By Hamish Johnston
Our good friends in the journals department have just published two special issues containing 850 papers on low temperature physics — all of which are free to read online.
The papers were presented at the 25th International Conference on Low Temperature Physics (LT25), which took place in August 2008 in Amsterdam.
You can get stuck into this rich seam of research papers here
Matin Durrani was there and blogged from the event.
Physicists in the US have invented a new way to increase the lifetime of electron spins flowing in a semiconductor device. Their technique involves fine–tuning the properties of a tiny gallium-arsenide structure and could make it possible to create logic circuits that use electron spin.
Electron spins can assume one of two values — up or down — and this property is already used to store data in computer hard disks and magnetic memories. In the future, more advanced “spintronic” devices could exploit both the spin and charge of the electron to create a wider range of digital devices that are faster are more energy efficient than conventional silicon chips.
However, such devices would rely on electrons maintaining their spin as they travel around a circuit. This has proven difficult because each time such an electron scatters from a defect or lattice vibration in a metal or semiconductor there is a small chance that its spin could flip direction. This occurs because a change in the motion of the electron affects the direction of its spin thanks to an effect called spin-orbit (SO) coupling.
In most materials electrons experience many collisions and this flipping occurs randomly and very rapidly. This can be minimized by using defect–free materials kept at very low temperatures — but this is not really possible in practical devices.
Now Joe Orenstein and Jake Koralek of the Lawrence Berkeley National Lab; David Awschalom of the University of California Santa Barbara; and colleagues have tackled the problem by working out a way to tune the SO interaction in a tiny gallium arsenide structure called a quantum well ( Nature 458 610).
The team focussed on two aspects of how spatial symmetries within a semiconductor affect SO coupling — the Dresselhaus and Rashba effects. The former is related to the “inversion asymmetry” that occurs in gallium arsenide crystals and was adjusted by changing the width of the quantum well. The Rashba effect is caused by the application of an electric field to the quantum well and the team controlled this by adding impurities (dopants) to certain regions of the quantum well.
“We tuned the Rashba and Dresselhaus terms to be equal”, explained Koralek. This meant that the resultant SO interaction has a much higher spatial symmetry than in a typical semiconductor or metal. Although individual spins are still affected by spin-orbit coupling, they are able to rotate in unison in a long-lasting collective state called a “persistent spin helix” (PSH).
By using a laser technique called transient spin-grating spectroscopy, the team measured how long a PSH persisted in the quantum well. Two “pump” laser pulses are fired at the quantum well where the resulting interference pattern of light creates alternating stripes of spin up and spin down electrons — called a spin-grating. The wavelength of the spin-grating can be adjusted by simply changing the angle between the two pump pulses.
The amplitude and wavelength of the spin–grating are then measured by firing a third “probe” laser pulse at the sample and observing the resulting diffraction pattern. By varying the time between the pump and probe pulses, the team were able to measure how long the spin-grating endured.
They found that when the wavelength of the spin-grating matched the expected wavelength of the persistent spin helix, the spin-grating endured for hundreds of picoseconds — compared to just a few picoseconds when the wavelengths did not match.
This 100-times improvement was seen at the relatively low temperature of 5 K and the team found that it dropped off rapidly as the temperature increased to room temperature. This strong temperature dependence was not expected and could mean that the technique is not appropriate for use in practical spintronic devices.
Although a few hundred picoseconds doesn’t sound like a long time, Awschalom told physicsworld.com that such “spin engineered” materials could someday be used in devices that perform large numbers of spin operations on electrons before their spins decayed.
Koralek added that the Rashba interaction can also be controlled by applying a voltage to the quantum well — and this could lead to a spin transistor that could turn a spin current on and off.
The list of famous Bristolians is an illustrious one. The Victorian engineer Isambard Kingdom Brunel, for example, is recognized everywhere in Bristol for his many iconic structures, even though he was not born, bred or even resident in the city. Another well-known son of the city is the Hollywood legend Cary Grant, born as Archie Leach in the suburb of Horfield and now commemorated with a striking bronze statue outside Bristol’s hands-on science museum. The physicist Paul Dirac actually went to the same elementary school as Grant/ Leach, and the abstract sculpture dedicated to him stands just a stone’s throw away from Grant’s bronze likeness. Dirac also has a building named after him: Dirac House, the headquarters of IOP Publishing (which publishes Physics World).
Yet in spite of these efforts to publicize Dirac’s many contributions to science, his city of birth and (until recently) the school where he was educated seemed almost unaware that in Dirac, Bristol produced one of the great minds of the last century, and arguably the greatest British physicist since Isaac Newton. Part of this lack of knowledge among both Bristolians and the general public is Dirac’s legendary reticence, literal-mindedness and almost total inability to communicate with anyone — except, possibly, his immediate family.
All of this makes Dirac a very difficult subject for the sort of sympathetic biography that Graham Farmelo has produced in The Strangest Man: The Hidden Life of Paul Dirac, Quantum Genius. The book represents years of careful research and conversations with family and friends who knew Dirac and his work. In it, Farmelo, a science communicator and senior research fellow at the London Science Museum, describes the life and work of this profoundly brilliant man, exploring the origins of his near-pathological reticence and in the last chapter proposing a possible explanation. I doubt whether a better biography will appear in most of our lifetimes.
Dirac’s parents Charles and Florence were married in 1899 and lived for a time at 42 Cotham Road, probably in rented rooms, where Dirac’s older brother Felix was born. Shortly afterwards, Charles bought a small terraced house in Monk Road and Paul Adrien Maurice Dirac, the second son, was born in 1902. His sister Betty was born in 1906, so Flo certainly had her hands full with a young family and the ever-increasing and apparently irrational demands of her husband.
These demands included Charles’ insistence that only French be spoken at the family dining table. As a result, Flo, Felix and Betty ate in the kitchen, while Paul — whose French was just passable — was allowed to sit with his Swiss-born father. In later life, Dirac acknowledged that his difficulty in communicating with others may have stemmed from this period, poignantly explaining to Kurt Hofer — an Austrian- born cell biologist who became a close friend — that “since I found that I couldn’t express myself in French, it was better for me to stay silent than to talk in English”.
Time and again, Farmelo returns to the difficult personal relations that plagued Dirac’s family. Although in today’s parlance the Diracs were upwardly mobile — they soon moved to a larger semi-detached house in Julius Road, a more salubrious part of Bristol — Charles was also a serial tax evader. His crimes only came to light after his death, however, leaving Flo with an unwelcome tax bill. At one stage in the relationship she appears to have sought separation from her husband due to suggestions that he was having an extramarital affair, and their oldest child Felix committed suicide when Dirac was 23. But despite all of these traumas, Dirac is said to have wept only once in his life: in 1955, when he heard of the death of his hero, Einstein.
Given this background, it is hardly surprising that in his later life it was only with some unhappiness and after pleading from his mother that Dirac could be persuaded to visit Bristol. Instead, St John’s College, Cambridge, became the place he regarded as his true home. While there, Dirac made his most important breakthrough: he succeeded in welding together special relativity and quantum mechanics to produce what is often and rightly regarded as one of the great equations in physics. He became the Lucasian Professor of Mathematics there in 1932, and in 1933 his famous equation won him a Nobel prize (shared with Schrödinger) “for the discovery of new productive forms of atomic theory”.
The conclusions of the Dirac equation were highly controversial when they were first described in 1928, but in a curious way, the criticisms appeared to simply bounce off Dirac — a consequence, perhaps, of his deeply private personality. The idea of negative energy states and the consequent hole theory was finally resolved by the discovery of the positron in 1932. The equation also showed that spin was a natural consequence of relativity and quantum mechanics, and not simply an add-on to explain atomic spectra. Recognizing this, it is only just and fair that the unique characteristics of electrons that make such devices as transistors, mobile phones and solid-state lasers possible are known as Fermi–Dirac statistics.
Farmelo takes the reader through difficult physics in a masterly manner — a consequence, no doubt, of his vast experience in science communication. The author also describes some aspects of Dirac’s work of which even professional physicists may not be aware. For example, in 1933 Dirac started an experimental study with Peter Kapitza on the possibility of bending a beam of electrons with light. He also developed an experiment to separate isotopes — much to the approval of Ernest Rutherford, who thought that it “augurs well for theoretical physics that the Lucasian Professor is soiling his hands in the laboratory”. As a result, Dirac became peripherally involved in the Manhattan Project, performing theoretical investigations of the “separation power” of uranium-enriching devices, although he declined a fulltime position.
Dirac’s life changed dramatically during a sabbatical at Princeton University in 1934 when he met Margit Wigner, a Hungarian divorcee and mother of two children, Gabriel and Judy. Margit, the sister of nuclear physicist Eugene Wigner, was known to friends and family as Manci. She was the opposite in nearly every sense to Dirac, but their affection turned to love and they were married in January 1937. Manci had to spend some time in Budapest after the honeymoon and as a result, Dirac penned “the first love letter I have ever written”. Until then, Dirac had replied to questions from Manci in tabular form!
The marriage did experience some strains (often arising from Manci’s dislike of Cambridge), but Dirac was a loving husband and stepfather to Manci’s children and to the two daughters of the marriage, Mary and Monica. Within the family, Dirac appears to have been far more communicative than he was with outsiders. At the opening of Dirac House in 1997, I remember Monica describing how his scientific approach to vegetable gardening caused much amusement in the family, which Dirac took in good humour.
One feels a sense of anticlimax as the book nears its end. Dirac fell out with the Cambridge hierarchy over what seems a rather trivial dispute about car parking, and by the mid- 1960s he spent most of the week working at home. Meanwhile, Manci had set her heart on escaping from Cambridge, and in 1971, having seen their children well settled (except for Dirac’s stepdaughter Judy, who had disappeared in 1968 and was by then presumed to be dead), the couple finally emigrated from the UK to Florida, where Dirac died in 1984.
Physicists remain divided over the legacy of Dirac’s later years. Was his opposition to the success of quantum electrodynamics justified on the grounds that the theory lacked beauty? Do monopoles really exist? Can his large-number hypothesis — which suggests that fundamental constants change with time — ever be reconciled with general relativity? But all physicists agree that the towering achievement of the Dirac equation will, as Farmelo makes clear, set Dirac apart and place him in a league with Newton and Einstein.
Perhaps the most controversial part of the book is its last chapter, in which Farmelo explores the possibility that Dirac’s pathological reticence was in fact undiagnosed autism or Asperger’s syndrome. Autism covers a wide spectrum of behaviour, and as the writer and doctor Milo Keynes points out in The Notes and Records of the Royal Society (2008 62 289), it has become something of a catch-all phrase for behaviour that departs significantly from the norm: “In the past 10 years it has been firmly claimed that Newton must have shown the development disorder of Asperger’s syndrome, a disorder that has been posthumously assigned to Michelangelo, Henry Cavendish, Albert Einstein, Marie Curie, Ludwig Wittgenstein and Paul Dirac.” Clearly, Dirac joins a long and distinguished list of retrospectively diagnosed luminaries.
For what it is worth, my guess is that Dirac was by nature a shy individual and that this shyness was reinforced by a difficult early home environment. Farmelo is correctly very cautious in what he has written, and regardless of the conclusions he draws about Dirac’s personality, it is clear that writing about him has been a labour of love. I most warmly recommend this book both to professional physicists and to laypersons interested in fundamental physics, as well as to anyone who finds the interaction between personality and intellectual endeavour fascinating.
In 1890 an electricity company enticed the German physicist Max Planck to help it in its efforts to make more efficient light bulbs. Planck, as a theorist, naturally started with the fundamentals and soon became enmeshed in the thorny problem of explaining the spectrum of black-body radiation, which he eventually did by introducing the idea — a “purely formal” assumption, as he then considered it — that electromagnetic energy can only be emitted or absorbed in discrete quanta. The rest is history. Electric light bulbs and mathematical necessity led Planck to discover quantum theory and to kick start the most significant scientific revolution of the 20th century.
Around the same time, Planck’s colleague Wilhelm Röntgen was experimenting with cathode rays when he noticed an odd glow coming from a fluorescent screen some distance away that was not part of the intended experiment; in so doing he discovered X-rays, and helped propel medicine into the modern era. Of course, it is not just German scientists who make world-changing discoveries by unexpected paths. In 1964 US physicists Arno Penzias and Robert Wilson famously detected the cosmic microwave background radiation in annoying noise that they could not eliminate from their cryogenic microwave receiver at Bell Labs.
This is how discovery works: returns on research investment do not arrive steadily and predictably, but erratically and unpredictably, in a manner akin to intellectual earthquakes. Indeed, this idea seems to be more than merely qualitative. Data on human innovation, whether in basic science or technology or business, show that developments emerge from an erratic process with wild unpredictability. For example, as physicist Didier Sornette of the ETH in Zurich and colleagues showed a few years ago, the statistics describing the gross revenues of Hollywood movies over the past 20 years does not follow normal statistics but a power-law curve — closely resembling the famous Gutenberg— Richter law for earthquakes — with a long tail for high-revenue films. A similar pattern describes the financial returns on new drugs produced by the bio-tech industry, on royalties on patents granted to universities, or stock-market returns from hi-tech start-ups.
What we know of processes with power-law dynamics is that the largest events are hugely disproportionate in their consequences. In the metaphor of Nassim Nicholas Taleb’s 2007 best seller The Black Swan, it is not the normal events, the mundane and expected “white swans” that matter the most, but the outliers, the completely unexpected “black swans”. In the context of history, think 11 September 2001 or the invention of the Web. Similarly, scientific history seems to pivot on the rare seismic shifts that no-one predicts or even has a chance of predicting, and on those utterly profound discoveries that transform worlds. They do not flow out of what the philosopher of science Thomas Kuhn called “normal science” — the paradigm-supporting and largely mechanical working out of established ideas — but from “revolutionary”, disruptive and risky science.
All of which, as Sornette has been arguing for several years, has important implications for how we think about and judge research investments. If the path to discovery is full of surprises, and if most of the gains come in just a handful of rare but exceptional events, then even judging whether a research programme is well conceived is deeply problematic. “Almost any attempt to assess research impact over a finite time”, says Sornette, “will include only a few major discoveries and hence be highly unreliable, even if there is a true long-term positive trend.”
This raises an important question: does today’s scientific culture respect this reality? Are we doing our best to let the most important and most disruptive discoveries emerge? Or are we becoming too conservative and constrained by social pressure and the demands of rapid and easily measured returns? The latter possibility, it seems, is of growing concern to many scientists, who suggest that modern science is in danger of losing its creativity unless we can find a systematic way to build a more risk-embracing culture.
The voices making this argument vary widely. For example, the physicist Geoffrey West, who is currently president of the Santa Fe Institute (SFI) in New Mexico, US, points out that in the years following the Second World War, US industry created a steady stream of paradigm-changing innovations, including the transistor and the laser, and it happened because places such as Bell Labs fostered a culture of enormously free innovation. “They brought together serious scientists — physicists, engineers and mathematicians — from across disciplines”, says West, “and created a culture of free thinking without which it’s hard to imagine how these ideas could have come about.”
Unfortunately, today’s academic and corporate cultures seem to be moving in the opposite direction, with practices that stifle risk-taking mavericks who have a broad view of science. At universities and funding agencies, for example, tenure and grant committees take decisions based on narrow criteria (focusing on publication lists, citations and impact factors) or on specific plans for near-term results, all of which inherently favour those working in established fields with well-accepted paradigms. In recent years, tightening business practices and efforts to improve efficiency have also driven corporations in a similar direction. “That may be fine in the accounting department,” says West, “but it’s squeezing the life out of innovation.”
A key problem, suggests mathematical physicist Eric Weinstein of the Natron Group, a hedge fund in New York, is that it is too easy for scientists in the “establishment” of any field to cut down new ideas, and to do so without really putting anything at risk, thereby leading to a culture that is systematically biased toward caution. “High-risk science is much more associated with figures from the past,” he says.
The result, he suggests, is that science is becoming less a “bottom-up” enterprise of free-wheeling exploration — energized by the kind of thinking that led Einstein to relativity — and more a “top-down” process strongly constrained by social conformity, with scientific funding following along fashionable lines. The publish-or-perish ethic, in particular, strongly rewards those scientists doing more or less routine technical work in established fields, and punishes more risky work exploring unproven ideas that may take a considerable period of time to reach maturity.
This is especially damaging given the disproportionate benefits that come from the most important discoveries, which seem to be inherently unpredictable in both timing and nature. As Taleb argues persuasively in The Black Swan, any sensible long-term strategy in a world dominated by extreme and unpredictable events has to accept, and even embrace, that unpredictability. He illustrates the idea in the financial context. People investing in venture-capital start-ups, for example, have to expect continual losses in the short term, and bank on the fact that they will ultimately make up for those losses by hitting on a few really big winners in the long run.
More generally, Taleb’s basic investing strategy — which could easily be translated into research terms — is to put a fair fraction of funds into very conservative processes that will not lose their value, even if they have little chance of producing big gains; and to put a small but reasonable fraction into high-risk, high-reward settings, thereby gaining exposure to the potentially enormous gains from these investments. These may be unpredictable in detail, but the statistics makes the expected long-term pay-off very high.
Even so, it takes discipline and fortitude to stick with this strategy. As Taleb points out, if everyone around you believes in the dominance of normal statistics, then they will think that you are foolish, and the short-term evidence will probably back them up. You will be losing money in the short run, seeing no returns, and this may go on for a considerable time. The same goes for high-risk science relative to research pursuing more short-term goals. In the short run, what the mavericks do will almost always seem less successful, perhaps even like wasting their time, and it is easy to think that this is the kind of research we should not pursue, even if this is actually very much mistaken.
This is a trap, West suggests, into which modern science planning has fallen. “My fear”, he says, “is that by eliminating the mavericks we end up hobbling our ability to discover the big, new ideas — the next transistor. That’s a serious and tragic error.”
What is to be done? Some funding agencies, of course, have long recognized the need to fund “blue sky” research — work that may be high risk but may also be high reward. In the US, for example, the National Science Foundation has high-risk programmes in areas ranging from basic physics through to anthropology. Similarly, the European Commission, even in the decidedly practical area of information and communications technology, has a programme in future and emerging technologies that only funds research identified as having the potential to overturn existing paradigms. Perhaps the most famous centre that supports high-risk science demanding long-term commitment and transdisciplinary involvement is the SFI, which is privately funded. In the past few years, the SFI has been joined by a host of new centres, such as the Perimeter Institute for Theoretical Physics in Waterloo, Canada, a public–private initiative strongly aided by the Canadian government and founded in 1999 by Mike Lazaridis, chief executive of Research in Motion, which created the BlackBerry.
But physicist Lee Smolin, currently at the Perimeter Institute, suggests that science overall requires a much broader and more coherent approach to risky science. To see the kinds of policies needed, he suggests, it is useful to note that scientists, at least in some rough approximation, follow working styles of two very different kinds, which mirror Kuhn’s distinction between normal and revolutionary science.
Some scientists, he suggests, are what we might call “hill climbers”. They tend to be highly skilled in technical terms and their work mostly takes established lines of insight that pushes them further; they climb upward into the hills in some abstract space of scientific fitness, always taking small steps to improve the agreement of theory and observation. These scientists do “normal” science. In contrast, other scientists are more radical and adventurous in spirit, and they can be seen as “valley crossers”. They may be less skilled technically, but they tend to have strong scientific intuition — the ability to spot hidden assumptions and to look at familiar topics in totally new ways.
To be most effective, Smolin argues, science needs a mix of hill climbers and valley crossers. Too many hill climbers doing normal science, and you end up sooner or later with lots of them stuck on the tops of local hills, each defending their own territory. Science then suffers from a lack of enough valley crossers able to strike out from those intellectually tidy positions to explore further away and find higher peaks.
“This is the situation I believe we are in,” says Smolin, “and we are in it because science has become professionalized in a way that takes the characteristics of a good hill climber as representative of what is a good, or promising, scientist. The valley crossers we need have been excluded or pushed to the margins.”
Smolin suggests that we need to shift the balance to include more valley crossers, and that this should not really be too hard to do if we take a determined approach. What we need, in general, is to put policies in place that will judge young scientists not on whether they are linked into programmes established decades ago by now-senior scientists, but solely on the basis of their individual ability, creativity and independence. Some specific steps that might be taken, he suggests, include ensuring that departments strong in any established field also include scientists with diverging views. Similarly, conferences focusing on one research programme should be encouraged to include participants from competing rival programmes.
In addition, funding agencies should develop a means of penalizing scientists for ignoring the really “hard” problems, and of rewarding those who attack long-standing open issues. Perhaps, Smolin suggests, an agency or foundation could create some really long-term fellowships to fund young researchers for, say, 10 years, thus allowing them the space to pursue ideas deeply without the pressure for rapid results.
Weinstein suggests another idea — that we should borrow some ideas from financial engineering and make scientists back up their criticisms by taking real financial risks. You think that some new theory is utterly worthless and deserving of ridicule? In the world Weinstein envisions, you could not trash the research in an anonymous review, but would buy some sort of option giving you a financial stake in its scientific future, an instrument that would pay off if, as you expect, the work slides noiselessly into obscurity. The money would come from the theory’s proponents, who would similarly benefit if it pans out into the next big thing.
Weinstein’s point is that markets, in theory at least, work efficiently and — putting the current financial meltdown to one side — lead to the accurate valuation of products. They exploit the “wisdom of crowds”, as a popular book of the same title recently put it. Take the famous electronic prediction markets at the University of Iowa, which pool the views of thousands of diverse individuals and consistently seem to give better predictions than any expert. For example, they predicted last year’s US presidential election correctly to within half a percentage point.
Could the same not be done for weighing up the likely value of scientific ideas? Those ideas, Weinstein argues, do not get weighed fairly today. As he points out, mavericks get their papers routinely rejected for what they feel are unfair reasons, and they often feel suppressed by the mainstream community, while mainstream scientists think it is perfectly obvious that the ideas in question are ludicrous and should not waste the community’s time. Current research practice lacks any mechanism that would arrange a fruitful meeting between the two — letting the maverick’s ideas gain free expression while at the same time letting the critics take a real stake based on their own knowledge.
“What do you do when you’re confronted with some maverick with a crazy idea?” he asks. “You’ve tried it, your students have tried it, and you know it’s almost certain to fail. Why can’t you use this knowledge to your own advantage? At the moment, you just can’t express your view in the market efficiently.”
The situation is directly akin to a trader on the stock market who has sound knowledge, for example, that a certain asset is currently undervalued, but, for whatever reason, cannot buy it and so benefit from that knowledge. In financial theory, a market of this kind of called “incomplete”, and its incompleteness leads to inefficiency, because all relevant knowledge does not get expressed in the market.
To counter the analogous inefficiency in the case of science, Weinstein suggests, it should be possible for the critic to take a position on the idea. “It would be more efficient,” he says, “if the maverick could demand of the critic, if my theory is so obviously wrong, why don’t you quantify that by writing me an options contract based on future citations in the top 20 leading journals secured by your home, furniture, holiday home and pension?”
That may be going a little over the top, but it makes the point. Bringing such possibilities into play, Weinstein suggests, would move research practice closer to the “efficient frontier” — the place where ideas get judged fairly based on all available knowledge, and risk takers, rather than being suppressed by social conformity, get encouraged by those taking a financial stake in the potentially enormous consequences of their success. Such mechanisms, Weinstein argues, would help avoid the effective censorship that often afflicts peer review, and that currently keeps research on the cautious side of the efficient frontier.
As one specific idea, Weinstein envisions something he calls synthetic tenure, which resonates with Smolin’s call for long-term fellowships. Today, he suggests, young researchers can easily be deterred from tackling really hard problems because they fear for their careers if they work on an issue for a decade and do not make significant progress. To give exceptional researchers the confidence to tackle hard problems, he suggests that an agency or foundation might make an agreement by which they would guarantee that person a good position in the future in some stimulating field, if their project does not work out.
It is precisely this kind of thing, Smolin argues, that could be helpful. If more scientists started pushing for a return to independent, curiosity-driven science, then this might also encourage the big funding agencies and the other new sources of private funds such as the Perimeter Institute or the Howard Hughes and Gates Foundations. Indeed, Weinstein suggests, these new structures may have similarities with recent developments in financial engineering with the new structures emerging as “intellectual hedge funds” in response to perceived inefficiencies of more traditional agents, which play the role of more risk-averse mutual funds.
The price to pay for not moving to re-establish such independence will lie in a failure to realize the huge and unpredictable discoveries that move science forward most in the long term — discoveries made possible only when individuals leap out of what is comfortable and accepted, and wander out into spaces unknown. It is the true enormity of the potential gains that makes this goal of reaching the “efficient frontier” so important. If today we seem to have a dearth of new Einsteins, Smolin suggests, this may just reflect that we have become a little too risk averse.
New Einsteins, he points out, will not be working in areas that have been well established for decades. They may not even work in an area linked to the name of any established, senior scientist. New Einsteins may be slipping out of view and out of science altogether just because our scientific culture currently simply has no way of encouraging them.
I once interviewed the Northern Irish physicist John Bell, who told me a curious tale about the wife of the then-American ambassador to Switzerland. Bell recalled how she rolled up at his office at CERN bearing a dog-eared copy of The Dancing Wu Li Masters, a book by the author and “soul-healer” Gary Zukav, seeking answers to her questions about the connections between quantum physics and Eastern mysticism.
I expected the seasoned, hard-nosed physicist to take a dim view of both book and woman, and was startled when he did not. Bell said he felt that there was little harm and some good in Zukav’s book. Quantum physics was marvellous, but so inaccessible that anything that allowed outsiders to start conversations with physicists was fine with him.
Although we classify such books as “popular science”, it is a category that embraces quite a bit. Popular science can refer to science that is popular with the public — dinosaurs, superbugs, cosmology and the like. It can refer to science that appears in literature, such as plays by Tom Stoppard. Or it can refer to “expository” works that set out to explain scientific ideas to non-scientists, be they written by scientists such as Richard Feynman or non-scientists like Zukav.
Elizabeth Leane, a lecturer at the University of Tasmania in Australia, has recently looked at such expository works in a new book called Reading Popular Physics. In it, she notes that such material plays a strong role in shaping the interface between science and culture, as it is almost always what novelists and playwrights consult when learning about science. Stoppard’s play Hapgood, for instance, begins with a quote from a Feynman popularization about how the double-slit experiment contains “the only mystery”.
It is tempting to view popularizations in what I call the “Moses and Aaron” framework. Just as Moses, the prophet, wrests knowledge from the beyond that his brother and spokesman Aaron transmits to the masses, so scientists discover truths about nature that popularizers translate into everyday language. The Moses and Aaron model treats popularization as a single skill directed at a single community.
But Leane points out that popular exposition is far more complex. There is a variety of literary tools — or “textual strategies” as she calls them — for starting conversations, and different branches of science lend themselves better or worse to each. Using Paul Davies’ triage of the physics frontiers into “the very small, the very large and the very complex”, Leane describes the characteristic strategies used to popularize cosmology, quantum physics and chaos/complexity.
Explaining quantum theory, for instance, seems both to require and to shipwreck metaphors — for what is “down there” just does not behave like what is “up here”. A common tool is to anthropomorphize, personifying elements of the quantum world. Certain books, such as George Gamow’s Mr Tompkins Explores the Atom, use such anthropomorphic metaphors guilelessly, trusting the reader to recognize the difference between what is literal and what is not. Others, especially the “new-age” accounts, tend to deliberately blur that difference for their own ends. These include Zukav, who moves from a claim about the role of observation on atomic systems to the claim that “physics has become a branch of psychology”.
Expositions of cosmology tend to appropriate the narrative conventions of the novel. These are “mythic” to the extent that they depict the course of science as having a smooth linear structure and as heading towards an ultimate, yet-to-be-achieved goal, when in reality science follows blind alleys, false starts and dead ends. Leane shows that while a book like Steven Weinberg’s The First Three Minutes denounces the blurring of myth and science, it also deploys “mythic narrative structures” in depicting unification theories as the ultimate goal of the universe.
Finally, Leane examines James Gleick’s Chaos and other books that emphasize details of person, place and time. Expositions of this kind, she says, often borrow from established literary character types in their portrayals of scientists and scientific advance; Gleick favours the hard-nosed detective “mixing it up” with the world. But these character types carry additional baggage — they tend to be loner males with dysfunctional families — which can distort the underlying story.
Many strategies discussed by Leane appear in “the top 10 books from the last 20 years” that were picked by the Physics World editorial team last October (p33 — print edition only). For example, Stephen Hawking’s A Brief History of Time (which topped the list) presents a linear progression of the universe in a cosmic evolutionary narrative that starts with the Big Bang and culminates not with the end of the universe, but with the end of physics — the search for a “theory of everything”. Dava Sobel’s Longitude (in fourth place) is more historical and character-based, focusing on an artefact and its creator. Feynman’s What do You Care…? (ninth) is a classic example of the cultivation of a popular stereotype of the scientist.
All too often, Leane writes, the public and even non-science scholars treat popular expositions of science naively as “information sources” rather than as “textual reconstructions”. This can create profound misunderstanding, and Leane traces much of the hostility between the sciences and the humanities to distorted images of the other side gained from the innocent use of popularizations. Leane’s work shows that the literary character of popularizations should not be ignored just because they are about science, but should be as much the subject of literary analysis as any other form of writing.
Starting conversations — as Bell told me that Zukav’s book does — is one thing, but maintaining and strengthening such conversations is another. Encouraging good conversation requires understanding conversational strategies — both their use and misuse — and for this purpose Leane’s book provides a fruitful beginning. For while the long-term strength of science depends on many things — funding, reliable careers and good teaching, among others — it also depends on healthy, long-term conversations between scientists and non-scientists.
I liked physics when I studied it at high school, though I did not have an advanced introduction to it until I was an undergraduate at Yale. It took me a while to develop what physicists call “intuition”, but I always liked the connection between mathematics and physical reality.
My school had a jazz ensemble and I had been playing piano since childhood, so I auditioned a few times and eventually got involved. Our local library had a lot of jazz albums, so I began investigating, and a few of my friends and I started a quartet that mangled jazz standards. I kept at it throughout university and started writing music for small groups that I was leading. I saw the documentary Straight, No Chaser about the great composer-pianist Thelonious Monk around this time, and I was inspired – it was like I had been struck by lightning.
When I moved to Berkeley, California, to begin my PhD, I found myself playing professionally around Oakland and San Francisco. I did not expect things to develop as rapidly as they did, but one thing led to another and I found myself pretty deeply involved in the Bay Area’s music world. For a while I led a double life – budding physicist by day, musician by night. Soon it was not just about playing gigs; it started to be more about becoming an artist.
A couple of years into my PhD, I had done well in my classes but was reaching an impasse with my research project, which was in theoretical solid-state physics. I decided to put the research on hold, take a teaching assistantship, and regroup. It was a real soul-searching moment. In the early-to-mid-1990s, job prospects were sort of grim for physicists, so I had to face that reality. At the same time I was getting a lot of satisfaction as a musician, and I soon realized that I loved that more than anything else. All walks of life offer their own frustrations, and music and physics are no exceptions. But if you really want to be happy, I realized, you have to love what you do.
I started touring in Europe and recorded my first album in 1995. I also hooked up with some key academic mentors – primarily David Wessel, a research pioneer in music perception and director of the computer-music centre at Berkeley. With guidance from Wessel and a few others, I switched to an independent interdisciplinary PhD programme that we created called “Technology and the arts”. This allowed me to take music performance and composition seriously while doing academic research in music perception and cognition. I completed this PhD in December 1998 and immediately moved to New York, stepping right into the city’s vast and diverse arts world. I have been a full-time artist for the last decade, while keeping a toe or two in academia.
I have this love for mathematical rigour and elegance, which influences the rhythms, forms and structures of my compositions. Often, I approach composition as solving problems with constraints. I look for the simplest solution, which is a cherished aesthetic for physicists. I always admired this about Paul Dirac, for example. There are other connections, too. Rhythmic periodicities can be likened to the crystalline lattices of solid-state physics; once I went so far as to consider the implications of a rhythmic Brillouin zone. I also think about harmony in terms of the physics of sound: the overtone series, resonances and psychoacoustics. But let’s face it – I am not doing quantum mechanics anymore. I “left” physics for music. I think that the playing of music gives me what physics did not: a visceral excitement, and the spark of real-time collaboration. I am sure that physics can do those things too, but in my case music did it first.
I read the science section of the New York Times each week, but because of my research in music perception, my scientific interests have drifted more to neuroscience, so I follow that a little more closely.
There are a couple of new albums that will surface in 2009 under my name, and I will be touring Europe several times in the coming year with my various ensembles. I am also developing a couple of new projects: one a site-specific installation in collaboration with a filmmaker named Bill Morrison at an abandoned prison in Philadelphia, and another with the poet Mike Ladd about veterans of the recent wars in Iraq and Afghanistan. And I have been asked to think about “interplanetary” music in conjunction with some physicists who are working on the atmospheric acoustics on Mars, Titan and Venus.
I am standing on a bridge near the North Carolina coast. There is a light breeze, and I am enjoying some hazy sunshine. But this calm is an illusion: in a few minutes winds of up to 45 m s–1 (100 mph) will sweep in again. The approaches to my section of the bridge are already drowned under 2.5 m of water, and my companions on this island are an eclectic mix of traumatized animals, including snakes, rats, wounded pelicans and frogs. Earlier, one of the snakes flew through the air past my truck. The animals and I have been drawn to this bridge by Hurricane Isabel, which has just slammed into the coastal islands of North Carolina, and at the moment we are in the calm, sunny eye of the storm. The animals are just trying to survive on the area’s only dry ground. But I have come to the bridge with a radar system on a truck and have spent a night and a day on it because I want to know what is happening inside this hurricane.
Meteorological research is a highly mathematical subject, and I have been intrigued by maths since I was a small child. Once, I spent dozens of hours working out the digits of π using a printing calculator (this was the 1960s) and what I soon realized was a very slowly converging formula. But I also loved being outdoors, so in between my calculations I collected thousands of insects, pinned in boxes and stored in hundreds of pill boxes in my family’s freezer.
As I moved beyond collecting numbers and bugs, I became interested in weather. The study of atmospheric motion is very mathematical, essentially applied fluid dynamics, and the real-world effects of these equations can be seen every day. The equations of motion for the atmosphere cause trees to be blown down, hail to fall and snowdrifts to pile up — all things that I could witness while growing up in Pennsylvania.
I started out as a physics major at the Massachusetts Institute of Technology (MIT), but my real interest was meteorology, in which MIT only had a graduate programme. Fortunately, the university was quite indulgent of me, and I was allowed to combine my physics classes with several graduate meteorology classes to earn a hybrid degree in interdisciplinary science.
While I was finishing my PhD on microbursts at MIT, a “tea hour” discussion with some friends got me thinking about constructing weather radar networks using “passive” rather than the traditional “active” radar sites. Passive radar systems are almost a hundred times cheaper than active systems, which require expensive components like powerful high-voltage transmitters and large antennas. I wrote to the heads of a few research labs and was surprised that they not only read my letters, but even wanted to fly me out to explain my ideas. One of these trips brought me to the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, where I became a visiting scientist in 1991 and began developing and testing my new radar-network concept.
Before too long, however, I became distracted by how little we really knew about what was going on inside severe-weather systems. In the mid-1990s, no one had yet mapped out the winds inside tornadoes, so no one really knew how strong they were. After reading the relevant literature, I decided that a more ambitious technological and logistical approach could push back the veil of ignorance about these fascinating phenomena. So in 1994 I decided to shift focus, leaving NCAR for a faculty position at the University of Oklahoma, where I developed a prototype mobile weather radar system called the Doppler on Wheels (DOW).
A DOW is a cutting-edge Doppler weather radar that is mounted on a truck. The concept is simple. Instead of waiting for interesting weather to come to me, I drive to the weather (like Hurricane Isabel) and surround it with DOWs and other instruments. In its first few weeks of testing, the DOW made important new measurements inside tornadoes, which allowed my team to produce the first-ever 3D mapping of tornadic winds. With new data coming in every minute, we could watch the wind, debris and rain fields evolve in something close to real time.
Since 1995 the DOW and its descendents have observed and mapped the wind fields of more than 140 tornadoes. These include the most intense tornado ever documented, which hit Moore, Oklahoma, in 1999 with near-surface winds of 142 m s–1; and the two largest tornadoes ever mapped, one of which occurred in the same 1999 outbreak and had a core circulation that was more than 1600 m in diameter. We have also mapped the fascinating behaviour of multiple vortices, which are like miniature tornadoes-within-tornadoes and which are believed to cause the worst tornado damage.
After nine years at Oklahoma, family considerations and a dislike of academic politics led me to return to Boulder, where I founded a not-for-profit company: the Center for Severe Weather Research (CSWR). There are only a few other severe-weather researchers working outside established universities or labs, but so far our experiment seems to be successful. The DOWs are now available to all National Science Foundation principal investigators as “national facilities”, without charge to their grant programmes, and my group of three researchers, a technician, an administrator and me is continually finding new ways of using them.
In September 1996 my team and I took a DOW into Hurricane Fran, which was much scarier than a tornado. I can study tornadoes while remaining at a relatively safe distance where the winds are only 20–40 m s–1, but a hurricane’s storm surge will inundate many tempting DOW deployment sites and winds can exceed 50 m s–1. Moreover, once we pick a spot, we cannot easily change our minds, because often escape routes can be blocked by flooding, downed power lines and felled trees.
In recent years, we have also taken DOWs to wildfires, to map out hot spots and wind shifts, and to observe aircraft dropping fire retardants. We have studied coastal storm systems off California, observed simulated releases of toxins from aircraft pretending to be terrorists, and assisted meteorology studies in France, Germany, Italy and Switzerland. The DOWs have proved extremely versatile, and are useful for any meteorology project that needs finer-scale observations.
The best thing about my career is that I have the freedom to pursue my passions and curiosities. If I can obtain resources or link up with colleagues with similar interests, then we can rush into these projects — studying tornadoes, hurricanes, fires, winter storms, toxin plumes, bird migrations, whatever. In all of these areas, there are still big questions that can be addressed by “mere mortals”; you do not have to be one of the four smartest people on the planet to make important contributions. Field research has also given me opportunities to travel to parts of the world that I would otherwise not have visited, and to experience local cultures in ways that I could not as a tourist. I have lived on a remote Polynesian island operating a radar, deployed instruments in some very odd places in the Pacific, and visited just about every town in the US High Plains.
I get literally thousands of meteorology-related e-mails each year, many proposing outlandish ways to destroy tornadoes or hurricanes. Of course, most of these writers are cranks, but because my career in severe weather research got started when I sent unsolicited ideas about radar networks to established scientists, I always try to remember that there might be a useful needle buried in this haystack (although I have not found one yet).
I am often asked how to get into this kind of research. The obvious answer — study lots of maths and physics — is correct, but I would take this half a step further. I and some others in meteorology actually prefer young researchers to have backgrounds in physics or mathematics, rather than just meteorology. For example, I recently hired a postdoc who earned Master’s degrees in physics and teaching before doing her PhD in meteorology. Although several universities (such as Reading in the UK and Pennsylvania State in the US) do offer undergraduate degrees in meteorology, some of the best departments for meteorology research (including MIT) do not. So, I recommend getting a degree in physics with some maths courses that cover fluid dynamics and then specializing later.
The disadvantages of my career are typical of much of science: if you are smart, ambitious and want to make lots of money, or retire to play golf at 50, severe-weather research is a poor choice. A really smart person can probably make more money as a lawyer or even an online poker player. But in the end, I am thrilled with the career that I have chosen. It is different every day, and I have a lot of control over my direction and destiny. Most importantly, it is lots of fun.
Have you ever tried to electrocute a hot dog? Wondered how to make a robot out of a toothbrush, watch battery and phone-pager motor? Seen a cantaloupe melon and thought, “Hmm, I could make this look like the Death Star from the original Star Wars films”? If you have not, but you would like to — preferably as soon as you can find a pager motor — then this is the site for you. The Evil Mad Scientist Project (EMSP) blog is packed full of ideas for unusual, silly and frequently physics-related creations that bring science out of the laboratory and into kitchens, backyards and tool sheds.
The main authors are the intensely creative husband-and-wife team of Windell Oskay and Lenore Edman. A former physicist who now works at a California-based engineering firm, Oskay is responsible for most of the electronics-themed entries. Edman, meanwhile, studied classical Greek, which she says “prepared her well” for a career working with scientists and engineers. Her posts tend to focus on topics like fractal biscuits and LED origami. Other contributors include Edman’s young son Chris Brookman and the family’s two cats; the site also lists several like-minded “honorary mad scientists” who work independently on similar projects.
Any site that contains both Dalek-shaped pumpkins and an interactive LED kitchen table is going to be hard to summarize, but there are a few common threads. A huge number of projects involve nifty things to do with LEDs, and a sizeable minority require users to play with their food in ways that would make even the most innovative chefs gasp (edible googly eyes, anyone?). One intriguing idea that grew out of the site about a year ago is the Great Internet Migratory Box of Electronics Junk, a kind of round-robin letter for the digital age in which participants receive and pass on a small box of miscellaneous components in the confident hope that someone else will find them useful.
The authors aim to post new projects every Wednesday, but most weeks contain two or three new items. As of March 2009, there were 81 pages of archived entries stretching back to early 2006, so if recent projects do not interest you, there are plenty of others to look at instead. Older posts are semi-organized into topics like field trips, projects and “Play With Your Food”, although there is considerable overlap between categories.
Fans of science fairs and TV programmes like the UK’s Scrapheap Challenge will find much to appreciate on this site. The EMSP is part of looseknit network of “Makers” — people interested in creating new things in a way that fuses art, science and engineering — and this well-illustrated blog offers a user-friendly introduction to this community. Most of the food-related projects and some of the simpler electrical ones could be made by children with a bit of adult help. Others require a working knowledge of basic electronics and specialist equipment. A few, like the electrocuted hot dog, are downright dangerous, and should be attempted by dedicated tinkerers only — but everyone can appreciate the results from a safe distance.
Researchers in the Netherlands have imaged the flow of blood in a living organism for the first time using a medical technology known as magnetic particle imaging (MPI). In the method, iron oxide nanoparticles were injected into the bloodstream of mice before their flow was traced through vital organs using a technique similar to magnetic resonance imaging (MRI).
If the technology can now be adapted for use in the human body it could be help to diagnose heart disease and cancer and to monitor the body’s reaction to the treatment of these conditions.
“If we can know the amount of blood absorbed by a cancerous tumour we can learn a lot about how it is reacting to particular treatments,” said Joern Bogert, one of the researchers at the Royal Phillips Research Lab in Hamburg.
Over the years, medical imaging procedures like X-ray and MRI have been honed to produce high quality snapshots of bones and hard tissue inside the body. When it comes to resolving softer tissues and fluids, however, these techniques have had limited success. However, iron oxide particles injected into the body are highly visible because there are no other naturally occurring magnetic particles in the blood stream.
After conceiving the technique of MPI in 2001, the Philips researchers then presented an initial set up of their MPI scanner in a Nature Paper of 2005. At that time MPI could only produce images in 2D and the processing times were far too slow to be useful for medical applications.
Over the past four years, the researchers have improved the technique to obtain high spatial resolutions in 3D, and images can be captured over time periods as short as one fiftieth of a second.
With this latest advance, the researchers have transferred MPI from an inorganic demonstration to a full preclinical trial in a live organism. The series of in vivo experiments comprised scans on 18 mice using tracer concentrations in the range between 8 and 45 micro moles of iron oxide. To confirm that the MPI signal truly reflected the anatomy of the mice, the researchers then transferred the mice to a standard MRI scanner and produced a series of reference images (Phys. Med. Biol. 54.5).
“Testing MPI in vivo is a major breakthrough for us – bodies are incredibly complex and that’s why so many new medical procedures fail at this stage,” Bogert told physicsworld.com
The next step is to scale up this technique for use on humans. Using a range of scaling factors, the researchers predict that – without any further enhancement to the technique – it would produce images that are only 10 per cent as good as those from the mice experiments. Given this drawback, this new technology may still be a long way from making it into hospitals.
“MPI may be able to replace or compliment some MRI procedures, but it’s not likely that it would replace MRI altogether,” said Philip Grandinetti an NMR methods researcher at Ohio State University.”
Matthew Allen of Wayne State University is also cautious. “MPI may be useful for imaging functions like coronary blood supply but MRI gives anatomical data that MPI cannot – because MRI images tissue not nanoparticles.”
“Other hurdles might include obtaining approval from the government for the use of MPI in the clinic and convincing doctors to switch from their current imaging techniques to MPI,” he added.
Physicists are on the verge of demonstrating perhaps the ultimate application of the laser: creating nuclear fusion in the lab.
Later today the US Department of Energy will give official clearance for experiments to begin at the the $4bn National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California. NIF is a huge facility consisting of 192 pulsed laser beams with a total energy of 1.8 MJ, more than 60 times more energetic than those from any machine currently in existence. The first experiments are expected to begin in May.
Ignition is a grand challenge. People have been waiting for this moment for a long time Ed Moses, NIF director
NIF’s main goal is to focus all that energy onto a hollow sphere 2 mm in diameter made of beryllium and chilled to 1.8 K. This will make the sphere implode and squeeze the deuterium and tritium nuclei lying inside until they fuse to spark “ignition” — the point at which enough heat is generated to react surrounding fuel and achieve a sustained burn that produces excess energy. “Ignition is a grand challenge. People have been waiting for this moment for a long time,” says NIF director Ed Moses.
Construction of NIF began in 1997 but did not go smoothly at first, with capacitors prone to exploding. Extensive redesigns were required, which led the US Department of Energy to re-evaluate the project and redraw its schedule and budget. NIF is now opening five years behind schedule and almost four times over budget.
NIF is a huge facility – roughly the size of three football pitches. Each laser pulse starts out as a 1 μm infrared beam that is split into 48 beams and fed into preamplifiers that increase their energy 10 billion times. Each beam is then split into four and passed repeatedly through main amplifiers. After converting the wavelength into the ultraviolet, the total energy of the 192 beams is 1.8 MJ. When the combined laser pulse hits the 2 mm sphere, it explodes, causing an implosion on the inside that forces the fuel into the centre and compresses it to a density 100 times that of lead and a temperature of 108 K.
This is enough to spark fusion at the centre, which then burns outwards to cooler parts of the fuel. The fuel is trapped by its own inertia: the fusion burn proceeds faster than the fuel can move to escape. In theory, if all the fuel burns up, at least 20 MJ of energy will be liberated.
Moses says that NIF staff plan to ramp up the laser energy to 1 MJ this year and reach full power by the end of 2010, but predicts they will achieve ignition before then. “We’re feeling pretty confident,” says Moses. Mike Dunne, head of the Central Laser Facility at the Rutherford Appleton Laboratory in the UK, agrees that NIF is “overwhelmingly likely to succeed” but warns that the laser can set up “resonant waves” in the plasma that heat it faster than it can be compressed so that ideal ignition conditions are not achieved.
Another potential problem is “hydrodynamic instabilities” that mix the beryllium of the sphere with the fuel, thus spoiling the plasma’s ability to retain heat. NIF will also be used to validate computer simulations of nuclear weapons to ensure the US’s nuclear stockpile is safe, while astrophysicists will use it to simulate the interiors of giant planets, stars and supernovae.
