Cocktail Party Physics

run, baby, run

Shhh! Try to keep it down to a low whisper, will ya? Jen-Luc Piquant is currently lost deep somewhere in the final Harry Potter book, having waited patiently for her turn -- and somehow avoided all the online spoilers in the process, no mean feat by now. (Anyone considering trying to ruin the surprise for her should be forewarned: she is ruthless when wreaking her revenge. When you least expect it, she will emerge out of Cyberspace via your computer monitor, just like the ghoulish Samara in the horror flick The Ring, who comes oozing out of the TV to claim her victims. Better yet, she'll send Oscar the Cat, a.k.a., the Feline Harbinger of Death, to sit and stare at you expectantly with those unblinking almond eyes. Aieee!) While waiting for myself and Future Spouse to finish our respective readings, Jen-Luc perused the biology of Harry Potter (courtesy of the Biology in Science Fiction blog) and re-read Roger Highfield's entertaining The Science of Harry Potter to keep herself in that Rowling frame of mind. 

Certain skeptical types might assume that it is pointless to look for science in a children's fairy tale, but that just demonstrates an overly literal mind or limited imagination, in our humble opinion. It's all a matter of perspective; as Highfield ably demonstrates in his book, quite a bit of cutting-edge modern technology is, in its own way, quite magical -- electronic paper, for example. And just this week, Wired reported that DARPA -- described as "the Pentagon's way-out research arm" -- wants to design a software suite that can help battlefield commanders predict the future. Seriously. They're developing a "digital crystal ball" capable of foretelling how any given military mission will turn out beforehand. Professor Trelawney would be so proud. And maybe Oscar the Cat can help with the divination aspects.

There's been another Oscar in the news this week: Paralympic champion sprinter Oscar Pistorius, a.k.a. "the Blade Runner," a double-amputee since he was a baby in South Africa. Pistorius was born without fibulae in both of his legs, which were amputated halfway between his knees and ankles just before his first birthday. He's always worn prosthetics, taking his first steps on fiberglass pegs, and has always been highly athletic, playing rugby, water polo, tennis, even wrestling before taking up track and field after suffering a serious injury in rugby. He's known for refusing special treatment, even perfectly legal ones, like handicapped parking spaces. He says his motto has always been, "You're not disabled by the disabilities you have, you are able by the abilities you have."

[UPDATE: There's a fascinating post up at my new favorite blog, Neurophilosophy, on the discovery of the 300o-year-old prosthetic foot. Check it out!]

That motto has served him well thus far. Not yet 21, Pistorius has racked up an impressive string of titles, and is the current Paralympic double amputee world record holder in the 100, 200 and 400 meter events. A few weeks ago, he made his international debut against the world's top able-bodied runners by running the 400 meter event at the Norwich Union British Grand Prix in Sheffield, England. He didn't fare very well, given wet conditions; he placed seventh in a field of eight, and was ultimately disqualified for running outside his lane.

Now Pistorius has set his sights on qualifying for the 2008 Summer Olympics in Beijing -- and therein lies the controversy. It's not unprecedented: according to a May 15 article in the New York Times, there have been at least three disabled athletes who have competed in the Summer Olympics: an American gymnast with a wooden leg (George Eyser); a paraplegic archer from New Zealand (Neroli Fairhall); and a legally blind American runner (Marla Runyon, who competed in the 1500 meters at the 2000 Summer Olympics in Sidney). There's never been an amputee competing in an Olympic track and field event; Pistorius wants to be the first.

The sticking point is whether his prosthetics give him an "unfair advantage" over able-bodied athletes. "But the man is a double amputee!" you may well exclaim. I certainly did. Nonetheless, that's the gist of objections, and the International Association of Athletics Federation (IAAF) is still mulling over the issue before deciding whether or not Pistorius can compete. (There's very little question of his qualifying.) They throw around a lot of impressive scientific jargon when discussing his case, talking about measuring the maximum amount of oxygen his body uses in one minute, per kilogram of body weight (known as an athlete's VO2 max), or assessing the mechanical efficiency of his stride using a dizzying array of different techniques, including force plates and 3D kinematics. They've already used high-definition cameras to film his running motion.

Just what's so special about those prosthetics? These days, Pistorius runs on a pair of high-tech prosthetic limbs made out of carbon graphite, called Cheetahs, since the J-shaped design mimics an actual cheetah foot. They make a telltale "snick-snick-snick" sound on the asphalt as he runs -- a sound competitors have come to dread; one fellow runner said he felt like he was "being chased by a giant pair of scissors."  They're also a bit longer than natural limbs, which some believe enable him to cover more ground with every stride -- those naysayers include single-amputee Paralympic athletes Marlon Shirley and Brian Frasure, both of whom were beaten by Pistorius this past May at the Paralympic competition in Athens. (Jen-Luc thinks this sounds a bit like a case of sour grapes.) That's not something Pistorius can help: the Cheetahs must be longer than biological legs, to compensate for their imperfect biomechanics. Also, the design means Pistorius runs pretty much on tiptoe.

In fact, the more I read about the objections, the more it sounds like people are basing their objections on perception rather than solid science. Any cited perceived advantage is easily outweighed by everything else that Pistorius must overcome. The Cheetahs are not without their drawbacks. For instance, Pistorius doesn't experience the lactic acid buildup that plagues able-bodied athletes, but they don't have to contend with the possibility that the carbon in an artificial limb will snap at an inopportune moment, sending Pistorius to the ground in a movement that more closely resembles a skier wiping out on the slope than a runner stumbling.

He's a slow starter, since he needs to exert more energy to get moving out of the starting blocks that his able-bodied competitors; unlike them, his later stage of a race is his strongest and fastest. For that reason, he'll never be as strong in the shorter 100-meter event; he really shines in the longer 400-meter event, because there he has time to find his rhythm after the inevitable shaky start. As the Sheffield competition made clear, if it's raining, he has trouble with traction. And a stiff, strong wind can blow his legs sideways. Most runners lose speed coming out of a turn, but Pistorius might actually gain energy -- the downside is that once the Cheetahs get going, they can be really tough to control.

Most damning of all is what you find when you crunch the numbers of energy return for Pistorius' artificial limbs. The Cheetahs rely on a passive spring to absorb energy as the foot lands, returning energy to propel the next step forward -- pretty much the same biomechanical concept behind how an able-bodied person walks. but the Cheetahs can't generate anywhere near the propelling force of a biological limb: landing on a human foot in a running stride has a 241% energy return, thanks to the contraction of leg muscles, compared to a roughly 82% spring efficiency for a passive prosthetic foot like that on the Cheetahs. So Pistorius actually has to work at least 30% harder than his  able-bodied competitors to compensate for not having the usual collection of muscles, tendons, ligaments, joints and bones -- and all that power must come from his hips, producing a weird, slightly waddling stride as he runs. The field of prosthetics hasn't yet come close to matching Mother Nature's design.

Pistorius has plenty of supporters, not just detractors. Hugh Herr, director of MIT's Biomechatronics Group and himself a double amputee, thinks Pistorius has "a distinct disadvantage" in track and field: "He's just really fast." Robert Gailey, an associate professor in the University of Miami's department of physical therapy, agrees with that assessment: "There is no science that he has an advantage, only that he is competing at a disadvantage," he told the New York Times. Imagine running on stilts: that's essentially what Pistorius is doing. He's just really, really good at it because he's been walking and running on stilts since birth. His handlers are fond of saying that anyone who thinks having carbon-fiber legs will automatically make them a faster sprinter, should have the operation and meet them at the track.

True, he does have an innate advantage over Shirley and Frasure, both of whom still have one natural leg. Mixed leg sprinters aren't as smooth or fast, according to Gailey, because they lose energy to vertical movement by pistoning up and down. Pistorius might waddle a little, "but his gait has a circular smoothness." Short of amputating their other legs, Shirley and Frasure will just have to accept this innate shortcoming, or find some other means of compensation.

Pistorius isn't some futuristic cyborg, just a gifted runner with two artificial limbs. It's easy to confuse the passive prosthetic limbs used by Pistorius with more active models using bionics and robotics. For instance, Herr has developed a computer-controlled robotic ankle giving an amputee a faster and more natural gait, as well as the Rheo Knee, which has a microprocessor and numerous sensors to allow it to adapt to changes in speed, load, and uneven terrain. The motor generates extra power if the user is walking uphill, while downhill, the ankle uses a brake-like device to dissipate some of the energy. The robotic ankle is powered by a rechargeable battery capable of storing sufficient power for a walk of several miles. Similar work on an artificial foot and ankle that can adapt to changing terrains and walking speeds is being done at Northwestern University. (At the very cutting edge is Cyberkinetics in Massachusetts, which implanted 100 electrodes onto the motor cortex of a paralyzed man that enables him to operate a computer or move an artificial arm using just his thoughts. Yikes!)

Despite all the technological bells and whistles, such devices still aren't as strong or powerful as natural limbs, and they don't respond automatically to signals from the brain, because they aren't linked directly to the central nervous system. But someday they might be. In so, then those types of prosthetics conceivably could confer an unfair advantage on a disabled athlete in the not-too-distant, according to Gailey -- which might be why the IAAF is concerned about setting a future precedent. Nobody wants to see track and field turn into the massive global embarrassment that has become this summer's scandal-plagued Tour de France. "If there are no constraints placed on what technology can be used, at some point there will be an advantage," Herr admitted to the New York Times; in fact, that's the ultimate goal of such research.

Pistorius' success is pushing hard against the traditional boundaries separating disabled and able-bodied athletics, and it's raising a lot of questions and making a lot of people uncomfortable in the process. Nor is the issue likely to go away: a single amputee named Jeff Skiba competed in the US indoor track and field championships last year. The IAAF recently amended its competition rules to ban the use of "any technical device that incorporates springs, wheels, or any other element that provides a user with an advantage over an athlete not using such a device." They claim this is not intended to target Pistorius, merely to better define what constitutes therapy versus an enhancement.

Even the head of the organization's medical and anti-doping commission, Juan Manuel Alonso, admitted to the New York Times that "There is no real grounds to say he [Pistorius] should not be allowed to compete" in the Olympics. I say, enough already. Let the man compete. He's had to overcome enough. Don't make him a poster boy for futuristic technology he's not even using. Yet.

ADDENDUM: Cocktail Party Physics will be hosting the next Philosophia Naturalis blog carnival, slated for April August 15th. Jen-Luc Piquant expects to be finished with Harry Potter any moment now, and is quite keen to begin sifting through submissions. So if you've got anything, be sure to send it along to her at JenLuc@gmail.com.

shiny things

Like many people, I have a fondness for shiny things, whether we're talking about ideas or actual material baubles -- anything cool, colorful, or especially eccentric or interesting is likely to catch my magpie-minded attention, collected, and stored away for future reference. One must decorate the metaphorical nest, after all. For instance, I used to have a set of ammonite jewelry (sadly misplaced in the move to LA), and treasure my butterfly pendant made of actual enameled butterfly wings. (Shhhh! nobody tell PETA!) My good friend Peri is particularly fond of opal jewelry -- especially when presented to her by an attractive suitor, accompanied by fine wine and lobster thermidor over candlelight and a single orchid. (Jen-Luc Piquant thinks this is the very least a potential suitor could offer and commends Peri for adhering to higher standards.)

Peri has some excellent company sharing her taste in gemstones. Queen Victoria adored all things opal, often giving them as wedding presents, and was thrilled when Australia (then part of the British empire) turned out to be an area rich in opals. In the Middle Ages, according to Wikipedia, "Blonde women wore opal necklaces to protect their hair from losing its color." They didn't have L'Oreal back then. They were also believed to be beneficial to eyesight. Pliny, the Roman historian, believed that opal combined "the beauty of all the other gems."

In physics circles, opals (and butterfly wings, for that matter) belong to a class of materials known as photonic crystals -- a topic I've covered before, both here and for The Industrial Physicist. Way back in 1887, Lord Rayleigh first studied how light interacted with the simplest form of a photonic crystal: a one-dimensional periodic structure (useful today in things like reflective coatings). It took an entire century to produce 2D and 3D versions, an honor that goes to Eli Yablonovitch and his collaborators, who accomplished the feat in 1991 when Yablonovitch was at Bell Communications Research in New Jersey. They mechanically drilled tiny holes into a block of material now known as "Yablonovite." As expected, the material prevented microwaves from propagating in any direction (a photonic bandgap). And the field exploded, although it took more than a decade to make photonic crystals that blocked near-infrared and visible light.

A short recap on why photonic crystals are so unique: The atoms or molecules in a photonic crystal are arranged in a precise lattice structure, similar to a 3D honeycomb, or an egg carton. Depending on the spacing between those building blocks, this creates a "photonic bandgap": certain frequencies of light are blocked, while others are preferentially let through. There's been a great deal of interest in using photonic crystals as a replacement for the pricey and sometimes toxic dyes used to color clothing or buildings, or even cosmetics. L'Oreal has a line of makeup featuring these iridescent effects, in which the colors only appear when the makeup is applied and exposed to light.

Therein lies one of the issues with manmade photonic crystal films to date: they have been highly dependent on viewing angle. Hold up a sheet of one of those films, and "You'll only see milky white, unless you look at a light reflected in it, in which case certain colors from the light source will be preferentially reflected," says Jeremy Baumberg, a physicist at the University of Southampton in the UK. Change the viewing angle, and the perceived color changes. He thinks that scientists have mistakenly assumed that the same effect was at work in both manmade and natural photonic crystals: the lattice structure causes the light to reflect off the surface in such a way as to produce the perception of color in the human eye, and which color one sees depends on the angle of reflection. But Baumberg says that the natural structures appear to selectively scatter rather than (or in addition to) reflecting the light, more like a diffraction grating.

Look at an opal under a powerful microscope, and you'll see that it's made up of spheres of silica stacked together like the oranges and other spherical fruit on display in our spiffy new Ralph's Fresh Fare grocery store in downtown Los Angeles. (I cringed inwardly in self-recognition at the reference in the linked article to "loft-dwelling yuppies" -- how hath the mighty East Village Bohemian fallen! Then again, there's a lot to be said for not having to step over discarded needles and crack vials strewn about the hallway every morning.) Because those spheres of silica aren't much bigger than the wavelengths of visible light, the stacking acts as a kind of grating. The regularity of the sphere sizes and how precisely they are packed together determines the wavelengths of light that will be diffracted and hence the colors that one sees. Baumberg copied that structure when he set about making polymer opal films. I have a short piece on his work in this week's New Scientist; the original paper appeared in Optics Express, an online open access journal of the Optical Society of America.

Even though it's technically a mineral-based gem, opal is considered to be a "mineraloid" because it doesn't have a truly crystalline structure as science narrowly defines it. Yet that very "imperfection" gives rise to very strong color effects -- stronger than the iridescence produced by manmade films. Figuring that Nature might be onto something, Baumberg used arrays of plastic spheres stacked in three dimensions, rather than the layers used by most researchers doing similar work in the past. (L'Oreal's makeup line, for instance, is made by stacking nanoscale layers of materials like mica or silica, of varying thickness; the thickness imparts the specific color.)

The colors produced by Baumberg's films are much stronger, and far less dependent on viewing angle, than earlier versions produced by other researchers. That's because Baumberg added a twist: he embedded tiny carbon nanoparticles wedged tightly between the spheres, a structure he likens to "cannonballs stacked in rubber." The end result: light doesn't just reflect at the interfaces between the plastic spheres and the surrounding materials, it also scatters weakly off the embedded nanoparticles. A similar effect makes the sky look blue, except the effect is enhanced by embedding the particles inside the lattice structure of a photonic crystal. You need both effects, it seems, to get the optical properties you need for these polymer opal films.

In fact, Baumberg points out that many mined opals have been "cooked" -- either deep in the earth for millions of years, or by the miners themselves in manmade laboratories -- and that process produces organic nanoparticles around the silica spheres that make up the opal. It's especially pronounced in the orange-y Australian fire opals. (This amazing photograph, by the way, is just one of  many close-up shots of common objects made by Florida State University's Molecular Expressions Website: "Exploring the World of Optics ad Microscopy." I encourage readers to do their own exploring. The opal page is here, but it's a terrific site in general, and one could spend hours -- I certainly have -- perusing its varied pages.)

Many opals just look whitish without this cooling process. "In trying to glean the secrets from the miners who extract these gems, it seems clear that the 'recipes' are exactly of enhancing the scattering that underpins the effect we've shown," Baumberg told me.

Much like natural opals, you can change the resulting color simply by changing the size of the spheres, so it's another example of a "tunable" material. For green-orange films, Baumberg and his colleagues use 100nm radius spheres. Ergo, it's ideal for practical applications. But you can also tailor the embedded nanoparticles to suit a particular application.

For instance, you can create nanoparticles that react with certain dangerous chemical agents or toxins. This would cause the film to stretch, thereby changing the spacing between the spheres in the lattice structure -- and thus, the color changes, indicating the presence of the target substance. That's why the military is interested in Baumberg's work, among others: the films would be ideal for making sensing patches that could be woven directly into soldiers' uniforms, and could alert them when dangerous toxins are present in the field.

The same effect makes the polymer opal films an excellent candidate for food packaging applications -- the area of interest for Unilever. Imagine being able to look in the fridge and tell immediately whether some perishable food item has gone off: the packaging would change color. The nanoparticles would be tailored to react to whatever happens when food spoils, the film stretches, and the spacing between spheres changes. Use the films to, say, make currency, and you've got a handy anti-counterfeit measure: someone could tell whether a bill was genuine simply by twisting or stretching it to see if it changed color. EADS has something less exotic in mind: they want to use the films to coat the tails of its Airbus craft. Because colors = pretty! For his part, Baumberg's interested in seeing if he can use fibers woven from his new material to make a flexible display.

In fairness, there are other physicists experimenting with "doping" photonic crystals, just to see what happens. Last November, there was a paper in Applied Physics Letters about recent work by a team of Italian and German physicists who have developed a new, flexible fabrication technique for "rewritable" photonic crystal devices. Unlike Baumberg's work, which is focused on more consumer-oriented applications, these researchers are interested in using the devices in optical computing, where photons process information in much the same way that electrons do in our present computers. They take a 2D lattice of tiny pores arranged in a beehive pattern (which is why AIP's public information office dubbed it an "optical beehive"), and insert defects by injecting different materials directly into the pores.

Baumberg has experimented in the past with 2D films for optical chips, and for LEDs, made of very dense glass and semiconductors -- in fact, it's how he got into the field, when Merck asked him about using photonic crystals for optical devices. Such films aren't useful, he says, unless they have a very high refractive index contrast, and are also much more expensive to manufacture when compared to polymer opals, because optical chips simply "can't tolerate disorder in the lattice." The polymer opal applications actually require a certain disorder; the spheres don't need to be perfectly stacked, "in fact, it's better if they are not," says Baumberg. This tolerance for a bit of messiness is the biggest reason that Baumberg's German collaborators at DKI in Darmstadt have been able to mass-produce the films in rolls as long as 100 meters -- the first time scientists have been able to do so and still get materials with such strong color properties, that can be so easily tailored to such a wide range of commercial applications.

In Nature, opals tend to form over millions of years, the result of sandy sediments along the shorelines of seas or oceans depositing silica in some type of fluid solution into cracks in rocks, layers of clay, and even a few fossils. When the silica solidified, some of it turned into opal. While not copying this process exactly, there are some common elements with the approach taken by Baumberg and his German collaborators to make opals. The manufacturing process doesn't involve any advanced lithography or etching, just a couple of simple polymers. They use a kind of directed self-assembly, first growing polystyrene spheres in a flask -- in batches of an impressive 350 kilograms, no less. Once the spheres reach the right size (about 200 nm in diameter), they stop the growth process and irradiate the spheres with UV light to harden them. The spheres are then coated with a sticky outer later of another soft polymer (poly-ethyl-acetate, or PEA, for the curious).

Per Baumberg, the spheres are then "squished" (his word, honestly, it just sounds like something I'd say!) at 150 degrees Celsius. This makes the outer shell runny -- the shell melts, basically, into a fluid, so there are naturally generated shear flows that take place. "All the spheres run over each other and want to line up in a beautiful lattice," he wrote in answer to a hastily emailed query. "Nature appears to favour the spheres lining up together when they flow over each other, but we are [still] trying to understand exactly why."

So now we have lovely natural-seeming photonic crystals, with an imperfect photonic bandgap effect because at this point, all we have are visible Bragg reflections, although the material is both flexible and malleable, changing color as it bends and stretches. Introducing much smaller (less than 50 nm) carbon nanoparticles into the interstices of the lattice structure is the final touch, bringing in the all-important diffraction grating/scattering effect. You maintain the lattice structure, and yet also enhance the desired color effects, resulting in a material that provides strong colors and less dependence on viewing angle.

Who knew that such a seemingly simple gemstone could be so much more than a pretty face? However, while I share Peri's admiration for opal, I also have a soft spot for nacre (a.k.a., mother-of-pearl), particularly of the type found inside abalone shells; it's also produced by pearl oysters and freshwater pearl mussels. The substance is secreted by epithelial cells that make up the mantle tissue of those aforementioned organisms, and it's secreted constantly, deposited onto the inner surface of the shell -- as a means of smoothing the interior, and as a defense against any invading parasitic organisms or foreign objects. When invaders do get in, the mollusk responds by encasing them in successive, concentric layers of nacre, ultimately forming a pearl. (I'm less fond of pearls; maybe it's the lack of iridescence. I needs my bright pretty colors.)

Like opals and other natural photonic crystals, nacre exhibits iridescence, although it doesn't seem to arise from a lattice structure; it's more like bricks in parallel stacked neatly together. Nacre is mostly made of nano-thin layers of calcium carbonate crystal called aragonite, and just as with opals, the iridescence is due to the interference of light as it reflects from the those crystalline layers. A new paper in the July 29 issue of Physical Review Letters sheds some interesting light on the microscopic architecture of nacre and how it might grow, according to a recent article in Physical Review Focus. This in turn, could explain why nacre is so resistant to cracks -- 3000 times more resilient than its organic and crystalline components.

Researchers at the University of Wisconsin, Madison, used a finely tuned, polarized x-ray beam  to investigate the structure. The crystals are shaped like irregular disks and arranged into alternating tablet and scaffold layers. The Focus article describes it as being "a bit like single layers of coins touching at their edges, alternating with sheets of paper." As with Baumberg's polymer opals, Nature's imprecision has a purpose: the Madison group's theory is that because nacre forms  layer by layer, those layers aren't perfectly aligned, although they do tend to form ragged columns that resemble "snaking stacks of quarters." Small holes pierce the layers, and these could be scattered quite randomly rather than being vertically aligned. The resulting structure is more resistant to cracks because the cracks can't propagate as easily -- they keep running into these holes, which serve as crystal boundaries. Considering that nacre forms from the biological processes of living creatures, perhaps it's not surprising that its structure isn't entirely determined by the usual intrinsic properties of crystal growth. (At least that's the opinion of McMaster University's Adam Hitchcock, who's quoted in the Focus article.) 

Thus concludes our lengthy paean to shiny things. We now return to our regularly scheduled deadlines.

what you can't see can hurt you

Back when I was living in NYC's East Village, I headed down Second Avenue on my way home one day, and came upon an amazing sight: the earth had opened and literally swallowed a couple of cars, the tailgates of which were sticking up vertically out of the enormous pothole that had formed in the middle of the asphalt. Second Avenue was closed for almost an entire week to repair the damage. Apparently that portion of the avenue had been unstable for some time, a ticking time bomb just waiting for the right moment to collapse.

I was reminded of that incident yesterday when news broke of a huge steam pipe explosion beneath a street near Grand Central Terminal. This was no minor "exploding manhole cover" (a problem that plagued residents of DC's tony Georgetown neighborhood in 2001/2002). The force of the explosion sent a gigantic "scalding jet of brownish steam toward the sky," according to a report in the New York Times, killing one person and injuring more than 30 others. The steam was accompanied by all kinds of debris: mostly mud and chunks of pavement, hitting the windows of skyscrapers before falling to earth like a very hard rain. (You can see the raw footage here.) The force of the explosion was sufficient to flip over a red tow truck; it landed right smack in the center of the crater.

Terrorism was the first thought to spring to mind for many, but it was really just due to very old pipes (from 1924) under extreme pressure, exacerbated by the introduction of cold water, which caused the pipe to rupture. There have been more than a dozen similar incidents over the last couple of decades, the biggest rocking Gramercy Park in 1989.

A bit of fascinating New York history emerged in the local media coverage. More than one person describing the appeal of the Big Apple has mentioned that New York's streets seem to vibrate with energy -- turns out that is literally correct! The steam pipes are there because steam was once used to power elevators in Manhattan buildings, beginning around 1882. But the demand for steam power decreased sharply with the rising availability of electricity. Today, it's used to spin turbines that generate electricity for Con Edison's plants, after which the steam is piped to large office buildings (among them the Empire State Building), where it provides heating and (by adding compressors) air conditioning. Millions of pounds of steam are pumped beneath the city every hour.

The CEO of Con Edison, Kevin Burke, theorized that recent rainstorms would have surrounded the pipes with cold water, resulting in condensation inside the steam pipe. That's very bad for these old pipes, since steam responds to even slight changes in its environment with a corresponding change in pressure -- ergo, the explosion. (The slang term, apparently, is "water hammer.") And there's 105 more miles of old steam pipes pumping away beneath Manhattan's mean streets, buried close enough together that trouble in one sector could damage a neighboring one. New Yorkers can't see it, but there's big trouble brewing beneath their bustling little feet.

Of course, the explosion and accompanying debris, and related injuries, aren't the only problem. The city's infrastructure is very old; certain materials considered unsafe today were in common usage in the 1920s -- materials like asbestos, a known human carcinogen. The explosion that ripped apart the pavement may have also ripped up the asbestos insulation and dispersed it into the air. Con Ed has been diligently testing the air and the debris for traces of asbestos. Ask a health official and he or she will tell you that no exposure is really safe, but the cancers related to asbestos are usually the result of sustained exposure (over the course of many years) in industrial settings. Just to be on the safe side, those in the vicinity of the blast were urged to wash and have their clothes carefully cleaned.

Still, if we're talking dangerous carcinogens, nothing beats ionizing radiation, especially gamma rays. Just two days before the NYC blast, the north coast of Japan was hit by a powerful undersea earthquake measuring 6.8 on the Richter scale. Nine people died, over 900 were injured, houses were crushed, highways buckled, and collapsed a few bridges along the coast -- all this damage in a supposedly rural area. Far scarier was the report that a "small amount" of radioactive waste had leaked into the Sea of Japan from the Kashiwazaki-Kariwa nuclear plant -- one of the world's largest such facilities. The plant owners, not surprisingly, insisted the leak wasn't a health risk, despite the fact that it wasn't publicly reported for several hours. According to the Los Angeles Times, "Japan's nuclear industry, which operates 55 plants atop some of the earth's most volatile tectonic plates, has a history of covering up accidents."

While I'm a big believer in investing in alternative energy sources, I'll go on record saying that I'm not nuclear power's #1 fan. It's nothing personal; some of my best friends are nuclear physicists. Nor am I hysterical about it; the word "nuclear" does not automatically fill me with fear and dread, because I've learned enough science over the years to understand the realities of the risks involved. Radiation might be invisible to the naked human eye, but there's no reason to freak out over getting an MRI, for example. (Jen-Luc hears that one reason it's called Magnetic Resonance Imaging, despite being based on nuclear magnetic resonance, is that nobody wanted the word "nuclear" to be mentioned.) And I'm a huge fan of nuclear medicine, which has saved far more lives over the years than radiation exposure has killed, I'd wager.

So why am I not a fan of nuclear power plants, despite their potential for reducing our dependence on oil and other fossil fuels? For starters, I just don't buy the argument that it's a "clean" energy source, because the process of creating nuclear energy also creates radioactive waste, which must be stored for decades upon decades in some supposedly safe underground location. That just doesn't meet my criteria for a truly clean energy source. Sorry. A small amount of nuclear power is fine, but our energy needs are enormous, and growing every day. Switch entirely to nuclear and we'd all be drowning in nuclear waste.

But my real concerns are best illustrated by what just happened in Japan: the very real risk of accidents or leaks that release highly dangerous ionizing radiation into the environment, contaminating land, water, and food sources for decades to come. Everyone still remembers the infamous Three Mile Island accident in 1979, and more recently, the Chernobyl disaster in 1986 in the Ukraine, the latter still considered the worst accident in the history of nuclear power.  According to the new "nuclear event rating scale" released by the International Atomic Energy Agency (IAEA),  Chernobyl is a 7 -- the highest rating on the scale. Three Mile Island rated a 5. We're still dealing with all the fallout -- real and metaphorical -- from the widespread Chernobyl contamination, even 20+ years later.

In fact, we're still dealing with the effects of the Trinity Test back in 1945. At the 52nd annual meeting of the Health Physics Society  (HPS) last week in Portland, Oregon, health physicist Tom Widner presented the first preliminary reports of total radiation dose to nearby residents . There really hasn't been a public accounting of that aspect of the Trinity Test, even though the local populace spent years breathing contaminated air and drinking contaminated water. It's an  ongoing study, due for completion in 2009, but those preliminary results were telling: at nearby ranches 19 miles from Ground Zero, the exposure rates were around 15  Roentgen per hour (as measured just over three hours after detonation). Most non-scientists aren't familiar with that scale, but it's a good 10,000 times greater than radiation limit that the Nuclear Regulatory Commission currently recommends (less than two millirem per hour). Widner's take as director of the study: "If officials had known what is now known about the long-term effects of radiation exposure, such as cancer, they would have much more likely ordered local evacuations, even though publicity was seen as a serious threat to the secrecy of the mission. (Jen-Luc Piquant thinks Widner is being a bit idealistic; she doesn't put it past our government to have simply decided those residents were expendable for the greater good of the nation.)

Granted, Three Mile Island and Chernobyl were statistical anomalies -- albeit very costly ones, in terms of human life and health. And yes, safety precautions are in place.  They were in place at Kashiwazaki Kariwa, although a review of those safety procedures is now pending. What scares me is the element of human error, and the accompanying dishonesty as managers struggle to hide the fact that they made a serious mistake. And equipment has to constantly be updated; not all plants are as conscientious in that regard. Here's more from the LA Times article, describing the damage to the plant from the earthquake, and the subsequent radiation leakage:

"... [A] fire broke out in an electrical transformer, spewing black soot into the sky for two hours before being brought control. Built in 1985 under now-outdated earthquake protection guidelines, the plant's seven reactors give it more production capacity than any other reactor in the world.... Company officials said four of the seven reactors were operating, or about to operate, when the earthquake hit, and that seismic activity detectors worked properly and shut down the plant as required. But the power station lacked the proper equipment to extinguish the chemical fire and had to await outside help. After initially denying any radioactive leaks occurred, company officials acknowledged several hours later that a small amount of coolant containing radioactive content had spilled from one reactor."

Now, supposedly, the amount of radioactive material that escaped was "minuscule," but those nameless plant officials seriously damaged their credibility by initially lying about the leak. We're talking about a serious potential human health risk, here -- there's no place for lying just to salvage the plant's reputation. (Jen-Luc Piquant can't believe Japan authorized construction of over 50 nuclear plants over "volatile tectonic plates" in the first place.)

Japan isn't the only culprit whose laxity could be placing the world at risk. The July 14 issue of New Scientist featured a short interview with Najmedin Meshkati, an expert in nuclear safety at the University of Southern California, who has serious concerns that Iran's large nuclear plants in Bushehr and elsewhere are equally vulnerable to accidents. Given Iran's strategic location, here's what Meshkati had to say about the spread of radioactive fallout from a major nuclear accident there: "If it happens in Bushehr... and the containment dome can't stop the fallout from traveling, the whole of Saudi Arabia, Kuwait, Dubai, and the rest of the Gulf will be downwind. If it happens at one of the uranium enrichment plants, the local population centers will be at the mercy of wind direction, as with the accident at Japan's enrichment plant in Tokaimura in 1999."

Even so, I might be persuaded to consider nuclear power to be  an acceptable tradeoff of risk vs benefit, were it not for the whole waste disposal issue -- and the fact that those radioactive "orphan sources" have a way of ending up in the wrong hands. That's right, there a global black market for radioactive wastes, and the radioactive isotopes used by various industries (including medicine). That was another highlight of the recent HPS meeting. Carolyn Jean MacKenzie of the IAEA's Division of Radiation, Transport, and Waste Safety flew in from her home base in Vienna, Austria, to discuss that agency's new process for conducting country-specific "search and secure strategies" for the recovery of orphan radioactive sources.

I admit, when I first read the abstract, it seemed a bit dry and boring. Procedural stuff is hardly pulse-pounding material. (Measures to be incorporated include "administrative paper searches, bankruptcy records, and keeping tabs on industries known to use radioactive materials." Yawn). But I dug a little deeper into the issue, and into MacKenzie's background, and found that the new process is based on lessons learned from more than 20 missions to search and secure orphan sources. Most recently, MacKenzie was in the former Soviet republic of Georgia, where as many as 300 radioactive sources have been recovered since the mid-1990s, thanks to the sharp economic decline in that region since the fall of the Soviet Union. In 2006, she was part of a team that located a powerful source of cesium-137 -- a radioactive isotope used by industry to check materials for flaws -- in a pile of dirt in an abandoned factory. They found a second source in a box of nuts and bolts in a private home. The family had been sleeping in the next room for years. (The BBC did an interesting segment on the mission; you can see the clip here.)

The situation is just as bad in Tajikstan, whose government is commendably intent on securing its 10 deserted sites, many of which are located near towns and villages -- all near Taboshar, which used to be the center of uranium mining and milling. Apparently there's a hill of more than a million tons of process residue just sitting there, unguarded, exposed to erosive elements like wind and rain. People salvage building materials from the site for their homes, and kids play around the big radioactive pile, blissfully unaware of the potential health hazards.

Is it any wonder the IAEA and others are seriously concerned about such material falling into terrorist hands? In 2005 alone, the IAEA tracked 103 confirmed incidents of illicit trafficking of nuclear and radioactive materials -- most of those involved orphan radioactive sources. We care, because such sources are the primary ingredient in dirty bombs (or radiological dispersion device, if you want to get all jargon-y about it).

According to other speakers at the HPS meeting, we are woefully under-prepared for such an attack; the Hurricane Katrina clusterf**k will look competent in comparison, if a 2003 federal training exercise is any indication. In that exercise, which simulated a dirty bomb attack, every single volunteer "victim" died before even reaching a hospital, mostly because fire and rescue personnel didn't really understand the nature of radiation -- or even how to use their radiation instruments -- when they got to the "scene." Better training programs for fire and rescue workers, as well as the National Guard and local health agencies, have since been developed, but the news hardly restores my confidence in our national preparedness. Seems to be an awful lot of windy rhetoric blowing around DC these days, with precious little to back it up when the chips are down.

The message one could easily get from all of the above is "Be afraid. Be very afraid. In fact, you might just want to stay inside for the remainder of your life on earth...preferably in an underground bunker sealed against any kind radiation." (Jen-Luc swears Dick Cheney pretty much lives in one; maybe he knows something we don't.) HPS folks responded to all this with a session on "Fighting Fear with Facts." Doug Van Cleef was among the speakers who addressed this issue. He's an employee of ORTEC, which manufactures radiation detection equipment, and wants us to know that "radioactivity is not synonymous with death." Without downplaying the reality of high-dose exposure (which pretty much is synonymous with death), he noted that dirty bombs have much lower levels and thus there would be less dangerous exposure -- any health effects would likely to be small.

The real risk of dirty bombs lies in the panic that would ensue, said Van Cleef, who seems to think that a dirty bomb would probably cause more deaths from car accidents as folks fled during evacuation than from the actual radiation. With images of Katrina still fresh in everyone's mind, maybe Van Cleef has a point. Maybe not -- I'm less likely than he is to downplay the danger of adverse health effects from radiation exposure in a dirty bomb attack. Nonetheless, I support the idea of fighting radiation fears with radiation facts: educating the public on this topic equips them to (a) not panic as easily, because they can strike that critical balance between over-exaggerating and excessively downplaying the risks involved, and can thereby (b) make better, informed decisions rather than relying on government officials (who as we have seen, are known to lie to protect their own interests) to tell them when sometime is safe or unsafe. A scientifically informed public is a healthy, happy public, as far as I'm concerned.

Besides, there's plenty of other things out there for the public to panic about -- things like the mysterious ingredients in the hugely popular Red Bull Energy Drinks. I'm not a fan myself, but Jen-Luc was a major consumer until she read an article this week in Wired, about what the drink actually contains. It's not the beverage taken as a whole that gives you wings, it's the ingredients: caffeine, to be sure, but also meat sugar (a.k.a., inositol) and, um, bull bile. Yummy! The secret ingredient in bull bile is taurine, a powerful age-defying antioxidant. No wonder Jen-Luc is eternally youthful. She's currently weighing the risks vs. benefits of continuing to drink bull bile and meat sugar on a regular basis -- anything in the name of perpetually youthful skin.

whatever floats your boat

Summertime, and the living is easy, at least for me and Future Spouse. We suddenly found our respective travel schedules sufficiently curtailed that we will both be in the same place for almost an entire month. Inconceivable! Leisure time is the ultimate novelty, and frankly, we're unaccustomed to that luxury. Lest we be reduced to sneering at each other's writer's block and heaving crockery about to relieve the boredom, we took the opportunity to explore our new hometown. Friday night, we saw an outdoor performance of Hamlet staged in the Hollywood Forever Cemetery, right smack in front of the tomb of Douglas Fairbanks (the event inspired a fluffy little piece at Huffington Post on "10 Things I Hate About Hamlet"). And Saturday night, we experienced "Dining in the Dark" (you can read more about our experience here).

Jen-Luc Piquant skipped out on those festivities in favor of consorting with her swashbuckling pirate mates over kegs of spiced rum (because everyone's got a little "Captain" in them, even faux-French avatars). There was much reminiscing over last month's Concrete Canoe Competition, an annual three-day event sponsored by the American Society of Civil Engineers (ASCE). Basically, teams of engineering students from universities all over the country compete to design and build the best canoe made out of concrete. The idea is to provide engineering students with a practical application of classroom principles, along with vital team and project management skills. It also "challenges their knowledge, creativity, and stamina, while showcasing the versatility and durability of concrete as a building material."

It's true, concrete is one of most common and versatile construction materials, used in pavement, buildings, foundations, roads, parking structures, and so forth. That explains why it's such a huge industry: about six billion cubic meters of concrete are made each year (at least per the most recent data from 2005), with a market value of around $35 billion. It also accounts for more than two million jobs. Its versatility is due in part to the fact that it can be mixed in so many different ways, to achieve different desired properties for specific uses. Almost all concrete is essentially cement mixed with water and some sort of aggregate (space filler); it hardens thanks to a chemical process called hydration, in which water reacts with the cement and bonds all the components together into the final stone-like material we know and love. That aggregate can contain just about anything. The concrete used in sidewalks, for instance, uses larger, heavier aggregates like rocks, gravel or sand. With the advent of carbon nanotubes, it's become more commonplace to mix them into the cement aggregates for added strength. But to build concrete canoes, far lighter materials are favored as aggregates: teams use things like glass bubbles, fly ash, or silica fume.

And yes, the canoes really do float, a compelling example of Archimedes' Principle in action: a body immersed in a fluid is pushed up by a force equal to the weight of the displaced fluid. You remember Archimedes. He was a Greek mathematician, famous for all kinds of things, but among the most oft-repeated tales is how he came to the aid of his friend, Hiero, king of the Greek city of Syracuse. Hiero suspected that a goldsmith charged with making him a royal crown -- one assumes he needed a spare -- had kept some of the gold provided for himself, and mixed in silver to ensure the weight of the final crown matched that of the original lump of gold provided. He didn't want to melt the crown down to discover the truth, but the thought just nagged at him, and he asked Archimedes to help. Inspiration hit one day as Archimedes lowered himself into one of the public baths in the city and noticed displaced water flowing over the sides of the tub. Legend has it that he was so excited with his insight, he leapt out of the tub and ran (naked?) through the streets of Syracuse yelling, "Eureka! Eureka!" ("I found it! I found it!")

A theoretical insight must be backed up by experiment, so Archimedes took a lump of gold and of silver, each weighing the same as the king's crown, although the lump of silver was much larger because silver is lighter than gold. He put each lump in a vessel filled to the rim with water, and noted that the larger amount of silver caused more water to overflow than the lump of gold, because there was more material, even though both weighed the same. He concluded that a solid material will push away an amount of water equal to its own bulkiness (volume). So if the king's crown were indeed made of pure gold, it would have to displace the same amount of water as the lump of pure gold that weighed the same. Unfortunately for the dishonest goldsmith, the crown made more water overflow than the pure lump of gold, proving that the goldsmith had added silver to the crown to make it bulkier. The goldsmith's fate was probably not a happy one.

This property is known as buoyancy: an object will float if its buoyancy is greater than its weight, and will sink if its weight is greater than its buoyancy. It must be said that the shape and position of a given object plays a vital role here: a concrete canoe placed on end in water will sink because the weight of the concrete is greater than that of the displaced water. But in its normal position, the weight of the canoe depends on its total volume, and this includes all the air inside it. So the average weight is less than that of the water displaced, and the canoe floats. It's weird, but true, like many counter-intuitive concepts in physics. And let's face it -- it's also pretty cool. (According to Wikipedia, the competition rules allow teams to insert concrete-covered, non-structural foam pieces in their canoes so that the canoes float after being submerged. Hmmm. Seems like a bit of cheat to me.)

Concrete in some form or another dates back to 5600 BC Serbia (Bora! would be so proud), evidenced by the discovery of remnants of a hut with a floor made of red lime, sand and gravel. In China, the pyramids of Shaanxi (thousands of years old) contain a mixture of lime and volcanic ash or clay, and the Assyrians and Babylonians also used clay as cement in their concrete. Builders in the Roman Empire preferred concrete made from quicklime, pozzolanic ash, and an aggregate mad from pumice (similar to modern Portland cement concrete). They also figured out that adding horse hair made concrete less likely to shrink, while adding blood -- you heard me: blood -- made the concrete more frost-resistant. The Egyptians liked to different and opted for lime and gypsum cement -- although in all seriousness, the variations probably had as much to do with available materials in the different regions as anything else.

For some reason, though, the various formulas for concrete were lost for roughly 13 centuries, before a British engineer named John Smeaton pioneered the use of Portland cement in concrete in 1756. (He used pebbles and powdered brick as aggregate.) It was only matter of time before someone got the idea to build a boat out of concrete, and it finally happened in 1848: a Frenchman named Joseph Louis Labot built a boat out of ferro-concrete that is still on display at the Brignoles Museum. Forty years later, the Dutch got into the act, with a concrete boat that proved so durable, it was still in use at the Amsterdam zoo as recently as 1967,

But racing concrete canoes? Who'd a thunk it? An engineering professor named Clyde Kessler, that's who. Back in 1969, he hit upon the notion of requiring his engineering students to build a canoe out of concrete. Word spread to another professor at nearby Purdue University, John McLaughlin, who challenged Kessler and his students to a competition. Since then, the event has expanded significantly, with more than 200 universities participating each year in regional competitions around the US (and that's not counting the other competitions occurring worldwide), and a magazine devoted entirely to concrete canoes. The winners of those move on to the national competition, considered to be the "Olympics of civil engineering," in much the same way that the annual International Physics Olympiad is the "Olympics of physics" -- except the national canoe competition isn't international. Still, the winning team does get to compete in the Dutch Concrete Canoe Challenge, to be held in the Netherlands this September.

Quite a bit of work goes into these designs; these are not fly-by-night creations. Top teams spend months on the project. They must design the canoes from scratch, usually creating the hull/overall shape with the aid of a computer design program. A styrofoam mold is made, and the particular concrete mix is designed.

Individual techniques vary, but in general, here's what happens. When it's time to actually build the canoe, the mold is covered with Crisco (so that it can be easily separated from the completed canoe) and a layer of cement is laid, followed by a fiberglass mesh to give more strength to the structure and also supply some tension to make the cement a bit more flexible, so it doesn't crack. (Stanford University's team built a canoe that cracked in half during a competition in the mid-1990s; strangely, the school hasn't competed since.) Then another layer of cement is applied, and another layer of fiberglass mesh, topped with one more cement layer. The entire canoe is then "cured" -- a process of hardening the concrete.

The team members also practice paddling, using a fiberglass model until the concrete canoe is ready, at which point they practice in the concrete craft to get a feel for it. This is key. In a 2006 article in Concrete Canoe Magazine, John Gilbert reminisced about that first race in Illinois in 1971: "Concrete canoes are not like their tamer counterparts made from aluminum or fiberglass. These canoes had minds of their own and needed to be coaxed wheedled, and urged around the course. And just when one felt one had control of the situation, one was liable to be tossed unceremoniously into the water by a none too subtle roll." The losing team (Purdue) learned the hard way: Know your boat if you want to win.

There are five different racing events in the competition: a men's pair, a women's pair, a men's slalom, a women's slalom, and a four-person co-ed sprint. The race might offer the most pulse-pounding excitement (especially for the poor sods who must paddle the sometimes unwieldy concrete canoes), but it only accounts for about 25% of the final score. There is also a technical paper, a technical presentation, and a "final product judging." Scanning over the technical papers, it's obvious that some real, hard science goes into these designs.

This year, the competition was held June 14-16 in Seattle, hosted by the University of Washington, and the University of Wisconsin, Madison, won for the fifth year in a row. The University of Florida placed second, with the University of Nevada, Reno, finishing a close third. It's not just a symbolic victory either: the winning teams receive scholarships of $5000, $2500 and $1500, respectively -- although, divided four ways, that doesn't amount to much, considering the months of work that goes into preparing for the competition. (I note with sadness that the City College of New York placed dead last out of 18 teams, perhaps because the only place to practice paddling is in the East River. And that's just, like, gross.)

If canoes just don't float your boat (oh, stop me before I pun again!), there's always the Great Northern Toboggan Race, a similar event intended to challenge the creativity of engineering students. It's been going on since 1974, and instead of designing and building concrete canoes, the students build toboggans with a metal frame and a running surface made completely out of concrete. Per Wikipedia, the resulting contraption must weigh less than 300 pounds, have a working braking system, and be fitted with a roll bar to protect its five passengers. It's a bit more elaborate than the canoe competition, in that teams also choose a theme for their sled -- drawn from pop culture or based on the home university and its location -- and compete dressed in costumes that match the theme. Sometimes even the toboggan design contains elements of the theme. That's Jen-Luc's kind of competition: she's got her pirate outfit all ready to go, the minute a toboggan team opts to be buccaneers.

the pit and the pendulum

Androgyny is a liability in Cyberspace, if a new study on people's choice of avatars is to be believed, and one should also take care in one's choice of condiments. Seriously. People rated androgynous avatars "less trustworthy" than those with an easily identifiable gender. It'd be easy to read something homophobic into that, but I'm inclined to think it has more to do with nervousness about who you might be dealing with on the Internet. A clearcut, open identity is just more reassuring. What I don't get is the whole ketchup thing: an avatar of a ketchup bottle rated next to last on the trustworthy scale. How can this be? It's so quintessentially American! Hot dogs and apple pie! And yet, it fell just below a cat, and just above a scaly lizard at the bottom of the heap. Hopefully the scientists will get to the bottom of that, and take a closer look at mustard and relish while they're at it. I've never quite trusted relish.

Fortunately there's no ambiguity whatsoever about Jen-Luc Piquant's virtual gender, so I guess readers find her trustworthy. ("Bwa-hah-hah-hah," she chortles with glee at having pulled the wool over the blogosphere's collective eyes.) But because she's also the mercurial, mischievous sort, she's donned a more ambiguous look for the day -- partly to mess with people's heads, but mostly because she's been dying to wear her "Tick Tribute" outfit again and get her fangrrl freak on ("Spooon!"). The jury's still out on the trustworthiness of avatars dressing up as their favorite superheroes. She even wore it to Monday night's promotional event at the Griffith Observatory, joining Future Spouse and myself for a preview screening of this fall's new science series on PBS: Wired Science.

Wired Science is a joint venture between PBS and Wired Magazine, and if the segment they showed is any indication, it's going to be terrific: smart, witty, and just a little bit snarky, at least if Wired's Adam Rogers is the field reporter. In the screened segment, he interviewed a couple of (very colorful) meteorite hunters, got to go on a hunt with them, and actually found a chunk of meteorite buried about two feet underground.  Even Rogers suspected the thing was planted, but the find appears to be genuine. The meteorite hunters turn their finds over to the curator of a meteorite "gallery," where the chunks are cleaned, displayed on little stands, and dubbed "art." One of the pieces was priced at $80,000, leading Rogers to describe the place on-air as "a really high end souvenir shop." Chatting with Rogers afterwards, we learned that the gallery's bathroom was decked out completely in meteorite material. Now we now what look we'll be going for should Future Spouse and I ever need to renovate a bathroom. Anyway, I strongly suspect that my butt will be parked in front of the tube on Wednesday nights at 8 PM for Wired Science; we'll just have to tape new episodes of Bones.

This was my first excursion to Griffith Observatory, newly refurbished and mercifully spared any damage from the recent wildfire that raged through Griffith Park a couple of months ago. It did not disappoint. (The catering was disappointing, though. Will someone explain to me why Wolfgang Puck still has any shred of reputation as a chef, when he really just  heads a glorified corporate chain?) We got to wander around the facility and check out the telescope. Visibility was poor, but you could still see Venus, although Future Spouse noted that the docent incorrectly identified it as Saturn. (Note to docent: Saturn's the one with the rings.)

But the observatory has more than just a telescope. There's some nicely done exhibits, on meteorites (how fitting!), the periodic table, and the usual astronomical topics. There's an entire room constructed to serve as a camera obscura. The term is Latin for "dark room," and that's pretty much what this was. In its simplest form, the camera obscura is just a small hole in a shade or a wall through which light from outside can pass into the dark room, projecting an inverted image of the scene onto the wall opposite the hole. The observatory's version is only slightly more elaborate, letting in light from above to project outdoor scenes onto a round white table in the center of the room.(Jen-Luc's superfluous bit o' trivia: NYC artist Vera Lutter is known for creating "photographs" using her own makeshift camera obscura: a wooden shack on the roof of the landmark Pepsi-Cola building in Queens. The images are projected onto photosensitive paper, burning into the sheets over the course of several hours.)

Several guests were understandably more enthralled by the fully operational Tesla coil, safely housed behind glass as it shot out sparks of electricity. It seems fitting to mention it, since yesterday was the anniversary of Nikola Tesla's birth, as Bora! reminds us. (Also check out Blake Stacey's LOLScience tribute to the Tesla/Westinghouse wars with Edison.) Tesla coils, for the uninitiated, are basically powerful transformers. Tesla's first patent for one, issued in 1891, had a power supply, a large capacitor (for storing electrical current), the coil itself (serving as an inductor), and adjustable spark gap electrodes. The coil and capacitor together comprise an oscillator, in which current and voltage kind of chase each other back forth, from one end of the circuit to another. Sending sparks (sudden electrical discharges) across the gap between the two electrodes sets the oscillator in motion. Voltage builds up in the capacitor until it becomes great enough that the air in the gap no longer acts as an insulator, and bolts of electrical current shoot out in pretty streaks. Then the whole cycle starts all over again. Tesla loved this sort of thing. His laboratory in Colorado Springs had a gigantic Tesla coil so powerful -- literally producing millions of volts, and shooting snakes of flame and lightning bolts 135 feet into the air -- that one of his experiments knocked the Colorado Springs Electric Company's generator offline and set it on fire. The entire town was in darkness from the blackout.

But the centerpiece at Griffith Observatory (apart from the telescope) is the very large Foucault Pendulum set up in the main hall area. It was part of the original design for the observatory, and when the place was refurbished, so was the pendulum. Such things are mainstays of science museums, with good reason: they're simple in concept, impressive in execution, and provide easily observable proof of the earth's rotation (other than the whole day and night phenomenon, but hey, that could be due to angels drawing the shades at bedtime). The pendulum swings slowly back and forth in a constant path, but as the Earth rotates, that path appears to change by roughly 0.2 degrees per minute. It's an illusion, though: the world around the pendulum is what's changing as the Earth rotates underneath the pendulum. (You can watch a Foucault pendulum in action on YouTube, peruse a large sampling of film clips and animations here, and even order your own small version here.)

Being the big science geek I am, I promptly came home and did some Googling on Foucault and his famous pendulum. (Half the fun of visiting science museums is being reminded of all the cool stuff one has forgotten in this age of information overload.) The set-up is the invention of a 19th century French physicist named Leon Foucault, the son of a publisher in Paris. He was home-schooled, for the most part, before formally studying medicine, although that specialty was short-lived: apparently the young Leon was squeamish at the sight of blood. This made him utterly unsuited for a career in medicine, so he switched to physical science. It proved to be an excellent choice: he went on to make numerous important contributions, in a wide variety of subfields. It's just that his mother couldn't brag about her son the doctor at her weekly knitting circle.

Foucault noticed in the lab one day in 1850 that a steel rod he'd placed on a nearby lathe would vibrate in response to an initial force. It gave him the idea to use a pendulum to experimentally demonstrate the rotation of the Earth. Scientists were already pretty sure the Earth rotated: they'd measured our planet's polar flattening and equatorial bulge, for instance. But they wouldn't be scientists if they didn't feel the need to test and retest the concept to death, from as many different angles as possible. Besides, the pendulum thing is just plain cool. Foucault demonstrated his pendulum for the first time in February 1851 at the Paris Observatory, and three weeks later suspended a 18-kg bob with a 67-meter wire from the dome of the Pantheon -- creating a public sensation.

Ideally, after 24 hours, the pendulum would return exactly to its original path. But we don't live in an ideal world; there's a whole bunch of other variables that come into play, and scientists do their best to account for them. For starters, Foucault himself found that the closer one travels to the equator, the more the oscillation follows an oval path, while at the North Pole, for example, the pendulum would appear to rotate an entire 360 degrees in one day.

Thanks to effects like air resistance and other sources of friction (the pendulum is attached to a ball in a socket, and all the grease in the world can't bring the mechanical friction to zero), the pendulum won't swing indefinitely -- that would make it a perpetual motion device. Instead it loses a bit of energy with every swing, gradually moving in increasingly shorter arcs until it stops altogether. (Most museums counter this by using some sort of electromagnetic drive to keep it moving.) Furthermore, the wire used to suspend the bob is extremely strong, but it still stretches over time because of the weight of the bob, and also in response to changes in temperature. I'm sure the Griffith Observatory is careful to maintain as constant a temperature as possible, but the device is so sensitive that even the slightest change can keep the pendulum from ending up at its original starting point 24 hours later.

Most of these variables are well-understood, even if it's tough to account for them all in an otherwise simple experiment. But in 1954, a physicist named Maurice Allais conducted a pendulum experiment over the course of 30 days, one of which happened to coincide with a total solar eclipse. It was an indoor experiment, so this should have had no impact on the pendulum, but instead of rotating at the usual rate as it did on the other 29 days, this time, the pendulum turned through an angle of 13.5 degrees in just 14 minutes. Allais saw the same effect five years later, when he repeated the same experiment during another total eclipse. As far as I can tell from my recent Adventures in Googleland, this effect remains a mystery, although everyone has a theory as to what causes it: gravitational waves, solar radiation, even the fact that space is different in different directions (what cosmologists like Future Spouse like to call anisotropy).

Anyway, Foucault is most famous for his pendulum, but he also invented the gyroscope for tracking the stars directly. It's similar in concept to the pendulum, in that its axis of rotation returns to the original orientation -- except in this case, the latitude is immaterial. He made an early measurement of the speed of light, discovered eddy currents, and he even has a crater on the Moon named after him. He also invented a method of testing the mirror of a reflecting telescope to determine its shape -- namely, to make sure the mirror is perfectly spherical. Before Foucault, figuring this out was pretty much a hit or miss proposition. The Griffith Observatory uses a refractive telescope, if memory serves, but still -- no wonder they have a fondness for Foucault. Leon died in 1868, two years after publishing one last paper on how to view the sun without ruining one's eyesight. (The trick is to deposit a transparent thin film of silver on the outer side of the object glass of the telescope.)

And that's the latest science museum excursion field report. I promise we'll get back to more substantial fare later in the week. Or not. I might just feel the need to blog about the fact that historians believe the rising trend of donning underwear under one's outer garments may have contributed to medieval literacy (hat tip: OmniBrain).

faster than a speeding prius

Tongues are all atwitter over the arrest of Al Gore III (or as Jen-Luc calls him, Al 3.0) for possession of contraband substances while speeding... in a Prius. In fact, people are a lot more intrigued by the impressive speed clocked by the plucky little hybrid -- 103 MPH! Go, daddy, go! -- than they are by the all-too-familiar site of a child of the rich and famous misbehaving in public. More celebrity spawn heading for rehab? Yawn. What else is new? But a hybrid whizzing along the highway at more than 100 MPH pretty much shatters our stereotypical assumptions about "green vehicles." I mean, the Prius is the car of choice for uber-liberal, tofu-and sprout-munching, Birkenstock-sporting aging hippies, right? And "greenies" poke along roads at or below the speed limit, irritating the hell out of other drivers, because they're waaay too relaxed from all that meditation in yoga class, right? Not that they'd have any choice, because those limp hybrid engines couldn't possibly match the tumescent gas-guzzling power of a top-notch V-8 engine. Or whatever.

Hah! The joke's on you! Thanks to Al 3.0, we Prius owners can bask in the proud knowledge that our little cars are not just efficient -- they're damned fast, too! Talk about a major paradigm shift in one's public image: the Prius is now a macho muscle car. Chalk it up to things like low-friction rubber tires and killer aerodynamic design -- because, as a Toyota spokesman told the LA Times: "Efficiency is just another word for performance." Damn straight. The only reason I haven't let my little red Prius go full throttle yet is because, well, traffic sucks in Los Angeles, and I'm thrilled when the roads are clear enough to actually be able to drive the speed limit, never mind pretend I'm on the Autobahn.

That said, I did make pretty good time driving to San Francisco yesterday, even if I never topped 75 MPH.  (The drive was mostly notable for the staggering 35-degree drop in temperature in a 20-minute time frame as I progressed into the Bay Area. Brrr!) This afternoon I ventured forth into the streets of San Francisco -- on foot -- and found my way to the