Facto Diem

Linkage

2011-02-13T11:46:00.006-05:00

Recently I've been working as a staff writer at Life's Little Mysteries, a website that explains the science behind the news and life in general. It's kind of a cool site, which has allowed me to research and write about everything from how stealth planes work to how the Egyptian government actually managed to turn off the Internet two weeks ago. After the mob bust that happened recently, I wrote about whether or to what extent the mob still runs New York, and I wrote a piece about men, women, and kissing for Valentine's Day.

Whenever a cool video goes viral on Youtube, like this video of a gorilla in a British zoo walking upright like a human, we find experts to explain the science behind them. Check out the site, and if you have an interesting question for us to answer, please send me an email!

I've also done some freelance writing at Popular Science Magazine and PopSci.com in the past few months. I wrote a long feature on the Pioneer Anomaly (which, as you may recall, I wrote about here first), and another short piece on the evolutionary purpose of tickling. I'm working on a new piece for them on gravity research that should be out soon.

Not much time for Facto Diem these days, but at the very least I will be better about updating the site with links to my articles published elsewhere.

Walking Around

2010-12-05T20:50:00.004-05:00

When lost in the desert or a thick forest -- terrains devoid of landmarks -- people tend to walk in circles. Blindfolded people show the same tendency; lacking external reference points, they curve around in loops as tight as 20 meters in diameter, all the while believing themselves to be walking in straight lines.

Why can't we walk straight? A group led by Jan Soulman of the Max Planck Institute for Biological Cybergenetics in Germany recently made gains toward answering this age-old question. By conducting a series of experiments with blindfolded test subjects, the team systematically ruled out body asymmetries as an explanation: Things like uneven legs and right- or left-side dominance did not correlate with walkers' veering directions. They also ruled out random noise in sensory input and/or motor output as the culprit, since this would have caused walkers to meander back and forth in a zig-zag fashion rather than to trace out circles.

Loopy paths, they concluded, are caused by a walker's changing sense of "straight ahead" itself. With every step, a small deviation is added to her cognitive sense of what's straight, and these deviations accumulate to send her veering around in tighter and tighter circles as time goes on. This increasing curvature doesn't happen under normal circumstances, which is to say, when external reference points are visible, because those allow the walker to frequently recalibrate her sense of direction.

Soulman's team is not quite sure where in our inner workings the accumulating deviations arise. Their best bet is placed on the vestibular system -- the system in our inner ears that maintains balance -- which is already well-known to exhibit biases. Some people have vestibular disorders so severe that they find walking in straight lines impossible even under normal circumstances. For most of us, the subtle leftward or rightward bias of our sense of direction would only rear its head if we were trying to find our way through a dense forest, or, perhaps, blindfolded by pirates and made to walk the plank.

The Truth, The Whole Truth

2010-12-01T23:28:00.011-05:00

Language is notoriously insufficient when it comes to grasping truth. Words, riddled with connotations and subjectivity and vestiges and misunderstandings, never seem just right. Using them, you can only ever approach the telling of the truth, but can never quite tell it.

Most of us have the impression that the breach lies with all those sources of ambiguity - that if you stripped away confusion and abstraction from language and left behind only perfect precision and clarity, which is to say, the language of logic--math--then you could achieve truth. And in theory (you might think) if you were an omniscient being, you could solve any mystery of the universe with mathematics, whether it be the workings of consciousness, the reason for entropy's rise, or the distribution of the prime numbers. Of course, your equations or proofs would be unimaginably complex. It doesn't matter. Truth seems achievable, in theory, by pure math.

But it isn't. Two of the strangest, most striking, most devastating, and thus most ignored math theorems ever proven, Kurt Godel's First & Second Incompleteness Theorems (1931), imply that math, like all other languages, can only approach truth, but can never grasp it.

Because the second incompleteness theorem follows quite easily from the first without adding much to it, I'll dispense with it and simply try to explain the first theorem. It states that formal systems--read: systems of mathematics generated from first principles (like the concepts of zero, and one, and two, etc.) and the rules that they logically follow (like addition and multiplication)--can never be both consistent and complete.

First, what does it mean for a system to be consistent? It means that no statement and its negation are both provable using the rules of the system. For example, if A is proven true within the system, then for consistency, "not A" must be proven false.

Consistency is the pleasure of mathematics. In the real world--the world of grey areas--A and "not A" usually both have some degree of truth to them, because real-world A's and "not A's" are far more complicated than the A's and "not A's" of math, and thus they are burdened with the ambiguity and confusion I complained of before. Still, in theory, even real world statements could be set up as extremely complex mathematical statements and, in that form, proven either true or false.

What does it mean for the formal system to be complete? It means that everything that is true can be proven true using the principles and rules of the system.

Putting those clarifications together, we can grasp Godel's incompleteness theorem. It says that if a system is consistent (never contradictory), then it lacks the tools to prove all the true statements that exist. Some mathematicians and logicians worry that some of the truths we have already conceived of (for example, the infinite distribution of twin primes) are not provable within math.

On the other hand, if a formal system is complete--if there is nothing true that isn't provable by the rules of the system--then the system is inconsistent. In other words, there must be some statement A in the system for which both A and "not A" are provable.

This is sort of mindboggling and a little hard to swallow, but in fact the theorem is true beyond the shadow of a doubt. Since plenty of links are available, I won't regurgitate the theorem's proof in a non-rigorous form, but the gist of it is this: within any formal system, it is possible to generate a formula that relates to its own provability. In words, the proven formula states: "This formula can't be proven." Contemplating this, you'll realize that since the formula is proven by the system, it must be true. But if it is true, then it can't be proven by the system. This contradiction renders completeness and consistency incompatible. (See for yourself.)

Obviously the heart of the proof relates to famously paradoxical sentences in everyday language, like the liar's paradox: "This sentence is a lie." Apparently the problem with that sentence runs much deeper than the mere ambiguity of words. The problem is fundamental, and Godel made it mathematically rigorous.

And its implications are profound. Because Godel's theorem bars humans from omniscience, many theologians use it to establish a sort of mathematical realm for God. He, not we, can know everything (they say). But in truth (no pun intended), Godel's theorem blocks even God's access to omniscience.

Stephen Hawking and Freeman Dyson interpret the incompleteness theorem to mean that we will never attain a theory of everything - the holy grail of physics. Most mathematicians disagree. They argue that the math used by physics is a proven subset of all math.

The theorem's undeniable implications are enormous enough. In a recent paper, Geoffrey Laforte and his colleagues lament them nicely. They write, "There is no bedrock of mathematical certainty on which the edifice of science must be based, no direct route to mathematical Truth ... We can never be absolutely sure that we have things right, even in mathematics, and still less can we be certain that all truths will eventually be vouchsafed to us."

The incompleteness theorem lurks like an unpatchable hole in the foundation of mathematics, and of human knowledge itself. With no alternative, most mathematicians, logicians, philosophers and scientists choose to step around it, and walk on.

Self-Projection

2010-11-10T23:19:00.020-05:00

Video feedback occurs when you point a camera at a display of its own output. Because of built-in processing delays, at every instant, the camera records an image that it projected about 40 milliseconds earlier. Because it records the previously projected image from some distance away, and probably at a slight angle, the recorded image is always a slightly distorted version of the projected one. The distortion gets projected on the display in turn, and then that gets recorded (with further distortions) and projected, and so on: The video output beautifully evolves.

Geometry drives evolution in video feedback. If a camera is zoomed in on its display, it continuously magnifies the projected image by stretching out the tiny details, including noise, in its center. If, on the other hand, the camera is zoomed out, then features get compressed to the center with every iteration of the feedback loop. If the camera is rotated or angled while recording its own output, then the stretching and compressing caused by the zoom happens along spiral paths. (This formula describes image distortion as a function of these various settings.)

Of course, because of the iterative, fractal nature of the video feedback effect, it isn't surprising that it causes familiar and organic patterns to emerge, as seen in the above clip.

Natural Born Killer

2010-10-16T16:46:00.006-04:00

It is the pain-causing agent in insect venom and poisonous plant spines, and the diarrhea-inducing ingredient in the cellular juices of pathogenic amoebas: serotonin is an extremely potent chemical. No wonder, then, that just a few molecules more or less of it can send the brain hurtling between happiness and deep emotional unrest.

Serotonin in the brain influences everything from mood to fatigue to hunger to memory, and its levels are so precariously balanced that regulating it requires vast spirals of DNA. While outside factors like diet, sleep, and stress cause serotonin levels to fluctuate, damage at the source has far worse consequences: a single serotonin-related genetic defect can double or triple the likelihood of depression, obesity, or suicide.

Dysfunction in a gene called MAOA, the so-called "warrior gene," even goes so far as to cause psychopathy. The gene inhibits serotonin reception in the impulse-control region of the brain. Combined with exposure to abuse or trauma, studies show that the defect makes people highly susceptible to violent crime. Because the MAOA gene gets passed down only on the X sex chromosome of mothers, more men than women are psychopaths. For a man, only one X chromosome is inherited - the one from his mother, so, lacking an alternative, it gets expressed. A woman on the other hand gets an X from each parent, so that the normal MAOA gene usually inherited from her father can overrule a warrior one from her mother.

A neuroscientist named Jim Fallon of UC Irvine was one of the central figures involved in finding the correlation between the warrior gene and psychopathy. Psychopaths have fascinated Fallon for the past two decades, and perhaps, without knowing it, this was why: Fallon recently learned that no less than seven killers, including the famous Lizzie Borden, decorate his family tree. He subsequently analyzed the DNA and scanned the brains of every living member of his family. All their brain scans were normal (the orbital cortex of psychopaths shows little to no activity), and they all had normal MAOA genes - except one person. Fallon himself has all the trappings of a psychopath. In an interview for npr.org, he said, "I have the pattern, the risky pattern. In a sense, I'm a born killer."

Fallon describes his upbringing as "terrific," and credits it with stopping him from becoming a psychopath. Of course, this frightening insight into his own character, this realization of what he could have turned into if not for the love and kindness of a doting family, has given Fallon a degree of compassion for those genetically like him who didn't have it so easy. Most of us know to be conscious of the abuse and strife that violent criminals may have endured as children. But a setback as concrete as a genetic predisposition - a defect - is somehow even more deserving of compassion. In the words of Barbara Hagerty for NPR, "Enter the new world of 'neurolaw,' in which neuroscience is used as evidence in the courtroom."

The Pioneer Itch

2010-10-04T10:22:00.025-04:00

NASA launched sister spacecrafts Pioneer 10 and Pioneer 11 in 1972 and '73, respectively. Their joint mission was to gather information about the asteroid belt, as well as Jupiter, Saturn, and their moons. As the probes hurtled past these objects, they measured many properties of their atmospheres and surfaces; they also took beautiful and now famous photographs of Jupiter's red spot and Saturn's rings.

Then, after the Pioneers completed their "flyby" missions, they kept going. Carrying identical plaques depicting a man and a woman, the atomic transition of hydrogen, and the location of the Sun and Earth within the galaxy--a message to aliens--they are now exiting the solar system in opposite directions: 10 heads toward the constellation Taurus, and 11 aims for Aquila.

In 1995, 11 sent its last blip of data back to Earth. 10 stayed in contact longer, sending sporadic bursts of signal until 2003. After their lines went dead and all was said and done, the Pioneers had indeed lived up to their family name. They provided decades of data for scientists to analyze, and from them we have learned a great deal about distant regions of the solar system.

But as NASA scientists sifted through the last signals sent by the spacecrafts from deep space, a problem emerged. It seemed minor at first - just a small discrepancy between the incoming data and the engineers' predictions, which (I assume) must happen occasionally at NASA. But no amount of rechecking the data or reevaluating predictions could force the two to sync up. The divergence wouldn't go away, because it reflected the divergence of the Pioneer spacecrafts themselves.

On their way out of the solar system, as they struggled through the gravitational field of the Sun and planets, the Pioneers were slowing down. Of course NASA expected this: they had made staggeringly precise calculations of the gravitational pull on the spacecrafts at every point in space, and they knew the exact rate at which the probes ought to decelerate during their uphill climb against gravity. The problem was, 10 and 11 were decelerating too much. Each year, they were 5,000 kilometers farther behind where they should have been on their respective paths. 5,000 kilometers is very little in the context of space travel, to be sure, but it isn't trivial. Some additional, undeniable force is pulling the probes inward toward the Sun, a force about 10 billion times weaker than gravity, and we have no idea what it is.

The scientific community caught wind of the so-called Pioneer anomaly in the late 90s, and in the years since, they have studied, theorized, and passionately argued about it via two international conferences and hundreds, or possibly thousands, of academic papers.

Why do they care so much? Well, the thinking is this: the anomalous effect could stem from errors in the machinery of the Pioneers, such as gas leaks, asymmetrical solar heating, or an unaccounted-for force exerted backwards by the probes' radio transmissions. Theoretically, these types of issues could throw things off course, and if NASA plans to execute deep space missions in future, they need to figure out what's going on.

But as engineers go over every detail of the spacecraft designs, analyze every possible source of error, and find no problem, the erroneous machinery explanation seems less and less likely. Alternatively and much more seriously, physics itself, not the spacecrafts, might be broken. The Pioneer anomaly could be our first clue of a mysterious, extremely weak force that exists in the Universe.

Many scientists who've dedicated their careers to contemplating the Pioneer anomaly think NASA ought to plan a mission specifically aimed to test it. If a spacecraft with an entirely different design and instrumentation shows the same lagging effect in deep space as the Pioneers, then the "new physics" explanation of the anomaly moves forward. If a new spacecraft shows no anomalous motion, then the broken Pioneers idea gets a boost.

Until such a mission, scientific fascination mixed with psychological confusion will continue to surround the Pioneer anomaly. Revolutions in physics often stem from results that subtly deviate from predictions, like when the precession of the perihelion of Mercury led to the overthrow of Newtonian mechanics by Einstein's theory of general relativity. The seed of revolution may be germinating once again. But the maddening thing is, maybe it's not!

Connotations of Color

2010-09-28T19:02:00.016-04:00

Check out this infographic displaying the symbolic meanings of colors in various regions of the world. (And see more visualizations made by Dave McCandless at his website, Information is Beautiful.)

The only color connotations consistent across cultures appear to be black for evil, and red for both passion and heat.

Sleep, Wake, Repeat

2010-09-22T22:36:00.019-04:00

In modern society, there is a standard opinion on the matter of sleep: we need, we think, eight straight hours of it each night. Get less than eight and you'll be dozy the next day; wake up for a long time during the night and you have insomnia.

But recently, the results of all those sleep studies your friends have been doing for extra cash have nixed this picture of the ideal sleep pattern. It turns out that the best night of sleep doesn't happen all at once. As Jesse Gamble asserts in the following video, the most natural, restful sleep is instead "biphasic" - it comes in two stages of equal length, separated by one or two hours of quiet, meditative wakefulness in between. This is the pattern humans eventually fall into when freed of the arbitrary structure of artificial lighting.

More shocking than the notion that we're doing it all wrong is the fact that we used to do it right. Until the relatively recent advent of electricity, biphasic sleeping was the norm. From an article by the historian A. Roger Ekirch:

Until the modern era, up to an hour or more of quiet wakefulness midway through the night interrupted the rest of most Western Europeans. ... Families rose from their beds to urinate, smoke tobacco, and even visit close neighbors. Remaining abed, many persons also made love, prayed, and, most important, reflected on the dreams that typically preceded waking from their "first sleep." Not only were these visions unusually vivid, but their images would have intruded far less on conscious thought had sleepers not stirred until dawn. The historical implications of this traditional mode of repose are enormous, especially in light of the significance European households once attached to dreams for their explanatory and predictive powers. In addition to suggesting that consolidated sleep, such as we today experience, is unnatural, segmented slumber afforded the unconscious an expanded avenue to the waking world that has remained closed for most of the Industrial Age.

Erkich presents a great deal of historical evidence in support of his claim, leaving, in my opinion, little doubt that our predecessors were biphasic sleepers. But there are still many open questions on this topic. First, why the societal shift? Even if artificial lighting has something to do with our newfound tendency to sleep through the night, why did we so quickly forget about the "first sleep" and "second sleep" of old?

Furthermore, besides the convenience of a midnight bathroom break and a heightened ability to recall dreams, what true biological benefit does biphasic sleeping bestow?

Scientists will soon be able to answer the latter question by studying the biphasic and polyphasic sleep patterns of other animals, and by conducting further sleep studies on unemployed post-adolescents. In the meantime, why not try out biphasic sleeping yourself? If you do, please report back!

The Silk Renaissance

2010-09-17T18:03:00.007-04:00

Read my feature article, "The Silk Renaissance", here at SEED Magazine.

Self-Organized Criticality

2010-09-12T12:40:00.022-04:00

Most learned people are aware that there is some sort of a connection between financial markets and biological evolution, between earthquakes and stock market crashes. They know it all has something to do with fractals and chaos, and that such connections are the subject of the relatively new realm of science called "complexity theory."

But the general understanding rarely seems to go much deeper. Few truly grasp the common thread tying together all these various phenomena, and scientists themselves clearly have trouble explaining the thread in terms that don't sound vague or wishy-washy. There was a time when complexity theory actually was somewhat wishy-washy; when scientists saw the similarities and patterns between various fields of study but were at a loss as to how or why they arose.

But that time has passed. At this point there is an explanation available that grants a huge amount of clarity about the common processes of the natural world. And unlike the complex systems it explains, the theory isn't all that complicated. Systems as disparate as world economies, rivers, forest fires, earthquakes, the human brain, and even the internet all display a behavior known as self-organized criticality (SOC). Understand SOC, and you will understand a great deal about the relationship between all these different types of systems.

The canonical example of a system that displays SOC is a pile of sand. (The three scientists who "discovered" SOC, Bak, Tang, and Wiesenfeld, used a sandpile model to present their theory to the world in the late 1980s, and it has remained the most straightforward presentation.) You may have noticed, or it may seem right when you think about it, that when you pile up sand at the beach, the slope of the cone of sand you make is always the same no matter how big or small the cone is. Gather up some sand, move your hands away, and the sandpile spontaneously falls into a very regular shape, always with the same slope.

Well it just so happens that this is the "critical slope" of the pile. Sandpiles, like many other naturally-occurring aggregates of a vast number of individual units, are attracted to their so-called "critical point". Without fine-tuning or careful arrangement, they just fall into that state. The critical point is where complex systems like sandpiles want to be.

At the critical point, sandpiles behave in a very peculiar way. If you perturb a pile by dropping a single grain of sand anywhere onto it, literally anything could happen. The grain could either slide down the pile a short distance and stop, it could knock a few grains down with it, or it could cause a huge avalanche and cave in the entire side of the sandpile.

In other words a sand avalanche of any scale is possible, and at the critical point, the severity of an avalanche exactly correlates with how likely it is to occur. Explicitly, the added grain of sand is 10 times more likely to knock 10 grains down the side of the pile than it is to displace 100 grains, and a 100-grain avalanche is in turn 10 times more likely than an avalanche involving 1000 grains. Small avalanches occur more often than big ones, but any size avalanche can and will happen if you spend long enough dropping grains onto the pile.

Slightly more technically speaking, the size of an avalanche is inversely proportional to its frequency. If you dropped grains of sand onto the pile over and over for days and recorded the size of each of the resulting avalanches, then graphed the results, the size-frequency proportionality would emerge. This correlation is known variously as 1/f noise, power law or fractal behavior, and scale-invariance. It occurs because, at the critical point, an infinity appears in the equation governing the behavior of the system, rendering such behavior unknowable. (Those interested in the math of critical points should read more here.)

SOC behavior is exhibited all over nature, wherever small perturbations (like the addition of single grains of sand) happen to large systems (like sandpiles). For example, small vibrations of tectonic plates can cause earthquakes of any size, with a severe earthquake being much less likely than a small one. The price drop of a single stock can have little or no effect on the stock market as a whole, or it can spur a chain of events that leads to a major stock market crash and economic depression. The extinction of a single biological species can bring down five others with it, or five hundred. The firing of a neuron in the brain can die down without effect, or it can cascade and grow into a conscious thought. A military skirmish can lead to a couple of others, or world war. In all these cases, "avalanches" of any size are possible, and with self-organized critical systems there's really no predicting what size avalanche will occur as a result of a given perturbation.

To use one more example, I am "perturbing" the internet by posting this article. I can be confident that this post is more likely to generate a few hundred hits than a few thousand, but who knows. With a chain reaction of Facebook shares and Tweets, anything is possible: thus the allure of blogging!

The brain, the internet, sandpiles, tectonic plates, the weather, stock markets, ecosystems, and literally countless other systems exhibit SOC, but there is as yet no general theory as to what exactly constitutes a system which causes it to self-organize around its critical point. This question occupies many minds and blackboards around the world.

My final observation on the matter of self-organized criticality concerns its relevance. Despite the fact that it explains so much about the way the world works, SOC isn't part of the general lexicon. People don't talk about it. Apart from complexity theorists, even most scientists don't talk about it. This is because scientists are in the business of predicting events in the world around us, and scientific theories have always been valued according to how well the predictions they make match reality. SOC turns this completely on its head. SOC is a theory about the impossibility of prediction. Not only can't SOC tell you how severe the next San Francisco earthquake is going to be, it is telling you that the question isn't answerable. That the earthquake could be any size. That we might as well stop trying to guess.

This kind of message is hard to swallow if you're judging science by its old standards. Self-organized criticality, and complexity theory as a whole, is certainly a new kind of science. It is more relevant than any theory before it as an explanation of how nature works, but not because it provides a means of determining what is going to happen in the future. It can't predict the next event that will occur in a complex system. Instead it predicts the pattern of events spanning the past, present, and future all at once, in no order.

Math on the Walls

2010-09-04T08:48:00.023-04:00

Wallpaper comes in an infinite variety of patterns, from repeating peacocks to intertwined flowers to Escher creatures to simple stripes. Mathematically, though, there are only a finite number of distinct types of wallpaper. It turns out that all the elaborate patterns of the world's walls can be stripped down to their bare bones, analyzed for which symmetries they display, and identified as one or another of exactly 17 so-called wallpaper groups. (Yes, 17 - it appears again.)

Wallpaper is only the historical point of reference for a more general statement about all two-dimensional repeating patterns, including things like tessellations, honeycomb, checkerboards, and chain-link fences too. Long before mathematicians rigorously classified planar patterns as "p4g", "pmm", or any of the other wallpaper groups, the ancient Egyptians discovered and plastered all 17 of them up on the walls of their rooms and tombs.

The classification of the wallpaper groups is based on how individual segments of a pattern, called unit cells, fit together. To determine how they fit, and which group they fit into, you test how you can transform the pattern and still end up with it looking how it did before. You test whether you can translate it (by shifting the unit cells over one place and ending up with the same thing), rotate it, reflect the pattern across a line, or "glide reflect" it, which means reflecting it across a line and simultaneously shifting it.

Based on those four types of symmetries, and which of them a given pattern possesses, it can be categorized in one of the 17 groups. Sometimes it is obvious that two wallpaper patterns are members of the same group, as in this case:

(Group cm - reflections and at least one glide reflection along an axis other than the reflection axes)

And sometimes patterns within the same group look very different:

(Group pmg - two centers of 180 degree rotation, a reflection axis, perpendicular glide reflection axes)

The mathematical proof of there being exactly 17 groups gets rather hairy, but fortunately someone wonderful has created an Applet allowing you to study the wallpaper groups directly: by designing wallpaper patterns of your own in mere seconds. It's fun!

Escher Web Sketch

It Isn't Facism

2010-09-01T16:53:00.020-04:00

Oliver Sacks, author of such brain disorder bestsellers as The Man Who Mistook His Wife for a Hat, has just written a fascinating piece for the August 30th issue of the New Yorker about his own neurological abnormality. Along with an estimated 6 to 8 million people in America alone, Sacks suffers from a condition called "prosopagnosia", or face-blindness.

Sacks cannot recognize people. Even the faces of his nearest and dearest seem like those of total strangers when seen out of context. To recognize family members and friends he must look for characteristic moles, familiar clothing, or haircuts - concrete traits rather than the subtle details to which the rest of us are so well attuned.

Because knowing your friends from your enemies is so important in our species, we have evolved a part of our brains called the "fusiform face area" which is solely responsible for storing and recalling information about human faces. Some people have a really, really heightened face sensitivity; they pass a woman at the supermarket and immediately remember seeing her at a nearby table at a restaurant a week earlier.

At the other end of the spectrum are people like Oliver Sacks. The fusiform face areas of their brains don't work very well, and so to them there is nothing much special about a face. This is my comparison rather than Sacks's, but it seems that for prosopagnosia sufferers, distinguishing between two people's faces is rather like distinguishing between their feet. Of course you can tell two pairs of feet apart if you really look, but bring in a couple more pairs and the clarity fades. We are all basically foot-blind, but some people are face-blind too.

The main interest of Sacks's article for me was a detail about the ways in which we are all partially prosopagnosiac. Recently a psychologist named Olivier Pascalis conducted a study on face recognition in babies. It found that at six months, babies are able to recognize a wide variety of types of faces - those of their own race, other races, and even individual faces within other species of animals. At nine months, however, they have lost some of the diversity in who they will recognize, as if the workings of their fusiform face areas have restricted themselves to face-types most often observed.

The consequence, in Sacks' words, is that "to a Chinese baby brought up in his own ethnic environment, Caucasian faces may all, relatively speaking, 'look the same,' and vice versa."

It is a phenomenon we have all experienced. When I was studying abroad in Ghana, West Africa, nearly every time I was in public with a white friend, no matter how different I thought we looked, someone would invariably ask us if we were twins or at the very least, siblings. They couldn't recognize the distinctions between our European faces. I would feel surprised, but then would find myself assuming the same about many pairs of Ghanaians I met as well.

Thankfully there is a neurological explanation for our foreign-face-blindness, rather than one rooted in inherent racism. It is difficult to tell people apart who are of a race other than our own simply because we didn't develop the skill as babies. Subtle awareness of deviances from an average face takes a great deal of mental resources, and these, of course, must be parsed.

This is Your Web on Drugs

2010-08-28T16:50:00.006-04:00

In 1995 a group of NASA scientists experimented with drugs, literally. They studied the effects that various legal and illegal drugs have on house spiders, and specifically on the way they weave their webs. The results are both surprising and... not.

The spider that was high on marijuana did a fair job weaving, but then got bored or distracted and didn't finish. The one on speed went really fast, of course, but without much awareness of the overall picture: it left large gaps. The acid-trippy spider wove a psychedelic, symmetrical web which was very pretty but not great at catching bugs.

And that brings us to caffeine. Wow. As I sit here typing, a large cup of coffee beside my laptop, I, well, I don't really want it anymore.

The NASA scientists suggested the possibility of analyzing the periodic structure of the spiderwebs (or lack thereof) as a means of determining the relative toxicity levels of drugs. They do not seem to have continued down that road, however; one obstacle may have been the difficulty of extrapolating a given drug's toxicity to humans from its toxicity to spiders. Though similarities between effects on the two species do seem to exist, I'm not sure caffeine makes me feel quite like THAT. In fact, if I wove spiderwebs, that one would probably be pre-morning-cup-of-coffee.

Such questions as what the research had to do with space shuttles or Mars rovers, where the scientists got the drugs, and what happened to the spiders later unfortunately cannot be answered here. The relevant NASA briefs are cited by other academic papers and New Scientist Magazine, but aren't themselves published on the web. The world wide one, that is.

Texas-Sized Trashberg

2010-08-25T18:33:00.016-04:00

Around the time I graduated from high school, a candy bar wrapper got thrown off a dock in Venice Beach, California. As I swirled around America doing various things - going Northeast to college, then South, then West, then East - that wrapper swirled too. All this time it has ridden ocean currents on a clockwise route around the Pacific.

But now, six years later, its estimated time of arrival has arrived, and the wrapper is reaching its final destination. Alongside an unknowable quantity of similar detritus, the wrapper is now bobbing up and down in a stationary region of water in the dead center of the Pacific. It has become part of an ugly, ominous, terrifying mass known as the Great Pacific Garbage Patch.

Estimates range from Texas-sized to more like the area of the entire continental U.S., but it is hard to say quite how big the Patch is because most of it isn't even visible. There are certainly large pieces of flotsam floating on top, but the greater danger is a dense layer of confetti-like plastic lurking beneath the ocean surface. Plastic breaks down over time into smaller and smaller bits, leaching toxic chemicals as it degrades. Eventually the bits become small enough to be devoured by plankton, at which point they enter the food chain.

Scientists believe most of the trash that converges in the Great Pacific Garbage Patch washes out to sea from land, but some is dumped from ships. A single 3,000 passenger cruise ship produces 8 tons of solid waste per week, for instance, and some of this gets expelled into the ocean.

In the past two years, several research projects have started work to determine the feasibility of cleaning up the Pacific Patch. Unfortunately, though, just as we have begun to address the trashberg in the Pacific, a garbage patch almost as large has been discovered in the middle of the Atlantic.

Fact: We should really, really stop using synthetic polymers.

Ants Count

2010-08-22T15:50:00.012-04:00

When desert ants go foraging, any scent trails they lay down immediately get swept away by the wind. Scientists have long wondered how they make it back to their nests without smelling their way there. An ingenious experiment by biologists at the University of Ulm leads to the conclusion that the ants must be navigating by numbers. With some sort of internal pedometer, they - and possibly many species of ants - count their steps to keep track of how far afield they've ambled, and count backwards to get home.

Ebb and Flow

2010-08-14T16:55:00.012-04:00

We all know the tides are caused primarily by the Moon's gravity. But why are there two tidal cycles every day instead of one? And why do the tides vary in height throughout the year, and from year to year as well?

See these questions answered by a chocolate "biscuit", a pickled onion, an orange, and a British man in just 2 minutes.

Auld Acquaintances

2010-08-09T21:28:00.015-04:00

Only the craziest among us have trouble distinguishing our own hands from the hands of a stranger. Our "sense of self" is so strong - stronger, perhaps, than the five senses with which we experience the external world - that we understand our own physical extent without so much as a conscious thought.

But that sense of self is an emergent phenomenon; of course it doesn't exist at the cellular level. In the bacterial battlefield that is our stomach, there is little to distinguish cells of the homeland from those of the enemy, and especially if the distinguishing is left up to an army of deaf, dumb, and blind white blood cells. In fact it is almost unbelievable that our immune systems work at all, that antibodies usually "know" which cells to defend and which to attack. How do they know?

Well, very often they don't. Rheumatoid arthritis, lupus, and type 1 diabetes are but three varieties of a condition called autoimmunity, which is marked by a person's immune system failing to recognize that person's own constituent parts and consequently attacking them. The immune systems of 1 in 12 people in the U.S. behave in this self-destructive manner, and we don't know quite why. The only compelling theory about why autoimmune diseases occur (and why they usually don't) stems from the bizarre fact that their incidence goes up, instead of down, in direct proportion to a country's standard of living.

I might have suspected an excess of hypochondria, but scientists think it's rather an absence of parasites, specifically hookworms, that is throwing off the immuno-balance of the industrialized world. Known as the "old friends hypothesis", it holds that humans and hookworms evolved symbiotically. Because we've dealt with them for the whole of our evolutionary history, we have actually come to rely on them to sort a few things out in our immune systems. For example, there is evidence that the parasites stimulate the performance of regulatory T cells, which are responsible for suppressing unnecessary immune reactions.

Today, an estimated two billion people are infected with hookworms worldwide. Though the repulsive creatures cause grave discomfort and malnutrition, many scientists wonder which devil is worse: the one we've known for millions of years, or the new one, born of hygiene. In 2004, Caroline Hadley addressed this question in a paper with a title that put it best: "Should auld acquaintance be forgot?"

Upward Spiral

2010-08-05T09:50:00.016-04:00

They say you have to hit rock bottom before you start to rise back up. Don't take this as fact, but rock bottom is where I imagine the mathematician Stanislaw Ulam making his most interesting discovery.

"I've got nothing!" he might have lamented, as he scrawled numbers in a spiral to kill time...

"Wait a second... why are all the primes on diagonals?"

Primes, the natural numbers that are not multiples of anything smaller, are an endlessly fascinating set. Any number can be written as the product of primes (for example, 33 = 3 x 11). Thus they are the "atoms" of the math world - the irreducible numbers from which all others are constructed.

Furthermore, a whole gammit of crazy statements seem to be true about them, though many can't be proven: There is at least one prime between any number and twice that number. There are an infinite set of primes, the largest currently known being 4 million digits long. There are even an infinite set of "twin primes" which are separated by 2, like 29 and 31. Another unproven but seemingly true conjecture is that every even number (besides 2) is the sum of two primes, which is quite unrelated to other multiplicative properties.

And like Ulam noticed, primes appear along diagonals when numbers are written in a spiral. In this large block of spiraling numbers, the white dots are primes.

Stranger still is the fact that some diagonals are more strongly prime than others. Why should this be? Unfortunately there's no telling; we really don't understand the distribution of the primes. But if we had to convey our intelligence to an alien life form, many scientists think the best way would be to demonstrate our knowledge of these incredible numbers. As the building blocks of math, they are the true universal language.

Centerpoint

2010-08-02T07:07:00.019-04:00

Astronomers of the past went to absurd lengths to justify placing the Earth at the center of their models of the cosmos. Belief in God, and the assumption that He would give us pride of place, were so entrenched that the mark of a viable astronomical theory was its ability to explain away any counter-evidence.

We now know the Sun rather than the Earth lies at the center of our Solar System. (The Catholic Church was the last to come around; they didn't admit that Galileo was right until 1992.) However, even though the Earth isn't at the center of the Solar System, it is at the center of the Universe.

Because everything is! Every point in the Universe can be thought of as its center - the point from which it expands outward.

If you've heard this before but have a hard time getting to grips with it, that's probably because there are too many dimensions involved. I have a hard time contemplating three dimensional expansion, but thinking about a 2-D Universe expanding is easy:

In this analogy the Universe is the balloon, and the dots are galaxies and the people in them. As the Universe expands, the dots get further and further apart. No one dot is at the center but rather space expands away from all of them.

Furthermore, traveling in a straight line along the surface of the balloon for long enough would bring you back to where you started.

The actual Universe is the 3-D analogue of the surface of a sphere. Each point in 3-D space acts as its center; traveling in a straight line eventually brings you back to your starting point. Unfortunately there is no way to draw a 3-D "surface" embedded in four dimensions, so we must content ourselves with the inklings of understanding we get from analogies.

The Other Hand

2010-07-27T06:16:00.034-04:00

Lefties don't have it easy in this world. It is littered with invisible obstacles. Even race tracks, which seem such equitable venues for human competition, favor people who are right-side dominant. Since their right legs can take longer strides than their left ones, they turn more easily through leftward curves. Thus most runners finish faster going counterclockwise than clockwise and eventually the former became the right way around.

Furthermore it's no coincidence that "right" - which comes from the Anglo-Saxon word riht meaning "correct" - is also the word for the dominant hand of most people. "Left" comes from the Anglo-Saxon lyft, meaning weak or useless. Such connotations can be observed in many languages: Words for right tend to be synonyms for things like justice, strength, and skill, while those for left signify clumsiness, awkwardness, wrong, and evil.

Though negative feelings toward left-handed people have abounded throughout history, and in some places continue to do so today, we southpaws have still managed to do well for ourselves. Lefties include an impressive list of high achievers, and are hugely overrepresented among Nobel Prize winners, U.S. Presidents, and famous artists, athletes, and academics. Lefties are often credited with having "a wider scope of thinking" which enables greater abstraction. But what does that mean? What does handedness have to do with thought? And why are there lefties - or righties for that matter - in the first place?

Handedness results from asymmetry in the brain. The region that controls language and speech is located in the left brain hemisphere in most people. Since speech and dexterity require similar types of finesse, it is assumed that these skills are controlled together (by the left hemisphere). Since that hemisphere is more neurally connected to the right side of the body, the right side usually ends up possessing more finely tuned motor skills.

The brains of lefties, though, are not simply mirror images of those of right-handed people. The division of labor in their brains tends to be much less cut-and-dry. For example, speech is controlled by the left hemisphere of about half of left-handed people's brains, just like it is for everyone else, while dexterity seems to be controlled on the right side. Another fourth of lefties' brains divide speech processing between the two hemispheres, probably handling dexterity on both sides as well.

This ambiguity may imply more connectivity between different brain regions, engendering abstract thinking (as well as higher rates of mental illnesses like schizophrenia).

What causes the brain to sometimes switch up or mix around? There is no clear consensus on the matter, just several interesting hypotheses. First of all, left-handedness is barely genetic. A child of two left-handed parents has only a 26% chance of being left-handed: higher than the 1-in-10 incidence in the general population, but not that much higher. Some scientists think left-handedness is caused by more testosterone than usual flooding the fetus at a critical moment during gestation. This would explain the higher incidence of left-handedness in males than females, and it could also relate to the putative evidence of a correlation between handedness and sexual orientation. However, the way in which testosterone influences brain lateralization isn't established.

One major evolutionary advantage of being left-handed is greater prowess in combat. Studies have shown that lefties are over-represented among violent or war-torn populations, implying that they do better in battle. This could have to do with the unexpected or unusual style in which they are biologically bound to fight, but it also points to heightened spatial awareness as well as greater ambidexterity. Considering how much of human history has been spent in combat, the following question comes to mind: Why isn't everybody left-handed, or better still, ambidextrous? Why is the right-handed model the prevalent one? Therein lies the ultimate unanswered question when it comes to handedness.

Please pass this article along to any lefties you know: We tend to be more interested in discussions of handedness than anybody else!

The Side Most Don't See

2010-07-22T05:17:00.011-04:00

Topology is the mathematics of morphing surfaces. It asks whether objects which look very different are actually the same: whether one can be turned into the other by way of a little twisting and stretching, or, on the other hand, if morphing one object into the other requires its surface to be cut.

To a topologist, it is obvious that a circle can be swelled out at the sides to make an ellipse, but that you can't get the twist out of a Mobius strip without tearing it. Because a torus can easily deform into a cylinder with a handle, a classic math joke is to say that topologists can't tell their donuts from their coffee cups.

Topology is a strange field, but one that appears all over the math and physics landscape; it has applications in general relativity, group theory, string theory, and a huge range of other areas. Though a rigorous understanding of topology requires years of training on top of a generous dose of inherent spatial awareness, anyone can get a sense of how it might be to think topologically by watching this wonderful video:

It's 20 minutes long but I found I couldn't stop watching. The clip demonstrates why a circle can't be turned inside out but why a sphere can - and how. Incidentally, the topologist Bernard Morin, who was key in developing this method of sphere eversion, was blind.

From Rats to Cats to Cat Ladies

2010-07-20T19:20:00.010-04:00

Guest Post by Aaron Wacks

For some strange, unexplainable reason, Facto Diem's post on slug sex reminded me of a terrifyingly powerful wizard known as Toxoplasma gondii. If you have not heard of these parasites, then please heed this warning: they are vile, terrifyingly evil creatures.

Let’s take a brief look at their life.

Stage I: Babies!

Innocent sporozoite babies are usually spread into stomach tissue of scavengers such as mice, rats, and nappy San Francisco Mission District pigeons. Eager to learn, they spread and multiply. After a few days of maturing, during which time they experiment with eye makeup, the Jonas Brothers, patchouli, and reefer, the small army of parasites forms cysts in the liver, muscles, and BRAIN of the carrier.

Stage IIa: Disgusting cyst-forming teenagers

“You darn kids, get off my lawn!” says the poor hard-working rodent.

Stage IIb: Vandals, and Evil Shamans

Studies have shown that Taxoplasma gondii-infected rats are more likely to favor a dwelling that smells like cat pee than their own rat pee. Cats become their obsession. The carrier rats go crazy, but it’s not their fault: Through voodoo techniques of some sort, T.G. causes the brain to lose fear-causing hormones such as dopamine and corticosterone which would normally make rats steer clear of felines. Dumb prey makes for easy prey, which is just what those cracky-voiced, pimply little parasites want at this stage in their lives.

Stage III: Move-in day: The Mansion in Wis-can-sin

A cat’s intestine is actually a parasitical sexual palace. The T.G. cells draw straws to see who gets to be sexual (gametocytes) and asexual (tachyzoites). Then they make babies. It’s not pretty. I won’t tell you any details. The babies are eventually pooped out by the cat for scavengers to find, and thus, the cycle begins again!

Please watch this video for more information on the subject.

Epilogue:

You might be thinking, “Oh that’s cute,” but humans are not safe! Around half the human population has been infected by Toxoplasma gondii. If you know someone who suddenly starts acting crazy, you should ask him or her if they have a cat. Drivers infected with Toxoplasma gondii are twice as likely to get in an automobile crash. Think of all the other horrible impaired decisions you might make (Scientology, capris, free beef at the carwash, and the list goes on!).

Some scientists are even going so far as to say this parasite is affecting human culture by changing a huge percentage of the world population's personalities. If the effect is to make people dumb and complacent, this means we can blame collective choices like Crocs and the Bush administration on parasites!

Whosits and Whatsits Galore

2010-07-18T16:31:00.031-04:00

As pretty and majestic as birds are, I find it difficult to sense much of an interspecies connection when I look into their rather steely eyes. Feeling connected is what makes me care, so I was recently excited to learn about an avian species Jared Diamond has called "the most intriguingly human of birds." The bowerbird, which lives in and near Papua New Guinea (like so many gems of evolutionary biology), is anthropomorphous to say the least.

Whereas many other birds sport flashy colors on their feathers to attract mates, bowerbirds are dull and brown like us. They must therefore accumulate their flashiness instead - also like us.

Males build elaborate huts, then decorate them with enormous collections of shiny and colorful trinkets. Depending on individual tastes they may choose to adorn their premises with piles of berries, stones, dead beetles, nice looking leaves, glass, brightly colored trash, and so on. The birds' collections are fastidiously arranged and maintained.

With their goods on display, the males await the arrival of females, whose role it is to assess their assorted items. On the basis of the aesthetic quality of a male's possessions, the female chooses whether to mate with him... or to fly on in search of sexier piles.

Photos by Tim Laman for National Geographic. More here.

Y or Woman

2010-07-13T12:35:00.017-04:00

Everyone receives an X sex chromosome from their mother. Females get a second X from their father and males get a Y, and from this disparity arise all the differences observed to exist between the sexes, controversial or otherwise.

The XX and XY chromosomal dichotomy was discovered over 100 years ago, but it has taken the century since then to uncover the subtle ways in which the sex chromosomes engender, well, gender.

First, in 1947, a French endocrinologist named Alfred Jost removed the testes from male rabbit fetuses while they were in the womb. (I have no idea how.) He found that the rabbits subsequently changed course and developed into females.

Then in 1959 it was observed that people with Turner's syndrome, who have a single X sex chromosome, develop as females.

It was becoming clear that it isn't primarily the presence of a second X that makes females female, but rather the lack of hormones produced by the Y. In 1990, scientists confirmed this hypothesis by locating what became known as the Sex-Determining Region of the Y chromosome (SRY).

The SRY set of genes dictate the production of proteins and hormones that make certain glands in the fetus turn into male reproductive organs. If the instructions in the form of the Y chromosome aren't there, or if they're inhibited as in the case of Jost's experiments with rabbits, the fetus develops as a female - as if this is the "default" template for sexual development.

Furthermore, the SRY genes must continue producing hormones during a male's maturity in order to keep him on the track of being male. If hormonal dosages are ineffective or insufficient, a male child may begin to change course and develop according to the female template.

Recent findings have complicated the picture slightly. Some anti-male genes have been identified on the X chromosome which must be counteracted by SRY genes, and vice versa for anti-female genes on the Y that get inhibited by genes on the X. But regardless of these more complex interactions, the default female template idea continues to capture the essence of the sex-differentiation process.

Strangely, the theory that gender differentiation arises from either an expression of maleness during reproduction (in the case of males) or lack thereof (in the case of females) was first proposed by Aristotle in ancient times, based on no evidence at all.

Non-Diem

2010-07-11T09:49:00.003-04:00

Hello! Due to a combination of traveling and spending more time working on my book, I won't be able to write daily posts for a while. I'll definitely post interesting facts whenever I get the chance, but, at least for the time being, the title of the blog will have to be a misnomer. Please keep checking the page and sending fact ideas when you have them! Thanks for all the great feedback.

Here's Feynman on how trains stay on their tracks.