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  • richardmitnick 10:22 am on November 25, 2014 Permalink | Reply
    Tags: , New York Times   

    From NYT: “On the Trail of an Ancient Mystery” 

    New York Times

    The New York Times

    NOV. 24, 2014
    JOHN MARKOFF

    Solving the Riddles of an Early Astronomical Calculator

    A riddle for the ages may be a small step closer to a solution: Who made the famed Antikythera Mechanism, the astronomical calculator that was raised from an ancient shipwreck near Crete in 1901?

    The complex clocklike assembly of bronze gears and display dials predates other known examples of similar technology by more than 1,000 years. It accurately predicted lunar and solar eclipses, as well as solar, lunar and planetary positions.

    m
    Part of the Antikythera Mechanism, above, an astronomical calculator raised from a shipwreck in 1901. Credit Thanassis Stavrakis/Associated Press

    For good measure, the mechanism also tracked the dates of the Olympic Games. Although it was not programmable in the modern sense, some have called it the first analog computer.

    Archaeologists and historians have long debated where the device was built, and by whom. Given its sophistication, some experts believe it must have been influenced, at least, by one of a small pantheon of legendary Greek scientists — perhaps Archimedes, Hipparchus or Posidonius.

    Its purpose has been debated, too. It has been described as, among other things, an eclipse predictor, an astrological forecasting system and an astronomical teaching device.

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    Astrological clock at Venice
    20 July 2011
    Zachariel

    Now a new analysis of the dial used to predict eclipses, which is set on the back of the mechanism, provides yet another clue to one of history’s most intriguing puzzles. Christián C. Carman, a science historian at the National University of Quilmes in Argentina, and James Evans, a physicist at the University of Puget Sound in Washington, suggest that the calendar of the mysterious device began in 205 B.C., just seven years after Archimedes died.

    The mechanism was most likely housed in a wooden box and operated by a hand crank. The device itself bears inscriptions on the front and back. In the 1970s, the engravings were estimated to date from 87 B.C. But more recently, scientists examining the forms of the Greek letters in the inscriptions dated the mechanism to 150 to 100 B.C.

    Writing this month in the journal Archive for History of Exact Sciences, Dr. Carman and Dr. Evans took a different tack. Starting with the ways the device’s eclipse patterns fit Babylonian eclipse records, the two scientists used a process of elimination to reach a conclusion that the “epoch date,” or starting point, of the Antikythera Mechanism’s calendar was 50 years to a century earlier than had been generally believed.

    k
    Kryptos, a sculpture at C.I.A. headquarters in Langley, Va., in 2010.

    The last of four messages embedded in Kryptos has baffled code breakers since the work went up in 1990. The sculptor, Jim Sanborn, gave a six-letter clue (“Berlin”) in 2010, but it did not lead to a solution. So he has offered another hint, this one five letters (“Clock”). “I figured maybe I should be a little more specific,” he said.

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    Sculptor Offers Another Clue in 24-Year-Old Mystery at C.I.A. NOV. 20, 2014

    The artist who created the enigmatic Kryptos, a puzzle-in-a-sculpture that has driven code breakers to distraction since it was installed 24 years ago in a courtyard at C.I.A. headquarters in Langley, Va., has decided that it is time for a new clue.

    By 1999, nine years after it went up, Kryptos fans had deciphered three of the sculpture’s four messages — 865 letters punched through elegantly curved copper sheets that make up the most striking part of the work. (In fact, cryptographers at the National Security Agency cracked those messages in 1993, but kept the triumph to themselves.) The fourth and final passage, a mere 97 characters long, has thwarted thousands of followers ever since.

    Jim Sanborn, the sculptor, having grown impatient with the progress of the fans and their incessant prodding for clues — and the misguided insistence by some that they had actually solved the puzzle — provided a six-letter clue to the puzzle in 2010. The 64th through 69th characters of the final panel, when deciphered, spelled out the word BERLIN.

    The finding supports the idea, scientists said, that the mechanism’s eclipse prediction strategy was not based on Greek trigonometry, which did not exist at the time, but on Babylonian arithmetical methods borrowed by the Greeks.

    Since then, the fans, many of whom keep up a lively online conversation, have come up empty-handed. And so Mr. Sanborn has decided to open the door a bit more with five additional letters, those in the 70th through 74th position.

    They spell “clock.”

    This means that the letters from positions 64 to 74 spell out two words: “Berlin clock.”

    As it happens, there is a famous public timepiece known as the “Berlin clock,” a puzzle in itself that tells time through application of set theory. Its 24 lights count off the hours and minutes in rows and boxes, with hours in the top two rows and minutes in the two below.

    When asked whether his new clue was a reference to this Berlin clock, Mr. Sanborn, sounding pleased, said, “There are several really interesting clocks in Berlin.”

    He added, “You’d better delve into that particular clock,” a favorite of conspiracy theorists because of the mysterious death in 1991 of its designer, Dieter Binninger. With all the intriguing timekeepers in the city, including the “Clock of Flowing Time,” Mr. Sanborn said, “There’s a lot of fodder there.”

    Divulging the clue “Berlin,” he said, led to “a tsunami” of entries that went off in every direction, including many “frivolous or debasing or hostile entries,” as well as messages from Nazi enthusiasts.

    The crush of people claiming to have solved the final puzzle, reached through a website Mr. Sanborn set up in 2010, had grown to be such a distraction that he set up a barrier to entry.

    Two years ago, he instituted a $50 fee (via Western Union) for anyone wanting to test a possible solution; the fee guaranteed “an exchange of no more than two back-and-forth-emails,” and no additional clues. If Mr. Sanborn did not wish to respond to the entry, he said, he would return the money.

    “It really worked very well,” he said. Although he has not made much money, Mr. Sanborn said that was not the idea: “It’s made it manageable.”

    But still, no solution. So Mr. Sanborn, now 69, said, “I figured maybe I should be a little more specific.”

    He was designing the project, he further explained, when the Berlin Wall fell, and “there’s no doubt I was influenced by all that going on simultaneously.” With the 25th anniversary of the fall of the wall, he said, he thought it was worth returning to the topic.

    The news will undoubtedly scramble the thousands of people around the world who have tried to decrypt Mr. Sanborn’s brainchild, especially the members of a Yahoo group devoted to the sculpture. They meet every now and then in the real world with a dinner in the Washington area; Mr. Sanborn has attended, as have N.S.A. employees.

    That community keeps up a steady stream of chatter about possible solutions, and is roughly divided between those who are called the “O.S.C.s,” for Old School Cryptographers, and “Brownies,” for devotees of the thriller author Dan Brown, who has mentioned Kryptos in his work.

    Edward M. Scheidt, a retired chairman of the Central Intelligence Agency’s cryptographic center, worked with Mr. Sanborn to devise the cryptographic schemes he incorporated into the artwork. Mr. Scheidt, reached in Herndon, Va., at the encryption company TecSec, which he co-founded, said he would not have expected to find people still banging their heads against Kryptos so many years later.

    “No, not really,” Mr. Scheidt said with a chuckle. “But a technique that I used obviously worked.”

    t
    A digital image of the surface inscriptions on the Antikythera Mechanism.

    Over the years scientists have speculated that the mechanism might have been somehow linked to Archimedes, one of history’s most famous mathematicians and inventors. In 2008, a group of researchers reported that language inscribed on the device suggested it had been manufactured in Corinth or in Syracuse, where Archimedes lived.

    But Archimedes was killed by a Roman soldier in 212 B.C., while the commercial grain ship carrying the mechanism is believed to have sunk sometime between 85 and 60 B.C. The new finding suggests the device may have been old at the time of the shipwreck, but the connection to Archimedes now seems even less likely.

    An inscription on a small dial used to date the Olympic Games refers to an athletic competition that was held in Rhodes, according to research by Paul Iversen, a Greek scholar at Case Western Reserve University.

    “If we were all taking bets about where it was made, I think I would bet what most people would bet, in Rhodes,” said Alexander Jones, a specialist in the history of ancient mathematical sciences at New York University.

    Dr. Evans said he remained cautious about attempting to identify the maker at all.

    “We know so little about ancient Greek astronomy,” he said. “Only small fragments of work have survived. It’s probably safer not to try to hang it on any one particular famous person.”

    Since new information began to emerge about the Antikythera Mechanism in 2006, it has been the source of several books, replicas and computer simulations, even a Lego model. A growing research community of Greek scholars, archaeologists, astronomers and historians is chasing its secrets.

    Last fall, an expedition led by Woods Hole and Greek government scientists began the first systematic, scientific investigation of the site of the shipwreck where the mechanism was found. The dive was shortened to just five days because of bad weather, but the scientists plan to return next spring.

    See the full article here.

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  • richardmitnick 5:27 pm on November 23, 2014 Permalink | Reply
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    From NYT: “Climate Change Threatens to Strip the Identity of Glacier National Park” 

    New York Times

    The New York Times

    NOV. 22, 2014
    MICHAEL WINES

    GLACIER NATIONAL PARK, Mont. — What will they call this place once the glaciers are gone?

    g

    A century ago, this sweep of mountains on the Canadian border boasted some 150 ice sheets, many of them scores of feet thick, plastered across summits and tucked into rocky fissures high above parabolic valleys. Today, perhaps 25 survive.

    In 30 years, there may be none.

    A warming climate is melting Glacier’s glaciers, an icy retreat that promises to change not just tourists’ vistas, but also the mountains and everything around them.

    Streams fed by snowmelt are reaching peak spring flows weeks earlier than in the past, and low summer flows weeks before they used to. Some farmers who depend on irrigation in the parched days of late summer are no longer sure that enough water will be there. Bull trout, once pan-fried over anglers’ campfires, are now caught and released to protect a population that is shrinking as water temperatures rise.

    Many of the mom-and-pop ski areas that once peppered these mountains have closed. Increasingly, the season is not long enough, nor the snows heavy enough, to justify staying open.

    What is happening here is occurring, to greater or lesser extents, in mountains across the North American West. In the Colorado Rockies, the median date of snowmelt shifted two to three weeks earlier from 1978 to 2007. In Washington, the Cascades lost nearly a quarter of their snowpack from 1930 to 2007. Every year, British Columbia’s glaciers shed the equivalent of 10 percent of the Mississippi River’s flow because of melting.

    The retreat is not entirely due to man-made global warming, though scientists say that plays a major role. While the rate of melting has alternately sped up and slowed in lock step with decades-long climate cycles, it has risen steeply since about 1980.

    And while glaciers came and went millenniums ago, the changes this time are unfolding over a Rocky Mountain landscape of big cities, sprawling farms and growing industry. All depend on steady supplies of water, and in the American West, at least 80 percent of it comes from the mountains.

    “Glaciers are essentially a reservoir of water held back for decades, and they’re releasing that water in August when it’s hot, and streams otherwise might have low flows or no flows,” Daniel B. Fagre, a United States Geological Survey research ecologist, said in an interview. “As glaciers disappear, there will be a reduction in the water at the same time that demand is going up. I think we’re on the cusp of bigger changes.”

    But shrinking glaciers are only the visible symptom of much broader and more serious changes. “We’re a snow-driven ecosystem, and glaciers are just a part of that,” Dr. Fagre said. “The way the snow goes is the way our ecosystem goes.”

    Lately, the snows are not going well.

    Mountain snowpacks are shrinking. In recent decades, rising winter temperatures have increasingly changed snows to rain. Rising spring temperatures are melting the remaining snow faster.

    “Imagine turning on your faucet in your sink and all your water runs out in an hour’s time,” Thomas Painter, a research scientist and snow hydrologic expert at NASA’s Jet Propulsion Laboratory, said in an interview. “Loss of snowpack earlier in the year compresses runoff into a shorter period of time.”

    Glaciers and year-round snowfields — accumulations of snow in colder locations, like shadowed mountainsides, that never fully melt — pick up the slack in summer. But they, too, are vanishing: In Glacier National Park, the number of days above 90 degrees has tripled since early last century, and the summertime span in which such hot days occur has almost doubled, to include all of July and most of August.

    Winters are warmer, too: A century ago, the last brutally cold day typically occurred around March 5. By last decade, it had receded to Feb. 15.

    Dr. Fagre, the park’s resident expert on snowpacks, glaciers and climate change, can see the changes firsthand. Grinnell Glacier, one of the park’s most studied ice sheets, feeds a frigid lake on the flanks of Mount Gould, more than 6,000 feet above sea level. “At the beginning, we had a 25-foot-high wall of ice that we were actually concerned about from a safety standpoint,” he said. “And now the entire glacier simply slopes into the water, with no wall of ice whatsoever.

    “All of that has melted just within the last 10 years.”

    At Clements Mountain, with a summit some 8,800 feet above sea level, what used to be a glacier is now a shrinking snowfield surrounded by 30- and 40-foot heaps of moraine, stones piled up by the ice as it pushed its way forward. One recent fall day, freshets of melted snow tumbled over rock ledges and down hills, past stands of Rocky Mountain firs.

    But that will change.

    “This snowfield will vanish,” Dr. Fagre said. “When that happens, this whole area will dry up a lot. A lot of these alpine gardens, so to speak, are sustained entirely by waterfalls and streams like this. And once this goes, then some of those plants will disappear.”

    For wildlife, Dr. Fagre said, the implications are almost too great to count. Frigid alpine streams may dry up, and cold-water fish and insects may grow scarce. Snowfall may decline, and fewer avalanches may open up clearings for wildlife or push felled trees into streams, creating trout habitats. Tree lines may creep up mountains, erasing open meadows that enable mountain goats to keep watch against mountain lions. A hummingbird that depends on glacial lilies for nectar may arrive in spring to find that the lilies have already blossomed.

    Trekking across what is left of the Clements snowfield, Dr. Fagre unexpectedly encountered a long-clawed paw print: from one of perhaps 300 wolverines said to remain in the lower 48 states. These solitary, ferocious animals have come back after trappers nearly eliminated them decades ago, but conservationists and federal wildlife experts are sharply at odds over whether rising temperatures imperil them.

    “Wolverines need deep snows to build their winter dens,” Dr. Fagre said. “I’m not sure what’s going to happen to them.”

    For people, the future is somewhat clearer.

    Rising temperatures and early snowmelt make for warmer, drier summers as rivers shrink and soils dry out. That is already driving a steady increase in wildfires, including in the park, and disease and pest infestations in forests.

    But in the long term, the ramifications are more ominous than a mere rise in fires or dying trees.

    Moisture loss from early snowmelt is worsening a record hydrological drought on the Colorado River, which supplies water to about 40 million people from the Rockies to California and Mexico; by 2050, scientists estimate, the Colorado’s flow could drop by 10 percent to 30 percent.

    In the usually arid West, where reservoirs are vital, earlier and bigger snowmelt will disrupt the task of balancing water demand and supply. Experts anticipate an increase in disputes over water rights as a growing population competes for a shrinking resource. And farming, a major industry across much of the Rockies, will become even more of a gamble than fickle weather makes it.

    Indeed, complications have already surfaced. Dennis Iverson runs a 140-head cow-and-calf operation on several thousand acres about 25 miles northeast of Missoula, Mont. Five hundred acres are hayfield, irrigated with water from the Blackfoot River about one and a half miles away.

    Twenty years ago, the water flowed through an open ditch, and from the time the irrigation pumps were started on May 20, “we were able to irrigate the whole ranch,” he said. “There was always enough water, even to do some irrigating in July and August.”

    Now, Mr. Iverson starts the pumps on May 10, because a hotter spring has already dried out his pasture. The open irrigation ditch has been converted into an 8,000-foot underground pipe to prevent evaporation. “If we hadn’t done that, we wouldn’t even be getting water to the ranch,” he said. “There’s that much less water in the stream than there was 20 years ago.”

    See the full article, with slide show an d park map, here.

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  • richardmitnick 7:04 am on November 18, 2014 Permalink | Reply
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    From NYT: “So Far Away, Yet So Near to Us” 

    New York Times

    The New York Times

    NOV. 17, 2014
    JOHN NOBLE WILFORD

    Philae is talking to us,” announced the manager in charge of the little piece of machinery that had just achieved the first landing on a comet, a frozen remnant from the formation of the solar system. “We are on the comet.”

    ph
    Philae

    ESA Rosetta spacecraft
    ESA/Rosetta with Philae

    Note the familiar, almost casual tone. It was as if the first thing the probe did on arrival was to call home, like a traveler with an ever-ready iPhone. The flight had taken forever, and that was some landing — bouncing around and finally winding up almost halfway across the surface. The European Space Agency’s probe was “talking” about its comet landing on Wednesday after a 10-year, four-billion-mile journey.

    The “we” echoes a famous human-machine flight relationship, Lindbergh’s solo crossing of the Atlantic in “The Spirit of St. Louis.” Here, the distant robotic messenger and the human receiver — the “we” — are also collaborators in reaching a new milestone in flight. Philae had made it to the surface on Comet 67P/Churyumov-Gerasimenko, an icy, rocky place only two and a half miles wide and 317 million miles from Earth.

    67
    Comet 67P/Churyumov-Gerasimenko

    Now, as even the most stalwart human explorers remain confined to lower Earth orbit for the foreseeable future, the search for discovery in the outer reaches of the solar system is left to robotic probes. They are conceived by humans to go where humans themselves cannot go. But that does not preclude the development of a strong human-machine bond over years of building, testing and flying a mission.

    Minders of these machines may spend half a career on an idea they will then cast into the heavens, and wait through what may seem like another half-career for it to reach its destination and send back results. The human-machine bond can be tight. Even no-nonsense scientists and engineers find themselves personalizing such a consuming life experience as well as a trusted machine.

    Sometimes, they too are guilty of the transgression they warn laypeople against: anthropomorphism, the attribution of human form and behavior to nonhuman or even inanimate forms. A machine is talking to us. It was shaken up by the three-bounce landing, at last coming to rest near a sheltering rock face (not a choice place, as it prevents sunlight from reaching the lander’s solar panels, which were counted on to charge its batteries). Poor Philae may not have long to live.

    What could be more natural than treating the probe in almost human terms when you have spent at least a decade, waking and dreaming, with machinery on which such care is bestowed that it penetrates to your very core? Your dog may or may not be your best friend, and who knows about the cat? But Philae talks to you.

    Finding something to relate to is a never-ending struggle for humans, as spacecraft and telescopes draw attention to unworldly realms. Thomas A. Mutch of Brown University was the principal geologist for the Viking missions in 1976 to search for possible life on Mars. When the first Viking landed on Mars and started transmitting pictures of the immediate surface, Dr. Mutch (known to all as Tim) focused his excitement on a single rock near of the craft’s footpads. The rock was red, as was nearly everything around on the russet plain, and so the geologist had something he could relate to. He would deal with the big picture in time.

    NASA Viking 1
    NASA/Viking 1

    Reporters don’t always resist the temptation to make homey comparisons of faraway encounters. In 1983, the Pioneer 10 spacecraft crossed the orbit of Pluto. Though it has since been stripped of full planetary standing, Pluto still represents a frontier into a greater unknown. Pioneer had flown by and photographed Jupiter and Saturn and was still going. Writing about this, I kept hearing the rhythm of the Little Engine That Could.

    NASA Pioneer 10
    NASA/Pioneer 10

    So I sought to put the same bug in the reader’s ear: Like the little engine that could, this was the little spacecraft that would probably push on to the frontier of interstellar space and still be living to tell the tale.

    Antoine de Saint-Exupéry, a French author, might have been able to understand our problem with perspective, in a universe so vast in which we are so small. Aside from his books on early aviation, he wrote about the Little Prince, who lived on a small asteroid where he cared for a single rose. The book was written for children, but with grown-ups very much in mind.

    A fox the little prince meets has some of the wisest lines. “One sees clearly only with the heart,” he says. “What is essential is invisible to the eye.”

    See the full article here.

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  • richardmitnick 6:16 am on November 17, 2014 Permalink | Reply
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    From NYT: “Is Quantum Entanglement Real?” 

    New York Times

    The New York Times

    NOV. 14, 2014
    SundayReview
    DAVID KAISER

    FIFTY years ago this month, the Irish physicist John Stewart Bell submitted a short, quirky article to a fly-by-night journal titled Physics, Physique, Fizika. He had been too shy to ask his American hosts, whom he was visiting during a sabbatical, to cover the steep page charges at a mainstream journal, the Physical Review. Though the journal he selected folded a few years later, his paper became a blockbuster. Today it is among the most frequently cited physics articles of all time.

    man

    Bell’s paper made important claims about quantum entanglement, one of those captivating features of quantum theory that depart strongly from our common sense. Entanglement concerns the behavior of tiny particles, such as electrons, that have interacted in the past and then moved apart. Tickle one particle here, by measuring one of its properties — its position, momentum or “spin” — and its partner should dance, instantaneously, no matter how far away the second particle has traveled.

    The key word is “instantaneously.” The entangled particles could be separated across the galaxy, and somehow, according to quantum theory, measurements on one particle should affect the behavior of the far-off twin faster than light could have traveled between them.

    Entanglement insults our intuitions about how the world could possibly work. Albert Einstein sneered that if the equations of quantum theory predicted such nonsense, so much the worse for quantum theory. “Spooky actions at a distance,” he huffed to a colleague in 1948.

    In his article, Bell demonstrated that quantum theory requires entanglement; the strange connectedness is an inescapable feature of the equations. But Bell’s proof didn’t show that nature behaved that way, only that physicists’ equations did. The question remained: Does quantum entanglement occur in the world?

    Starting in the early 1970s, a few intrepid physicists — in the face of critics who felt such “philosophical” research was fit only for crackpots — found that the answer appeared to be yes.

    John F. Clauser, then a young postdoctoral researcher at the Lawrence Berkeley National Laboratory, was the first. Using duct tape and spare parts, he fashioned a contraption to measure quantum entanglement. Together with a graduate student named Stuart Freedman, he fired thousands of pairs of little particles of light known as photons in opposite directions, from the middle of the device, toward each of its two ends. At each end was a detector that measured a property of the photon known as polarization.

    As Bell had shown, quantum theory predicted certain strange correlations between the measurements of polarization as you changed the angle between the detectors — correlations that could not be explained if the two photons behaved independently of each other. Dr. Clauser and Mr. Freedman found precisely these correlations.

    Other successful experiments followed. One, led by the French physicist Alain Aspect, tested the instantaneousness of entanglement. Another, led by the Austrian physicist Anton Zeilinger, considered entanglement among three or more particles.

    Even with these great successes, work remains to be done. Every experimental test of entanglement has been subject to one or more loopholes, which hold out the possibility, however slim, that some alternative theory, distinct from quantum theory and more in line with Einstein’s intuitions, may still be salvageable. For example, one potential loophole — addressed by Dr. Aspect’s experiment — was that the measurement device itself was somehow transmitting information about one particle to the other particle, which would explain the coordination between them.

    The most stubborn remaining loophole is known as “setting independence.” Dr. Zeilinger and I, working with several colleagues — including the physicists Alan H. Guth, Andrew S. Friedman and Jason Gallicchio — aim to close this loophole, a project that several of us described in an article in Physical Review Letters.

    HERE’S the problem. In any test of entanglement, the researcher must select the settings on each of the detectors of the experimental apparatus (choosing to measure, for example, a particle’s spin along one direction or another). The setting-independence loophole suggests that, though the researcher appears to be free to select any setting for the detectors, it is possible that he is not completely free: Some unnoticed causal mechanism in the past may have fixed the detectors’ settings in advance, or nudged the likelihood that one setting would be chosen over another.

    Bizarre as it may sound, even a minuscule amount of such coordination of the detectors’ settings would enable certain alternative theories to mimic the famous predictions from quantum theory. In such a case, entanglement would be merely a chimera.

    How to close this loophole? Well, obviously, we aren’t going to try to prove that humans have free will. But we can try something else. In our proposed experiment, the detector setting that is selected (say, measuring a particle’s spin along this direction rather than that one) would be determined not by us — but by an observed property of some of the oldest light in the universe (say, whether light from distant quasars arrives at Earth at an even- or odd-numbered microsecond). These sources of light are so far away from us and from one another that they would not have been able to receive a single light signal from one another, or from the position of the Earth, before the moment, billions of years ago, when they emitted the light that we detect here on Earth today.

    That is, we would guarantee that any strange “nudging” or conspiracy among the detector settings — if it does exist — would have to have occurred all the way back at the Hot Big Bang itself, nearly 14 billion years ago.

    If, as we expect, the usual predictions from quantum theory are borne out in this experiment, we will have constrained various alternative theories as much as physically possible in our universe. If not, that would point toward a profoundly new physics.

    Either way, the experiment promises to be exciting — a fitting way, we hope, to mark Bell’s paper’s 50th anniversary.

    See the full article here.

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  • richardmitnick 5:37 am on November 6, 2014 Permalink | Reply
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    From NYT: “Funding Is Restored for Storied California Observatory” 

    New York Times

    The New York Times

    NOV. 5, 2014

    NYT Dennis Overbye
    DENNIS OVERBYE

    A year after the University of California announced that it would phase out all funding for its storied Lick Observatory, sparking fears that the observatory could close if it could not find outside support, the university said on Tuesday that it had changed its mind.

    As Aimée Dorr, provost and executive vice president of the university, and Nathan Brostrom, executive vice president, said in an Oct. 29 letter to the acting director of the observatory, Claire Max of the University of California, Santa Cruz, “We are rescinding our previous requirements that Lick Observatory become self supporting.”

    Lick, which started operations in 1888, is the oldest mountaintop observatory in the West, located on Mount Hamilton, about 30 miles south of San Francisco. In recent years it has played a pivotal role in the discovery of dark energy, which resulted in a Nobel Prize in 2011, and of planets around other stars.

    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    UCO Lick Shane Telescope

    Lick costs the university about $1.3 million a year to operate, money that the university said was needed in a time of declining state support for new ventures like the mighty Keck telescopes it owns with Caltech on Mauna Kea in Hawaii and the even mightier Thirty Meter Telescope, an international project under construction on Mauna Kea.

    Keck Observatory
    Keck Observatory Interior
    Keck

    TMT
    TMT Schematic
    TMT

    Acknowledging widespread interest among astronomers in keeping Lick alive, Provost Dorr and Mr. Brostrom wrote that they had never said they intended to close Lick and that recent budget plans suggested it could continue to operate without wrecking other projects.

    “Indeed,” they wrote, “we see the Lick, Keck and Thirty Meter Telescope Observatories as an integrated ecosystem that can together maintain and grow U.C.’s leadership in astronomy.”

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  • richardmitnick 3:48 pm on October 30, 2014 Permalink | Reply
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    From NYT: “From Ancient DNA, a Clearer Picture of Europeans Today” 

    New York Times

    The New York Times

    OCT. 30, 2014
    Carl Zimmer

    About 50,000 years ago, humans from Africa first set foot in Europe. They hunted woolly mammoths and other big game — sometimes to extinction. Eventually, they began grazing livestock and raising crops.

    They chopped down forests and drained swamps, turning villages into towns, then cities and capitals of empires. But even as they altered the Continent, Europeans changed, too.

    Their skin and hair grew lighter. They gained genetic traits particular to the regions in which they lived: Northern Europeans, for example, grew taller than Southern Europeans.

    Up till now, scientists have learned about evolution on the Continent mostly by looking at living Europeans. But advances in biotechnology have made it possible to begin extracting entire DNA from the bones of ancestors who lived thousands of years ago. Their genomes are like time machines, allowing scientists to see bits of European history playing out over thousands of years.

    Recently David Reich, a geneticist at Harvard Medical School, and his colleagues analyzed the genomes of nine ancient Europeans. Eight belonged to hunter-gatherers who lived about 8,000 years ago, seven in what is now Sweden and one in Luxembourg. The ninth came from a farmer who lived 7,000 years ago in present-day Germany.

    The scientists compared these genomes with those of living Europeans. As they reported last month in Nature, the study revealed something scientists never knew: Europeans today have genes from three very different populations.

    The oldest of these populations were the first Europeans, who appear to have lived as hunter-gatherers. The second were farmers who expanded into Europe about 8,500 years ago from the Near East.

    But most living Europeans also carry genes from a third population, which appears to have arrived more recently. Dr. Reich and his colleagues found the closest match in DNA taken from a 24,000-year-old individual in Siberia, suggesting that the third wave of immigrants hailed from north Eurasia. The ancient Europeans that the scientists studied did not share this North Eurasian DNA. They concluded that this third wave must have moved into Europe after 7,000 years ago.

    Last week, another team of scientists based at University College Dublin reported data from an even bigger haul of ancient European genomes — 13, all told. While Dr. Reich and his colleagues studied ancient Europeans separated by hundreds of miles, the Dublin team focused on just one region in Central Europe called the Great Hungarian Plain.

    The people whose genomes the scientists retrieved lived on the plain at various times between 7,700 years ago and 2,800 years ago.

    “What’s really exciting here is to have a transect through time,” said Johannes Krause, a co-director of the Max Planck Institute for History and the Sciences in Jena, Germany, who was not involved in the study. “It’s the first time that’s been done.”

    Archaeological digs have revealed evidence of farming on the plain as long as 8,000 years ago. People there raised crops like barley, and raised cattle and other livestock. Shards of pottery show that they consumed milk.

    The oldest genomes retrieved from human remains in the area — one from a man and one from a woman — date back to the dawn of agriculture on the plain. The woman’s DNA showed that she belonged to the ancient farming population documented by Dr. Reich and his colleagues.

    The man, however, did not have the genes of a farmer. He belonged to the oldest population of hunter-gatherers.

    “The archaeological information isn’t enough to say whether he was married to a local farmer,” said Ron Pinhasi, an archaeologist at University College Dublin and a co-author of the new study. It may even be that the man’s skull was a trophy of some sort, Dr. Pinhasi added.

    Archaeologists have found that early farming culture didn’t change drastically for the next 3,700 years. But about 4,000 years ago, the Bronze Age arrived. People started using bronze tools, trading over longer networks and moving into fortified towns.

    Dr. Pinhasi and his colleagues found that the era also brought a sudden shift in human DNA. A new population arrived on the Great Hungarian Plain, and Dr. Reich believes he knows who they were: the northern Eurasians.

    “It’s very exciting,” he said. “It documents that by this time in Central Europe, this Eastern influence had already arrived.”

    At the start of the Bronze Age, life settled down on the plain for a thousand years. But then came the Iron Age, bringing another shift in culture — and genes.

    People began traveling across the plain by horse-drawn chariots and wagons, and the genomes from 2,800 years ago show that the people of the Bronze Age had begun to be supplanted by a new Iron Age population. These are the people most closely related to living Hungarians.

    In the new study, Dr. Pinhasi and his colleagues also surveyed individual genes known to have changed over the course of European history.

    Today, for example, people in Hungary tend to have light skin and light brown hair, and half of them carry a mutation that lets them digest milk as adults. It took thousands of years for the genes for these traits to appear on the Great Hungarian Plain, the scientists found.

    The hunter-gatherer that lived 7,700 years ago, for example, probably had black hair and dark skin, along with blue eyes. His genes suggest that he also probably couldn’t digest milk — not surprising, since he came from a population that didn’t raise livestock.

    The ancient farmer woman, on the other hand, probably had dark brown hair and brown eyes. But like the hunter-gatherers, she lacked the genetic mutation for digesting milk.

    woman
    A 7,700-year-old skeleton of a woman found in Hungary has yielded DNA. Scientists have found that she belonged to a wave of early farmers who moved into Europe from the Near East. Credit Ron Pinhasi

    It is not until 6,400 years ago that the scientists find the first genetic evidence on the Great Hungarian Plain for light brown hair. And the milk mutation appeared even later, just 3,100 years ago.

    It is possible that these new genes and others were brought to the plain by successive waves of immigrants. But natural selection probably played a role in making these genes pervasive.

    Genetic mutations that enable people to drink milk as adults, for example, could have helped them survive famines. In cow-herding cultures, scientists have found, the milk-drinking mutation led to a 10 percent increase in the number of children.

    If that’s true, then for 4,600 years people on the Great Hungarian Plain were milking cows but lacked the ability to digest milk. Dr. Pinhasi suggested that they only used milk at first to make cheese and yogurt, which would have been easier to digest.

    Daniel G. Bradley, a geneticist at University College Dublin and co-author of the new study, predicted more unexpected results would emerge as scientists gather more ancient DNA in Europe.

    “The past is going to be a different country,” he said, “and it’s going to surprise us.”

    See the full article here.

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  • richardmitnick 6:49 pm on October 20, 2014 Permalink | Reply
    Tags: , , New York Times   

    From NYT: “25 Years Ago, NASA Envisioned Its Own ‘Orient Express’” 

    New York Times

    The New York Times

    OCT. 20, 2014
    KENNETH CHANG

    The National Aero-Space Plane was to be a revolutionary advance beyond the space shuttle.

    plane

    In his 1986 State of the Union address, President Ronald Reagan promised “a new Orient Express that could, by the end of the next decade, take off from Dulles Airport and accelerate up to 25 times the speed of sound, attaining low-earth orbit or flying to Tokyo within two hours.”

    On Oct. 3, 1989, an article in Science Times, Designing a Plane for the Leap of Space (and Back), reported frenetic activity at NASA and the Defense Department.

    “Scientists and engineers are making rapid progress in developing technologies needed to build a 17,000-mile-an-hour ‘space plane’ that could escape earth’s gravity and circle the globe in 90 minutes,” the article began.

    “Their goal,” it continued, “is a space plane that could take off and land from virtually any airport in the world, carry satellites and other space cargo into orbit cheaply, shuttle between the earth and an orbiting space station, or carry a load of bombs deep into enemy territory as fast as an intercontinental missile.”

    Proponents contended the space plane would be far cheaper to operate than the shuttle.

    Others were dubious. The Air Force, which was providing most of the financing, had already tried to back out, but the National Space Council, headed by Vice President Dan Quayle, recommended continuing work at a slower pace.

    The target for the first flight of the first experimental version, known as the X-30, was originally 1993 but was pushed back to 1997.

    25 YEARS LATER The space plane, able to fly by itself to orbit, never took off. The X-30 died in 1994. Smaller-scale hypersonic programs came and went.

    Was the X-30 technologically feasible?

    “No, and it’s still not,” said Jess Sponable, a program manager in the tactical technology office at Darpa, the Defense Advanced Research Projects Agency. For X-30 to succeed, infant ideas would have had to have been developed into robust, reliable technologies — materials that could survive intense temperatures, air-breathing engines that could fly faster and higher.

    Nonetheless, “absolutely, it was worthwhile,” Mr. Sponable said, although he added perhaps not worth the more than $1.6 billion spent. “We learned a lot.”

    The pendulum for spacecraft design has since swung away from the cutting edge to the tried and true. The Orion craft, which NASA is building for deep-space missions, is a capsule, just like the one used for the Apollo moon missions but bigger. The two private company designs that NASA chose to take future astronauts to the space station are also capsules. (The loser in that competition was a mini-shuttle offering.)

    NASA Orion Spacecraft
    NASA/Orion

    But the dream of hypersonic space planes continues.

    At Darpa, Mr. Sponable heads the XS-1 space plane project. It is not a do-it-all-at-once effort like the 1980s space plane but a much simpler, unmanned vehicle that would serve as a reusable first stage.

    Mr. Sponable is eager to figure out how to send it up many times, quickly and cheaply; the goal is 10 flights in 10 days.

    “We want operability No. 1,” he said. With the quick launches, the issue of cost “just disappears, because we can’t spend a lot of money from Day 1 to Day 2 to Day 3.”

    Darpa has awarded contracts to three industry teams to develop preliminary designs. Mr. Sponable said the decision of a next step would come next spring.

    The space plane episode illustrates the recurring money woes that have bedeviled NASA for decades: A grandiose plan is announced with fanfare and a burst of financing that fades as delays and cost overruns undercut the optimistic plans. Then a new president or a new NASA administrator changes course.

    Most recently, the Obama administration canceled plans started under President George W. Bush to send astronauts back to the moon and told NASA to consider an asteroid instead.

    If the pattern continues, NASA priorities could zig again after the next president moves into the White House in 2017.

    See the full article here.

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  • richardmitnick 5:10 pm on October 8, 2014 Permalink | Reply
    Tags: , , , , , New York Times   

    From Dennis Overbye at the New York Times: “How to Make a Black Hole” 

    New York Times

    The New York Times

    On July 2, 1967, a network of satellites designed to detect tests of nuclear weapons recorded a flash of gamma rays coming from the wrong direction — outer space.

    And so it was that human astronomers were tipped to the existence of one of the most violent phenomena of nature. Today, they know that about once a day somewhere in the observable universe, an explosion called a gamma-ray burst occurs, releasing more energy in a few seconds than our galaxy does in a year.

    These magnificent cosmic conflagrations are as far away as they are rare, which is just as well. If one happened nearby, in our own galaxy, we could be swathed with radiation. The closest gamma-ray burst whose distance has been measured happened some 119 million light-years from us, far outside the so-called Local Group, which contains our own Milky Way galaxy. The farthest so far recorded is now 31 billion light-years away, as calculated by the mathematics of the expanding universe; it happened when the universe was only 500 million years old.

    local group
    Local Group

    Gamma-ray bursts are thought to be the final step in the series of transformations by which stars shrink and slump from blazing glory to oblivion, winding up as bottomless deadly dimples in the fabric of space-time — that is to say, as black holes.

    The hierarchy of dead stars goes like this: Stars like the sun, when they run out of thermonuclear fuel, shrink to cinders known as white dwarfs, the size of Earth. Stars more massive than the sun might collapse more drastically and undergo a supernova explosion, blasting newly formed heavy elements into space to enrich future stars, planets and perhaps life, and leaving behind crushed cores known as neutron stars. These weigh slightly more than the sun but are only 12 miles or so in diameter — so dense that a teaspoonful on Earth would weigh as much as Mount Everest.

    Such an explosion, bright enough to be seen in daylight, happened in 1054, Earth time, as told by Chinese astronomers and the ancient inhabitants of Chaco Canyon in what is now New Mexico. That supernova left behind the Crab nebula, a tangle of glowing shreds of gas and a pulsar — a magnetized neutron star spinning 30 times a second, whipping the gas with magnetic fields that make it glow.

    Crab
    Crab Nebula

    Neutron stars, theorists say, are the densest stable form of matter, but they are not the end of the story. According to theory, too much mass accumulating on a neutron star can cause its collapse into a black hole, an abyss from which not even light can escape. The signature of such a cataclysm would be a gamma-ray burst, astronomers say.

    col
    Colliding neutron stars

    Supercomputer simulations by astronomers led by Luciano Rezzolla of the Institute of Theoretical Physics in Frankfurt have recently showed this would work.

    The simulation, as it unwound over six weeks of supercomputer time at the Max Planck Institute for Gravitational Physics, started with two neutron stars orbiting each other at a distance of 11 miles. That would not be unusual in the universe; most stars are in fact part of double-star systems and several pairs of pulsars orbiting each other are already known. They will eventually collide because such dense, heavy objects lose energy rapidly and spiral together.

    In the case of Dr. Rezzolla’s computation, it took seven milliseconds for tidal forces from the larger star’s gravity to rip apart the smaller star and unwind it into a spiral resembling flaming toothpaste writhing with magnetic fields and begin munching up the gas.

    The excess plasma forms a fat disk around the new black hole, and its magnetic fields, a billion times stronger than those in the sun, align to channel beams of radiation and particles out at the speed of light. The result is a gamma-ray burst visible across the universe, carrying the news of doom — the last astronomers will ever hear of these stars.

    For those two stars, the last bang was the best. Oblivion can be such a lovely sight.

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  • richardmitnick 8:36 pm on September 28, 2014 Permalink | Reply
    Tags: , , New York Times   

    From NYT: “Building an Ark for the Anthropocene” 

    New York Times

    The New York Times

    SEPT. 27, 2014
    JIM ROBBINS

    WE are barreling into the Anthropocene, the sixth mass extinction in the history of the planet. A recent study published in the journal Science concluded that the world’s species are disappearing as much as 1,000 times faster than the rate at which species naturally go extinct. It’s a one-two punch — on top of the ecosystems we’ve broken, extreme weather from a changing climate causes even more damage. By 2100, researchers say, one-third to one-half of all Earth’s species could be wiped out.

    ark

    As a result, efforts to protect species are ramping up as governments, scientists and nonprofit organizations try to build a modern version of Noah’s Ark. The new ark certainly won’t come in the form of a large boat, or even always a place set aside. Instead it is a patchwork quilt of approaches, including assisted migration, seed banks and new preserves and travel corridors based on where species are likely to migrate as seas rise or food sources die out.

    The questions are complex. What species do you save? The ones most at risk? Charismatic animals, such as lions or bears or elephants? The ones most likely to survive? The species that hold the most value for us?

    One initiative, the Intergovernmental Platform on Biodiversity and Ecosystem Services formed in 2012 by the governments of 121 countries, aims to protect and restore species in wild areas and to protect species like bees that carry out valuable ecosystem service functions in the places people live. Some three-quarters of the world’s food production depends primarily on bees.

    “We still know very little about what could or should be included in the ark and where,” said Walter Jetz, an ecologist at Yale involved with the project. Species are being wiped out even before we know what they are.

    Another project, the EDGE of Existence, run by the Zoological Society of London, seeks to protect the most unusual wildlife at highest risk. These are species that evolved on their own for so long that they are very different from other species. Among the species the project has helped to preserve are the tiny bumblebee bat and the golden-rumped elephant shrew.

    While the traditional approach to protecting species is to buy land, preservation of the right habitat can be a moving target, since it’s not known how species will respond to a changing climate.

    To complete the maps of where life lives, scientists have enlisted the crowd. A crowdsourcing effort called the Global Biodiversity Information Facility identifies and curates biodiversity data — such as photos of species taken with a smartphone — to show their distribution and then makes the information available online. That is especially helpful to researchers in developing countries with limited budgets. Another project, Lifemapper, at the University of Kansas Biodiversity Institute,

    “We know that species don’t persist long in fragmented areas and so we try and reconnect those fragments,” said Stuart L. Pimm, a professor of conservation at Duke University, and head of a nonprofit organization called SavingSpecies. One of his group’s projects in the Colombian Andes identified a forest that contains a carnivorous mammal that some have described as a cross between a house cat and a teddy bear, called an olinguito, new to science. Using crowd-sourced data, “we worked with local conservation groups and helped them buy land, reforest the land and reconnect pieces,” Dr. Pimm says.

    Coastal areas, especially, are getting scrutiny. Biologists in Florida, which faces a daunting sea level rise, are working on a plan to set aside land farther inland as a reserve for everything from the MacGillivray’s seaside sparrow to the tiny Key deer.

    To thwart something called “coastal squeeze,” a network of “migratory greenways” is envisioned so that species can move on their own away from rising seas to new habitat. “But some are basically trapped,” said Reed F. Noss, a professor of conservation biology at the University of Central Florida who is involved in the effort, and they will most likely need to be picked up and moved. The program has languished, but Amendment 1, on the ballot this November, would provide funding.

    One species at risk is the Florida panther. Once highly endangered, with just 20 individuals left, this charismatic animal has come back — some. But a quarter or more of its habitat is predicted to be under some three feet of water by 2100. Males will move on their own, but females will need help because they won’t cross the Caloosahatchee River. Experts hope to create reserves north of the river, and think at some point they will have to move females to new quarters.

    Protecting land between reserves is vital. The Yellowstone to Yukon Conservation Initiative, known as Y2Y, would protect corridors between wild landscapes in the Rockies from Yellowstone National Park to northern Canada, which would allow species to migrate.

    RESEARCHERS have also focused on “refugia,” regions around the world that have remained stable during previous swings of the Earth’s climate — and that might be the best bet for the survival of life this time around.

    A section of the Driftless Area encompassing northeastern Iowa and southern Minnesota, also known as Little Switzerland, has ice beneath some of its ridges. The underground refrigerator means the land never gets above 50 or so degrees and has kept the Pleistocene snail, long thought extinct, from disappearing there. Other species might find refuge there as things get hot.

    A roughly 250-acre refugia on the Little Cahaba River in Alabama has been called a botanical lost world, because of its wide range of unusual plants, including eight species found nowhere else. Dr. Noss said these kinds of places should be sought out and protected.

    Daniel Janzen, a conservation ecologist at the University of Pennsylvania who is working to protect large tracts in Costa Rica, said that to truly protect biodiversity, a place-based approach must be tailored to the country. A reserve needs to be large, to be resilient against a changing climate, and so needs the support of the people who live with the wild place and will want to protect it. “To survive climate change we need to minimize the other assaults, such as illegal logging and contaminating water,” he said. “Each time you add one of those you make it more sensitive to climate change.”

    The Svalbard Global Seed Vault, beneath the permafrost on an island in the Arctic Ocean north of mainland Norway, preserves seeds from food crops. Frozen zoos keep the genetic material from extinct and endangered animals. The Archangel Ancient Tree Archive in Michigan, meanwhile, founded by a family of shade tree growers, has made exact genetic duplicates of some of the largest trees on the planet and planted them in “living libraries” elsewhere — should something befall the original.

    In 2008, Connie Barlow, a biologist and conservationist, helped move an endangered conifer tree in Florida north by planting seedlings in cooler regions. Now she is working in the West. “I just assisted in the migration of the alligator juniper in New Mexico by planting seeds in Colorado,” she said. “We have to. Climate change is happening so fast and trees are the least capable of moving.”

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  • richardmitnick 4:44 am on September 13, 2014 Permalink | Reply
    Tags: , New York Times,   

    From The New York Times: “A Lost-and-Found Nomad Helps Solve the Mystery of a Swimming Dinosaur” 

    New York Times

    The New York Times

    SEPT. 11, 2014
    KENNETH CHANG

    The first bones came in a cardboard box. Nizar Ibrahim, a paleontologist, was in the Moroccan oasis town of Erfoud at the edge of the Sahara, returning from a dinosaur dig in the sands. Inside the box, brought to him by a nomad, were sediment-encrusted pieces more intriguing than anything he had found himself, including a blade-shaped bone with a reddish streak running through the cross section. He took the bones to a university in Casablanca.

    That was April 2008.

    The next year, he was in Italy visiting colleagues at the Milan Natural History Museum who showed him bones that seemed to be from Spinosaurus aegyptiacus, a strange-looking predatory dinosaur larger than Tyrannosaurus Rex that lived in northern Africa about 95 million years ago.

    He looked at the spines, part of a giant distinctive sail on the back of Spinosaurus. He saw a familiar red line — possibly a passageway for blood vessels long since decayed away — in the cross section of a bone. “My mind started racing,” he said.

    big
    An artist’s interpretation of how Spinosaurus aegyptiacus might have looked and how its size might have compared with that of a human. Credit Davide Bonadonna

    Amazingly, the pieces in Milan and those he had seen a year earlier and 1,200 miles away were from the same ancient skeleton.

    That was the start of an odyssey of diligence and serendipity that led to the unveiling on Thursday of a new skeleton of Spinosaurus. The largest known predatory dinosaur, growing to at least 50 feet in length, Spinosaurus is also the only dinosaur known to be a swimmer that spent a large fraction of its life in the water.

    “It’s probably the most bizarre dinosaur out there,” said Dr. Ibrahim, a graduate student when he saw the first bones, and now a postdoctoral researcher at the University of Chicago.

    Spinosaurus had been an intriguing mystery for decades. The original fossil of the dinosaur, discovered in Egypt a century ago and moved to a German museum, was destroyed during World War II, leaving paleontologists with little more than a few drawings to ponder.

    The new partial skeleton is of a Spinosaurus not fully grown, about 36 feet long. Its forelimbs were large and strong, with scythe-like claws; its hind legs were short, with paddle-shaped feet.

    In an article published online on Thursday by the journal Science, Dr. Ibrahim and an international team of colleagues describe the features that made the dinosaur well suited for swimming and feasting on giant fish that lived in the rivers there.

    Conical teeth in a crocodilian snout overlapped like a snare for trapping fish, and it had nostrils halfway up the skull so it could stick its snout into the water and still breathe.

    With its flat feet, Spinosaurus may have paddled like a duck. It had a long, flexible tail, which it may have used for propulsion. “It’s like a cross between an aquatic bird and a crocodile,” said Paul C. Sereno, a paleontologist at the University of Chicago who was part of the research team.

    On land, Spinosaurus was ungainly. The researchers calculated that its center of mass would have been too far forward for it to have stood easily on its hind legs, like other predator dinosaurs; instead, it ambled on all four legs.

    “It does add significantly to the strangeness,” said Matthew C. Lamanna, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, who was not involved with the research. He described the evidence for Spinosaurus’s semiaquatic existence as “quite convincing.”

    model
    A life-size model of Spinosaurus aegyptiacus made from polystyrene, resin and steel. The model was created from computer scans of fossils, images of lost bones and educated guesses using bones from related dinosaurs. Credit Mike Hettwer/National Geographic

    An exhibition on Spinosaurus opens Friday at the National Geographic Museum in Washington. The National Geographic Society provided financing for the research.

    The new findings may return prominence to Ernst Stromer, the German paleontologist who first described Spinosaurus aegyptiacus, meaning “Egyptian spine lizard.”

    Stromer’s fossil, mounted in the Bavarian State Collection of Paleontology in Munich, included the lower jaw and parts of the spine.

    In April 1944, the British Royal Air Force dropped a bomb on the museum, and Spinosaurus — and every Egyptian dinosaur fossil known at the time — burned.

    After that, some isolated bones of Spinosaurus were found, but nothing as complete as Stromer’s specimen. Some evidence, like the conical teeth, suggested Spinosaurus ate fish, but perhaps it just waded into a river and caught them like a grizzly bear.

    One fossil, uncovered in Morocco around 1975, had been thought to be part of the lower jaw of a crocodile, but a decade ago, Cristiano Dal Sasso of the Milan museum realized that interpretation was upside down. “There were too many bones to be the lower jaw,” he said.

    It was actually from the top half of a snout of a huge adult Spinosaurus.

    In 2008, an Italian geologist showed the new Spinosaurus bones to Dr. Dal Sasso, who then showed them to Dr. Ibrahim.

    But the scientists were missing crucial geological information about where the bones had been excavated.

    Dr. Ibrahim needed to find the nomad, so last year, he returned to the Erfoud area.

    A researcher helping him, Samir Zouhri, of University Hassan II Casablanca, asked how they would locate the man, whether Dr. Ibrahim had a name or an address or a phone number.

    “I didn’t want to disappoint my Moroccan colleague,” Dr. Ibrahim said, “so I told him I distinctly remember that the man had a mustache.”

    Dr. Zouhri did not seem impressed. “He basically thought that was not an adequate starting point for our wild-goose chase,” Dr. Ibrahim said.

    The search indeed proved fruitless, and they were sitting in a cafe, about to give up, when a mustachioed man walked past.

    It was the nomad who had showed Dr. Ibrahim the Spinosaurus bones five years earlier.

    “I had to run, because he was walking fast,” Dr. Ibrahim said. “He recognized me, and I convinced him to take us to the site.”

    The nomad, who Dr. Ibrahim said did not want public attention, remains anonymous.

    A few months later, Dr. Ibrahim and other members of the research team returned, uncovering more bone fragments and confirming that the fossils Dr. Ibrahim had seen in 2008 and those in Milan were all from the same dinosaur.

    The partial skeleton — about a quarter to a third of the animal, Dr. Sereno estimated — did not tell the whole story. The researchers made a three-dimensional digital model of the bones and added pieces scanned from other fossils like the Milan snout and the Stromer drawings.

    The new fossil also served as a Rosetta stone. A second dinosaur fossil of Stromer’s turned out to be a Spinosaurus; some of its bones matched those from the Moroccan find.

    Putting all the pieces together and making educated guesses from close relatives of Spinosaurus, the researchers came up with a complete skeleton and produced a life-size model for the National Geographic exhibition.

    The dearth of swimming dinosaurs has been something of a mystery. Among other groups of animals, some species did move from land to water — for instance, the mammals that evolved into whales. Even among birds, the modern-day descendants of dinosaurs, some like penguins and ducks spend copious time in the water.

    “Dinosaurs were landlubbers,” Dr. Sereno said. “Until this one.”

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