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Max Planck, center, with Walther Nernst, Albert Einstein, Robert Andrews Millikan, and Max Laue, all physicists and winners of the Nobel Prize, Berlin, 1928

In the summer of 1946, as soon as possible after the end of World War II, the Royal Society of London organized a celebration for the three hundredth birthday of Isaac Newton. Newton was born on Christmas Day 1642, laid the foundations of modern physics with his masterpiece, Mathematical Principles of Natural Philosophy, in 1686, and served as president of the Royal Society from 1703 until his death in 1727. The birthday party had been postponed because of the war. Surviving in the ruins of defeated Germany were many distinguished scientists, all of them loyal to their country and many of them tainted by active collaboration with the Nazi regime. The Royal Society invited only one man to represent Germany at the celebration. The chosen representative, serving as a symbol of the glorious past and the tragic downfall of German science, was Max Planck.

Planck was then eighty-eight years old, devoting the last years of his life to the rebuilding of German science. When he entered the auditorium at the Newton celebration, the leaders of British science gave him long and emotional applause. He had laid the foundations of quantum theory with his masterpiece, the paper “On the Theory of the Energy Distribution Law of the Normal Spectrum,” in 1900, and had served as president of the Prussian Academy of Sciences, the German equivalent of the Royal Society.

In that paper he had explained the observed intensity of light of various colors emitted from the surfaces of hot objects at various temperatures. His explanation involved a new and revolutionary idea: that energy could move around only in little packets rather than continuously. The little packets were later called quanta, and Planck’s idea was called quantum theory. Planck’s quantum theory and Einstein’s theory of relativity became the twin foundation stones on which the science of the twentieth century was built.

Besides inventing quantum theory, Planck had made another great contribution to science by welcoming and generously supporting the young Albert Einstein. In 1905, when Einstein, then an unknown employee of the Swiss patent office in Bern, sent five revolutionary papers to the physics journal that Planck edited in Berlin, Planck immediately recognized them as works of genius and published them quickly without sending them to referees. He did not agree with all of Einstein’s ideas, but he published all of them. He helped Einstein to move ahead in the academic world, and in 1913 invited him to a full professorship in Berlin. For twenty years Planck and Einstein were friends and colleagues in Berlin, leaders of a scientific community that remained creative and vibrant, in spite of the political and economic disarray that surrounded them. Planck was the rock-solid central figure of German science, with the vision to promote the unorthodox and unpatriotic citizen-of-the-world Einstein.

For Planck, loyalty to Germany always came first. The British audience at the Royal Society gave him the respect due to a defeated enemy who had fought bravely. The audience also knew that his son Erwin had been hanged by Hitler’s executioners in the final days of the war in 1945. Erwin had opposed Hitler and paid for it with his life. That greatly increased the respect paid to his father. It made the old Planck a suitable symbol for a reborn Germany. It gave him a final chance to do some service to his country. At the end of his life he saw German science beginning to revive in Göttingen as a result of his friendly relations with the British occupation authorities.

Once in his life, Planck had traveled to the United States. In 1909 he was invited by Columbia University to give a series of eight public lectures on recent developments in physics. He was then the most famous theoretical physicist in the world. He gave his lectures in German. In those days anyone with a serious interest in physics would understand German. A large fraction of the scientific literature was in German, and a large fraction of the American experts had studied in Germany. Michael Pupin, the professor whose name now belongs to the Columbia University physics building, probably had a hand in inviting Planck to Columbia. Pupin had been a student of the great physicist Hermann von Helmholtz in Berlin. Planck and von Helmholtz were close friends.

Planck spoke at Columbia about the broad understanding of atomic and thermodynamic processes that had been achieved in the nineteenth century, ending with the new questions raised by his own quantum theory and Einstein’s relativity at the beginning of the twentieth. The audience for Planck’s lectures did not dwindle, and he came home to Berlin with happy memories of American hospitality. But he had not expected to learn any new science in America. Josiah Willard Gibbs, the only American scientist that Planck might have recognized as his intellectual equal, had died in 1903. It was evident in 1909 that Germany was far ahead of America, in dedication to pure research and in depth of understanding of science.


The two decisive dates in the German tragedy were 1914 and 1933. The origins of World War I were complicated and are still debated by historians, but there is no doubt that the war could have been avoided if the German leadership in 1914 had been wiser. The German leaders, including the kaiser, the military, the scholars, and the scientists, were immersed in a militaristic culture that glorified the fatherland and welcomed the war. They regarded the initial quarrel between Serbia and Austria as a golden opportunity for Germany to give a good beating to its enemies Russia and France.

On October 4, 1914, soon after the war began, the scholars and scientists of Germany demonstrated their patriotic spirit by publishing an “Appeal to the Cultured People of the World,” signed by ninety-three leading intellectuals. The appeal of the intellectuals declared the solidarity of German culture with the German army, specifically approving the invasion of neutral Belgium and the killing of Belgian civilians who resisted the invasion. Leading writers, artists, theologians, and scientists had been invited to sign the appeal. Among those who signed was Planck. Among those who refused was Einstein.

Einstein saw clearly in 1914 that the German obsession with national glory was insane. Planck still believed in national glory. The two remained friends. Planck played the piano and Einstein played the violin, and they loved to play together. After 1914, Planck became more deeply attached to Germany, while Einstein became more detached. Planck felt closer to his German heritage as he saw his people defeated and impoverished. Einstein felt closer to the worldwide community of Jews as he saw them attacked and endangered.

From 1914 until 1933, with help from Planck and Einstein, German science flourished while German society broke apart. Then in January 1933 everything changed. Hitler seized power and the second German tragedy began. Hitler considered himself the good soldier who almost won World War I, and the soldiers with whom he served to be undefeated. Only the politicians were defeated, mostly because they were corrupted by treacherous Jews. Hitler’s dream was to fight World War I over again and this time win. Incidentally, he would get rid of the Jews and the Communists. And incidentally, he would provide jobs for the unemployed and prosperity for German industry. This dream resonated strongly with the German public after twenty years of feeble government and economic misery. Hitler won power in 1933 with solid public support, helped by a well-organized campaign of violence and intimidation.

In 1933 Planck and Einstein ended their friendship. Einstein had seen the disaster coming and made his preparations in good time. He moved to America and never again set foot in Germany. Planck stayed in Berlin and remained loyal to the fatherland, although he knew that his loyalty demanded obedience to the murderous whims of a man he despised. Einstein sent a formal notice to the Prussian Academy resigning his membership. Planck as president of the academy recorded the resignation, with a comment that Einstein had only himself to blame for it. At the same time, Planck dismissed a number of other academy members who happened to be Jewish. He was required by the new racial laws to dismiss Jews, and he did as he was told. Planck was never a member of the Nazi Party, but he never defied its cruel and crazy laws.

Only once, in May 1933, did Planck meet with Hitler face to face, to try to mitigate the damage that Hitler was doing to German science. He appealed to Hitler to keep Fritz Haber in Germany. Haber was a world-famous chemist who won a Nobel Prize for inventing the industrial process for converting nitrogen from the atmosphere into fertilizer. He was also a Jew and an intensely patriotic German. He had done important military service for the fatherland in World War I, developing the chemical weapons that German troops used effectively on the Western Front.

To keep Haber in Germany, it would be necessary for Hitler to allow him to keep several Jewish colleagues who worked for him. Hitler reacted to this suggestion with furious anger, giving Planck a firsthand view of the black hatred that gave driving force to Hitler’s ambition. Planck quietly left the room. He saw that any attempt to negotiate with Hitler was futile. He continued to serve as president of the academy, helping Hitler to destroy German science by enforcing the racial laws.

Planck had one Jewish colleague whom he could protect. That was Lise Meitner, who became world-famous in 1939 when she understood the process of splitting the uranium atom discovered by her friend Otto Hahn in Berlin. She gave the name “fission” to Hahn’s discovery. She was then living as a refugee in Sweden, having escaped from Germany in 1938. Until 1938, with the help of Planck, she was able to survive and work with Hahn in Berlin because she was an Austrian citizen.


In 1938 Hitler annexed Austria. Meitner thus became a German citizen subject to the racial laws, and Planck could no longer protect her. She had come to Berlin in 1907 as a student, had attended Planck’s lectures, and had quickly become his friend. In 1912 he gave her a job as his assistant, and afterward helped her at every stage of her career until she became the first female science professor at the University of Berlin. For thirty years she was almost a member of the Planck family, sharing their joys and sorrows. There were plenty of sorrows, as Planck lost two daughters in childbirth and a son fighting at Verdun in World War I. There were plenty of joys, as Meitner shared Planck’s love of science, his love of music, and his love of hiking in mountains.

After their enforced separation in 1938, Planck and Meitner met twice more. In 1943, with Hitler’s war grinding toward its agonizing end, Planck was able to travel to Stockholm and spend a day with his old friend. Meitner described their meeting in her memoirs. She never lost her respect and admiration for Planck. She saw him as a tragic figure, doing the best he could in a hopeless situation. In the meantime she had traveled to America and met with many of the leading nuclear physicists there, all of them heavily involved in the Manhattan Project. She met with General Leslie Groves, the leader of the project. She had no clearance to learn secret information, but she could see pretty well what was going on. From remarks that Planck made later, it is likely that Meitner shared with him some of her insights. After that, they met once more. Meitner was in London to greet him when he came to the Newton celebration in 1946. She describes this final meeting as “like a gift from heaven…the purity and integrity of his character have resisted all the years.”


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Max Planck, 1930

Brandon Brown’s biography of Planck is arranged in a peculiar way. Each chapter begins with a brief episode from the apocalyptic final years of his life, beginning in 1943 and ending with his death in 1947. Each of these episodes is followed by a longer narrative presented as a flashback memory, describing the happier years of his youth and the triumphs of his maturity. This arrangement has the effect of emphasizing the tragedy and diminishing the achievements of his life. A more conventional arrangement would have shown him as a man who was in many ways lucky, living in a time and place where his extraordinary gifts were put to good use, giving the world new insights into the mysteries of nature. His lasting memorial is the Max Planck Institute, a great institution for the support of scientific research in Germany, carrying forward the public service to which he devoted his life.

I now turn from the details of Planck’s biography to the general issues of ethics and politics that his story raises. My Princeton colleague Albert Hirschman published in 1970 a little book with the title Exit, Voice, and Loyalty, exploring these issues in a different perspective. Hirschman was writing as an economist about large-scale enterprises that he had seen in many countries, beginning with the railroads in Nigeria and ending with the American war in Vietnam. In each of these enterprises, gross failures were manifest, and the individuals occupying positions of responsibility had to choose between three alternative responses. Exit meant to quit the enterprise. Voice meant to stay on the job but speak out publicly for change of direction. Loyalty meant to stay on the job and give support to the continuation of failing policies. Hirschman observed that in the majority of enterprises, voice is sadly lacking. Most people choose loyalty and very few choose voice. Those who choose exit have only a small effect on the enterprise. If gross errors and injustices are to be corrected, voice must be fearless and fierce, loud enough to be heard.

Hirschman’s picture of three choices can be applied to German society as a whole, considered as a single enterprise, during the lifetime of Planck (who was born in 1858) up to 1933. The society moved ahead rapidly in art and music and literature as well as in science. It was marred by a concentration of power in the hands of wealthy aristocrats and professional soldiers. It came to grief in 1914 because it was deluded by dreams of military glory. Until 1933, Hirschman’s three responses to the failures were available. Planck chose loyalty. Einstein chose exit when he first left Germany in 1895, and chose voice when he returned in 1914.

After 1933, Hirschman’s picture no longer applied, because open opposition to Hitler meant suicide. Voice was no longer available. It was replaced by secret resistance. In any national community with a totalitarian government, the choices are exit, resistance, and loyalty. After 1933, Planck continued to choose loyalty, Einstein chose exit, and Planck’s son Erwin chose resistance. Exit was clearly the right choice for Einstein and would have been the right choice for Erwin. For Max Planck himself, the right choice is not so clear. The story of Max is a particular example of a more general question: where to draw the line between loyalty to a community and resistance to evil. He had to choose between loyalty to Germany and resistance to Hitler. He chose loyalty. His choice and Erwin’s choice both ended badly. There is no easy solution to the dilemma when a beloved community falls into the hands of warmongers, or when it welcomes a tyrant like Hitler as a leader.

Another highly gifted man facing the same dilemma was Robert E. Lee, who had to choose between loyalty to the state of Virginia and resisting the will of his people to fight a disastrous war. Lee came through the ordeal like Planck, honored and respected by friends and enemies. Lee was fighting for the perpetuation of slavery. Planck was obeying a leader who murdered millions in concentration camps. Our traditional warrior ethic tells us to honor people who are loyal and fight bravely for their own communities, even when the cause for which they fight is evil. Do Lee and Planck deserve the admiration that we give them? Hirschman’s book does not provide an answer to that question.

The most important example of Hirschman’s dilemma is the nuclear weapons enterprise, beginning with the discovery of fission in 1938 and continuing to the present day. This is a monstrous growth to which many talented people have devoted their lives, bringing enormous costs and dangers and achieving a precarious balance of terror. The dangers were clearly foreseen by the people who started the enterprise in 1939. In 1939 they had a brief opportunity, before their national governments knew what was happening and before the barriers of secrecy were established, to respond to the dangers with a loud and public voice. If they had chosen voice in 1939, the scientists of the United States and Britain and Germany and the Soviet Union might have come to an effective agreement not to go ahead with building nuclear bombs. The opportunity was missed. Instead, the scientists chose loyalty, and were quickly trapped in an escalating arms race with no end in sight.

During the years from 1940 to 1945, secrecy prevailed everywhere and voice was not an option. During those years, Max Planck was in close contact with his friend Werner Heisenberg, who was leading the abortive German nuclear energy project. Heisenberg probably kept Planck informed about the project and invited him to participate in it. If he was invited, Planck had the wisdom to say no. So far as nuclear bombs were concerned, Planck chose exit.

It is likely that something similar happened when Meitner met with General Groves in America. Meitner was a legendary figure, one of the discoverers of fission, driven from her home in Berlin by Hitler. It is hard to imagine that she would have been attending a nuclear conference in America if she had not been quietly invited to join the Manhattan Project. Like Planck, she chose exit and kept silent. A third European scientist of legendary status was Niels Bohr, who escaped from his home in Denmark to Sweden when the German occupation authorities in Denmark began deporting Jews. We know that Bohr was invited to join the Manhattan Project, because he accepted. He chose loyalty and was bound by the rules of secrecy that loyalty imposes.

Bohr understood that the only way to avoid an apocalyptic nuclear arms race was to establish an international authority with power to control industrial and military nuclear activities in all countries. He understood that the chance of achieving this goal would be much greater if serious discussions of nuclear issues with the Soviet Union could be started before the American bomb was built and used. He made it his mission to speak personally with President Roosevelt and Prime Minister Churchill to urge them to move immediately in this direction; and actually succeeded in meeting privately with them.

Roosevelt received him graciously and listened politely but took no action. The meeting of Bohr with Churchill was a disaster. It was oddly like an echo of the meeting of Planck with Hitler eleven years earlier. Churchill became furiously angry. He told Bohr that the sharing of nuclear information with the Russians was a mortal crime. Bohr never had a chance to explain why secrecy could give Britain no lasting security. Churchill subsequently remarked that Bohr ought to be locked up before he gave away any more secrets. Churchill and Hitler were in several ways similar. Both of them loved war. Both of them had dreams of empire. Both of them were bad listeners and quick to anger. Fortunately, their differences were greater than their similarities.

After 1945, the basic facts about nuclear weapons were no longer secret and voice became possible. Great scientists, beginning with Bohr and Einstein, gave powerful voice to the hope of escape from nuclear madness. Their voices did not prevail. Loyalty to our tribes prevailed. After seventy years we are left with deeply entrenched institutions and deeply entrenched beliefs, making nuclear weapons a permanent part of our way of life. To escape from this trap, some future generation must challenge our institutions and beliefs with a louder voice, blowing their trumpets and shouting with a great shout until the walls of nuclear loyalty fall down like the walls of Jericho long ago.

If we are lucky, the demolition of nuclear weaponry will be achieved peacefully, as Einstein hoped, as a consequence of a change in our way of thinking. If we are unlucky, the demolition will be achieved as a consequence of a nuclear holocaust, and our descendants will find themselves, like Max Planck at the end of his life, starting to build a new world amid the rubble of the old. This time, the rubble will be radioactive.