Cocktail Party Physics

gaga for science

It's been a busy spring. Among other highlights, the Spousal Unit and I made a whirlwind trip to New York City in March, so he could be on some obscure cable talk show or something. But we had the added treat of getting to see an excerpt from the modern opera, Hypermusic Prologue, featuring a libretto penned by none other than Harvard physicist Lisa Randall. She collaborated with Spanish composer Hèctor Parra, and artist Matthew Ritchie, on a reimagined segment of the full opera, tailored specifically to the museum's unique rotunda. Physics-inspired operas are rare enough; taking over part of the Guggenheim for the evening is even rarer. Afterward, the Spousal Unit was pondering his ideal collaborator should he undertake a similar project. He decided he'd like to do more of a "rock opera," collaborating with Lady Gaga.

So I'm just putting that thought out there into the ether, on the off-chance Lady Gaga is intrigued by the notion of a rock opera on entropy, the big bang, the arrow of time, and the multiverse, and decides to give the Spousal Unit a call. I'm sure MoMA would be interested if the Guggenheim passed on the opportunity. I mean, the outfits alone would qualify as works of art, and Gaga is as much performance artist as musician. Everything she does is calculated to make an impression -- right down to her aversion to wearing pants of any kind. "When I'm writing music, I'm thinking about the clothes I want to wear on stage. It's all about everything altogether — performance art, pop performance art, fashion," Gaga once told MTV News. "For me, it's everything coming together and being a real story that will bring back the super-fan. I want to bring that back."

Oh, yes, I am a Gaga fan, and I know Jen-Luc Piquant totally hangs around backstage at Gaga's YouTube channel in hopes of catching a brief glimpse of her idol -- or at least the pixelated version thereof. But it wasn't always the case. Gaga has had a meteoric rise, and I confess that I'd really only caught snippets of "Let's Dance" and "Poker Face" as they were racing up the dance charts, augmented by her increasingly frequent appearances in celebrity gossip columns. These days, Gaga is everywhere, and "Poker Face" is one of the most parodied tunes on YouTube, but it was the release of her video of "Bad Romance" that turned me into a fan (along with millions of others). Not only is it a killer song you can't help but dance to, but the performance is fierce, intense, sexy, visually innovative, and just a wee bit sneakily subversive. Check it out:

See? She's a free bitch, baby. And she's only 24, and getting better and better musically (unlike certain other pop icons who shall not be named, Gaga can actually sing and play the piano very well). (BTW, check out this awesome rendition of "Bad Romance" by male a capella group On the Rocks, complete with nods to "Thriller.") But there's another reason I love me some Gaga. Science could use an image makeover from a true master of performance like Lady Gaga, who literally invented her persona from scratch and then demanded the world pay attention to her. I think the Spousal Unit is onto something. Bring back the super-fans of science! And use the tools of mass media and marketing -- music, fashion, performance art, and story-telling -- to do it. Especially fashion, because science and technology are definitely influencing fashion these days, in ways that should fit neatly into Her Ladyship's artistic vision via the Haus of Gaga. She already made a splash this past February by debuting her version of a shape-shifting "living dress" inspired by the designs of fashion icon Hussein Chalayan, a self-described techno-geek who tries to bring together technology, science culture, and fashion in some really intriguing ways. 

Chalayan's work was all the rage in Paris during the fall of 2006, when he debuted his "One Hundred Eleven" collection, with nods to 111 years of fashion in just five dresses that used technology to morph from, say, an 1895 look to something more common in 1900, and finally into a Roaring 20s flapper sheath. The Hour-Glass Dress morphs from a style reminiscent of Dior in the 1950s to a 1960s metallic sheath, and the grand finale during the 2006 Paris show featured a dress that disappeared entirely into a wide-brimmed hat, leaving the model pretty much naked on the runway (see video below). Chalayan has remained at the top of the field ever since with increasingly outre designs; his style is perfect for Lady Gaga -- and for the Spousal Unit's rock opera concept -- because it's the haute couture version of wearable electronics, designed in collaboration with a company called 2D3D.

2D3D director Rob Edkins described some of the underlying technology for Technology Review back in 2006:

"Basically, the dresses were driven electronically by controlled, geared motors. We made, for want of a better term, little bum pads for the models. So on their buttocks were some hard containers, and within these containers we had all the battery packs, controlling chips--the microcontrollers and microswitches--and little geared motors. The motors we used were tiny, about a third of the size of a pencil and nine millimeters in diameter. Each of the motors had a little pulley, and the pulley was then attached to this monofilament wire which was fed through hollow tubes sewn into the corset of the dress.

"Some of the corsets were very complicated. They had 30 or 40 of these little tubes running everywhere, carrying these little cables, each doing its little job, lifting things up or releasing little linked metallic plates. There was a huge amount of stuff going on beneath the clothes."

My personal favorite of Chalayan's creations -- particularly when it comes to what we'd need for a cosmology-inspired rock opera -- is his "Big Bang" dress, which debuted during the 2008 Paris Fashion Week. Its another mechanical dress, except this one projects moving spots of light to symbolize the birth of the universe. A glimpse of the underlying machinery is below, and you can watch a video of the dress in action over at Adam Wright's website (he collaborated with Chalayan on the dress). [Click "Fashion" on the right side, then click on "Hussein Chalayan: Big Bang."] 

He's also done a series of LED dresses, in which light-emitting diodes are incorporated into the fabric. Pop singer Katy Perry recently wowed the crowds when she showed up at the Costume Institute Gala at the Metropolitan Museum of Art in a stunning LED gown. Really, that's almost as impressive as Meejin Yoon's "Defensible Dress," which has sensors woven into the fabric that can detect a person who is getting too close, thereby triggering "quills" to pop out and keep the intruder at a safe distance. (Yoon got the idea while working in Neil Gershenfeld's "Fab Lab" at MIT, and says she was inspired by the porcupine and the blowfish.)

Oh, but Chalayan didn't stop with morphing outfits and LED dresses; he also put together an architecturally inspired collection in 2009 featuring chairs and tables that transformed into wearable (at least in theory) garments. When was the last time you saw a tiered wooden skirt that doubled as a table? Chair covers that can turn into dresses? These are all elements that would be perfect for staging the Spousal Unit's hypothetical rock opera. Heck, if Chalayan prefers to focus on Galaxy/LED dresses for the performance, perhaps Neri Oxman can step in to help. Oxman is getting her PhD in design computation at MIT, and per io9, she specializes in "reactive architecture: surfaces, furnishings, and structures that change their own properties according to different stimuli. Her resin floors grow thicker where they need to support more weight; her composite walls rearrange their windows and stress lines based on local weather conditions. One of her best-known works, a chaise lounge called Beast, can adjust its shape, flexibility and softness to fit each person who sits in it."

Oxman incorporates so-called smart materials into her pieces. So does designer Marielle Leenders, who weaves wires containing shape memory alloys (like alloys of nickel and titanium) into her clothing to create, say, fabrics that contract under heat. So if you walk outside in a long-sleeved shirt, and it's warmer that perhaps you might expect, there's no need to roll up your own sleeves: the garment will respond to the increase in temperature and roll up itself. No kidding. No need for all those intricate cables, wires, motors and microcontrollers featured in Chalayan's designs! (Cracked.com has a problem with this concept. What's their problem? "You're an incredible lazy ass, that's the problem! What, you can't roll up your own sleeves?") It's still pretty ingenious on Leenders' part, and certainly preferable to Spray-On Fabric, or "Fabrican," which (according to the good folks at Cracked.com) "uses a pressurized formula that, when sprayed from an aerosol can, creates fibers that adhere to any surface and bind to create a piece of non-woven fabric. It can be sprayed onto a ... model, for example, to instantly create an entire dress or outfit right onto her body."

Then there's the tantalizing prospect of incorporating glitter-sized solar cells into fabrics to create clothing that produces electricity -- just the thing for charging your iPhone when you're on the go. That way you can be sure to get those all-important text messages sent by your sensor-lined underwear, alerting you to any unfortunate "accidents" you may experience. Per Discovery News:

"A firm in Australia called Simavita has invented a pair of electronic underpants for people who have incontinence that works to monitor and relay information about "accidents." Alerts are sent via text message over the institution's paging system. The underpants have a disposable element similar to a regular incontinence pad and include a detachable transmitter that relays readings from the pad's sensor strip over a wireless network to a central computer."

At least those mechanical dresses would have a built-in power source... so long as it was a sunny day. Ah, but what about more traditional means of ornamenting clothing? Beading and other kinds of adornment aren't just for clothing anymore; now you can place these things right onto the skin. Tattoos are old hat by now, although Gaga sports one quoting Rilke. It's even money that Gaga has already experimented with the new fashion trend of "vajazzling": "bedazzling" a certain sensitive area on women immortalized on Grey's Anatomy as the "va-jay-jay." Or maybe that's just a bit too tame for Her Ladyship. In which case, may I suggest the "dermatological embellishments" of Lauren Kalman, featured by Jessica Palmer at Bioephemera? Kalman is a metalsmith and mixed media artist who uses gold acupuncture wires to pierce the skin with mini-baubles in patterns that mimic certain skin diseases: a "rash of glistening blood-red stones set in gold," for instance to mimic an open sore. But since Gaga specializes in the gorgeously grotesque, she might like this, from an earlier series called "Hard Wear," in which golden crusts call to mind a heavily blistered mouth:

So that's a brief survey of cutting-edge, technology (and biology) inspired fashion to tempt Lady Gaga into considering a science-themed rock opera. For my part, I'm more on the grungy end of things; I'd probably want to work with the wild geeks of ArcAttack and their singing Tesla coils. They program the coils to perform electronic covers of tunes like the theme from Dr. Who (I'm still waiting for what I'm sure will be a killer version of the theme from Buffy the Vampire Slayer). Just watching the streaks of electricity emanating from the coils in time to the music is awe-inspiring enough, but these guys also devised a Faraday suit for their performances, enabling one of them (the one wearing the suit) to actually play with the arcs of electricity and not get electrocuted.

That suit that looks so much like a beekeeper's getup in the video below is actually what's known as a Faraday cage, an enclosure specifically designed to exclude electromagnetic fields. The 19th century British scientist Michael Faraday built the first one in 1836 to demonstrate his assertion that the charge on a charged conductor travels along the exterior surface and doesn't influence anything enclosed within it. It's essentially an application of "Gauss's Law": since like charges repel each other (opposites attract), electrical charge will "migrate" to the surface of a conducting form, such as a sphere. 

Faraday's 19th century version was an entire room coated with metal foil; he built it himself. Then he blasted the walls with high-voltage discharges from an electrostatic generator, and used an instrument called an electroscope to prove that no charge was present inside the actual room. As long as there are no gaps in the conductive "path," the electrical current from the lightning will never have much of an impact. The same thing is true of cars. If you happen to be sitting in a car when lightning strikes it, you'll probably be okay, as long as you don't stick your hand out the window to check and see if it's "still raining." The current will simply travel along the metallic exterior of the vehicle.

Be honest, now: wouldn't it be awesome to have a glitzed-up version of those singing Tesla coils on-stage with dancers and backup singers in spiffy tech-outfits, performing catchy dance tunes about time's arrow, entropy, and the birth of the universe? And for the finale, why not bring in the crack Caltech team -- working with Mindshare LA, an "idea factory that brings together scientists, artists, entrepreneurs, and others to engage in creative brainstorming" -- that helped OK Go design their warehouse-scale, two-story Rube Goldberg device for the video version of "This Too Shall Pass"? It starts with a toy car pushing against a column of dominoes, and ends with the band being splattered by paint guns. All those cheering folks at the video's end helped design and build the contraption, using "ideas and materials anyone can come up with at home."

[The band] wanted the machine strung together from the kind of everyday stuff you might find at a yard sale and to run on mostly mechanical energy. No computers, fancy electronics, or high-tech gimmickry. The machine had to interact with the four musicians and even perform part of their song—an honor that ultimately went to a pulley-controlled whirling guitar whose neck plinks out part of the tune on water glasses. It had to function flawlessly during a lengthy camera take, like an Olympic figure skater performing a perfect program. It went without saying that the finished product had to be an eye-catching crowd-pleaser.

The whole thing was shot in an abandoned warehouse in our neighborhood, Echo Park. Even with so many creative brilliant minds at work, the team needed over 70 takes, done over two solid days and nights of filming. The elaborate device worked perfectly on only three of those takes, one of which became the final video. To date, it's had over 12.4 million views (a dozen of which are mine -- I can't stop watching it in wonderment).

And there you have: a movable feast of science-inspired elements to provide fodder for the Spousal Unit's Gaga-esque rock opera about cosmology. For those who remain unconvinced, earlier this year, Improbable Research featured a couple of interesting equations: one a GA GA equation in a CHinese paper on PCR algorithms for parallel computing, and the other a (made-up) formula re-interpreting the lyrics, such as they are, in "Bad Romance." It goes like this: (RAH(<2> (AH)<3> + [ROMA (1+MA)] + (GA)<2> + (OOH)(LA)<2>. I'm telling you, it's a sign....

get the lead in

I recall reading an article asserting that women living in the same house or dorm would end up with synchronized menstrual cycles.  I'm thinking that women who blog together must have some universal rhythm too, since I started working on a "lead post" a week ago - well before Lee posted hers yesterday.  Luckily, lead is a dense enough topic that the only overlap between our posts is the Romans.

My inspiration wasn't a half-nekkid HughJackman (see Lee's post), although that is an inspirational vision.  I was trying to find out whether L'Oreal sponsored programming on PBS, as I'm looking for a funding source for a program I'd like to do on cosmetics.  What came up on Ask.com was a paper from Nanoletters by a group of researchers from L'Oreal R&D (in France) about nanoparticles of lead sulfide (PbS) used by the ancient Greeks and Romans for dying hair black.

Lead has been a cosmetics component for a very long time.  Lead white (lead carbonate or 2PbCO₃·Pb(OH)₂ + PbCO₃) was used for foundation by the Hellenes, which is pretty impressive because it takes a lot of chemical synthesis.  Pliny the Elder described how to prepare it from metallic lead and vinegar in a paper in a very early edition of JACS.  The Volos museum in Greece has power compacts from the end of the 4th Century B.C.  Lead white also used to be common in paints, but (as Lee points out), it poses a risk of lead poisoning.  The Romans just used talc and gypsum - as did I the one time my husband and I tried drywalling. 

The natural look is in now, thankfully, but it surprised me that the many of the Greco-Roman recipes are still being used.  Mix lead oxide (PbO) with slaked lime (Ca (OH)₂) and a small amount of water.  The resulting paste applied to gray or light-colored hair and, after 24-72 hours, turns the hair black.  Grecian formula is lead (II) acetate (Pb(CH₃COO)₂) and it works the same way as the ancient formula.  (Just for Men hair coloring does not use lead acetate - but it doesn't work as gradually as Grecian formula.  Or so I'm told.)

The protein alpha-keratin makes up most of your hair (as well as your fingernails).  (Beta keratin makes up harder things, like bird beaks, reptile claws and scales). Keratin is a long coiled molecule that acts like a spring, as shown in yellow in the picture at left.  Four keratin springs twist together to form a protofibril.  Eleven protofibrils twist together to form a microfibril, which is the largest structure shown in the diagram at left.  Keratins have lots of the sulfur-containing amino acid cysteine and that allows the formation of disulfide bridges that hold together keratin molecules.  Think of a disulfide bridge as two keratin molecules holding hands.  The bridge forms a much stronger structure than the two individual molecules.  Sulfur bridges do the same thing in vulcanized rubber.

Microfibrils pack together in long thin bundles called macrofibrils.  Macrofibrils pack together to form long thin cortical cells, and cortical cells pack together to form a hair. Human hair is about 14% cysteine and most of it is in the grey area in the figure that separates macrofibrils.  There is a fair amount of sulfur in hair, which is why burning hair is one of the absolute worst smells in the world - even when it is someone else's hair.  Permanent curling and straightening products break sulfur bridges, reshape the hair, and then reform the bridges so that the hair adapts the new shape.To give you an idea of size, the average hair is about 70,000 nanometers.  A macrofibril is roughly 7 nanometers in diameter. L'Oreal has a great animation showing the composition of the hair. The picture at right (from the L'Oreal animation) shows the macrofibrils (the smallest structures visible in that shot) and the cortical cells that make up a hair.

The little black things you see within each macrofibril is melanin, which is responsible for giving you your hair color.  Large star-shaped cells called melanocytes reside at the bottom of the hair follicle and manufacture the melanin, which is incorporated into the hair structure as the hair is formed. Only about 1% of the hair is melanin, so it doesn't take much to give it its color.

There are only two types of melanin.  Eumelanin is rice-shaped and comes in brown and black varieties. Phaeomelanin is irregularly shaped and imparts a pink to red hue. Japanese hair contains mostly eumelanin and red hair is rich is phaeomelanin.  Black eumelanin is in mostly non-Europeans, while brown eumelanin is in mostly young Europeans.  A small amount of brown eumelanin in the absence of other pigments makes hair blond.  A small amount of black eumelanin without other pigments causes grey hair. With no melanin, hair is white, although we don't know yet whether that is because your body stops producing melanin, or if it just isn't incorporated into the hair.

When the coloring formula interacts with the hair, the lead in the colorant combines with the sulfur in the hair and forms nanoparticles of lead sulfide (PbS) with diameters between 4 nanometers and 15 nanometers.  In contrast, natural melanin that produces black hair is about 300 nanometers in diameter.  The longer you leave the formula on the hair, the more nanocrystals you form and the blacker the hair looks.  This is why coloring products like Grecian formula slowly change the hair color and can get rid of grey gradually, unlike permanent color.  The PbS nanocrystals are very small and it doesn't take a lot of them to change the apparent color of the hair, so the mechanical properties of the hair aren't really affected.

Why do they form nanocrystals and not microcrystals?  One theory is that peptides - polymers that surround the organized keratin proteins - form nanoreactors that limit the size of the PbS nanoparticles.  The nanoparticles accumulate preferentially at the boundaries between the microfibrils, whereas melanin colorants are randomly distributed throughout the hair.

L'Oreal presents the L'Oreal-UNESCO awards each year to outstanding women scientists across the world:  one in African/Arab countries, one in Europe, one in North America, one in Asia, and one in Latin America.  The awards recognize the important role science plays in their industry and in the rest of the world.  They also offer a variety of awards and fellowships for women at other stages in their careers.. because we're worth it.

these boots weren't made for walking

Every now and then, shoe-frenzy makes a cameo appearance the blogosphere. Okay, it's omnipresent in blogs dealing with fashion and shopping, but most of us (male and female) have to shop for footwear at some point. And some of us feel compelled to blog about our particularly noteworthy finds, at least in passing. You know, like the incomparable Heather Armstrong at Dooce, who has waxed ecstatic about silver-metallic ballet flats (dismissed by her husband as "elf shoes"), and once wrote this wonderful paean to the joy of finding the perfect pair. Armstrong is known for detailing the minutiae of her daily life on her blog, but that doesn't mean the rest of us don't occasionally bliss out over an especially nifty pair of pumps. Which is exactly what happened in comment threads this week over at Bitch PhD and Shakesville. (Fair warning to the easily offended: why are you clicking on a link to a blog called Bitch PhD in the first place? Because you thought it would be about knitting while sipping mint juleps and nibbling cucumber sandwiches? Duh!)

Ah, but there are lots of killjoys out there on teh Internets, no doubt wearing too-tight or ill-fitting shoes (or, worse, clunky "sensible" shoes), which might explain why they're so cranky, and why they feel compelled to spoil other people's fun. Apparently some people criticized Shakesville's Melissa McEwan for departing from her usual hard-hitting feminist political fare to focus on something as trivial as shoes. I'm guessing this is something women scientists face as well. We aren't allowed, it seems, to take pleasure in the small joys of life and still be Serious Women, respected professionals in our chosen fields.

Um, screw that. I'm the patron saint of comfy sensible shoes -- I'm known for it among my female friends, in fact (who are not always complimentary about my workmanlike choices) -- but that doesn't mean I can't branch out once in awhile and be truly stylin'. Who says women can't be smart, serious, 100% professional, and still totally rock a pair of hot pink pumps if they want to? (Or asphalt-stomping Doc Martens, if that's your preference. To each his/her own.) In honor of Melissa, Bitch PhD, Heather, and all you other shoe-lovers out there, today's post will focus on the science of footwear.

First, a look at this week's featured products before we delve into the science. Bitch PhD offered these multi-colored beauties:

Then Melissa weighed in with these innocent-seeming pink pumps that launched a thousand angry comments (UPDATE: Oops! Apparently it was only a couple of negative comments, but it did inspire her to write a blog post on the topic):

Followed by these plaid ballet flats, for the more sensible-minded of her readers:

Just for good measure, since we're talking flats, here's Heather's silver ballet flats (a.k.a., "elf shoes"), which I covet greatly:

Perhaps your tastes run to more of a Goth/fetish look. A few blog posts ago, I mentioned going shoe-shopping with the Spousal Unit (who wore ostrich skin boots at our wedding, so he's a man who appreciates stylish footwear). I got some comfy low-heeled sandals for summer, a couple pairs of Skechers (for daily practical wear), and these fabulous New Rock Malicia Silver Spiderweb mid-calf-length boots:

Yeah. It's an indulgence. These boots are definitely not made for walking, although as stiletto heels go, they're surprisingly comfortable. Ergo, I bought them. That's what a well-made pair of heels does for you, and why they're worth paying a bit extra. According to a UK pal of mine, "fantasy heels" are all the rage this season for the "fashion forward." Take that, cranky Shakesville commenters! (Or, you know, the one or two commenters who complained...)

Okay, so we're fashion forward. Yay, us. But could there really be any actual science associated with sexy stilettos? "Mais oui!" Jen-Luc Piquant exclaims. "How could you doubt it?" We need look no further than Jolly Olde England. Several years ago, The Globe and Mail ran an entertaining article about a physics professor at the University of Surrey named Paul Stevenson who calculated the maximum height of stiletto heels a woman could wear without falling over, and/or cramping up in pain. He did so at the behest of a publicist at the Institute of Physics in London, who -- while watching the series finale of Sex and the City -- found herself wondering how the women in the show could possibly wear such high stiletto heels and still perambulate around the Big Apple with any measure of grace. I've never seen the appeal of the show myself (which puts me firmly in the minority among women), but must admit, it's a valid question.

Stevenson obliged by coming up with a formula for the maximum heel height you could wear without tipping over: h = Q x (12+3s/8). His formula determines how changes in foot slope increase the "tippiness" likelihood. It's based on the wearer's shoe size and something he calls the "Q" factor: taking into account sociological factors like how much pain a woman is prepared to tolerate for the sake of style. (If you're me, the Q factor is pretty low: if a shoe pinches or chafes, it's coming off, which is why those gorgeous Michael Kors sage green ballet flats I bought for half price are sitting forlornly in my closet, unworn. But a friend of mine once developed bleeding blisters walking around in ill-fitting shoes because she loved them so much.) It's hard to quantify that sort of subjective parameter, which is probably why we haven't seen Stevenson's paper on arXiv. But he made a noble attempt, figuring in things like "the probability that wearing the shoes will turn heads," how much experience (in years) the wearer has with high heels, the cost of the shoes (in British pounds), how much time has elapsed since the shoe style was all the rage, and of course, the amount of alcohol consumed by the wearer.

Going by Stevenson's handy formula, the answer is: about five inches. (Of course, that's assuming the wearer is sober; alcohol can really disrupt one's equilibrium.) It's basic Pythagorean geometry, really: much like the hypotenuse of a triangle, the sharper the angle of the foot in the shoe, the more unsteady the wearer becomes -- especially since stilettos support the wearer's weight on a relatively small area. The answer would be different for a broader heel, since the greater area would probably help the wearer remain stable at even greater heel heights.

Stability aside, one's weight pressing down on stiletto heels produces a huge amount of pressure. The late, great songstress Kirsty MacColl has a classic tune called "In These Shoes," wherein the heroine turns down offers from aspiring swains to take her on all kinds of far-flung adventures, in response to which she sniffs, "In these shoes? I don't think so...." In the final stanza, an Englishman asks her to walk up and down his spine in her sexy stilettos. The response: "In these shoes? I doubt you'd survive." She's not kidding. A 100-pound woman in a pair of stiletto high heels would exert pressure under the foot that is 20 times greater than that of a 6-ton elephant. (Jen-Luc cautions: Don't make Sarah Jessica Parker angry by knocking Sex and the City too loudly, lest she stomp on you with her pricey Manolo Blahnik pumps!) 

Stevenson's formula was primarily concerned with balance, but the awkward angles and high pressures associated with heels has been cause for concern in some circles. For years now, orthopaedists, podiatrists and other medical sorts have been warning women about the health risks of routinely donning high heels: bunions, stress fractures, joint pain in the ball of the foot (because weight is shifted to the ball of your foot, rather than being distributed over the entire foot), corns and calluses, hammertoes, ingrown toenails, toenail fungus, and something called "pump bumps" (enlargement of the bony area on the back of the heel). High heels have been linked to injured leg muscles, lower back pain, and osteoarthritis in the knee, too, because when you wear heels, the foot slides forward, redistributes your weight and creates those unnatural pressure points. You can pretty much kiss healthy spinal alignment goodbye. 

High heels also mean your heel bones don't regularly come into contact with the ground, so the Achilles tendon can't stretch out properly while walking, and thus becomes shortened and/or tightened. Then there's a little thing called Morton's neuroma, a growth of nerve tissue in the foot -- usually between the third and fourth toes -- that arises when you wear too-tight shoes, causing sharp burning pain in the ball of your foot and a stinging or numbness in your toes. The list goes on and on. In fact, thanks to high heels, the American Orthopaedic Foot & Ankle Society estimates that women account for 90% of surgeries performed each year for common foot ailments.  That's about $3.5 billion annually in the US alone, according to this May 2007 article in the Washington Post.

Suddenly Heather's "elf shoes" are starting to look pretty good, right? Ah, but are flats really better for your feet than heels? Inquiring minds want to know. The answer is, not necessarily. Flip-flops, for example, can cause other kinds of problems, like plantar fasciitis, thanks to the repeated lifting of the heel away from the shoe surface. Ballet flats don't offer much in the way of arch support, and can still be tight and/or ill-fitting; they're not really made for walking long distances, either. So perhaps now all the folks who snickered at the practical Teva clogs I wore until they fell apart will reconsider their harsh judgment of my fashion sense. I could walk for hours in those Tevas, they were that comfortable. And having lived without a car for many years in New York City and Washington DC, I've always been an inveterate walker.

So, what should we look for in a stylin' pair of shoes? The recommendation is usually for a rounded toe, more cushioning in the sole, and good arch support (a quality that is lacking in my pretty new Skechers and languishing Kors ballet flats). If one must wear high heels, it's recommended you limit the height to 3 inches (preferably 1 or 2 inches) and not wear them for more than three hours at a stretch -- something that is not an option for, say, cocktail waitresses in Vegas. Wider heels are preferable to stilettos, and it's important to make sure shoes aren't too narrow for your feet.

The Mayo Clinic recommends shopping for shoes in the late afternoon or early evening, since the feet swell up during the day, and trying on both shoes of a pair, since many folks have one foot that is bigger than the other. Also? "There's no such thing as a 'break-in' period. Shoes should feel comfortable right away. Don't buy a pair that you think will fit well after you've worn them for awhile." (*hangs head in shame*) We have all been guilty of this... especially when I was impoverished in the Big Apple and Payless Shoe Source was the only outlet I could afford.

When I shop for "fashionable" shoes these days, I tend to avoid pointed toes as a general rule (because I have freakishly long, mutant toes), but here's something I discovered about pricier shoes: the pointed toes are actually "fake." What I mean is, they're made longer than usual, so one's toes aren't really being crunched together into that tiny space. That's certainly the case with my new Malicia spiderweb boots, and with the stunning black Dior pumps I purchased for our wedding. The downside: most of us can't afford the high price tags for high-end heels. Those prices have recently gotten way out of hand, with some of the most famous designers charging over $1000. The Los Angeles Times recently reported that many consumers have "balked" at paying those prices. Um, ya think?

The good news for women who love their stiletto heels is twofold. First, several shoe manufacturers are coming out with "healthy high heels" with more air-cushioning. For example, the Massachusetts-based Insolia has designed a line of heels with weight-shifting inserts that shift body weight off the ball of the foot, with a shape that places feet in optimal position for a high heel, thereby improving body alignment and ankle stability -- while still making sure the shoes are attractive.

But there's even better news, according to this February 12 report: "High Heels Might Boost Your Sex Life."  The same unnatural posture that wrecks your spinal alignment can also tone your abdomen and pelvic floor, according to Maria Angela Cerruto, a urologist at the University of Verona in Italy. She tested 66 women under the age of 50 and found that if they stood with feet at a 15-degree angle -- achievable by wearing three-inch heels -- the pelvic muscles were more relaxed, making them stronger and easier to contract. To counter being pushed forward by the heels, women naturally tighten the abdominal muscles and push the pelvis under. Cerruto thinks this might mean that wearing heals could reduce the need for so-called "Kegel" pelvic exercises -- associated not just with reversing the toll of pregnancy, childbirth, extra weight and such on women, but also with improving sexual response/gratification. Manolo Blahnik, for one, is thrilled at the findings, no doubt with visions of dollar signs dancing in his head.

So there you have it: the science of shoes. The upshot is, be smart about your choices, but wear the styles you like, whether it be sexy stilettos, ballet flats, platform wedges, comfy Tevas, cowboy boots, or anything in between.  After all, ever since humans began wearing shoes, the accessory has been as much about status and fashion, as about practicality and comfort. The WaPo article quotes Elizabeth Semmelhack, curator at Toronto's Bata Shoe Museum, which has some 13,000 artifacts, including one that is nearly 4500 years old. "It's absolutely clear to me... when I look at cultures that impracticality is one of the primary features among the privileged" class, she said. And the rest of us seek to emulate the privileged class. Or perhaps, as Dawn once said in an episode of Buffy the Vampire Slayer, it's just because "Everyone loves a slender ankle."