Shortly after Erwin’s execution, Allied bombing put a permanent end to the People’s Court. Hitting it mid-session, the airstrike destroyed the courthouse, and an enormous beam cascaded through the shelter beneath, killing Judge Roland Freisler. He died with prisoner files still in his grip.1 The Plancks received little consolation from this news. Nor were they cheered by the waves of written condolences, sharing their own fresh tragedies: destroyed apartments, missing relatives, dead soldiers, and the deprivations of a nation in collapse.
Planck spent time at the guesthouse piano playing Erwin’s favorite songs. In writing to his nephew, he mistakenly wrote Erwin as his signature. “I fight every day anew to gain the strength to accept this twist of fate,” he wrote. “Because with every new morning, it overcomes me like a new blow, paralyzing me and clouding my clear mind, and it will take a long time until I’ll be back in mental balance.”2
In early April, American troops swept eastward toward the Elbe River, while Soviet armies took Vienna and moved rapidly on Berlin. Marga was terrified at the increasing military presence around them. An officer told the Plancks that the area was ideal for an enemy’s aerial troop landing. And the medieval tower adjacent to the guesthouse would make a good perch for German artillery, anchoring their defenses. As German soldiers swarmed into Rogätz, Marga wrote a hurried letter to a relative in Göttingen, asking if she and Max could stay there in an emergency.3
As the Americans approached, General Dwight D. Eisenhower called for German surrender, but Hitler ignored it. “Never will we repeat the mistake of 1918,” he had declared in 1943, “laying down our arms at a quarter to midnight.”4
Meanwhile, the world began to witness the scope of Nazi atrocities as the British liberated the Bergen-Belsen concentration camp, piled with unburied bodies, and the Americans found Buchenwald. On April 12 (the day American president Franklin Roosevelt died), journalist Edward R. Murrow entered Buchenwald, and his CBS broadcast became a particular touchstone of the Holocaust.5 He began by warning listeners that his report “would not be pleasant listening.” After talking with several prisoners at the gate, he approached one of barracks. “When I entered, men crowded around, tried to lift me to their shoulders. They were too weak. Many of them could not get out of bed. I was told that this building had once stabled 80 horses. There were 1,200 men in it, five to a bunk.” Driven outside by a stench “beyond all description,” he then watched men in their final moments, slumping and expiring before him as others crawled toward the latrines. General Eisenhower began shuttling large tours of German citizens through the camps, where many broke down in tears or fainted.6
Max and Marga wouldn’t have heard the news. Rogätz became a war zone by April 9, and the Plancks fled their once quiet refuge amid approaching gunfire and shelling. They crossed the Elbe River and headed east. On April 13, American troops claimed Rogätz, but intense fighting continued in the area. Now the Plancks tried to locate primitive shelter, barns and sheds, while navigating what Marga later described to Lise Meitner as a “combat zone” filled with the “last but not the least horrors of the war.”7 Only mortal danger could compel them to move, as Planck’s curled and rigid back rendered him nearly immobile. “The very worst was the frightful suffering that Uncle Max had to bear,” Marga later wrote. “He often screamed from the pain.”8
There was no returning to Rogätz, even if they’d wanted to surrender to the Americans. German troops continued to launch counter attacks, seeking to retake the town.9
As Planck fled the battle, did he glimpse an American face bobbing beneath a green helmet? Would he recall his former encounters and fond impressions? The happiest time of his life’s long arc included his only trip to America. In early 1909, all the dear women in his life were still with him: his mother, his first wife Marie, his friend and colleague Lise Meitner, and his musical twins Grete and Emma.
His lectures now attracted 10 times the students that his first Berlin lectures had 20 years earlier. He was only a few months from finally meeting his pen pal, Albert Einstein, at a Salzburg conference. In 1909, Planck foresaw the two of them leading the way in building a single theoretical structure to unite all of physics.
Columbia University invited Planck to lecture on the state of theoretical physics. He looked forward to taking such a trip with Marie, but her health steadily worsened as the trip approached. She started with a cough that winter, and “gradually a fever came to her,” he wrote in the letter diary, and “she is confined to bed, with a left-side pneumonia.” He took her to a sanatorium in Ebersteinburg, “where she now hopefully finally goes to find healing with careful and expert care. The major regret is that she cannot accompany me on a journey … to New York.” Instead of traveling alone, he elected to take one of his daughters in Marie’s place, choosing the “older” Emma, and presenting Grete with a harmonium as a consolation prize.10
As far as we know, this marked Planck’s only overseas trip, and if he recalled the stories from his mentor Hermann von Helmholtz, he followed those footsteps with a mix of excitement and trepidation. Helmholtz and his wife had traveled to see the Chicago World’s Fair of 1893 and, in particular, to attend the International Electrical Congress (along with Thomas Edison and others). At the time, Helmholtz was nearly without peer as an international scientific figure, and America greeted him with much fanfare.11 He met with President Grover Cleveland, and American elites queued for a handshake as the famous scientist toured major cities. But on the return ocean voyage, he’d tumbled down a flight of stairs, striking his head. Everything healed externally, but the 71-year-old never regained his former energy and concentration. One year later, back in Berlin with Planck, a cerebral hemorrhage sent him to his deathbed. So while Planck may have associated the trip to America with the great Helmholtz’s demise, he must also have recalled the man’s enthusiasm. “I am convinced that America represents the future of civilized humanity,” Helmholtz wrote to a friend in 1893, “while in Europe we have only chaos or the supremacy of Russia to look forward to.”12
Max and Emma first stopped in Washington, DC, and he wrote Max von Laue a postcard featuring the White House (bereft of trees save a few scrawny palms), mentioning that New York was next.13 Planck relayed to his friend Willie Wien that he’d found “vigor and hospitality” in America and that he cherished Emma’s company, as they shared impressions and navigated busy itineraries.14
The New York of 1909 boasted twice Berlin’s population and would have surprised any German tourist with its young skyscrapers. Several buildings already rose more than 20 stories and the new Singer Tower was the world’s tallest, rising over 600 feet, with 47 floors. One assumes Max and Emma would make the short walk from Columbia to the city’s Central Park, but they might have found less relief there than in their native Grunewald paths. Automobiles were now allowed to jostle with horse-drawn and goat-drawn carriages throughout the park.15
When Max began his eight Columbia lectures, he did so as the most renowned and respected theoretical physicist in the world. As one generation faded, he transitioned to the old guard. His mentor Helmholtz had passed 15 years earlier, Boltzmann had recently taken his own life, and Einstein, despite his miracle year of 1905, didn’t yet enjoy Planck’s international reputation. In 1909, relativity still seemed radical, and very few took Einstein’s “light quanta” idea seriously. To an American audience, Planck was the most brilliant physicist from the most prestigious scientific nation, and they eagerly awaited his lectures, which he naturally delivered in German, the language of physics.16
He thanked the president of Columbia and began with a humble caveat, saying he couldn’t possibly discuss all of theoretical physics. Instead, he would hit the primary topics of his greatest interest and involvement. From the outset, he warned against either underestimating the success of the topic, pointing to recent technologies like “wireless telegraphy” and “aerial navigation,” or overestimating its prospects. For instance, he dismissed recent claims that physics would soon describe both the inner workings of atoms and also “the laws of mental life.”17
He built quickly to one of the best encapsulations of his ultimate vision.
In short, we may say that the characteristic feature of the entire previous development of theoretical physics is a definite elimination from all physical ideas of the anthropomorphic elements. … Now, what are the great advantages to be gained through such a real obliteration of personality? … The result is nothing more than the attainment of unity and compactness in our system of theoretical physics, and, in fact, the unity of the system, not only in relation to all of its details, but also in relation to physicists of all places, all times, all peoples, and all cultures.
This is the early talk of the “unified field theory” that later haunted Einstein’s work and compels theorists to this day. But Planck wasn’t done with the topic of transcendence.
Certainly the system of theoretical physics should be adequate, not only for the inhabitants of this earth, but also for the inhabitants of other heavenly bodies. Whether the inhabitants of Mars, in case such actually exist, have eyes and ears like our own, we do not know—it is quite improbable, but that they, in so far as they possess the necessary intelligence, recognize the law of gravitation and the principle of energy, most physicists would hold as self evident.18
Our red neighbor was a hot topic in 1909, especially in the United States. The polymath Percival Lowell had turned his thick bankroll to studying astronomy at about the same time Planck turned to black-body radiation. Lowell built his observatory just outside Flagstaff, Arizona. (The installation functions to this day and offers a fascinating tour.) After many years of work, he published Mars and Its Canals in 1906, followed by Mars as the Abode of Life in 1908. Lowell reheated and popularized the notion that the visible striations on Mars were actually the canals of an intelligent civilization. But the public welcomed these books much more than did the scientific community. Soon enough, other more reputable astronomers, using a more powerful telescope, said the “canals” were probably signs of natural erosion on the barren Martian surface. So although Planck played to his audience a bit with the Mars reference, he probably gave his fellow physicists a knowing wink as well. Not catching the wink was his philosophical nemesis Ernst Mach, who ridiculed Planck that year for referencing the science of aliens.19
In the meat of his first Columbia lecture, Planck staked his central pillar of physical thought: entropy. By differentiating the majority of all physical interactions, in which entropy would increase, from the very rare cases, in which entropy might remain constant, he pointed to the absolute but still confounding arrow of time. “I express it as my opinion that in the theoretical physics of the future the first and most important differentiations of all physical processes will be into reversible and irreversible processes.”20
He delivered one lecture per day, and after the first week, Planck had come to his own dear baby: the theory of “heat radiation,” explaining the black-body experiments. The thoughtful progression of Planck’s lectures showed a master architect’s eye at its best. Moving from the existence of atoms to Boltzmann’s statistical treatment of atoms and the great conceptual power of entropy, he set up the black-body problem as a natural or even necessary destination.21 Using some of Boltzmann’s tools, as in his 1900 work, Planck derived his famous formula, but even in 1909, he concluded by shaking his head. He confessed that, “the physical meaning of the universal constant h remains quite unexplained.” And although he admitted that all existing classical theories “suffer from an incompleteness which demands a modification,” he was not yet ready to embrace the “radical” ideas of Einstein and others, in which light itself flew about in particle-like quanta. He modestly suggested, “It is not necessary to proceed in so revolutionary a manner” and proposed that the quantum of energy existed only between nearby components of the black body, with no direct relevance to light itself.22 So nine years after his discovery, the public Planck still sought to chain it to the fence separating matter from light, unwilling to let the quantum roam off leash in either region.
In his eighth and final Columbia lecture, Planck turned to the theory of relativity as the cutting edge of physics. Instead of diving right into Einstein’s principles, he set out the historical narrative moving through James Maxwell, Heinrich Hertz, and Hendrik Lorentz before placing Albert Einstein as the next logical way-shower, followed closely by Einstein’s former mathematics professor Minkowski. Halfway through this lecture, he made a crucial pivot that presages the political dawn of “German” versus “Jewish” physics in the devastating decades to come. Einstein’s ideas abolished the idea of absolutely simultaneous events or a universal time for all observers, and Planck admitted this would spawn headaches. Since the human mind was poisoned with preconceptions of time and therefore prone to, “logical mistakes … we shall adopt the mathematical method of treatment.”23 From there, his lecture was heavily and beautifully mathematical. We can see where the mathematical bus of Planck and Einstein was leaving the Johannes Starks of the physics world coughing in exhaust fumes.
He concluded this final lecture with an example that could strike one now as esoteric. He considered a black body moving at very high speed through a laboratory. By combining his own work with Einstein’s special relativity, he computed the speeding body’s thermal radiation spectrum. Especially in 1909, this was not a realistic or useful case, so what was he doing? By intentionally entwining their two greatest creations, he wanted to demonstrate that physics was moving toward a unified picture. But only a few months later, at a Salzburg conference, Planck heard Einstein bluntly declare that Planck’s own work meant there was no turning back—classical ideas of light were as good as dead. Though they would come together in Berlin as friends and music partners, their two signature theories eventually went the way of their personal dialogue, separate and irreconcilable.
“Colleagues, ladies and gentlemen, I have arrived at the conclusion of my lectures. I have endeavored to bring before you in bold outline those characteristic advances in the present system of physics which in my opinion are the most important. Another in my place would perhaps have made another and better choice.” He promised ongoing work, to leave “lasting results” for the next generations of physicists. “For if, while engaged in body and mind in patient and often modest individual endeavor, one thought strengthens and supports us it is this—that we in physics work not for the day only and for immediate results, but, so to speak, for eternity.” He then thanked them for their patience.24
Steaming eastward across the Atlantic, the professor and his daughter must have traded impressions of America. In addition to New York and Washington, they had visited “Baltimore, Boston-Cambridge, Ithaca, Niagara Falls. … Everywhere the people were lovely and amiable.”25 Max Planck’s recollections were indelibly upbeat, even reverential. A few years later, in his first address as rector of the University of Berlin, he cited America’s energy and optimism as worthy models for Germany.26 But when Max and Emma returned to the Planck villa in Grunewald, they found Marie worse than ever, with a fever that never abated. She died of her lung ailments within months, and Max buried her next to her parents in the mountains near Tegernsee. As more Planck funerals quietly queued for the coming decade, and as younger physicists prepared to close the chapter of his intellectual leadership, he left the peak of his long and gracious life in the wake of the passenger liner returning him to Germany.
In 1945, the Americans had come to his Fatherland. They battled retreating Germans through the streets of Rogätz, destroying the town’s normal tranquility. They advanced to the western edge of Elbe River, while the German forces regrouped on the opposite bank. The Americans could have crossed the Elbe and moved on Berlin, but General Eisenhower calculated military versus political aims. The Allies had already agreed to a framework partitioning in which the Soviet Union would take the German regions surrounding Berlin. The General saw no use in sacrificing further American lives for the political feat of being first to Berlin, if they then must return to the Elbe anyway. Furthermore, his orders had been to dismantle the German military and then divert resources to the Pacific theater. British Prime Minister Winston Churchill, sensing the iron curtain to come, questioned the strategy of surrendering key cities like Berlin, Prague, and Vienna to the Soviets, but the Americans simply wanted a speedy end to the war’s European chapter.27 Churchill’s arguments lost the day, and Eisenhower held fast at the Elbe.
Max and Marga would not have known of Eisenhower’s decision. Fighting just to move, they tried to stay safe. What would the Americans do with captured Germans? How long could Max Planck live without shelter in his condition?
Unbeknownst to the Plancks, a new menace grumbled forward from the other direction. The Red Army had overtaken Berlin and moved forward now to meet their American partners at the Elbe, unleashing violence along the way. The Soviet troops looked like the cast of a post-apocalyptic nightmare, as described by author Antony Beevor, “an extraordinary mixture of modern and medieval: tank troops in padded black helmets, Cossack cavalrymen on shaggy mounts with loot strapped to the saddle, lend-lease Studebakers and Dodges towing light field guns, and then a second echelon in horse-drawn carts.” To revenge themselves for the brutal German invasion of the Motherland, these troops took to raping women and girls, and shooting any male who dared to interfere. The occupying Red Army raped an estimated two million German women in 1945, regardless of age, pregnancy, or religious garb.28 As this force moved toward the Elbe, Max passed his eighty-seventh birthday in agony, with Marga comforting him as best she could.