Thursday, November 26, 2015
Sadie Stein in The Paris Review:
This vintage video from the U.S. Department of Agriculture actually gives a very good primer on carving—frankly, it’s the best guide I’ve found, and the thigh-meat trick is indeed neat, even if the announcer’s chummy tone can grate. (Be sure to watch long enough to hear him intone, “There goes that drumstick for a hungry boy!”)
But it raises other questions. Mainly: What is “turkey time,” and why is it separate from “carving time”? Best of all is the rather menacing, passive-aggressive coda: “You can carve without these directions, but you can probably carve better with them.” As a random drunk in a bar once slurred at me when I said I didn’t want to go to the pier with him, “Fine, whatever, just thought you might want to see the Statue of Liberty!”
Wanderer, your footsteps are
the road, and nothing more;
wanderer, there is no road,
the road is made by walking.
By walking one makes the road,
and upon glancing back
one sees the path
that must never be trod again.
Wanderer, there is no road—
Only wakes upon the sea.
by Antonio Machado
Wednesday, November 25, 2015
Maria Popova reviews Lisa Randall's Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe in The NYT Book Review:
A good theory is an act of the informed imagination — it reaches toward the unknown while grounded in the firmest foundations of the known. In “Dark Matter and the Dinosaurs,” the Harvard cosmologist Lisa Randall proposes that a thin disk of dark matter in the plane of the Milky Way triggered a minor perturbation in deep space that caused the major earthly catastrophe that decimated the dinosaurs. It’s an original theory that builds on a century of groundbreaking discoveries to tell the story of how the universe as we know it came to exist, how dark matter illuminates its beguiling unknowns and how the physics of elementary particles, the physics of space, and the biology of life intertwine in ways both bewildering and profound.
If correct, Randall’s theory would require us to radically reappraise some of our most fundamental assumptions about the universe and our own existence. Sixty-six million years ago, according to her dark-matter disk model, a tiny twitch caused by an invisible force in the far reaches of the cosmos hurled a comet three times the width of Manhattan toward Earth at least 700 times the speed of a car on a freeway. The collision produced the most powerful earthquake of all time and released energy a billion times that of an atomic bomb, heating the atmosphere into an incandescent furnace that killed three-quarters of Earthlings. No creature heavier than 55 pounds, or about the size of a Dalmatian, survived. The death of the dinosaurs made possible the subsequent rise of mammalian dominance, without which you and I would not have evolved to ponder the perplexities of the cosmos.
Paul Churchland reviews Richard Rorty's Mind, Language, and Metaphilosophy: Early Philosophical Papers in Notre Dame Philosophical Review:
This glowing collection includes Rorty's earliest publications -- from 1961 through 1972 -- and his earliest attempts to deal with the broad landscape of problems that engulfed our discipline in the second half of the 20th Century: most centrally (for Rorty), analytical reductionism, the mind/body problem, the distinguishing or defining feature of the mental, and the proper methodology for philosophy itself. The arc of Rorty's adventures here mirrors the arc of our professional concerns generally in that period, not least because Rorty was an influential contributor to those discussions, but also because he addressed in depth the work of his most prominent philosophical contemporaries, such as Carnap, Wittgenstein, Ryle, Strawson, Sellars, Quine, and Dennett. His insightful commentaries on these figures, and others, are worth the price of this collection all by themselves.
But a larger issue shapes the relevance of Rorty's essays here. Despite an initial philosophical education that was decidedly classical, Rorty was captured by C.S. Peirce's late 19th-century pragmatism, a philosophical perspective that never left him. And that fertile perspective dominates all of his philosophical activity throughout these essays. For example, given the basic pragmatist conviction that the ultimate function of cognitive activity is to survive in and to navigate the peculiar environment in which one happens to be embedded, a philosopher is very unlikely to find plausible a story that attempts to reduce or translate all empirical statements into a unique and philosophically basic vocabulary of sensory simples. For the sensory vocabulary we happen to use is also plastic, is also in the business of helping us to navigate the world, and is ultimately to be evaluated by the pragmatic virtues that drive and select our conceptual resources generally. Understanding our sensory access to the world is indeed of major importance, and it commands constant evaluation and reevaluation. But our first-person sensory judgements themselves do not constitute an independent touchstone, forever free from pragmatic evaluation. According to Rorty, they are an integral part of the overall epistemic contest. Classical empiricism is thus pushed aside.
Over at Todd W. Schneider's website:
NYC Taxi Data
The official TLC trip record dataset contains data for over 1.1 billion taxi trips from January 2009 through June 2015, covering both yellow and green taxis. Each individual trip record contains precise location coordinates for where the trip started and ended, timestamps for when the trip started and ended, plus a few other variables including fare amount, payment method, and distance traveled.
I used PostgreSQL to store the data and PostGIS to perform geographic calculations, including the heavy lifting of mapping latitude/longitude coordinates to NYC census tracts and neighborhoods. The full dataset takes up 267 GB on disk, before adding any indexes. For more detailed information on the database schema and geographic calculations, take a look at the GitHub repository.
Thanks to the folks at FiveThirtyEight, there is also some publicly available data covering nearly 19 million Uber rides in NYC from April–September 2014 and January–June 2015, which I’ve incorporated into the dataset. The Uber data is not as detailed as the taxi data, in particular Uber provides time and location for pickups only, not drop offs, but I wanted to provide a unified dataset including all available taxi and Uber data. Each trip in the dataset has a
cab_type_id, which indicates whether the trip was in a yellow taxi, green taxi, or Uber car.
Borough Trends, and the Rise of Uber
The introduction of the green boro taxi program in August 2013 dramatically increased the amount of taxi activity in the outer boroughs. Here’s a graph of taxi pickups in Brooklyn, the most populous borough, split by cab type:
From 2009–2013, a period during which migration from Manhattan to Brooklyn generally increased, yellow taxis nearly doubled the number of pickups they made in Brooklyn.
Once boro taxis appeared on the scene, though, the green taxis quickly overtook yellow taxis so that as of June 2015, green taxis accounted for 70% of Brooklyn’s 850,000 monthly taxi pickups, while yellow taxis have decreased Brooklyn pickups back to their 2009 rate. Yellow taxis still account for more drop offs in Brooklyn, since many people continue to take taxis from Manhattan to Brooklyn, but even in drop offs, the green taxis are closing the gap.
Ed Yong in The Atlantic:
Take a slice of cake and cut it in two. Eat one half, and let a friend scoff the other. Your blood-sugar levels will both spike, but to different degrees depending on your genes, the bacteria in your gut, what you recently ate, how recently or intensely you exercised, and more. The spikes, formally known as “postprandial glycemic responses” or PPGR, are hard to forecast since two people might react very differently to exactly the same food.
But Eran Elinav and Eran Segal from the Weizmann Institute of Science have developed a way of embracing that variability. By comprehensively monitoring the blood sugar, diets, and other traits of 800 people, they built an algorithm that can accurately predict how a person's blood-sugar levels will spike after eating any given meal.
They also used these personalized predictions to develop tailored dietary plans for keeping blood sugar in check. These plans sometimes included unconventional items like chocolate and ice-cream, and were so counter-intuitive that they baffled both the participants and dieticians involved in the study. But they seemed to work when assessed in a clinical trial, and they hint at a future when individuals will get personalized dietary recommendations, rather than hewing to universal guidelines.
John McWhorter in Aeon:
English speakers know that their language is odd. So do people saddled with learning it non-natively. The oddity that we all perceive most readily is its spelling, which is indeed a nightmare. In countries where English isn’t spoken, there is no such thing as a ‘spelling bee’ competition. For a normal language, spelling at least pretends a basic correspondence to the way people pronounce the words. But English is not normal.
Spelling is a matter of writing, of course, whereas language is fundamentally about speaking. Speaking came long before writing, we speak much more, and all but a couple of hundred of the world’s thousands of languages are rarely or never written. Yet even in its spoken form, English is weird. It’s weird in ways that are easy to miss, especially since Anglophones in the United States and Britain are not exactly rabid to learn other languages. But our monolingual tendency leaves us like the proverbial fish not knowing that it is wet. Our language feels ‘normal’ only until you get a sense of what normal really is.
There is no other language, for example, that is close enough to English that we can get about half of what people are saying without training and the rest with only modest effort. German and Dutch are like that, as are Spanish and Portuguese, or Thai and Lao.
Greg Rienzi in HUB:
Math as both profession and course of study can be a hard sell, something even Don Draper might have trouble pitching. The field unites numbers, theories, and ideas that, yes, can be physically represented but remain intangible. Math is a language unto itself that for some might as well be Latin or Klingon. Even its rare turns in popular culture—A Beautiful Mind,Proof, and The Big Bang Theory come to mind—typically depict brilliant but troubled and/or socially handicapped thinkers more absorbed by theory than reality.
To Richard Brown, however, math can be as beautiful as a ray of morning sunlight cast upon an orchid's petals, as lyrical as a Beethoven symphony. "Math is not about the numbers," says Brown, director of undergraduate studies in Department of Mathematics at Johns Hopkins University. "It's the ideas behind the numbers. Yes, you can say it's built on a rigid set of rules, but out of that comes an infinite amount of creativity." And, he adds, beauty.
In recent years, Brown has served as math spokesman of sorts. Last year, he presented a talk at the inaugural TedxJohnsHopkinsUniversity titled "Why Mathematics?". He opened up with a question: "Why on earth would anyone choose math as a field of discipline to study, or construct a career in the field?"
UC San Francisco researchers have discovered that even brainless single-celled yeast have “sensory biases” that can be hacked by a carefully engineered illusion — a finding that could be used to develop new approaches to fighting diseases such as cancer. In the new study, published online Thursday November 19 in Science Express, Wendell Lim, PhD, the study’s senior author*, and his team discovered that yeast cells falsely perceive a pattern of osmotic levels (by applying potassium chloride) that alternate in eight minute intervals as massive, continuously increasing stress. In response, the microbes over-respond and kill themselves. (In their natural environment, salt stress normally gradually increases.) The results, Lim says, suggest a whole new way of looking at the perceptual abilities of simple cells and this power of illusion could even be used to develop new approaches to fighting cancer and other diseases.
“Our results may also be relevant for cellular signaling in disease, as mutations affecting cellular signaling are common in cancer, autoimmune disease, and diabetes,” the researchers conclude in the paper. “These mutations may rewire the native network, and thus could modify its activation and adaptation dynamics. Such network rewiring in disease may lead to changes that can be most clearly revealed by simulation with oscillatory inputs or other ‘non-natural’ patterns. “The changes in network response behaviors could be exploited for diagnosis and functional profiling of disease cells, or potentially taken advantage of as an Achilles’ heel to selectively target cells bearing the diseased network.”
Jacqueline Feldman in Harvard Magazine:
As Of Men and War opens, a trumpet moans and won’t resolve into taps, and a van traps men who let it bounce them. They rarely come to town, they say. They are quick to road rage. They wear sunglasses. Later, one man tells his wife, “If we never had to leave the house, I’d be all right, but it’s going outside I can’t handle too much.” The French documentary (released in many U.S. cities this week after playing at theaters in France and at international festivals), follows veterans of Iraq and Afghanistan as they undergo trauma therapy at a residential center called Pathway Home, founded by therapist Fred Gusman. These characters are archetypal—“almost mythological”—says Isidore Bethel ’11, the head editor for the film and one of its associate producers: “These men could have served in any war.” Their transposition into an older pantheon of suffering is nimble. The contemporary term “PTSD” is used exactly twice, once by a vet guilt-tripping a too-persistent caller and then by another vet’s wife. Otherwise, no character mentions diagnoses or pills, only men and death and their closeness to it.
Of Men and War is the second film in Laurent Bécue-Renard’s series A Genealogy of Wrath. As a young man, the director spent several months in besieged Sarajevo for “purely romantic” reasons. He found the city’s high pitch catching and vaguely familiar. There, while writing news dispatches and short stories, he met a therapist who worked with war widows. He focused on three of these women for his first documentary, War-Wearied (2003). It dawned on him that a personal “quest” had drawn him to his project. His grandfathers served in the First World War, which killed some 1.7 million French, about 5 percent of the country’s population. “All of us who grew up in the second half of the twentieth century inherited the legacy of the wars in the first part of the twentieth century,” Bécue-Renard said. “It has been shaping the psyches of the families we belong to.”
……… Alone together a moment
on the twenty-second anniversary
……… of their wedding
he clasped her as she stood
……… at the sink, pressing
into her backside, rubbing his cheek
……… against the stubble
of her skull. He gave her a ring
……… of pink tourmaline
with nine small diamonds around it.
……… She put it on her finger
and immediately named it Please Don’t Die.
……… They kissed and Jane
whispered, “Timor mortis conturbat me.”
by Donald Hall
Mariner Books, 1999
Tuesday, November 24, 2015
On the eve of the 100th anniversary of the publication of General Relativity by Albert Einstein, Sean Carroll asks, "Einstein's legacy: if spacetime is dynamical rather than absolute, what else about the universe might be flexible?" at PBS Newshour:
Nicolaus Copernicus is famous for having suggested that the Earth moves around the sun, rather than the other way around. That’s a big deal, as it displaces the Earth from its presumed position at the center of the universe. But it’s easy for us to forget something equally amazing: the idea that the Earth can actually move at all. If anything seems like a solid foundation, it’s the Earth itself. But in our post-Copernican world, we know better.
Albert Einstein, with his general theory of relativity, took this conceptual revolution one step forward. Not only is the Earth not a fixed fulcrum around which the rest of the universe revolves, space and time themselves are not fixed and unchanging. In Einstein’s universe, space and time are absorbed into a single, four-dimensional “spacetime,” and spacetime is not solid. It twists and turns and bends in response to the motion of matter and energy. We perceive that stretching and distortion of the fabric of spacetime as the force of gravity.
The idea that space and time themselves are not immutable, but are dynamical quantities that can evolve through the history of the universe, is one of Einstein’s most dramatic legacies. It was so profound that Einstein himself had trouble accepting all the implications of the idea. When he investigated the universe as a whole in general relativity, he found that it should be expanding or contracting, not staying at a fixed size. That went contrary to his intuition, as well as to what astronomers of the time actually thought the universe was doing. When Edwin Hubble discovered the expansion of the universe in the 1920’s, Einstein realized that he had missed the opportunity to make one of the great predictions in the history of science.
The longer I looked at the painting the more I was drawn to the dialogue taking place, sotto voce, between the over-coloured count and his shadowy double hung high on the wall above him – a faintly preposterous rehash of the mirror in Las Meninas, where king and queen make their necessary appearance. The dialogue in Goya – the shadow play, the hovering between repetition and caricature – seemed to me to drain both parties (I presumed that the figure on the wall was an ancestor, or maybe the monarch himself) of reality. The second man staring at me – again, a version of a great moment in Las Meninas, where Velázquez in the background fixes his royal sitters with a predatory gaze – seemed to peer from the picture with an expression compounded of alarm, disbelief and sheer uncomfortable consciousness of his place in a game of looking. Looking and being looked at and thereby ‘brought to life’. He’d be damned if he’d occupy the place he’d been allotted. I found myself staring back at the painting in much the same frame of mind. The more I responded to Floridablanca’s local (stunning) reality effects – the silver shimmer on the count’s sash, the light through the glass on the clock face, the spectacles clutched in his fingers, the Zurbarán notebook glowing on the floor – the more it seemed to me they didn’t matter. What mattered – what made the painting Goya’s – was the pervasive unreality of the set-up, swallowing the world of objects and persons no sooner than it conjured them up.
I realise that I haven’t put my finger on what produced the feeling of unreality, and I’m not sure I can. I know there are dangers in trusting the feeling at all. Anyone looking at Goya’s portraits can’t avoid seeing them against the background of the Caprichos and Black Paintings and the unbearable private albums, some drawn, some etched and aquatinted, dwelling on torment and degeneracy.
Fourteen years after September 11, the reality-concealing rhetoric of Westernism participates in a race to extremes with its ideological twin, in an escalated dialectic of bombing from the air and slaughter on the ground. It grows more aggressive in proportion to the spread of the non-West’s chaos to the West, and also blends faster into a white supremacist hatred of immigrants, refugees, and Muslims (and, often, those who just “look” Muslim). Even more menacingly, it postpones the moment of self-reckoning and course-correction among Euro-American elites who seem to have led us, a century after the First World War, into another uncontrollable and extensive conflagration.
Among the more polished examples of their intellectual rearguardism last week was a piece in the Financial Times by the paper’s foreign-affairs columnist, Philip Stephens, titled “Paris attacks must shake Europe’s complacency. The idea that the west should shoulder blame rests on a corrosive moral relativism.”
It should be said that the Financial Times, the preferred newspaper of the Anglo-American intelligentsia as well as Davos Man and his epigones, keeps a fastidious distance, editorially, from the foam-at-the-mouth bellicosity of its direct competitor, the Wall Street Journal (whose op-ed pages often seem to be elaborating on its owner’s demented tweets).
Among the dozen useful masterpieces chosen by the US Postal Service for its 2011 series of stamps honoring American industrial design pioneers is the Normandie water pitcher (1935), a sleek chromium-plated vessel whose prow-like form echoes that of the then-new French ocean liner for which it was named. This stunning work, manufactured by the Revere Copper and Brass company, evokes the glamour of interwar transatlantic travel with a sculptural purity worthy of Brancusi, and is rightly included in numerous design history books and museum collections. Yet until now the general public has known next to nothing about its creator, Peter Muller-Munk.
That lapse is finally redressed by “Silver to Steel: The Modern Designs of Peter Muller-Munk,” an illuminating exhibition at Pittsburgh’s Carnegie Museum of Art. It vindicates the personal crusade of the Miami-based design historian Jewel Stern, an intrepid researcher of this overlooked figure and the co-curator of the show.
Danny Lewis in Smithsonian Magazine:
At first glance, Faig Ahmed’s carpets look like digital photos that didn’t load right the first time you clicked on them. Intricate patterns morph into messes of pixelation; blocks of color slide off like someone scrolled past them too fast; and some of the 2D mats look like they are bulging off a screen. But while they may appear to be software glitches or bad Photoshop editing, every one of Ahmed’s carpets are hand-woven – bugs and all.
Ahmed is an Azerbaijani artist who takes inspiration from traditional carpets made by craftsmen in his country. The artisanal carpets are made with intricate patterns and vibrant colors, both of which inspired Ahmed to begin working in textiles after years of focusing on paintings, video and installation art, Kate Sierzputowski writes for Colossal.
“Patterns and ornaments can be found in all cultures, sometimes similar, sometimes very different,” Ahmed tells Sierzputowski. “I consider them words and phrases that can be read and translated to a language we understand.”
Azerbaijani carpets are a prized around their world both for their beautiful patterns and the craftsmanship it takes to create such detailed, delicate pieces. The skills used to make the carpets are passed down through generations by family members, according to UNESCO. Traditionally, the carpets are dyed and woven in the winter by female household members who use special techniques to create intricate designs in the fabric. Carpets are often made to celebrate special occasions like weddings, a child’s birth and religious rites. Although the carpets carry much cultural significance, Ahmed takes pleasure pushing the craft's boundaries in his artwork.
Ken Roth in Politico:
The horrendous Paris attacks have provided certain European and U.S. politicians with an irresistible opportunity to attempt to close the door on refugees while seeking to expand overbroad government surveillance. It is important, out of principle and for our collective safety, to reject these appeals to fear and prejudice, as some political leaders have done.
A fake Syrian passport reportedly left behind by an attacker of unknown identity and nationality suggests that he entered Europe with the recent refugee flow. The presence of the passport may reflect a deliberate effort by the so-called Islamic State to stigmatize the people who dare flee its “caliphate.” It has led to a chorus of voices seeking to keep out refugees and asylum-seekers, despite the fact that theattackers identified so far have turned out to be citizens of Belgium and France.
The focus on refugees in the aftermath of the recent attacks is a dangerous distraction from Europe’s violent home-grown extremism. The roots of the problem are notoriously complex but relate in part to the social exclusion of past generations of immigrants — the persistent discrimination, hopelessness, and despair that pervades neighborhoods on the outskirts of certain cities.
The Grave, The Mine
Taking off from the city
at night, from the
airplane, I look at streetlights
below: hovering unfixed
sockets of light.
Then it is black beneath me.
A pair of headlights
veer slowly along a macadam
far from pianos and theaters.
Women are leaning back in taxis
Men stoop into taxis after them
and enter the well, the
grave, the tunnel, the mine
of fur and scent.
by Donald Hall
from Poetry Magazine
Carl Zimmer in The New York Times:
The agricultural revolution was one of the most profound events in human history, leading to the rise of modern civilization. Now, in the first study of its kind, an international team of scientists has found that after agriculture arrived in Europe 8,500 years ago, people’s DNA underwent widespread changes, altering their height, digestion, immune system and skin color. Researchers had found indirect clues of some of these alterations by studying the genomes of living Europeans. But the new study, they said, makes it possible to see the changes as they occurred over thousands of years.
...The original hunter-gatherers, descendants of people who had come from Africa, had dark skin as recently as 9,000 years ago. Farmers arriving from Anatolia were lighter, and this trait spread through Europe. Later, a new gene variant emerged that lightened European skin even more. Why? Scientists have long thought that light skin helped capture more vitamin D in sunlight at high latitudes. But early hunter-gatherers managed well with dark skin. Dr. Reich suggests that they got enough vitamin D in the meat they caught. He hypothesizes that it was the shift to agriculture, which reduced the intake of vitamin D, that may have triggered a change in skin color. The new collection of ancient DNA also allowed Dr. Reich and his colleagues to track the puzzling evolution of height in Europe. After sorting through 169 height-related genes, they found that Anatolian farmers were relatively tall, and the Yamnaya even taller.
Neil Spencer in The Guardian:
Frank Sinatra’s favourite time of day was dawn, especially the ice-blue desert dawn of Las Vegas, the signal that he had slaked his gargantuan thirst for fine music, fast company, beautiful women and booze. His customary bedtime was 7am, at which point the perpetual party he led and underwrote would evaporate. Sinatra’s need for distraction and his terror of solitude are a central theme of Sinatra: The Chairman, James Kaplan’s meticulously researched biography, this second volume marking the singer’s centenary. Kaplan takes up his story in 1954, when Sinatra’s Oscar for From Here to Eternity began “the greatest comeback in showbusiness history”, taking him from over-the-hill crooner to worldwide icon. Kaplan draws from previous biographies and the memoirs of Sinatra’s lovers and fellow travellers, but the pithy narrative is his own, as are his persuasive critiques of the music.
...For a decade or more, Sinatra ruled US showbiz like a medieval monarch, “welcoming worship and demanding fealty”. Las Vegas, then little more than a clutch of casinos stretched along a two-lane blacktop, became his favourite playground, the home of the self-styled Rat Pack led by Sinatra, Dean Martin and Sammy Davis Jr. His work schedule was unrelenting, involving up to four live shows a night and three movies a year (mostly Hollywood schlock studded with a few fine performances), quite aside from his cheesy TV programmes and carefully crafted recording sessions. His personal life was just as intense. There wereendless flings with starlets and hookers, more serious affairs with Lauren Bacall and Marilyn Monroe and, later, an ill-advised, short-lived marriage to Mia Farrow, 30 years his junior. Yet Frank remained entangled with his second wife, Ava Gardner, the woman who “taught him how to sing a torch song”, as Nelson Riddle observed. “She taught him the hard way.”
Monday, November 23, 2015
It is the 100th anniversary of the publication of what many have called the most beautiful scientific theory of all time
by S. Abbas Raza
In November of 1915, Albert Einstein published what would come to be known as his theory of general relativity. Ten years ago, I wrote as simple an explanation as I could of some of the more salient aspects of that theory, here at 3 Quarks Daily. I am republishing that article below.
General Relativity, Very Plainly
[NOTE: Since I wrote and published this essay last night, I have received a private email from Sean Carroll, who is the author of an excellent book on general relativity, as well as a comment on this post from Daryl McCullough, both pointing out the same error I made: I had said, as do many physics textbooks, that special relativity applies only to unaccelerated inertial frames, while general relativity applies to accelerated frames as well. This is not really true, and I am very grateful to both of them for pointing this out. With his permission, I have added Sean's email to me as a comment to this post, and I have corrected the error by removing the offending sentences.]
In June of this year, to commemorate the 100th anniversary of the publication of Einstein's original paper on special relativity, I wrote a Monday Musing column in which I attempted to explain some of the more salient aspects of that theory. In a comment on that post, Andrew wrote: "I loved the explanation. I hope you don't wait until the anniversary of general relativity to write a short essay that will plainly explain that theory." Thanks, Andrew. The rest of you must now pay the price for Andrew's flattery: I will attempt a brief, intuitive explanation of some of the well-known results of general relativity today. Before I do that, however, a caveat: the mathematics of general relativity is very advanced and well beyond my own rather basic knowledge. Indeed, Einstein himself needed help from professional mathematicians in formulating some of it, and well after general relativity was published (in 1915) some of the greatest mathematicians of the twentieth century (such as Kurt Gödel) continued to work on its mathematics, clarifying and providing stronger foundations for it. What this means is, my explication here will essentially not be mathematical, which it was in the case of special relativity. Instead, I want to use some of the concepts I introduced in explaining special relativity, and extend some of the intuitions gathered there, just as Einstein himself did in coming up with the general theory. Though my aims are more modest this time, I strongly urge you to read and understand the column on special relativity before you read the rest of this column. The SR column can be found here.
Before anything else, I would like to just make clear some basics like what acceleration is: it is a change in velocity. What is velocity? Velocity is a vector, which means that it is a quantity that has a direction associated with it. The other thing (besides direction) that specifies a velocity is speed. I hope we all know what speed is. So, there are two ways that the velocity of an object can change: 1) change in the object's speed, and 2) change in the object's direction of motion. These are the two ways that an object can accelerate. (In math, deceleration is just negative acceleration.) This means that an object whose speed is increasing or decreasing is said to be accelerating, but so is an object traveling in a circle with constant speed, for example, because its direction (the other aspect of velocity) is changing at any given instant.
Get ready because I'm just going to give it to you straight: the fundamental insight of GR is that acceleration is indistinguishable from gravity. (Technically, this is only true locally, as physicists would say, but we won't get into that here.) Out of this amazing notion come various aspects of GR that most of us have probably heard about: that gravity bends light; that the stronger gravity is, the more time slows down; that space is curved. The rest of this essay will give somewhat simplified explanations of how this is so.
by Ali Minai
The terrible terrorist attacks by ISIS in Paris on November 13 have understandably generated a great surge of opinion and analysis – some of it insightful and some just opportunistic. It is precisely at times like these that the volume of immediate response threatens to obscure deeper issues, and for a problem as deep as the threat of jihadi extremism, this is truly dangerous. While people are still reeling from the actual attacks and decision-makers are reaching for the most obvious – and frequently bad – choices, it is critical that policy-makers move towards a more realistic understanding of the conflict they face, and not make things worse than they are. Of course, history suggests that this likely to be a vain hope - especially since the proper course is far from clear. This motivation behind this article is not to prescribe specific actions, but to provide a general perspective that may trigger further thinking.
Following the Paris attacks, President Hollande of France declared, "France is at war!" Similar pronouncements have been made by world leaders, analysts and pundits since 9/11. Some see the conflict with jihadi terrorists as a "clash of civilizations"; others as a "battle of ideas", pitting modern liberal democracy against a regressive ideology. Yet others have declared it to be a "battle for the soul of Islam." Those wedded to conventional geopolitics see it in terms of military engagements, covert operations and counterinsurgency. There is some element of truth to all these characterizations, but only in the sense that the five blind men of India had some part of the truth about the elephant. What has remained largely unacknowledged is the terrible truth that this is the first war of its kind – a brand new thing never before seen in history, and therefore one for which there is no prior wisdom. It is the first great conflict of the age of globalization, and its phenomenology reflects that of a complex, nonlinear, self-organizing networked world. To make an imperfect analogy, it is to ordinary warfare what quantum physics is to Newtonian physics. It is a war where things don't add up normally, where distant events can be strangely entangled, where common sense may be a liability, and where the very geometry of comprehension is distorted.
With mirrors the aging face became personal.
It hung before only on the heads of others,
but with realization that the still surface
of a pond returned the image of the seer,
when polished metals revealed a clear and troubling truth,
when a silver-backed square of glass
served up serial images of hard fact so precisely
denial was impossible,
the aging face became a self portrait
in intimate time, like a film frame
on a reel of a fresh spring field
which, between glimpses,
had been raked by a ruthless gardener
determined to turn new life into that
which can only be remembered