Items tagged with: may
HN Discussion: https://news.ycombinator.com/item?id=19666148
Posted by dessant (karma: 702)
Post stats: Points: 167 - Comments: 68 - 2019-04-15T15:47:08Z
#HackerNews #adblock #arbitrary #code #execute #filter #lists #may #pages #plus #web
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#aux #breakingnews #brexit #may #news #parlementaires #présente #report #theresa
Le bloc européen a fixé le report du Brexit au 31 octobre. La première ministre s'est présentée devant les élus pour leur expliquer ce qu'elle fera du temps donné par l'Union européenne.
posted by pod_feeder
#breakingnews #brexit #journée #marathon #may #news #nouvelle #pour #theresa #une
Theresa May rencontre Angela Merkel, puis Emmanuel Macron aujourd'hui. Son objectif est de les convaincre de soutenir sa nouvelle demande de report du Brexit lors du sommet européen de ce mercredi.
posted by pod_feeder
A new theory challenges assumptions about when and how our ancestors altered their behaviors to boost brainpower
Article word count: 1075
HN Discussion: https://news.ycombinator.com/item?id=19600420
Posted by hourislate (karma: 3377)
Post stats: Points: 174 - Comments: 93 - 2019-04-07T22:42:35Z
#HackerNews #bigger #brains #fat #have #hominin #led #may #meat #not
Northern Ethiopia was once home to a vast, ancient lake. Saber-toothed cats prowled around it, giant crocodiles swam within. The streams and rivers that fed it—over 3 million years ago, during the Pliocene—left behind trails of sediment that have now hardened into sandstone.
Deposited within these layers are fossils: some of early hominins, along with the bones of hippos, antelope, and elephants. Anthropologist Jessica Thompson encountered two of these specimens, from an area named Dikika, in 2010.
At the time, she was a visiting researcher at the Institute of Human Origins at Arizona State University. Given no explanation as to their history, she analyzed the bones and found signs of butchery. Percussion marks suggested someone may have accessed the marrow; cut marks hinted that flesh was stripped from bone. To her surprise, the specimens were 3.4 million years old, putting the butcher’s behaviors back 800,000 years earlier than conventional estimates would suggest. That fact got Thompson, now an assistant professor in the department of anthropology at Yale University, thinking there might be more traces of tool use from those early times.
In a wide-ranging review published in February’s issue of Current Anthropology, Thompson joins a team of researchers to weave together several strands of recent evidence and propose a new theory about the transition to large animal consumption by our ancestors. The prevailing view, supported by a confluence of fossil evidence from sites in Ethiopia, is that the emergence of flaked tool use and meat consumption led to the cerebral expansion that kickstarted human evolution more than 2 million years ago. Thompson and her colleagues disagree: Rather than using sharpened stones to hunt and scrape meat from animals, they suggest, earlier hominins may have first bashed bones to harvest fatty nutrients from marrow and brains.
Humans are the only primate to regularly consume animals larger than themselves. This nutritional exploitation, something Thompson and her colleagues call the “human predatory pattern,” has long been synonymous with the flesh-eating, man-the-hunter view of human origins.
Because large animals such as antelope pack a serious micro-and-macro-nutrient punch, scientists have thought their meat contributed to humanity’s outsized brains. A consensus arose in the 1950s that our ancestors first hunted small animals before moving on to larger beasts around 2.6 million years ago. Flaked tool use and meat eating became defining characteristics of the Homo genus.
“It’s a very appealing story,” says Thompson. “Right around that time there appeared to be the first stone tools and butchery marks. You have the origins of our Homo genus. A lot of people like to associate that with what it means to be human.”
Then, starting in the mid-1980s, an opposing theory arose in which Homo’s emergence wasn’t so tightly coupled with the origins of hunting and predatory dominance. Rather, early hominins first accessed brain-feeding nutrients through scavenging large animal carcasses. The debate has rolled on through the decades, with evidence for the scavenging theory gradually building.
The new paper goes further: Harvesting outer-bone meat would have come at significant costs, the authors argue. The chance of encountering predators is high when scraping raw flesh from a carcass. Chewing raw meat without specialized teeth doesn’t give much energetic benefit, studies have shown. In addition, meat exposed to the elements will quickly rot.
Marrow and brains, meanwhile, are locked inside bones and stay fresh longer. These highly nutritional parts are also a precursor to the fatty acids involved with brain and eye development. And more easily than flesh-meat, bones could be carried away from carcass sites, safe from predators.
Conventional thinking has been that the behavioral package of early hominins was to go after meat and marrow together, explains Briana Pobiner, a paleoanthropologist at the Smithsonian Institution, who did not contribute to the new paper. But in the new paper, she says, “This team has shown that marrow may have in fact been more important. It’s a nuance, but an important nuance.”
The Pliocene—between 5.3 and 2.6 million years ago—was an era of dramatic change. An intensely variable and cooling climate transformed vast swaths of rainforest into mosaics of grassland and savanna. Large clearings spawned ecological niches for opportunistic and versatile hominins like Australopithecus, a likely contender for the Homo ancestor, and Kenyanthropus to fill in. Larger predators may well have left carcasses for them to scavenge.
Evidence suggests hominins shifted their diet around 3.76 million years ago as they took advantage of the open spaces. By around 3.5 million years ago, some species of Australopithecus already showed increased brain sizes, up to 30 percent larger than chimpanzees of comparable body size. Canines had shrunk to proportions later seen in the genus Homo, and hand morphology was already more human than ape, with potential both for terrestrial travel and tool use.
Percussive tools, the authors argue, were the key to the transition to large animal exploitation. Rocks could bash open bones, exposing the marrow inside. The alternative—that humans sharpened stone against stone, creating a flaked tool to carve meat from bone—seems more onerous, they say. They argue that such meat carving and the associated tool creation would likely come later.
As to who wielded these percussive instruments, the timeline presents a puzzle. The earliest Homo specimen is now dated to 2.8 million years. The Dikika fossils suggest butchery behaviors at 3.4 million years ago. Homo may have emerged earlier than scientists suspected—a theory that would need more fossil evidence to support it—or another hominin, such as Australopithecus, may have created tools before Homo.
Some scholars aren’t convinced by the study’s arguments, however. For example, Craig Stanford, an anthropologist at the University of Southern California, questions the emphasis on hominin scavenging behavior appearing before hunting. “We have no examples today of animals that scavenge but don’t hunt,” he adds.
To test the new theory, the review authors suggest seeking out further evidence of percussive tools that predate flaked tools. Researchers could, they note, broaden the search for the signatures of such instruments within both the existing fossil record and at dig sites. Thompson’s graduate students, for example, are using 3D scanning and artificial intelligence techniques to improve the identification of marks on fossils—whether they were created by early hominins, saber-toothed cats, hyenas, or other types of creatures.
What they uncover could deal a blow to their theory, but it will also, undoubtedly, enrich our understanding of how our ancestors evolved.
This work first appeared on SAPIENS under a CC BY-ND 4.0 license. Read the original here.
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#avec #breakingnews #brexit #défend #dialogue #dun #lopposition #may #news #nécessité
Dans une vidéo, Theresa May a défendu la nécessité d'un dialogue avec les travaillistes, pour trouver un accord sur le Brexit.
posted by pod_feeder
#breakingnews #brexit #carte #conclure #corbyn #joue #may #news #pour
La Première ministre britannique, Theresa May, mise sur son opposition travailliste pour faire adopter l'accord de Brexit conclu par le Royaume-Uni avec l'Union européenne (UE). Les chefs d'Etat et de gouvernement de l'UE se retrouvent mercredi 10 avril à Bruxelles, à deux jours de l'échéance.
posted by pod_feeder
Count Casimir Pulaski is revered as the father of American cavalry. He came to America of his own volition to fight in the War of Independence. One of the Revolution’s great heroes, he was a very…
Article word count: 1813
HN Discussion: https://news.ycombinator.com/item?id=19592911
Posted by uxhacker (karma: 917)
Post stats: Points: 139 - Comments: 39 - 2019-04-06T20:43:11Z
#HackerNews #been #female #fought #general #have #may #polish #washington #who #with
April 5, 2019
Chadds Ford, Pennsylvania, 1777. At the end of a daylong battle, George Washington’s right flankSomewhere on the battlefield is Private Johan Wilhelm Seckel, 40, the first of his family born in America — and ancestor to ASU Now reporter Scott Seckel — serving with the Germantown Battalion Continental Troops in Capt. George Hubleyʼs Company. has completely collapsed. British troops are closing in.
A dashing Polish cavalry officer reports to Washington’s bodyguard that they are in danger of being surrounded. Washington orders Casimir Pulaski to gather as many men as he can. Count Pulaski discovers an escape route past the British advance, then wheels and charges enemy lines. The redcoats are astounded to be attacked by what they thought was a fleeing rabble. Washington escapes.
Pulaski is revered as the father of American cavalry. He came to America of his own volition to fight in the War of Independence. One of the Revolution’s great heroes, he was a loner. A very private person, he was extremely driven and difficult with people. (It’s one reason Washington simply ended up giving Pulaski his own legion, most of whom were Europeans.) Both superiors and subordinates considered him imperious. He was brave in battle to the point of recklessness. Detractors called him a loose cannon. Short and thin, pacing and speaking quickly, he lacked interest in women or drinking.
And he harbored a secret that lay unknown for more than 200 years, until an Arizona State University bioarchaeologist and a colleague discovered the truth.
Monday night a documentary unveiling the mystery airs on the Smithsonian Channel. But it doesn’t tell the whole story ...
In the late 1990s, Charles Merbs and his wife visited their daughter in Savannah, Georgia. A forensic anthropologist at Arizona State University’s now School of Human Evolution and Social Change, Merbs’ expertise lies in skeletal remains, especially reconstructing behavior from skeletons.
The family toured the historic city, including a visit to Casimir Pulaski’s monument. Merbs is Polish on his mother’s side. His mother always told him they were related to the Pulaskis and should be proud of that. (“It’s been impossible to prove,” he said. “The records just aren’t there.”)
Pulaski was mortally wounded during the Battle of Savannah. (Like most Revolutionary War battles, the American side lost.) He was hit in the groin by grapeshot. Grapeshot was pingpong-size metal balls collected in a canvas bag and fired from a cannon. It acted like shotgun pellets and was used as an antipersonnel round.
He was taken aboard an American ship, where he died a few days later.
“Then the story gets murky as to what happens to his body,” Merbs, now retired, said. “One story is that he was buried at sea on the way back to Charleston. The other story is that in the dead of night his body was taken ashore and buried by torchlight on a plantation. It was done secretly. The plantation owners knew about it and maintained the burial.”
In 1854, it was decided to build a monument to Pulaski. The bones were exhumed and reburied beneath the monument in a metal box.
A week after their visit to Savannah, Merbs’ daughter called. The monument was being taken down. Iron spacers between the stones were rusting. The whole thing was in danger of collapsing.
Merbs tracked down the physical anthropologist working with the bones — Karen Burns, of the University of Georgia — and offered to help. She accepted. “That’s how I got involved,” he said.
Before Merbs was allowed to examine the remains, however, he had to sign a document swearing him to secrecy.
“Basically I couldn’t say anything about what I found until the final report came out,” he said. “Dr. Burns said to me before I went in, ‘Go in and don’t come out screaming.’ She said study it very carefully and thoroughly and then let’s sit down and discuss it. I went in and immediately saw what she was talking about.
“The skeleton is about as female as can be.”
The next — and obvious — question: Was it Pulaski or someone else who had been stuck in the tomb because a skeleton was needed?
Everything seemed to match. The stature, age and general body build were all correct for Pulaski. There’s one contemporary portrait of Pulaski painted from life. There’s a black smudge below his left eye. “On the skull there is a bone defect right exactly there,” Merbs said.
Pulaski injured his right hand in a battle in Russia. “Sure enough; the fourth and fifth metacarpals in the right hand had fractured and had healed rather poorly, exactly where they were supposed to be,” he said.
Merbs has done forensic work with the Maricopa County Medical Examiner’s Office, including working with the skeletons of equestrians. Riding a lot shows up in skeletons. Horse rider’s syndrome is a whole series of issues that affect bones, primarily in the pelvis.
“That skeleton definitely showed signs of horseback riding,” Merbs said, including a new one he added to the lexicon of horse rider’s syndrome: the skeleton’s shoulder showed signs of holding arms high, as would be done holding and pulling back on reins or raising a heavy saber. (Cavalrymen killed enemies by swinging their swords directly down on the crown of their heads. Ever notice the tall bearskin caps worn by the guards at Buckingham Palace? They were designed to protect from exactly that blow.)
The forehead showed an injury consistent with a wound from a blade, although Merbs couldn’t be sure.
ASU Charles Merbs examines grapeshot which killed Pulaski
Charles Merbs examines the grapeshot that killed Casimir Pulaski. Photo courtesy of Charles Merbs
“Everything matched, except for the sex,” he said. “The sex was as clearly female as anything could be.”
Something that could be reasonably suspected of a woman in her 30s would be evidence of childbirth. “There were no parturition scars on this pelvis,” Merbs said.
The next step was a positive DNA identification. When the skeleton was exhumed in the 1850s, most of its teeth were missing, except for a few molars.
“Those teeth had been taken out when the skeleton was excavated,” he said.
This was evidence of a macabre but common custom of the time. During the Napoleonic Wars, when millions died in massive clashes, tooth hunters scavenged battlefields. Dead soldiers’ teeth were in great demand for making dentures. (In 1814 an Englishman recorded a meeting with a tooth hunter. When asked how he obtained them, he replied, “Oh sir, only let there be a battle, and there’ll be no want of teeth. I’ll draw them as fast as the men are knocked down.”) After the Battle of Waterloo in 1815, the market became so flooded they became known as Waterloo teeth. Because they came from healthy young men, they were advertised as such.
“It’s very likely around the time the people of Savannah were wearing Pulaski’s teeth,” Merbs said.
They had enough of Pulaski’s DNA to turn the investigation in that direction. But who could they compare it to? Burns and Merbs looked at Pulaski’s genealogy and found out he had two brothers and six sisters. Mitochondrial DNA is passed through women. Of the six sisters, only one had a child. Luckily it was a daughter. She had another daughter. Pulaski and his grandniece would share the same mitochondrial DNA.
Her grave was excavated and samples returned, but nothing usable turned up. “That was 20 years ago,” Merbs said.
Recently three young researchers, one of whom studied archaeology at ASU, decided to look into the mystery. DNA work had come quite a long way in 20 years. Something new might turn up. They got a lab to give them an analysis estimate, which turned out to be $18,000. They contacted the Smithsonian Institute, which funded the research last summer.
The results came back positive. The mitochondrial DNA was identical in both Pulaski and his grandniece.
“Now we know that the bones in the monument were indeed those of Pulaski, but we have the problem of the fact that they are female,” Merbs said. “Here’s the thing: if you go back and look at his life, what we know about it, there are interesting little clues along the way.”
Aristocratic Polish Catholic families in the 18th century traditionally held public baptisms in church.
“In his case it said he was suffering from some debilitatus, and they held off on the baptism and privately baptized him at home,” he said.
Suddenly, Pulaski’s personality traits — aloof, driven, private, brazen in battle — fell into line.
“We think the problem goes back to his birth and basically deciding whether he was a boy or a girl,” Merbs said.
Merbs’ oldest daughter is a professor at Johns Hopkins University School of Medicine. She put him in touch with a specialist in sex and gender issues.
“With scientists, sex and gender are two totally different things,” Merbs said. “Sex is biological, and gender is social and behavioral. Ordinarily the two go together, but you can have a conflict between the two. That’s what I think we were dealing with here.”
Merbs explained to the professor he thought they were dealing with a sex-gender problem. The professor took out a stack of photographs of bare babies and told him and his wife to put them in one of two piles — girls and boys — which they did.
“One hundred percent,” the professor said. “You are one hundred percent wrong. You were wrong on every single one.”
Merbs thinks the Pulaski family, faced with a similar situation, had to make a decision.
So Pulaski was raised as a man, in a military family. It was without question he would become an officer, and so he did.
“I don’t think, at any time in his life, did he think he was a woman,” Merbs said. “I think he just thought he was a man, and something was wrong. He had some kind of defect or something. Back in those days they just didn’t know.”
Did that perhaps play a part in Pulaski’s aggression on the battlefield?
“Oh, I think that’s a big part of it,” Merbs said. “I think his whole personality indicates he was driven, and I think that’s the reason why.”
Merbs kept his secret, until now.
“This was definitely not what the good folks of Savannah wanted us to find, and the whole thing became a political hot potato,” he said. “They wanted us to verify that the remains were indeed those of a male Pulaski, which would then be interred at Arlington.”
Without conclusive DNA evidence, it was considered that Burns and Merbsʼ observations were opinion, not fact. The bones were reburied next to the monument.
Burns died several years ago. Merbs has a small credit in the documentary. Both Merbs and Burns names appear in the Pulaski Exhibit in Savannah. Merbs’ contributions are clearly spelled out in an article about to be submitted to the Journal of Forensic Anthropology.
“America’s Hidden Stories: The General Was Female?” will air on the Smithsonian Channel at 8 and 11 p.m. Monday, April 8, and at 1 p.m. Tuesday, April 9.
Top image courtesy of the Library of Congress
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Particles' changing masses could explain why distant galaxies appear to be rushing away.
Article word count: 850
HN Discussion: https://news.ycombinator.com/item?id=19588996
Posted by hairytrog (karma: 91)
Post stats: Points: 112 - Comments: 51 - 2019-04-06T03:22:33Z
#HackerNews #2013 #claims #cosmologist #expanding #may #not #universe
TAKE 27 LTD/SPL
The conventional model of cosmology is that most galaxies recede from one another as space itself inflates like the surface of a balloon — which would explain why other galaxies appear redshifted from our own galaxyʼs point of view. But one cosmologist has a different interpretation of that redshift.
It started with a bang, and has been expanding ever since. For nearly a century, this has been the standard view of the Universe. Now one cosmologist is proposing a radically different interpretation of events — in which the Universe is not expanding at all.
In a paper posted on the arXiv preprint server^1, Christof Wetterich, a theoretical physicist at the University of Heidelberg in Germany, has devised a different cosmology in which the Universe is not expanding but the mass of everything has been increasing. Such an interpretation could help physicists to understand problematic issues such as the so-called singularity present at the Big Bang, he says.
Although the paper has yet to be peer-reviewed, none of the experts contacted by Nature dismissed it as obviously wrong, and some of them found the idea worth pursuing. “I think it’s fascinating to explore this alternative representation,” says Hongsheng Zhao, a cosmologist at the University of St Andrews, UK. “His treatment seems rigorous enough to be entertained.”
Astronomers measure whether objects are moving away from or towards Earth by analysing the light that their atoms emit or absorb, which comes in characteristic colours, or frequencies. When matter is moving away from us, these frequencies appear shifted towards the red, or lower-frequency, part of the spectrum, in the same way that we hear the pitch of an ambulance siren drop as it speeds past.
In the 1920s, astronomers including Georges Lemaître and Edwin Hubble found that most galaxies exhibit such a redshift — and that the redshift was greater for more distant galaxies. From these observations, they deduced that the Universe must be expanding.
But, as Wetterich points out, the characteristic light emitted by atoms is also governed by the masses of the atomsʼ elementary particles, and in particular of their electrons. If an atom were to grow in mass, the photons it emits would become more energetic. Because higher energies correspond to higher frequencies, the emission and absorption frequencies would move towards the blue part of the spectrum. Conversely, if the particles were to become lighter, the frequencies would become redshifted.
Because the speed of light is finite, when we look at distant galaxies we are looking backwards in time — seeing them as they would have been when they emitted the light that we observe. If all masses were once lower, and had been constantly increasing, the colours of old galaxies would look redshifted in comparison to current frequencies, and the amount of redshift would be proportionate to their distances from Earth. Thus, the redshift would make galaxies seem to be receding even if they were not.
Work through the maths in this alternative interpretation of redshift, and all of cosmology looks very different. The Universe still expands rapidly during a short-lived period known as inflation. But prior to inflation, according to Wetterich, the Big Bang no longer contains a ʼsingularityʼ where the density of the Universe would be infinite. Instead, the Big Bang stretches out in the past over an essentially infinite period of time. And the current cosmos could be static, or even beginning to contract.
The idea may be plausible, but it comes with a big problem: it canʼt be tested. Mass is what’s known as a dimensional quantity, and can be measured only relative to something else. For instance, every mass on Earth is ultimately determined relative to a kilogram standard that sits in a vault on the outskirts of Paris, at the International Bureau of Weights and Measures. If the mass of everything — including the official kilogramme — has been growing proportionally over time, there could be no way to find out.
For Wetterich, the lack of an experimental test misses the point. He says that his interpretation could be useful for thinking about different cosmological models, in the same way that physicists use different interpretations of quantum mechanics that are all mathematically consistent. In particular, Wetterich says, the lack of a Big Bang singularity is a major advantage.
He will have a hard time winning everyone over to his interpretation. “I remain to be convinced about the advantage, or novelty, of this picture,” says Niayesh Afshordi, an astrophysicist at the Perimeter Institute in Waterloo, Canada. According to Afshordi, cosmologists envisage the Universe as expanding only because it is the most convenient interpretation of galaxiesʼ redshift.
Others say that Wetterich’s interpretation could help to keep cosmologists from becoming entrenched in one way of thinking. “The field of cosmology these days is converging on a standard model, centred around inflation and the Big Bang,” says physicist Arjun Berera at the University of Edinburgh, UK. “This is why it’s as important as ever, before we get too comfortable, to see if there are alternative explanations consistent with all known observation.”
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#breakingnews #brexit #demande #may #news #nouveau #report #theresa
"Cher Donald" : dans une lettre adressée au président Conseil européen Theresa May souhaite que le Brexit soit repoussé jusqu'au 30 juin 2019. Paris estime prématurée cette demande qui impliquerait la participation du Royaume-Uni aux élections européennes prévues du 23 au 26 mai.
posted by pod_feeder
#avec #breakingnews #brexit #constructive #discute #lopposition #manière #may #news #quot #theresa #travailliste
Brexit : Theresa May a discuté de manière "constructive" avec le chef des travaillistes, Jeremy Corbyn, malgré leurs positions opposées.
posted by pod_feeder
#breakingnews #brexit #carte #corbyn #joue #may #news #theresa
La Première ministre britannique tend la main à son adversaire Jeremy Corbyn sur le Brexit. Une main que le leader de l'opposition semble vouloir saisir à en croire ses déclarations devant la Chambre des communes mercredi.
posted by pod_feeder
#breakingnews #brexit #européenne #lunion #may #news #nouveau #report #réclamer #theresa #veut
La Première ministre britannique a également indiqué lors d'une conférence de presse, qu'elle allait appeler Jeremy Corbyn, le leader de l'opposition, "pour trouver ensemble une solution".
posted by pod_feeder
#accord #breakingnews #brexit #may #news #quatrième #tentative #theresa
Theresa May devrait cette semaine tenter une nouvelle fois de faire adopter son accord de Brexit au parlement, un texte qui a déjà été rejeté trois fois par les députés.
posted by pod_feeder
#breakingnews #brexit #britanniques #des #députés #laccord #may #news #nouveau #sur #vote
Ils s'exprimeront pour la troisième fois sur cet accord de retrait du Royaume-Uni de l'Union européenne négocié par la Première ministre à Bruxelles.
posted by pod_feeder
#annoncée #après #breakingnews #britannique #démission #may #ministre #news #première #theresa
"Soutenez mon accord ou je m'en vais". En substance, c'est le message de Theresa May aux parlementaires et surtout à son propre camp, dont une partie reste hostile à son accord de Brexit. Mais que se passera-t-il quand elle quittera son poste ?
posted by pod_feeder
#annoncée #breakingnews #britanniques #comment #démission #ils #les #may #news #réagissent #theresa
Devant le parlement de Westminster, des électeurs se rassemblent. Ils n'ont pas tous voté la même chose lors du référendum, mais ici, cette annonce ne choque pas grand monde.
posted by pod_feeder
#avant #breakingnews #brexit #démissionner #les #may #news #négociations #prochaines #promet #theresa
La Première ministre britannique, Theresa May, a indiqué dans un communiqué qu'elle acceptait de quitter son poste avant la "prochaine étape de négociations" sur le Brexit.
posted by pod_feeder
#breakingnews #brexit #dans #immédiat #laccord #may #news #norganisera #pas #sur #theresa #troisième #vote
L'accord de Brexit négocié avec Bruxelles n'a "pas le soutien suffisant" au Parlement britannique pour être soumis une troisième fois au vote des députés, a déclaré ce lundi la Première ministre britannique, devant la Chambre des communes.
posted by pod_feeder
Feel like visiting another star system or dimension? You can do this by traveling through a spacetime portal of a black hole. But you better choose carefully. All black holes are not created equal.
Article word count: 941
HN Discussion: https://news.ycombinator.com/item?id=19479352
Posted by Pharmakon (karma: 1896)
Post stats: Points: 94 - Comments: 120 - 2019-03-24T23:28:28Z
#HackerNews #black #for #gentle #holes #hyperspace #may #portals #rotating #serve #travel
One of the most cherished science fiction scenarios is using a black hole as a portal to another dimension or time or universe. That fantasy may be closer to reality than previously imagined.
Black holes are perhaps the most mysterious objects in the universe. They are the consequence of gravity crushing a dying star without limit, leading to the formation of a true singularity – which happens when an entire star gets compressed down to a single point yielding an object with infinite density. This dense and hot singularity punches a hole in the fabric of spacetime itself, possibly opening up an opportunity for hyperspace travel. That is, a short cut through spacetime allowing for travel over cosmic scale distances in a short period.
Researchers previously thought that any spacecraft attempting to use a black hole as a portal of this type would have to reckon with nature at its worst. The hot and dense singularity would cause the spacecraft to endure a sequence of increasingly uncomfortable tidal stretching and squeezing before being completely vaporized.
Flying through a black hole
My team at the University of Massachusetts Dartmouth and a colleague at Georgia Gwinnett College have shown that all black holes are not created equal. If the black hole like Sagittarius A*, located at the center of our own galaxy, is large and rotating, then the outlook for a spacecraft changes dramatically. That’s because the singularity that a spacecraft would have to contend with is very gentle and could allow for a very peaceful passage.
The reason that this is possible is that the relevant singularity inside a rotating black hole is technically “weak,” and thus does not damage objects that interact with it. At first, this fact may seem counter intuitive. But one can think of it as analogous to the common experience of quickly passing one’s finger through a candle’s near 2,000-degree flame, without getting burned.
 [IMG]Hold your finger close to the flame and it will burn. Swipe it through quickly and you won’t feel much. Similarly, passing through a large rotating black hole, you are more likely to come out the other side unharmed. mirbasar/Shutterstock.com
My colleague Lior Burko and I have been investigating the physics of black holes for over two decades. In 2016, my Ph.D. student, Caroline Mallary, inspired by Christopher Nolan’s blockbuster film “Interstellar,” set out to test if Cooper (Matthew McConaughey’s character), could survive his fall deep into Gargantua – a fictional, supermassive, rapidly rotating black hole some 100 million times the mass of our sun. “Interstellar” was based on a book written by Nobel Prize-winning astrophysicist Kip Thorne and Gargantua’s physical properties are central to the plot of this Hollywood movie.
Building on work done by physicist Amos Ori two decades prior, and armed with her strong computational skills, Mallary built a computer model that would capture most of the essential physical effects on a spacecraft, or any large object, falling into a large, rotating black hole like Sagittarius A*.
The fictional Miller’s planet orbiting the black hole Gargantua, in the movie ‘Interstellar.’ interstellarfilm.wikia.com
Not even a bumpy ride?
What she discovered is that under all conditions an object falling into a rotating black hole would not experience infinitely large effects upon passage through the hole’s so-called inner horizon singularity. This is the singularity that an object entering a rotating black hole cannot maneuver around or avoid. Not only that, under the right circumstances, these effects may be negligibly small, allowing for a rather comfortable passage through the singularity. In fact, there may no noticeable effects on the falling object at all. This increases the feasibility of using large, rotating black holes as portals for hyperspace travel.
Mallary also discovered a feature that was not fully appreciated before: the fact that the effects of the singularity in the context of a rotating black hole would result in rapidly increasing cycles of stretching and squeezing on the spacecraft. But for very large black holes like Gargantua, the strength of this effect would be very small. So, the spacecraft and any individuals on board would not detect it.
This graph depicts the physical strain on the spacecraft’s steel frame as it plummets into a rotating black hole. The inset shows a detailed zoom-in for very late times. The important thing to note is that the strain increases dramatically close to the black hole, but does not grow indefinitely. Therefore, the spacecraft and its inhabitants may survive the journey. Khanna/UMassD
The crucial point is that these effects do not increase without bound; in fact, they stay finite, even though the stresses on the spacecraft tend to grow indefinitely as it approaches the black hole.
There are a few important simplifying assumptions and resulting caveats in the context of Mallary’s model. The main assumption is that the black hole under consideration is completely isolated and thus not subject to constant disturbances by a source such as another star in its vicinity or even any falling radiation. While this assumption allows important simplifications, it is worth noting that most black holes are surrounded by cosmic material – dust, gas, radiation.
Therefore, a natural extension of Mallary’s work would be to perform a similar study in the context of a more realistic astrophysical black hole.
Mallary’s approach of using a computer simulation to examine the effects of a black hole on an object is very common in the field of black hole physics. Needless to say, we do not have the capability of performing real experiments in or near black holes yet, so scientists resort to theory and simulations to develop an understanding, by making predictions and new discoveries.
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