by P. D. Smith
One of the stories published in the first issue of Gernsback’s Amazing Stories was ‘The Man Who Saved the Earth’ by Austin Hall. In this apocalyptic story of heat rays and saviour scientists, a character argues that ‘an inventor is merely a poet with tools’ and that ‘the really great scientist should be a visionary’.20 In the 1950s Leo Szilard often described himself as being on a mission to ‘save the world’. Throughout his life he saw himself as a scientist in the mould of these early science fiction heroes, as both a visionary and an inventor. He said as much in the year before his death:
The creative scientist has much in common with the artist and the poet. Logical thinking and an analytical ability are necessary attributes of a scientist but they are far from sufficient for creative work. Those insights in science which have led to a breakthrough operate on the level of the subconscious. Science would run dry if all scientists were crank turners and if none of them were dreamers.21
Leo Szilard was certainly no ‘crank turner’. But practical invention formed an essential part of his scientific life and his self-image. His first German patent, filed in 1923, was for an X-ray sensitive cell, followed by patents for mercury vapour lamps. The sale of these patents to Siemens gave Leo Szilard a very necessary source of income. By 1924 he had become Max von Laue’s assistant – a great honour, but one with very little financial reward. Szilard may have ignored Einstein’s advice to find a job at a patent office, but he used Einstein’s experience of patents to become financially independent.
Many of Szilard’s inventions were never developed and ended up gathering dust on the patent office shelf. Often the intellectual stimulus of coming up with an idea was the only reward he wanted. Unlike other scientists, he showed little interest in the mundane business of conducting experiments and publishing results in academic journals. The thrill of invention was like a drug. Possessed by a compulsive intellectual wanderlust, he was always impatient to move on to the next brilliant idea – and he was never short of ideas. But as Szilard researcher Gene Dannen has said, ‘when you are as far ahead of your time as Szilard often was, the obstacles to the acceptance of your ideas can be almost insurmountable’.22 The life of a visionary scientist was not going to be easy.
One of Leo Szilard’s ideas did make the long journey from patent to fully functional machine. It was not a revolutionary new cyclotron, but a household refrigerator. In the winter of 1925/26, Einstein read a shocking story in the newspaper. A Berlin family, including several children, had died in their beds one night when poisonous fumes leaked from the coolant system of their refrigerator. The former patent officer was deeply shocked. But this human tragedy was by no means a rare occurrence. From the 1870s until 1929, the toxic gases methyl chloride, ammonia and sulphur dioxide were commonly used as refrigerants. As the ownership of refrigerators increased, so too did the number of poisonings. Some people even started keeping their refrigerator outside the house.
‘There must be a better way,’ said Einstein as he showed Leo Szilard the newspaper report. Szilard agreed, and the two physicists set out to design a safe refrigerator. They decided from the outset that ownership and profits on any inventions would be shared jointly. However, Szilard was just about to climb the next rung on the academic ladder and become a Privatdozent, a lecturer. In Germany this was a position not funded by the university; instead, lecturers received the fees paid by the students for attending a course. So Einstein generously suggested that if the young lecturer’s income ever dropped below what he had earned as von Laue’s assistant, then the Professor would waive his right to the refrigerator royalties. Although Einstein always enjoyed the appliance of science, especially if it meant saving lives, he clearly saw this project as a way of helping his young friend’s career.
Their collaboration was a great success. The two physicists worked together on this now forgotten project for seven years. From 1926, Einstein and Szilard filed more than forty-five patent applications for refrigerators in various countries. In the autumn of 1926, Szilard began supervising the construction of prototypes at Berlin’s Institute of Technology where he had been a student just a few years earlier. They came up with three highly innovative designs. As Szilard explained in a letter to his brother, ‘all three machines work without moving parts and are hermetically sealed’.23 Clearly, the desire to avoid fumes leaking from the refrigerator remained uppermost in their minds. Several companies expressed interest in their ideas, including AB Electrolux and the Allgemeine Elektrizitäts Gesellschaft (the German General Electric Company, or AEG).
Their most original attempt to tackle the problem of refrigeration, one that has found a far wider use today than either scientist could ever have imagined, was a revolutionary pump in which liquid metal was circulated by an electromagnetic field. It was an invention that could have come straight out of the pages of one of the electrical gadget magazines that Szilard loved as a boy.24 Einstein’s uncle, who invented dynamos and lighting systems, would also have been delighted by this example of electrotechnical ingenuity. He always said his nephew would go far.
The Einstein–Szilard pump had no moving parts because it used an electromagnetic field to push a liquid metal, such as potassium, through a cylinder. This acted as a piston to compress a refrigerant gas. As in conventional refrigerators, the gas then discharged its heat into the environment as it liquefied. When it was allowed to expand again, the refrigerant cooled and so absorbed heat from the cabinet of the refrigerator. Development work began on this ingenious refrigerator in autumn 1928 at the research institute of AEG. Szilard hired his Hungarian friend Albert Kornfeld (who later changed his name to Korodi) to work on the electrical engineering problems. He was assisted by another of Szilard’s fellow countrymen, Lazislas Bihaly. Szilard himself was employed by AEG as consultant on the project. At last, he could officially call himself ‘Director General’.
Together with royalties from other patents, his consultancy for AEG on the electromagnetic pump brought his annual earnings to $3,000 (about £30,000 today). It is not known whether Einstein ever took his share of the earnings from their joint bank account, but according to Korodi he took a close interest in the four-year project to develop the Einstein–Szilard pump, inspecting each prototype. Gene Dannen, who talked to Korodi in Hungary before he died in 1995, says that Korodi remembered visiting Einstein’s Berlin home with Leo Szilard at least a dozen times to discuss this and Szilard’s other inventions. ‘I didn’t talk to Einstein about physics,’ said Korodi with a laugh.25 He left that side of things to the Director General.
Unfortunately, when the two physicists started their search for a new and safer type of refrigerator, unknown to them an American chemist was also working on the same problem, but from a completely different angle. Thomas Midgley was a scientist at General Motors who also invented leaded petrol to prevent ‘knocking’ (pre-ignition) and later died from its side effects. He had been given the task of searching for a non-toxic and non-flammable refrigerant. In 1928, just as AEG began developing the Einstein–Szilard electromagnetic pump, Midgley discovered a ‘miracle compound’ which was later patented under the brand name of Freon.
Freon was the first of the chlorofluorocarbons, or CFCs, a group of organic compounds containing the elements carbon, fluorine (as well as other halogens such as chlorine) and hydrogen. They are colourless gases or liquids and have no smell. Most importantly from the point of view of refrigerators, they are non-flammable and toxic only in large quantities. Thomas Midgley chose a dramatic way to demonstrate this when he revealed his new compound to the public. At a meeting of the American Chemical Society in April 1930, Midgley inhaled Freon deep into his lungs and then used it to blow out a candle. No one would be poisoned in their beds by this gas – it was perfectly safe. Or so people thought. In the 1990s, a build-up of CFCs in the earth’s atmosphere was blamed for the depletion of the ozone layer. This artificial chemical had threatened to irrevocably damage the biosphere of the whole planet.
When it
was invented, Freon was thought to be a major step forward in producing safe refrigerators. In 1923, only 20,000 American households owned a refrigerator. By 1935, Frigidaire and its competitors had sold eight million new Freon refrigerators in the United States alone.26 The ingeniously engineered refrigerators dreamed up by Leo Szilard and Albert Einstein at the end of the 1920s stood no chance in the marketplace. Nevertheless, AEG continued to back development work on the Einstein–Szilard electromagnetic pump until 1932, when the Depression began to bite and the company was forced to slash its research projects by half. The pump was one of the casualties.
And so, unfortunately, no one ever used an Einstein–Szilard refrigerator to keep their groceries cool. The two men’s work wasn’t wasted, though. In 1942, as scientists at Chicago were planning how to build the first atomic pile and drawing up plans for the reactors that would produce the explosive new element, plutonium, it occurred to Leo Szilard that the electromagnetic pump would be ideal for cooling nuclear reactors. Exactly ten years after AEG shelved the commercial development of the Einstein–Szilard refrigerator, Szilard submitted a paper to his fellow Manhattan Project scientists on ‘A magnetic pump for liquid bismuth’.27
In November 1942, just a few weeks before the historic pile beneath the Stagg Field football stadium went critical, Szilard wrote: ‘The main purpose of operating a bismuth cooled power unit during the war is the production of about 1 ton of 94. This amount might be needed in order to win the war by means of atomic bombs, though one may hope that a smaller quantity will be sufficient.’28
Szilard assumed that a quarter of the uranium-235 in 150 tons of uranium would be transmuted into plutonium, or ‘94’ as he called it. He estimated this would produce 600 lb of plutonium in about 200 days. Ever on the lookout for ingenious inventions, he also predicted that because bismuth absorbed neutrons to form polonium, his reactor would also produce 250,000 luminous torches for the armed forces. The fact that the electromagnetic pump had no moving parts and thus required no servicing made the idea attractive for nuclear reactors as well as refrigeration.
At this time John Marshall became Szilard’s ‘hands’, the person who did all the Director General’s experimental work. Marshall was married to the physicist Leona Woods, the best known of the women scientists working on the Manhattan Project and the only woman present when the Chicago pile went critical. She thought Szilard was ‘a really amazing man’. But according to her husband, ‘Szilard was one of these guys who is a little bit too bright. He had the right conclusion as to what should be done but it would turn out in practice to be something that couldn’t be done for twenty years.’29
In the end, Szilard’s friend Eugene Wigner, who was in charge of reactor design, decided on a simpler solution than the electromagnetic pump: water-cooled reactors. Once again, Szilard had been too far ahead of his time. But he wasn’t daunted by this setback. By 1944 he was already looking forward to the coming age of nuclear power generation. In April he suggested using liquid metal cooling in a fast neutron reactor which was designed to produce as much plutonium as it burned. He called this revolutionary type of reactor a ‘breeder’, because it bred fuel. Enrico Fermi was immediately sceptical of this idea, just as he had been when Szilard first suggested, in 1939, that atomic bombs were possible. But Szilard was nothing if not tenacious. He brought up the idea again in 1945, claiming that he was ‘fairly confident’ that breeder reactors could be built which ‘double the investment of plutonium within about a year’.30
In a breeder reactor, the fuel consists of 90 per cent uranium-238 together with 10 per cent plutonium. There is no graphite to moderate the reaction by slowing neutrons. The fast neutrons are absorbed by the uranium, which is then transmuted into fissionable plutonium. The great advantage of this type of reactor is that, rather than merely burning uranium to create energy, the naturally abundant uranium-238 isotope is used in a cyclical process that simultaneously generates both fission energy and more nuclear fuel than there was in the first place.
As John Marshall said, in 1945 this was blue-sky thinking. But seven years later the Atomic Energy Commission revealed that it had built an experimental breeder reactor at Arco, Idaho. It worked byburning fissionable uranium-235 and using the neutrons released to transmute a ‘blanket’ of uranium-238 surrounding the reactor core into plutonium. This plutonium could then be used in other reactors or in atomic bombs. Walter H. Zinn was its designer, and, like his cadmium safety rod in the 1942 pile, it was nicknamed ZIP, which this time was short for ‘Zinn’s Infernal Pile’. Zinn revealed the details of the new reactor to the American public. One feature was its ‘unique’ electromagnetic pump.31
Progress on transforming Leo Szilard’s idea into reality has been slow. America has built just one commercial breeder reactor, which started operating in Michigan in 1969. Ironically, given his scepticism about the initial idea, it was called Fermi I. It is France that pioneered the subsequent commercial development of breeder reactors, beginning in the 1970s during the oil crisis. The French operated a fast neutron reactor power plant successfully from 1973 to 1990. It was named, appropriately enough, Phénix, after the mythical bird that is reborn in fire. For out of the nuclear fire of this reactor, new fuel was created.
After Phénix came Superphénix, built in 1985 thirty miles east of Lyon at Creys-Malville, on the Rhône. Like all fast neutron reactors it uses the Einstein–Szilard pump as part of a liquid metal cooling system. The French used liquid sodium. In 1998, the Russians revealed that they had been using lead–bismuth cooled reactors for forty years in their nuclear submarines. Both these liquid metals were proposed by Leo Szilard in his Manhattan Project research paper of April 1944. Indeed, future developments in reactor design lie in the direction of fast breeder reactors, probably using liquid metal coolants. Liquid metal cooling has also been used in reactors on satellites. Most recently, in 2005, liquid metal pumps have been miniaturized for use in computers, providing a revolutionary new approach to cooling for CPUs and even fuel cells.32
From Szilard’s theoretical work on thermodynamics (inspired by Einstein’s seminars on statistical mechanics) and the creative brainstorming of these two visionary physicists came an idea for a practical solution to an urgent problem that has subsequently been used in ways unimaginable at the time. In fiction too, their revolutionary pump has made its mark. In Tom Clancy’s cold-war thriller The Hunt for Red October (1984), the Soviets develop a silent, and thus undetectable, submarine thanks to an electromagnetic seawater propulsion system based on the Einstein–Szilard principle. American scientists did actually explore this idea in the 1950s but found it unfeasible, given the available technology.33
With their safer refrigerator, Einstein and Szilard had wanted to use science to save lives. But in an ironic twist to the story of the Einstein–Szilard pump, Szilard revived the idea in the atomic age as a way of creating the new fissile element plutonium for bombs. The invention that both of these humanistic scientists hoped would prevent deaths became part of the atomic arms race. Szilard’s work on the electromagnetic pump helped to provide him with an income during the turbulent years to come. The patents he applied for during the 1920s allowed him to concentrate all his creative energies on the subject that came to dominate his life – atomic energy. The cold war began, appropriately enough, in a refrigerator.
Einstein and Leo Szilard began designing refrigerators in 1926. This was also the year in which the final member of the Hungarian Quartet arrived in Germany. Edward Teller, born in 1908, was the youngest of the four Hungarian émigrés. Szilard was the oldest. John von Neumann was born in 1903, and Wigner a year later.
Teller began his scientific career by studying chemistry at Karlsruhe, where Fritz Haber had once taught. Like Szilard, he soon realized that physics was the more promising field and in 1928 moved first to Munich, where he studied under Arnold Sommerfeld, and then to Leipzig, where he became a postdoctoral student in the department of the brilliant quantum theorist, Werner Heisenbe
rg. It was an extraordinary period to be working in physics. According to Szilard’s Berlin friend Victor Weisskopf, there had never been a time in science ‘in which so much has been clarified by so few in so short a period’.34
The quantum revolution, which Einstein had helped to spark in 1905, had now been taken over by a new, younger generation of physicists which included Heisenberg and the Austrians Wolfgang Pauli and Erwin Schrödinger. Under their leadership, the physical world became stranger than the worst nightmares of the classical physicists. The new physics was founded on the counter-intuitive, even disturbing, principles of probability and uncertainty – notions which undermined the previously accepted view of the physical universe. Even causality and objective reality were challenged in this new era of subatomic physics. For Einstein, who had always been a reluctant revolutionary, such ideas were anathema. To his dying breath he refused to believe that the subatomic realm departed fundamentally from the laws that governed the macroscopic universe. Throughout the 1920s, the atomic nucleus remained shrouded in mystery, concealing the secrets of its composition from the curious eyes of the nuclear physicists. The great breakthrough in understanding would come in 1932. By then the golden age of physics was drawing to a close, and for Berlin, the city that had become the capital of physics, the party was almost over.
On 7 November 1926, Joseph Goebbels stepped off the train at the Anhalter Bahnhof in Berlin where, six years earlier, Leo Szilard had arrived. Adolf Hitler had just appointed the 29-year-old Gaufüghrer, or area commander, of Berlin. Goebbels had fallen under the spell of this political Caligari. In April, Goebbels wrote in his diary: ‘Adolf Hitler, I love you, because you are both great and simple. A genius.’35 His task was to build Hitler’s power base.
