Einstein's War

by Matthew Stanley

  Einstein took the critique in the spirit de Sitter had offered it. He was quick to reassure his friend that these were not very important questions: “I am sorry for having placed too much emphasis on the boundary conditions problem in our discussions. This is purely a matter of taste which will never gain scientific significance.” Nonetheless, he stuck with his investigations. He came to the view that the problem was the always-sticky concept of the “infinite”—infinite distance meant possibly infinite mass, and Mach’s principle would generate infinite inertia here on Earth, which made no sense. If he could get rid of the idea of an infinitely large universe, then those problems went away.

  He consulted with several astronomers in Germany, chiefly the old reliable Freundlich. What was known about the actual structure of the universe? Consensus of the time was that the Milky Way—the group of billions of stars to which our sun belongs—was essentially everything that existed. Astronomers had a decent estimate of the total mass and size of the Milky Way (about 10,000 light-years across). There were notable dissenters to this view, but Einstein, taking this as true, was on firm ground in 1916. So he had a blob of matter in an otherwise empty void, a fairly straightforward situation to calculate with his equations. He cranked out the numbers and found that in such a system (essentially the Milky Way) space-time would loop back in on itself, creating a pocket from which one could not escape—physicists thus give it the nickname “closed.”

  This meant the universe would have the peculiar status of being finite but unbounded. This is so counter to our intuitions that it is worth a moment to think about. Finite means you can run out of space in the universe. There would be a limit to how many Starbucks we can have. Our everyday experience suggests that if this is true, there must be an edge, a border, a place where you can see no more Starbucks. But in four-dimensional space-time this is not true. Stepping out of one coffee shop will always take you into another. Eventually, though, you will be back in the one where you started. There is no escape. The surface of the Earth is a useful analogy here. Our planet’s surface is finite (you could get enough paint to cover it) but unbounded (no matter how long you walk you will never get to the edge). Instead, you will eventually get back to where you started. Einstein’s universe worked the same way.

  There was an odd side effect, though. According to his equations this stellar blob’s own gravity should make it collapse, which didn’t seem to be happening. As he formally wrote, “The relative velocities of the stars are very small.” In other words, we’re not all crashing into one another. To explain why not, he did something extraordinary. He added an entirely new force to general relativity. It was the term λ (lambda), now called the cosmological constant, a placeholder for a mysterious repulsive force that would keep the universe from collapsing inward as a result of gravity. This was a difficult moment for Einstein. The whole point of general relativity was that it was supposed to emerge inevitably from a handful of universal principles, without any special fixes or adjustments. But this was the ultimate example of a special fix—the prediction of his equations (collapse) didn’t match observations (a fairly stable universe). So he just stuck λ in, like duct tape over a leaky pipe. He confessed that although this worked, it was not truly “justified by our actual knowledge.” He wasn’t very happy about this, and the physicist George Gamow called it Einstein’s greatest blunder.

  Nonetheless, it gave Einstein a finite universe with no edges, which was what he wanted. The specific numbers did not quite work out perfectly. His calculations predicted a universe about 10 million light-years across, as opposed to the 10,000 light-years astronomers had measured. He had confidence that further work on stellar statistics could help fix the problem. As usual when he encountered challenges with astronomical observations, he tried to enlist the erstwhile Erwin Freundlich to resolve things. And as usual, Einstein failed to get him any time off to make it happen.

  Einstein had created a new universe, with paper and ink and patient thought. This was not his goal—remember that he was just trying to see what the limits of his theory were. And writing to his friends, that was still what he emphasized: “It is at the very least proof that general relativity can lead to a system free of contradictions.” Along the way he found that the universe needed to be structured a particular way. As usual, solving one problem introduced others—how big was our home? Was there really a mysterious cosmological force pushing apart the stars? He wondered idly whether “the eternal enigma-giver” would ever let him truly understand the physical world. Surely “Jehovah did not found the world on such a crazy basis.”

  Einstein presented this to the Prussian Academy on February 5, 1917. What started as a small exploration became a challenging project, especially once his liver ailments severely cut back on his ability to work. He actually crafted the final version of the paper from his sickbed. He didn’t mind working from his bed—it cut down on visitors and allowed him to avoid the fine clothes required at the Academy. It did, however, mean he had to cancel his next trip to the Netherlands.

  Writing to his friends, Einstein confessed that the work would seem “rather outlandish.” To Paul Ehrenfest he wrote that it “exposes me a bit to the danger of being committed to a madhouse. I hope there are none over there in Leyden, so that I can visit you again safely.” He reassured everyone that he didn’t take these ideas about the whole cosmos too seriously even though “I argue as I do.” He particularly worried that de Sitter’s professional expertise would find this repellent: “From the standpoint of astronomy, of course, I have erected but a lofty castle in the air.” It was just a side effect of trying to resolve problems within relativity; it was not about reality. He could now forget about the infinities: “Now I am no longer plagued with the problem, while previously it gave me no peace.” Whether our universe was actually structured this way, he wrote, we could probably never know.

  De Sitter eagerly received the results from his own sickbed. He had contracted tuberculosis and was trying to work from a sanatorium near Doorn. He was not impressed with Einstein’s attempt at universe building. Simply juggling equations to determine the nature of the entire universe seemed a little much. He replied to Einstein: “Well, if you do not want to impose your conception on reality, then we are in agreement. I have nothing against it as a contradiction-free chain of reasoning, and I even admire it.”

  But within a week de Sitter had a change of heart and wondered what other universes were allowed by general relativity. Bizarrely, he found that a universe without any matter—completely empty—was perfectly compatible with Einstein’s equations. This featureless universe was, perplexingly, somehow also in motion. If two intrepid astronauts ventured into de Sitter’s cosmos, they would still have mass and would be driven apart. The nothingness was expanding. De Sitter pointed out that if general relativity allowed an empty universe in which individual objects can still have mass, then Mach’s principle could not be part of the theory—there were no distant masses to provide inertia. De Sitter did not really understand what this meant, and he was content with that: “I do not concern myself with explanations.” This was probably the end of Einstein’s infatuation with Mach’s principle, and general relativity went forward without it.

  * * *

  • • •

  DE SITTER AND Einstein continued to spar over their different universes. Was it possible to tell the difference by observation? Were certain inexplicable features “real” or just mathematical illusions? They ended up agreeing to disagree; Einstein dismissed it as a simple “difference in creed.” In other words, it was of no more significance than theological debates.

  Others picked up the project, though, taking it somewhat more seriously. Einstein and de Sitter had created the first and second of what we now call cosmological models, and accidentally invented the foundations of the modern field of relativistic cosmology. The entire discipline is built around the idea that these models can describe the true state of the
universe—static? moving? eternal? reincarnated?—and that observation could be used to decide between them. It is this field that eventually led us to our current models of a universe starting with a Big Bang and galaxies hurling apart. Quite different from the universe as Einstein and his contemporaries imagined it, our universe today is infinite and expanding, with our entire galaxy as no more than an insignificant speck. Einstein had no idea what he was setting in motion.

  WHILE EINSTEIN AND de Sitter were creating universes without boundaries, borders back on Earth continued to matter. In March 1917, several months after his debate with Einstein, de Sitter sent Eddington a letter describing the two models. Mail remained unreliable across the Channel—de Sitter speculated that the reason he never received any copies of his paper from the Monthly Notices was that the boat carrying the packet had been “probably torpedoed.” Unrestricted submarine warfare by German U-boats—the practice of torpedoing civilian ships without warning—had just resumed. After the sinking of the Lusitania, international outrage had brought a suspension of the practice. By early 1917, though, Germany’s fortunes of war looked grim enough to justify a resumption. Wrecks and bodies began to fill the Atlantic. In one month nearly a million tons of Allied and neutral merchant shipping was sunk by the Germans. And it looked like it might work. British grain supplies were down to six weeks’ worth.

  Berlin felt increasingly surreal to Einstein. “When I speak with people, I sense the pathology of the general state of mind. The times recall the witch trials and other religious misjudgments.” He felt as though the people who were kindest and most thoughtful in private were somehow also the most despicably patriotic in public. By the spring, he was venturing out occasionally, sometimes to take part in meetings of the Deutsche Friedensgesellschaft (or DFG, the German Peace Society). They met at the Café Austria. One of the other members was surprised to learn that Einstein was someone important in the scientific world. The DFG was no more welcomed by the government than the BNV was, and one meeting in April was broken up by the police.

  Whom could he trust? His fellow pacifist Friedrich Wilhelm Foerster asked him to write something on general relativity for the popular reader. Foerster worried that the only thing most Germans knew about relativity was that it opposed British science by replacing Newton’s gravity. “This agitation is probably connected to the almost psychopathic state of the current, widely spread sentiments among the populace.”

  It was not clear what the future would bring for Einstein and his theories. Relativity had managed to cross the trenches and find a foothold in enemy lands. But his hopes for confirmation of the theory—empirical support for his abstract speculations—remained as frustrated as ever by the war. Seeing the gravitational deflection of light seemed an almost idle fantasy. The war showed no signs of slowing or international science of resuming. His brief excursions to the outer reaches of the universe did not help him escape the brutal situation humanity had made for itself: “It is a pity that we do not live on Mars and just observe man’s nasty antics by telescope. . . . Jehovah no longer needs to send down showers of ash and brimstone; he has modernized and has set this mechanism to run on automatic.”

  CHAPTER 9

  The Resistance to Relativity

  “The most remarkable publication during the war.”

  ELSA WAS TRYING to keep Albert alive. This became much easier to do once he moved into the apartment next door to her on Haberlandstrasse in the summer of 1917. One of her goals was to keep him to one cigar a day. Previously his office was known for being filled with a blue haze of smoke almost constantly. No more. Although her efforts to keep his lungs working were constantly sabotaged by his friends, who would smuggle him a second or third cigar when she wasn’t looking.

  Keeping him alive also meant taking care of him throughout his increasingly acute illness. This included cooking his special meals. Elsa had been trying to get him to move closer to make this easier but he resisted. So while he was away visiting family, she simply moved him into her building herself. She may have regretted this decision once she discovered that he snored “unbelievably loudly.” He accepted the change with equanimity: “The grub is good and I rest a lot.” She kept him eating healthy even when he was traveling—while in Frankfurt he sent a letter assuring her that he was still following the doctor’s orders. The envelope also included her keys to the apartment, which he had thoughtlessly taken with him. In Zurich he excitedly wrote that he had found a bar of soap and a tube of toothpaste he would bring back for her. This was the last of his wartime trips. The military authorities decided that he was, in fact, a political danger (he was number 9 on a list of 31 pacifists) and they would soon restrict his movements to officially approved travel only.

  Back in Berlin he continued to receive his food parcels from friends. He warned them not to seal any packages they sent because the military censors would open them anyway, or perhaps simply destroy them. The food was even more needed as supplies became tighter. As an unmarried man Einstein received only the completely inadequate “bachelor’s packages” of rations. The middle of 1917 saw the introduction of “ersatz ersatz” food—when the substitutes themselves had to be replaced with even faker food (coffee became roasted barley with coal tar, which became chicory with sugar beet). Haber, Fischer, and Nernst worked with the government to improve the nutritional value of what food was available. The black market became an essential part of life. At one point, all news of the war was eclipsed by rumors about a missing jam shipment. When some forward-thinking revolutionaries were stockpiling weapons, they successfully kept the police from inspecting the crates by claiming they were actually smuggling fruit.

  Einstein was starting to lose confidence in whether the work of he and his pacifist friends would make a difference. “All our exalted technological progress, civilization for that matter, is comparable to an axe in the hand of a pathological criminal.” The ax was sometimes falling close to home: his friend Georg Nicolai, who drafted the internationalist manifesto he signed at the beginning of the war, had just been court-martialed. Nicolai’s story was a bizarre one. A publicly avowed Socialist, he was a professor of physiology and private doctor in Berlin. A committed pacifist, he volunteered to run a cardiac clinic for the army, which provided enough political cover to continue practicing medicine and teaching.

  For a little while anyway. As his internationalist views became better known, the military drafted him and began transferring him from one awful posting to another (including an infirmary in a Russian POW camp in the middle of a swamp). One of the finest doctors in the country, he was reduced to working as an orderly. This did, however, give him plenty of time to work on his intellectual projects. He struggled to get his book The Biology of War, his explanation for why the war broke out, published in Switzerland. He finally succeeded in 1917, though the text was incomplete, out of order, and a general mess (he never even saw the proofs). The military authorities were watching closely, though, and court-martialed him. He was fined 1,200 marks and made to write a public letter disclaiming the book as punishment. He was court-martialed again a few months later, this time for insolence.

  Nicolai was unstoppable, though. He kept pressing Einstein to participate in a new publishing project, marshaling any argument that came to mind (including that, since Einstein hadn’t explicitly said he wouldn’t participate, he was really obligated to do so). Einstein couldn’t take it anymore and blasted off a crushing response: “Thus I raise my voice with the force of a bullock just come of age and ceremoniously, fervently, and energetically call (bellow) it off herewith.” He immediately regretted the outburst and sent an apology, saying his previous letter was merely “a coarse joke.” He still didn’t want anything to with Nicolai’s crazy project, though.

  Unfortunately for Albert, Nicolai was not his only politically complicated friend. The historian Peter Galison tells us the extraordinary story of Friedrich Adler. He had competed with Einstein for the Zurich pr
ofessorship in 1908, and lived in the same apartment building. Their families were friendly. Albert and Friedrich would talk physics. When Einstein went to Prague he hoped that Adler would replace him. Instead, Adler became a full-time radical Socialist, even meeting Trotsky in 1914.

  Like Einstein, Adler opposed the war. Unlike Einstein, he decided to do so by shooting the prime minister of Austria, Count Stürgkh. Shortly after disentangling himself from Nicolai, Einstein received a prison letter from Adler asking if he would be interested in discussing some aspects of relativity. Oh, and would Einstein mind being a character witness at his trial? Einstein quickly wrote a testimony praising Adler’s trustworthiness and asking the emperor for clemency. Adler continued to send his thoughts on relativity, which amounted to an alternative theory that leaned more toward Lorentz than Einstein. Adler’s father, desperate, tried to use his son’s alternative physics as evidence for an insanity defense. In May 1917, Adler was found guilty and sentenced to death, though his execution was stayed. From solitary confinement, perhaps with not much else to do, he continued to try to convince his old friend that his theory was fatally flawed.

  * * *

  LIKE EINSTEIN, EDDINGTON had trouble getting tobacco. Neither his sister nor Trimble minded his smoking, but his nicotine fix often ended up on the bottom of the Atlantic thanks to the U-boats. Alcohol was in short supply too. That wasn’t a problem for him—in 1917 he still kept to his mother’s old-fashioned advice on drinking. He actually offered the use of the observatory for the making of a temperance propaganda film at one point. Later in life he was trapped on a sweltering boat where the only drink available was Champagne. Once he gave it a try, he decided alcohol wasn’t so bad after all.