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  • richardmitnick 1:18 pm on December 13, 2018 Permalink | Reply
    Tags: Science News, , The Parker Solar Probe takes its first up-close look at the sun   

    From Science News: “The Parker Solar Probe takes its first up-close look at the sun” 

    From Science News

    December 12, 2018
    Lisa Grossman

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    The spacecraft broke speed and distance records on its initial solar flyby.

    1
    FIRST LOOK One of the first images NASA’s Parker Solar Probe took during its close encounter with the sun shows a streamer of plasma in the outer solar atmosphere, or corona. The probe took this image November 8 at a distance of about 27 million kilometers from the sun’s surface. The bright dot below the streamer is Jupiter. Parker Solar Probe/NASA and Naval Research Laboratory

    NASA’s Parker Solar Probe has met the sun and lived to tell the tale.

    The sun-grazing spacecraft has already broken the records for the fastest space probe and the nearest brush any spacecraft has made with the sun. Now the probe is sending data back from its close solar encounter, scientists reported December 12 at the American Geophysical Union meeting in Washington, D.C.

    “What we are looking at now is completely brand new,” solar physicist Nour Raouafi of Johns Hopkins University Applied Physics Lab in Laurel, Md., said at a news conference. “Nobody looked at this before.”

    Parker launched August 12 (SN Online: 8/12/18) and will make 24 close passes by the sun over the next seven years, eventually going to within about 6 million kilometers of the sun’s surface (SN: 7/21/18, p. 12). The spacecraft made its first close flyby November 6, swooping to within roughly 24 million kilometers of the solar surface. That’s about twice as close to the sun as the previous closest spacecraft, the Helios spacecraft in the 1970s. At peak speed, Parker was racing at about 375,000 kilometers per hour, roughly twice Helios’ speed.

    But because the probe was on the opposite side of the sun from Earth during the flyby, Parker didn’t start relaying its observations until December 7.

    After the probe emerged from behind the sun, the Parker team got its first up-close look at the wispy outer solar atmosphere, called the corona. One of the first images from Parker’s camera shows unprecedented detail in a solar streamer, a filament of plasma in the corona. The team hopes that Parker’s data will help solve the mystery of why the corona is about 300 times as hot as the sun’s surface (SN Online: 8/20/17).

    Only about one-fifth of the data recorded during Parker’s initial flyby will reach scientists before the sun gets between Earth and the spacecraft again. The rest of the data will be downlinked next year, between March and May. Scientists hope to start publishing results soon after.

    “If you ask any scientist in the team or even outside what to expect, I think the answer would be, we don’t really know,” Raouafi said. “We are almost certain we’ll make new discoveries.”

    See the full article here .


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  • richardmitnick 10:45 am on December 6, 2018 Permalink | Reply
    Tags: , , , , , , , NASA/ESA Cosmic Origins Spectrograph, Science News, The ecosystem that controls a galaxy’s future is coming into focus   

    From Science News: “The ecosystem that controls a galaxy’s future is coming into focus” 

    From Science News

    July 12, 2018
    Lisa Grossman

    The circumgalactic medium has been hard to observe, but new tools now make it possible.

    1
    COSMIC CLOAK Whirls of cold and hot gas billow in this simulation of a circumgalactic medium surrounding a galaxy. With new tools and simulations, researchers have learned that the CGM helps a galaxy recycle its materials. M.S. Peeples et al/FOGGIE Project

    There’s more to a galaxy than meets the eye. Galaxies’ bright stars seem to spiral serenely against the dark backdrop of space. But a more careful look reveals a whole lot of mayhem.

    “Galaxies are just like you and me,” Jessica Werk, an astronomer at the University of Washington in Seattle, said in January at a meeting of the American Astronomical Society. “They live their lives in a constant state of turmoil.”

    Much of that turmoil takes place in a huge, complicated setting called the circumgalactic medium, or CGM. This vast, roiling cloud of dust and gas is a galaxy’s fuel source, waste dump and recycling center all in one [Annual Review of Astronomy and Astrophysics]. Astronomers think the answers to some of the most pressing galactic mysteries — how galaxies keep forming new stars for billions of years, why star formation abruptly stops — are hidden in a galaxy’s enveloping CGM.

    “To understand the galaxies, you have to understand the ecosystem that they’re in,” says astronomer Molly Peeples of the Space Telescope Science Institute in Baltimore.

    Yet this galactic atmosphere is so diffuse that it’s invisible — a liter of CGM contains just a single atom. It has taken almost 60 years and an upgrade to the Hubble Space Telescope just to begin probing distant CGMs and figuring out how their constant churning can make or break galaxies.

    “Only recently have we been able to really, truly, observationally characterize the relationship between this gaseous cycle and the properties of the galaxy itself,” Werk says.

    Armed with the first extragalactic census, astronomers are now piecing together how a CGM controls its galaxy’s life and death. And new theoretical studies hint that galaxies’ stars would be arranged very differently without a medium’s frenetic flows. Plus, new observations show that some CGMs are surprisingly lumpy [Nature]. A better understanding of CGMs, enabled by new telescopes and computer simulations, could change how scientists think about everything from galaxy collisions to the origins of our own atoms.

    “The CGM is the part of the iceberg that’s under the water,” says astrophysicist Kevin Schawinski of ETH Zurich, who studies the more conventional parts of galaxies. “We now have good measurements where we’re sure it’s important.”

    _______________________________________________
    Frenetic fog

    Researchers use a bright source of background light, like a quasar, to learn about a galaxy’s circumgalactic medium, a diffuse cloud of gas and metals (pink in the illustration) surrounding a galaxy. Gas is recycled between the galaxy and the CGM.

    2
    Sources: J. Tumlinson, M.S. Peeples and J.K. Werk/Annual Review of Astronomy and Astrophysics 2017; M.S. Peeples/Nature 2015
    _______________________________________________

    Waiting for Hubble

    That 2009 Hubble telescope upgrade, which made the CGM census possible, almost didn’t happen.

    In a cosmic coincidence, the Hubble telescope’s chief champions were also the first astronomers to figure out how to observe a galaxy’s CGM. Lyman Spitzer of Princeton University and John Bahcall of the Institute for Advanced Study in Princeton, N.J., and other astronomers noticed something strange after the 1963 discovery of quasars [http://cosmology.carnegiescience.edu/timeline/1963] (SN Online: 3/21/14), bright beacons now known to be white-hot disks surrounding supermassive black holes in the centers of distant galaxies.

    Everywhere astronomers looked, quasars’ spectra — the rainbow created when their light is spread out over all wavelengths — were notched with dark holes. Some wavelengths of light weren’t getting through.

    In 1969, Spitzer and Bahcall realized what was going on: The missing light was absorbed by gas at the edges of galaxies, the same stuff that would later be called the CGM. Astronomers had been peering at quasars shining through CGMs like headlights through a fog.

    Not much more could be done at the time, though. Earth’s atmosphere also absorbs light in those same wavelengths, making it difficult to tell which light-blocking atoms were in a galaxy’s CGM and which came from closer to home. Knowing that a CGM was there was one thing; taking its measurements would require something extra.

    Spitzer and Bahcall knew what they needed: a space telescope that could observe from outside Earth’s atmosphere. The pair were two of the most vocal and consistent champions of the Hubble Space Telescope, which launched in 1990. Spitzer’s colleagues called him Hubble’s “intellectual and political father.”

    Bahcall never stopped advocating for Hubble. In February 2005, six months before his death at age 70 from a rare blood disorder, he co-wrote an article in the Los Angeles Times [http://articles.latimes.com/2005/feb/23/opinion/oe-tayloretal23] urging Congress to restore funding for a mission to fix some aging Hubble instruments, which NASA had canceled after the 2003 Columbia space shuttle disaster.

    “What is at stake is not only a piece of stellar technology but our commitment to the most fundamental human quest: understanding the cosmos,” Bahcall and colleagues wrote. “Hubble’s most important discoveries could be in the future.”

    His plea was answered: The space shuttle Atlantis brought astronauts to repair Hubble for the last time in May 2009 (SN Online: 5/19/09). During the repair, the astronauts installed the Cosmic Origins Spectrograph, which could pick up diffuse CGM gas with 30 times the sensitivity of any previous instrument.

    NASA Hubble Cosmic Origins Spectrograph

    Although earlier spectrographs on Hubble had picked out CGMs a few quasar-beams at a time, the new device let astronomers search around dozens of galaxies, using the light of even dimmer quasars.

    “It blew the field wide open,” Werk says.

    4
    Gas flows out from Messier 82, the Cigar galaxy, to its invisible circumgalactic medium in this Hubble image. NASA, ESA, Hubble Heritage Team

    The circumgalactic census

    A team led by Jason Tumlinson of Baltimore’s Space Telescope Science Institute, Hubble’s academic home, made a catalog of 44 galaxies with a quasar sitting behind them from Hubble’s perspective. In a 2011 paper in Science, the researchers reported that every time they looked within 490,000 light-years of a galaxy, they saw spectra dappled with blank spots from atoms absorbing light. That meant that CGMs weren’t odd cloaks worn by just a few galaxies. They were everywhere.

    Tumlinson’s team spent the first few years after Hubble’s upgrade like 19th century naturalists describing new species. The group measured the mass and the chemical makeup of the galaxies’ CGMs and found they were huge cisterns of heavy elements. CGMs contain 10 million times the mass of the sun in oxygen alone. In many cases, the mass of a CGM is comparable to the mass of the entire visible part of its galaxy.

    The finding offers an answer to a long-standing cosmic mystery: How do galaxies have enough star-forming fuel to keep going for billions of years? Galaxies build stars from collapsing clouds of cool gas at a constant rate; the Milky Way, for example, makes one to two solar masses’ worth of stars every year. But there isn’t enough cool gas within the visible part of a galaxy, the disk containing its stars, to support observed rates of star formation.

    “We think that gas probably comes from the CGM,” Werk says. “But exactly how that gas is getting into galaxies, where it gets in, the timescale on which it gets in, are there things that prevent it from getting in? Those are big questions that keep us all awake at night.”

    Werk and Peeples realized that all that mass could help solve two other cosmic bookkeeping problems. All elements heavier than helium (which astronomers lump together as “metals”) are forged by nuclear fusion in the hearts of stars. When stars use up their fuel and explode as supernovas, they scatter those metals around to be folded into the next generation of stars.

    But if you add up all the metals in the stars, gas and dust in a given galaxy’s disk, it’s not enough to account for all the metals the galaxy has ever made. The mismatch gets even worse if you include the hydrogen, helium, electrons and protons — basically all the ordinary matter that should have collected in the galaxy since the Big Bang. Astronomers call all those bits baryons. Galaxies seem to be missing 70 to 95 percent of that stuff.

    So Peeples and Werk led a comprehensive effort to tally all the ordinary matter in about 40 galaxies observed with Hubble’s new spectrometer. The researchers published the results in two 2014 papers in The Astrophysical Journal.

    At the time, Werk reported that at least half of galaxies’ missing ordinary matter can be accounted for in their CGMs. In a 2017 update, Werk and colleagues found that the mass of baryons just in the form of cool gas in a galaxy’s CGM could be nearly 90 billion solar masses [The Astrophysical Journal]. “Obviously, this mass could resolve the galactic missing baryons problem,” the team wrote.

    “It’s a classic science story,” Schawinski says. The researchers had a hypothesis about where the missing material should be and made predictions. The group made observations to test those predictions and found what it sought.

    In a separate study, Peeples showed that although metals are born in galaxies’ starry disks, those metals don’t stay there. Only 20 to 25 percent of the metals a galaxy has ever produced remains in the stars, gas and dust in the disk, where the metals can be incorporated into new stars and planets. The rest probably ends up in the CGM.

    “If you look at all the metals the galaxies ever produced in their whole lifetime, more of them are outside the galaxy than are still inside the galaxy,” Tumlinson says, “which was a huge shock.”

    Recycling centers

    So how did the metals get into the CGM? Quasars’ spectra couldn’t help with that question. Their light shows only a slice through a single galaxy at a single moment in time. But astronomers can track galaxies’ growth and development with computer simulations based on physical rules for how stars and gas behave.

    This strategy revealed the churning, ever-changing nature of gas in galaxies’ CGMs. Simulations such as EAGLE, or Evolution and Assembly of GaLaxies and their Environments, which is run out of Leiden University in the Netherlands, showed that metals can reach CGMs through stars’ violent lives: in powerful winds of radiation blowing away from massive young stars, and in the death throes of supernovas spraying metals far and wide.

    5
    This EAGLE simulation shows that, over time, metals (colors) move away from the center of a galaxy to the circumgalactic medium. J. Tumlinson, M.S. Peeples and J.K. Werk/Annual Review of Astronomy and Astrophysics 2017

    Once the metals are in the CGM, though, they don’t always stay put. In simulations, galaxies seem to use the same gas over and over again.

    “It’s basically just gravity,” Peeples says. “Throw a baseball up, and it’ll come back to the ground.” The same goes for gas flowing out of galaxies: Unless the gas travels fast enough to escape the galaxy’s gravity altogether, those atoms will eventually fall back into the disk — and form new stars.

    Some simulations show discrete gas parcels making the trip from a galaxy’s disk out into the CGM and back again several times. Together, CGMs and their galaxies are giant recycling devices.

    That means that the atoms that make up planets, plants and people may have taken several trips to circumgalactic space before becoming part of us. Over hundreds of millions of years, the atoms that eventually became part of you traveled hundreds of thousands of light-years.

    “This is my favorite thing,” Tumlinson says. “At some point, your carbon, your oxygen, your nitrogen, your iron was out in intergalactic space.”

    How galaxies die

    But not all galaxies get their CGM gas back. Losing the gas could shut off star formation in a galaxy for good. No one knows how star formation shuts off, or quenches. But the answer is probably in the CGM.

    Galaxies come in two main forms: young spiral galaxies that are making stars and old blobby galaxies where star formation is quenched (SN Online: 4/23/18).

    “How galaxies quench and why they stay that way is one of the most important questions in galaxy formation generally,” Tumlinson says. “It just has to have something to do with the gas supply.”

    _______________________________________________
    Reading what’s not there

    Using light from a quasar (QSO), researchers can “see” CGMs. In this example, spectra from two galaxies, G1 and G2, have certain wavelengths missing (red, in bottom boxes) where the CGM atoms are absorbing light.

    6
    _______________________________________________

    One possibility, suggested in a paper posted online February 20 in The Astrophysical Journal, is that sprays of supernova-heated gas could get stripped from galaxies. Physicist Chad Bustard of the University of Wisconsin–Madison and colleagues simulated the Large Magellanic Cloud, a satellite galaxy of the Milky Way, and found that the small galaxy’s outflowing gas was swept away by the slight pressure of the galaxy’s movement around the Milky Way.

    Alternatively, a dead galaxy’s CGM gas could be too hot to sink into the galaxy and form stars. If so, star-forming galaxies should have CGMs full of cold gas, and dead galaxies should be shrouded in hot gas. Hot gas would stay floating above the galactic disk like a hot air balloon, too buoyant to sink in and form stars.

    But Hubble saw the opposite. Star-forming galaxies had CGMs chock-full of oxygen-VI — meaning that the gas was so hot (a million degrees Celsius or more) that oxygen atoms lost five of their original electrons. Dead galaxies had surprisingly little oxygen-VI.

    “That was puzzling,” Tumlinson says. “If theory told us anything, it should have gone the other way.”

    In 2016, Benjamin Oppenheimer, a computational astrophysicist at the University of Colorado Boulder, suggested a solution: The “dead” galaxies didn’t lack oxygen at all. The gas was just too hot for Hubble to observe. “In fact, there is even more oxygen around those passive galaxies,” Oppenheimer says.

    All that hot gas could potentially explain why those galaxies died — except that these galaxies were full of star-forming cold gas, too.

    “The dead galaxies have plenty of fuel left in the tank,” Tumlinson says. “We don’t know why they’re not using it. Everybody’s chasing that problem.”

    Grabbing at the elephant

    The chase comes at a good time. Until recently, observers had no way to map a single galaxy’s CGM. Researchers have had to add up dozens of quasar beams to understand the composition of CGMs on average.

    “We’ve been like the three blind people grabbing at the elephant,” says John O’Meara, an observational astronomer at Saint Michael’s College in Colchester, Vt.

    Teams using two new spectrographs — KCWI, the Keck Cosmic Web Imager on the Keck telescope in Hawaii, and MUSE, the Multi Unit Spectroscopic Explorer on the Very Large Telescope in Chile — are racing to change that.

    Keck Cosmic Web Imager schematic

    Keck Cosmic Web Imager


    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level,

    ESO MUSE on the VLT on Yepun (UT4),

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    These instruments, called integral field spectrographs, can read spectra across a full galaxy all at once. Given enough background light, astronomers can now examine a single galaxy’s entire CGM. Finally, astronomers have a way to test theories of how gas circulates into and out of a galaxy.

    A Chilean team, led by astronomer Sebastian Lopez of the University of Chile in Santiago and colleagues, used MUSE to observe a small dim galaxy that happens to be sandwiched between a bright, distant galaxy and a massive galaxy cluster closer to Earth. The cluster acts as a gravitational lens, distorting the image of the distant galaxy into a long bright arc (SN: 3/10/12, p. 4). The light from that arc filtered through the CGM of the sandwiched galaxy, which the team called G1, at 56 different points.

    Surprisingly, G1’s CGM was lumpy, not smooth as expected, the team reported in the Feb. 22 Nature. “The assumption has been that that gas is distributed homogeneously around every system,” Lopez says. “This is not the case.”

    _______________________________________________
    MUSE makes a mark

    Light from a source galaxy is deflected and magnified by an intervening galaxy cluster to form the bright arc seen in the projected image at far right. Unlike a quasar’s narrow beam of light, the extensive arc lights up a large area of galaxy G1’s CGM, showing it is surprisingly lumpy.

    6
    _______________________________________________

    O’Meara is leading a group that is hot on Lopez’s trail. Last year, while KCWI was being installed, O’Meara got an hour of observing time and was able to see hydrogen — which is associated with cool, star-forming gas — in the CGM of another galaxy backlit by a bright lensed arc. He’s not ready to discuss the results in detail yet, but the team is submitting a paper to Science.

    Meanwhile, Peeples’ team is revisiting how computers render CGMs. “The resolution of the circumgalactic medium in simulations is, um, bad,” she says. Existing simulations are good at matching the visible properties of galaxies — their stars, the gas between the stars, and the overall shapes and sizes. But they “utterly fail at reproducing the properties of the circumgalactic medium,” she says.

    So she’s running a new set of simulations called FOGGIE, which focus on CGMs for the first time. “We’re finding that it changes everything,” she says: The shape, star formation history and even the orientation of the galaxy in space look different.

    Together, the new observations and simulations suggest that the CGM’s function in the life cycle of a galaxy has been underestimated. Theorists like Peeples and observers like O’Meara are working together to make new predictions about how the CGM should look. Then the researchers will check real galaxies to see if they match.

    “Molly will post a really amazing new render of a simulation on Slack, and I’ll go, ‘Holy crap, that looks weird!’ ” O’Meara says. “I’ll go scampering off to find a similar example in the data, and we get into this positive feedback loop of going ‘Holy crap! Holy crap!’ ”

    While future circumgalactic studies will focus on gathering spectra from full CGMs, Tumlinson is hoping to squeeze more information out of Hubble while he still can. Hubble made CGM studies possible, but the telescope is 28 years old, and probably has less than a decade left. Hubble’s spectrograph is still the best at observing certain atoms in CGMs to help reveal the gaseous halos’ secrets. “It’s something we definitely want to do,” he says, “before Hubble ends up in the ocean.”

    See the full article here .


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  • richardmitnick 9:42 am on December 2, 2018 Permalink | Reply
    Tags: , , Physicists finally calculated where the proton’s mass comes from, Science News   

    From Science News: “Physicists finally calculated where the proton’s mass comes from” 

    From Science News

    November 26, 2018
    Emily Conover

    Only 9 percent of the subatomic particle’s bulk comes from the mass of its quarks.

    1
    MASSIVE UNDERTAKING Using a technique called lattice QCD, scientists figured out how protons (illustrated here in the nucleus of an atom) get their mass.

    A proton’s mass is more than just the sum of its parts. And now scientists know just what accounts for the subatomic particle’s heft.

    Protons are made up of even smaller particles called quarks, so you might expect that simply adding up the quarks’ masses should give you the proton’s mass. However, that sum is much too small to explain the proton’s bulk. And new, detailed calculations show that only 9 percent of the proton’s heft comes from the mass of constituent quarks. The rest of the proton’s mass comes from complicated effects occurring inside the particle, researchers report in the Nov. 23 Physical Review Letters.

    Quarks get their masses from a process connected to the Higgs boson, an elementary particle first detected in 2012 (SN: 7/28/12, p. 5). But “the quark masses are tiny,” says study coauthor and theoretical physicist Keh-Fei Liu of the University of Kentucky in Lexington. So, for protons, the Higgs explanation falls short.

    Instead, most of the proton’s 938 million electron volts of mass is due to complexities of quantum chromodynamics, or QCD, the theory which accounts for the churning of particles within the proton. Making calculations with QCD is extremely difficult, so to study the proton’s properties theoretically, scientists rely on a technique called lattice QCD, in which space and time are broken up into a grid, upon which the quarks reside.

    Using this technique, physicists had previously calculated the proton’s mass (SN: 12/20/08, p. 13). But scientists hadn’t divvied up where that mass comes from until now, says theoretical physicist André Walker-Loud of Lawrence Berkeley National Laboratory in California. “It’s exciting because it’s a sign that … we’ve really hit this new era” in which lattice QCD can be used to better understand nuclear physics.

    In addition to the 9 percent of the proton’s mass that comes from quarks’ heft, 32 percent comes from the energy of the quarks zipping around inside the proton, Liu and colleagues found. (That’s because energy and mass are two sides of the same coin, thanks to Einstein’s famous equation, E=mc2.) Other occupants of the proton, massless particles called gluons that help hold quarks together, contribute another 36 percent via their energy.

    The remaining 23 percent arises due to quantum effects that occur when quarks and gluons interact in complicated ways within the proton. Those interactions cause QCD to flout a principle called scale invariance. In scale invariant theories, stretching or shrinking space and time makes no difference to the theories’ results. Massive particles provide the theory with a scale, so when QCD defies scale invariance, protons also gain mass.

    The results of the study aren’t surprising, says theoretical physicist Andreas Kronfeld of Fermilab in Batavia, Ill. Scientists have long suspected that the proton’s mass was made up in this way. But, he says, “this kind of calculation replaces a belief with scientific knowledge.”

    See the full article here .


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  • richardmitnick 12:16 pm on November 23, 2018 Permalink | Reply
    Tags: A low-altitude meteor explosion around 3700 years ago destroyed cities villages and farmland north of the Dead Sea rendering the region uninhabitable for 600 to 700 years, An exploding meteor may have wiped out ancient Dead Sea communities, , , Science News   

    From Science News: “An exploding meteor may have wiped out ancient Dead Sea communities” 

    From Science News

    November 20, 2018
    Bruce Bower

    Archaeologists at a site in what’s now Jordan have found evidence of a cosmic calamity.

    1
    ANCIENT WIPEOUT Preliminary evidence indicates that a low-altitude meteor explosion around 3,700 years ago destroyed cities, villages and farmland north of the Dead Sea (shown in the background above) rendering the region uninhabitable for 600 to 700 years.

    A superheated blast from the skies obliterated cities and farming settlements north of the Dead Sea around 3,700 years ago, preliminary findings suggest.

    Radiocarbon dating and unearthed minerals that instantly crystallized at high temperatures indicate that a massive airburst caused by a meteor that exploded in the atmosphere instantaneously destroyed civilization in a 25-kilometer-wide circular plain called Middle Ghor, said archaeologist Phillip Silvia. The event also pushed a bubbling brine of Dead Sea salts over once-fertile farm land, Silvia and his colleagues suspect.

    People did not return to the region for 600 to 700 years, said Silvia, of Trinity Southwest University in Albuquerque. He reported these findings at the annual meeting of the American Schools of Oriental Research on November 17.

    Excavations at five large Middle Ghor sites, in what’s now Jordan, indicate that all were continuously occupied for at least 2,500 years until a sudden, collective collapse toward the end of the Bronze Age. Ground surveys have located 120 additional, smaller settlements in the region that the researchers suspect were also exposed to extreme, collapse-inducing heat and wind. An estimated 40,000 to 65,000 people inhabited Middle Ghor when the cosmic calamity hit, Silvia said.

    The most comprehensive evidence of destruction caused by a low-altitude meteor explosion comes from the Bronze Age city of Tall el-Hammam, where a team that includes Silvia has been excavating for the last 13 years. Radiocarbon dating indicates that the mud-brick walls of nearly all structures suddenly disappeared around 3,700 years ago, leaving only stone foundations.

    What’s more, the outer layers of many pieces of pottery from same time period show signs of having melted into glass. Zircon crystals in those glassy coats formed within one second at extremely high temperatures, perhaps as hot as the surface of the sun, Silvia said.

    High-force winds created tiny, spherical mineral grains that apparently rained down on Tall el-Hammam, he said. The research team has identified these minuscule bits of rock on pottery fragments at the site.

    Examples exist of exploding space rocks that have wreaked havoc on Earth (SN: 5/13/17, p. 12). An apparent meteor blast over a sparsely populated Siberian region in 1908, known as the Tunguska event, killed no one but flattened 2,000 square kilometers of forest. And a meteor explosion over Chelyabinsk, Russia, in 2013 injured more than 1,600 people, mainly due to broken glass from windows that were blown out.

    See the full article here .


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  • richardmitnick 3:19 pm on November 11, 2018 Permalink | Reply
    Tags: , , , , Hints of Oort clouds around other stars may lurk in the universe’s first light, Science News   

    From Science News: “Hints of Oort clouds around other stars may lurk in the universe’s first light” 

    From Science News

    November 9, 2018
    Lisa Grossman

    Searching the cosmic microwave background could reveal other giant spheres of icy debris.

    1
    HIDDEN TREASURES This map of the cosmic microwave background taken by the Planck satellite could also hide signs of exo-Oort clouds — planetary graveyards surrounding other stars.

    A thick sphere of icy debris known as the Oort cloud shrouds the solar system. Other star systems may harbor similar icy reservoirs, and those clouds may be visible in the universe’s oldest light, researchers report.

    Oort Cloud, The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA, Universe Today

    Astronomer Eric Baxter of the University of Pennsylvania and colleagues looked for evidence of such exo-Oort clouds in maps of the cosmic microwave background, the cool cosmic glow of the first light released after the Big Bang, roughly 13.8 billion years ago. No exo-Oort clouds have been spotted yet, but the technique looks promising, the team reports November 2 in The Astronomical Journal. Finding exo-Oort clouds could help shed light on how other solar systems — and perhaps even our own — formed and evolved.

    The Oort cloud is thought to be a planetary graveyard stretching between about 1,000 and 100,000 times as far from the sun as Earth. Scientist think that this reservoir of trillions of icy objects formed early in the solar system’s history, when violent movements of the giant planets as they took shape tossed smaller objects outward. Every so often, one of those frozen planetary fossils dives back in toward the sun and is visible as a comet (SN: 11/16/13, p. 14).

    But it’s difficult to observe the Oort cloud directly from within it. Despite a lot of circumstantial evidence for the Oort cloud’s existence, no one has ever seen it.

    Ironically, exo-Oort clouds might be easier to spot, Baxter and colleagues thought. The objects in an exo-Oort cloud wouldn’t reflect enough starlight to be seen directly, but they would absorb starlight and radiate it back out into space as heat. For the sun’s Oort cloud, that heat signal would be smeared evenly across the entire sky from Earth’s perspective. But an exo-Oort cloud’s warmth would be limited to a tiny region around its star.

    Baxter and colleagues calculated that the expected temperature of an exo-Oort cloud should be about –265° Celsius, or 10 kelvins. That’s right in range for experiments that detect the cosmic microwave background, or CMB, which is about 3 kelvins.

    The team used data from the CMB-mapping Planck satellite to search for areas across the sky with the right temperature (SN Online: 7/24/18).

    ESA/Planck 2009 to 2013

    Then, the researchers compared the results with the Gaia space telescope’s ultraprecise stellar map to see if those regions surrounded stars (SN: 5/26/18, p. 5).

    ESA/GAIA satellite

    ESA GAIA Release 2 map

    Although the astronomers found some intriguing signals around several bright, nearby stars, it wasn’t enough to declare victory. “That’s pretty interesting, but we can’t definitively say that it’s from an Oort cloud or not,” Baxter says.

    Other ongoing CMB experiments with higher resolution, like those with the South Pole Telescope and the Atacama Cosmology Telescope in the Chilean Andes, could confirm if those hints of exo-Oort clouds are real.

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including the University of Chicago, the University of California, Berkeley, Case Western Reserve University, Harvard/Smithsonian Astrophysical Observatory, the University of Colorado Boulder, McGill University, The University of Illinois at Urbana-Champaign, University of California, Davis, Ludwig Maximilian University of Munich, Argonne National Laboratory, and the National Institute for Standards and Technology. It is funded by the National Science Foundation.

    ACT

    “It’s a super clever observational idea,” says astronomer Nicolas Cowan of McGill University in Montreal who was not involved in the new work. “Looking for exo-Oort clouds is looking for a signature of these violent histories in other solar systems.”

    Cowan has suggested that the cosmic microwave background could also be used to search for a hypothetical Planet Nine in the sun’s Oort cloud (SN: 7/23/16, p. 7). “The very coolest thing would be if we could get measurements of the exo-Oort clouds and find planets in those systems,” he says.

    See the full article here .


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  • richardmitnick 12:07 pm on November 8, 2018 Permalink | Reply
    Tags: , , Science News, Weyl metals might reveal the secrets of how Earth gets its magnetic field   

    From Science News: “Bizarre metals may help unlock mysteries of how Earth’s magnetic field forms” 

    From Science News

    November 7, 2018
    Emily Conover

    The dynamo effect that generates Earth’s magnetic pull could also occur in Weyl metals.

    1
    MAKING MAGNETISM Earth’s magnetic field (illustrated) as well as those of stars and other astronomical objects are created by flows of electrically conductive substances. On smaller scales, such dynamos may also be created by materials called Weyl metals. Goddard Space Flight Center/NASA.

    Weird materials called Weyl metals might reveal the secrets of how Earth gets its magnetic field.

    The substances could generate a dynamo effect, the process by which a swirling, electrically conductive material creates a magnetic field, a team of scientists reports in the Oct. 26 Physical Review Letters.

    Dynamos are common in the universe, producing the magnetic fields of the Earth, the sun and other stars and galaxies. But scientists still don’t fully understand the details of how dynamos create magnetic fields. And, unfortunately, making a dynamo in the lab is no easy task, requiring researchers to rapidly spin giant tanks of a liquefied metal, such as sodium (SN: 5/18/13, p. 26).

    First discovered in 2015, Weyl metals are topological materials, meaning that their behavior is governed by a branch of mathematics called topology, the study of shapes like doughnuts and knots (SN: 8/22/15, p. 11). Electrons in Weyl metals move around in bizarre ways, behaving as if they are massless.

    Within these materials, the researchers discovered, electrons are subject to the same set of equations that describes the behavior of liquids known to form dynamos, such as molten iron in the Earth’s outer core. The team’s calculations suggest that, under the right conditions, it should be possible to make a dynamo from solid Weyl metals.

    It might be easier to create such dynamos in the lab, as they don’t require large quantities of swirling liquid metals. Instead, the electrons in a small chunk of Weyl metal could flow like a fluid, taking the place of the liquid metal.

    The result is still theoretical. But if the idea works, scientists may be able to use Weyl metals to reproduce the conditions that exist within the Earth, and better understand how its magnetic field forms.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

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  • richardmitnick 4:55 pm on November 5, 2018 Permalink | Reply
    Tags: , , , Physicists measured Earth’s mass using neutrinos for the first time, , Science News   

    From Science News: “Physicists measured Earth’s mass using neutrinos for the first time” 

    From Science News

    November 5, 2018
    Emily Conover

    The tiny particles provide an independent test of some of the planet’s key properties.

    1
    PARTICLE PROBES Subatomic particles called neutrinos are created when spacefaring protons and other particles smash into Earth’s atmosphere (illustrated). Scientists have now used neutrinos to measure the Earth’s mass and the densities of its layers. Earth: Reto Stöckli, Nazmi El Saleous and Marit Jentoft-Nilsen/GSFC/NASA, adapted by E. Otwell

    Puny particles have given scientists a glimpse inside the Earth.

    For the first time, physicists have measured the planet’s mass using neutrinos, minuscule subatomic particles that can pass straight through the entire planet. Researchers also used the particles to probe the Earth’s innards, studying how the planet’s density varies from crust to core.

    Typically, scientists determine Earth’s mass and density by quantifying the planet’s gravitational pull and by studying seismic waves that penetrate the globe. Neutrinos provide a completely independent test of the planet’s properties. Made using data from the IceCube neutrino observatory at the South Pole, the new planetary profile agreed with traditional measurements, a trio of physicists reports November 5 in Nature Physics.

    U Wisconsin IceCube neutrino observatory

    U Wisconsin IceCube experiment at the South Pole



    U Wisconsin ICECUBE neutrino detector at the South Pole


    IceCube Gen-2 DeepCore PINGU


    IceCube reveals interesting high-energy neutrino events

    To make the measurement, the scientists studied high-energy neutrinos that were produced when protons and other energetic particles from space slammed into the Earth’s atmosphere. These neutrinos can zip clean through the entire Earth, but sometimes they smash into atomic nuclei and are absorbed instead. How often neutrinos get stopped in their tracks reveals the density of the stuff they’re traveling through.

    Neutrinos that arrived at the IceCube detector from different angles probed different layers of the Earth. For example, a neutrino coming from the opposite side of the planet, at the North Pole, would pass through the Earth’s crust, mantle and core before reaching the South Pole. But one that skimmed in at an angle might pass through only the crust. By measuring how many neutrinos came from various angles, the team inferred the densities of different parts of the Earth and its total mass.

    The technique doesn’t yet reveal anything new about the planet. But one day it might help scientists determine whether all of Earth’s mass comes from normal matter. Perhaps some of the mass is due to something that shuns neutrinos, such as a type of dark matter, a shadowy substance that scientists believe must exist to account for missing mass observed in measurements of other galaxies. Neutrinos could help physicists nail down whether the Earth harbors such dark matter within.

    See the full article here .


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  • richardmitnick 2:28 pm on November 3, 2018 Permalink | Reply
    Tags: A new measurement bolsters the case for a (slightly) smaller proton, , , , Proton size, Science News   

    From Science News: “A new measurement bolsters the case for a (slightly) smaller proton” 

    From Science News

    November 2, 2018
    Emily Conover

    The PRad physics experiment studies how electrons scatter off of protons.

    1
    EXTRA SMALL Protons are small, but scientists disagree on exactly how small. A new finding from the PRad physics experiment suggests that the subatomic particle is extra tiny.
    pixelparticle/Shutterstock

    A scientific tug-of-war is underway over the size of the proton. Scientists can’t agree on how big the subatomic particle is, but a new measurement has just issued a forceful yank in favor of a smaller proton.

    By studying how electrons scatter off of protons, scientists with the PRad experiment [APS Bulleton] at Jefferson Laboratory in Newport News, Va., sized up the proton’s radius at a measly 0.83 femtometers, or millionths of a billionth of a meter. That’s about 5 percent smaller than the currently accepted radius, about 0.88 femtometers.

    The new figure adds to a muddle of measurements, each of which seems to fall into one of two camps — favoring either the standard radius or one a tad smaller. With the new result from PRad, “if anything, the proton radius puzzle has become even more puzzling,” says physicist Nilanga Liyanage of the University of Virginia in Charlottesville. He presented the result on October 23 at a joint meeting of the American Physical Society Division of Nuclear Physics and the Physical Society of Japan, held in Waikoloa, Hawaii.

    The experiment, in which electrons scatter off of the protons contained in hydrogen gas, improves upon previous electron-proton scattering experiments by catching electrons that scatter away at glancing angles, as small as 0.6 degrees. Such electrons help suss out the protons’ size by probing the outermost edges of the protons.

    2
    LET’S BOUNCE The PRad experiment (shown) works by bouncing electrons off of protons. The angles at which the electrons scatter away tell scientists how big the proton is. PRad Collaboration

    PRad’s small radius is in conflict with previous electron-proton scattering measurements as well as some hydrogen-radius measurements made using different techniques. However, the result is still preliminary, the researchers caution. Additional work is needed before the finding is submitted to a scientific journal and its merits judged by other researchers.

    “It’s a great result; it’s a hard experiment,” says physicist Jan Bernauer of Stony Brook University in New York, who worked on an earlier electron-proton scattering measurement by a team of scientists called the A1 collaboration. Still, he says, “it’s a little bit early to say anything” about the proton’s true size.

    In addition to electron-proton scattering, scientists use two other techniques to gauge the proton’s girth. One method, called hydrogen spectroscopy, uses lasers to study the energy levels of the hydrogen atom. Since each hydrogen atom is composed of a single proton and a single electron, the atoms’ energy levels depend on how large the proton is. Another technique, introduced in 2010, is similar to hydrogen spectroscopy, but the hydrogen atoms’ electrons are swapped for a heavier electron relative, called a muon.

    That switcheroo is what kicked off the whole kerfuffle over the proton’s size in the first place. The first such measurement, published in Nature in 2010, came up with an unexpectedly slim proton (SN: 7/31/10, p. 7). But the plot thickened further that year when the A1 electron-proton scattering measurement [Physical Review Letters]found a larger radius, in agreement with older measurements (SN Online: 12/17/10).

    Meanwhile, new spectroscopy measurements — made with normal hydrogen — are also in a jumble. One such measurement, published in 2017 in Science, found a small radius (SN: 11/11/17, p. 14). The same goes for another study reported in July at the International Conference on Atomic Physics in Barcelona. But a large proton radius was found in a study published in May in Physical Review Letters.

    The proton’s radius is an important property of nature. And the confusion about its size is preventing scientists from performing other experiments, such as testing the theory of quantum electrodynamics, which describes how light and charged particles behave.

    At first, the proton radius woes had scientists excited that the discrepancy might reveal the existence of new particles or other secrets of physics. But such explanations now seem not to work, says physicist Marko Horbatsch of York University in Toronto.

    Future experiments could help resolve the disagreement, including the upcoming MUSE experiment, under construction at the Paul Scherrer Institute in Switzerland, which will scatter muons off of protons. But for now, the debate continues. “Science is not as hard and exact as you would want to make people believe,” Horbatsch says.

    See the full article here .


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  • richardmitnick 12:42 pm on October 18, 2018 Permalink | Reply
    Tags: , , , Science News   

    From Science News: “To unravel autism’s mysteries, one neuroscientist looks at the developing brain” 

    From Science News

    October 16, 2018
    Laura Sanders

    Understanding how the disorder arises could lead to new interventions.

    1
    HEAD START Studying early signs of autism in the developing brain may ultimately help researchers figure out why more boys are diagnosed with the disorder than girls. Africa Studio/Shutterstock

    As the number of children diagnosed with autism spectrum disorder increases, so too has research on the complex and poorly understood disorder. With powerful genetic tools, advanced brain-imaging methods and large groups of children to study, the field is poised to make big contributions in understanding — and potentially treating — autism.

    Neuroscientist Kevin Pelphrey, who is formerly of George Washington University in Washington, D.C., but has recently moved to the University of Virginia in Charlottesville, studies autism’s beginnings. He described some of his findings about the link between brain development and the disorder on October 15 at a meeting of the Council for the Advancement of Science Writing.

    Here are some of the key points Pelphrey made on how autism may get its start in the developing brain, how the disorder is different between boys and girls, and how large, long-term studies of children with autism might yield clues about the condition.

    What causes autism spectrum disorder?

    For most cases, no one knows. There’s likely no single cause — environmental and genetic risk factors work in combination. In some children, rare mutations in key genes have been linked to the disorder. More commonly, many genetic changes, each with a small influence on overall risk, may increase a child’s likelihood of developing the disorder.

    With the number of autism diagnoses growing, partly due to better detection, researchers are looking at potential factors beyond genetics, such as parents’ age, premature birth and maternal obesity.

    When does the disorder begin?

    On average, kids are diagnosed with autism around the age of 4, though symptoms can appear by around age 2. But Pelphrey says the disorder starts long before then, as the brain is built in utero (SN: 4/29/17, p. 10). Evidence is growing that alterations in brain development, perhaps in nerve cell connections or communication between brain regions, are involved in the disorder.

    By studying newborns and even fetuses, Pelphrey aims to uncover some of the key differences in the brains of babies who go on to develop the disorder. That early detection could ultimately allow clinicians to change the brain’s developmental trajectory in a way that prevents the disorder.

    How close are scientists to an autism biomarker?

    Biological signatures, or biomarkers, of autism might enable both earlier detection and a way to see if interventions to treat the disorder are working. In 2017, researchers found signatures of autism [PubMed] in the brains of 6-month-old babies who would go on to be diagnosed with the disorder at age 2. Other attempts to find autism markers involve abnormal neural activity [Journal of Neurosciene], differences in eye contact [Nature] and even changes in gut microbes.

    But for a biomarker to be useful, it needs to check a lot of boxes, Pelphrey said. It must be reliable, predictive, informative at the individual level and easy to bring into pediatricians’ offices, among other things. So far, none of the proposed biomarkers check all of those boxes.

    Along with colleagues, Pelphrey is studying the utility of a brain-imaging technique that could make spotting abnormal neural activity a little easier for clinicians. Called functional near-infrared spectroscopy, it uses light to measure oxygenated blood as a proxy of brain activity. The method is less precise than MRI but cheaper and more mobile.

    Why do more boys get autism diagnoses than girls?

    Researchers don’t yet know for sure. Scientists recently began studying the differences between boys and girls, in the hopes of explaining why an estimated four boys are diagnosed with autism for every girl diagnosed. One clue comes from big genetic studies that suggest girls are somehow more resistant to genetic mutations than boys (SN Online: 2/27/14). Sex hormones may also have something to do with the differences between boys and girls, Pelphrey says.

    What’s more, by looking at brain behavior, scientists are beginning to suspect that girls’ autism is, at its core, distinct from that of boys. “The behaviors that we call autism, while on the surface are the same, have different biological origins,” Pelphrey says.

    Females with autism, for example, are more likely to have stronger social abilities, though it may be hard work for the girls [PubMed], a 2017 study suggests.

    What’s the future of autism research?

    Autism is an idiosyncratic disorder, one that’s likely a bit different for each person. As such, making progress toward understanding common pathways will require large numbers of subjects and many types of measurements.

    With collaborators, Pelphrey has collected data on genetics, brain behavior and structure, and behavior for about 500 children with autism, about half of whom are girls, he says. That project will continue to recruit more participants and also collect personal experiences and adult outcomes.

    Other large research collectives will likely move the field forward, such as the Simons Foundation’s Simons Simplex Collection, which contains genetic samples from 2,600 families with children with autism.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

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  • richardmitnick 1:46 pm on October 6, 2018 Permalink | Reply
    Tags: , , , , Science News, The universe’s continued existence implies extra dimensions are tiny, This could be the way the world ends., Where the black hole just was a bubble of space with entirely different laws of physics than the universe we inhabit would begin to grow expanding ever-outward at the speed of light. In its wake atoms   

    From Science News: “The universe’s continued existence implies extra dimensions are tiny” 

    From Science News

    October 5, 2018
    Lisa Grossman

    1
    POP GOES THE UNIVERSE If extra dimensions were large enough, a universe with different laws of physics could bubble up from the death of a black hole. That would be bad news for us: The new version would be uninhabitable. Vectorpocket/shutterstock

    This could be the way the world ends.

    First, a pair of cosmic protons smash together at unimaginable speeds. The tremendous energy of their crash would create a tiny, ephemeral black hole, so small that it would last just a fraction of a second before evaporating.

    Where the black hole just was, a bubble of space with entirely different laws of physics than the universe we inhabit would begin to grow, expanding ever-outward at the speed of light. In its wake, atoms would disintegrate, and the universe as we know it would fizzle out of existence.

    “If you’re standing nearby when the bubble starts to expand, you don’t see it coming,” says Katie Mack, a physicist at North Carolina State University in Raleigh. “If it’s coming at you from below, your feet stop existing before your mind realizes that.”

    That horror movie can happen only if the universe has at least one extra dimension, on top of three of space and one of time.

    But this isn’t the way the world ends — at least it hasn’t yet.

    And so the fact that the universe hasn’t been destroyed by evaporating black holes puts strict limits on the size of extra dimensions, if any actually exist, Mack and Robert McNees of Loyola University Chicago claim in a paper posted online at arXiv.org September 13.

    Scientists have yet to find evidence of extra dimensions, a lack that suggests that any real ones must be minuscule. But their existence could help explain mysteries like dark energy and dark matter, and point the way to new physics beyond the standard model of particle physics (SN: 9/29/18, p. 18), so physicists are eager to probe their properties any way they can.

    Even tiny extra dimensions could have an influence on the universe, physicists suspect. For instance, gravity could leak into these extra dimensions, perhaps explaining why that force appears so much weaker than the other fundamental forces (SN: 9/29/18, p. 8).

    That leakage could also lower the bar for creating miniature black holes — at the tiny distances that the extra dimensions affect, gravity would appear much stronger. “If you have these extra dimensions, you don’t need to get as much matter in as small a space to make a black hole as you would without the extra dimensions,” Mack says.

    That’s why some people thought the Large Hadron Collider at CERN near Geneva might make tiny black holes when it turned on in 2008, but so far none have appeared (SN Online: 6/24/08).

    Nature can collide particles with even higher energies, though. The highest are found in ultrahigh energy cosmic rays, protons that zip between galaxies with energies higher than 8 billion billion electron volts (SN: 10/14/17, p. 7). That’s 100 million times as high as the energies produced by the LHC. If collisions between those particles have made any black holes, then physicists could work out the gravitational reach of any extra dimensions, or how close you have to get to an object before gravity starts acting weird.

    This scenario has a dark side. According to a theory first put forward by Stephen Hawking in the 1970s, energy radiates away from a black hole until the black hole eventually disappears (SN: 4/14/18, p. 12). The smaller the black hole, the faster it evaporates, so any black holes made by colliding cosmic rays would fizzle almost instantaneously, or so the theory goes.

    That could be bad news for the universe. In 2015, theoretical physicist Ruth Gregory of Durham University in England and her colleagues showed mathematically that when black holes evaporate, they can nudge the universe into a state in which the laws of physics are so different that atoms no longer hold together.

    “No structures can exist,” Mack says. “We’d just blink out of existence.”

    This catastrophe is called vacuum decay. It relies on the idea that the fundamental nature of the universe, called its vacuum state, might not be the most stable one possible. There could be another configuration of physical laws, the true vacuum, that sits in a lower energy state.

    Evaporating black holes could provide the bump needed to create a bubble of this true vacuum, Gregory and her colleagues argued. And once some true vacuum exists, the space around it would want to join the true vacuum. The bubble would expand outward at the speed of light, taking the known universe with it.

    “The black holes are quite naughty,” Gregory says. “They really want to seed vacuum decay. It’s a very strong process, if it can proceed.”

    That set of ideas leads to a paradox, Mack and McNees realized. Collisions between ultrahigh energy cosmic rays “should have happened thousands of times,” McNees says. If extra dimensions exist, and if they are large enough for ultrahigh energy cosmic rays to make mini black holes, then vacuum decay should already have happened. The fact that we’re here to wonder about it means that extra dimensions, if they exist, must be even smaller than previously thought.

    Mack and McNees calculated that any extra dimensions must be smaller than about 16 nanometers, or billionths of a meter. In other words, the gravitational influence of the extra dimensions would extend only that far. That’s hundreds of times smaller than the previous best estimates and rules out some of the theories that let gravity leak into extra dimensions.

    The analysis is fun and thorough, says cosmologist Ian Moss of Newcastle University in England, who worked with Gregory on the 2015 paper. But he’s worried that Mack and McNees make too many assumptions about what conditions would lead to vacuum decay.

    “You can’t really say that these limits are totally convincing,” he says. “There’s nothing wrong, but there’s so many ifs.”

    See the full article here .


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