dilluns, 22 de novembre de 2010
dijous, 18 de novembre de 2010
A concatenation of puzzling results from an alphabet soup of satellites and experiments has led a growing number of astronomers and physicists to suspect that they are getting signals from a shadow universe of dark matter that makes up a quarter of creation but has eluded direct detection until now.
“Nobody really knows what’s going on,” said Gordon Kane, a theorist at the University of Michigan. Physicists caution that there could still be a relatively simple astronomical explanation for the recent observations.
But the nature of this dark matter is one of the burning issues of science. Identifying it would point the way to a deeper understanding of the laws of nature and the Einsteinian dream of a unified theory of physics.
The last few weeks have seen a blizzard of papers trying to explain the observations in terms of things like “minimal dark matter” or “exciting dark matter,” or “hidden valley” theory, and to suggest how to look for them in particle accelerators like the Large Hadron collider, set to begin operation again outside Geneva next summer.
“It could be deliriously exciting, an incredibly cool story,” said Nima Arkani-Hamed of the Institute for Advanced Study in Princeton, N.J., who has been churning out papers with his colleagues. “Anomalies in the sky tell you what to look for in the collider.”
On Thursday, a team of astrophysicists working on one of the experiments reported in the journal Nature that a cosmic ray detector onboard a balloon flying around the South Pole had recorded an excess number of high-energy electrons and their antimatter opposites, positrons, sailing through local space.
The particles, they conceded, could have been created by a previously undiscovered pulsar, the magnetized spinning remnant of a supernova explosion, blasting nearby space with electric and magnetic fields. But, they say, a better and more enticing explanation for the excess is that the particles are being spit out of the fireballs created by dark matter particles colliding and annihilating one another in space.
“We cannot disprove that the signal could come from an astrophysical object. We also cannot eliminate a dark matter annihilation explanation based upon current data,” said John P. Wefel of Louisiana State University, the leader of the team, adding, “Whichever way it goes, for us it is exciting.”
The results came on the heels of a report earlier this fall from Pamela, a satellite built by Italian, German, Russian and Swedish scientists to study cosmic rays. Pamela scientists reported in talks and a paper posted on the Internet that the satellite had recorded an excess of high-energy positrons. This, they said, “may constitute the first indirect evidence of dark matter particle annihilations,” or a nearby pulsar.
Antimatter is rare in the universe, and so looking for it is a good way of hunting for exotic phenomena like dark matter.
Another indication that something funny is happening on the dark side of the universe is evident in maps of the cosmic background radiation left over from the Big Bang. Those maps, produced most recently this year by the Wilkinson Microwave Anisotropy Probe satellite, show a haze of what seem to be charged particles hovering around the Milky Way galaxy, according to an analysis by Douglas Finkbeiner of the Harvard-Smithsonian Center for Astrophysics.
Adding to the mix and mystery, the European Space Agency’s Integral satellite detected gamma rays emanating from the center of the Milky Way, suggesting the presence of positrons there, but with much lower energies than Pamela and Dr. Wefel’s experiments have seen.
What all this adds up to, or indeed whether it all adds up to anything at all, depends on which observations you trust and your theoretical presumptions about particle physics and the nature of dark matter. Moreover, efforts to calculate the background level of high-energy particles in the galaxy are beset with messy uncertainties. “The dark matter signal is easy to calculate,” Dr. Kane said. “The background is much harder.”
Dark matter has teased and obsessed astronomers since the 1930s, when the Caltech astronomer Fritz Zwicky deduced that some invisible “missing mass” was required to supply the gravitational glue to hold clusters of galaxies together. The idea became respectable in the 1970s when Vera C. Rubin of the Carnegie Institution of Washington and her collaborators found from studying the motions of stars that most galaxies seemed to be surrounded by halos of dark matter.
The stakes for dark matter go beyond cosmology. The most favored candidates for its identity come from a theory called supersymmetry, which unifies three of the four known forces of nature mathematically and posits the existence of a realm of as-yet-undiscovered particles. They would be so-called wimps — weakly interacting massive particles — which feel gravity and little else, and could drift through the Earth like wind through a screen door. Such particles left over from the Big Bang could form a shadow universe clumping together into dark clouds that then attract ordinary matter.
The discovery of a supersymmetric particle would also be a boost for string theory, the controversial “theory of everything,” and would explicate the nature of a quarter of the universe. But until now, the dark matter particles have mostly eluded direct detection in the laboratory, the exception being a controversial underground experiment called Dama/Libra, for Dark Matter/Large Sodium Iodide Bulk for Rare Processes, under the Italian Alps, where scientists claimed in April to have seen a seasonal effect of a “dark matter wind” as the Earth goes around its orbit.
The sky could be a different story. Dark matter particles floating in the halos around galaxies would occasionally collide and annihilate one another in tiny fireballs of radiation and lighter particles, theorists say.
Dr. Wefel and his colleagues have been chasing sparks in the sky since 2000, when they flew an instrument known as ATIC, for Advanced Thin Ionization Calorimeter, around Antarctica on a balloon at an altitude of 23 miles, looking for high-energy particles known as cosmic rays raining from space.
In all they have made three flights, requiring them to spend the winter at the National Science Foundation’s McMurdo Station, which Dr. Wefel described as very pleasant. “It’s not bad until a storm moves in. You put your hand out till you can’t see it. Then you go out and start shoveling snow,” he explained.
The Nature paper includes data from the first two balloon flights. It shows a bump, over theoretical calculations of cosmic ray intensities, at energies of 500 billion to 800 billion electron volts, a measure of both energy and mass in physics. One way to explain that energy bump would be by the disintegration or annihilation of a very massive dark particle. A proton by comparison is about one billion electron volts.
Dr. Wefel noted, however, that according to most models, a pulsar could generate particles with even more energy, up to trillions of volts, whereas the bump in the ATIC data seems to fall off at around 800 billion electron volts. The ATIC results, he said, dovetail nicely with those from Pamela, which recorded a rising number of positrons relative to electrons, but only up to energies of about 200 billion electron volts.
Reached in China, where he was attending a workshop, Neal Weiner of New York University, who is working with Dr. Arkani-Hamed on dark matter models, said he was plotting ATIC data gleaned from the Web and Pamela data on the same graph to see how they fit, which was apparently very well.
But Piergiorgio Picozza, a professor at the University of Rome and the Pamela spokesman, said in an e-mail message that it was too soon to say the experiments agreed. That will depend on more data now being analyzed to learn whether Pamela continues to see more positrons as the energy rises.
Moreover, as Dr. Kane pointed out, Pamela carries a magnet that allows it to distinguish electrons from positrons — being oppositely charged, they bend in opposite directions going through the magnetic field. But the ATIC instrument did not include a magnet and so cannot be sure that it was seeing any positrons at all: no antimatter, no exotic dark matter, at least at those high energies.
But if he is right, Dr. Wefel said that the ATIC data favored something even more exotic than supersymmetry, namely a particle that is lost in the fifth dimension. String theory predicts that there are at least six dimensions beyond our simple grasp, wrapped up so tightly we cannot see them or park in them. A particle in one of these dimensions would not appear to us directly.
You could think of it as a hamster running around on a wheel in its cage. We cannot see the hamster or the cage, but we can sort of feel the impact of the hamster running; according to Einsteinian relativity, its momentum in the extra dimension would register as mass in our own space-time.
Such particles are called Kaluza-Klein particles, after Theodor Kaluza and Oscar Klein, theorists who suggested such an extra-dimensional framework in the 1920s to unify Einstein’s general theory of relativity and electromagnetism.
Dr. Wefel’s particle would have a mass of around 620 billion electron volts. “That’s the one that seems to fit the best,” he said in an interview. The emergence of a sharp edge in the data, he said, “would be a smoking gun” for such a strange particle.
But Dr. Arkani-Hamed said that Kaluza-Klein particles would not annihilate one another at a fast enough rate to explain the strength of the ATIC signal, nor other anomalies like the microwave haze. He and his colleagues, including Dr. Weiner, Dr. Finkbeiner and Tracy Slatyer, also of Harvard, drawing on work by Matthew Strassler of Rutgers, have tried to connect all the dots with a new brand of dark matter, in which there are not only dark particles but also a “dark force” between them.
That theory was called “a delightful castle in the sky” by Dr. Kane, who said he was glad it kept Dr. Arkani-Hamed and his colleagues busy and diverted them from competing with him. Dr. Kane and his colleagues favor a 200 billion-electron-volt supersymmetric particle known as a wino as the dark matter culprit, in which case the Pamela bump would not extend to higher energies.
Dr. Wefel said he had not kept up with all the theorizing. “I’m just waiting for one of these modelers to say here is the data, here is the model,” he said. “Fit it out. I’m not sure I’ve seen it yet.”
Dr. Picozza said that it was the job of theorists to come up with models and that they were proliferating.
“At the end of the story only one will be accepted from the scientific community, but now it is too early,” he said in an e-mail message.
Sorting all this out will take time, but not forever.
Pamela is expected to come out with new results next year, and the first results from the Fermi Gamma-ray Space Telescope, launched last summer, should also be out soon. Not to mention the Large Hadron Collider, which will eventually smash together protons of seven trillion electron volts. It is supposed to be running next summer.
“With so many experiments, we will soon know so much more about all of this,” Dr. Weiner said. “In a year or two, we’ll either not be talking about this idea at all, or it will be all we’re talking about.”
Dennis Overbye, The New York Times (2008). A whisper, perhaps, from the Universe's dark side.
dimarts, 16 de novembre de 2010
Singer James Blunt has told the BBC how he refused an order to attack Russian troops when he was a British soldier in Kosovo.Blunt said he was willing to risk a court martial by rejecting the order from a US General.
But he was backed by British Gen Sir Mike Jackson, who said: "I'm not going to have my soldiers be responsible for starting World War III."
Blunt was ordered to seize an airfield, but the Russians had got there first.
In an interview with BBC Radio 5 live, broadcast on Sunday, he said: "I was given the direct command to overpower the 200 or so Russians who were there.
"I was the lead officer with my troop of men behind us...
"The soldiers directly behind me were from the Parachute Regiment, so they're obviously game for the fight.
"The direct command [that] came in from Gen Wesley Clark was to overpower them. Various words were used that seemed unusual to us. Words such as 'destroy' came down the radio."
The confusion surrounding the taking of Pristina airfield in 1999 has been written about in political memoirs, and was widely reported at the time.
But this is the first time Blunt has given an account of his role in the incident.
Blunt, who was at the head of a column of 30,000 Nato troops with his unit, told Pienaar's Politics it was a "mad situation".
He said he had been "party to the conversation" between senior officers in which Gen Clark had ordered the attack.
"We had 200 Russians lined up pointing their weapons at us aggressively, which was... and you know we'd been told to reach the airfield and take a hold of it.
"And if we had a foothold there then it would make life much easier for the Nato forces in Pristina. So there was a political reason to take hold of this.
"And the practical consequences of that political reason would be then aggression against the Russians."Asked if following the order would have risked starting World War III, Blunt, who was a 25-year-old cavalry officer at the time, replied: "Absolutely. And that's why we were querying our instruction from an American general.
"Fortunately, up on the radio came Gen Mike Jackson, whose exact words at the time were, 'I'm not going to have my soldiers be responsible for starting World War III', and told us why don't we sugar off down the road, you know, encircle the airfield instead.
"And after a couple of days the Russians there said: 'Hang on we have no food and no water. Can we share the airfield with you?'."
If Gen Jackson had not blocked the order from Gen Clark, who as Nato Supreme Commander Europe was his superior officer, Blunt said he would still have declined to follow it, even at the risk of a court martial.
He said: "There are things that you do along the way that you know are right, and those that you absolutely feel are wrong, that I think it's morally important to stand up against, and that sense of moral judgement is drilled into us as soldiers in the British army."
Blunt left the Army in 2002 to pursue a career in music, later scoring a worldwide hit with You're Beautiful.
dilluns, 15 de novembre de 2010
The ad popped up in my e-mail the way it always has: “1-800-Flowers: Mother’s Day Madness — 30 Tulips + FREE vase for just $39.99!”
I almost clicked on it, forgetting for a moment that those services would not be needed this year. My mother, Margaret Friedman, died last month at the age of 89, and so this is my first Mother’s Day without a mom.
As columnists, we appear before you twice a week on these pages as simple bylines, but, yes, even columnists have mothers. And in my case, much of the outlook that infuses my own writings was bred into me from my mom. So, for once in 13 years, I’d like to share a little bit about her.
My mom was gripped by dementia for much of the last decade, but she never lost the generous “Minnesota nice” demeanor that characterized her in her better days. As my childhood friend Brad Lehrman said to me at her funeral: “She put the mensch in dementia.”
My mom’s life spanned an incredible period. She was born in 1918, just at the close of World War I. She grew up in the Depression, enlisted in the Navy after Pearl Harbor, served her country in World War II, bought our first house with a G.I. loan and lived long enough to play bridge on the Internet with someone in Siberia.
For most of my childhood, my mom appeared to be a typical suburban housewife of her generation, although I knew she was anything but typical. She sewed many of my sisters’ clothes, including both of their wedding dresses, and boy’s suits for me. And on the side, she won several national bridge tournaments.
My mom left two indelible marks on me. The first was to never settle for the cards you’re dealt. My dad died suddenly when I was 19. My mom worked for a couple of years. But in 1975, I got a scholarship to go to graduate school in Britain and my mom surprised us all one day by announcing that she was going, too. I called it the “Jewish Mother Junior Year Abroad Program.”
Most of her friends were shocked that she wasn’t just going to play widow. Instead, she sold our house in little St. Louis Park, Minn., and moved to London. But what was most amazing to watch was how she used her world-class bridge skills to build new friendships, including with one couple who flew her to Paris for a bridge game. Yes, our little Margie off to Paris to play bridge. She even came to see me in Beirut once, during the civil war — at age 62.
The picture of her in Beirut makes me think back in amazement at what my mom might have done had she had the money to finish college and pursue her dreams — the way she encouraged me to pursue mine, even when they meant I’d be far away in some crazy place and our only communications would be through my byline. It’s so easy to overlook — your mom had dreams, too.
My mom’s other big influence on me you can read between the lines of virtually every column — and that is a sense of optimism. She was the most uncynical person in the world. I don’t recall her ever uttering a word of cynicism. She was not naïve. She had taken her knocks. But every time life knocked her down, she got up, dusted herself off and kept on marching forward, motivated by the saying that pessimists are usually right, optimists are usually wrong, but most great changes were made by optimists.
Six years ago, I was in Israel at a dinner with the editor of the Haaretz newspaper, which publishes my column in Hebrew. I asked the editor why the newspaper ran my column, and he joked: “Tom, you’re the only optimist we have.” An Israeli general, Uzi Dayan, was seated next to me and as we walked to the table, he said: “Tom, I know why you’re an optimist. It’s because you’re short and you can only see that part of the glass that’s half full.”
Well, the truth is, I am not that short. But my mom was. And she, indeed, could only see that part of the glass that was half full. Read me, read my mom.
Whenever I’ve had the honor of giving a college graduation speech, I always try to end it with this story about the legendary University of Alabama football coach, Bear Bryant. Late in his career, after his mother had died, South Central Bell Telephone Company asked Bear Bryant to do a TV commercial. As best I can piece together, the commercial was supposed to be very simple — just a little music and Coach Bryant saying in his tough voice: “Have you called your mama today?”
On the day of the filming, though, he decided to ad-lib something. He reportedly looked into the camera and said: “Have you called your mama today? I sure wish I could call mine.” That was how the commercial ran, and it got a huge response from audiences.
So on this Mother’s Day, if you take one thing away from this column, take this: Call your mother.
I sure wish I could call mine.
Thomas Friedman, The New York Times. Call your mother.
dijous, 11 de novembre de 2010
His first memorable experience in the army was a briefing on sex from a medical officer, which frankly shocked him. Without a trace of a smile the officer had said, “Don’t forget: a woman for children, a boy for pleasure, but for real ecstasy, a goat.” At the tail end of World War II, Colonel Cross was assigned to the 1st Battalion of the 1st Gurkha Rifles, based at Dharamsala, and thus commenced his life’s work as a leader of Gurkhas. From there it was on to Burma to fight and disarm Japanese soldiers; to Cochin-China (Vietnam) to fight the Viet Minh; and to Laos, where, as the last British defense attaché before the fall of the monarchy, Cross became the de facto eyes and ears of the U.S. embassy, tracking the Communist Pathet Lao (the British ambassador, he says with a sneer, “was a fellow-traveler”). Next he went to western Nepal to become a recruiting officer for the Gurkhas. Future years would find him parachuting into Borneo to fight a Communist insurgency, and training Americans in jungle warfare in the Malay Peninsula. “A certain BBC reporter, God rot his soul, accused me of teaching torture,” Cross recalls. All in all he has spent a total of ten years in the jungle, often carrying the equivalent of his own weight on his back, which he terms “a delightful way of life.” He speaks French and nine Asian languages.
Cross is a confirmed bachelor because of “hot blood and cold feet,” he explains. His library of battered books, medals, and kukri knives, each object charged by a memory, is decayed by heat and humidity, for he has no air-conditioning. He sleeps on a spartan bed in the next room.
Now, writing books on irregular warfare and Himalayan history that deserve to be read even though they aren’t, he is a minor and very eccentric offshoot of a British imperial species that reached perfection in the person of the former soldier and literary travel writer Patrick Leigh Fermor, whom I interviewed in Greece in 2002. Both are inveterate walkers: Fermor across Europe, Cross across Nepal.
I found the old Gurkhas a haunting presence, because they were sharpened, refined, exaggerated forms of the Marines and soldiers I had been befriending and describing in previous travels. There was something indisputably antique about these gentlemen warriors, who told me their life stories under a black-and-white photograph of Queen Elizabeth II. To call them Kiplingesque would be to cheapen them; they were practically out of the Iliad.
Of course, Colonel Cross is a throwback. His outlook and manner of expression can be brutal, almost perverse. He is living in a threatened backwater of the only country he can call his own. Still, there was a certain cruel logic in his pronouncements.
“It’s not about sugarcoated bullets and dispensing condoms in PXes,” he said. “You can’t fight properly until you know that you are going to die anyway. That’s extreme, but that’s the gold standard. You don’t join the army to wipe your enemy’s ass. You join to kill, or for you yourself to be killed, and above all to have a good sense of humor about it.”
Robert D. Kaplan, Atlantic Monthly. Colonel Cross of the Gurkhas.
dilluns, 8 de novembre de 2010
dissabte, 6 de novembre de 2010
se quiebra como un vaso,
y antes de que se rompa
y muera (porque las cosas mueren
también) llénalo de agua
y bebe, quiero decir que dejes
las palabras gastadas, bien lavadas,
en el fondo quebrado
de tu alma,
y que, si pueden, canten.
divendres, 5 de novembre de 2010
dimecres, 3 de novembre de 2010
dimarts, 2 de novembre de 2010
It has been described as one of the greatest battles of all time -- the fight between Henry V of England and the French army on October 25, 1415, at Agincourt in northern France. Henry, whose goal was to reclaim English territory seized by France in earlier centuries, had approximately 6,000 men. The French army, depending on which historical report you read, had anywhere from 30,000 to 60,000 soldiers, many of them knights in armor prepared to fight on foot and on horseback. The English army had neither armor nor horses, and they were exhausted by their two-month trek across France trying to reach what was then the English port of Calais.
But they did have what turned out to be a decisive advantage -- Henry V's leadership skills and his ability to innovate in ways that would turn significant disadvantages into game-winning advantages. In addition, before the battle started, he delivered one of the most famous motivational speeches in history -- at least as it is written in Shakespeare's Henry V. The speech has been played on Allied ships crossing the English Channel to Normandy during World War II; in locker rooms by football coaches losing at half time, and on the Internet for U.S. soldiers about to leave for duty in Iraq.
Here is how Henry won: He stopped his army on a field that was flanked on either side by woodlands, thus forcing the French army to move forward through a narrow funnel and neutralizing their superior numbers. He took full advantage of a rainfall that had muddied the battlefield and that would prove disastrous for the armored French soldiers -- when they slipped backwards wearing their 60-pound armor, they couldn't hoist themselves back up; when they fell forward, they drowned in the mud.
In addition, rather than rely on the more traditional, easy-to-use crossbow, Henry chose the long bow, which could fire arrows more quickly and at greater range. The resulting hail of arrows killed French soldiers behind the front line, taking away urgently needed reinforcements. Henry armed his men with pikes a foot longer than those used by the French, allowing English soldiers in hand-to-hand combat to deliver the first, and usually lethal, blow. And, in what has been described as a last minute innovation, Henry planted sharp stakes in the ground just at the point of the battle's engagement. The French army's horses, rushing forward, were impaled on the stakes and fell to the ground, crushing soldiers around them and blocking the path forward for others.
When the fighting stopped after several hours, the French had lost about 6,000 men, and the English about 450.
Some version of this battle has been told in history books, in Shakespeare's play and, two weeks ago, by Carol and Ken Adelman, founders of Movers & Shakespeares, which uses the world's greatest playwright to teach modern management skills to executives. The Adelmans were at Wharton as part of a Wharton executive education program called "The Leadership Journey."
Carol Adelman is director of the Hudson Institute's Center for Global Prosperity where, among other things, she developed the annual Index of Global Philanthropy and Remittances. Ken Adelman is a former U.S. Ambassador to the United Nations and director of the U.S. Arms Control & Disarmament Agency during the Reagan administration.
The two started Movers & Shakespeares eight years ago because, as Carol noted during the course, William Shakespeare offers his audience exceptionally astute insights into human nature and has a genius for telling stories, which, she suggested, "is the best way to learn." The downside to the bard, she added, is that the language can be tedious and hard to understand -- something that comes as no surprise to high school students everywhere.
The Adelmans' approach is to delve into the language and extract leadership lessons from Shakespeare's plays. In this particular session, the focus was on Henry V, brought to life by a series of scenes from the 1989 movie starring Kenneth Branagh as Henry and Emma Thompson as the French princess Katharine. The class discussion centered on the battle scene, the motivation speech, Henry's wooing of Katharine, the punishment meted out to a soldier caught stealing, and the conference between Henry V and the Archbishop of Canterbury before Henry sets sail for France.
From the description of the battle at Agincourt, it's clear that Henry V displayed remarkable leadership capabilities, said Ken Adelman. He led by example, situating himself in the middle of the fighting whereas the French king, Charles VI, stayed in Paris, leaving the army under the leadership of a group of nobles. "Henry was willing to innovate, recognizing, for example, the superiority of the long bow and making sure his men were well-trained in how to use it," Adelman noted. Before Agincourt, the English army was 80% foot soldiers and 20% archers. After Agincourt, it was 20% foot soldiers and 80% archers.
Yet perhaps the English army's biggest asset was the speech Henry made to his men just before going into battle, including the famous sentence, "All things are ready if our minds be so." (The words are Shakespeare's; the actual text of the speech does not exist.) Even before speaking, Henry walks among his troops listening to what they are saying and feeling, and then positions himself in their midst to deliver his address. By contrast, the French leaders (in the Branagh movie) are shown at the head of their army, uttering confident phrases unable to be heard by any of their soldiers.
Here are excerpts from Henry's speech in the play:
"That he which hath no stomach to this fight,
Let him depart; his passport shall be made
And crowns for convoy put into his purse:
We would not die in that man's company
That fears his fellowship to die with us...
Old men forget: yet all shall be forgot,
But he'll remember with advantages
What feats he did that day: then shall our names
Familiar in his mouth as household words
Harry the King, Bedford and Exeter,
Warwick and Talbot, Salisbury and Gloucester,
Be in their flowing cups freshly remember'd.
This story shall the good man teach his son
And Crispin Crispian shall ne'er go by,
From this day to the ending of the world,
But we in it shall be remember'd;
We few, we happy few, we band of brothers;
For he today that shed his blood with me
Shall be my brother."