Fourmilog: None Dare Call It Reason

Reading List: Destination Moon

Saturday, September 27, 2014 00:37

Byers, Bruce K. Destination Moon. Washington: National Aeronautics and Space Administration, 1977. NASA TM X-3487.
In the mid 1960s, the U.S. Apollo lunar landing program was at the peak of its budget commitment and technical development. The mission mode had already been chosen and development of the flight hardware was well underway, along with the ground infrastructure required to test and launch it and the global network required to track missions in flight. One nettlesome problem remained. The design of the lunar module made assumptions about the properties of the lunar surface upon which it would alight. If the landing zone had boulders which were too large, craters sufficiently deep and common that the landing legs could not avoid, or slopes too steep to avoid an upset on landing or tipping over afterward, lunar landing missions would all be aborted by the crew when they reached decision height, judging there was no place they could set down safely. Even if all the crews returned safely without having landed, this would be an ignominious end to the ambitions of Project Apollo.

What was needed in order to identify safe landing zones was high-resolution imagery of the Moon. The most capable Earth-based telescopes, operating through Earth's turbulent and often murky atmosphere, produced images which resolved objects at best a hundred times larger that those which could upset a lunar landing mission. What was required was a large area, high resolution mapping of the Moon and survey of potential landing zones, which could only be done, given the technology of the 1960s, by going there, taking pictures, and returning them to Earth. So was born the Lunar Orbiter program, which in 1966 and 1967 sent lightweight photographic reconnaissance satellites into lunar orbit, providing both the close-up imagery needed to select landing sites for the Apollo missions, but also mapping imagery which covered 99% of the near side of the Moon and 85% of the far side, In fact, Lunar Orbiter provided global imagery of the Moon far more complete than that which would be available for the Earth many years thereafter.

Accomplishing this goal with the technology of the 1960s was no small feat. Electronic imaging amounted to analogue television, which, at the altitude of a lunar orbit, wouldn't produce images any better than telescopes on Earth. The first spy satellites were struggling to return film from Earth orbit, and returning film from the Moon was completely impossible given the mass budget of the launchers available. After a fierce competition, NASA contracted with Boeing to build the Lunar Orbiter, designed to fit on NASA's workhorse Atlas-Agena launcher, which seriously constrained its mass. Boeing subcontracted with Kodak to build the imaging system and RCA for the communications hardware which would relay the images back to Earth and allow the spacecraft to be controlled from the ground.

The images were acquired by a process which may seem absurd to those accustomed to present-day digital technologies but which seemed miraculous in its day. In lunar orbit, the spacecraft would aim its cameras (it had two: a mapping camera which produced overlapping wide-angle views and a high-resolution camera that photographed clips of each frame with a resolution of about one metre) at the Moon and take a series of photos. Because the film used had a very low light sensitivity (ASA [now ISO] 1.6), on low-altitude imaging passes the film would have to be moved to compensate for the motion of the spacecraft to avoid blurring. (The low light sensitivity of the film was due to its very high spatial resolution, but also reduced its likelihood of being fogged by exposure to cosmic rays or energetic particles from solar flares.)

After being exposed, the film would subsequently be processed on-board by putting it in contact with a band containing developer and fixer, and then the resulting negative would be read back for transmission to Earth by scanning it with a moving point of light, measuring the transmission through the negative, and sending the measured intensity back as an analogue signal. At the receiving station, that signal would be used to modulate the intensity of a spot of light scanned across film which, when developed and assembled into images from strips, revealed the details of the Moon. The incoming analogue signal was recorded on tape to provide a backup for the film recording process, but nothing was done with the tapes at the time. More about this later….

Five Lunar Orbiter missions were launched, and although some experienced problems, all achieved their primary mission objectives. The first three missions provided all of the data required by Apollo, so the final two could be dedicated to mapping the Moon from near-polar orbits. After the completion of their primary imaging missions, Lunar Orbiters continued to measure the radiation and micrometeoroid environment near the Moon, and contributed to understanding the Moon's gravitational field, which would be important in planning later Apollo missions that would fly in very low orbits around the Moon. On August 23rd, 1966, the first Lunar Orbiter took one of the most iconic pictures of the 20th century: Earthrise from the Moon. The problems experienced by Lunar Orbiter missions and the improvisation by ground controllers to work around them set the pattern for subsequent NASA robotic missions, with their versatile, reconfigurable flight hardware and fine-grained control from the ground.

You might think the story of Lunar Orbiter a footnote to space exploration history which has scrolled off the screen with subsequent Apollo lunar landings and high-resolution lunar mapping by missions such as Clementine and the Lunar Reconnaissance Orbiter, but that fails to take into account the exploits of 21st century space data archaeologists. Recall that I said that all of the image data from Lunar Orbiter missions was recorded on analogue tapes. These tapes contained about 10 bits of dynamic range, as opposed to the 8 bits which were preserved by the optical recording process used in receiving the images during the missions. This, combined with contemporary image processing techniques, makes for breathtaking images recorded almost half a century ago, but never seen before. Here are a document and video which record the exploits of the Lunar Orbiter Image Recovery Project (LOIRP). Please visit the LOIRP Web site for more restored images and details of the process of restoration.

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Reading List: My Sweet Satan

Tuesday, September 23, 2014 01:14

Cawdron, Peter. My Sweet Satan. Seattle: Amazon Digital Services, 2014. ASIN B00NBA6Y1A.
Here the author adds yet another imaginative tale of first contact to his growing list of novels in that genre, a puzzle story which the viewpoint character must figure out having lost memories of her entire adult life. After a botched attempt at reanimation from cryo-sleep, Jasmine Holden finds herself with no memories of her life after the age of nineteen. And yet, here she is, on board Copernicus, in the Saturn system, closing in on the distant retrograde moon Bestla which, when approached by a probe from Earth, sent back an audio transmission to its planet of origin which was mostly gibberish but contained the chilling words: “My sweet Satan. I want to live and die for you, my glorious Satan!”. A follow-up unmanned probe to Bestla is destroyed as it approaches, and the Copernicus is dispatched to make a cautious investigation of what appears to be an alien probe with a disturbing theological predisposition.

Back on Earth, sentiment has swung back and forth about the merits of exploring Bestla and fears of provoking an alien presence in the solar system which, by its very capability of interstellar travel, must be far in advance of Earthly technology. Jasmine, a key member of the science team, suddenly finds herself mentally a 19 year old girl far from her home, and confronted both by an unknown alien presence but also conflict among her crew members, who interpret the imperatives of the mission in different ways.

She finds the ship's computer, an early stage artificial intelligence, the one being in which she can confide, and the only one who comprehends her predicament and is willing to talk her through procedures she learned by heart in her training but have been lost to an amnesia she feels compelled to conceal from human members of the crew.

As the ship approaches Bestla, conflict erupts among the crew, and Jasmine must sort out what is really going on and choose sides without any recollections of her earlier interactions with her crew members. In a way, this is three first contact novels in one: 19 year old Jasmine making contact with her fellow crew members about which she remembers nothing, the Copernicus and whatever is on Bestla, and a third contact about which I cannot say anything without spoiling the story.

This is a cracking good first contact novel which, just when you're nearing the end and beginning to worry “Where's the sense of wonder?” delivers everything you'd hoped for and more.

I read a pre-publication manuscript edition which the author kindly shared with me.

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Reading List: Superintelligence

Friday, September 19, 2014 23:11

Bostrom, Nick. Superintelligence. Oxford: Oxford University Press, 2014. ISBN 978-0-19-967811-2.
Absent the emergence of some physical constraint which causes the exponential growth of computing power at constant cost to cease, some form of economic or societal collapse which brings an end to research and development of advanced computing hardware and software, or a decision, whether bottom-up or top-down, to deliberately relinquish such technologies, it is probable that within the 21st century there will emerge artificially-constructed systems which are more intelligent (measured in a variety of ways) than any human being who has ever lived and, given the superior ability of such systems to improve themselves, may rapidly advance to superiority over all human society taken as a whole. This “intelligence explosion” may occur in so short a time (seconds to hours) that human society will have no time to adapt to its presence or interfere with its emergence. This challenging and occasionally difficult book, written by a philosopher who has explored these issues in depth, argues that the emergence of superintelligence will pose the greatest human-caused existential threat to our species so far in its existence, and perhaps in all time.

Let us consider what superintelligence may mean. The history of machines designed by humans is that they rapidly surpass their biological predecessors to a large degree. Biology never produced something like a steam engine, a locomotive, or an airliner. It is similarly likely that once the intellectual and technological leap to constructing artificially intelligent systems is made, these systems will surpass human capabilities to an extent greater than those of a Boeing 747 exceed those of a hawk. The gap between the cognitive power of a human, or all humanity combined, and the first mature superintelligence may be as great as that between brewer's yeast and humans. We'd better be sure of the intentions and benevolence of that intelligence before handing over the keys to our future to it.

Because when we speak of the future, that future isn't just what we can envision over a few centuries on this planet, but the entire “cosmic endowment” of humanity. It is entirely plausible that we are members of the only intelligent species in the galaxy, and possibly in the entire visible universe. (If we weren't, there would be abundant and visible evidence of cosmic engineering by those more advanced that we.) Thus our cosmic endowment may be the entire galaxy, or the universe, until the end of time. What we do in the next century may determine the destiny of the universe, so it's worth some reflection to get it right.

As an example of how easy it is to choose unwisely, let me expand upon an example given by the author. There are extremely difficult and subtle questions about what the motivations of a superintelligence might be, how the possession of such power might change it, and the prospects for we, its creator, to constrain it to behave in a way we consider consistent with our own values. But for the moment, let's ignore all of those problems and assume we can specify the motivation of an artificially intelligent agent we create and that it will remain faithful to that motivation for all time. Now suppose a paper clip factory has installed a high-end computing system to handle its design tasks, automate manufacturing, manage acquisition and distribution of its products, and otherwise obtain an advantage over its competitors. This system, with connectivity to the global Internet, makes the leap to superintelligence before any other system (since it understands that superintelligence will enable it to better achieve the goals set for it). Overnight, it replicates itself all around the world, manipulates financial markets to obtain resources for itself, and deploys them to carry out its mission. The mission?—to maximise the number of paper clips produced in its future light cone.

“Clippy”, if I may address it so informally, will rapidly discover that most of the raw materials it requires in the near future are locked in the core of the Earth, and can be liberated by disassembling the planet by self-replicating nanotechnological machines. This will cause the extinction of its creators and all other biological species on Earth, but then they were just consuming energy and material resources which could better be deployed for making paper clips. Soon other planets in the solar system would be similarly disassembled, and self-reproducing probes dispatched on missions to other stars, there to make paper clips and spawn other probes to more stars and eventually other galaxies. Eventually, the entire visible universe would be turned into paper clips, all because the original factory manager didn't hire a philosopher to work out the ultimate consequences of the final goal programmed into his factory automation system.

This is a light-hearted example, but if you happen to observe a void in a galaxy whose spectrum resembles that of paper clips, be very worried.

One of the reasons to believe that we will have to confront superintelligence is that there are multiple roads to achieving it, largely independent of one another. Artificial general intelligence (human-level intelligence in as many domains as humans exhibit intelligence today, and not constrained to limited tasks such as playing chess or driving a car) may simply await the discovery of a clever software method which could run on existing computers or networks. Or, it might emerge as networks store more and more data about the real world and have access to accumulated human knowledge. Or, we may build “neuromorphic“ systems whose hardware operates in ways similar to the components of human brains, but at electronic, not biologically-limited speeds. Or, we may be able to scan an entire human brain and emulate it, even without understanding how it works in detail, either on neuromorphic or a more conventional computing architecture. Finally, by identifying the genetic components of human intelligence, we may be able to manipulate the human germ line, modify the genetic code of embryos, or select among mass-produced embryos those with the greatest predisposition toward intelligence. All of these approaches may be pursued in parallel, and progress in one may advance others.

At some point, the emergence of superintelligence calls into the question the economic rationale for a large human population. In 1915, there were about 26 million horses in the U.S. By the early 1950s, only 2 million remained. Perhaps the AIs will have a nostalgic attachment to those who created them, as humans had for the animals who bore their burdens for millennia. But on the other hand, maybe they won't.

As an engineer, I usually don't have much use for philosophers, who are given to long gassy prose devoid of specifics and for spouting complicated indirect arguments which don't seem to be independently testable (“What if we asked the AI to determine its own goals, based on its understanding of what we would ask it to do if only we were as intelligent as it and thus able to better comprehend what we really want?”). These are interesting concepts, but would you want to bet the destiny of the universe on them? The latter half of the book is full of such fuzzy speculation, which I doubt is likely to result in clear policy choices before we're faced with the emergence of an artificial intelligence, after which, if they're wrong, it will be too late.

That said, this book is a welcome antidote to wildly optimistic views of the emergence of artificial intelligence which blithely assume it will be our dutiful servant rather than a fearful master. Some readers may assume that an artificial intelligence will be something like a present-day computer or search engine, and not be self-aware and have its own agenda and powerful wiles to advance it, based upon a knowledge of humans far beyond what any single human brain can encompass. Unless you believe there is some kind of intellectual élan vital inherent in biological substrates which is absent in their equivalents based on other hardware (which just seems silly to me—like arguing there's something special about a horse which can't be accomplished better by a truck), the mature artificial intelligence will be the superior in every way to its human creators, so in-depth ratiocination about how it will regard and treat us is in order before we find ourselves faced with the reality of dealing with our successor.

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Reading List: The South Pole

Friday, September 5, 2014 15:17

Amundsen, Roald. The South Pole. New York: Cooper Square Press, [1913] 2001. ISBN 978-0-8154-1127-7.
In modern warfare, it has been observed that “generals win battles, but logisticians win wars.” So it is with planning an exploration mission to a remote destination where no human has ever set foot, and the truths are as valid for polar exploration in the early 20th century as they will be for missions to Mars in the 21st. On December 14th, 1911, Roald Amundsen and his five-man southern party reached the South Pole after a trek from the camp on the Ross Ice Shelf where they had passed the previous southern winter, preparing for an assault on the pole as early as the weather would permit. By over-wintering, they would be able to depart southward well before a ship would be able to land an expedition, since a ship would have to wait until the sea ice dispersed sufficiently to make a landing.

Amundsen's plan was built around what space mission architects call “in-situ resource utilisation” and “depots”, as well as “propulsion staging”. This allowed for a very lightweight push to the pole, both in terms of the amount of supplies which had to be landed by their ship, the Fram, and in the size of the polar party and the loading of their sledges. Upon arriving in Antarctica, Amundsen's party immediately began to hunt the abundant seals near the coast. More than two hundred seals were killed, processed, and stored for later use. (Since the temperature on the Ross Ice Shelf and the Antarctic interior never rises above freezing, the seal meat would keep indefinitely.) Then parties were sent out in the months remaining before the arrival of winter in 1911 to establish depots at every degree of latitude between the base camp and 82° south. These depots contained caches of seal meat for the men and dogs and kerosene for melting snow for water and cooking food. The depot-laying journeys familiarised the explorers with driving teams of dogs and operating in the Antarctic environment.

Amundsen had chosen dogs to pull his sledges. While his rival to be first at the pole, Robert Falcon Scott, experimented with pulling sledges by ponies, motorised sledges, and man-hauling, Amundsen relied upon the experience of indigenous people in Arctic environments that dogs were the best solution. Dogs reproduced and matured sufficiently quickly that attrition could be made up by puppies born during the expedition, they could be fed on seal meat, which could be obtained locally, and if a dog team were to fall into a crevasse (as was inevitable when crossing uncharted terrain), the dogs could be hauled out, no worse for wear, by the drivers of other sledges. For ponies and motorised sledges, this was not the case.

Further, Amundsen adopted a strategy which can best be described as “dog eat dog”. On the journey to the pole, he started with 52 dogs. Seven of these had died from exhaustion or other causes before the ascent to the polar plateau. (Dogs who died were butchered and fed to the other dogs. Greenland sled dogs, being only slightly removed from wolves, had no hesitation in devouring their erstwhile comrades.) Once reaching the plateau, 27 dogs were slaughtered, their meat divided between the surviving dogs and the five men. Only 18 dogs would proceed to the pole. Dog carcasses were cached for use on the return journey.

Beyond the depots, the polar party had to carry everything required for the trip. but knowing the depots would be available for the return allowed them to travel lightly. After reaching the pole, they remained for three days to verify their position, send out parties to ensure they had encircled the pole's position, and built a cairn to commemorate their achievement. Amundsen left a letter which he requested Captain Scott deliver to King Haakon VII of Norway should Amundsen's party be lost on its return to base. (Sadly, that was the fate which awaited Scott, who arrived at the pole on January 17th, 1912, only to find the Amundsen expedition's cairn there.)

This book is Roald Amundsen's contemporary memoir of the expedition. Originally published in two volumes, the present work includes both. Appendices describe the ship, the Fram, and scientific investigations in meteorology, geology, astronomy, and oceanography conducted during the expedition. Amundsen's account is as matter-of-fact as the memoirs of some astronauts, but a wry humour comes through when discussing dealing with sled dogs who have will of their own and also the foibles of humans cooped up in a small cabin in an alien environment during a night which lasts for months. He evinces great respect for his colleagues and competitors in polar exploration, particularly Scott and Shackleton, and worries whether his own approach to reaching the pole would be proved superior to theirs. At the time the book was published, the tragic fate of Scott's expedition was not known.

Today, we might not think of polar exploration as science, but a century ago it was as central to the scientific endeavour as robotic exploration of Mars is today. Here was an entire continent, known only in sketchy detail around its coast, with only a few expeditions into the interior. When Amundsen's party set out on their march to the pole, they had no idea whether they would encounter mountain ranges along the way and, if so, whether they could find a way over or around them. They took careful geographic and meteorological observations along their trek (as well as oceanographical measurements on the trip to Antarctica and back), and these provided some of the first data points toward understanding weather in the southern hemisphere.

In Norway, Amundsen was hailed as a hero. But it is clear from this narrative he never considered himself such. He wrote:

I may say that this is the greatest factor—the way in which the expedition is equipped—the way in which every difficulty is foreseen, and precautions taken for meeting or avoiding it. Victory awaits him who has everything in order—luck, people call it. Defeat is certain for him who has neglected to take the necessary precautions in time; this is called bad luck.

This work is in the public domain, and there are numerous editions of it available, in print and in electronic form, many from independent publishers. The independent publishers, for the most part, did not distinguish themselves in their respect for this work. Many of their editions were produced by running an optical character recognition program over a print copy of the book, then putting it together with minimal copy-editing. Some (including the one I was foolish enough to buy) elide all of the diagrams, maps, and charts from the original book, which renders parts of the text incomprehensible. The paperback edition cited above, while expensive, is a facsimile edition of the original 1913 two volume English translation of Amundsen's original work, including all of the illustrations. I know of no presently-available electronic edition which has comparable quality and includes all of the material in the original book. Be careful—if you follow the link to the paperback edition, you'll see a Kindle edition listed, but this is from a different publisher and is rife with errors and includes none of the illustrations. I made the mistake of buying it, assuming it was the same as the highly-praised paperback. It isn't; don't be fooled.

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Reading List: The Man Who Changed Everything

Friday, August 29, 2014 23:45

Mahon, Basil. The Man Who Changed Everything. Chichester, UK: John Wiley & Sons, 2003. ISBN 978-0-470-86171-4.
In the 19th century, science in general and physics in particular grew up, assuming their modern form which is still recognisable today. At the start of the century, the word “scientist” was not yet in use, and the natural philosophers of the time were often amateurs. University research in the sciences, particularly in Britain, was rare. Those working in the sciences were often occupied by cataloguing natural phenomena, and apart from Newton's monumental achievements, few people focussed on discovering mathematical laws to explain the new physical phenomena which were being discovered such as electricity and magnetism.

One person, James Clerk Maxwell, was largely responsible for creating the way modern science is done and the way we think about theories of physics, while simultaneously restoring Britain's standing in physics compared to work on the Continent, and he created an institution which would continue to do important work from the time of his early death until the present day. While every physicist and electrical engineer knows of Maxwell and his work, he is largely unknown to the general public, and even those who are aware of his seminal work in electromagnetism may be unaware of the extent his footprints are found all over the edifice of 19th century physics.

Maxwell was born in 1831 to a Scottish lawyer, John Clerk, and his wife Frances Cay. Clerk subsequently inherited a country estate, and added “Maxwell” to his name in honour of the noble relatives from whom he inherited it. His son's first name, then was “James” and his surname “Clerk Maxwell”: this is why his full name is always used instead of “James Maxwell”. From childhood, James was curious about everything he encountered, and instead of asking “Why?” over and over like many children, he drove his parents to distraction with “What's the go o' that?”. His father did not consider science a suitable occupation for his son and tried to direct him toward the law, but James's curiosity did not extend to legal tomes and he concentrated on topics that interested him. He published his first scientific paper, on curves with more than two foci, at the age of 14. He pursued his scientific education first at the University of Edinburgh and later at Cambridge, where he graduated in 1854 with a degree in mathematics. He came in second in the prestigious Tripos examination, earning the title of Second Wrangler.

Maxwell was now free to begin his independent research, and he turned to the problem of human colour vision. It had been established that colour vision worked by detecting the mixture of three primary colours, but Maxwell was the first to discover that these primaries were red, green, and blue, and that by mixing them in the correct proportion, white would be produced. This was a matter to which Maxwell would return repeatedly during his life.

In 1856 he accepted an appointment as a full professor and department head at Marischal College, in Aberdeen Scotland. In 1857, the topic for the prestigious Adams Prize was the nature of the rings of Saturn. Maxwell's submission was a tour de force which proved that the rings could not be either solid nor a liquid, and hence had to be made of an enormous number of individually orbiting bodies. Maxwell was awarded the prize, the significance of which was magnified by the fact that his was the only submission: all of the others who aspired to solve the problem had abandoned it as too difficult.

Maxwell's next post was at King's College London, where he investigated the properties of gases and strengthened the evidence for the molecular theory of gases. It was here that he first undertook to explain the relationship between electricity and magnetism which had been discovered by Michael Faraday. Working in the old style of physics, he constructed an intricate mechanical thought experiment model which might explain the lines of force that Faraday had introduced but which many scientists thought were mystical mumbo-jumbo. Maxwell believed the alternative of action at a distance without any intermediate mechanism was wrong, and was able, with his model, to explain the phenomenon of rotation of the plane of polarisation of light by a magnetic field, which had been discovered by Faraday. While at King's College, to demonstrate his theory of colour vision, he took and displayed the first colour photograph.

Maxwell's greatest scientific achievement was done while living the life of a country gentleman at his estate, Glenair. In his textbook, A Treatise on Electricity and Magnetism, he presented his famous equations which showed that electricity and magnetism were two aspects of the same phenomenon. This was the first of the great unifications of physical laws which have continued to the present day. But that isn't all they showed. The speed of light appeared as a conversion factor between the units of electricity and magnetism, and the equations allowed solutions of waves oscillating between an electric and magnetic field which could propagate through empty space at the speed of light. It was compelling to deduce that light was just such an electromagnetic wave, and that waves of other frequencies outside the visual range must exist. Thus was laid the foundation of wireless communication, X-rays, and gamma rays. The speed of light is a constant in Maxwell's equations, not depending upon the motion of the observer. This appears to conflict with Newton's laws of mechanics, and it was not until Einstein's 1905 paper on special relativity that the mystery would be resolved. In essence, faced with a dispute between Newton and Maxwell, Einstein decided to bet on Maxwell, and he chose wisely. Finally, when you look at Maxwell's equations (in their modern form, using the notation of vector calculus), they appear lopsided. While they unify electricity and magnetism, the symmetry is imperfect in that while a moving electric charge generates a magnetic field, there is no magnetic charge which, when moved, generates an electric field. Such a charge would be a magnetic monopole, and despite extensive experimental searches, none has ever been found. The existence of monopoles would make Maxwell's equations even more beautiful, but sometimes nature doesn't care about that. By all evidence to date, Maxwell got it right.

In 1871 Maxwell came out of retirement to accept a professorship at Cambridge and found the Cavendish Laboratory, which would focus on experimental science and elevate Cambridge to world-class status in the field. To date, 29 Nobel Prizes have been awarded for work done at the Cavendish.

Maxwell's theoretical and experimental work on heat and gases revealed discrepancies which were not explained until the development of quantum theory in the 20th century. His suggestion of Maxwell's demon posed a deep puzzle in the foundations of thermodynamics which eventually, a century later, showed the deep connections between information theory and statistical mechanics. His practical work on automatic governors for steam engines foreshadowed what we now call control theory. He played a key part in the development of the units we use for electrical quantities.

By all accounts Maxwell was a modest, generous, and well-mannered man. He wrote whimsical poetry, discussed a multitude of topics (although he had little interest in politics), was an enthusiastic horseman and athlete (he would swim in the sea off Scotland in the winter), and was happily married, with his wife Katherine an active participant in his experiments. All his life, he supported general education in science, founding a working men's college in Cambridge and lecturing at such colleges throughout his career.

Maxwell lived only 48 years—he died in 1879 of the same cancer which had killed his mother when he was only eight years old. When he fell ill, he was engaged in a variety of research while presiding at the Cavendish Laboratory. We shall never know what he might have done had he been granted another two decades.

Apart from the significant achievements Maxwell made in a wide variety of fields, he changed the way physicists look at, describe, and think about natural phenomena. After using a mental model to explore electromagnetism, he discarded it in favour of a mathematical description of its behaviour. There is no theory behind Maxwell's equations: the equations are the theory. To the extent they produce the correct results when experimental conditions are plugged in, and predict new phenomena which are subsequently confirmed by experiment, they are valuable. If they err, they should be supplanted by something more precise. But they say nothing about what is really going on—they only seek to model what happens when you do experiments. Today, we are so accustomed to working with theories of this kind: quantum mechanics, special and general relativity, and the standard model of particle physics, that we don't think much about it, but it was revolutionary in Maxwell's time. His mathematical approach, like Newton's, eschewed explanation in favour of prediction: “We have no idea how it works, but here's what will happen if you do this experiment.” This is perhaps Maxwell's greatest legacy.

This is an excellent scientific biography of Maxwell which also gives the reader a sense of the man. He was such a quintessentially normal person there aren't a lot of amusing anecdotes to relate. He loved life, loved his work, cherished his friends, and discovered the scientific foundations of the technologies which allow you to read this. In the Kindle edition, at least as read on an iPad, the text appears in a curious, spidery, almost vintage, font in which periods are difficult to distinguish from commas. Numbers sometimes have spurious spaces embedded within them, and the index cites pages in the print edition which are useless since the Kindle edition does not include real page numbers.

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