Monthly Archives: November 2010

Bust magazine tackles women in science

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One of the things my wife and I like to do over Thanksgiving is read magazines, especially unfamiliar ones. A few days before the holiday, we visit Borders or Barnes and Noble and buy a batch of magazines.

The October/November issue of Bust was among our haul. What had caught my eye in the magazine stand, besides the cover’s magenta logo and photo of Helen Mirren, was the line WE ♥ SCIENCE in the top left.

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Bust‘s tagline is “for women with something to get off their chests,” but the issue was as much about celebrating women in science and their achievements as it was about airing their grievances.

The opening editorial from Debbie Stoller, the magazine’s editor-in-chief, set the tone. Before introducing feature articles on Antarctic science and the actor and pioneering cryptographer Hedy Lamar, Stoller described her own experiences as a graduate student scientist:

I spent the better part of four years inserting electrodes into the tiny neurons of leeches (true story). But at a certain point, I couldn’t take it anymore. I loved the science part—wondering about how our amazing brains work and trying to puzzle out an answer kept me endlessly fascinated. Instead, it was the daily grind that got to me.

Stoller switched fields from neuroscience to psychology. If she encountered any sexism during her science career, she didn’t say.

Evidence of overt discrimination was also missing, thankfully, from Trina Arpin’s article in the same issue. Arpin profiled several women scientists at various stages of their careers, including three students. One of the students, Sylvana Yelda, is pursuing a PhD in astronomy at UCLA under the guidance of Andrea Ghez. Despite having to write computer code—the equivalent of Stoller’s threading electrodes into leeches—Yelda was quoted as saying “I love what I do. I just really love astronomy.”

But two other students, the University of Connecticut’s Jayinta Banerjee and Sarah Lamb, recalled encountering sexist attitudes that caused them to switch from physics to other fields: Banerjee to biology, Lamb to engineering.

Both women told Arpin that they felt they had to worker harder than men did to prove themselves. If that wasn’t bad enough,

Lamb noticed that her male classmates, who had treated her as an equal when school started, began to emulate their professors’ gender bias. “Watching my class move through the physics program, freshman and sophomore years, we were the best of friends,” she says. But junior year, when the students began working more closely with physics professors on special projects, her male classmates changed. “It was like guys who had supported me turned into the mentors [they worked with],” adopting their professors’ tendencies to openly doubt her abilities and intellect.

Science in general and physics in particular will remain competitive—for the simple reason that telling a scientist not to work hard at something he or she loves, even when it entails tedious tasks, is usually futile.

But science in general and physics in particular don’t have to, and should not, remain hostile to women. The depressing thing about Banerjee’s and Lamb’s experiences is that they didn’t ask for or expect special treatment, just equal treatment.

Charles Day

Turkey and Bose-Einstein condensates

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Fred Dylla, the CEO of the American Institute of Physics, advocates roasting your Thanksgiving turkey at 533 K (500 °F, 260 °C). Charlie Burke, a food writer for the Heart of New England, concurs. According to Burke,

High heat roasting (500 degrees) intensifies flavors and considerably shortens
cooking time so there is less time for the white meat to dry out while the dark
meat reaches proper temperature. We have found that fresh local turkey
cooks in a surprisingly short time and has superior taste, although
commercial turkeys are quite consistent in quality. It is important that the
oven be clean, because excess smoke will be caused by any residue in the
oven.

High-temperature roasting also makes sense physically. The higher the temperature, the steeper the temperature gradient is between the air inside the oven and the meat inside the turkey. Heat enters the turkey more effectively than at lower temperatures.

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To the extent that an oven is like a blackbody radiator, high-temperature roasting brings another advantage. As the figure above shows, as you raise the temperature, you increase the number of photons available to cook the turkey.

Although it’s good for roasting turkeys, the blackbody spectrum’s dependence on temperature is bad for making a Bose–Einstein condensate. As the archetypal bosons, blackbody photons should form a BEC. The trouble is, as Martin Weitz of the University of Bonn puts it in a paper in today’s Nature,

In such systems photons have a vanishing chemical potential, meaning that their number is not conserved when the temperature of the photon gas is varied; at low temperatures, photons disappear in the cavity walls instead of occupying the cavity ground state.

Weitz and his colleagues Jan Klaers, Julian Schmitt, and Frank Vewinger overcame that problem in an ingenious way. Their photon gas is not generated by an ovenlike cavity. Rather, they place a dye solution between two closely spaced concave mirrors and illuminate it with a laser.

Photons resonant with the mirrors’ separation bounce back and forth, but only after undergoing multiple scatterings off the dye molecules. The scatterings, which occur when the dye molecules are in an excited, laser-pumped state, are crucial because they ensure that photons interact weakly, not strongly, with each other, thereby satisfying a prerequisite for condensation.

The trapped photons have such a low effective mass that they condense at room temperature in the mirrors’ lowest accessible resonance. Weitz and his team bring about condensation when they increase the laser intensity, and therefore the density of scattered photons, above the critical value.

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The left panel shows the photons just before the onset of condensation; the right panel shows a condensed central spot of photons condensed into a single macroscopic state (the mirrors’ TEM00 mode, to be precise).

I’m not sure whether Weitz, Klaers, Schmitt, and Vewinger ate Thanksgiving turkey today, hot-roasted or otherwise. But their coup de recherche is certainly cause for celebration. In the acknowledgments section of their paper they thank Jean Dalibard and Yvan Castin for discussions, the German Research Foundation for funding, and the Kastler Brossel Laboratory in Paris for hospitality.

Charles Day

Theorists in industry: Long may they thrive!

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Twelve years ago, my fellow Physics Today editor Toni Feder and I visited Bell Labs in Murray Hill, New Jersey. Whether Bell Labs had passed its peak by then, I couldn’t tell, but it was certainly doing innovative science under its new parent, Lucent Technologies.

During the day-long visit, Toni and I met two of pioneers of quantum cascade lasers, Claire Gmachl and Federico Capasso, who demonstrated how one of their tiny devices could light a match. Tony Tyson showed us the latest images of gravitationally lensed galaxies that he’d obtained using his CCD cameras.

We also met Arun Netrvali, the Bell Labs president. Netravali is one of the leaders in digital technology. He invented, among other things, the digital compression algorithm that underlies high-definition television. Unlike the other researchers we met, he’s a theorist.

Despite the obvious practicality of Netravali’s work, the notion that an industrial research lab should employ theorists might seem strange. In fact, theorists have a long history—and, I hope, a long future—in industrial research.

Some industrial theorists, such as Claude Shannon, Rolf Landauer, and Charles H. Bennett, lay down frameworks for experimenters to exploit. Shannon invented information theory at Bell Labs. Landauer and Bennett, both IBMers, extended information theory into the quantum realm.

Other industrial theorists, such as John Bardeen and George Hockham, help guide the research of their experimentalist colleagues. Bardeen made crucial contributions to the invention of the transistor at Bell Labs. Hockham explained the opacity measurements on optical fibers that his coworker Charles Kao made at Standard Telecommunication Laboratories.

Although industrial labs around the world are shrinking, theorists are still employed by them. Hewlett Packard, for example, runs a social computing laboratory at its research campus in Palo Alto, California. The lab’s director, Bernardo Huberman, used to work in condensed-matter physics.

Indeed, the ranks of industrial theorists, past and present, are exalted enough that newly graduated theorists should give thought to working for a company, not a university. Last week IBM posted a job ad for theoretical physicist to work in superconducting qubits.

When Toni and I met Netravali, he told us why he liked working at Bell Labs. “It’s a problem-rich environment,” he said.

Charles Day

The seemingly improbable physics of the whole caper

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NASA’s Goddard Space Flight Center, the University of Maryland’s main campus, the Institute for Defense Analysis’s center for computing sciences, and Physics Today‘s editorial offices are all in Prince George’s County, Maryland. Last week FBI agents arrested the county’s chief executive, Jack Johnson, and his wife, Leslie Johnson, on corruption charges.

The Washington Post‘s news story about the arrest opened with a memorable scene, which Post reporters Paul Schwartzman, Ruben Castaneda, and Cheryl Thompson recreated from FBI wiretaps:

Just after 10:12 a.m. Friday, Leslie Johnson frantically phoned her husband, Jack B. Johnson, the Prince George’s county executive.

Two FBI agents were at the front door of their two-story brick colonial in Mitchellville.

“Don’t answer it,” the county executive said, unaware that more agents were listening in.

Johnson ordered his wife to find and destroy a $100,000 check from a real estate developer that was hidden in a box of liquor.

“Do you want me to put it down the toilet?” Leslie Johnson asked.

“Yes, flush that,” the county executive said.

But what about the cash? she asked – $79,600.

Put it in your underwear, the county executive told his wife.

She replied, “I have it in my bra” – which is where agents discovered the money after she answered the door.

The main topic of this blog post isn’t Prince George’s County, but the metaphorical use of the word “physics” by Petula Dvorak, the Post’s metro columnist. The second paragraph of her column about the Johnsons’ arrest ran: “That bra. The cash. And the seemingly improbable physics of the whole caper.”

At first I thought Dvorak used “physics” to suggest something difficult and puzzling, but my wife, Jan, had a better answer. “Eighty thousand dollars. How would you hide that in a bra?,” she wondered. To Jan, “physics” suggested a physical, concrete challenge.

But it turns out that $79,600 in cash, if denominated in $100 bills, isn’t especially bulky. Given that a bill is 100 μm thick, Leslie Johnson would have had to conceal two wads each about 4 cm thick. If she wore a loose-fitting dressing down (the raid took place in the morning), the illicit cache of cash might not be conspicuous.

So maybe Dvorak really did mean “physics” to convey something difficult and puzzling. Out of curiosity, I asked her by e-mail. I’ll let you know if she replies.

Charles Day

The rare pleasure of physics

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The Order of Merit is one of Britain’s most exclusive clubs. Limited to 24 living members, the OM honors distinguished service in the arts, science, industry, and war. Lords Kelvin and Rayleigh were among the first group admitted to the order in 1902. On receiving the honor from King Edward VII, Rayleigh remarked,

The only merit of which I personally am conscious was that of having pleased myself by my studies, and any results that may be due to my researches were owing to the fact that it has been a pleasure for me to become a physicist.

Rayleigh enjoyed physics so much that he’d investigate topics that lay outside the mainsteam, such as tennis ball trajectories, insect color, and the soaring of albatrosses.

Most people, however, don’t share Rayleigh’s love of physics, especially high-school physics. When I tell members of the nonphysics laity that I work for a physics magazine, a typical reaction is “Man, I hated physics in high school. I just didn’t get it.”

Bad or uninspiring teachers are sometimes responsible for the unpopularity of physics. But even good and inspiring teachers have a tough time with a subject whose prime directive is to distill natural phenomena and express them in abstract mathematics. If a school’s catalog of courses were a music store, physics would be the modern jazz section, where you’d find the likes of Eric Dolphy’s 1964 album Out To Lunch!

Improving the teaching of physics should be a high priority. Biologists, chemists, and engineers need a basic understanding of physics to practice their chosen fields effectively. And everyone, nonscientists included, would benefit from knowing a little of the physics behind air conditioners, cars, cookers, and other everyday machines.

However, just as modern jazz is enjoyed by a small band of enthusiasts, physics will likely remain a minority interest. Physics is too esoteric and difficult to become as popular as country and western music.

Does that matter? Probably not. As long as everyone who wants to become a physicist can become one.

Charles Day

QM in SF

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Although writers of science fiction can be reasonably accused of flouting the laws of physics, they nevertheless incorporate real physics—or extrapolations of real physics—in their work.

Quantum mechanics especially tempts writers. Despite being more than a century old, the theory seems perpetually modern, like Bauhaus architecture, twelve-tone music, or imagist poetry. Moreover, quantum mechanics is difficult, subtle, and weird.

There is, however, a problem with incorporating entanglement, complementarity, and other quantum concepts into a novel: Quantum mechanics is most apparent and influential in systems that are small, cold, and isolated. Novelists tend to prefer their stages large, their action hot, and their characters interactive.

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That mismatch is overcome in Ian McDonald’s 2007 novel Brasyl. Set in the Amazon jungle in 1732, Rio de Janeiro in 2006, and São Paulo in 2032, the novel hinges on Hugh Everett’s many-worlds interpretation of quantum mechanics.

Everett devised the interpretation in 1957 to circumvent the unpalatably probabilistic nature of the orthodox “Copenhagen” interpretation. According to Everett, observing a system doesn’t force it into one of its many possible states. Rather, observing a system forces it into all of its many possible states, creating for each of them a new and parallel universe.

Brasyl prominently features another manifestation of quantum mechanics: quantum computation, which by 2032 has become not only possible but also dangerous. (I won’t say why, lest I spoil the plot for you.)

I suspect McDonald found the many-worlds interpretation attractive because, unlike other quantum manifestations, it plays out in the macroworld, if only an imaginary one. Quantum computation, however, remains confined to small isolated systems. But to work, it must scale up—by 2032, if McDonald is correct.

Charles Day

Physicists as neuroscientists and vivisectors

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Presented for the first time with a human’s internal organs, an alien neuroscientist might not grasp right away that the brain is the seat of human consciousness.

Outwardly, a brain looks somewhat like other large, blobby organs. And unlike a computer’s central processing unit, the brain’s ability to calculate, imagine, and perform other tasks resides not in a few thousand neatly arranged and simply connected components but in 1011 interconnected brain cells that come in just two broad types—neurons and glial cells.

As for determining how the brain works, the alien neuroscientist would probably do what human biologists do: try to find out how the brain cells’ operation, organization, and connectivity manifest consciousness.

The tools and techniques available to alien neuroscientists are unknown. Human neuroscientists, however, are using an increasingly sophisticated set of tools, some of which physicists devised. Physicists are also engaged in interpreting data gathered from brains and neurons.

A recent paper in Nature exemplifies both trends. Michael Long and Michale Fee of MIT and Dezhe Jin of the Pennsylvania State University built and deployed tiny sensors in the heads of male zebra finches that recorded neural activity as the birds sang.

Long, Fee, and Jin started their paper by noting that complex behavior is possible because of the brain’s ability to step through a sequence of neural states. A male zebra finch’s song, being made up of recognizable repeated motifs, is one such complex behavior and is among the easiest to study.

Neuroscientists already know which parts of the bird’s brain control song. The question that the three scientists set out to answer was how the neurons that control singing fire in the correct sequence.

Two models have been proposed to explain the sequencing. In the synaptic chain model, the individual neurons responsible for each note (not quite the right word, but it will do) are linked to each other head to toe—or dendrite to axon—in a chain.

In the ramp-to-threshold model, the neurons lie next to each other in the same sequence but aren’t in direct, synaptic contact with each other. Rather, they fire in sequence when a wave of excitatory or inhibitory stimulus washes over them one after the other.

The ramp-to-threshold model’s wave would show up as a change in membrane potential from one neuron to the next. The sensors implanted in the finches didn’t record such a change—quite the opposite, in fact. The membrane potentials of the neurons remained constant when the finches sang their strings of notes, supporting the synaptic chain model.

Biophysical ethics

For the experiment to succeed, the finches had to be happy enough to sing. Evidently, the implantation and operation of the recording devices was not too traumatic for them. The finches were, however, killed after recordings were made. To be sure they had recorded signals from the correct neurons, the experimenters removed, sliced, and wired up the finches’ brains.

I have no reason to suspect that the finches suffered during the experiment. The paper’s methods summary includes the line, “All animal procedures were reviewed and approved by the MIT committee on animal care.”

However, despite the line’s reassuring tone, I was unable to find out what criteria the committee applies to evaluate experiments on live animals. MIT’s division of comparative medicine, which administers the criteria, doesn’t make them publicly available on its website.

I was also unable to find any statement about the ethical treatment of animals issued by two professional organizations that biophysicists in the US belong to: the Biophysical Society and the American Physical Society’s division of biological physics. Given that US labs and universities, such as MIT, have committees that oversee animal welfare, it’s not necessary, for the animals’ sake, that the two societies have any policy on experiments on animals.

It might, however, be desirable for the humans’ sake. If I were a biophysicist like Long, Fee, and Jin, trying to figure out how brains work (or don’t work in the case of brain disorders), I’d like to belong to an organization that officially values the welfare of zebra finches and other lab animals.

Charles Day

Better living through science

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Two weeks ago I received a free book through the mail. Written by Mark Frary and published by Rodale Books, the book bore the promising title Better Living Through Science: The Basic Scientific Principles You Need To Solve Every Household Conundrum. I’d forgotten about the book until yesterday when Kate, a communications assistant at Rodale, sent me an e-mail saying she’d love to talk to me about my plans to cover it.

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Physics Today doesn’t routinely review books like Frary’s. The magazine’s books editor prefers to devote his limited pages to titles aimed at the physics community—with good reason. For some of those books, Physics Today is the only publication that provides a review.

But my hunch is that you, the readers of my blog, might want to know more about a book that purports to help you in your everyday lives.

The 142-page book contains an introduction, plus 34 illustrated chapters with titles like How to combat garlic breath, How to win at pool, and How to sail a yacht. Each chapter succinctly describes the science behind the problem and the solution. “This book,” writes the author in the introduction, “explains things in an easy-to-understand manner that can be enjoyed by anyone, no matter what grades you got back in high school.”

If you’re a scientist like me, you’ll probably find the book offers a mix of things you already know or could easily deduce and things you don’t know. The chapters on throwing balls, stopping cars, and other applications of Newtonian mechanics didn’t teach me anything new, but I did learn how to remove a red wine stain from clothing (apply a mixture of liquid soap and hydrogen peroxide).

My biggest beef with the book is that it doesn’t live up to its subtitle. I didn’t expect such a short book to discuss “every household conundrum.” But, having outlined 34 quotidian problems, the author could have gone on to explain how to approach solving all the others.

According to a much-quoted Australian aboriginal proverb, “The more you know, the less you need.” Frary’s solutions, most of which don’t require special tools, exemplify that piece of folk wisdom. But his omission of a general discussion of the scientific method brings to mind an addendum to the proverb: “The more you understand, the less you need to know.”

Charles Day

Science and nuclear disarmament

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I spent Monday morning at the Washington, DC, headquarters of the American Association for the Advancement of Science. The event that drew me there was a symposium entitled “Science and Nuclear Disarmament: Progress and Challenges.” Its sponsors were the AAAS and the Japan Society for the Promotion of Science (JSPS).

Scientists continue to devise new weapons, nuclear or not. When Joseph Rotblat accepted the 1995 Nobel Peace Prize, he quoted Solly Zuckerman, who was chief scientific adviser to the British government from 1964 to 1971:

When it comes to nuclear weapons . . . it is the man in the laboratory who at the start proposes that for this or that arcane reason it would be useful to improve an old or to devise a new nuclear warhead. It is he, the technician, not the commander in the field, who is at the heart of the arms race.

Rotblat worked on the Manhattan Project and was among several physicists who campaigned against nuclear weapons. He, Albert Einstein, and others argued that using nuclear weapons was inhumane.

At Monday’s symposium, I learned of another, perhaps more subtle argument: The possession of nuclear weapons by a few countries is intrinsically unstable and inevitably leads to a nuclear arms race.

According to one of the symposium’s speakers, Michiiji Konuma of Keio University in Tokyo, the orignators of the argument were Japan’s first two Nobel laureates: Hideki Yukawa and Sin-Itiro Tomonaga. Konuma didn’t cite any references, but it’s not hard to imagine a paper by the two imaginative theorists. In it you’d find the world’s nuclear arsenals and security concerns represented by dynamical equations that, when analyzed, are revealed to have no stable solution.

Another speaker, George Perkovich of the Carnegie Endowment for International Peace, argued that a world without nuclear weapons makes sense from a geopolitical point of view. Countries without nuclear weapons will always find it difficult to accept that only a few countries—the current count is nine—get to have the weapons and tell the rest of the world to forgo them.

Some nuclear-armed countries would also resist multilateral nuclear disarmament because their conventional forces are weaker than those of their perceived rivals. The US and Russia have more or less the same number of nuclear warheads. But the US has more conventional forces at its disposal than Russia does and outspends Russia on military hardware and personnel by 17 to 1. In a world without nuclear weapons, the US would be even more predominant.

Thomas Schelling of the University of Maryland noted that he hasn’t yet seen a thorough and comprehensive analysis of whether a world without nuclear weapons is stable—or even desirable, given the ease with which nuclear weapons can be manufactured. The lack of analysis reminded him of the early stages of the cold war. It took a decade, he said, for the US to recognize the strategic imperative of making sure that its nuclear arsenal be invulnerable to a surprise attack.

Hearing about nuclear weapons is gloomy. Fortunately, an uplifting note came from the symposium’s cohost and first speaker, Hirotaka Sugawara, who directs JSPS’s Washington office. He challenged physicists to devise ways to detect and thwart nuclear weapons:

The nuclear bomb is a product of “devil’s work” by physicists. If the tragedy of Hiroshima and Nagasaki should be repeated again somewhere, sometime by someone, physicists should seriously consider contributing to “God’s work,” which is to nullify the nuclear bombs.

Sugawara acknowledged that the goal would be dificult. But, to quote another physicist, Phil Anderson, about another unmet goal, understanding high-Tc superconductors, “Since when did physicists stop working on something because it’s hard?”

Charles Day

Superchiral electric fields, beer, and coffee

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Some new techniques and ideas are so interesting and potentially important that their inventors don’t wait to prove they’re useful before writing a paper. Instead, after describing the ground-breaking work, the inventors outline possible applications that they and others might one day realize.

The delay between invention and application can be brief. In April 2003 I wrote a news story about the creation of precisely timed bursts of extreme UV light that last a few hundred attoseconds (10−18 s). Within a year, one of the inventors, Ferenc Krausz, had used the technique to probe the motion of electrons inside neon atoms on timescales shorter than the time it takes the electrons to orbit the atoms.

Krausz was applying his own technique. This morning I encountered a freshly published paper in Nature Nanotechnology, which, if taken at face value, suggests that its authors, Glasgow University’s Malcolm Kadodwala and his collaborators, implemented someone else’s idea within six months.

The idea was published in the 23 April issue of Physical Review Letters. Harvard University’s Yiqiao Tang and Adam Cohen used James Clerk Maxwell’s famous equations to identify electromagnetic waveforms whose degree of chirality, or handedness, is stronger than that of left- or right-handed circularly polarized light. Such light, Tang and Cohen proposed, could serve as a sensitive probe of amyloid fibrils, viruses, and other biomolecular aggregates whose constituents are themselves chiral.

Although I can’t be sure, I’m guessing that Kadodwala or one of his colleagues read Tang and Cohen’s paper and sprang into action. In the introduction of the Nature Nanotechnology paper, Kadodwala writes:

Recently, it has been postulated that under certain circumstances superchiral electromagnetic fields could be produced that display greater chiral asymmetry than circularly polarized plane light waves. We have realized that such superchiral electromagnetic fields are generated in the near fields of planar chiral metamaterials (PCMs), which can greatly enhance the sensitivity of a chiroptical measurement, enabling the detection and characterization of just a few picograms of a chiral material.

Kadodwala and his coauthors go on to describe fabricating a PCM, whose periodic features are electrically conducting and of the same few-hundred-nanometer scale as UV and visible wavelengths.

Illuminating the PCM excites plasmons, thereby generating short-range superchiral light. When Kadodwala’s team immersed the PCM in a solution of chiral molecules, they detected strong, telltale resonances whenever the chirality of the PCM matched that of the molecules—just as Tang and Cohen had predicted.

It’s possible that Kadodwala really did find out about Tang and Cohen’s idea by reading their paper. One of the marvels of modern science is how conveniently papers are disseminated.

On the other hand, it’s just as conceivable—and perhaps more comforting—that members of the two teams met one day at a conference and decided over beer, coffee, or other social lubricant to work together.

Charles Day