhagen and then in Go¨ ttingen and Leiden. He

enjoyed the informal and friendly atmosphere of the Bohr institute and had

many long conversations with the Great Dane: ‘I admired Bohr very much.

We had long talks together, very long talks in which Bohr did practically all

of the talking.’ While respecting Bohr greatly for his depth of thought, he

said he did not know that Bohr had any influence on his own work because

Bohr tended to argue qualitatively, while Dirac was more mathematical. At

Paul Dirac (1902–1984) 357

Go¨ ttingen he got to know Robert Oppenheimer, at the time a Ph.D. student,

while at Leiden he mainly worked with Ehrenfest.

In 1927 St John’s elected Dirac to a fellowship, after which he lived

and worked in college. In the same year he was invited to the sixth Solvay

conference, where he made important contributions to the discussion and

had the opportunity of meeting Einstein and Lorentz. In 1930 he was elected

to the Royal Society at the unusually young age of twenty-eight. He spent

much of the following year at the Institute for Advanced Study in Princeton

and, soon after returning to Cambridge, he was elected Lucasian Professor

of mathematics; his teacher Fowler had been elected Plumerian Professor

of mathematical physics the previous year. Sadly, his extreme rationalism

now led Dirac into sterile byways after his amazingly successful early years.

Few of his later contributions to physics had lasting value, and none had the

revolutionary character of his earlier work.

In 1933 Dirac and Schro¨ dinger shared the Nobel prize for physics ‘for

the discovery of new productive forms of atomic theory’. At first Dirac was

inclined to refuse it because he so hated publicity, but changed his mind

when Rutherford warned him that a refusal would attract even greater publicity.

At the seventh Solvay conference Dirac gave a talk on ‘Structure

and Properties of Atomic Nuclei’. He liked to travel, and often went to

the Soviet Union to see his friend Kapitza. In the academic year 1934/5,

when he was on leave from Cambridge, Dirac returned to Princeton, mainly

to revise his classic textbook The Principles of Quantum Mechanics for a

second edition. There he developed a close friendship with Eugene Wigner,

whose sister Margit Balasz was visiting from Budapest at the time. Her

temperament was quite unlike Dirac’s, spontaneous and impulsive, with

strong likes and dislikes. There was an attraction of opposites, and in

January 1937 they were married in London. From then until he retired

in 1969 the Diracs lived in a house in Cavendish Avenue, Cambridge.

The household included two children, a son and a daughter, from Margit’s

first marriage, both of whom took the name of Dirac, and two daughters

from the second marriage; later Dirac’s mother Florence came to live

with them.

There are many stories about Dirac’s personality, usually related to his

taciturnity, for which he was inclined to blame his father, perhaps unfairly.

Heisenberg, who knew Dirac well, recalled that ‘We were on the steamer

from America to Japan and I liked to take part in the social life on the

steamer and so, for instance, I took part in the dances in the evening. Paul,

somehow, didn’t like that too much but he would sit in a chair and look at

358 From Heisenberg to Yukawa

the dances. Once I came back from a dance and took a chair beside him and

he asked me “Heisenberg, why do you dance?” I said “Well, when there are

nice girls it is a pleasure to dance.” He thought for a long time about it and

after about five minutes he said “Heisenberg, how do you know beforehand

that the girls are nice?”’.

Although he was not much interested in teaching, Dirac seems to have

had some success as a research supervisor. Among the doctoral students who

were supervised by him, the mathematician Harish-Chandra stands out.

As for Dirac’s lectures, one who attended his regular course on quantum

theory recalled that ‘The delivery was always exceptionally clear and one

was carried along in the unfolding of an argument which seemed as majestic

and inevitable as the development of a Bach fugue.’ Dirac was an inveterate

traveller and, although not a serious mountaineer, he climbed some high

mountains, notably Mount Elbruz in Turkey, which brought on an attack

of altitude sickness.

Until he retired Dirac based himself in Cambridge, except for extended

visits to the Institute for Advanced Study in Princeton, the Tata Institute for

Fundamental Research in Bombay and Moscow State University. Although

he had attractive offers from elsewhere, he chose to remain in England, so

as to give a lead to young British theoreticians, until in 1972 he crossed the

Atlantic and took on a new lease of life at the Tallahassee campus of Florida

State University. In Cambridge he tended to work mainly at home and went

to the university only for classes and seminars; in Tallahassee he was on the

campus all day. He published prolifically, over sixty papers during the last

twelve years of his life, although they were not research papers. Gradually

his health failed and he died at Tallahassee on October 20, 1984.

Dirac refused all honorary degrees, but among the honours he

accepted, apart from the Nobel prize, perhaps the Copley and Royal medals

of the Royal Society and the Order of Merit should be singled out. There are

several paintings of him and several portrait busts. ‘Dirac was tall, gaunt,

awkward and extremely taciturn’, wrote a German scientist after his death,

‘he has succeeded in throwing everything he has into one dominant interest.

He was a man, then, of towering magnitude in one field, but with little

interest and competence left for other human activities. In other words he

was the prototype of the superior mathematical mind; but while in others

this has coexisted with a multitude of interests, in Dirac’s case everything

went into the performance of his great historical mission, the establishment

of the new science quantum mechanics, to which he probably contributed

as much as any other man.’

J. Robert Oppenheimer (1904–1967) 359

J. Robert Oppenheimer (1904–1967)

In America the study of physics was slow to develop. There were outstanding

individuals at times, such as Henry, Gibbs and Millikan, but it was not

until after the Second World War that the USA became the world leader in

physical research, with immigrants from Europe and elsewhere setting the

standard for native-born Americans to attain. More than anyone else it was

Oppenheimer who was responsible for raising American theoretical physics

from the state of being little more than a provincial adjunct of Europe to

world leadership.

J. Robert Oppenheimer was born on April 22, 1904 in New York; the

letter J. in his full name may refer to his father Julius, who had come to

the USA from Germany at the age of seventeen and developed a prosperous

business importing textiles. Oppenheimer’s mother Ella (n ´ee Friedman)

came from Baltimore. She was said to have been unusually sensitive, and had

studied painting in Paris. Robert had one younger brother, Frank Friedman

Oppenheimer, born in 1912, who became professor of experimental physics

at the University of Colorado: he also had another brother who died in

infancy. The family was well-off, with a sumptuous apartment on Riverside

Drive in Manhattan, furnished with post-impressionist paintings, and

an estate on Long Island, where they kept a yacht. They were non-observant

Jews, much interested in art and music.

360 From Heisenberg to Yukawa

In 1911 the young Oppenheimer entered the non-sectarian School of

Ethical Culture, one of the best in the city of New York, where he joined a

large number of other Jewish boys who were excluded from private schools

through the rigid quota system. He received an education in what, for those

days, were advanced liberal concepts of social justice, racial equality and

intellectual freedom. Being very shy, he was much bullied and, rather than

mixing with other boys, immersed himself in his schoolwork, in poetry and

in science, particularly physics and chemistry. When he was only five he

had started collecting mineralogical specimens, some of which came from

his grandfather in Germany. By the time he was eleven his collection was so

good and his knowledge so extensive that he was admitted to membership

of the Mineralogical Club of New York.

After graduating from school in 1921, Oppenheimer made a trip to

Europe, but became sick with colitis. He entered Harvard the next year, just

after the university had introduced its quota system for admitting Jewish

students, the intention being to restrict them to the same proportion as

obtained in the population as a whole. Originally he had intended to major

in chemistry, but soon switched to physics. It was characteristic of him not

to abandon a subject in which he had once been interested; familiarity with

chemistry was to be very useful to him later on in his career. At Harvard he

was strongly influenced by Percy Williams Bridgeman, a distinguished and

unconventional experimental physicist. Apart from this, he kept very much

to himself and devoured knowledge avidly. ‘I had a real chance to learn’, he

said, ‘I loved it. I almost came alive. I took more courses than I was supposed

to, lived in the library stacks and just raided the place intellectually’. In

addition to studying physics and chemistry, he learned Latin and Greek and

graduated summa cum laude in 1925, having taken three years to complete

the normal four-year course. He retained a lifetime affection for Harvard,

serving as a member of the Board of Overseers from 1949 to 1955.

After graduation from Harvard, Oppenheimer spent four years studying

at the great European centres of physics. First he spent the academic

year 1925/6 as a member of Christ’s College, Cambridge. After having been

turned down by Rutherford, he was assigned a rather uninspiring research

project and altogether he was generally unimpressed by Cambridge. His parents

came over to see him, having heard that he was having treatment for

depression. It was rather a disappointing year, but at least he reached the

conclusion that he preferred theoretical physics to experimental physics

and decided that he would do his doctoral work at G¨ ottingen, under Born.

While at Cambridge he had begun a thesis on the application of quantum

J. Robert Oppenheimer (1904–1967) 361

theory to transitions in the continuous spectrum, which he completed so

rapidly that it was ready for submission early in 1927. At the same time he

was building up his knowledge of the revolutionary new developments in

theoretical physics.

Next Oppenheimer was awarded a Rockefeller-funded fellowship by

the American National Research Council, later the National Science Foundation.

He held it first at Harvard and then at the California Institute of

Technology, presided over by Millikan. In the year 1928/9 he held a fellowship

from the International Education Board and used it to visit Ehrenfest

in Leiden and to see Bohr’s disciple Kramers in Utrecht. In the first half of

1929 he went on to the ETH in Zu¨ rich, where he worked with Pauli, another

influence on his scientific development.

On his return to the USA in 1929, Oppenheimer received many offers

of academic positions. He accepted two of them, becoming assistant professor

of physics concurrently at the California Institute of Technology and

at the Berkeley campus of the University of California. In the ensuing thirteen

years he divided his time between the two institutions, spending the

autumn and winter in Berkeley, the rest of the year in Pasadena. The majority

of the best American theoretical physicists who matured in those years

were trained by him at one stage or another in their careers. His teaching,

his style and his example influenced them all.

Oppenheimer was fortunate to enter physics in 1925, just when modern

quantum physics came into being. Although he was too young to take

part in its formulation, he was one of the first to use it for the exploration

of problems that had defeated the old quantum theory. Probably the most

important ingredient he brought to his teaching was his ability to choose the

most interesting problems. Although his lectures were difficult, they conveyed

so well the beauty of the subject that almost every student repeated

his course, which was based on the survey by Pauli in the Handbuch der

Physik. He was interested in almost everything, but principally quantumfield

theory, cosmic rays and nuclear physics.

The magnetism and force of Oppenheimer’s personality was such that

his students tended to copy his gestures and mannerisms; he had exquisite

manners, a marvellous command of language and a ready wit. In those days

students were generally short of money; he entertained them generously,

to concerts, dinners and other social events. Among his many friends in

the Berkeley faculty were not only scientists but also classicists, artists

and so on. Most of the time he was indifferent to the events taking place

around him. He never read a newspaper or listened to the radio; he never

362 From Heisenberg to Yukawa

used the telephone. However, he had a passion for fast cars and particularly

enjoyed racing trains when the railroad track ran alongside the highway. He

was described as having titanic ambition but was tortured by self-doubt. In

1936 he was promoted to full professor at both of the institutions where he

worked. The following year his father died; his mother had died six years

earlier. In 1941 he was elected to the National Academy of Sciences. In 1940

he married the divorc´ee Katherine (Kitty) Harrison; they had one son, Peter,

and one daughter, Katherine.

In 1942, after America had entered the Second World War, Oppenheimer

was appointed leader of the theoretical side of the effort to design

and build an atomic bomb. Research in England had made it seem very likely

that the concept was viable. The chemical firm Dupont was contracted to

build a production reactor, and it was time to prepare for the assembly of

an atomic weapon. A permanent laboratory was needed for the work, somewhere

remote because of the need for secrecy. For many years Oppenheimer

and his brother had rented a ranch in the high country of the state of New

Mexico, where they loved to spend their summers horseback riding. The

government established its laboratory on a beautiful mesa nearby, called

Los Alamos. Oppenheimer, as director of the enterprise, set about recruiting

his team. Many of the best physicists were already involved in war work

and disinclined to move, but he was very persuasive and those who came

to join him found it an unforgettable experience.

The task they were faced with was formidable. Initially not much

more was known than the fundamental theory behind a chain reaction.

The details of the fission process had to be fully understood, but no fissionable

material was yet available. Nuclear physicists found themselves dealing

with unfamiliar subjects, like hydrodynamics, but Oppenheimer kept

morale high and not only led the physicists but also argued against the tendency

of the military to impose security measures the scientists regarded as

excessive; for example, they had to use false names. The preparatory work

was completed in 1945, at just about the time that a sufficient amount of the

isotope uranium-235 became available. In 1946, at the end of it all, Oppenheimer

was awarded the Medal of Merit by President Truman, ‘for his great

scientific experience and ability, his inexhaustible energy, his rare capacity

as an organizer and executive, his initiative and resourcefulness, and his

unswerving devotion to duty’.

It was obvious that a community like Los Alamos would be deeply

concerned with the ominous implications of the atomic bomb. Oppenheimer

was one of those most concerned, and had many discussions about

J. Robert Oppenheimer (1904–1967) 363

this problem with Bohr amongst others. Bohr had come to the USA in 1944

as a consultant on the project, but his main interest was in talking to statesmen

and trying to persuade them that international control was the only

way to avoid a pernicious arms race or worse, atomic war. Bohr did not get

far with the statesmen but he greatly impressed Oppenheimer and through

him other scientists. In 1949, after the Soviet Union had exploded its first

atomic bomb, the chances of any international agreement receded, and the

scientists had little influence on the arms race which then developed.

In 1945 Oppenheimer resigned as director of the Los Alamos laboratory

while remaining on a number of major national and international

committees concerned with atomic energy. He returned to California briefly

to resume his professorships. In 1948 he was president of the American

Physical Society, and the following year he was appointed as both professor

of physics and director of the Institute for Advanced Study in Princeton. Not

all the permanent members of the institute supported his appointment, and

he was not universally popular. He arrived with an armed guard carrying a

large safe containing secret documents, and much of his time and energy

was spent working in Washington.

During the Cold War a notorious witch-hunt took place in the USA,

when many prominent people were accused, rightly or wrongly, of being

Communists or crypto-Communists and therefore not to be trusted with

secret information. Oppenheimer was a known left-winger. Although his

brother and sister-in-law both joined the Communist Party, apparently he

never did so himself. Nevertheless, at the end of 1953 President Eisenhower

ordered that his clearance for secret government work should be suspended.

The ensuing protracted security investigation became a cause c´ el `ebre. Many

of his fellow-scientists came out in his defence, but he had made powerful

enemies who testified against him. The decision was upheld, and it was

not until eight years later that the American government made amends.

When President Johnson, carrying out a decision made by the late President

Kennedy, presented him with the prestigious Enrico Fermi award at the

White House, Oppenheimer commented: ‘I think it is just possible, Mr

President, that it had taken some charity and some courage for you to make

this award today.’

Under Oppenheimer theoretical physics at the Institute for Advanced

Study was strengthened, to some extent at the expense of mathematics.

The institute faculty had always included prominent physicists; Einstein

as a permanent member, Bohr, Dirac and Pauli, amongst others, as visitors,

but now younger physicists were increasingly encouraged to visit, as well

364 From Heisenberg to Yukawa

as those who were already eminent. Although he was never quite in the

top rank of researchers himself, Oppenheimer could still conduct a lively

seminar and play a leading and often critical role in the vigorous discussion

which usually followed the talk. His own writings and lectures, after the

war, were more concerned with the problems of the human race than with

physics as such; increasingly he performed the twin roles of public symbol

and interpreter of modern physics. Among the many foreign honours he

received were membership of the Legion of Honour and the fellowship of

the Royal Society. A heavy smoker, Oppenheimer died of throat cancer in

Princeton on February 18, 1967, after having taken early retirement the

previous year.

Maria Goeppert-Mayer (1906–1972)

Regrettably, only three of my remarkable physicists are women. The handicaps

that Marie Curie and Lise Meitner faced have already been described;

those that Maria Goeppert had to deal with, several decades later, were different

but equally discouraging. Maria Gertrude Kate Goeppert was the only

child of well-educated upper-middle-class parents. She was born on July 28,

1906, in what was then the German city of Kattowitz in Upper Silesia, and

Maria Goeppert-Mayer (1906–1972) 365

is now the Polish city of Katowice. Her mother Maria (n ´ee Wolff) taught

French and music before her marriage. Her father, Friedrich Goeppert, who

was professor of medicine at the university with a special interest in paediatrics,

took special pride in being the sixth straight generation in a family of

university professors; later his daughter would be proud to have continued

the family tradition. Friedrich Goeppert encouraged his daughter’s natural

curiosity and adventurousness, and made it clear that he would like her to

be more than simply a housewife. She later said that she found her scientific

father more interesting than her mother, yet she was devoted to her mother,

who delighted to entertain faculty members at lavish dinner parties and to

provide a home filled with flowers and music for her only daughter.

Maria Goeppert was blond, with blue eyes, very earnest and unguarded

in her expression, who learned the importance of duty while young and presented

a reserved, somewhat aristocratic bearing as an adult. As a child she

was described as active, adventurous and tense. She suffered from severe

headaches and minor illnesses during childhood, perhaps exacerbated by her

parents’ high expectations. In 1910, when she was four, the family moved

to Go¨ ttingen, where her father had been appointed professor of paediatrics

at the Georgia Augusta. They had Hilbert as a neighbour, and their social

circle included many of the scientists of the great university. The public

schools of Go¨ ttingen had very good teachers; she excelled at languages and

mathematics. To prepare for the Abitur she completed her school education

at the Frauenstudium, a small private school run by suffragettes to prepare

girls for higher education: unfortunately, before she could finish the threeyear

course it was closed due to hyperinflation. Rather than change schools

again, she chose to take the Abitur a year earlier than normal. After passing

this successfully, she entered the Georgia Augusta in 1924 to major in

mathematics. Like most of the women students, she began by studying for

the teaching certificate, but found the classes uninteresting. She considered

medicine, but her father argued against it, fearing that she would suffer too

much distress whenever a patient died.

The Georgia Augusta had long been famous for mathematics and was

becoming so for theoretical physics as well. In 1927, inspired by the lectures

of Max Born, Maria Goeppert switched to physics. That year her father,

whom she idolized, died unexpectedly and, knowing what he would have

wished, she honoured his memory by resolving to complete her doctorate,

as a student of Born. She also spent a term in Cambridge, at Girton College,

primarily to learn English, but she was also able to meet the Rutherfords. She

was described as the prettiest girl inG¨ ottingen, rather short and plump, with

366 From Heisenberg to Yukawa

blue eyes and a fine-grained complexion. Her widowed mother, in accordance

with a G¨ ottingen tradition, began taking young people from the university

as boarders in her substantial house: one was a post-doctoral student

in chemistry from California named Joseph Mayer, the son of an Austrianborn

engineer and an American schoolteacher. He and Maria became great

friends and in 1930 they married. The same year she completed her doctoral

dissertation ‘On Elemental Processes with Two Quantum Jumps’. This was

a theoretical treatment of two-photon processes, which she later used to

determine the probability of double beta decay.

Meanwhile her husband had obtained a position as assistant professor

of chemistry at Johns Hopkins University and so the couple moved to

Baltimore. At that time universities were rather hesitant to hire women

for academic positions. Prejudice against women scientists began to recede

as the twentieth century progressed, but prejudice remained. In America

many universities had ‘anti-nepotism’ rules, preventing husband and wife

both holding academic positions in the same institution, and Johns Hopkins

was one of these; there was no chance of an academic post for her there. Since

no-one was working on quantum mechanics at Johns Hopkins, on Born’s recommendation

she collaborated in research with the physical chemist Karl

Herzfeld, who was working on energy transfer and the liquid phase, and

published some papers with him and with her husband. However, physical

chemistry was not her chosen field and during the summers she returned

to Go¨ ttingen, where she wrote several papers with Max Born on beta-ray

decay.

She found it difficult to adjust to life in America and was homesick for

Germany. By marrying an American she had forfeited her German nationality

and become for a time stateless, which created various bureaucratic

problems. In the spring of 1933 she took out American citizenship, calling

herself Maria Goeppert-Mayer professionally, Maria Mayer otherwise. Her

first child, Maria Ann, was born that year, the second, Peter Conrad, five

years later. Although both children initially studied science in college, they

did not pursue it further. The family lived in a large house, with an attractive

garden, where they entertained streams of German visitors. Before their

son was born her husband was appointed to a much-better-paid position as

associate professor of chemistry at Columbia University and so they moved

to New York, where she collaborated with him on a textbook, Statistical

Mechanics, published in 1940, which became a classic. Unfortunately, it

was assumed that her husband had done most of the work on this, so she

did not receive her due credit, a common experience for married women.

Until the USA entered the Second World War she was never on the payroll

Maria Goeppert-Mayer (1906–1972) 367

of an American university. Later she worked for the Manhattan project and

participated actively in efforts to help the German refugee scientists. Her

feelings about the war were ambivalent, due to her German roots and love of

family, friends and colleagues in the land of her birth. She told her children

that the war was against the Nazis, not the German people. Some of the

other German scientists in exile felt differently about the homeland which

had rejected them, but she continued to love Germany and the Germans

and to insist that Hitler was an aberration.

At the end of 1941 Goeppert-Mayer took a part-time teaching position

at Sarah Lawrence College in Bronxville, New York, where she developed a

unified science course. A few months later she joined the secret project to

separate the isotope uranium-235 from uranium-238, and she also worked

with Edward Teller on nuclear fusion. When the first atomic bombs were

dropped on Japan, with such devastating results, she was relieved that her

part in their development had been very minor. After the war Joseph Mayer

moved to the University of Chicago, where she was offered an associate

professorship but without salary, due to anti-nepotism rules, and she joined

the research group at the Argonne National Laboratory as senior physicist,

the first time she held a normal scientific post. The Mayers lived in a handsome

old house on the South Side of the city, ideal for entertaining. Like her

mother she had a flair for this. She filled their house with flowers, often from

their own garden. She specialized in cultivating orchids in a greenhouse on

the top floor of their house.

Her collaboration with Teller on the origin of the chemical elements

led to considerations of their relative abundance. She noticed that the most

stable elements contained particular numbers of either protons or neutrons,

later called the ‘magic numbers’. Shell models for the nucleus had been

considered and discarded earlier, but Goeppert-Mayer believed that new

evidence strongly supported this concept. In 1948 she published a paper

that set out the evidence but without a theory. A chance remark by Fermi,

who was keenly interested in her work, triggered the insight that enabled

her to solve the theoretical problem. By assuming the occurrence of spin–

orbit coupling, she was able to calculate the energy levels that matched

the magic numbers. Always impeccably correct in her behaviour towards

others, she delayed publishing her results because she had heard that several

other physicists were working on shell models in the USA. As it turned out,

it was a group in Heidelberg that published a similar interpretation to hers,

at about the same time as she did; later she co-authored a book on the subject

with one of them, Hans Jensen, a ‘dear gentle man’ but rather inclined to

procrastinate. It is said that through Bohr he provided information about

368 From Heisenberg to Yukawa

the progress of German research into atomic weapons that was useful to

the Allies.

During the war Goeppert-Mayer, an inveterate chain-smoker, began

to experience health problems. In 1956 she lost most of the hearing in one

ear. In 1959 both she and her husband were appointed to full professorships

at the new San Diego campus of the University of California, although they

were under pressure to remain in Chicago. A stroke in 1960, not long after

the move to La Jolla where the campus is located, left her partly paralysed,

but she continued to carry on as best she could. It was there in 1963 that

the news arrived that she was to become a Nobel laureate. She and Jensen

shared half the prize in theoretical physics for their discoveries concerning

nuclear shell structure; the other half went to Wigner for contributing to

the theory of the atomic nucleus and the elementary particles. Election to

the National Academy of Sciences and several honorary doctorates soon

followed, but her health gradually declined and she died of heart failure on

February 20, 1972.

Goeppert-Mayer dealt with the obstacles she faced in her career partly

by identifying with men at an early age and by disregarding the expectations

of the society in which she lived. Like some other successful women scientists,

she received much encouragement from key men in her life, beginning

with her father, ‘a gentle bear of a man’, who wanted her to make something

of her gifts. Many of her colleagues, including Born and Fermi, were

supportive, but, perhaps partly because she worked so long without recognition,

she was unduly modest about her work and abilities. Some of the

difficulties Goeppert-Mayer experienced turned to her advantage. Unable

to determine her own career path, she seized the opportunities which arose

as she followed her husband’s career. Although she had been educated as a

mathematical physicist and was equipped with great facility in the Born–

Heisenberg matrix formulation of quantum theory, she turned to physical

chemistry when she went to America. The combination of theoretical and

practical knowledge was important for her later work on nuclear structure.

What was undertaken from expedience led to a deeper appreciation of

experiment and understanding of a new field. She learned about nuclear

physics, another new field to her, from Teller and from Fermi while at

Columbia and Chicago. The varied strands in her background, both the

planned and the unplanned, eventually converged in the studies that earned

her the Nobel prize for the shell model of the nucleus. In the first century

of the prizes, only two women have been awarded a Nobel prize in

physics.

Hideki Yukawa (1907–1981) 369

Hideki Yukawa (1907–1981)

Hantar ¯o Nagaoka, who studied under Boltzmann, was the first Japanese

physicist to participate fully in the competitive world of theoretical and

experimental physics. Some young Japanese scientists studied in Germany,

others in Britain, a few in France. They encountered language and other

cultural difficulties. For example, several young professors of the faculty of

science of the Imperial University who went to study at the University of

Berlin heard an address glorifying the progress of German science in which

the dean of the faculty said ‘In order to study science in Germany, there

come to this country many foreigners, Americans and so on, and lately

even Japanese. In future, no doubt, even apes will be coming . . .’

Until around 1935 the contribution of the Japanese nation to world

physics was very limited. By the end of the Second World War, however,

Japan had become a significant contributor to theoretical physics, with an

impressive number of first-rate research workers. Initially by far the largest

volume of Japanese research was on the most modern aspect of the subject:

elementary particles and fields. The new Japanese school was essentially

the school of Hideki Yukawa and his friend and contemporary Sin-itiro

Tomonaga. Both were Nobel laureates in physics. Both of them wrote

370 From Heisenberg to Yukawa

autobiographies that have been translated into English, but Yukawa is more

informative about his early years, and for that reason I choose him as the

main subject for this profile. Of the two, Tomonaga had a more open and

engaging personality; he remarked that ‘Yukawa’s eyes look inward, mine

look outward.’

The man known to the scientific world as Hideki Yukawa was born in

the Azabu district of Tokyo on January 23, 1907, during the fortieth year of

the Meiji era. The child was the middle one of five brothers, the fifth of seven

children altogether. Their parents were Takuji Ogawa and his wife Koyuki.

Until his marriage to Sumi Yukawa in 1932, when he was adopted into

his wife’s family, the future physicist’s name was Hideki Ogawa. Hideki’s

father’s name had been changed from Asai to Ogawa for a similar reason.

For a few months after Hideki’s birth his father remained on the staff of

the Geological Survey Bureau in Tokyo but in 1908 he became professor

of geography at the University of Kyoto. Thus Hideki regarded Kyoto, the

former capital city of Japan, as his home town; he spent almost all his life

there.

Both the Asai family and the Ogawa family could look back on generations

of scholars steeped in the tradition of Chinese as well as Japanese culture.

Hideki’s grandfather was a Confucian scholar and teacher of Chinese

classics. His son Takuji, brought up in the same tradition, was well-versed

in Chinese religion and philosophy, collected antiques and maintained an

active interest in the history of ancient China and Japan throughout his life.

He was associated with the Institute of Oriental Culture, under whose auspices

he frequently visited China to participate in archaeological surveys

and expeditions.

Like his brothers, Hideki was exposed to ancient traditions in childhood

and adolescence. He recalled that, even before he entered primary

school, he had studied various Chinese classics: ‘In practice this meant

that I repeated aloud after my grandfather a version of the Chinese texts

converted into Japanese. At first, of course, I had no idea of the sense of

it at all. Yet oddly enough I gradually began to understand without being

told.’

In his autobiography Ogawa, as Yukawa was called in his youth, says

that he was afraid of the stormytemperament of his unpredictable father and

tried to avoid him; the influence of the boy’s mother and grandparents on

his upbringing seems to have been dominant.We learn from Ogawa himself

that as a boy he was clumsy and ill at ease in his relations with other people.

‘I never did develop socially’, he recalled, ‘often I think human relationships

Hideki Yukawa (1907–1981) 371

are tiresome, even among Japanese. Relating to foreigners simply wears out

my nerves.’

At school Ogawa consistently obtained good marks, but when asked

a question would often remain silent when he knew the answer perfectly

well. When the time to choose a speciality arrived, he found it difficult to

make a decision. His difficulty in interacting with people was linked, so he

relates, to a complete lack of interest in human problems, so that all fields

within the sphere of social science in the broad sense had no appeal whatsoever.

Although literature and philosophy interested him, mathematics was

his favourite subject. Indeed, the latter field seemed for a time to be the

most likely choice of specialization, even though he had some doubts about

devoting himself to a study that seemed to be so unrelated to the natural

world.

Ogawa, when young, lived in a world of his own and made his own

decisions. An avid and catholic reader, at the age of thirteen he entered

high school, where he discovered in its library a series of books in Japanese

explaining modern physics at a level he found accessible, at least in part.

Ogawa related that he found the ideas of relativity comprehensible and

exciting. On the other hand, in commenting on an introduction to quantum

theory, he recalled that ‘however much I read it, it made no sense to me . . .

so I thought it might be a good idea to study it’. He appears to have kept to

this resolution with remarkable tenacity.

Ogawa relates that, while he was at high school, he took very little

notice of the normal run of student life around him, feeling an aversion to

the bohemian life-style of his contemporaries. He was supposed to attend

a class in economics and law but relates that these lectures went in one

ear and out the other. Even so, his natural ability and methodical habits

seemed to carry him safely over all examination hurdles. While he was at

school a well-publicized visit to Japan by Einstein in 1922 had opened up the

new world of ideas in physics to the Japanese. Ogawa taught himself some

German and, when browsing in a bookshop, picked up the first volume

of Planck’s Einfu¨ hrung in die theoretische Physik. He relates with great

warmth how he found the work both intelligible and fascinating, and as a

result he decided to study at the physics department of the University of

Kyoto.

The year of his entry was 1926, just after the discovery of the new

quantum mechanics in the west. Whatever of the older quantum theory

was included in the course he was offered – and it seems that there was

very little – the new ideas had certainly not penetrated far. The account he

372 From Heisenberg to Yukawa

gave of his studies is entirely about his private reading: learning the older

quantum theory from an English translation of Reich’s Quantentheorie and

then, just as the first news of quantum mechanics was reaching Japan, being

inspired by Born’s Probleme der Atomdynamik. From then on it was a

matter of studying new papers as they became available. As with so many

other workers of the day, Schro¨ dinger’s version of quantum mechanics –

wave mechanics – came as a revelation. He found it so much easier to understand

than the Heisenberg matrix mechanics that had preceded it. Ogawa

persuaded his teacher to agree to his choosing the new theory as his main

subject for graduation. It seems that the only outside stimulus during these

studies was from his friendship with his classmate Tomonaga.

Like Ogawa, Sin-itiro Tomonaga came from a family of culture,

renowned for its literary scholarship. He was born in 1906, the eldest son of

Sanjuro Tomonaga, who in turn was of Nagasaki samurai descent. Sanjuro

had studied philosophy and history of philosophy at Tokyo Imperial University

and at the time of Sin-itiro’s birth was professor of philosophy at Shinshu

University (later known as Otani University) in Tokyo. The following year

he took up the position of associate professor at Kyoto University and in

1909 went to Europe for further study, leaving his wife and child with relatives

in Tokyo. When he returned after an absence of four years, the family

went to live in Kyoto, where he had been appointed professor.

Also like Ogawa, Sin-itiro Tomonaga gained admission to the faculty

of science at Kyoto University in 1926 and elected to specialize in physics.

He was greatly disappointed at the level of the lectures, especially in physics:

moreover, the laboratories provided were dark, dirty and old-fashioned.

More advanced work was being done in the laboratory of Professor Kajuro

Tamaki, whose speciality was fluid dynamics and whose interests extended

to relativity but not quantum theory. Soon Ogawa, Tomonaga and a few

other ambitious students were studying western publications together.

They saw that in atomic physics one major problem after another was

rapidly being resolved, often by young researchers such as Heisenberg, Dirac,

Pauli and Fermi.

Ogawa realized that quite basic questions remained unanswered in

the context of relativistic quantum theory, in the quantum theory of fields

and in the description of the atomic nucleus. He made the bold decision

to concentrate on these even newer problems. As his graduation thesis he

chose to offer some investigations on the properties of Dirac’s equation.

While there is no record of what went into this work, it was sufficiently

impressive to enable him to graduate in 1929 and, although Tamaki did not

Hideki Yukawa (1907–1981) 373

accept research students, he and Tomonaga were allowed to remain in the

laboratory as unpaid assistants. That year both Heisenberg and Dirac visited

Kyoto, as did also the physicist Yoshio Nishina, who had just returned from

seven years in Europe, most of the time spent studying with Bohr in Copenhagen.

Nishina was impressed by the two young researchers and invited

Tomonaga to join him in Tokyo.

In 1932 Ogawa married the classical Japanese dancer Sumi Yukawa

and, as we have seen, adopted her family name, replacing the name of Ogawa.

He was also appointed instructor in physics at his alma mater, where he lectured

on quantum mechanics, using Dirac’s textbook. One of his students

described his voice as being ‘gentle as a lullaby, an ideal invitation to sleep’.

The following year he began speculating about the nature of the proton–

neutron force. Before the moment of breakthrough Yukawa was given the

chance to move from the peaceful atmosphere of Kyoto to the much livelier

surroundings of the industrial city of Osaka, where a new university was

being built up with a strong physics department, including a large experimental

group provided with modern accelerator equipment. In this stimulating

environment Yukawa’s ideas came to fruition and his famous first

paper was published, predicting the existence of a new fundamental particle,

the meson.

After 1937 Yukawa was increasingly seen as a leader of theoretical

physics in Japan. Already he could attract many research students, and his

appointment to a chair was not long delayed. He was happy that this should

be at his alma mater, soon to be internationally recognized as a major centre

for theoretical physics. His first visit to the west included attendance at the

eighth Solvay conference in Brussels in 1939. The arrangements for this

were disrupted by the outbreak of the Second World War, but Yukawa was

able to take the opportunity to establish personal contact with European

and American physicists.

After the war, when Yukawa’s own interest was beginning to turn

away from the particular topic of meson theory to more general unsolved

problems, the experimental discovery of the pion further enhanced his reputation.

In 1948 he accepted Oppenheimer’s invitation to work at the Institute

for Advanced Study in Princeton, which was followed by appointment

to a chair at Columbia University in New York. He remained at Columbia

until 1953, when he was offered the directorship of a new inter-university

research institute in Kyoto, housed in a building to be named in his honour.

Yukawa remained in the old capital for the rest of his life. After reaching

the age of seventy-four he became gravely ill and died from pneumonia on

374 From Heisenberg to Yukawa

September 8, 1981, survived by his widow Sumi and two sons, Harumi and

Takai. He had received the Nobel prize in 1949, and many other honours

as well.

In conclusion, something should also be said about the later career

of Yukawa’s friend Tomonaga, a quiet person of great charm. After a period

of studying nuclear theory at Leipzig University under Heisenberg from

June 1937 to August 1939, Tomonaga returned to Japan and received his

D.Sc. from Tokyo Imperial University. In 1941 he was appointed professor

at theTokyo University of Science and Literature.Two years laterTomonaga

was mobilized with other Japanese physicists to undertake research on

magnetrons and ultra-short-wave circuits at the laboratory of the Naval

Research Institute at Shimada. In addition he was a part-time lecturer at

Tokyo University. Because of the intense air raids on Tokyo, he sent his

family to live in the country while he remained in the city. During a raid on

April 13, 1945 the district to the west of the campus where many professors

lived was destroyed, including the house of Tomonaga.

After the war his seminar became a Mecca for young physicists. In

1948 he was elected to the Science Council of Japan. The following year

he visited the Institute for Advanced Study in Princeton. In 1965 he shared

the Nobel prize in physics with Richard Feynman and Julian Schwinger

for contributions to quantum electrodynamics. Tomonaga’s theory of 1943

had been developed quite independently of the American one, of which he

did not become aware until the war was over. Like his friend Yukawa, he

was awarded the prestigious Cultural medal of Japan, and numerous other

scientific honours.

Much more than Yukawa, Tomonaga took on responsibility for

nuclear physics and science policy generally in Japan. Scientists had long

been perceived as left-wing agitators, opposed to big business and keen to

distance themselves from the bureaucracy; Tomonaga attempted to break

down this stereotype. The two Nobel laureates attended the first Pugwash

conference held in Canada in 1957 and put their prestige behind the movement

to ban atomic and hydrogen bombs. Tomonaga’s health was poor in

later years, and he died on July 8, 1979. Today Japanese workers contribute

significantly to many branches of physics, both experimental and theoretical,

following the lead of the two pioneers.

Epilogue

In the list of contents at the front of this book the names of all the subjects of

the profiles are arranged in order of date of birth. The following list consists

of the same names arranged in order of date of death.

Johannes Kepler (1571–1630)

Galileo Galilei (1564–1642)

Christiaan Huygens (1629–1695)

Isaac Newton (1642–1726)

Daniel Bernoulli (1700–1782)

Roger Boscovich (1711–1787)

Benjamin Franklin (1706–1790)

Charles Augustin Coulomb (1736–1806)

Henry Cavendish (1731–1810)

Benjamin Thompson (Count Rumford) (1753–1814)

Pierre-Simon Laplace (1749–1827)

Thomas Young (1773–1829)

Jean-Baptiste Fourier (1768–1830)

Andr´e-Marie Amp`ere (1775–1836)

George Green (1793–1841)

Hans Christian Oersted (1777–1851)

Georg Ohm (1789–1854)

Michael Faraday (1791–1867)

Joseph Henry (1797–1878)

James Clerk Maxwell (1831–1879)

Hermann von Helmholtz (1821–1894)

Willard Gibbs (1839–1903)

Ludwig Boltzmann (1844–1906)

William Thomson (Lord Kelvin) (1824–1907)

John William Strutt (Lord Rayleigh) (1842–1919)

Wilhelm Conrad Ro¨ ntgen (1845–1923)

Paul Ehrenfest (1880–1933)

Marie Curie (1867–1934)

Ernest Rutherford (Lord Rutherford) (1871–1937)

Joseph John Thomson (1856–1940)

William Henry Bragg (1862–1942)

Max Planck (1858–1947)

376 Epilogue

Robert Millikan (1868–1953)

Enrico Fermi (1901–1954)

Albert Einstein (1879–1955)

Frederick Lindemann (Lord Cherwell) (1886–1957)

Jean-Fr´ed´ eric Joliot (1900–1958)

Erwin Schr ¨ odinger (1887–1961)

Niels Bohr (1885–1962)

J. Robert Oppenheimer (1904–1967)

Otto Hahn (1879–1968)

Lise Meitner (1878–1968)

Max Born (1882–1970)

Maria Goeppert-Mayer (1906–1972)

Satyendranath Bose (1894–1974)

Werner Heisenberg (1901–1976)

Hideki Yukawa (1907–1981)

Piotr Leonidovich Kapitza (1894–1984)

Paul Dirac (1902–1984)

Louis de Broglie (1892–1987)

The fifty physicists whose profiles make up this book were the sons or

daughters of men who were engaged in a wide variety of occupations. Only

some of them were academics: Daniel Bernoulli and William Thomson

were the sons of professors of mathematics, Gibbs was the son of a professor

of sacred literature, Born the son of a professor of embryology, Bohr

the son of a professor of physiology, Goeppert-Mayer the daughter of a

professor of paediatrics, and Yukawa the son of a professor of geography.

Others were the offspring of professional men: Helmholtz and Dirac were

the sons and Marie Curie was the daughter of schoolteachers, Maxwell and

Planck were the sons and Meitner was the daughter of lawyers, Oersted was

the son of a pharmacist, Millikan was the son of a preacher, Lindemann

and Kapitza were the sons of architects or engineers, Galileo was the son

of a musician, Huygens was the son of a diplomat, and Bose was the son

of an accountant. Franklin, Boscovitch, Young, Ampe` re, Ro¨ ntgen and J.J.

Thompson were the sons of merchants. Newton, Rumford, Laplace and

Bragg were the sons of farmers. Coulomb, Boltzmann and Fermi were the

sons of public officials. Einstein, Schro¨ dinger, Joliot and Oppenheimer were

the sons of businessmen. Kepler was the son of a soldier of fortune. Maxwell

and Strutt were the sons of wealthy landowners; perhaps Cavendish and de

Broglie should be included in the same category. Several subjects were sons

Epilogue 377

of artisans or tradesmen, in particular Fourier was the son of a tailor, Ohm

and Heisenberg were the sons of locksmiths, Hahn the son of a glazier,

Faraday the son of a blacksmith, Green the son of a miller, and Rutherford

the son of a wheelwright. Joseph Henry’s father was a day labourer, and

Ehrenfest’s father worked in a textile mill. At some time in their lives, usually

childhood, Kepler, Franklin, Fourier, Ohm, Faraday and Marie Curie

knew poverty.

A number of our subjects inherited or acquired titles of nobility, and

these have been used where appropriate. Of course, the nature of such titles

varied from country to country; today they survive officially in only a few

countries, but they were common in Europe during most of our period.

Laplace was made a marquis and Fourier a baron, while de Broglie succeeded

to the title of duke. Benjamin Thompson was made a count in Bavaria;

de Broglie inherited the imperial title of prince. Rayleigh succeeded to his

title, while Kelvin and Rutherford received theirs for services to science.

Lindemann was elevated to a viscountcy for services more political than

scientific. In addition, a number of our subjects received knighthoods or

similar honours.

Bearing in mind the shorter expectation of life in the eighteenth and

nineteenth centuries, the great majority of our subjects lived into old age.

Exceptions are Green and Maxwell, who died at forty-eight, and Ehrenfest

and Fermi, who died at fifty-three. In most cases deaths were from natural

causes, insofar as they are known, except that Planck died after a road accident,

while Boltzmann and Ehrenfest committed suicide. Marie Curie, her

daughter Ir `ene Curie and son-in-law Fr´ed´ eric Joliot essentially died from

radiation sickness. Boltzmann, and probably Ehrenfest, suffered from the

mood-swings characteristic of manic-depression, but retrospective diagnosis

of mental disorders is notoriously difficult. People with Asperger’s syndrome,

a mild form of autism, seem to be attracted to physics. Newton,

Cavendish, Einstein and Dirac are thought to have had the syndrome. In

childhood only a few of our subjects could be described as precocious and,

although several exhibited phenomenal memory, only Lindemann seems to

have shown any sign of savant skills. Most subjects displayed an enthusiasm

and aptitude for physics from an early age, but some only decided to

become physicists relatively late.

A companion work, Remarkable Mathematicians, has been published.

The distribution of occupations of the fathers of the mathematicians

is noticeably different from that of the physicists; rather more of them were

men of religion, rather fewer were professional men, and rather more of the

378 Epilogue

subjects grew up in a condition of poverty. Again, for mathematicians more

than for physicists there are indications that the maternal influence was

the dominant one in their upbringing. Two subjects, namely Fourier and

Laplace, appear in both works, since they seem to qualify equally well both

as mathematicians and as physicists. Arguably this is true in some other

cases.

Much more has been written about the physicists than the mathematicians,

whole shelves of books about Galileo, Newton, Einstein and

Faraday, for example, and a greater tendency to hagiography is apparent.

The story of the development of mathematics does not run parallel to that

of physics. Moreover, there are cultural differences. Increasingly, experimental

physics has become a matter of teamwork whereas research in theoretical

physics, as in mathematics, can still be practised successfully by individuals

working in isolation. The world of physics is more intensely competitive, so

a promising line of research may be kept secret in case someone else starts

to compete. Moreover, progress is often achieved by discarding one theory in

favour of another, after a period of controversy; there is nothing comparable

in mathematics. Finally, there is the vexed question of commercial exploitation

of discoveries, the possibility of which arises much more frequently in

physics.

Further Reading

Many of the remarkable physicists featured in this book have been the

subjects of full-scale biographies. Some that have appeared fairly recently,

mainly in the English language, are listed below. To list all relevant articles

would take up an excessive amount of space, but the reader who wishes for

further information in a particular case will find bibliographies in such reference

works as the Dictionary of Scientific Biography and the Isis Cumulative

Bibliography. Journals such as the Archive for History of Exact Sciences

often contain relevant articles. The new Biographical Dictionary ofWomen

Scientists is another source of information, and there are several biographical

collections, of which a few are listed, for example those by J.G. Crowther.

Although they were written long ago, Crowther’s informative and reliable

biographies of British and American scientists make a good starting-point.

Among more recent accounts of the lives and works of selected physicists,

that by William Cropper, listed below, can be recommended as an excellent

introduction for the general reader. More or less complete ‘Collected

Works’, usually containing some biographical information, have been compiled

for most of our subjects, and these are also listed below. In a few cases

the subject’s scientific correspondence has been edited and published, and

this can be of particular interest.

1. Andriesse, Cornelis Dirk. Christiaan Huyghens. Paris: Albin Michel, 1996.

2. Appleyard, Rollo. Pioneers of Electrical Communication. London: Macmillan,

1930.

3. Armitage, Angus. John Kepler. London: Faber & Faber, 1966.

4. Bell, A.E. Christian Huygens and the Development of Science in the Seventeenth

Century. London: Edward Arnold, 1947.

5. Berry, A.J. Henry Cavendish; His Life and Scientific Work. London: Hutchinson

& Co., 1960.

6. Biafioli, Mario. Galileo, Courtier. Chicago, IL: University of Chicago Press, 1993.

7. Biquard, Pierre. Fr´ed´ eric Joliot-Curie: The Man and his Theories (trans. Geoffrey

Strachan). London: Souvenir Press, 1965.

8. Birkenhead, Earl of. The Prof in Two Worlds. London: Collins, 1961.

9. Blaedel, Niels. Harmony and Unity: The Life of Niels Bohr (trans. Geoffrey

French). Madison, WI: Science Tech. Inc., 1988.

10. Born, Max. My Life: Reflections of a Nobel Laureate. London: Taylor and Francis,

1978.

380 Further Reading

11. Brian, Denis. Einstein: A Life. New York, NY: John Wiley and Sons Inc., 1996.

12. Broda, Engelbert. Ludwig Boltzmann (trans. Engelbert Broda and Larry Gay).

Woodbridge, CN: Ox Bow Press, 1983.

13. Brown, G.I. Count Rumford: Scientist, Soldier, Statesman, Spy: The Extraordinary

Life of a Scientific Genius. Stroud: Sutton, 1999.

14. Brown, Sanborn C. Benjamin Thompson, Count Rumford. Cambridge, MA: MIT

Press, 1979.

15. Caban, D. Hermann von Helmholtz and the Foundations of Nineteenth Century

Science. Berkeley, CA: University of California Press, 1993.

16. Campbell, John. Rutherford, Scientist Supreme. Christchurch, New Zealand:

AAS Publications, 1999.

17. Cannell, D.M. George Green: Mathematician and Physicist 1793–1841. London:

Athlone Press, 1993.

18. Cantor, Geoffrey. Michael Faraday: Sandemanian and Scientist. London:

Macmillan, 1991.

19. Caroe, G.M. William Henry Bragg. Cambridge: Cambridge University Press,

1978.

20. Caspar, Max. Kepler (trans. and ed. by C. Doris Hellman). London and New York:

Abelard-Schuman, 1959.

21. Cassidy, David C. Uncertainty; the Life and Science ofWerner Heisenberg. New

York, NY: W.H. Freeman, 1992.

22. Cercignani, Carlo. Ludwig Boltzmann, the Man who Trusted Atoms. Oxford:

Oxford University Press, 1998.

23. Chaterjee, Santimay et al. (eds.). S.N. Bose: The Man and his Work. Calcutta:

S.N. Bose National Centre for Basic Sciences, 1994.

24. Cohen, I. Bernard. Benjamin Franklin’s Science. Cambridge, MA: Harvard

University Press, 1990.

25. Cotton, Eug´enie. Les Curies. Paris: Editions Seghers, 1963.

26. Coulson, Thomas. Joseph Henry: His Life and Work. Princeton, NJ: Princeton

University Press, 1950.

27. Cropper, William H. Great Physicists: The Life and Times of Leading Physicists

from Galileo to Hawking. New York, NY: Oxford University Press, 2001.

28. Crowther, J.G. British Scientists of the Nineteenth Century. London: Kegan Paul,

Trench, Trubner, 1935.

29. Crowther, J.G. Famous American Men of Science. London: Secker and Warburg,

1937.

30. Crowther, J.G. British Scientists of the Twentieth Century. London: Routledge

& Kegan Paul, 1952.

31. Curie, Eve. Madame Curie. London: Heinemann, 1939.

32. Curie, Marie. Pierre Curie. New York, NY: MacMillan, 1923.

Further Reading 381

33. Dash, Joan. A Life of One’s Own. New York, NY: Harper & Row, 1973.

34. Davis, E.A. and Falconer, I.J. J.J. Thomson and the Discovery of the Electron.

London: Taylor and Francis, 1997.

35. Doren, Carl Van. Benjamin Franklin. 1938.

36. Drake, Stillman. Galileo Studies. Ann Arbor, MN: University of Michigan Press,

1970.

37. Drake, Stillman. Galileo atWork. Chicago, IL: University of Chicago Press, 1978.

38. Drake, Stillman. Galileo, Pioneer Scientist. Toronto: University ofToronto Press,

1990.

39. Dunsheath, Percy. Giants of Electricity. New York, NY: Thomas Y. Crowell,

1967.

40. Eve, A.S. Rutherford. Cambridge: Cambridge University Press, 1939.

41. Everitt, C.W. James Clerk Maxwell: Physicist and Philosopher. New York, NY:

Scribner, 1975.

42. Farah, Patricia. Newton: The Making of a Genius. Basingstoke: MacMillan, 2002.

43. Fermi, Laura. Atoms in the Family. London: George Allen and Unwin, 1955.

44. Fermi, Laura. Illustrious Immigrants. Chicago, IL: Chicago University Press,

1961.

45. F ¨ olsing, Albrecht. Albert Einstein: A Biography. New York, NY: Viking, 1997.

46. French, A.P. and Kennedy, P.J. Niels Bohr. A Centenary Volume. Cambridge, MA:

Harvard University Press, 1985.

47. Fu¨ chtbauer, Ritter von. Georg Simon Ohm. Berlin: BDF Verlag, 1939.

48. Gillispie, C.C. et al. Pierre-Simon Laplace. Princeton, NJ: Princeton University

Press, 1997.

49. Gillmor, C. Stewart. Coulomb and the Evolution of Physics and Engineering

in Eighteenth-century France. Princeton, NJ: Princeton University Press,

1971.

50. Giroud, Franc¸ oise. Marie Curie. A Life (trans. Lydia Davis). New York, NY:

Holmes and Meier, 1986.

51. Glasser, Otto. William Conrad Roentgen and the History of the Roentgen Rays.

London: John Bale & Sons, Danielsson, 1933.

52. Goading, David and James, Frank Agile. Faraday Rediscovered. Basingstoke:

MacMillan, 1989.

53. Goldman, Martin. The Demon in the Aether: The Story of James Clerk Maxwell.

Bristol: Adam Hilger, 1983.

54. Goldsmith, Maurice. Fr´ed´ eric Joliot-Curie. London: Lawrence andWishart, 1976.

55. Golino, Carlo L. Galileo Reappraised. Berkeley, CA: University of California

Press, 1966.

56. Grattan-Guinness, Ivor. Joseph Fourier 1768–1830. Cambridge, MA: MIT Press,

1972.

382 Further Reading

57. Hahn, Otto. My Life (trans. Erns Kaiser and EithneWilkins). London: Macdonald,

1970.

58. Hahn, Otto. A Scientific Autobiography (trans.Willey Ley). MacGibbon and Kee,

1967.

59. Hamilton, James. Faraday: The Life. London: Harper Collins, 2002.

60. Heilbron, J.L. The Dilemmas of an Upright Man: Max Planck as Spokesman for

German Science. Berkeley, CA: University of California Press, 1986.

61. Heisenberg, Elizabeth. Inner Exile: Recollections of a Life with Werner Heisenberg

(trans. S. Cappellari and C. Morris). Boston, MA: Birkh¨auser, 1984.

62. Heisenberg,Werner. Physics and Beyond: Encounters and Conversations (trans.

Arnold J. Pomerans). New York, NY: Harper and Row, 1971.

63. Herivel, John. Joseph Fourier. The Man and the Physicist. Oxford: Clarendon

Press, 1975.

64. Highfield, Robert and Carter, Paul. The Private Lives of Albert Einstein. London:

Faber & Faber, 1993.

65. Hoffmann, Banesh, with Helen Dukas. Albert Einstein: Creator and Rebel. New

York, NY: Viking, 1972.

66. Hoffmann, K. Otto Hahn: Achievement and Responsibility. Heidelberg: Springer

Verlag, 2001.

67. Hofmann, James R.I. Andr´e-Marie Amp`ere. Cambridge: Cambridge University

Press, 1995.

68. James, Frank A.J.L. (ed.). The Correspondence of Michael Faraday. London: Institution

of Electrical Engineers, 1991.

69. Jungnickel, Christa and McCormmack, Russell. Cavendish: The Experimental

Life. Philadelphia, PA: American Philosophical Society, 1999.

70. Kargon, Robert H. The Rise of Robert Millikan. Ithaca, NY: Cornell University

Press, 1982.

71. King, Agnes Gardner. Kelvin the Man. London: Hodder and Stoughton, 1925.

72. Klein, Martin J. Paul Ehrenfest. Amsterdam: North Holland, 1970.

73. Koestler, Arthur. The Sleepwalkers. London: Hutchinson, 1959.

74. Ko¨ nigsberger, Leo. Hermann von Helmholtz (trans. Frances A.Welby). Oxford:

Clarendon Press, 1906.

75. Kragh, Helge. Dirac: A Scientific Biography. Cambridge: Cambridge University

Press, 1990.

76. Kursunoglu, Behram N. and Wigner, Eugene P. (eds). Reminiscences about a

Great Physicist: Paul Adrien Maurice Dirac. Cambridge: Cambridge University

Press, 1987.

77. Linsay, Robert Bruce. Lord Rayleigh: The Man and his Work. Oxford: Pergamon

Press, 1970.

Further Reading 383

78. Machamer, Peter (ed.). The Cambridge Companion to Galileo. Cambridge:

Cambridge University Press, 1998.

79. Manuel, Frank E. A Portrait of Isaac Newton. Cambridge, MA: Belknap Press,

1968.

80. Matsui, Makinsake (ed.). Tomonaga, Sin-Itoro: The Life of a Japanese Physicist

(trans. Cheryl Dujimoto and Takako Sano). Tokyo: MYU, 1995.

81. Millikan, Robert A. Autobiography. London: Macdonald, 1951.

82. Moore, Ruth. Niels Bohr: The Man and the Scientist. London: Hodder &

Stoughton, 1967.

83. Moore, Walter. Schro¨ dinger: Life and Thought. Cambridge: Cambridge University

Press, 1989.

84. More, Louis Trenchard. Isaac Newton: A Biography. New York, NY: Charles

Scribner’s Sons, 1934.

85. Moyer, Albert E. Joseph Henry, the Rise of an American Scientist. Washington,

DC: Smithsonian Institution Press, 1997.

86. Nachmansohn, David. German-Jewish Pioneers in Science, 1900–1933. Heidelberg:

Springer Verlag, 1978.

87. Nitske, W. Robert. The Life of Wilhelm Conrad Ro¨ ntgen, Discoverer of the

X-Ray. Tucson, AZ: University of Arizona Press, 1971.

88. Pais, Abraham. Subtle is the Lord – The Science and Life of Albert Einstein.

Oxford: Clarendon Press, 1982.

89. Pais, Abraham. Niels Bohr’s Times, in Physics, Philosophy and Polity. Oxford:

Clarendon Press, 1991.

90. Pais, Abraham. The Genius of Science. Oxford: Oxford University Press, 2000.

91. Peacock, George. Life of Thomas Young, M.D., F.R.S., etc. London: John Murray,

1855.

92. Pflaum, Rosalynd. Grand Obsession: Madame Curie and her World. New York,

NY: Doubleday, 1989.

93. Planck, Max. Scientific Autobiography and Other Papers (trans. F. Gaynor). New

York: NY: Philosophical Library, 1949.

94. Quinn, Susan. Marie Curie: A Life. London: Heinemann, 1995.

95. Reston, James R. Jr. Galileo. London: Cassell, 1994.

96. Rife, Patricia. Lise Meitner and the Dawn of the Nuclear Age. Basel: Birkh¨auser,

1992.

97. Rose, Paul Lawrence. Heisenberg and the Nazi Atomic Bomb Project. Berkeley,

CA: University of California Press, 1998.

98. Rozental, Stefan (ed.). Niels Bohr: His Life andWork as Seen by His Friends and

Colleagues. Amsterdam: North Holland, 1968.

99. Rukeyser, Muriel. Willard Gibbs. Woodbridge, CN: Ox Bow Press, 1988.

384 Further Reading

100. Segr` e, Emilio. Enrico Fermi; Physicist. Chicago, IL: University of Chicago Press,

1970.

101. Sharatt, Michael. Galileo: Decisive Innovator. Oxford: Blackwell, 1994.

102. Sharlin, Harold I. Lord Kelvin: The Dynamic Victorian. Philadelphia, PA:

Pennsylvania State University Press, 1979.

103. Sime, Ruth Lewin. Lise Meitner: A Life in Physics. Berkeley, CA: University of

California Press, 1996.

104. Smith, Alice Kimball and Weiner, Charles Robert. Oppenheimer: Letters and

Recollections. Madison, WI: University of Wisconsin Press, 1968.

105. Smith, Crosbie andWise, M. Norton. Energy and Empire: A Biographical Study

of Lord Kelvin. Cambridge: Cambridge University Press, 1989.

106. Sobell, Dava. Galileo’s Daughter. London: Fourth Estate, 1999.

107. Strutt, Robert John (Fourth Baron Rayleigh). Life of John William Strutt Third

Baron Rayleigh. Cambridge, MA: Harvard University Press, 1980.

108. Tolstoy, Ivan. James Clerk Maxwell. Edinburgh: Canongate, 1981.

109. Villami, R de. Newton the Man. London: Gordon D. Knox, 1931.

110. Westfall, Richard S. The Life of Isaac Newton. Cambridge: Cambridge University

Press, 1993.

111. Wheeler, Lynde Phelps. Josiah Willard Gibbs: The History of a Great Mind.

New Haven, CN: Archon Books, Yale University Press, 1970.

112. White, Michael. Isaac Newton; the Last Sorcerer. London: Fourth Estate, 1997.

113. Whitrow, G.J. (ed). Einstein: The Man and his Achievement. London: British

Broadcasting Corporation, 1957.

114. Whyte, Lancelot Law (ed.). Roger Joseph Boscovich. London: George Allen and

Unwin, 1961.

115. Williams, L. Pearce. Michael Faraday. London: Chapman and Hall, 1965.

116. Wilson, David. Rutherford: Simple Genius. London: Hodder and Stoughton,

1983.

117. Wilson, David B. Kelvin and Stokes:AComparative Study in Victorian Physics.

Bristol: Adam Hilger, 1987.

118. Wilson, George. The Life of the Honourable Henry Cavendish. London:

Cavendish Society, 1851.

119. Wood, Alexander. Thomas Young, Natural Philosopher, 1773–1829. Cambridge:

Cambridge University Press, 1954.

120. Yukawa, Hideki. Tabibito (The Traveller) (trans L. Brown and K. Yoshida).

Singapore: World Scientific Publications, 1982.

Collections

The publications of the subjects of the profiles can generally be found most

conveniently in their respective Collected Works, where these exist. In

physics such collections tend to be selective rather than complete, since it

is in the nature of the subject for the results of even the best research often

to be rapidly superseded. In the case of Daniel Bernoulli, Amp` ere, R¨ ontgen,

J.J. Thomson, Bragg, Millikan, Meitner, Hahn, Lindemann, Schro¨ dinger, de

Broglie, Bose, Oppenheimer and Goeppert-Mayer no such collections exist,

apparently. For the remaining subjects I have found it useful to consult the

following:

Galileo Galilei: Le opere di Galileo Galilei. Florence, 1929–1939.

Johannes Kepler: Gesammelte Werke. Munich: C.H. Beck, 1937–1990.

Christiaan Huygens: Oeuvres Compl`etes. The Hague: Soci´et´e Hollandaise des

Sciences, Martinus Nijhoff, 1888–1950.

Isaac Newton: The Mathematical Papers of Isaac Newton. Cambridge: Cambridge

University Press, 1967–1981.

Benjamin Franklin: The Papers of Benjamin Franklin. New Haven, CN: Yale University

Press, 1959–1999.

Roger Boscovich: Rogerii Josephi Boscovich opera pertinentia ad opticam et astronomiam.

Bassano: Remondini, 1785.

Henry Cavendish: The Scientific Papers of the Honourable Henry Cavendish, FRS.

Cambridge: Cambridge University Press, 1921.

Charles Augustin de Coulomb: M´emoires de Coulomb. Paris: Soci´et´e Franc¸aise de

Physique, 1884.

Pierre-Simon Laplace: Oeuvres compl`etes. Paris: Gauthier-Villars, 1878–1912.

Count Rumford: Collected Works of Count Rumford. Cambridge, MA: Harvard

University Press, 1968.

Joseph Fourier: Oeuvres de Fourier. Paris: Gauthier-Villars, 1888–1890.

Thomas Young: Miscellaneous Works. London: John Murray, 1854.

Hans Christian Oersted: Selected Scientific Works of Hans Christian Oersted.

Princeton, NJ: Princeton University Press, 1998.

Georg Ohm: Gesammelte Abhandlungen, Leipzig: Johann Ambrosius Barth, 1892.

Michael Faraday: Experimental Researches in Electricity. London, 1839/1855.

Experimental Researches in Chemistry and Physics. London 1859.

George Green: Mathematical Papers of the Late George Green. London: MacMillan,

1871.

386 Collections

Joseph Henry: The ScientificWritings of Joseph Henry.Washington, DC: Smithsonian

Institution Publications, 1886.

Hermann Helmholtz:Wissenschaftliche Abhandlungen. Leipzig: Johann Ambrosius

Barth, 1982.

Lord Kelvin: Mathematical and Physical Papers of Sir William Thomson/Lord

Kelvin. Cambridge: Cambridge University Press, 1882/1911.

James Clerk Maxwell: Scientific Papers. Cambridge: Cambridge University Press,

1890.

Willard Gibbs: The Scientific Papers of J. Willard Gibbs. London: Longmans Green,

1966.

Lord Rayleigh: Scientific Papers. Cambridge: Cambridge University Press, 1899.

Ludwig Boltzmann: Wissenschaftliche Abhandlungen. Leipzig: Barth, 1909.

Max Planck: Physikalische Abhandlungen und Vortra¨ ge. Braunschweig: Vieweg,

1958.

Marie Curie: Oeuvres de Marie Sklodowska-Curie. Warsaw, 1954.

Lord Rutherford: Collected Papers of Lord Rutherford of Nelson. London: George

Allen and Unwin, 1962–1965.

Albert Einstein: The Collected Papers of Albert Einstein. Princeton, NJ: Princeton

University Press, 1987–.

Max Born: Ausgewa¨ hlte Abhandlungen. Go¨ ttingen: Vandenhoek & Ruprecht, 1963.

Niels Bohr: Collected Works. Amsterdam: North Holland, 1972.

Piotr Kapitza: Collected Papers of P.L. Kapitza. Oxford: Pergamon Press, 1964–1985.

Fr´ed´ eric Joliot: Oeuvres compl`etes scientifiques de Fr´ed´ eric et Ir `ene Joliot-Curie.

Paris: Presses Universitaires de France, 1961.

Enrico Fermi: Collected Papers. Chicago, IL: University of Chicago Press, 1962–1965.

Werner Heisenberg: Gesammelte Werke. Munich: Piper, 1984.

Paul Dirac: Collected Works of P.A.M. Dirac: 1924–1948. Cambridge: Cambridge

University Press, 1995.

Hideki Yukawa: Scientific Works. Tokyo: Iwani Shoten, Publishers, 1979.

Acknowledgements

In an academic historical work it is usual to document almost every statement.

Here this would be inappropriate, but historians and others who might

wish to do so should have no difficulty in identifying the relevant sources.

Where full-scale biographies exist for the remarkable physicists featured in

this book I have, of course, made use of them; the most important and recent

have already been mentioned above.

The profiles of Louis de Broglie and Piotr Kapitza are largely based

on their obituaries in the Biographical Memoirs of the Royal Society. The

profile of J. J. Thomson is based on the memoir by his grandson David in [34].

For the other profiles the principal sources used are listed above according

to the following key:

Galileo [6, 36, 37, 38, 55, 73, 95, 101, 106], Kepler [3, 20, 73], Huygens

[1, 4], Newton [42, 79, 84, 109, 110, 112]; Franklin [2, 24, 29, 39]; Boscovich

[114]; Cavendish [5, 69, 118]; Coulomb [2, 39, 49]; Laplace [48]; Rumford [13,

14]; Fourier [56, 63]; Young [91]; Amp`ere [2, 39, 67]; Oersted [2, 39]; Ohm

[2, 39, 48]; Faraday [2, 18, 52, 59, 68, 115]; Green [17]; Joseph Henry [29,

85]; Helmholtz [15, 74]; Kelvin [71, 102, 117]; Maxwell [2, 28, 39, 53, 108];

Gibbs [99, 111]; Rayleigh [77, 107]; Boltzmann [12, 22]; Ro¨ ntgen [51, 87]; J.J.

Thomson [34]; Planck [60, 93]; Bragg [19]; Marie Curie [25, 31, 32, 50, 92,

94]; Millikan [70, 81]; Rutherford [16, 40, 116]; Lise Meitner [96, 103]; Hahn

[57, 58, 66]; Einstein [11, 45, 64, 65, 88, 113]; Ehrenfest [72]; Born [10]; Bohr

[9, 46, 82, 89, 98]; Lindemann [8]; Schr ¨ odinger [83]; Bose [23], Joliot [25, 54];

Fermi [43, 44, 100]; Heisenberg [21, 61, 62, 97]; Dirac [75, 76]; Oppenheimer

[104]; Goeppert-Mayer [33], Yukawa [80, 120]. The sources of the longer

quotations in the text are as follows:

Franklin: ‘To determine the question’/ ‘the doctor having published’ [24]

Laplace: ‘the algebraic analysis soon’/ ‘At four in the afternoon’ [48]

Fourier: ‘first causes are not known’ [56]

Rumford: ‘I shall withhold’ [14]

Young: ‘he was not a popular physician’ [91]

Oersted: ‘In my family I am’ [39]

Green: ‘For all his six years’ [17]

Helmholtz: ‘had seriously to think’/ ‘We were sitting in’/ ‘Professor Klein came in’/

‘In his whole personality’ [74]

Maxwell: ‘James Clerk Maxwell still occasioned’/ ‘It was Maxwell who’ [53]

388 Acknowledgements

Gibbs: ‘Though but a few of them’/ ‘Gibbs cannot be given’/ ‘A little over medium

height’ [111]

Kelvin: ‘The dear Kelvins arrived’ [71]

Boltzmann: ‘Erdberg has remained’/ ‘He never exhibited his superiority’/ ‘Boltzmann

has no inhibitions’ [12]

Ro¨ ntgen: ‘he had a well-spread nose’/ ‘He had a penetrating gaze’ [51]

Thomson: ‘in all his theories’ [34]

Planck: ‘Planck loved happy’ [60]

Millikan: ‘I do not think’ [70]

Rutherford: ‘Rutherford’s book has no rival’/ ‘This effect though to all’/ ‘The

Rutherfords lived’ [16]

Einstein: ‘He was a very well-behaved child’ [45]

Ehrenfest: ‘In his usual way’ [72]

Born: ‘The theoretical research’ [10]

Bohr: ‘Father always took an interest’/ ‘The discussions between’ [82]

Lindemann: ‘worked in Professor Nernst’s laboratory’/’many pilots’/ ‘I have often

pondered’/ ‘he came to Oxford’/ ‘If we had some interesting guest’ [8]

Schro¨ dinger: ‘extremely stimulating and impressive’/ ‘for some years already’ [83]

de Broglie: ‘This little brother’/ ‘Demobilized in 1919’ / ‘Having experienced myself’/

‘He greeted me with great courtesy’. Louis de Broglie by A. Abgrem, Biographical

Memoirs, Royal Society, 34 (1988).

Kapitza: ‘Today the crocodile’ Piotr Leonidovich Kapitza by D. Schoenberg, Biographical

Memoirs, Royal Society, 31 (1985).

Fermi: ‘Fermi possessed a sure way’ [100]

Most of the portraits reproduced are taken from the collected works of the subject,

listed above; the sources of the remainder are as follows:

Isaac Newton: Courtesy of the National Portrait Gallery, London.

Roger Boscovich: unknown

Henry Cavendish: Bridgeman Art Gallery.

Charles Augustin Coulomb: C.C. Gillmor. Coulomb and the Evolution of Physics

and Engineering in Eighteenth-century France. Princeton, NJ: Princeton University

Press, 1971.

Pierre-Simon Laplace: Ecole Polytechnique, Paris.

Benjamin Thompson (Count Rumford): Courtesy of the National Portrait Gallery,

London.

Joseph Fourier: Ecole Polytechnique, Paris.

Andr´e-Marie Amp` ere: J.R.I. Hofmann, Andr´e-Marie Amp`ere. Cambridge: Cambridge

University Press, 1995.

Acknowledgements 389

Georg Ohm: Ritter von Fu¨ chtbauer, Georg Simon Ohm. Berlin: BDF Verlag, 1939.

Michael Faraday: Courtesy of the National Portrait Gallery, London.

Joseph Henry: Smithsonian Institution, Washington.

William Thomson (Lord Kelvin): Courtesy of the National Portrait Gallery, London.

John William Strutt (Lord Rayleigh): Courtesy of the National Portrait Gallery,

London.

Wilhelm Conrad Ro¨ ntgen. The Nobel Foundation.

J.J. Thomson: Courtesy of the National Portrait Gallery, London.

Max Planck: The Nobel Foundation.

William Henry Bragg: Courtesy of the National Portrait Gallery, London.

Marie Curie: The Nobel Foundation.

Robert Millikan: The Nobel Foundation.

Ernest Rutherford: Courtesy of the National Portrait Gallery, London.

Lise Meitner: Royal Society, London.

Otto Hahn: The Nobel Foundation.

Albert Einstein: Lotte Jacobi Collection, University of New Hampshire.

Frederick Lindemann: Royal Society, London.

Erwin Schr ¨ odinger: Royal Society, London.

Satyendranath Bose: Santimay Chaterjee et al. (eds.). S.N. Bose: The Man and his

Work. Calcutta: S.N. Bose National Centre for Basic Sciences, 1994.

Louis de Broglie: Royal Society, London.

Maria Goeppert-Mayer: The Nobel Foundation.

Fr´ed´ eric Joliot: Royal Society, London.

Paul Dirac: Courtesy of the National Portrait Gallery, London.

Robert Oppenheimer: Royal Society, London.

Hideki Yukawa: The Nobel Foundation.