Physicists From The Netherlands

"You can forget facts but you cannot forget understanding."

"The gravitational force is the oldest force known to man and the least understood."

"I am impressed by the great limitations of the human mind. How quick are we to learn, that is, to imitate what others have done or thought before. And how slow to understand, that is, to see the deeper connections. Slowest of all, however, are we in inventing new connections or even in applying old ideas in a new field."

"We must expect that these German scientists, once they get here, will continually try to defend the actions of Germany before and during the war. Their background and education wiil have supplied them with the necessary arguments. The rocket specialists have at times tried to convince us that they worked on rockets only for the purpose of scientific research. The German atomic scientists, who failed in their attempt to make a bomb, planned to deny that they wanted to make one."

"For although it is certainly true that quantitative measurements are of great importance, it is a grave error to suppose that the whole of experimental physics can be brought under this heading. We can start measuring only when we know what to measure: qualitative observation has to precede quantitative measurement, and by making experimental arrangements for quantitative measurements we may even eliminate the possibility of new phenomena appearing."

"Goudsmit stumbled to fame in 1925. For more than a decade, Niels Bohr and others had been trying to develop a quantum theory of the atom, mostly by studying atomic spectra. These consist of the energies (specific to each element) of the quanta of light, or photons, that an atom’s electrons can absorb or emit. Physicists had been struggling to make sense of anomalies that appeared in spectra when atoms were immersed in a magnetic field: some spectral levels mysteriously split into two or more. Goudsmit and his friend George Uhlenbeck, both graduate students at Leiden University in the Netherlands, had an idea. They proposed that the splitting could be explained if the electron had an intrinsic ‘spin’ that could assume one of two directions: clockwise or anticlockwise. Other physicists had discarded this idea, seeing it as marred by conceptual difficulties. ... Soon, researchers including Paul Dirac explained away the conceptual difficulties. Quantum spin was born."

"Secrecy, it was impressed upon us at the outset, was imperative, despite the fact that our code name, ALSOS, seemed a give-away, being the Greek translation for Groves. Since General Groves was in complete charge of all Army activities relating to the atom bomb project, the inference did not take too much imagination. To make it even more obvious, the Mission's vehicles had license plates bearing the Greek letter Alpha."

"If only we could get hold of a German atomic physicist, we felt, we could soon find out what the rest of them were up to. To us physicists the problem seemed very simple. Even those of us who were not working on the atom bomb project knew pretty well what was going on over here. No amount of military security could have prevented us from knowing, difficult as it was for the military to understand this. Active scientists engaged in the same general field of research inevitably form a kind of clan; they work closely together and know all about each other's specialities and whereabouts. You can't take a group of key scientists from their accustomed haunts and have them disappear in some remote place in New Mexico, together with their families, without their colleagues who are left behind wondering about it and deriving the right conclusions. The same thing, we knew, would be true of the Germans."

"In short, we knew very little about the German uranium project, and what little we knew we almost invariably interpreted in their favor. In the long run, this was probably all to the good, since it accelerated our own work enormously. But in those days, before the invasion of Europe, we would have given a great deal to know more."

"In my study hangs a fine old horse shoe, which I found in an abandoned Western ghost town. I don't believe in superstitions, but it is supposed to work even for a nonbeliever2. It hasn't so far."

"... I don't like the history of physics, I have always been against the way in which the historians wrote about it in earlier days. Nowadays it is better, someone like Martin Klein, that is real, he brings something new. But the earlier historians always described physics as if it had been done by three and four people and they forgot that these famous people could only do their work because of the many others who also made contributions. ..."

"I did all the problems a little different from the rest of the class."

"Dit model wil het Higgs deeltje om een zinnige theorie te zijn."

"Great physics does not automatically imply complicated mathematics!"

"Gerard is a Dutchman. The Dutch are the tallest people in Europe, but Gerard is short and solidly built, with a mustache and the look of a burgher. Like Feynman, 't Hooft has a strong competitive streak, but I am sure that I never got the better of him. Unlike Feynman, he is a product of old Europe — the last great European physicist, inheritor of the mantle of Einstein and Bohr. Although he is six years younger than I am, I was in awe of him in 1981, and rightfully so. In 1999 he was awarded the Nobel Prize for his work leading to the Standard Model of elementary particles."

"Deterministic underlying theories for QM are possible. They are still difficult to construct, but simple "toy models" are possible. These models are not good enough to replace today's existing quantum theories."

"... trying to solve a paradox will lead to new kinds of understanding. And I think that the problem of subjecting black holes to quantum mechanics is a fundamental paradox of the same nature, and the same depth, and the same importance as the paradox that Max Planck was studying at the beginning of the twentieth century."

"When investigating theories at the tiniest conceivable scales in nature, almost all researchers today revert to the quantum language, accepting the verdict from the Copenhagen doctrine that the only way to describe what is going on will always involve states in HIlbert space, controlled by operator equations."

"In practice, quantum mechanics merely gives predictions with probabilities attached. This should be considered as a normal and quite acceptable feature of predictions made by science: different possible outcomes with different probabilities. In the world that is familiar to us, we always have such a situation when we make predictions. Thus the question remains: What is the reality described by quantum theories? I claim that we can attribute the fact that our predictions come with probability distributions to the fact that not all relevant data for the predictions are known to us, in particular important features of the initial state."

"The usual no-go theorems telling us that hidden variables are irreconcilable with locality, appear to start with fairly conventional pictures of particle systems, detectors, space and time. Usually, it is taken for granted that events at one place in the universe can be described independently from what happens elsewhere. Perhaps one has to search for descriptions where the situation is more complex. Maybe, it needs not be half as complex as superstring theory itself. The conventional Copenhagen interpretation of quantum mechanics suffices to answer all practical questions concerning conventional experiments with quantum mechanics, and the outcome of experiments such as that of Aspect et al can be precisely predicted by conventional quantum mechanics. This is used by some to state that no additional interpretation prescriptions for quantum mechanics are necessary. Yet we insist that the axioms for any "complete" quantum theory for the entire cosmos would present us with as yet unresolved paradoxes."

"Quantum mechanics as it stands would be perfect if we didn't have the quantum-gravity issue and a few other very deep fundamental problems."

"On your way towards becoming a bad theoretician, take your own immature theory, stop checking it for mistakes, don't listen to colleagues who do spot weaknesses, and start admiring your own infallible intelligence."

"If you really want to contribute to our theoretical understanding of physical laws — and it is an exciting experience if you succeed! — there are many things you need to know. First of all, be serious about it!"

"The reader may ask why in this book string theory and supersymmetry have not been discussed. ... The fact is that this book is about physics and this implies that the theoretical ideas discussed must be supported by experimental facts. Neither supersymmetry and string theory satisfy this criterion. They are figments of the theoretical mind."

"We understand many things about particles and their interactions, but this and other mysteries make it very clear that we are nowhere close to a full understanding."

"... de wiskunde (houdt) zich veel meer bezig (...) met bijvoorbeeld de structuur achter iets of met het bouwwerk van iets. Wiskundigen zijn ook niet echt een soort puzzelaars. Degenen die echt wiskundige puzzels oplossen dat zijn de natuurkundigen. Als je het leuk vindt om wiskundige puzzels op te lossen, moet je geen wiskunde maar natuurkunde gaan studeren!"

"... (een flits van inzicht) komt nooit vanzelf, in de zin dat je er geen moeite voor hoeft te doen. Je moet je er echt wel voor inspannen. Er is een mooi spreekwoord voor: “toeval schiet de voorbereide geest te hulp”. Zo’n inzicht komt wel toevallig, maar je krijgt het alleen als je bent voorbereid. Het inzicht komt niet vanzelf."

"Bij natuurkunde heb je een beetje van alles wat: je moet goed zijn in puzzelen, maar je moet ook grote lijnen kunnen zien, belangrijke dingen van onbelangrijke dingen kunnen scheiden, snel nieuwe stof in je kunnen opnemen en snel in een voordracht of artikel de essentie kunnen zien."

"In de mesoscopische fysica moet je echt intuïtie opbouwen, omdat het niet de wereld is die je kent."

"A new man appears abruptly, the ‘suddenly famous Doctor Einstein.’ He carries the message of a new order in the universe. He is a new Moses come down from the mountain to bring the law and a new Joshua controlling the motion of heavenly bodies..."

"I spent every night until four in the morning on my dissertation, until I came to the point when I could not write another word, not even the next letter."

"Once I even took the train to Utrecht, forty miles from Amsterdam, with my yellow star, this star which I still have. Why did I go? I just wanted to visit some friends. I was a little bit crazy, a little bit insane"

"To make a discovery is not necessarily the same as to understand a discovery."

"The rule of the game was never assume that anybody, however honorable, would be able to stand up under torture. If Mr. X, who knew where I was, was caught for some reason, I should move."

"One of the things I learned, one of the strangest things, is how to think."

"For several months I was incapable of feeling anything, completely inaccessible to my feelings — I did not laugh, I did not cry. The second thing was this amazing trauma, where I forgot the names of everyone I knew. That was very strange. I knew who everyone was: this was a friend from high school, this was my cousin, but I had to relearn every name. It was quite striking, that very strong reaction that I had. They have a name for it, I think: posttraumatic stress syndrome. I don't sit here conquering great resistance to talk. It is not my way. I don't suffer the reliving of these memories with tremendous pain. It's very odd, but it's finished for me. That, of course, is never quite true. It isn't finished. I am like all of my generation; we are marked people. But I don't suffer; I can talk to you about it. Most of my family was killed. All of my father's and mother's sisters and brothers and their children, my sister and my old grandfather, they're all gone. Four out of five Jews in Holland never came back after the war — 80 percent."

"On the day we were caught, Lion and I had been talking about writing a memorandum on the fate of the Jewish war children living in hiding or among Dutch families … we were the representatives of the Zionist youth organization. … Lion who had been taking notes of the discussion, put these papers in his jacket pocket when he took a break from lunch. When the Germans caught us they discovered his notes. If those papers had been in my pocket I would have never lived to be seventy. I have led a strange life, a set of complete coincidences."

"I was lucky because the same week that I went to prison the Americans crossed the Rhine and cut off the northern part of Holland, so there was no longer any possibility of being shipped out to a concentration camp. The rail lines were cut. So I was in prison in Amsterdam during the very last days of the war. We were sent to the men's prison and the girls were sent to a women's prison in a different place."

"I knew all the time I was going to get through the war. It was completely irrational, a silly idea, but I was not going to lie down and get myself killed. I was going to get out of it."

"One of the absolute rules I learned in the war was, don't know anything you don't need to know, because if you ever get caught they will get it out of you."

"One of the things I learned, one of the strangest things, is how to think. There was nothing else to do. I couldn't see people, or go for a walk in the forest. All I had was my head and my books, and I thought a lot. I learned, because there was no interruption. I had access to myself, to my thinking. I wouldn't say that I particularly matured. The thinking was physics thinking. I was just short of twenty-two then. I was in hiding for two years and two months, something like that. In all that time I went out very, very little, just once in a great while, after dark. Once I even took the train to Utrecht, forty miles from Amsterdam, with my yellow star, this star which I still have. Why did I go? I just wanted to visit some friends. I was a little bit crazy, a little bit insane."

"I lived altogether in nine different places while in hiding, because whenever something happened, either someone betrayed the place or something happened to someone who knew where I was, I had to move. The rule of the game was never assume that anybody, however honorable, would be able to stand up under torture. If Mr. X, who knew where I was, was caught for some reason, I should move."

"Deliberately or not, every author is of course present in every book he or she writes — even in a scientific text."

"I made a discovery, perhaps known to others but new to me: I need not put myself center stage but can rather place myself at the side, like a Greek chorus. As the curtain rises, I can walk to the center and can speak as follows: I wish to tell you of happenings in the twentieth century, as I witnessed them and reflected upon them. You will see me return to center stage, but only occasionally. Once that imagery had gotten hold of me, I went back to Ida and said yes, I shall try."

"Of course, relative citation frequencies are no measure of relative importance. Who has not aspired to write a paper so fundamental that very soon it is known to everyone and cited by no one?"

"Today we live in the midst of upheaval and crisis. We do not know where we are going, nor even where we ought to be going. Awareness is spreading that our future cannot be a straight extension of the past or the present … The century now approaching its end has been one of indiscriminate violence, it has been perhaps the most murderous one in Western history of which we have record. Yet I would think that what will strike people most when, hundreds of years from now, they will look back on our days is that this was the age when the exploration of space began, the microchip was invented, revolutions in transport and communication virtually annihilated time and distance, transforming the world into a "global village," and relativity theory, quantum mechanics, and the structure of the atom were discovered, in brief that this has been the century of science and technology."

"To make a discovery is not necessarily the same as to understand a discovery. Not only Planck but also other physicists were initially at a loss as to what the proper context of the new postulate really was."

"A number of current theoretical explorations will turn out to be passing fancies..."

"Progress leads to confusion leads to progress and on and on without respite. Every one of the many major advances … created sooner or later, more often sooner, new problems. These confusions, never twice the same, are not to be deplored. Rather, those who participate experience them as a privilege."

"The first thing Bohr said to me was that it would only then be profitable to work with him if I understood that he was a dilettante. The only way I knew to react to this unexpected statement was with a polite smile of disbelief. But evidently Bohr was serious. He explained how he had to approach every new question from a starting point of total ignorance. It is perhaps better to say that Bohr's strength lay in his formidable intuition and insight rather than erudition."