In the years of the First World War, science was dominated at Göttingen as elsewhere by Relativity. But in 1921 there was appointed to the chair of physics Max Born, who began a series of seminars that brought everyone interested in atomic physics here. It is rather surprising to reflect that Max Born was almost forty when he was appointed. By and large, physicists have done their best work before they are thirty (mathematicians even earlier, biologists perhaps a little later). But Born had a remarkable personal, Socratic gift. He drew young men to him, he got the best out of them, and the ideas that he and they exchanged and challenged also produced his best work. Out of that wealth of names, whom am I to choose? Obviously Werner Heisenberg, who did his finest work here with Born. Then, when Erwin Schrödinger published a different form of basic atomic physics, here is where the arguments took place. And from all over the world people came to Göttingen to join in.
It is rather strange to talk in these terms about a subject which, after all, is done by midnight oil. Did physics in the 1920s really consist of argument, seminar, discussion, dispute? Yes, it did. Yes, it still does. The people who met here, the people who meet in laboratories still, only end their work with a mathematical formulation. They begin it by trying to solve conceptual riddles. The riddles of the sub-atomic particles – of the electrons and the rest – are mental riddles.
Think of the puzzles that the electron was setting just at that time. The quip among professors was (because of the way university timetables are laid out) that on Mondays, Wednesdays, and Fridays the electron would behave like a particle; on Tuesdays, Thursdays, and Saturdays it would behave like a wave. How could you match those two aspects, brought from the large-scale world and pushed into a single entity, into this Lilliput, Gulliver’s Travels world of the inside of the atom? That is what the speculation and argument was about. And that requires, not calculation, but insight, imagination – if you like, metaphysics. I remember a phrase that Max Born used when he came to England many years after, and that still stands in his autobiography. He said: ‘I am now convinced that theoretical physics is actual philosophy’.
Max Born meant that the new ideas in physics amount to a different view of reality. The world is not a fixed, solid array of objects, out there, for it cannot be fully separated from our perception of it. It shifts under our gaze, it interacts with us, and the knowledge that it yields has to be interpreted by us. There is no way of exchanging information that does not demand an act of judgment. Is the electron a particle? It behaves like one in the Bohr atom. But de Broglie in 1924 made a beautiful wave model, in which the orbits are the places where an exact, whole number of waves closes round the nucleus. Max Born thought of a train of electrons as if each were riding on a crankshaft, so that collectively they constitute a series of Gaussian curves, a wave of probability. A new conception was being made, on the train to Berlin and the professorial walks in the woods of Göttingen: that whatever fundamental units the world is put together from, they are more delicate, more fugitive, more startling than we catch in the butterfly net of our senses.
All those woodland walks and conversations came to a brilliant climax in 1927. Early that year Werner Heisenberg gave a new characterisation of the electron. Yes, it is a particle, he said, but a particle which yields only limited information. That is, you can specify where it is at this instant, but then you cannot impose on it a specific speed and direction at the setting-off. Or conversely, if you insist that you are going to fire it at a certain speed in a certain direction, then you cannot specify exactly what its starting-point is – or, of course, its end-point.
That sounds like a very crude characterisation. It is not. Heisenberg gave it depth by making it precise. The information that the electron carries is limited in its totality. That is, for instance, its speed and its position fit together in such a way that they are confined by the tolerance of the quantum. This is the profound idea: one of the great scientific ideas, not only of the twentieth century, but in the history of science.
Heisenberg called this the Principle of Uncertainty. In one sense, it is a robust principle of the everyday. We know that we cannot ask the world to be exact. If an object (a familiar face, for example) had to be exactly the same before we recognised it, we would never recognise it from one day to the next. We recognise the object to be the same because it is much the same; it is never exactly like it was, it is tolerably like. In the act of recognition, a judgment is built in – an area of tolerance or uncertainty. So Heisenberg’s principle says that no events, not even atomic events, can be described with certainty, that is, with zero tolerance. What makes the principle profound is that Heisenberg specifies the tolerance that can be reached. The measuring rod is Max Planck’s quantum. In the world of the atom, the area of uncertainty is always mapped out by the quantum.
Yet the Principle of Uncertainty is a bad name. In science or outside it, we are not uncertain; our knowledge is merely confined within a certain tolerance. We should call it the Principle of Tolerance. And I propose that name in two senses. First, in the engineering sense. Science has progressed step by step, the most successful enterprise in the ascent of man, because it has understood that the exchange of information between man and nature, and man and man, can only take place with a certain tolerance. But second, I also use the word passionately about the real world. All knowledge, all information between human beings can only be exchanged within a play of tolerance. And that is true whether the exchange is in science, or in literature, or in religion, or in politics, or even in any form of thought that aspires to dogma. It is a major tragedy of my lifetime and yours that, here in Göttingen, scientists were refining to the most exquisite precision the Principle of Tolerance, and turning their backs on the fact that all around them tolerance was crashing to the ground beyond repair.
The sky was darkening all over Europe. But there was one particular cloud which had been hanging over Göttingen for a hundred years. Early in the 1800s Johann Friedrich Blumenbach had put together a collection of skulls that he got from distinguished gentlemen with whom he corresponded throughout Europe. There was no suggestion in Blumenbach’s work that the skulls were to support a racist division of humanity, although he did use anatomical measurements to classify the families of man. All the same, from the time of Blumenbach’s death in 1840 the collection was added to and added to and became a core of racist, pan-Germanic theory, which was officially sanctioned by the National Socialist Party when it came into power.
When Hitler arrived in 1933, the tradition of scholarship in Germany was destroyed, almost overnight. Now the train to Berlin was a symbol of flight. Europe was no longer hospitable to the imagination – and not just the scientific imagination. A whole conception of culture was in retreat: the conception that human knowledge is personal and responsible, an unending adventure at the edge of uncertainty. Silence fell, as after the trial of Galileo. The great men went out into a threatened world. Max Born. Erwin Schrödinger. Albert Einstein. Sigmund Freud. Thomas Mann. Bertolt Brecht. Arturo Toscanini. Bruno Walter. Marc Chagall. Enrico Fermi. Leo Szilard, arriving finally after many years at the Salk Institute in California.
The Principle of Uncertainty or, in my phrase, the Principle of Tolerance fixed once for all the realisation that all knowledge is limited. It is an irony of history that at the very time when this was being worked out there should rise, under Hitler in Germany and other tyrants elsewhere, a counter-conception: a principle of monstrous certainty. When the future looks back on the 1930s it will think of them as a crucial confrontation of culture as I have been expounding it, the ascent of man, against the throwback to the despots’ belief that they have absolute certainty.
I must put all these abstractions into concrete terms, and I want to do so in one personality. Leo Szilard was greatly engaged in them, and I spent many afternoons in the last year or so of his life talking with him about them at the Salk Institute.
Europe was no longer hospitable to the imagination.
Enrico Fermi.
Leo Szilard was a Hungarian whose university life was spent in Germany. In 1929 he had published an important and pioneer paper on what would now be called Information Theory, the relation between knowledge, nature and man. But by then Szilard was certain that Hitler would come to power, and that war was inevitable. He kept two bags packed in his room, and by 1933 he had locked them and taken them to England.
It happened that in September of 1933 Lord Rutherford, at the British Association meeting, made some remark about atomic energy never becoming real. Leo Szilard was the kind of scientist, perhaps just the kind of good-humoured, cranky man, who disliked any statement that contained the word ‘never’, particularly when made by a distinguished colleague. So he set his mind to think about the problem. He tells the story as all of us who knew him would picture it. He was living at the Strand Palace Hotel – he loved living in hotels. He was walking to work at Bart’s Hospital, and as he came to Southampton Row he was stopped by a red light. (That is the only part of the story I find improbable; I never knew Szilard to stop for a red light.) However, before the light turned green, he had realised that if you hit an atom with one neutron, and it happens to break up and release two, then you would have a chain reaction. He wrote a specification for a patent which contains the words ‘chain reaction’ which was filed in 1934.
And now we come to a part of Szilard’s personality which was characteristic of scientists at that time, but which he expressed most clearly and loudly. He wanted to keep the patent secret. He wanted to prevent science from being misused. And, in fact, he assigned the patent to the British Admiralty, so that it was not published until after the war.
But meanwhile war was becoming more and more threatening. The march of progress in nuclear physics and the march of Hitler went step by step, pace by pace, in a way that we forget now. Early in 1939 Szilard wrote to Joliot Curie asking him if one could make a prohibition on publication. He tried to get Fermi not to publish. But finally, in August of 1939, he wrote a letter which Einstein signed and sent to President Roosevelt, saying (roughly), ‘Nuclear energy is here. War is inevitable. It is for the President to decide what scientists should do about it’.
Finally, Szilard wrote a letter which Einstein signed and sent to President Roosevelt.
Text of the letter of 2 August 1939 to the President of the United States.
But Szilard did not stop. When in 1945 the European war had been won, and he realised that the bomb was now about to be made and used on the Japanese, Szilard marshalled protest everywhere he could. He wrote memorandum after memorandum. One memorandum to President Roosevelt only failed because Roosevelt died during the very days that Szilard was transmitting it to him. Always Szilard wanted the bomb to be tested openly before the Japanese and an international audience, so that the Japanese should know its power and should surrender before people died.
As you know, Szilard failed, and with him the community of scientists failed. He did what a man of integrity could do. He gave up physics and turned to biology – that is how he came to the Salk Institute – and persuaded others too. Physics had been the passion of the last fifty years, and their masterpiece. But now we knew that it was high time to bring to the understanding of life, particularly human life, the same singleness of mind that we had given to understanding the physical world.
The first atomic bomb was dropped on Hiroshima in Japan on 6 August 1945 at 8.15 in the morning. I had not been long back from Hiroshima when I heard someone say, in Szilard’s presence, that it was the tragedy of scientists that their discoveries were used for destruction. Szilard replied, as he more than anyone else had the right to reply, that it was not the tragedy of scientists: ‘it is the tragedy of mankind’.
There are two parts to the human dilemma. One is the belief that the end justifies the means. That push-button philosophy, that deliberate deafness to suffering, has become the monster in the war machine. The other is the betrayal of the human spirit: the assertion of dogma that closes the mind, and turns a nation, a civilisation, into a regiment of ghosts – obedient ghosts, or tortured ghosts.
It is said that science will dehumanise people and turn them into numbers. That is false, tragically false. Look for yourself. This is the concentration camp and crematorium at Auschwitz. This is where people were turned into numbers. Into this pond were flushed the ashes of some four million people. And that was not done by gas. It was done by arrogance. It was done by dogma. It was done by ignorance. When people believe that they have absolute knowledge, with no test in reality, this is how they behave. This is what men do when they aspire to the knowledge of gods.
Science is a very human form of knowledge. We are always at the brink of the known, we always feel forward for what is to be hoped. Every judgment in science stands on the edge of error, and is personal. Science is a tribute to what we can know although we are fallible. In the end the words were said by Oliver Cromwell: ‘I beseech you, in the bowels of Christ, think it possible you may be mistaken’.
I owe it as a scientist to my friend Leo Szilard, I owe it as a human being to the many members of my family who died at Auschwitz, to stand here by the pond as a survivor and a witness. We have to cure ourselves of the itch for absolute knowledge and power. We have to close the distance between the push-button order and the human act. We have to touch people.
CHAPTER TWELVE
GENERATION UPON GENERATION
In the nineteenth century the city of Vienna was the capital of an Empire which held together a multitude of nations and languages. It was a famous centre of music, literature and the arts. Science was suspect in conservative Vienna, particularly biological science. But unexpectedly Austria was also the seedbed for one scientific idea (and in biology) that was revolutionary.
At the old university of Vienna the founder of genetics, and therefore of all the modern life sciences, Gregor Mendel, got such little university education as he had. He came at a historic time in the struggle between tyranny and freedom of thought. In 1848, shortly before he came, two young men had published far away in London, in German, a manifesto which begins with the phrase: ‘Ein Gespenst geht um Europa’, ‘a spectre is haunting Europe’, the spectre of communism.
Of course, Karl Marx and Friedrich Engels in The Communist Manifesto did not create the revolutions in Europe; but they gave them the voice. It was the voice of insurrection. A spate of disaffection ran though Europe against the Bourbons, the Habsburgs, and governments everywhere. Paris was in turmoil in February of 1848, and Vienna and Berlin followed. And so in the University Square in Vienna in March 1848 students protested and fought the police. The Austrian Empire, like others, shook. Metternich resigned and fled to London. The Emperor abdicated.
Emperors go, but empires remain. The new Emperor of Austria was a young man of eighteen, Franz Josef, who reigned like a medieval autocrat until the ramshackle empire fell to pieces during the First World War. I still remember Franz Josef when I was a small boy; like other Habsburgs, he had the long lower lip and pouched mouth which Velazquez has painted in the Spanish kings, and which is now recognised as a dominant genetic trait.
When Franz Josef came to the throne the patriots’ speeches fell silent; the reaction under the young Emperor was total. At that moment the ascent of man was quietly set off in a new direction by the arrival at the University of Vienna of Gregor Mendel. He had been born Johann Mendel, a farmer’s son; Gregor was the name he was given when he became a monk just before this, frustrated by poverty and lack of education. He remained all his life a farm boy in the way he went about his work, not a professor nor a gentleman naturalist like his contemporaries in England; he was a kitchen-garden naturalist.
Mendel had become a monk to get an education, and his abbot put him into the University of Vienna to get a formal diploma as a teacher. But he was nervous and was not a clever student. His examiner wrote that he ‘lacks insight and the requisite clarity of knowledge’ and failed him. The farm boy become monk had no choi
ce except to withdraw again into the anonymity of the monastery at Brno in Moravia, which is now part of Czechoslovakia.
The ascent of man was quietly set off in a new direction by Gregor Mendel.
Mendel in 1865.
When Mendel came back from Vienna in 1853 he was, at the age of thirty-one, a failure. He had been sent by the Augustinian Order of St Thomas in Brno, and they were a teaching order. The Austrian Government wanted the bright boys among the peasantry taught by monks. Theirs is the library not so much of a monastery as of a teaching order. And Mendel had failed to qualify as a teacher. He had to make up his mind whether to live the rest of his life as a failed teacher, or as – what? As the boy they called Hansl on the farm, the young man Johann from the farm, he decided; not as the monk Gregor. He went back in thought to what he had learned on the farm and had been fascinated by ever since: plants.
At Vienna he had been under the influence of the one fine biologist he ever met, Franz Unger, who took a concrete, practical view of inheritance: no spiritual essences, no vital forces, stick to the real facts. And Mendel decided to devote his life to practical experiments in biology, here in the monastery. A bold, silent, and secret stroke, I think, because the local bishop would not even allow the monks to teach biology.
Mendel began his formal experiments about two or three years after he came back from Vienna, say about 1856. He says in his paper that he worked for eight years. The plant that he had chosen, very carefully, is the garden pea. He picked out seven characters for comparison: shape of seed, colour of seed, and so on, finishing his list with tall in stem versus short-stemmed. And that last character is the one that I have chosen to display: tall versus short.
The Ascent of Man Page 24