Last September the OPERA collaboration posted a preprint whose main finding, if corroborated, would necessitate rebuilding one of the foundations of modern physics: that nothing travels faster than light. Derived by timing muon neutrinos on a 732-km journey from CERN in Geneva, Switzerland, to Gran Sasso, Italy, the result provoked a range of reactions and a flurry of media coverage.

Although I can’t be sure, I think most physicists were skeptical of the OPERA result. Other physicists leapt at the chance to apply their imaginations to deriving theoretical explanations for the anomalously speedy particles. As for the general public, how they reacted probably depended on their source of news. Britain’s BBC Radio 4 was careful to emphasize the provisional nature of scientific findings. The New York Times, however, was more excitable. Under the title “Tiny neutrinos may have broken cosmic speed limit,” Dennis Overbye’s story began:

Roll over Einstein?

The physics world is abuzz with news that a group of European physicists plans to announce Friday that it has clocked a burst of subatomic particles known as neutrinos breaking the cosmic speed limit—the speed of light—that was set by Albert Einstein in 1905.

If true, it is a result that would change the world. But that “if” is enormous.

On Wednesday the world learned that the OPERA result could well be spurious. Among the possible explanations for the neutrinos’ early arrival at the end of their journey is an improperly screwed-in fiber optic cable that connects a GPS receiver and a computer.

In retrospect, it looks as though the OPERA researchers posted their results prematurely—that is, before they’d thoroughly checked their equipment. After all, it was the OPERA team that discovered and disclosed the possible problem with the loose cable. Some particle physicists now worry that their field appears ridiculous. If only the OPERA team had waited, they say.

I first heard of the OPERA results when I was on vacation in Northern England. My reaction was complete skepticism. I’m not a particle physicist, but I do know that neutrinos are hard to detect and that the precision needed to time their flight is high. What’s more, Albert Einstein’s theory of special relativity, which sets the ceiling on a particle’s speed at c, has passed every experimental test.

My initial skepticism appears vindicated in the light of yesterday’s revelation, but was it entirely justified? The news about the faulty cable broke on the 380th anniversary of the publication in Florence of Galileo Galilei’s Dialogue Concerning the Two Chief World Systems. The title’s two systems are the Copernican and Ptolemaic models of the solar system. In the book, characters called Salviati and Simplicio make the case, respectively, for Copernicus and Ptolemy before a character called Sagredo.

Salviati wins over Sagredo to the Copernican camp on the strength of his appeal to observational evidence and reason. But Salviati also argues in favor of Galileo’s physically erroneous explanation for Earth’s tides. Presumably, Galileo hoped the readers of his Dialogue would be open to both ideas: the Copernican system, which turned out to be right, and his tidal theory, which turned out to be wrong.

Physicists should be skeptical of grand claims that overturn established and sometimes cherished notions. But they should also be open-minded enough to recognize the possibility that they might be wrong. In “The Nobel laureate versus the graduate student” (Physics Today, July 2001, page 46), Donald McDonald recounted John Bardeen’s opposition to then graduate student Brian Josephson’s prediction that a supercurrent could tunnel through a thin layer of insulating material. Bardeen’s objections hinged on Josephson’s treatment of electron–electron correlations in the insulator. He withdrew them graciously when experiments vindicated his former adversary.

Metabolic cycles, gene expression, and other biochemical pathways are natural fodder for the network theorist. Like the internet, airlines’ route systems, and power grids, biochemical pathways contain branches and nodes. And like those manmade networks, biochemical pathways are complex, especially when you include their myriad regulatory checks and balances.

Despite that affinity, the application of network theory to biochemical pathways is relatively recent. Yesterday at the annual meeting of the Biophysical Society in Baltimore, Hawoong Jeong of the Korea Advanced Institute of Science and Technology noted that in 2000 only a handful of “network biology” papers appeared. Last year, he said, the number was around 1800.

Jeong made his observation at a session entitled “Contributions of Network Theory to Biology.” The first speaker and chair of the session was Sergei Maslov of Brookhaven National Laboratory. Maslov’s talk nicely exemplified one of those contributions: to make sense of the pathways’ daunting complexity.

Maslov and his collaborators look at, among other things, protein–protein interactions. In yeast cells, there are around 2000 different kinds of proteins. Those proteins interact with each other and with other molecules, including DNA and RNA.

Fully 80% of yeast proteins are connected in one giant network, whose scale-free topology resembles those of human social networks. Indeed, the median degree of separation of one yeast protein from any other protein in the network is the same as Kevin Bacon’s from any other actor: six.

The internet’s scale-free topology ensures myriad paths for information to flow from one node to another. But, noted Maslov, being scale-free is not obviously an unalloyed benefit to biochemical pathways. Unlike the internet, a biochemical pathway lacks the means to redirect traffic if one node malfunctions. Undesirable perturbations and interactions can spread.

One kind of interaction that may be harmless or undesirable is that between a protein and other proteins that don’t belong to its habitual pathway. In a cell containing N proteins, the rate of specific, pathway interactions is proportional to N, whereas the rate of nonspecific, off-pathway interactions is proportional to N².

In general, cells need N to be high enough to ensure their proteins can carry out their specific jobs efficiently but not so high that proteins waste too much of their time in nonspecific interactions. In a series of papers, the latest of which appeared last month, Maslov and his collaborators have applied network theory to analyze protein–protein interactions.

Among their conclusions: The abundance and concentration of proteins in cells and in two kinds of cellular compartment, mitochondria and nuclei, are more than high enough to ensure efficiency. In fact, according to Maslov and his colleagues’ calculations, proteins spend about 80% of their time interacting with proteins that belong to their pathways.

The remaining 20% of the time that proteins spend in the company of off-pathway partners might not be a complete waste. Just as Kevin Bacon and other humans benefit from meeting new people, nonspecific protein–protein interactions might promote evolutionary adaptation.

Charles Day

In Swann’s Way, the first volume of Marcel Proust’s 1.5-million-word novel In Search of Lost Time, the narrator recalls the church in his hometown of Combray. After describing the church’s tapestries, crosses, and other treasures, the narrator muses that

all these things made of the church for me something entirely different from the rest of the town; a building which occupied, so to speak, four dimensions of space—the name of the fourth being Time—which had sailed the centuries with that old nave, where bay after bay, chapel after chapel, seemed to stretch across and hold down and conquer not merely a few yards of soil, but each successive epoch from which the whole building had emerged triumphant.

At the end of act I of Richard Wagner’s 5.5-hour opera Parsifal, Gurnemanz, the oldest of the Grail knights, leads Parsifal, who’ll later become the youngest, from the forest and into the hall of Monsalvat Castle, telling him,

You see, my son, time
Changes here to space.

Should physicists be surprised that a writer and a composer should have appeared to grasp something like Albert Einstein’s notion of spacetime? I don’t think so. Of all the weirdnesses in Einstein’s special relativty—differentially aging twins, shrinking yardsticks, mass-increasing projectiles—spacetime seems the most natural and palatable.

When I first encountered spacetime, as a physics undergraduate at Imperial College London, I remember thinking that the presence of ct as the fourth coordinate alongside x, y, and z made clear, readily acceptable sense. In retrospect, I perhaps should have thought more deeply about the concept.

But you don’t have to be a giant of civilization like Proust (shown here), Wagner, and Einstein or an undergraduate physicist as I was to appreciate the dimensional kinship of space and time.

Yesterday I learned from my wife that a careful gardener sees her plot in four dimensions. She plants her flowers and vegetables based on where and when she wants them to appear.

Charles Day

One of the most exciting themes running through condensed-matter physics is the close mathematical association between how electrons behave in certain crystals and how particles behave in certain field theories.

I first noticed the association in 2005 when I wrote a news story about topological quantum computing. The basic currency of quantum computation, topological or otherwise, is the qubit. Until it’s read out, a qubit exists in a superposition of states that encompasses not only the classical bit’s 0 and 1 but also nonclassical states in between. If you could operate on k entangled qubits, a potentially vast space of 2^k values becomes available for computation.

To work, a quantum computer must protect the qubits’ all-important superposition and entanglement from heat, vibration, stray electric fields, and other environment intrusions—at least for long enough to perform a calculation step. Topological qubits are more robust against those intrusions than other qubits because their entanglement abides not in their geometric disposition, which can be perturbed by moving just one qubit, but in their topological disposition, which can’t.

Field theory, to my surprise, was involved in both the conception of topological computing and in ideas for its implementation. Solving a certain class of problems, which includes optimizing a traveling salesman’s route, is mathematically equivalent to calculating a topological invariant that characterizes the tangledupness of a three-dimensional knot. The invariant looks like a certain field theory in two spatial dimensions plus time, which, it turns out, might describe a certain state in the fractional quantum Hall effect (FQHE).

The upshot of that chain of mathematical resemblances is that you can, in principle, solve the traveling salesman problem and others by manipulating FQHE quasiparticles in a sliver of gallium arsenide. Researchers in labs in the US and elsewhere are trying to build an FQHE computer.

Skyrmions and Majorana fermions

Since writing about topological quantum computing, I’ve encountered other areas in which mathematical structures from field theory appear in condensed-matter contexts. Ettore Majorana’s 1932 description of the neutrino could turn out to fit the quasiparticles in superconducting strontium ruthenate, even if it proves inapt for neutrinos themselves. Skyrmions, the elementary particles that Tony Skyrme postulated in 1962 to account for the diversity of baryons, resemble vortices observed in manganese silicide.

What do these and other resemblances mean? They could be manifestations of shared symmetries. In two dimensions, it’s mathematically possible for a particle to be neither a fermion nor a boson but something in between—an anyon, as Frank Wilczek called the possibility. If, as some theorists assert, certain FQHE quasiparticles are anyons, shared symmetries would be confirmed, but perhaps nothing else more profound.

On the other hand, the resemblances could, as Xiao-Gang Wen proposed, indicate that electrons, photons, and other particles in the universe emerge from elementary structures whose mathematical origin lies in condensed-matter physics, not string theory.

Whether they connote shared symmetries or something deeper, the mathematical resemblances between condensed matter and field theory have proven fruitful. Yoichiro Nambu won his share of the 2008 Nobel Prize in Physics for discovering spontaneous symmetry breaking in field theory. The path to that discovery lay through previous work by Philip Anderson and others on superconductivity.

Charles Day

Thanks to Ravi Chathuranga and Maire Evans, fans of Physics Today‘s Facebook page, for suggesting I tackle theories of everything.

For May’s issue of Physics Today I wrote a news story about a clever biophysical experiment by Aurélien Roux of the Curie Institute in Paris and his collaborators.

Roux wanted to find out how the protein dynamin forms a pouch of cell membrane that projects into the cell during a process called endocytosis. At the start of endocytosis, the pouch—termed a vesicle—is open to the cell’s exterior. In the final step, the neck of the vesicle, which is squeezed by a collar of polymerized dynamin, is pinched off, trapping the vesicle and its contents inside the cell.

Roux’s experiment popped back into my mind this morning when I encountered a paper in the Proceedings of the National Academy of Sciences entitled “Soap-Film Möbius Strip Changes Topology with a Twist Singularity.” Roux had told me that the mechanism by which the cell membrane changes its topology as the vesicle closes is unknown. Curious, I wondered if the new Möbius strip paper was relevant to endocytosis.

The paper was written by Raymond Goldstein, Keith Moffatt, and Adriana Pesci of the University of Cambridge and Renzo Ricca of the University of Milano-Bicocca. Here’s how it begins:

In an elegant article in 1940, the mathematician R. Courant laid out a number of fundamental questions about surfaces of minimal area that could be visualized with soap films spanning wire frames of various shapes. He noted that when the frame is a double loop it can support a film with a Möbius strip topology. Pulling apart and untwisting the loop leads to an instability whereby the film jumps with change of topology to a two-sided solution.

Goldstein and his coauthors point out that despite progress made on Courant’s questions, one stands out unanswered: What is the process that takes a one-sided film to a two-sided one?

In fact, if Goldstein’s paper is correct, that question is no longer unanswered. With a combination of high-speed videography and mathematical analysis, the Cambridge–Milan team demonstrates that the topological transition proceeds via a twist instability at the boundary wire. Clicking on the image of the Möbius soap film will take you to a video of the transition—filmed at 5600 frames a second!

I’m not sure whether the Cambridge–Milan team’s paper is directly relevant to Roux’s experiment. Still the team’s approach might be applicable to models of endocytosis. As a science writer, I found the possibiity of a link between the two papers intriguing enough to write what, I hope, is a not uninteresting blog post.

But if you’re a scientist, not a science writer, spotting possible links between diverse experiments and theories could be a source of inspiration and future projects. If you don’t already do so, read widely, attend seminars in topics outside your immediate field, and keep an open mind.

Charles Day

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

This morning I visited Wikipedia, typed the date, 12 August, into the search box, and looked for events that I could write about for Physics Today‘s Facebook page. Today happens to be Erwin Schrödinger’s birthday, so I picked him.

It’s also the 67th anniversary of the Philadelphia Experiment. According to conspiracy theorists, in 1943 the US Navy tested a device at the Philadelphia Naval Shipyard that rendered the USS Eldridge, a 1240-ton destroyer, completely invisible.

Like all good conspiracy yarns, the Philadelphia Experiment features real people, among them the philosopher Bertrand Russell and an SS-Obergruppenführer called Hans Kammler, who supposedly led a rival Nazi project. But what I wasn’t expecting was the key role played by Albert Einstein’s unified field theory.

In 1950, five years before the Philadelphia Experiment was “uncovered,” Einstein wrote an article for Scientific American about his attempts to unify the forces of nature in one grand unified theory. Devising such a theory eluded Einstein—and it continues to elude his successors—but if the theory were found, it could more or less plausibly describe the means to locally distort spacetime in such a way that the paths of photons would be bent around a massive object—for example, a warship.

It’s quixotic in the extreme to base a conspiracy, which purports to be real, on a solution to what is perhaps the most challenging problem in all of science. A less ambitious theoretical goal would have made for a stronger, more convincing foundation for conspirators.

Science fiction writers, on the other hand, are free to appropriate any theory for their work. Wormholes, tachyons, Hugh Everett’s many-worlds interpretation of quantum mechanics, and other as-yet-unproven concoctions have made their way into science fiction. And their presence, paradoxically, makes the stories seem more real.

Charles Day