Hacking, Ian

English

Public (E-Journal, York University)

Once There Were Revolutions:Now There Are Only SurprisesIAN HACKINGWe who inhabit the comfortably extended western world may think just that.Only surprise, no more revolutions. That is the way that it will be, or so we maycomplacently imagine. Once there was the Russian Revolution, canonizing theidea of revolution for the twentieth century. Then there was the collapse of thecommunist system, which we do not call a revolution at all. Nothing but a giganticofficial surprise, with all the experts caught running for cover. It was, in fact, atruly radical change for several hundred million people. In the short term it wasmostly for the worse, in the daily lives of most citizens of the former SovietUnion. But we do not call it a revolution. The Velvet Revolution in Prague, longafter the RevolutionTranquille in Quebec. We shall soon run out of gentle adjectives.Maybe even the idea of revolution will revert back to its roots, where a revolutionis like a wheel that goes round, restoring what has been lost to its former glory-like the Glorious Revolution in England, 1688. But I am not talking about politics.It is the sciences that interest me.Once upon a time, a hundred years ago, physics had revolutions as dramaticas the events in Moscow and Saint Petersburg. Kanfs great a priori structures cametoppling down. According to the eternal vision of the sage of Konigsberg, theywere what made human understanding possible at all. The certain knowledge ofNewton's absolute space, uniform causality and determinism, Euclidean geometryitself, this was all in smithereens by 1926, a process begun with Max Planck's verymodest thoughts about black bodies in 1894. Earnest young intellectuals, them-selves living in turbulent times and places like Vienna, whose vast empire had justterminated, changed the way we think about knowledge itself. The sciences didnot gradually accumulate and acquire a fuller, rounder, and more intricate masteryof the world. They proceeded, wrenchingly, by conjecture and refutation.Certainty and permanence, the professed twin goals ofWestern science ever sincethey had been enshrined by Plato, were over, for ever. Thus Karl Popper in 1935,stating what by then seemed obvious to like minds in Berlin, Warsaw, Lvov, Rome.Once the idea had been fully digested, that is, by 1962,Thomas Kuhn changedrefutation to revolution. (In case you think I stuck in Lvov-Lemberg-now Lvivin the Ukraine-just to show off my central European geography, Kuhn began hisbook by saying that he had in many ways been anticipated by a Polish epidemiologist,Ludwik Fleck, writing in Lvov in 1935.) The Structure eifScient!fic Revolutions wasthe work of a man trained in physics who became a historian and transmuted intoa philosopher. For quite some time he was being cited as frequently as Freud andthe Bible. Whatever spark he inadvertently struck turned into a firestorm. Anobscure word used mostly by grammarians changed overnight into a cliche. (Kuhnused to have on his mantle a NewYorker cartoon, circa 1963, a Manhattan cocktailparty, pompous person addressed by buxom girl, 0, Mr. so and so, you are the firstman I have ever heard say that word 'paradigm:) Kuhn came to assert, quite explicitly,that science was impossible without revolution. Without revolution science wouldjust die, doing the same old thing better and better until it withered away. At bestPUBLIC 33 ERRATA 13it would turn into mere technology. Kuhn, like Popper and Plato before him, wasever an elitist, saying that theory, the scientific life of the mind, is what counts.Experiment, practice and technology is what engineers do. But they cannot do itwithout theory, and theory needs revolutions to feed on, or so Kuhn said.Refutation and revolution were owls of Minerva, flying, as Hegel said, atdusk, after the dust had settled and the light was dim. They really suited the timesin which Popper was young. Physics had been revolutionary in a way that it isalmost impossible for us a century later to take in. That is why I spoke less ofrelativity and the quantum theory than of the grander philosophical terms ofhuman knowledge itself, causality, space, and time. Popper and then Kuhn reflectedthat revolutionary fact-a long time ago. Now we live in a very different world.The owl sees a very stable landscape indeed.Physics in the second half of the twentieth century was an astounding successstory. For a long time the success was headlined with the work that was showcasedwith the weapon that changed statecraft, namely the atomic bomb. High energyphysics, ever more elementary particles, the first three minutes of the universe,grand unified theories of everything, plus incredibly costly accelerators justifiedby the war effort, got the headlines. The Russian un-revolution brought that warto an end. The money for vast experiments stopped, and everyone realized thatquite cheap physics had been succeeding at the same pace with the same successes.It was called solid state physics and is now called condensed matter physics.In popular science, the laser is its best known tool. Lasers do more amazing thingsin day-to-day laboratory work than any science fiction ever dreamt of, not to men-tion running your CD player on the side. Hey, we cool down individual atoms towithin trillionths of a degree of absolute zero, and they become our pals, we takefour or five of these lazy little things and do almost what we want with them. Theamazing fact is that those revolutions at the start of the twentieth century gotthings just right. We could not cool down those atoms in the way at which I justhinted until 1995, but Einstein showed what would happen in 1925, in maybe hislast amazing insight. He was a bit like Newton. He really was in touch with the waythe world works, and we still live in a world that he and his contemporaries divined.Hence my title. I do not think that there will be revolutions in physics in mygrandchildren's lifetimes. That is all too bold a conjecture. We do have theseproblems. The two great achievements from the early twentieth century just donot mesh. We cannot put (relativistic) gravity together with the quantum theory.We cannot find enough mass in the universe to keep it going! These are surelywhat Kuhn would have called anomalies, and he would have predicted that only arevolution would sort us out. String theory plus. Well, actually only superpluswould do it, and string theory minus is at present running on a serious lack of con-tact with the real world. But perhaps some future theory of strings or somethingeven more challenging will prove me wrong. I certainly want to encourage everyyoung and dreaming student to try to revolutionize physics. But we who are mere14 PUBLIC 33 ERRATAowls should look at what is around us. It is a physics that tells about the materialworld better than could possibly have been hoped for.That does not mean we know it all. That is where surprise comes in. Surprise(like revolution) is a relative notion. You are surprised by something that you donot expect. Let a city person walk in a real forest. I do not mean a preserved andhomogeneous wilderness area, out there in your canoe in tamed Algonquin Parkor whatever. The bewildered city walker in the real wild woods will be startledfrom time to time. Startle is different from surprise. Surprise comes when youknow what to expect, and it doesn't happen. Startle comes from having no ideawhat will happen. Precisely because physics is such a success, it fills us with verydetailed expectations. These are not expectations that follow from the fundamentalprinciples of a grand theory. They follow from complex models, ever simplifying.They model in detail how some isolated and highly controlled little bit of theworld will behave. The big theories do not tell us much. That is why high energyphysics needs so much money, to dragoon the world into acting as it says it should.And why it needs so many incredibly highly trained employees to do anything atall, hundreds of engineers, hundreds of physicists, hundreds of janitors. If highenergy physics were unionized, there would be 179 different unions, at least,involved in every major experiment at CERN.Most theorizing in physics is not like that at all. A typical lab has half a dozenpeople at work. The physics consists of making models of some very specialarrangements, and of building arrangements that match. We call that experimentand theory. The mix of both leads to a lot of very precise expectations. The sur-prises come when things do not work out. And they come all the time.Experiments do not work, models are not quite right. Most of the routine failuresteach nothing, except how to do something better. The real surprises are whatteach us. Kuhn was wrong. Physics does not need revolutions. It needs surprisesto keep it going.Here is an example I like. Ultracold physics is hot right now. In the past twentyyears we have been able to cool things down with quite astonishing success. Allsorts of techniques are used. A high-class version of evaporation is at presentessential. If you trap some atoms and some of the faster ones are encouraged towander off, they take some energy with them, and the remainder get colder. Butthere is a wonderful short cut. Get some atoms of just one species going in onedirection, and shine a laser beam of just the right frequency at those atoms. Theyget stopped dead in their tracks (sort of). That means they go much slower, and soare colder. It is of course more tricky than that. It is a practical version of theDoppler effect, which in this case has to do with the velocity of the laser light rel-ative to the prepared atoms. Theoretical models of what is happening predictexactly how much cooling (energy loss) you can get in this way.The building of the models and the building of the experimental apparatuswent hand in hand, in the 1980s. A team in California and a team in Paris foundPUBLIC 33 ERRATA 15just what was expected. But a third team near Washington D.C., from what usedto be the US Bureau of Standards-now the National Institute of Science andTechnology-was skeptical. Their mission is, after all, precision measurement.They could not replicate the expected measurements. In due course it turned outthat the laser technique cooled far better than could be expected. Surprise, surprise!For it is the rule that experiments always work worse than can be expected; thereis always something gumming up the works. But in this case, everything workedbetter than could be hoped for.The initial experiments got the expected result. Wrongly. They did not do sobecause they fudged their data to fit their expectations. There were several sourcesof systematic error. One resulted from the routine fact that when you buildapparatus you do it step by step. First you get the laser to cool the prepared atoms.Then you need to measure the result. You do so by letting the atoms expand afteryou turn your trap off. The rate at which they expand shows how fast they aremoving, how much energy they have, how cold they are. You find this out by tak-ing photographs of a little cloud of atoms expanding. You put the detector thatdoes this on top of the apparatus you have already built.But it makes a difference where the detector is! That was one of the firstthings the NIST people noticed. Why? Normally atoms pay no attention to gravity.They are moving so fast that gravity makes no difference. But these cooled atomsare so lacking in energy that they just-fall. Like stones. Exactly like stones, as amatter of fact, just as Galileo taught. The atoms coming out of the top of theapparatus are more energetic, warmer, than the ones coming out of the bottom,which are in almost free fall. Net result: Laser cooling as measured above theapparatus underestimates the cooling. The expected results were vvrong. The tech-nique works better than it ought to.Back to the drawing board. Something else has to be put into the model toexplain what is happening. The workers in Paris who figure it out call it theSisyphus effect. When the beams of laser light and the prepared atoms cometogether, the atoms experience the wave of coherent light like a washboard, orrather like a washboard road in Alberta, which seriously slows you down, atomstoo. This is because all the light is vibrating at the same rate, so it looks just likewhat we call a wave. As it climbs up each hill in the laser light, an atom loses energy.Sisyphus: it has to keep pushing itself up every hill, and does not get it all back asit goes down into the trough. The surprise is explained. Nobel prizes all round(1997, Chu, Cohen-Tannoudji and Phillips, California, Paris, and NIST).Kuhn offered Max Planck and the problem of black-body radiation as his mostdetailed example of a scientific revolution, one that began the quantum theory. Awhole book's worth, read only by specialists, Black-Body TheoT)' and the QyantumDiscontinuity, 1894-1912. I offer the little story I have just told as a less thandetailed example of what I mean by a surprise. It is a surprise only because of howmuch we know. It is a valuable surprise because of new things it enables us to do.16 PUBLIC 33 ERRATAI suspect that the Nobel prize was awarded only in 1997, after laser cooling hadbeen used, in 1995 to produce the effects on cold atoms that Einstein had pre-dicted in 1925. (Nobel prize, Colorado and MIT, 2001.) I have been saying atoms,by the way, but the desired effect works on only one kind of isotope, one speciesof atom called bosons, named after the Indian physicist whose letter to Einstein in1924, about photons of light, led Einstein to his final amazing insight. In the lastcouple of years it has become possible to apply similar techniques to pairs of atomsof the other species of atomic isotopes, called fermions.These results are not revolutionary. They do not demolish any vision of howthe world is, or of the human place in nature. We do not have a Kant to undo anymore, but if there were one, he would be unmoved. Nevertheless, the surprise Ihave described helped open remarkable doors to new houses in which we shallfind out a lot more about nature. Not just very cold, lazy nature, but also it mayhelp us to understand impossibly hot, overwrought nature, for it is pairs of fermionsthat fuel neutron stars, and for the first time-that is now, not five years ago-wecan treat these items as collaborators, manipulate them to see what they do andhow they do it. Revolutionary, in one familiar sense, but not a scientific revolutionin Kuhn's sense at all.Surprise is the way it will go, in the foreseeable future. Surprise within astable conception of the world, immune to revolution. And of course if there is ascientific revolution that unseats the vision of the physical world that stabilized inthe course of the twentieth century, it will be a surprise, but not in the sense inwhich I have been talking.Surprise is very different from chance, the advertised topic of this issue ofPublic. Or it is very different from the kind of chance that was tamed during thenineteenth century. The manifesto for this issue starts by quoting Mallarme aboutthe throw of a die. In 1990 I ended my book, The Taming ifChance, by quoting thesame poem as evidence that chance, which in the Enlightenment had been thesuperstition of the vulgar, by the 1890s had become wholly domesticated, the stuffof social science, the matter of physics, the laws of the universe, the toy of artists.That is, the chance that is described by the laws of probability, which are the lawsthat run the world. Mallarme wanted to talk about the uncontrollable and free,but inexorable probability ran his show, whether he knew it or not. Chance is free-dom only in the little picture, not in the big one.But there is another sense of chance, as when we talk of chance events.Aristotle gave an example that still stands. I head out to the Saint LawrenceMarket on a Saturday morning, to get the week's supply of fresh vegetables. And10 and behold, I meet an old girlfriend whom I have not seen or heard of for donkey'syears. There is a perfectly good explanation of why I am standing at the stall buy-ing apples at 8 :45 on a Saturday morning. And there is a perfectly good reason whyshe, who usually lives in quite other parts of the world, is there beside me. Twoindependent causal histories intersect, and only the superstitions of the fatalist teachPUBLIC 33 ERRATA 17otherwise. It just happened that we met. We are rightly surprised: we are aston-ished at this chance meeting. Probabilities, the chance that was tamed, have noth-ing to do with it. The surprise is governed by unwitting expectations; I do notexpect to see a face, at this moment, a face that was once close to mine, but whichhas been apart and forgotten for so many years.And yet that tamed chance, probability, can step in here. Coincidences sur-prise us, but usually they too can be expected. It is not to be expected that todayI meet this person from long ago. But it is fully to be expected that I shall haveencounters from the past, especially at the St. Lawrence Market where peoplefrom my social class congregate on Saturday mornings. Probability rules evencoincidence.There is yet another kind of unexpectedness. A few years ago there was alot of fancy talk about chaos and catastrophe theory. Aside from some clevermathematics, that was mostly a reaction against over-confident big deterministicscience. People realized that tiny causes can have big consequences, and this ratherobvious fact was hyped. All that talk of chaos and catastrophe was intellectualplayfulness. But now occasional catastrophes may be starting to crop up moreoften than they used to.We manage risk by insurance. Insurance companies manage the risks ofinsurance by reinsurance. There are now fairly good reasons to think that globalwarming is going on at such a rate that more and more radical climate change willoccur. Hurricanes galore, frozen orange groves, melting glaciers, costly real estatesinks below the rising seas, the lot. Insurance companies used to get away byexcluding Acts of God from risks covered. That will not wash any more. Insurancebegan in a coffee house in London just when the world was beginning to stabilize,and it has become more and more stabilized. Insurance companies, including pen-sion funds, which are based on pure actuarial-probability-calculations, are thebiggest accumulations of capital on earth. Climate change is beginning to makethem run scared. After 400 years ofincreasing stability, we may be undoing it all.More and more potential catastrophes will not be covered. Reinsurance won'tback the insurance.The grand accumulations of capital are beginning to expect the unexpected.Your children will not be able to get insurance for their holiday properties becausethe reinsurers won't back the insurance companies to which you and I now turn.But this is not a matter of surprise. Quite the contrary. We may not know quitewhich hurricane or sudden freeze may hit where, but that that sort of thing is tobe expected. Is expected, by the financiers. It is a bit like my meeting myoIdfriend. That particular friend was not expected, but some forgotten old acquain-tance, for good or ill, will cross my path quite soon.The difference between these kinds of example, and the physics tale, is thatthe physical surprise is governed by extremely precise expectations. Precisionengendered by models based on theories that grasp the microstructure of the18 PUBLIC 33 ERRATAworld in ways that were only dreamed of by Galileo. And he did dream of them!But for a long time his dreams were not enough to give a regular round of surprises.Now they are. The Galilean dream of a mathematical structure that mirrors the(im)material world is in place. It took revolution to get us here, but from now on,it will only be surprises.PUBLIC 33 ERRATA 19

Once There Were Revolutions: Now There Are Only Surprises

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Once There Were Revolutions: Now There Are Only Surprises

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