A Brief History of Science with Levity

by Mike Bennett

  An estimated 2,754 civilians were killed in London by V-2 attacks, with another 6,523 injured, which is two people killed per V-2 rocket. However, this understates the potential of the V-2, since many rockets were misdirected and exploded harmlessly. Accuracy increased over the course of the war, particularly on batteries where the latest Leitstrahl Guide Beam apparatus was installed. Missile strikes were often devastating, causing large numbers of deaths; 160 civilians were killed and 108 seriously injured in one explosion on 25th November 1944 in mid-afternoon, when a V-2 hit Woolworth’s department store in New Cross, south-east London.

  After these deadly results, British intelligence spread more disinformation saying that the rockets were overshooting their London targets by 10 to 20 miles (16 to 32km). This tactic worked, and for the remainder of the war most V-2s landed on less heavily populated areas in Kent due to erroneous recalibration. The final two rockets exploded on 27th March 1945. One of these was the last V-2 to kill a British civilian. She was Mrs Ivy Millichamp, aged thirty-four, killed in her home in Kynaston Road, Orpington in Kent.

  Antwerp, Belgium was also the target for a large number of V-weapon attacks from October 1944 through March 1945, leaving 1,736 dead and 4,500 injured in greater Antwerp. Thousands of buildings were damaged or destroyed as the city was struck by 590 direct hits. The largest loss of life in a single attack came on 16th December 1944, when the roof of a crowded cinema was struck, leaving 567 dead and 291 injured.

  A scientific reconstruction carried out in 2010 demonstrated that the V-2 creates a crater 20m wide and 8m deep, ejecting approximately 3,000 tons of material into the air.

  Although the V-2 was an enormous technological achievement, in the final assessment it was probably not the best use of the German resources. The V-2 consumed a third of Germany’s fuel alcohol production and major portions of other critical technologies. To distil the fuel alcohol for one V-2 launch required 30 tonnes of potatoes at a time when food was becoming scarce. Due to a lack of explosives, concrete was used, and sometimes the warhead contained photographic propaganda of German citizens who had died in Allied bombing.

  The V-2 lacked a proximity fuse, so it could not be set for airburst, but buried itself in the target area before or just as the warhead detonated. This reduced its effectiveness. Furthermore, its early guidance systems were too primitive to hit specific targets and its costs were approximately equivalent to four-engine bombers. They were more accurate (though only in a relative sense), had longer ranges, carried many more warheads and were reusable. Moreover, the V-2 diverted resources from other, more effective programmes.

  That said, the limiting factor for German aviation after 1941 was always the availability of high-octane aviation fuel (not planes or pilots), so criticisms of the V-1 and V-2 programmes that compare their cost to hypothetical increases in fighter or bomber production are misguided. Nevertheless, the weapon had a considerable psychological effect because, unlike bombing planes or the V-1 Flying Bomb (which made a characteristic buzzing sound), the V2 travelled faster than the speed of sound, and gave no warning before impact. There was no effective defence, and no risk of pilot and crew casualties.

  In comparison, in one twenty-four-hour period during Operation Hurricane, the RAF dropped over 10,000 tons of bombs on Brunswick and Duisburg, roughly equivalent to the amount of explosives that could be delivered by 10,000 V-2 rockets.

  With the war all but lost, regardless of the factory output of conventional weapons, the Nazis resorted to V-weapons as a tenuous last hope to influence the war (hence Antwerp as a V-2 target), as an extension of their desire to “punish” their foes, and most importantly to give hope to their supporters with their miracle weapons. If the V-2 had no effect on the outcome of the war, its value was in its ingenuity, which set the stage for the next fifty years of ballistic military rocketry, culminating in the ICBMs of the Cold War and in the beginnings of modern space exploration.

  Following the defeat of the Nazis, Operation Paperclip recruited German engineers and transported the captured V-2 rockets and parts to the United States. At the close of World War II, over 300 rail cars filled with assorted V-2 parts, including engines, fuselages, propellant tanks, gyroscopes and associated equipment were brought to the rail yards in Las Cruces, New Mexico, so they could be placed on trucks and driven to the White Sands Proving Grounds, also in New Mexico.

  In addition to V-2 hardware, the US Government delivered German mechanisation equations for the V-2 guidance, navigation and control systems, as well as for advanced development concept vehicles, to US defence contractors for analysis. In the 1950s, some of these documents were useful to US contractors in developing direction cosine matrix transformations and other inertial navigation architecture concepts that were applied to early US programmes such as the Atlas and Minuteman guidance systems, as well as the Navy Submarine Inertial Navigation System.

  A committee was formed with military and civilian scientists to review payload proposals for the reassembled V-2 rockets. This led to an array of experiments that flew on V-2s, and paved the way for American-manned space exploration. Devices were sent aloft to sample the air at all levels to determine atmospheric pressures and to see what gases were present. Other instruments measured the level of cosmic radiation. The first photo from space was taken from a V-2 launched by US scientists on 24th October 1946.

  Only sixty-eight percent of the V-2 trials were considered successful. The Navy attempted to launch a German V-2 rocket at sea. One test launch from the aircraft carrier USS Midway was performed on 6th September 1947 as part of the Navy’s Operation Sandy. The test launch was a partial success, as the V-2 splashed down in the ocean only 10km (6 miles) from the carrier. This launch was notable as it used foldaway arms to prevent the missile from falling over. The arms pulled away just after the engine ignited, releasing the missile. The setup may look similar to the R-7 launch procedure, but in the case of the R-7, the trusses hold the full weight of the rocket, rather than just reacting to side forces. The US Redstone rocket is a direct descendant of the V-2.

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  CHAPTER 14

  Superconductivity is a phenomenon of exactly zero electrical resistance and the expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.

  Superconductivity was discovered in 1911 by Heike Onnes, who was studying the resistance of solid mercury at cryogenic temperatures using the recently produced liquid helium as a coolant. At the temperature of 4.2K, he observed that the electrical resistance abruptly disappeared. In the same experiment, he also observed the superfluid transition of helium at 2.2K, without recognising its significance. The precise date and circumstances of the discovery were only reconstructed a century later, when Onnes’ notebook was found. In subsequent decades, superconductivity was observed in several other materials. In 1913, lead was found to superconduct at 7K, and in 1941 niobium nitride was found to superconduct at 16K.

  For the readers coming from a non-scientific background, in this section we will discuss temperature in terms of degrees Kelvin (K). Coldness in itself is not a distinct physical property. It is merely the lack of heat (energy) within a material. Once all of the energy possible has been removed, the material is said to be at absolute zero.

  Absolute zero is the lower limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reaches its minimum value, taken as zero. Absolute zero is defined as precisely 0 K on the Kelvin scale, and it equates to -273.15 degrees Celsius on the Celsius scale with which we are all familiar.

  In common with ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. The electrical resistivity of a metallic conductor decreases gradually as the temperature is lowered. In ordina
ry conductors such as copper or silver, this decrease is limited by impurities and other defects. Even near zero K, a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing through a loop of superconducting wire can persist indefinitely with no power source.

  In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90K (-183°C). Such a high transition temperature is theoretically impossible for a conventional superconductor, leading to these new materials being termed as Class II or high temperature superconductors. Liquid nitrogen boils at 77 K, and superconduction at higher temperatures than this facilitated many experiments and applications that are less practical at lower temperatures.

  The microscopic structure of high temperature superconductors has long puzzled scientists seeking to harness their virtually limitless technological potential. Now, at last, researchers have deciphered the cryptic structure of one class of the superconductors, providing a basis for theories about how they manage to transport electricity with perfect efficiency when cooled, and how scientists might raise their operating temperature closer to the climes of everyday life.

  This goal, if realised, could make an array of fantastical technologies commercially viable, from power grids that never lose energy and cheap water purification systems to magnetically levitating vehicles. Scientists believe room-temperature superconductivity would have an impact on a par with that of the laser, a 1960s invention that now plays an important role in an estimated $7.5 trillion of economic activity.

  Louis Taillefer, a professor of physics at the University of Sherbrooke in Quebec, has said, “In the same way that a laser is a lot more powerful than a light bulb, room temperature superconductivity would completely change how you transport electricity and enable new ways of using electricity.”

  Materials that superconduct under much warmer conditions than their ultra-cooled predecessors were discovered in 1986, winning IBM researchers Georg Bednorz and K. Alex Müller the Nobel Prize in Physics soon after. But today, around three decades later, our current high-temperature superconductors still fall short of room-temperature operation by more than 100°C. The materials’ complexity has so far frustrated the dream of purpose-formulating their operating temperatures. Researchers currently say that new developments are firmly setting them on the right track.

  Until 1986, scientists generally believed that the accepted knowledge of physics at the time forbade superconductivity at temperatures above around 30K. In that year, Bednorz and Müller discovered superconductivity in a lanthanum-based cuprate perovskite material, which had a transition temperature of 35 K, and as a result of this were awarded the Nobel Prize for Physics in 1987. It was soon found that replacing the lanthanum with yttrium raised the critical temperature to 92 K.

  The primary superconducting components used by the author in the final, most powerful, version of his superconducting turbine (to be discussed in the next chapter) were constructed using yttrium barium cuprate (YBaCuO).

  Since that time, other superconductors have been developed with even higher transition temperatures, but yttrium barium cuprate will superconduct above the boiling point of liquid nitrogen. This is an inexpensive and readily available industrial material, and lends itself well to research into Class II Superconductors.

  Many other cuprate superconductors have since been discovered, and the theory of superconductivity in these materials is one of the major outstanding challenges of theoretical condensed matter physics. There are currently two main hypotheses – the resonating-valence-bond theory, and spin fluctuation, which has the most support in the research community. The second hypothesis proposed that electron pairing in high-temperature superconductors is mediated by short-range spin waves known as paramagnons.

  Since 1993, the highest temperature superconductor was a ceramic material consisting of mercury, barium, calcium, copper and oxygen (HgBa2Ca2Cu3O8+δ) with Tc = 133–138 K. The latter experiment (138 K) still awaits experimental confirmation, however.

  In February 2008, an iron-based family of high-temperature superconductors was discovered. Hideo Hosono, of the Tokyo Institute of Technology, and colleagues found lanthanum oxygen fluorine iron arsenide (LaO1-xFxFeAs), an oxypnictide that superconducts below 26 K. Replacing the lanthanum in LaO1-xFxFeAs with samarium leads to superconductors that work at 55 K.

  Subir Sachdev, a professor of physics at Harvard University, recently predicted the form of charge density waves, which he detailed as a possible mechanism behind high-temperature superconductivity. Although further tests are needed, Sachdev’s theory is gaining support from many experts, who say it succinctly captures key features of these materials. The various recent findings are at last starting to build a comprehensive picture of the physics behind high-temperature superconductivity.

  High-temperature superconductivity seems like a miracle of quantum mechanics; one that could be harnessed to great effect if only it could be properly understood.

  The property is exhibited primarily by cuprates, brittle ceramic materials composed of two-dimensional sheets of copper and oxygen separated by more complicated layers of atoms. When cuprates are cooled below a certain temperature, electrons in the copper-oxygen sheets suddenly overcome their mutual repulsion and pair up.

  With their powers combined, they behave like a different type of particle altogether, a boson, which has the unique ability to join with other bosons into a coherent swarm that moves as one. This bosonic swarm perfectly conducts electricity. A current flowing through a loop of cuprate wire will persist forever, or as long as the liquid nitrogen fridge stays on. Taillefer correctly said that the biggest question in this field is what force binds the electrons together, because if you can understand that force, you can then strengthen the force.

  In Class I superconductivity, the kind exhibited by many metals when they are cooled to near absolute zero, electron pairing is caused by gentle pressure waves that breeze through the metals. When an electron gets swept along by one of these waves, another follows in its wake, attracted by the positively charged metal atoms that shift toward the passing electron. But this light breeze cannot possibly explain pairing in cuprates, which survives at up to 160 K (-113 °C).

  Many competing forces seem to influence the electrons simultaneously, and the force that binds them together over such a broad temperature range must be strong enough to overcome others that strive to keep them apart. The devil is in disentangling the forces. In the words of Pegor Aynailian, an assistant professor of physics at Binghamton University in New York, “It feels like we’re in a battlefield and we don’t know who’s our ally and who’s our enemy.”

  The first sign of what looks increasingly like the enemy – charge density waves, also known as “charge order” – came in 2002. Using a new kind of microscope that could map currents on the surface of cuprates with nanometer resolution, Davis, then a professor at the University of California, Berkeley, and Jennifer Hoffman, his graduate student at the time, discovered a minute pattern of denser and less-dense ripples of electrons.

  These appeared wherever they hit the cuprate with a powerful magnetic field, an effect that suppressed superconductivity. Soon, other labs reported more actions that both killed superconductivity and produced the waves, such as raising the temperature or lowering the cuprates’ oxygen concentration.

  “You start to build this picture in which charge density waves are lurking, waiting to take over when anything unfriendly to superconductivity happens,” said Hoffman, who is now an associate professor at Harvard.

  It seemed possible that if the force shaping electrons into charge density waves could be suppressed, its rival, the force that forms superconducting pairs, would flourish. But some researchers argued that the ripples of electrons were merely a surface anomaly and irrelevant to superconductivity.

  The community still remains divided today, when t
wo groups using a technique called resonant X-ray scattering managed to detect charge density waves deep inside cuprates, cementing the importance of the waves. As the groups published their findings in Science and Nature Physics, two new collaborations formed, one led by Damascelli and the other by Ali Yazdani of Princeton University, with plans to characterise the waves even more thoroughly. Finishing in a dead heat, the rival groups’ independent studies appeared together in Science in January 2014. They confirmed that charge density waves are a ubiquitous phenomenon in cuprates and that they strenuously oppose superconductivity, prevailing as the temperature rises.

  CHAPTER 15

  When I attended high school in the 1960s I was fascinated by many of the science experiments that we performed. One of the most intriguing to me was that you could make a metallic/dielectric sandwich apparently lose weight merely by applying a high-voltage differential between the two metal plates. How could this be? This apparent weight loss had occurred even though the sandwich assembly still had the same mass and was still under the same gravitation attraction as it was prior to the plates being charged. This and similar events prompted me to investigate these types of phenomena further when I was older and had more money and time available to do so.