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Friday, June 30, 2017

Reading List: The Pope of Physics

Segrè, Gino and Bettina Hoerlin. The Pope of Physics. New York: Henry Holt, 2016. ISBN 978-1-62779-005-5.
By the start of the 20th century, the field of physics had bifurcated into theoretical and experimental specialties. While theorists and experimenters were acquainted with the same fundamentals and collaborated, with theorists suggesting phenomena to be explored in experiments and experimenters providing hard data upon which theorists could build their models, rarely did one individual do breakthrough work in both theory and experiment. One outstanding exception was Enrico Fermi, whose numerous achievements seemed to jump effortlessly between theory and experiment.

Fermi was born in 1901 to a middle class family in Rome, the youngest of three children born in consecutive years. As was common at the time, Enrico and his brother Giulio were sent to be wet-nursed and raised by a farm family outside Rome and only returned to live with their parents when two and a half years old. His father was a division head in the state railway and his mother taught elementary school. Neither parent had attended university, but hoped all of their children would have the opportunity. All were enrolled in schools which concentrated on the traditional curriculum of Latin, Greek, and literature in those languages and Italian. Fermi was attracted to mathematics and science, but little instruction was available to him in those fields.

At age thirteen, the young Fermi made the acquaintance of Adolfo Amidei, an engineer who worked with his father. Amidei began to loan the lad mathematics and science books, which Fermi devoured—often working out solutions to problems which Amidei was unable to solve. Within a year, studying entirely on his own, he had mastered geometry and calculus. In 1915, Fermi bought a used book, Elementorum Physicæ Mathematica, at a flea market in Rome. Published in 1830 and written entirely in Latin, it was a 900 page compendium covering mathematical physics of that era. By that time, he was completely fluent in the language and the mathematics used in the abundant equations, and worked his way through the entire text. As the authors note, “Not only was Fermi the only twentieth-century physics genius to be entirely self-taught, he surely must be the only one whose first acquaintance with the subject was through a book in Latin.”

At sixteen, Fermi skipped the final year of high school, concluding it had nothing more to teach him, and with Amidei's encouragement, sat for a competitive examination for a place at the elite Sculoa Normale Superiore, which provided a complete scholarship including room and board to the winners. He ranked first in all of the examinations and left home to study in Pisa. Despite his talent for and knowledge of mathematics, he chose physics as his major—he had always been fascinated by mechanisms and experiments, and looked forward to working with them in his career. Italy, at the time a leader in mathematics, was a backwater in physics. The university in Pisa had only one physics professor who, besides having already retired from research, had knowledge in the field not much greater than Fermi's own. Once again, this time within the walls of a university, Fermi would teach himself, taking advantage of the university's well-equipped library. He taught himself German and English in addition to Italian and French (in which he was already fluent) in order to read scientific publications. The library subscribed to the German journal Zeitschrift für Physik, one of the most prestigious sources for contemporary research, and Fermi was probably the only person to read it there. In 1922, after completing a thesis on X-rays and having already published three scientific papers, two on X-rays and one on general relativity (introducing what are now called Fermi coordinates, the first of many topics in physics which would bear his name), he received his doctorate in physics, magna cum laude. Just twenty-one, he had his academic credential, published work to his name, and the attention of prominent researchers aware of his talent. What he lacked was the prospect of a job in his chosen field.

Returning to Rome, Fermi came to the attention of Orso Mario Corbino, a physics professor and politician who had become a Senator of the Kingdom and appointed minister of public education. Corbino's ambition was to see Italy enter the top rank of physics research, and saw in Fermi the kind of talent needed to achieve this goal. He arranged a scholarship so Fermi could study physics in one the centres of research in northern Europe. Fermi chose Göttingen, Germany, a hotbed of work in the emerging field of quantum mechanics. Fermi was neither particularly happy nor notably productive during his eight months there, but was impressed with the German style of research and the intellectual ferment of the large community of German physicists. Henceforth, he published almost all of his research in either German or English, with a parallel paper submitted to an Italian journal. A second fellowship allowed him to spend 1924 in the Netherlands, working with Paul Ehrenfest's group at Leiden, deepening his knowledge of statistical and quantum mechanics.

Finally, upon returning to Italy, Corbino and his colleague Antonio Garbasso found Fermi a post as a lecturer in physics in Florence. The position paid poorly and had little prestige, but at least it was a step onto the academic ladder, and Fermi was happy to accept it. There, Fermi and his colleague Franco Rasetti did experimental work measuring the spectra of atoms under the influence of radio frequency fields. Their work was published in prestigious journals such as Nature and Zeitschrift für Physik.

In 1925, Fermi took up the problem of reconciling the field of statistical mechanics with the discovery by Wolfgang Pauli of the exclusion principle, a purely quantum mechanical phenomenon which restricts certain kinds of identical particles from occupying the same state at the same time. Fermi's paper, published in 1926, resolved the problem, creating what is now called Fermi-Dirac statistics (British physicist Paul Dirac independently discovered the phenomenon, but Fermi published first) for the particles now called fermions, which include all of the fundamental particles that make up matter. (Forces are carried by other particles called bosons, which go beyond the scope of this discussion.)

This paper immediately elevated the twenty-five year old Fermi to the top tier of theoretical physicists. It provided the foundation for understanding of the behaviour of electrons in solids, and thus the semiconductor technology upon which all our modern computing and communications equipment is based. Finally, Fermi won what he had aspired to: a physics professorship in Rome. In 1928, he married Laura Capon, whom he had first met in 1924. The daughter of an admiral in the World War I Italian navy, she was a member of one of the many secular and assimilated Jewish families in Rome. She was less than impressed on first encountering Fermi:

He shook hands and gave me a friendly grin. You could call it nothing but a grin, for his lips were exceedingly thin and fleshless, and among his upper teeth a baby tooth too lingered on, conspicuous in its incongruity. But his eyes were cheerful and amused.

Both Laura and Enrico shared the ability to see things precisely as they were, then see beyond that to what they could become.

In Rome, Fermi became head of the mathematical physics department at the Sapienza University of Rome, which his mentor, Corbino, saw as Italy's best hope to become a world leader in the field. He helped Fermi recruit promising physicists, all young and ambitious. They gave each other nicknames: ecclesiastical in nature, befitting their location in Rome. Fermi was dubbed Il Papa (The Pope), not only due to his leadership and seniority, but because he had already developed a reputation for infallibility: when he made a calculation or expressed his opinion on a technical topic, he was rarely if ever wrong. Meanwhile, Mussolini was increasing his grip on the country. In 1929, he announced the appointment of the first thirty members of the Royal Italian Academy, with Fermi among the laureates. In return for a lifetime stipend which would put an end to his financial worries, he would have to join the Fascist party. He joined. He did not take the Academy seriously and thought its comic opera uniforms absurd, but appreciated the money.

By the 1930s, one of the major mysteries in physics was beta decay. When a radioactive nucleus decayed, it could emit one or more kinds of radiation: alpha, beta, or gamma. Alpha particles had been identified as the nuclei of helium, beta particles as electrons, and gamma rays as photons: like light, but with a much shorter wavelength and correspondingly higher energy. When a given nucleus decayed by alpha or gamma, the emission always had the same energy: you could calculate the energy carried off by the particle emitted and compare it to the nucleus before and after, and everything added up according to Einstein's equation of E=mc². But something appeared to be seriously wrong with beta (electron) decay. Given a large collection of identical nuclei, the electrons emitted flew out with energies all over the map: from very low to an upper limit. This appeared to violate one of the most fundamental principles of physics: the conservation of energy. If the nucleus after plus the electron (including its kinetic energy) didn't add up to the energy of the nucleus before, where did the energy go? Few physicists were ready to abandon conservation of energy, but, after all, theory must ultimately conform to experiment, and if a multitude of precision measurements said that energy wasn't conserved in beta decay, maybe it really wasn't.

Fermi thought otherwise. In 1933, he proposed a theory of beta decay in which the emission of a beta particle (electron) from a nucleus was accompanied by emission of a particle he called a neutrino, which had been proposed earlier by Pauli. In one leap, Fermi introduced a third force, alongside gravity and electromagnetism, which could transform one particle into another, plus a new particle: without mass or charge, and hence extraordinarily difficult to detect, which nonetheless was responsible for carrying away the missing energy in beta decay. But Fermi did not just propose this mechanism in words: he presented a detailed mathematical theory of beta decay which made predictions for experiments which had yet to be performed. He submitted the theory in a paper to Nature in 1934. The editors rejected it, saying “it contained abstract speculations too remote from physical reality to be of interest to the reader.” This was quickly recognised and is now acknowledged as one of the most epic face-plants of peer review in theoretical physics. Fermi's theory rapidly became accepted as the correct model for beta decay. In 1956, the neutrino (actually, antineutrino) was detected with precisely the properties predicted by Fermi. This theory remained the standard explanation for beta decay until it was extended in the 1970s by the theory of the electroweak interaction, which is valid at higher energies than were available to experimenters in Fermi's lifetime.

Perhaps soured on theoretical work by the initial rejection of his paper on beta decay, Fermi turned to experimental exploration of the nucleus, using the newly-discovered particle, the neutron. Unlike alpha particles emitted by the decay of heavy elements like uranium and radium, neutrons had no electrical charge and could penetrate the nucleus of an atom without being repelled. Fermi saw this as the ideal probe to examine the nucleus, and began to use neutron sources to bombard a variety of elements to observe the results. One experiment directed neutrons at a target of silver and observed the creation of isotopes of silver when the neutrons were absorbed by the silver nuclei. But something very odd was happening: the results of the experiment seemed to differ when it was run on a laboratory bench with a marble top compared to one of wood. What was going on? Many people might have dismissed the anomaly, but Fermi had to know. He hypothesised that the probability a neutron would interact with a nucleus depended upon its speed (or, equivalently, energy): a slower neutron would effectively have more time to interact than one which whizzed through more rapidly. Neutrons which were reflected by the wood table top were “moderated” and had a greater probability of interacting with the silver target.

Fermi quickly tested this supposition by using paraffin wax and water as neutron moderators and measuring the dramatically increased probability of interaction (or as we would say today, neutron capture cross section) when neutrons were slowed down. This is fundamental to the design of nuclear reactors today. It was for this work that Fermi won the Nobel Prize in Physics for 1938.

By 1938, conditions for Italy's Jewish population had seriously deteriorated. Laura Fermi, despite her father's distinguished service as an admiral in the Italian navy, was now classified as a Jew, and therefore subject to travel restrictions, as were their two children. The Fermis went to their local Catholic parish, where they were (re-)married in a Catholic ceremony and their children baptised. With that paperwork done, the Fermi family could apply for passports and permits to travel to Stockholm to receive the Nobel prize. The Fermis locked their apartment, took a taxi, and boarded the train. Unbeknownst to the fascist authorities, they had no intention of returning.

Fermi had arranged an appointment at Columbia University in New York. His Nobel Prize award was US$45,000 (US$789,000 today). If he returned to Italy with the sum, he would have been forced to convert it to lire and then only be able to take the equivalent of US$50 out of the country on subsequent trips. Professor Fermi may not have been much interested in politics, but he could do arithmetic. The family went from Stockholm to Southampton, and then on an ocean liner to New York, with nothing other than their luggage, prize money, and, most importantly, freedom.

In his neutron experiments back in Rome, there had been curious results he and his colleagues never explained. When bombarding nuclei of uranium, the heaviest element then known, with neutrons moderated by paraffin wax, they had observed radioactive results which didn't make any sense. They expected to create new elements, heavier than uranium, but what they saw didn't agree with the expectations for such elements. Another mystery…in those heady days of nuclear physics, there was one wherever you looked. At just about the time Fermi's ship was arriving in New York, news arrived from Germany about what his group had observed, but not understood, four years before. Slow neutrons, which Fermi's group had pioneered, were able to split, or fission the nucleus of uranium into two lighter elements, releasing not only a large amount of energy, but additional neutrons which might be able to propagate the process into a “chain reaction”, producing either a large amount of energy or, perhaps, an enormous explosion.

As one of the foremost researchers in neutron physics, it was immediately apparent to Fermi that his new life in America was about to take a direction he'd never anticipated. By 1941, he was conducting experiments at Columbia with the goal of evaluating the feasibility of creating a self-sustaining nuclear reaction with natural uranium, using graphite as a moderator. In 1942, he was leading a project at the University of Chicago to build the first nuclear reactor. On December 2nd, 1942, Chicago Pile-1 went critical, producing all of half a watt of power. But the experiment proved that a nuclear chain reaction could be initiated and controlled, and it paved the way for both civil nuclear power and plutonium production for nuclear weapons. At the time he achieved one of the first major milestones of the Manhattan Project, Fermi's classification as an “enemy alien” had been removed only two months before. He and Laura Fermi did not become naturalised U.S. citizens until July of 1944.

Such was the breakneck pace of the Manhattan Project that even before the critical test of the Chicago pile, the DuPont company was already at work planning for the industrial scale production of plutonium at a facility which would eventually be built at the Hanford site near Richland, Washington. Fermi played a part in the design and commissioning of the X-10 Graphite Reactor in Oak Ridge, Tennessee, which served as a pathfinder and began operation in November, 1943, operating at a power level which was increased over time to 4 megawatts. This reactor produced the first substantial quantities of plutonium for experimental use, revealing the plutonium-240 contamination problem which necessitated the use of implosion for the plutonium bomb. Concurrently, he contributed to the design of the B Reactor at Hanford, which went critical in September 1944, running at 250 megawatts, that produced the plutonium for the Trinity test and the Fat Man bomb dropped on Nagasaki.

During the war years, Fermi divided his time among the Chicago research group, Oak Ridge, Hanford, and the bomb design and production group at Los Alamos. As General Leslie Groves, head of Manhattan Project, had forbidden the top atomic scientists from travelling by air, “Henry Farmer”, his wartime alias, spent much of his time riding the rails, accompanied by a bodyguard. As plutonium production ramped up, he increasingly spent his time with the weapon designers at Los Alamos, where Oppenheimer appointed him associate director and put him in charge of “Division F” (for Fermi), which acted as a consultant to all of the other divisions of the laboratory.

Fermi believed that while scientists could make major contributions to the war effort, how their work and the weapons they created were used were decisions which should be made by statesmen and military leaders. When appointed in May 1945 to the Interim Committee charged with determining how the fission bomb was to be employed, he largely confined his contributions to technical issues such as weapons effects. He joined Oppenheimer, Compton, and Lawrence in the final recommendation that “we can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use.”

On July 16, 1945, Fermi witnessed the Trinity test explosion in New Mexico at a distance of ten miles from the shot tower. A few seconds after the blast, he began to tear little pieces of paper from from a sheet and drop them toward the ground. When the shock wave arrived, he paced out the distance it had blown them and rapidly computed the yield of the bomb as around ten kilotons of TNT. Nobody familiar with Fermi's reputation for making off-the-cuff estimates of physical phenomena was surprised that his calculation, done within a minute of the explosion, agreed within the margin of error with the actual yield of 20 kilotons, determined much later.

After the war, Fermi wanted nothing more than to return to his research. He opposed the continuation of wartime secrecy to postwar nuclear research, but, unlike some other prominent atomic scientists, did not involve himself in public debates over nuclear weapons and energy policy. When he returned to Chicago, he was asked by a funding agency simply how much money he needed. From his experience at Los Alamos he wanted both a particle accelerator and a big computer. By 1952, he had both, and began to produce results in scattering experiments which hinted at the new physics which would be uncovered throughout the 1950s and '60s. He continued to spend time at Los Alamos, and between 1951 and 1953 worked two months a year there, contributing to the hydrogen bomb project and analysis of Soviet atomic tests.

Everybody who encountered Fermi remarked upon his talents as an explainer and teacher. Seven of his students: six from Chicago and one from Rome, would go on to win Nobel Prizes in physics, in both theory and experiment. He became famous for posing “Fermi problems”, often at lunch, exercising the ability to make and justify order of magnitude estimates of difficult questions. When Freeman Dyson met with Fermi to present a theory he and his graduate students had developed to explain the scattering results Fermi had published, Fermi asked him how many free parameters Dyson had used in his model. Upon being told the number was four, he said, “I remember my old friend Johnny von Neumann used to say, with four parameters I can fit an elephant, and with five I can make him wiggle his trunk.” Chastened, Dyson soon concluded his model was a blind alley.

After returning from a trip to Europe in the fall of 1954, Fermi, who had enjoyed robust good health all his life, began to suffer from problems with digestion. Exploratory surgery found metastatic stomach cancer, for which no treatment was possible at the time. He died at home on November 28, 1954, two months past his fifty-third birthday. He had made a Fermi calculation of how long to rent the hospital bed in which he died: the rental expired two days after he did.

There was speculation that Fermi's life may have been shortened by his work with radiation, but there is no evidence of this. He was never exposed to unusual amounts of radiation in his work, and none of his colleagues, who did the same work at his side, experienced any medical problems.

This is a masterful biography of one of the singular figures in twentieth century science. The breadth of his interests and achievements is reflected in the list of things named after Enrico Fermi. Given the hyper-specialisation of modern science, it is improbable we will ever again see his like.

Posted at 21:00 Permalink

Wednesday, June 28, 2017

Reading List: Defying Hitler

Haffner, Sebastian [Raimund Pretzel]. Defying Hitler. New York: Picador, [2000] 2003. ISBN 978-0-312-42113-7.
In 1933, the author was pursuing his ambition to follow his father into a career in the Prussian civil service. While completing his law degree, he had obtained a post as a Referendar, the lowest rank in the civil service, performing what amounted to paralegal work for higher ranking clerks and judges. He enjoyed the work, especially doing research in the law library and drafting opinions, and was proud to be a part of the Prussian tradition of an independent judiciary. He had no strong political views nor much interest in politics. But, as he says, “I have a fairly well developed figurative sense of smell, or to put it differently, a sense of the worth (or worthlessness!) of human, moral, political views and attitudes. Most Germans unfortunately lack this sense almost completely.”

When Hitler came to power in January 1933, “As for the Nazis, my nose left me with no doubts. … How it stank! That the Nazis were enemies, my enemies and the enemies of all I held dear, was crystal clear to me from the outset. What was not at all clear to me was what terrible enemies they would turn out to be.” Initially, little changed: it was a “matter for the press”. The new chancellor might rant to enthralled masses about the Jews, but in the court where Haffner clerked, a Jewish judge continued to sit on the bench and work continued as before. He hoped that the political storm on the surface would leave the depths of the civil service unperturbed. This was not to be the case.

Haffner was a boy during the First World War, and, like many of his schoolmates, saw the war as a great adventure which unified the country. Coming of age in the Weimar Republic, he experienced the great inflation of 1921–1924 as up-ending the society: “Amid all the misery, despair, and poverty there was an air of light-headed youthfulness, licentiousness, and carnival. Now, for once, the young had money and the old did not. Its value lasted only a few hours. It was spent as never before or since; and not on the things old people spend their money on.” A whole generation whose ancestors had grown up in a highly structured society where most decisions were made for them now were faced with the freedom to make whatever they wished of their private lives. But they had never learned to cope with such freedom.

After the Reichstag fire and the Nazi-organised boycott of Jewish businesses (enforced by SA street brawlers standing in doors and intimidating anybody who tried to enter), the fundamental transformation of the society accelerated. Working in the library at the court building, Haffner is shocked to see this sanctum of jurisprudence defiled by the SA, who had come to eject all Jews from the building. A Jewish colleague is expelled from university, fired from the civil service, and opts to emigrate.

The chaos of the early days of the Nazi ascendency gives way to Gleichschaltung, the systematic takeover of all institutions by placing Nazis in key decision-making positions within them. Haffner sees the Prussian courts, which famously stood up to Frederick the Great a century and a half before, meekly toe the line.

Haffner begins to consider emigrating from Germany, but his father urges him to complete his law degree before leaving. His close friends among the Referendars run the gamut from Communist sympathisers to ardent Nazis. As he is preparing for the Assessor examination (the next rank in the civil service, and the final step for a law student), he is called up for mandatory political and military indoctrination now required for the rank. The barrier between the personal, professional, and political had completely fallen. “Four weeks later I was wearing jackboots and a uniform with a swastika armband, and spent many hours each day marching in a column in the vicinity of Jüterbog.”

He discovers that, despite his viewing the Nazis as essentially absurd, there is something about order, regimentation, discipline, and forced camaraderie that resonates in his German soul.

Finally, there was a typically German aspiration that began to influence us strongly, although we hardly noticed it. This was the idolization of proficiency for its own sake, the desire to do whatever you are assigned to do as well as it can possibly be done. However senseless, meaningless, or downright humiliating it may be, it should be done as efficiently, thoroughly, and faultlessly as could be imagined. So we should clean lockers, sing, and march? Well, we would clean them better than any professional cleaner, we would march like campaign veterans, and we would sing so ruggedly that the trees bent over. This idolization of proficiency for its own sake is a German vice; the Germans think it is a German virtue.

That was our weakest point—whether we were Nazis or not. That was the point they attacked with remarkable psychological and strategic insight.

And here the memoir comes to an end; the author put it aside. He moved to Paris, but failed to become established there and returned to Berlin in 1934. He wrote apolitical articles for art magazines, but as the circle began to close around him and his new Jewish wife, in 1938 he obtained a visa for the U.K. and left Germany. He began a writing career, using the nom de plume Sebastian Haffner instead of his real name, Raimund Pretzel, to reduce the risk of reprisals against his family in Germany. With the outbreak of war, he was deemed an enemy alien and interned on the Isle of Man. His first book written since emigration, Germany: Jekyll and Hyde, was a success in Britain and questions were raised in Parliament why the author of such an anti-Nazi work was interned: he was released in August, 1940, and went on to a distinguished career in journalism in the U.K. He never prepared the manuscript of this work for publication—he may have been embarrassed at the youthful naïveté in evidence throughout. After his death in 1999, his son, Oliver Pretzel (who had taken the original family name), prepared the manuscript for publication. It went straight to the top of the German bestseller list, where it remained for forty-two weeks. Why? Oliver Pretzel says, “Now I think it was because the book offers direct answers to two questions that Germans of my generation had been asking their parents since the war: ‘How were the Nazis possible?’ and ‘Why didn't you stop them?’ ”.

This is a period piece, not a work of history. Set aside by the author in 1939, it provides a look through the eyes of a young man who sees his country becoming something which repels him and the madness that ensues when the collective is exalted above the individual. The title is somewhat odd—there is precious little defying of Hitler here—the ultimate defiance is simply making the decision to emigrate rather than give tacit support to the madness by remaining. I can appreciate that.

This edition was translated from the original German and annotated by the author's son, Oliver Pretzel, who wrote the introduction and afterword which place the work in the context of the author's career and describe why it was never published in his lifetime. A Kindle edition is available.

Thanks to Glenn Beck for recommending this book.

Posted at 00:28 Permalink

Monday, June 26, 2017

Reading List: Into the Looking Glass

Ringo, John. Into the Looking Glass. Riverdale, NY: Baen Publishing, 2005. ISBN 978-1-4165-2105-1.
Without warning, on a fine spring day in central Florida, an enormous explosion destroys the campus of the University of Central Florida and the surrounding region. The flash, heat pulse, and mushroom cloud are observed far from the site of the detonation. It is clear that casualties will be massive. First responders, fearing the worst, break out their equipment to respond to what seems likely to be nuclear terrorism. The yield of the explosion is estimated at 60 kilotons of TNT.

But upon closer examination, things seem distinctly odd. There is none of the residual radiation one would expect from a nuclear detonation, nor evidence of the prompt radiation nor electromagnetic pulse expected from a nuclear blast. A university campus seems an odd target for nuclear terrorism, in any case. What else could cause such a blast of such magnitude? Well, an asteroid strike could do it, but the odds against such an event are very long, and there was no evidence of ejecta falling back as you'd expect from an impact.

Faced with a catastrophic yet seemingly inexplicable event, senior government officials turn to a person with the background and security clearances to investigate further: Dr. Bill Weaver, a “redneck physicist” from Huntsville who works as a consultant to one of the “Beltway bandit” contractors who orbit the Pentagon. Weaver recalls that a physicist at the university, Ray Chen, was working on shortcut to produce a Higgs boson, bypassing the need for an enormous particle collider. Weaver's guess is that Chen's idea worked better than he imagined, releasing a pulse of energy which caused the detonation.

If things so far seemed curious, now they began to get weird. Approaching the site of the detonation, teams observed a black globe, seemingly absorbing all light, where Dr. Chen's laboratory used to be. Then one, and another, giant bug emerge from the globe. Floridians become accustomed to large, ugly-looking bugs, but nothing like this—these are creatures from another world, or maybe universe. A little girl, unharmed, wanders into the camp, giving her home address as in an area completely obliterated by the explosion. She is clutching a furry alien with ten legs: “Tuffy”, who she says speaks to her. Scientists try to examine the creature and quickly learn the wisdom of the girl's counsel to not mess with Tuffy.

Police respond to a home invasion call some distance from the site of the detonation: a report that demons are attacking their house. Investigating, another portal is discovered in the woods behind the house, from which monsters begin to issue, quickly overpowering the light military force summoned to oppose them. It takes a redneck militia to reinforce a perimeter around the gateway, while waiting for the Army to respond.

Apparently, whatever happened on the campus not only opened a gateway there, but is spawning gateways further removed. Some connect to worlds seemingly filled with biologically-engineered monsters bent upon conquest, while others connect to barren planets, a race of sentient felines, and other aliens who may be allies or enemies. Weaver has to puzzle all of this out, while participating in the desperate effort to prevent the invaders, “T!Ch!R!” or “Titcher”, from establishing a beachhead on Earth. And the stakes may be much greater than the fate of the Earth.

This is an action-filled romp, combining the initiation of humans into a much larger universe worthy of Golden Age science fiction with military action fiction. I doubt that in the real world Weaver, the leading expert on the phenomenon and chief investigator into it, would be allowed to participate in what amounts to commando missions in which his special skills are not required but, hey, it makes the story more exciting, and if a thriller doesn't thrill, it has failed in its mission.

I loved one aspect of the conclusion: never let an alien invasion go to waste. You'll understand what I'm alluding to when you get there. And, in the Golden Age tradition, the story sets up for further adventures. While John Ringo wrote this book by himself, the remaining three novels in the Looking Glass series are co-authored with Travis S. Taylor, upon whom the character of Bill Weaver was modeled.

Posted at 21:50 Permalink

Cellular Automata Laboratory: Bak-Tang-Wiesenfeld Sandpile Model

A new rule in Cellular Automata Laboratory (CelLab) implements the Bak-Tang-Wiesenfeld sandpile model [BakTang&Wiesenfeld87]. In each generation, a single grain of sand falls on the cell at the center of the map. When the pile of sand in any cell reaches a height of four grains, it becomes unstable and topples, with the four grains it contains distributed to its four von Neumann neighbors. If this process results in one of more of the neighbors containing four grains, they in turn topple and the process continues until no cell contains four grains. This was the first model discovered which exhibits the property of self-organized criticality. The system exhibits avalanches whose size follows a power law: many small, local events, and a few rare large ones.

Color is used to represent the number of grains in each cell: grey for none, blue for 1, yellow for 2, and red for 3. Since a cell with four grains immediately topples, no cell can contain more than three grains. As the pile grows, you will see how the addition of a single grain can cause cascades of all sizes. While you might expect a smoothly growing structure, in fact the depth of the sand in the pile exhibits a complex fractal pattern that emerges as the pile grows. The edges of the map consume any grains which reach them: they limit the growth of the pile.

If you're patient and have a high-resolution screen, try running Sand in the double-wide simulator—it will produce intricate mandala patterns. The Sand rule is entirely implemented within the sand user evaluator. This is an interesting mathematical model which has proved useful in analyzing emergent processes in a variety of fields. It does not, however, accurately model the behavior of actual piles of sand.

Run the Sandpile simulation in CelLab
Run the Sandpile simulation (double-wide)

Posted at 13:03 Permalink

Saturday, June 24, 2017

Cellular Automata Laboratory: Reproduction, Evolution, Abiogenesis, and Sex

The latest collection of rules for Cellular Automata Laboratory (CelLab) illustrates aspects of self-reproduction and analogues to biological systems. Basic self-reproduction is demonstrated by the Langton rule, in which a loop of digital “DNA” provides the instructions to replicate itself and its enclosing structure, creating new identical digital organisms.

Ever since John von Neumann discovered the first self-reproducing cellular automaton rule in 1952, a challenge has been to find simpler and faster-replicating rules. Von Neumann's original rule used 29 states, while Langton, in 1984, simplified this to just 8 states, an initial pattern of 86 cells, and 151 generations to replicate. The latest update to CelLab includes the Byl and Chou-Reggia rules, which further simplify a replicator to (Byl) 12 cells, 6 states, and 25 generations to replicate; and (Chou-Reggia) 5 cells, 8 states, and replication in just 15 generations.

These are all exact replication: every descendant is a precise copy of its ancestor. Biological replication is messier yet more powerful, since it permits evolutionary change and adaptation to the environment. In 1998, Hirokia Sayama published Evoloops, a generalisation of Langton's replicator which allows individual replicators that collide in a world of limited space to mutate, often leading to selection for smaller, faster-replicating organisms not present in the original simulation. Precisely the same phenomenon is observed in bacteria grown with limited resources. Evoloops can also demonstrate abiogenesis: the appearance of replicators from random interactions of non-replicating structures in a “primordial soup”.

In 2007 and 2009, Nicholas Oros further generalised Evoloops to create Sexyloop, which stirs recombination of genetic information, similar to that which occurs in sexual reproduction, into the mix. Now, when digital organisms interact, they can exchange genetic information, so a behaviour which appears spontaneously in one organism can propagate to others, similar to gene transmission in bacterial conjugation and, if adaptive, come to dominate the population.

Run the Byl replicator in CelLab
Run the Chou-Reggia replicator
Run Evoloops evolution experiment
Run Evoloops abiogenesis experiment
Run Sexyloop simulation

Posted at 23:27 Permalink

Tuesday, June 20, 2017

Cellular Automata Laboratory: Langton's Ant

I have added another new rule to Cellular Automata Laboratory (CelLab): Langton's Ant. This rule was discovered by Christopher Langton in 1986, and is one of the simplest known moving-head Turing machine rules which exhibits complex behaviour.

It is a two-dimensional Turing machine with a head (ant) that moves on a map of cells which can be in one of two states. In each generation, the head moves to an adjacent cell, inverting the state of the cell it departs. The head can move in one of the four directions in the von Neumann neighborhood; the direction it moves is set by the current state of the head. Upon moving to a new cell, the head adjusts its direction by turning clockwise if the cell's state is zero and counterclockwise if it is one.

When started with an all-zero map, the head starts by tracing out a lacy pattern exhibiting symmetries, but then, as the pattern grows, appears to be following a random walk, occasionally adding to the borders of the pattern. After around 10,000 generations, however, the head will begin to create a “highway” which extends in a diagonal direction in a cycle of 104 generations. This is an example of spontaneous emergence of order after a long period of apparently chaotic behavior. If run on an infinite map, the highway would extend without bound, but on our wrap-around map, it will eventually collide with the original random pattern, producing interesting interactions. All starting configurations which have been tested eventually produce a highway, but it has not been proved that every possible configuration does so. It has, however, been proved that the pattern always grows without bound in some manner. Try starting the rule on the square pattern and watch how it evolves into a lattice of ordered highways and burl-like intersections.

Run the Langton's Ant rule in CelLab

Posted at 23:09 Permalink

Monday, June 19, 2017

Autour de la Lune: Web Edition Updated

I have just posted an updated version of Jules Verne's 1870 novel Autour de la Lune (Around the Moon). This is the sequel to 1865's De la terre à la lune (From the Earth to the Moon), which left our intrepid explorers apparently stranded in orbit around the Moon.

The present novel picks up the story from inside the projectile moments before it was fired from the giant cannon toward the Moon and recounts their subsequent adventures. As always, Verne does not stint on details, and readers will learn much of what was known in the mid-19th century about selenography. The story is not the classic the original work was, nor does it have the subtext of technology as a modern sacrament, but it is a worthy sequel.

The original version Web version was posted in 2002. This edition updates all of the documents to contemporary Web standards (XHTML 1.0 Strict and CSS3), uses Unicode for text elements such as ellipses and dashes, improves formatting and navigation, and corrects a few typographical errors.

Posted at 20:20 Permalink

Sunday, June 18, 2017

HotBits: New Version with API Keys, Pseudorandom Generation

I have just posted a new version of the HotBits radioactive random number generator Web support software. There are no changes to the actual generation process or hardware, which remain as previously documented. All changes are to the proxy server, which obtains random data from the generators and delivers them to requesters over the Web.

API Keys

The first change is the phased introduction of API Keys, which requesters must use to obtain random data. Since the original introduction of HotBits in 1996, anybody has been able to request random data generated from radioactive decay over the Web, constrained only a quota limiting requests from an IP address to 12,208 bytes or 120 requests, whichever comes first, in any 24-hour period (the quota is applied by an aging algorithm measuring rate, and does not have a hard cutoff on day boundaries). The reason for the imposition of a quota is that the hardware generators produce only around 100 bytes per second, and it would be easy for a user to exhaust this capacity, either inadvertently or in order to wreck the service and deny it to others out of malice.

This policy worked well for more than twenty years, but with increasing blight in the Internet slum, more and more distributed denial of service attacks against HotBits have been mounted over recent months. These are conducted from a multitude of IP addresses, most of which make only one or a few requests, and thereby evade the quota. I do not know the motive for these attacks—probably it's just a nihilistic desire to wreck something provided for free to others; there's plenty of that around on the Internet—no good deed goes unpunished. In any case, this irresponsible behaviour of a few results, as it usually does, in making things inconvenient for the large majority of legitimate users.

Beginning on July 1st, 2017, requests for random data from HotBits will require an API Key, which is either entered in a box in the request page or via an “apikey=key” query field in a direct request URL. Requests without a valid API key will be rejected with an error message. HotBits users can apply for an API Key starting today, by using the:

HotBits API Key Request Form

API Keys are typically issued with two days of being requested. Once you receive your API Key, you can begin to use it immediately with the Request HotBits (API) test page. On July 1st, this will be come the standard request page and an API Key will be required for all requests.

Pseudorandom Data

When you visit the new request page, you'll notice a new option at the bottom: “Pseudorandom data?”. The most common application of genuine random data is to “seed” a pseudorandom number generator which can then produce a large volume of data which passes all of the statistical tests for randomness. HotBits now provides such data without the need for users to set up and validate their own generator. When you check the box, HotBits will return data from its own high quality internal pseudorandom number generator which is seeded from radioactively-generated data from the HotBits hardware generator. Requests for pseudorandom data do not require an API key and are not subject to quota limitations. You can also request pseudorandom data by specifying “Pseudorandom” as an API Key. Pseudorandom data in the hexadecimal, C, password, and XML formats is identified as such in the result page returned.

The pseudorandom data returned by HotBits are generated with the Mersenne twister algorithm, using the MT19937-64 (64-bit) version. The generator is seeded with 2496 bytes of radioactively-generated random data from the HotBits generators. Because the Mersenne twister algorithm is not cryptographically secure, in that by observing a sufficiently large number of results it is possible to predict subsequent output, the pseudorandom data supplied by HotBits is produced by taking pairs of 64-bit results from Mersenne twister, comprising a 16 byte block, encrypting the block using the Advanced Encryption Standard (AES) with a 256 bit secret key also obtained from radioactively-generated HotBits data, then returning encrypted 16 byte blocks to fill the request. (Multiple blocks are generated if the request is more than 16 bytes, and if the request is not a multiple of 16 bytes, excess bytes from the last block are discarded.) A new AES encryption key is generated every 30 minutes, so even were a key to be disclosed, it would only enable decryption of data returned during the half hour window in which it was in use. Fourmilab makes no claim about the suitability of this pseudorandom data for cryptographic or any other use; that is up to you to determine based upon your own testing of the data and auditing of the algorithms and code used to generate it. Complete source code of the HotBits server, including the pseudorandom generator, will be posted when the new version enters production on July 1st, 2017. Statistical testing of the pseudorandom generator, including the downloadable data sets used in the tests, is currently available.

Posted at 11:45 Permalink

Tuesday, June 13, 2017

Cellular Automata Laboratory: Bootstrap Percolation

Here's another new rule for Cellular Automata Laboratory (CelLab): Bootperc. The rule illustrates the process of bootstrap percolation in statistical mechanics. The rule is started with a random pattern in which some fraction of cells are set to 1 with the others zero. On each generation, zero cells look at their neighbours (either 4 for the von Neumann neighbourhood or 8 for the Moore neighbourhood) and, if the number of nonzero neighbours exceeds a threshold (2 for the 4-neighbour case, 4 for 8 neighbours), become ones. A cell, once set to one, remains forever in that state.

When run, one of two things will happen: either the map will evolve into a number of isolated domains separated by gaps, or else it will percolate—end up with all cells set to 1. Whether this happens is highly sensitive to the initial density of one cells. Below a critical density, the map will almost never percolate, while above it the map will almost always end up all ones. Near the critical density, whether or not the map percolates depends upon details of its initial random configuration. The critical density depends upon the neighbourhood size, and is around 4.5% ones for the four neighbour case and 7.5% for eight neighbours.

Colour is used to trace the waves of percolation, but plays no part in the operation of the rule. Initially set cells are displayed in white and do not change. Newly set cells in each generation are in green, and cells age over a colour gradient from red to dark blue. You can see the percolation front proceeding from each nucleation site as a green wave leaving the rainbow behind it, with the oldest cells in dark blue. If the map completely percolates, the end state will be the white initially set cells on a background of dark blue.

When you run the rule, try stopping it after it has reached a steady state and then use the “Random” button in the Pattern section and its Density field to load patterns with different densities and explore how they behave. The rule is initially set for the eight cell Moore neighbourhood. You can change this by editing the rule program, changing the setting of the vonnN variable, then pressing “Generate” to update the rule.

Run the Bootperc rule in CelLab

Posted at 22:27 Permalink

Monday, June 12, 2017

Reading List: Kindling

Shute, Nevil. Kindling. New York: Vintage Books, [1938, 1951] 2010. ISBN 978-0-307-47417-9.
It is the depth of the great depression, and yet business is booming at Warren Sons and Mortimer, merchant bankers, in the City of London. Henry Warren, descendant of the founder of the bank in 1750 and managing director, has never been busier. Despite the general contraction in the economy, firms failing, unemployment hitting record after record, and a collapse in international trade, his bank, which specialises in floating securities in London for foreign governments, has more deals pending than he can handle as those governments seek to raise funds to bolster their tottering economies. A typical week might see him in Holland, Sweden, Finland, Estonia, Germany, Holland again, and back to England in time for a Friday entirely on the telephone and in conferences at his office. It is an exhausting routine and, truth be told, he was sufficiently wealthy not to have to work if he didn't wish to, but it was the Warren and Mortimer bank and he was this generation's Warren in charge, and that's what Warrens did.

But in the few moments he had to reflect upon his life, there was little joy in it. He worked so hard he rarely saw others outside work except for his wife Elise's social engagements, which he found tedious and her circle of friends annoying and superficial, but endured out of a sense of duty. He suspected Elise might be cheating on him with the suave but thoroughly distasteful Prince Ali Said, and he wasn't the only one: there were whispers and snickers behind his back in the City. He had no real friends; only business associates, and with no children, no legacy to work for other than the firm. Sleep came only with sleeping pills. He knew his health was declining from stress, sleep deprivation, and lack of exercise.

After confirming his wife's affair, he offers her an ultimatum: move away from London to a quiet life in the country or put an end to the marriage. Independently wealthy, she immediately opts for the latter and leaves him to work out the details. What is he now to do with his life? He informs the servants he is closing the house and offers them generous severance, tells the bank he is taking an indefinite leave to travel and recuperate, and tells his chauffeur to prepare for a long trip, details to come. They depart in the car, northbound. He vows to walk twenty miles a day, every day, until he recovers his health, mental equilibrium, and ability to sleep.

After a few days walking, eating and sleeping at inns and guest houses in the northlands, he collapses in excruciating pain by the side of the road. A passing lorry driver takes him to a small hospital in the town of Sharples. Barely conscious, a surgeon diagnoses him with an intestinal obstruction and says an operation will be necessary. He is wheeled to the operating theatre. The hospital staff speculates on who he might be: he has no wallet or other identification. “Probably one of the men on the road, seeking work in the South”, they guess.

As he begins his recovery in the hospital Warren decides not to complicate matters with regard to his identity: “He had no desire to be a merchant banker in a ward of labourers.” He confirmed their assumption, adding that he was a bank clerk recently returned from America where there was no work at all, in hopes of finding something in the home country. He recalls that Sharples had been known for the Barlow shipyard, once a prosperous enterprise, which closed five years ago, taking down the plate mill and other enterprises it and its workers supported. There was little work in Sharples, and most of the population was on relief. He begins to notice that patients in the ward seem to be dying at an inordinate rate, of maladies not normally thought life-threatening. He asks Miss McMahon, the hospital's Almoner, who tells him it's the poor nutrition affordable on relief, plus the lack of hope and sense of purpose in life due to long unemployment that's responsible. As he recovers and begins to take walks in the vicinity, he sees the boarded up stores, and the derelict shipyard and rolling mill. Curious, he arranges to tour them. When people speak to him of their hope the economy will recover and the yard re-open, he is grimly realistic and candid: with the equipment sold off or in ruins and the skilled workforce dispersed, how would it win an order even if there were any orders to be had?

As he is heading back to London to pick up his old life, feeling better mentally and physically than he had for years, ideas and numbers begin to swim in his mind.

It was impossible. Nobody, in this time of depression, could find an order for a single ship…—let alone a flock of them.

There was the staff. … He could probably get them together again at a twenty per cent rise in salary—if they were any good. But how was he to judge of that?

The whole thing was impossible, sheer madness to attempt. He must be sensible, and put it from his mind.

It would be damn good fun…

Three weeks later, acting through a solicitor to conceal his identity, Mr. Henry Warren, merchant banker of the City, became the owner of Barlows' Yard, purchasing it outright for the sum of £5500. Thus begins one of the most entertaining, realistic, and heartwarming tales of entrepreneurship (or perhaps “rentrepreneurship”) I have ever read. The fact that the author was himself founder and director of an aircraft manufacturing company during the depression, and well aware of the need to make payroll every week, get orders to keep the doors open even if they didn't make much business sense, and do whatever it takes so that the business can survive and meet its obligations to its customers, investors, employees, suppliers, and creditors, contributes to the authenticity of the tale. (See his autobiography, Slide Rule [July 2011], for details of his career.)

Back in his office at the bank, there is the matter of the oil deal in Laevatia. After defaulting on their last loan, the Balkan country is viewed as a laughingstock and pariah in the City, but Warren has an idea. If they are to develop oil in the country, they will need to ship it, and how better to ship it than in their own ships, built in Britain on advantageous terms? Before long, he's off to the Balkans to do a deal in the Balkan manner (involving bejewelled umbrellas, cases of Worcestershire sauce, losing to the Treasury minister in the local card game at a dive in the capital, and working out a deal where the dividends on the joint stock oil company will be secured by profits from the national railway. And, there's the matter of the ships, which will be contracted for by Warren's bank.

Then it's back to London to pitch the deal. Warren's reputation counts for a great deal in the City, and the preference shares are placed. That done, the Hawside Ship and Engineering Company Ltd. is registered with cut-out directors, and the process of awarding the contract for the tankers to it is undertaken. As Warren explains to Miss McMahon, who he has begun to see more frequently, once the order is in hand, it can be used to float shares in the company to fund the equipment and staff to build the ships. At least if the prospectus is sufficiently optimistic—perhaps too optimistic….

Order in hand, life begins to return to Sharples. First a few workers, then dozens, then hundreds. The welcome sound of riveting and welding begins to issue from the yard. A few boarded-up shops re-open, and then more. Then another order for a ship came in, thanks to arm-twisting by one of the yard's directors. With talk of Britain re-arming, there was the prospect of Admiralty business. There was still only one newspaper a week in Sharples, brought in from Newcastle and sold to readers interested in the football news. On one of his more frequent visits to the town, yard, and Miss McMahon, Warren sees the headline: “Revolution in Laevatia”. “This is a very bad one,” Warren says. “I don't know what this is going to mean.”

But, one suspects, he did. As anybody who has been in the senior management of a publicly-traded company is well aware, what happens next is well-scripted: the shareholder suit by a small investor, the press pile-on, the back-turning by the financial community, the securities investigation, the indictment, and, eventually, the slammer. Warren understands this, and works diligently to ensure the Yard survives. There is a deep mine of wisdom here for anybody facing a bad patch.

“You must make this first year's accounts as bad as they ever can be,” he said. “You've got a marvellous opportunity to do so now, one that you'll never have again. You must examine every contract that you've got, with Jennings, and Grierson must tell the auditors that every contract will be carried out at a loss. He'll probably be right, of course—but he must pile it on. You've got to make reserves this year against every possible contingency, probable or improbable.”

“Pile everything into this year's loss, including a lot that really ought not to be there. If you do that, next year you'll be bound to show a profit, and the year after, if you've done it properly this year. Then as soon as you're showing profits and a decent show of orders in hand, get rid of this year's losses by writing down your capital, pay a dividend, and make another issue to replace the capital.”

Sage advice—I've been there. We had cash in the till, so we were able to do a stock buy-back at the bottom, but the principle is the same.

Having been brought back to life by almost dying in small town hospital, Warren is rejuvenated by his time in gaol. In November 1937, he is released and returns to Sharples where, amidst evidence of prosperity everywhere he approaches the Yard, to see a plaque on the wall with his face in profile: “HENRY WARREN — 1934 — HE GAVE US WORK”. Then he was off to see Miss McMahon.

The only print edition currently available new is a very expensive hardcover. Used paperbacks are readily available: check under both Kindling and the original British title, Ruined City. I have linked to the Kindle edition above.

Posted at 00:35 Permalink

Sunday, June 11, 2017

Cellular Automata Laboratory: Forest Fire Model

I have just added a new sample rule to Cellular Automata Laboratory (CelLab): Forest, a model of forest fire propagation originally published by Drossel and Schwabl in 1992.

Cells in the map represent either a tree or open ground. Lightning strikes cells at random with a probability f (default 0.00002) on each generation. If lightning strikes open ground, nothing happens, but if it strikes a tree, on the next generation the tree will be on fire. A tree on fire becomes open ground in the next generation. A tree catches fire if any of its eight neighbours is on fire. New trees appear in open ground cells with a probability p (default 0.002).

When the density of trees is low, most lightning strikes empty ground or burns only one or a few trees. As the density of fuel grows over time, the forest becomes susceptible to cataclysmic wildfires which burn large regions. Eventually, you will see lots of small fires and a few very large conflagrations.

The behaviour of the model is highly sensitive to the ratio of the parameters f and p, which you can adjust by editing the top of the evaluator function. Counter-intuitively, reducing the number of lightning strikes increases the number of large fires because it allows fuel to build up which permits the rare fire, once started, to propagate widely. This phenomenon is observed in forestry and is managed by controlled burns.

An age counter is used to display trees in sixteen intensities of green based upon their age in generations, and to make flame fronts fade after they have passed. This is simply to make the display easier to understand; it plays no part in the behavior of the rule.

Run the Forest rule in CelLab

Posted at 13:48 Permalink

Thursday, June 8, 2017

The Time Machine by H. G. Wells: New Web Edition

I have just posted an updated version of the Web edition of H. G. Wells' classic 1895 novel, The Time Machine. This novel (actually, at around 33,000 words, it would be classed as a long novella by contemporary publishers) was originally posted at Fourmilab in 2002. The new edition updates the document to contemporary Web standards (XHTML 1.0 Strict and CSS 3), and uses Unicode text entities for typographic elements such as quotes, dashes, and ellipses.

As I note in the contents page, there were many editions of this work published between 1895 and the last version revised by Wells in 1935. I have based this edition upon the latter work. If you find any errors, please send feedback, but bear in mind that if it's a quibble with words on which the author signed off, I'll go with the latter. Please don't complain about the quote marks. The 1935 edition was published in Britain. British publishers use ‘single quotes’ for the outer level of quotations and “double quotes” for quotations nested within them, while U.S. publishers use exactly the opposite convention. In this edition, I have used quote marks as the author wrote them and his publisher printed them. Because of the story's unusual narrative structure, the main long quotation is carried over from chapter to chapter without a closing quote until the Time Traveller pauses his story in chapter 7 and concludes it in chapter 12: this is as it was in the original.

This is a fine yarn, easily read in one or two sittings, which has much to say about the consequences of eliminating risk and challenges from the lives of people in developed societies. It is much better than the two Hollywood movies loosely based upon it.

Posted at 23:46 Permalink

Tuesday, June 6, 2017

Cellular Automata Laboratory: WebCA Released

In the first major update since 1997, a completely new version of Cellular Automata Laboratory (CelLab) is now available. The cellular automata simulators which previously ran under MS-DOS and Microsoft Windows (and which have ceased to work on recent releases of Windows thanks to Microsoft's trademark strategic incompatibility) and been replaced by a new simulator, WebCA, which is written in JavaScript and runs entirely within the user's browser, using the HTML5 canvas element and associated JavaScript support to display the results of the simulation. Rules, which were previously defined by external programs in languages such as Java, Pascal, C, or Basic, are now defined in JavaScript and compiled directly by the simulator: no external programming environment is required. Custom evaluators, formerly written in assembly language or as a Windows DLL, are now also defined in JavaScript

Many new sample rules have been added, illustrating applications such as billiard ball computing, ecological modeling, emulation of Boolean logic elements, simulation of a spin Ising system, Margolus block rule evaluation, and computational fluid dynamics (the latter demonstrating a cellular automaton with continuous-valued cell state). Source code for all rules and evaluators and the pattern and colour palette files they use are available in a new CelLab Development Kit.

The ability to create self-running demos, or “shows” has been added, and used to build the CelLab Demo, which you can also watch (albeit at lower resolution) on YouTube. A number of other demos are included, which are available on a YouTube playlist.

The manual has been extensively revised, removing the information on the MS-DOS and Windows simulators and documenting WebCA and the new rules and evaluators. Instructions for writing rule definitions and custom evaluators in JavaScript are included. The manual has been updated to current Web standards and typography, and should be easier on the eye.

In order to run WebCA, you need a browser which supports HTML5 canvas and the JavaScript features it requires. Browsers differ substantially in the efficiency of their JavaScript implementations. I have found that the Chrome and Brave browsers provide the best performance, with Firefox and Safari substantially slower but sufficient to run all but the most complicated evaluators.

The links below provide access to the new release and its components.

Posted at 21:04 Permalink

Monday, June 5, 2017

New: Terranova Planet Maker

Since 1995, Terranova has been delivering a planet of the day to visitors on the Web. Now, users with a modern Web browser that supports HTML5 canvas and JavaScript can use Terranova Planet Maker to make their own planets, plus images of cloudy skies and star fields, any time they wish, right within the browser (you don't need to be connected to a server—all computation is done locally). The algorithm used to produce the images is identical to that used by Terranova and can either use randomly-selected parameters or be controlled at a fine-grained level by user settings. Images can be saved to your local machine through the right-click menu available on almost all browsers.

Yes. we're really doing a million-point two-dimensional inverse fast Fourier transform in JavaScript running inside the browser. Progress in JavaScript implementations has been such that on a fast machine and modern browser, you'll hardly notice the generation time.

Posted at 20:53 Permalink