Titans at Breakfast
In the blue corner, at five feet nine inches – tall for a physicist - with a café noir and a
butter croissant -the genius from Germany, no, Switzerland, no Germany – welcome
to the Citizen of the World, Albert Einstein! In the red corner, big-boned but slightly
shorter – all the better to understand the inner atom –with a café au lait and a plain
croissant - from Denmark, Niels Bohr!
The clashes between the two giants of twentieth century physics lasted more than three
They began at the Solvay Conferences in Belgium, in 1927 and 1930. In reality, those tough
encounters involved no boxing gloves, no pistols, swords, teeth, claws or knives; just sheer
brain power. The stakes were certainly high, but the worthy combatants were two middle-
aged European gentlemen in three-piece suits, taking coffee and croissants and perhaps a
little orange juice. Their early and main bouts took place in the art deco breakfast room of the
Metropole Hotel, in Brussels, the central dining area for all Solvay Conferences.
Solvay sounds like it may be something vaguely Norwegian, by Grieg. In fact, Ernest
Solvay was a Belgian multimillionaire who had amassed his fortune with a brand of caustic
soda for drains. Perhaps inevitably, Ernest Solvay had a pet theory and, since the late 1890s,
he had been inviting the world's greatest scientists to stay at the splendid Hotel Metropole in
what was in every sense a vain attempt to convince them of his own worth as a physicist.
At the Fifth Solvay Congress, Einstein and Bohr embarked upon one of the greatest
intellectual controversies of all time. It has been compared with the debates between Newton
and Leibniz, but Sir Isaac and Gottfried were each claiming to have been first to described
the Calculus. With them it was a matter of priority, of ego. Niels and Albert were arguing
about the way things are, the realities of nature and the nature of reality, the essence of
physics and the very soul of Science. Though no one said so at the time - or since - Albert
Einstein seems to have been especially worried that science was becoming too girly.
The Hotel Metropole is a Belle Époque establishment on Place de Brouckère, near the Stock
Exchange and the business centre of Brussels. The two scientists might have been properly
dressed for such a bourgeois milieu, but Einstein’s rather rumpled suit, steel-wool-like hair
and spivvy moustache would have earned him disdain - and worse - had he not been one
of the most famous people on the planet, his cultivated style an excellent form of branding,
his professed lack of vanity in itself a sort of vanity. However much he might have looked
in the flesh like a failed music hall comedian - he was certainly getting his laughs - Albert
Einstein’s name had already by then become a byword, a synonym for genius.
So it was odd to see him in that particular group of people gathered around a breakfast table
in the Metropole Hotel on an October morning in 1927. A few of the other people sipping
coffee and munching at their patisserie that day looked as if they might be fairly bright,
but the man doing most of the talking looked out of place among them and in such smart
surroundings. He was not badly dressed, but he was big-boned and somewhat lunkish. He
had an empty look in his eyes, lowering brows and a protruding lower lip.
Niels Bohr was frequently described as wandering through the world as if in a trance. He
was something of a Danish football hero - although, playing goalkeeper, he did once have
to be yelled at by panicked spectators when the ball threatened to roll past him. Bohr was
working out a few calculations on the goalpost.
Because of his dreamy demeanour, Niels Bohr opened himself up to be underestimated.
But of course it didn't take long for one to realise that he was an extraordinary human being.
Few people in his or any field can have been so revered, and fewer if any minds have worked
in such wonderful ways. Rarest of all, considering his background and interests, was Niels
Bohr's capacity to love. It was evident in his extraordinarily tender relationship with his wife,
Margrethe, in the glorious fun he had with his sons and, perhaps most unusual of all, in his
relationship with his younger brother. Harald Bohr was an outstanding mathematician and
played football for Denmark. Niels played soccer well, but not that well and yet he genuinely
rejoiced at his brother's triumphs. No-one had ever seen two boys from the same family so
supportive and so close, nor any older brother so free of sibling rivalry, or any jostling at all.
Niels Bohr had what today would be called a well-developed feminine side.
Albert Einstein, in his science as in his life, was less female than male. He disliked all those
elements which made quantum mechanics too much like an immature fräulein, conduct that
was unpredictable, disorderly, wayward and which led serious scientists to be - horror of
horrors – subjective. Einstein was more interested in the ‘outer’ than the ‘inner’, he favoured
the rational over the irrational and hard evidence to him was preferable to rhetoric, just as, for
him, reason always had to take precedence over emotion. The theories pertaining to quantum
mechanics challenged everything he stood for and everything he and many others like him
Einstein's Theories of Relativity had not overthrown the ideas of Newton. Indeed it was
the Newtonian universe that Einstein wished to preserve and which clearly Bohr and his
supporters were seeking to dismantle. Isaac Newton was born on Christmas Day 1827. In
October 1927, Albert Einstein was well aware of that approaching 200th anniversary as the
At the 1927 Conference, there were a number of Young Turks who were intent on proving
themselves. And prove themselves they certainly did, honoured in due course with the
approval of their peers, Nobel Prizes and the positive judgment of history. These included
Wolfgang Pauli, Werner Heisenberg and P.A.M. Dirac, all three of whom were at that time
around 26 years old. For some reason 26 seems to be a very special age for genius. That
is not only the case in the world of science; for example Orson Welles was 26 when he
directed 'Citizen Kane'. But it is startling to note that Albert Einstein, Werner Heisenberg,
PAM Dirac, Wolfgang Pauli, Richard Feynman and a host of other ground-breaking
scientists and mathematicians did their most important work when they were around the
age of 26, which also happens to be, for some reason, a popular time for drug-addicted rock
There were older theorists there too. Einstein thought they should have known better. But,
whatever the stature of his colleagues, Niels Bohr was the acknowledged leader of the new
quantum revolution; and at the conference it was he who tended to speak for them all. It is
hardly believable that Niels Bohr would have been the spokesperson for anyone or anything.
The fact that he was chosen to talk is a tribute to what he had to say, rather than the way he
said it - or mumbled it. In 1946, it was arranged for Bohr to meet with Churchill to discuss
the urgent question of the atom bomb. But Niels Bohr’s blurry muttering infuriated the
British politician, who took him to be either a maniac or an imbecile. Churchill had to be
restrained from calling for Bohr's arrest
Over the past few years, I have been lucky enough to chat with – or formally interview –
some of the world’s eminent physicists, none of whom regard themselves as performers, but
all of whom have perfected their Niels Bohr anecdotes and imitations.
Steven Weinberg's secretary warned me that it would be inappropriate for Professor
Weinberg, a Nobel Prize winner after all, to become too informal in a video interview I was
about to record with him. But within minutes, Weinberg was acting out the Danish-accented,
gobbling, spluttering manner with which Bohr tried, usually without success, to express
himself. Weinberg's wife was once seated next to Bohr at a dinner party and at no point in
the entire evening did she understand any part of any syllable of any single word uttered by
The physicist and author Freeman Dyson told me that during a stay in America, Bohr saw
it as his noble task to make a television programme in which he explained the new physics to
the widest possible lay audience. By lunchtime, after a morning of Bohr’s flubbering, the TV
programme’s director had lost the will to live and begged J. Robert Oppenheimer, a lucid and
charismatic science explainer, to take Bohr's place. Urgently.
Another winner of the Nobel Prize Murray Gell-Mann, whom I'd only just met socially,
launched into a bubbling, slightly jerky babble, his head nodding as if he were a cat with a
hairball, his blue eyes gleaming through his spectacles with wonder. Niels Bohr’s speech
patterns were to Gell-Mann as fascinating as his famous quarks.
At the Solvay Conference, over meals and as part of the main business of the day, Niels
Bohr, in his own halting way, stated that in the quantum realm, certainty and causality did
not exist at all. Everything at the subatomic level, said Bohr, was subject to randomness. For
Bohr and the theorists who had built up such a devastating picture of nature at the subatomic
level, none of the laws by which scientists - and especially physicists – had operated for
centuries applied. There was only chance, tendency, probability. Light could be made up of
particles or waves, but that depended upon the apparatus the experimenter might choose, so
that now scientists knew the results of their tests in advance. There was even a suggestion
that the light and matter being tested were interacting with the scientist’s mind.
In short, Bohr had come to the conference to say that one could no longer speak of
a ‘reality’ independent of measurements and observations.
All of this was worse than alien to Albert Einstein, who could express himself lucidly
when he wrote and with clarity and wit when he spoke. Einstein's opinion of quantum
mechanics was that it was ‘the system of delusions of an exceedingly intelligent paranoiac.’
To him, quantum mechanics and all its works had been ‘concocted of elements of incoherent
Before, during and after the Fifth Solvay Conference, Einstein kept up a correspondence
with his great friend Max Born, a supporter of Bohr and of quantum mechanics and, by
the way, Olivia Newton John’s grandfather. In one of his best known letters, Einstein told
Born: ‘Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet
the real thing. The theory says a lot, but it does not really bring us any closer to the secrets of
The Old One…’ Einstein was fond of saying that a good joke shouldn't be repeated. But he
certainly repeated the following two lines many times for more than a quarter of a century,
after he first wrote them to Max Born: ‘Quantum mechanics may not be wrong but it is at the
very least Incomplete. I am convinced that God does not play dice with the universe.’
Niels Bohr’s response to Einstein's one-liner about God and dice has also been endlessly
repeated. He is supposed to have said, ‘Einstein, stop telling God what to do with the
universe’, or something equally catchy. Bohr was a studiously polite gent, though, so it is
unlikely that he would actually have sought to put Einstein down and impossible that he
would have bossed him. Einstein was indisputably a great man, not just of his epoch, but of
all time. Everything he did and everything he said was treated with awe. Wolfgang Pauli was
a notorious iconoclast, fond of saying to even the most elevated of colleagues,
‘That’s not even wrong’, or remarking to some uppity tyro, ‘So young and already
unknown’. But even Pauli, in Einstein's presence, was just that little bit different.
At the time of that Solvay Conference, Einstein was 48 but seemed to be older. Niels
Bohr was still a little ungainly at the age of 42, as can be seen in a series of snapshots taken
by an amateur photographer and professional scientist by the name of Paul Ehrenfest.
Einstein regarded Ehrenfest as one of the greatest teachers in the world. In the course of
the conference, Ehrenfest burst into tears because he believed that Einstein was being
stubborn and was dismissing his younger colleagues just as Einstein in his time had himself
experienced the dismissal of his seniors. More to the point, Ehrenfest, who idolised Einstein,
found himself siding with Niels Bohr.
You wouldn't know it though, from the photographs he took. In all of his rather amateurish
snaps, Ehrenfest has captured the eccentricities of Einstein and Bohr, dapper in their coats
and hats, chatting earnestly and even reclining, deeply relaxed, with smoke billowing around
them. But not all of the photos are flattering and, in one shot, Bohr looks as if he has only
Still, Niels Bohr would grow into his face and into himself. His hairline would recede, bags
and jowls would appear, his eyes would acquire clarity and focus; he accrued renown and
power, sailed, skied and walked a little less, ate and drank a little more. And so, in time,
he acquired great gravitas. Einstein would also mature. He, too, loved to get away from his
desk and sail, or take long walks, so that people who expected to meet an effete intellectual
were surprised to find how like a sportsman he was, with his strong limbs, powerful chest
and oarsman’s shoulders. Consciously easy with his own lack of self-consciousness,
uniquely unconcerned by the time any problem might take, Albert Einstein strode in his own
extraordinarily ordinary way towards a celebrated cheeky, solitary sainthood.
Einstein's friend, Max Born said, 'The generation to which Einstein, Bohr and I belong was
taught that there exists an objective physical world, one which unfolds itself according to
immutable laws. And it does so independent of us. We had come to believe that we were
watching such processes in the same way that an audience watches a play in a theatre.
Einstein still believes that this should be the relationship, that there should be a separation
between the observer and the observer’s subject.’
Einstein himself had helped to raise the curtain on the entire, marvellous subatomic show
– the quantomime if you like - loving the spectacle, but not expecting to be yanked in and
involved with the action. For Einstein, it was the basis of all natural science that belief in the
external world was independent of the perceiving subject. So when Heisenberg and Bohr said
that the observer affects that which is being observed, Einstein didn't like it. He didn't like it
Einstein's first chosen target was Heisenberg's Uncertainty Principle. And although he had
not spoken during the official conference in Brussels, confining himself to remarks at meal
times, he now took part in an informal discussion in the hall itself. The tension was palpable.
One can understand Heisenberg's theory by imagining a luxury liner steaming over the
ocean. At any given minute, the ship's captain will know with great accuracy exactly
how fast his vessel is going, its precise position and how much energy the ship’s engine
requires. Heisenberg had shown that it was not possible, ever, to have all of those simple
bits of information at the same time in the quantum realm. One could know a subatomic
particle’s position but not, simultaneously, its momentum and its energy. One could know its
momentum, or its energy, but not without giving up knowledge of its position.
Heisenberg was a scientist and in this case was not really making a philosophical point. He
was trying to create a tool with which researchers could work. Nevertheless, Einstein felt that
however small the entities we study may be, science depends on our being able to examine
and measure each and every one of nature's moving parts without affecting them and without
Einstein believed that a gadget which he had dreamed up would demolish the central tenets
of quantum mechanics. Anyone who knew Einstein and Bohr knew that they both loved
gadgets. Einstein described a stream of electrons flying through an aperture and towards a
photographic plate. In an atmosphere of silence and anxiety, Albert Einstein explained that,
clearly, one could see, on the photographic plate, the exact position of every single particle
and know the precise moment at which it arrived at the plate. One would also know the
momentum of each particle: the speed of light.
Thus, Einstein claimed, it was possible to know the position and the momentum of any
particle simultaneously. Heisenberg was wrong. Einstein was right. Quantum mechanics was
Heisenberg was extremely uneasy. Wolfgang Pauli said, ‘Ach ja. It'll be all right it'll be all
right all right.’ But he didn't sound all that convinced.
Slowly, Niels Bohr leaned forward. He explained, as he and his faithful team had explained
many times before, that, in dealing with entities at the subatomic level, it is fiendishly
difficult to separate them off from the apparatus. Einstein retorted that he had just shown
precisely how the particles could be separated off. That was the point. Niels Bohr explained
gently that as the electrons passed through the aperture, they would inevitably disturb
their brother and sister electrons as well as unavoidably causing a certain jarring, however
minimal, of the aperture itself. Einstein proposed a makeshift solution.
Again, Bohr patiently explained how it could not be - and would not ever be - possible in
the Einstein's example to separate off the particles from the apparatus.
Einstein was revisiting his own worst nightmare. His argument was demolished.
To professional physicists the exchanges and reversals involved were reminiscent of a
courtroom drama. For laypeople, it might be a little more difficult for to understand the
niceties of the episode. The sensational fact is that Einstein, the great genius, lost that round
of the debate. Suffice it to say that Einstein was defeated by details, details which, for all
their huge implications, could not have been more miniscule.
After all, the two men were arguing about the utterly weird conduct of particles smaller than
Do scientist’s personalities affect the ideas they favour? Science is supposed to be objective,
impersonal and value free. But scientists are human beings. They are not machines. And,
although Einstein and Bohr had supremely powerful minds, they were not gods. They were
human. If they conformed to any archetype, then they were holy fools - self-deprecating,
clown-like figures, cute enough to be mothered and given cocoa.
Except cocoa and cuddliness were not entirely Albert Einstein's style. He was a well-
mannered and approachable fellow, but he always had about him a quality of ‘apartness’.
He himself said, ‘Between me and other people there has always been some kind of glass
pane.’ It is unknown whether that pun was intended. It is also not known what or how much
Einstein felt when in 1902 he and his wife, Mileva, gave a daughter away. Not in marriage.
The baby girl already had a name, Lieserl. Mileva had come from Hungary, but in fact she
was Serbian and it was to Serbia that Lieserl was sent in 1902. Maybe Lieserl died of scarlet
Mileva and Albert Einstein had two other children, Hans Albert and Eduard. Hans Albert
did seminal work in the field of hydraulic engineering. Eduard suffered a schizophrenic
breakdown and died in a Swiss clinic. Neither of those boys experienced closeness or
affection from their father. Perhaps Einstein suffered from a form of autism.
Einstein was married to Mileva for 17 years. As part of the divorce settlement, he gave the
Nobel Prize money - which he confidently expected to win - to Mileva for her upkeep and for
the care of her children. Mileva actually cited his work as co-respondent. Towards the end of
their marriage, Albert Einstein actually put forward a contract in which he imposed a series
of conditions upon his wife. They included ‘A. You will make sure, 1. that my clothes and
laundry are kept in good order; 2. that I will receive my three meals regularly in my room; 3.
that my bedroom and study are kept neat, and especially that my desk is left for my use only.’
Other stipulations included: ‘B. You will renounce all personal relations with me insofar
as they are not completely necessary for social reasons’ and ‘you will stop talking to me if I
request it.’ It is a sign of those times - and much else besides - that Mileva actually accepted
those conditions, even his instruction that their ‘personal aspects must be reduced to a tiny
remnant.’ For his part, he told her ‘In return, I assure you of proper comportment on my part,
such as I would exercise to any woman as a stranger.’
Meanwhile he was already dating his next wife. Like Darwin, Einstein married his first
cousin. His cousin’s name was Elsa and while he was courting her, he admitted to her that he
treated Mileva ‘as an employee whom I cannot sack.’
There must have been a certain amount of compartmentalisation in Einstein's psyche. He
spent a lot of time answering letters from children, reassuring little girls it was not bad to be a
daughter, encouraging youngsters who struggled, as he did with mathematics and treasuring
letters from little boys who invited him along on their space trips because they needed good
scientists. My own mother-in-law lived very near to Einstein’s house in Berlin during the
1920s. She remembered him as a lovely man, kind and open. Einstein often bought sweet
ices for her, her sister and their friends. Indeed in my family home to this day, we refer to the
celebrated theorist as Albert Ice Cream.
Albert Ice Cream was not present at the birth of Lieserl, the daughter whom he gave away.
He never met her. It is not known whether he held either of his sons in his arms.
Niels Bohr’s arms were not strong enough to hold on to his son. They were at sea and
Niels’s beloved, eldest boy was washed overboard. Niels Bohr was a powerful man, not
the clichéd boffin at all, athletic and strong but he simply could not hold on to his firstborn
child. The drowning of that lad haunted Niels Bohr and his adored wife Margrethe for the
rest of their lives. They never got over it. Another of their children succumbed very early to
meningitis. This death also caused Niels and Margrethe untold pain. In all, the remarkably
affectionate couple had six children. And the four who survived went on to lead the happiest
of lives in a house that was also a research Institute. It was said in the world of physics that
all roads led to number 17 Blejdamswei. Einstein stayed away, though on the mantelpiece of
his office Niels Bohr always kept a little bust of his old adversary, looking like a chirpy court
In all the group photographs in that Institute, Bohr always crosses his leg to the left. And
on the wall to this day there is a horseshoe. Scientists are not supposed to believe that such
objects might bring you luck, but Bohr said that whether he believed in it or not, it worked.
There were certainly tragedies in Niels Bohr's life, but there was also elation.
One of the first Danish words Bohr’s young champion researchers would learn would always
have been ‘hygge’ (It almost rhymes with ‘humour’).
‘Hygge’ means the art of creating intimacy. Niels and Margrethe Bohr had, of course, the
kind of marriage the rest of us can only wonder at. So one might think that, because ‘hygge’
sounds a little like ‘huggy’, it means something close to ‘cosy’. But that’s not quite right.
Hygge has to do with affection, yes, and comfiness. But it mainly has to do with having a
Carlsberg, the beer people, sponsored the Institute and most of the scientific celebs who
came to live there were fond of a drink. They could sleep as late as they liked. Their mail
was always laid out for them. There were always snacks around and tea and coffee. They
went to the movies together, they devised elaborate practical jokes, they played cards. The
floor around the table tennis table was worn down and furrows were forming. The Bohr boys
hurtled around and were always full of mischief.
Since as far as Bohr was concerned, there was always fun to be had, he challenged his
fellow physicists one evening to a shoot out, after they'd been to see a cowboy movie. Using
toy pistols lent to him by his sons, he invited all-comers to see if they could pull their guns
out of their holsters faster than he could. He won every time. His explanation was that if
one is rational, if one thinks to precisely on th’event, instead of being intuitive, instead of
improvising and reacting on the spot, one isn’t going to be quick on the draw.
It is also possible to be too quick on the draw. Paul Ehrenfest was. Intellectually and
personally, new ideas in physics frequently take their toll. Einstein became seriously ill and
almost died before he had completed his theory of relativity. Heisenberg and Schrödinger
suffered physical and mental anguish as they wrestled with the problems of quantum theory.
Ehrenfest had started off referring to the quantum theorists as ‘Klugscheisser’ – clever
excrement. Then, sobbing, he had sided with them against his dearest friend, Einstein. But
then Paul Ehrenfest went under. He wrote an undelivered letter to Einstein, saying: ‘In
recent years it has become ever more difficult for me to follow the developments in physics
with understanding. After trying, ever more enervated and torn, I have finally given up
in DESPERATION. I have completely lost contact with theoretical physics. I feel myself
incompetent to have even the most modest grasp about what makes sense... This makes me
completely weary of life... I have no other practical possibility than suicide, and that after
having first killed Wassik.’ Wassik was his son, an engaging young lad who had Down’s
Syndrome. Ehrenfest shot his son and then himself.
At the next Solvay Conference in 1930, the stage was set for something real, something
earnest. Again coffee and croissants were brought. And again, Albert Einstein had devised
a gadget. This time he was attacking a variation of Heisenberg's idea, for Heisenberg stated
that just as it was impossible to ascertain simultaneously the position and the momentum of a
particle, so one could not know at the same time a particle's position and its energy.
Again Einstein wanted to show that measurements at the quantum level were perfectly
possible. He proposed that a box full of light be weighed. Then that a single particle of light be
released. And that the box be weighed again.
This might mean very little to anyone was not a physicist perhaps, but here was Einstein
brilliantly in the ascendant. What he had shown - and clearly shown - was that it was quite
possible to know both the energy and the position of a particle. Apparently Niels Bohr
wandered from group to group, from table to table and from physicist of physicists all that
morning, throughout the day and into the evening too. He was convinced by Einstein's
argument but it did not accord with his experience of nature. He stayed up well beyond
midnight, worrying, pondering and thinking hard about Einstein’s devastating gadget.
Next morning, for the usual breakfast in that very same room in the Metropole Hotel, Bohr
greeted Einstein. Coffee, orange juice and croissants were brought. Bohr leaned forward,
his thickening frame stretching his good suit and making his chair creak softly. Quietly and
meticulously he showed Einstein that the box with the light in it would have to be on a scale
that had springs. Between the first and the second weighing of the box, Bohr, explained, the
springs and the box would move into a different gravitational field.
And as Einstein knew, knew only too well, the fact that the box was in a different
gravitational field meant that its weighing could not possibly remain unaffected.
But there is another way of saying this.
Niels Bohr had won the debate with Einstein using Einstein's own theory of relativity.
Bohr and Einstein kept up their argument for thirty years and more. Every time they met,
they would greet each other and go straight back to their dispute. They always talked past
each other. Neither managed to convince the other. And one colleague told me that Bohr
would argue against Einstein after Einstein had died. It was his warm-up.
Einstein’s secretary, Helen Dukas, reported that Einstein held Bohr deeply in his heart.
Which is perhaps why, on one well-known occasion, Einstein crept up behind Bohr and
startled him, by grabbing his tobacco pouch. He explained, ‘My doctor has told me not to
buy tobacco. So I am forced to steal it.’
In 1962, after a life of ‘hygge’, a life spent understanding the relationships between
people, between atoms and between nations - and after fifty years of marriage - the last
word Niels Bohr uttered on earth was ‘Margrethe’ and he died in his wife’s arms in that
house at 17 Blejdamswei in Copenhagen.
On a blackboard near him as he died, there was a sketch of the gadget that Einstein proposed
30 years earlier. The box full of light, the shutter and the scales. Bohr was reassuring himself
one last time of the way of the debates and the breakfasts and his knockout blow.
In the physics community nowadays it is not accepted at all that Niels Bohr won. As a matter
of fact, the vast majority of physicists today think that Einstein was absolutely right, that
quantum mechanics is Incomplete. The old seer, as always, soared and saw further than the
rest. And although he lost a couple of rounds, Einstein still might win on points.
Einstein stood apart from Copenhagen, from Bohr and from the rest. Did he need that
In 1955, he died alone, except for a nurse who happened to be in his ward.
And when the world’s press asked if he had said anything she said, ‘Yes.’
They asked, what did he say? What were Einstein’s last words.
‘I’m sorry,’ said the nurse. ‘I don’t speak German.’