пятница, 31 января 2020 г.

'Doomsday Clock' closer to midnight than ever


The Doomsday Clock on Thursday ticked down to 100 seconds to midnight, symbolizing the greatest level of peril to humanity since its creation in 1947 as the threat posed by climate change and a growing nuclear race loomed large.

'Doomsday Clock' closer to midnight than ever
"We are now expressing how close the world is to catastrophe in seconds – not hours, or even minutes," said
Rachel Bronson, president of the Bulletin of the Atomic Scientists in announcing the change
[Credit: Carolyn Kaster/Associated Press]
The danger level was compounded by information warfare and disruptive technologies ranging from deepfake video and audio to the militarization of space and the development of hypersonic weapons.

"We are now expressing how close the world is to catastrophe in seconds—not hours, or even minutes," said Rachel Bronson, president of the Bulletin of the Atomic Scientists, in announcing the change.

The decision on the clock is taken by panels of experts, including 13 Nobel laureates. It was originally set at seven minutes to midnight, and the previous worst—two minutes to midnight—held from 2018 to 2019 as well as 1953. The furthest it has ever been is 17 minutes, following the end of the Cold War in 1991.


On the nuclear front, the arms control boundaries that helped prevent catastrophe over the last half century are being dismantled and may be gone by next year, said subject expert Sharon Squassoni.

This includes the demise in 2019 of the Intermediate-Range Nuclear Forces (INF) Treaty, with the US and Russia entering a new competition to deploy once banned weapons. The US has suggested it won't extend New START, an arms reduction treaty signed in 2010.

"This year could see not just the complete collapse of the Iran nuclear deal," added Squassoni, with Tehran boosting its enrichment efforts.

And despite initial hopes US President Donald Trump's unorthodox approach to North Korea may produce results, no real progress ensued, said Squassoni, with Pyongyang instead vowing to press ahead with a new strategic weapon.

'Doomsday Clock' closer to midnight than ever
The Doomsday Clock on Thursday ticked down to 100 seconds to midnight
[Credit: Iris Royer De Vericourt/AFP]
On climate, two major UN summits fell dismally short of the action required to limit long-term warming to the goals laid out by the Paris Agreement that scientists say is necessary to prevent catastrophe.

The effects were already apparent in the record-breaking heat waves and floods India faced in 2019, and the wildfires that raged from the Arctic to Australia.

"If humankind pushes the climate into the opposite of an ice age," said Sivan Kartha, a scientist at the Stockholm Environmental Institute, "we have no reason to be confident that such a world will remain hospitable to human civilization."

Yet the experts took heart in mounting climate activism spearheaded by a youth movement that is spurring some governments to action.


Misinformation campaigns and fake news catalyzed by deepfake videos are potent threats to social cohesion, while the rise of AI weapons like drones that attack targets without human supervision create new uncertainty.

Russia meanwhile has announced a new hypersonic glide missile and the US is testing its own weapons that severely limit response times of targeted nations.

Space, long an arena for international cooperation, is also becoming increasingly militarized with multiple countries testing projectile and laser anti-satellite weapons and the US creating a new military branch, the Space Force.

"We ask world leaders to join us in 2020 as we work to pull humanity back from the brink," said Mary Robinson, chair of The Elders leadership group and former president of Ireland.

"Now is the time to come together—to unite and to act."

Source: AFP [January 23, 2020]



* This article was originally published here

Finely tuned nervous systems allowed birds and mammals to adopt smoother strides


Since the 1900s, neuroscientists have known that the peripheral nervous systems of tetrapods (four-footed animals) vary greatly, but how these differences affect the way that animals walk, run, or move has not been well understood. Now, a study published in the Journal of Experimental Biology, authored by a New York Institute of Technology anatomy professor, suggests that neuromuscular adaptations in mammals and birds may have allowed them to become more nimble than reptiles and amphibians.

Finely tuned nervous systems allowed birds and mammals to adopt smoother strides
Golgi tendon organs in reptiles and amphibians vs. birds and mammals
[Credit: Michael Granatosky]
"This research could explain why tigers have a much smoother walk than crocodiles, which lumber and drag their abdomens, and perhaps one reason why today's humans have evolved to walk with such uniform steps," says lead author Michael Granatosky, Ph.D., assistant professor of Anatomy at New York Institute of Technology College of Osteopathic Medicine (NYITCOM).


Tetrapods have small receptors in their muscles called Golgi tendon organs, which protect muscles from forces during locomotion (walking) and other physical activity. When muscle tension becomes dangerous, these receptors signal the nervous system to produce reflexes that release tension and prevent injury.

Amphibians and reptiles, which diverged from early tetrapods before mammals and birds, have freeform Golgi tendons located further from the muscle-tendon junction, suggesting that they detect stress across the entire muscle. In contrast, birds and mammals have encapsulated Golgi tendon organs set directly at the muscle-tendon junction, signifying an ability to detect tension in precise muscle areas, which would allow for more controlled motion. Now, researchers pose that birds and mammals owe their agile strides to these finely tuned receptors.

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Lordenshaw Hill Prehistoric Rock Art (Main Panel), Northumberland, 25.1.20.

Lordenshaw Hill Prehistoric Rock Art (Main Panel), Northumberland, 25.1.20.



* This article was originally published here

Hidden past of Earth's oldest continents unearthed


New international research led by the University of St Andrews presents a novel way to understand the structure and formation of our oldest continents.

Hidden past of Earth's oldest continents unearthed
Credit: University of St Andrews
The research, published in the journal Earth and Planetary Science Letters reveals how the team from St Andrews, Greenland, Australia, Denmark, and Canada, used magmatic rocks, sourced from deep within the Earth, to sample the interior of cratons as a means to understand how they were formed.


Cratons are the ancient, stable, heart of the Earth's continents, and their formation was a prerequisite for the evolution of complex life. The North Atlantic Craton extends from Northern Scotland through Greenland to North America, and contains the oldest crust known on Earth—up to 3.8 billion years old. How these ancient cratons were built is a major scientific debate, informing on one of the most fundamental questions in Earth science: when did plate tectonics begin operating?

Plate tectonics—the cycle of rigid tectonic plates in constant horizontal motion across the surface of the planet—makes Earth unique within the rocky planets of the solar system. Plate tectonics started at some point after the Earth formed 4.6 billion years ago, but it is unclear exactly when. Some scientists believe craton formation occurred as a result of plate tectonics, whereby they were assembled via horizontal stacking of crust. Others believe cratons were formed through non-plate tectonic processes, growing via so-called "vertical tectonics."

Hidden past of Earth's oldest continents unearthed
Credit: University of St Andrews
The ability to understand the architecture of cratons and therefore how and when they were formed is, however, problematic, due to the difficulty in sampling rocks from within the deep crust and mantle, which in West Greenland is up to 250 km thick.


To address this, the research team used deep-sourced magmatic rocks known as kimberlites to sample the deep parts of the North Atlantic Craton. Kimberlites, which are famous for bringing diamonds to the surface, originate from the upper mantle, more than 100 km below Earth's surface. As they ascend through the craton, their magma collects pieces of crust along the way, pieces that are hidden at the surface. In this way, kimberlites can sample parts of the deep continent that are otherwise inaccessible.

The researchers sampled a kimberlite from the coast of West Greenland, near Maniitsoq, and extracted from it microscopic zircon grains, each less than the width of a human hair, originating from crust deep within the craton. The team analysed these grains using high-precision laser ablation mass spectrometry.

Hidden past of Earth's oldest continents unearthed
Credit: University of St Andrews
Analysis revealed the age and chemistry of the zircon grains, which suggested that beneath the 3.0 billion-years old crust which today forms the Maniitsoq region, lies much older 3.8 billion-year-old crust. This older crust is today only found at the surface 150 km south of the kimberlite locality. Therefore, for it to have been sampled by the kimberlite, parts of it must have been transported laterally beneath the crust that is now at the surface, sometime after 3.0 billion years ago.

Lead scientist Dr. Nick Gardiner of the School of Earth and Environmental Sciences, University of St Andrews, said: "The kimberlite sample offers up these ancient zircon grains which imply the North Atlantic Craton was assembled by horizontally stacking different-aged slices of continental crust, likely in the late Archaean Eon after 3.0 billion years ago. These findings imply some cratons were formed through plate tectonic processes."

Source: University of St Andrews [January 27, 2020]



* This article was originally published here

2020 January 31 Goldilocks Zones and Stars Infographic Credit:...



2020 January 31

Goldilocks Zones and Stars
Infographic Credit: NASA ESA, Z. Levy (STScI)

Explanation: The Goldilocks zone is the habitable zone around a star where it’s not too hot and not too cold for liquid water to exist on the surface of orbiting planets. This intriguing infographic includes relative sizes of those zones for yellow G stars like the Sun, along with orange K dwarf stars and red M dwarf stars, both cooler and fainter than the Sun. M stars (top) have small, close-in Goldilocks zones. They are also seen to live long (100 billion years or so) and are very abundant, making up about 73 percent of the stars in the Milky Way. Still, they have very active magnetic fields and may produce too much radiation harmful to life, with an estimated X-ray irradiance 400 times the quiet Sun. Sun-like G stars (bottom) have large Goldilocks zones and are relatively calm, with low amounts of harmful radiation. But they only account for 6 percent of Milky Way stars and are much shorter lived. In the search for habitable planets, K dwarf stars could be just right, though. Not too rare they have 40 billion year lifetimes, much longer than the Sun. With a relatively wide habitable zone they produce only modest amounts of harmful radiation. These Goldilocks stars account for about 13 percent of the stars of the Milky Way.

∞ Source: apod.nasa.gov/apod/ap200131.html



* This article was originally published here

Lordenshaw Hill Iron Age Hill Fort, Lordenshaw, Northumberland, 25.1.20.

Lordenshaw Hill Iron Age Hill Fort, Lordenshaw, Northumberland, 25.1.20.



* This article was originally published here

Early North Americans may have been more diverse than previously suspected


Ancient skulls from the cave systems at Tulum, Mexico suggest that the earliest populations of North America may have already had a high level of morphological diversity, according to a study published in the open-access journal PLOS ONE by Mark Hubbe from Ohio State University, USA, Alejandro Terrazas Mata from Universidad Nacional Autónoma de México, Mexico, and colleagues.

Early North Americans may have been more diverse than previously suspected
Original position of the skeletal remains inside submerged cave of Muknal
[Credit: Jerónimo Avilés]
Debate about the origins of the earliest humans in the Americas has relied on relatively little data, in part due to the rarity of early human remains in North America.

The coastal, mostly-flooded limestone cave system in the city of Tulum in the Mexican state of Quintana Roo encompasses at least eight different sites with ancient human remains (approximately 13-8 kya).


After dating and scanning four relatively well-preserved skulls retrieved from different sites within this cave network, Hubbe and colleagues used craniofacial morphology to compare these skulls with a reference dataset of worldwide modern human populations.

The authors found unexpectedly high diversity among the skulls. While the oldest skull showed close morphological associations with modern arctic North Americans in Greenland and Alaska, the second-oldest skull demonstrated strong affinities with modern European populations--a new finding for early American remains using this type of reference comparison.

Of the two remaining skulls, one appeared to show associations with Asian and Native American groups, while the other showed associations to arctic populations in addition to having some modern South American features.


These findings are surprising considering that previous studies have not shown this level of diversity: earlier work on South American remains has instead found consistent associations with modern Australo-Melanesian and African groups, and with Late Pleistocene specimens found in Europe and Asia.

The authors posit that early North American colonizers may have been highly diverse, but that diversity reduced when some populations dispersed into South America. This study underscores the need to pursue new archaeological evidence across the continent to build more robust models of early diversity, migration and dispersal across the Americas.

The authors add: "Four ancient skulls discovered in the submerged caves of Quintana Roo, Mexico, show that Early Americans had high biological diversity since the initial occupation of the continent."

Source: Public Library of Science [January 29, 2020]



* This article was originally published here

Lordenshaw Hill Prehistoric Rock Art (Channel Rock), Lordenshaws, Northumberland, 25.1.20.

Lordenshaw Hill Prehistoric Rock Art (Channel Rock), Lordenshaws, Northumberland, 25.1.20.



* This article was originally published here

The 'firewalkers' of Karoo: Dinosaurs and other animals left tracks in a 'land of fire'


In southern Africa, dinosaurs and synapsids, a group of animals that includes mammals and their closest fossil relatives, survived in a "land of fire" at the start of an Early Jurassic mass extinction, according to a study published in the open-access journal PLOS ONE by Emese M. Bordy of the University of Cape Town and colleagues.

The 'firewalkers' of Karoo: Dinosaurs and other animals left tracks in a 'land of fire'
Palaeoenvironmental reconstruction of the Highlands ichnosite at the Pliensbachian-Toarcian boundary
[Credit: Bordy et al, 2020]
The Karoo Basin of southern Africa is well-known for its massive deposits of igneous rocks left behind by extensive basaltic lava flows during the Early Jurassic. At this time, intense volcanic activity is thought to have had dramatic impacts on the local environment and global atmosphere, coincident with a worldwide mass extinction recorded in the fossil record. The fossils of the Karoo Basin thus have a lot to tell about how ecosystems responded to these environmental stresses.


In this study, Bordy and colleagues describe and identify footprints preserved in a sandstone layer deposited between lava flows, dated to 183 million years ago. In total, they report five trackways containing a total of 25 footprints, representing three types of animals: 1) potentially small synapsids, a group of animals that includes mammals and their forerunners; 2) large, bipedal, likely carnivorous dinosaurs; and 3) small, quadrupedal, likely herbivorous dinosaurs represented by a new ichnospecies (trace fossils like footprints receive their own taxonomic designations, known as ichnospecies).

These fossils represent some of the very last animals known to have inhabited the main Karoo Basin before it was overwhelmed by lava. Since the sandstone preserving these footprints was deposited between lava flows, this indicates that a variety of animals survived in the area even after volcanic activity had begun and the region was transformed into a "land of fire."


The authors suggest that further research to uncover more fossils and refine the dating of local rock layers has the potential to provide invaluable data on how local ecosystems responded to intense environmental stress at the onset of a global mass extinction.

Bordy adds: "The fossil footprints were discovered within a thick pile of ancient basaltic lava flows that are ~183 million years old. The fossil tracks tell a story from our deep past on how continental ecosystems could co-exist with truly giant volcanic events that can only be studied from the geological record, because they do not have modern equivalents, although they can occur in the future of the Earth."

Source: Public Library of Science [January 29, 2020]



* This article was originally published here

The cosmic cow explained - radio signals point to an explosion and a newborn magnetar

Artist's impression of the cosmic cow
Credit: Shanghai Astronomical Observatory, China

Observations using 21 telescopes of the European VLBI Network (EVN) have revealed that a cosmic explosion, called AT2018cow most likely formed a neutron star with an extremely powerful magnetic field - known as a magnetar. The high-resolution radio images produced in this new study show physical properties of the stellar remnant that make alternative explanations less likely, say scientists.

Among short-lived sky phenomena, AT2018cow (The Cow) is an astronomical event like no other. First detected in 2018, it received its memorable name by chance according to alphabetical protocol to classify such events. However, it was not just its name that makes it memorable. AT2018cow was identified in a relatively nearby galaxy (about 200 million light years away). Its proximity, exceptionally brief brightness and unusually high temperature led to widespread attention upon discovery.

Originally discovered with optical telescopes, follow up observations were conducted across wavelengths from X-ray to radio. These observations indicated that there is a ‘central engine' which powered the event. This resulted in theories that the mysterious source could be a supernova - a star whose central core collapsed - or a Tidal Disruption Event (TDE), where a white dwarf star is being ripped apart as it approaches a massive black hole.

In the current study, an international team was led by Prashanth Mohan, astronomer at the Shanghai Astronomical Observatory, China.

"Both these theories suggested that the observed central engine would produce relativistic jets - a high energy expulsion of material. These jets, when aligned with our line of sight, would appear much brighter as ionised matter is accelerated close to the speed of light, and could be responsible for the exceptional brightness of the event. With a network of radio telescopes, we decided to test whether that was the case", explains Tao An.

The team monitored the radio afterglow to search for a relativistic jet from the Cow. They conducted five observations over the course of a year, using a total of 21 telescopes from the European VLBI Network (EVN). The high-resolution radio imaging provided by the EVN, led the team to a surprising conclusion: there was no sign of a relativistic jet.

"These most detailed images in the radio regime do not show any relativistic motion or expansion during this time period. That argues against a jet in the Cow, at least later in its evolution. Instead it seems that the Cow was intrinsically bright and originated from a star exploding as a supernova", says Jun Yang, astronomer at Onsala Space Observatory, Chalmers University of Technology in Sweden.

Further, the astronomers' observations reveal physical conditions that can only be explained by the presence of a neutron star with extremely strong magnetic fields (a magnetar), which was born in the explosion. "We see signs that material from the explosion expanded into a dense, magnetized environment. The way the radio signals faded is just what we might expect if the Cow's "central engine" is a magnetar which formed from the collapse of a star's core" says Prashanth Mohan.

Such characteristics point to another intriguing possibility, the scientists suggest. Interaction of a magnetar with its strongly magnetized environment around it might also produce short enigmatic phenomena known as Fast Radio Bursts (FRBs).

"The EVN is the most sensitive standalone VLBI network in the world that has delivered cutting edge results in the field of transient science. It has by now provided the most accurate localizations of two FRBs. There is an intriguing possibility that there may be a link between FRBs and other type of transient sources (like the event that produced 2018ATcow), but this requires further studies", concludes Zsolt Paragi from the Joint Institute for VLBI ERIC (JIVE).




Publication link

Prashanth Mohan, Tao An, and Jun Yang. The Nearby Luminous Transient AT2018cow: A Magnetar Formed in a Subrelativistically Expanding Nonjetted Explosion. 2020, ApJL, 888, 24 https://iopscience.iop.org/article/10.3847/2041-8213/ab64d1



Contact

Assist. Prof. Prashanth Mohan - lead author
Shanghai Astronomical Observatory, China
Email: pmohan@shao.ac.cn

Prof. Tao An - author
Shanghai Astronomical Observatory, China
Email: antao@shao.ac.cn

Dr. Jun Yang - author
Onsala Space Observatory, Sweden
Email: jun.yang@chalmers.se

Zsolt Paragi - EVN contact
The Joint Institute for VLBI ERIC (JIVE), the Netherlands
Email: paragi@jive.eu
Phone: +31 521 596 536



Additional information

Observations were conducted with the European Very Long Baseline Interferometry Network (EVN). The EVN is the most sensitive Very Long Baseline Interferometry (VLBI) array in the world, which allows researchers to conduct unique, high-resolution, radio astronomical observations of cosmic radio sources. Data from the EVN is processed at the Joint Institute for VLBI ERIC (JIVE) - an international research infrastructure based in the Netherlands, which also provides support, conducts leading research and forwards technical development in the field of radio astronomy.

A total of 21 antennas from the EVN were involved in these observations: 300 m Arecibo, (USA), 32 m Badary (Russia), 32 m Cambridge (UK), 25 m Defford (UK), 100 m Effelsberg (Germany) 26 m Hartebeesthoek (South Africa), 32 m Irbene (Latvia), 16 m Irbene (Latvia), 76 m Lovell (UK), 40 m Kunming (China), 25 m Knockin (UK), 25 m Medicina (Italy), 25 m Onsala (Sweden), 64 m Sardinia (Italy), 32 m Svetloe (Russia), 65 m Tianma (China), 32 m Torun (Poland), 26 m Urumqi (China), 25 m Westerbork (Netherlands), 40 m Yebes (Spain), 32 m Zelenchukskaya (Russia).




* This article was originally published here

Lordenshaw Hill Bronze Age Cairn, Lordenshaws, Northumberland, 25.1.20.

Lordenshaw Hill Bronze Age Cairn, Lordenshaws, Northumberland, 25.1.20.



* This article was originally published here

New predatory dinosaur added to Australia's prehistory


Evidence of agile, carnivorous two-legged dinosaurs known as noasaurids have been found across the now dispersed land masses that once formed the ancient southern supercontinent of Gondwana, but never in Australia—until now.

New predatory dinosaur added to Australia's prehistory
The Lightning Ridge noasaurid bone in approximate life position,
with a human for scale [Credit: Tom Brougham]
Researchers identified a single neck bone found in an opal mine near the outback town of Lightning Ridge, New South Wales, as belonging to a noasaurid, and then realised that another fossil discovered in 2012 along the south coast of Victoria was from the same group.

Noasaurid are a rare group of theropod dinosaurs—two legged carnivores—that lived in the middle to late Cretaceous Period, between about 120 and 66 million years ago. Noasaurids were small-bodied dinosaurs, many with peculiar facial features, typically less than two metres long and weighing about 20 kilograms.


The recognition of this new group of dinosaurs in Australia by palaeontologists from the Palaeoscience Research Centre at the University of New England and the Australian Opal Centre in Lightning Ridge adds a missing piece to a puzzle.

"It was assumed that noasaurids must have lived in Australia because their fossils have been found on other southern continents that, like Australia, were once part of the Gondwanan supercontinent," said lead scientist, Dr. Tom Brougham of the Palaeoscience Research Centre. "These recent fossil finds demonstrate for the first time that noasaurids once roamed across Australia. Discoveries of theropods are rare in Australia, so every little find we make reveals important details about our unique dinosaur fauna."

The researchers compared the 100 million-year-old Lightning Ridge neck bone with those from other carnivorous dinosaurs and quickly realised it was different from anything that had been found in Australia to date. "When we looked at what features this bone has compared to those of other theropods, we found that it matched closely with this strange group of dinosaurs called noasaurids," Dr. Brougham said.


"This prompted us to re-examine an ankle bone of a dinosaur that was discovered in Victoria in 2012, about 20 million years older than the Lightning Ridge bone, and using the same methods we concluded that this also belonged to a noasaurid. In addition, this ankle bone is approximately the same age, or perhaps even older, than the oldest known noasaurids, which come from South America."

Noasaurids were similar in size to, and lived at the same time as, a more well-known group of carnivorous dinosaurs called dromaeosaurids or 'raptors'—infamously represented by Velociraptor in Jurassic Park—and were probably also active predators. However, while Velociraptor and kin have representatives from all over the world, noasaurids were known only from several of the southern continents (South America, Africa, Madagascar and India), which formed the supercontinent of Gondwana before it started breaking apart in the Cretaceous.

The study was published today in the journal Scientific Reports.

Source: University of New England [January 29, 2020]



* This article was originally published here

Prehistoric Rock Art Fragments, The Great North Museum, Hancock, Newcastle upon Tyne, 26.1.20.

Prehistoric Rock Art Fragments, The Great North Museum, Hancock, Newcastle upon Tyne, 26.1.20.



* This article was originally published here

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