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  • richardmitnick 5:32 pm on April 5, 2017 Permalink | Reply
    Tags: , GERDA collaboration, GIZMODO, , Scientists Are Getting Closer to Understanding Where All the Antimatter Has Gone   

    From GIZMODO: “Scientists Are Getting Closer to Understanding Where All the Antimatter Has Gone’ 

    GIZMODO bloc

    GIZMODO

    4.5.17
    Ryan F. Mandelbaum

    1
    From Nature: “The fiber shroud of the liquid argon veto and the copper head for mounting the germanium strings. View from bottom.” Image: V. Wagner, GERDA collaboration

    You and me, we’re matter. Everyone you know is matter. Everything on Earth, spare a few particles, is matter. Most of the things in space are matter. But we don’t have convincing reasons why there should be so much more matter than antimatter. So where’s all the antimatter?

    A team of European scientists have taken a major step in understanding this conundrum, using a house-sized detector called the Germanium Detector Array, or GERDA, buried inside a mountain in Grand Sasso, Italy. GERDA’s scientists are looking for a strange behavior in radioactive atoms, called “neutrinoless double beta decay” (I’ll get to that in a second). Some versions of the rules of particle physics says this behavior could help explain where all the antimatter went. But for now, the experiment is reporting some important results: it works.

    “A discovery of [neutrinoless double beta] decay would have far-reaching consequences for our understanding of particle physics and cosmology,” the researchers write in the paper, published today in the journal Nature. It’s important that we understand why there is more matter than antimatter today. The Big Bang probably should have created equal amounts… but it didn’t [CERN].

    If you’ve got a good handle on what neutrinoless double beta decay is, you can skip the next three paragraphs. If not, it’s time for a break from our regular programming.

    Matter is stuff, and it’s made of particles. Antimatter is also stuff, made from the particles’ antiparticle counterparts. We’ve made it in labs and some radioactive elements produce it. Every particle has an antiparticle, like electrons and positrons, which have the same mass, but opposite electric charge. If they meet, they annihilate each other in a burst of energy. There is not a lot of antimatter in the universe. Capisce?

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    From Nature: “The inner walls of the water tank are covered by a reflecting foil improving the light detection. This permits the identification of cosmic muons.” Image: K. Freund, GERDA collaboration

    Neutrinos, they’re weird. Scientists don’t know how much they weigh, but even at the upper limit of what we guess their mass is, they’re many times lighter than electrons. They’re also really common—for example, the sun sending almost a hundred billion of them per square centimeter of your body every second. They don’t interact via electromagnetism, though, so they don’t harm us in any way. If they were their own antiparticle, what scientists call “Majorana particles,” they should annihilate one another. Most extensions of our main theory of particle physics, called the Standard Model, say this is true.

    So, the key is to build an experiment that can test whether neutrinos are annihilating one another, and to look for a process that should usually create neutrinos, but doesn’t. In this case, that process is radioactive beta decay, where the neutral neutron turns into a positive proton, a negative electron, and an antineutrino. Some forms of some atoms, like germanium should go through double beta decay, where two neutrons decay simultaneously. If scientists observe double beta decay without any neutrinos (or antineutrinos), then they can say they’ve spotted this neutrinoless double beta decay. This would demonstrate that neutrinos and antineutrinos are essentially the same, and convince us that our physics theories can explain why there’s more matter than antimatter.

    3
    From Nature: “Working on the germanium detector array within the glove box which is located in the clean room on top of the liquid argon cryostat.” (Image: J. Suvorov, GERDA collaboration)

    That’s what GERDA is looking for. They’re watching 35.6 kilograms of a special form of germanium, the shiny semiconducting metal, sitting inside a vat of liquid argon inside a bigger vat of water, waiting however long it takes for it to experience a neutrinoless double beta decay. No, they haven’t found any evidence of the process yet. But their experiment works really, really well—there’s no background noise, which is an incredible feat. Otherwise, we might see a false signal. And there’s radiation that could set off the detector everywhere, from the sun to the air we breathe.

    “Imagine running a radiation detector for a year and seeing nothing! It’s quite an experience,” said Duke physicist Phillip Barbeau, who is not involved in the GERDA collaboration, in an interview with Gizmodo. “We need discerning detectors, ones that avoid sources of these backgrounds by going deep underground, avoiding dust, building them in clean rooms, avoiding cosmic activation of these materials. After all, they can turn radioactive simply by being above ground.”

    Scientists are at least sure that the experiment is working, and not just turned off, by the way. “People would give them the benefit of the doubt,” said Barbeau. But “it’s a difficult experiment to run because you see nothing in the detector.”

    But there are plenty of other complicating factors in this process aside from getting rid of all the outside noise. Most processes we’ve observed in the universe conserves a property called lepton number. In theory, the number of leptons (neutrinos and electrons are examples of leptons) minus the number of antileptons should remain the same before and after some physical reaction. Regular beta decay starts with a lepton number of zero and ends with zero (one electron minus one antineutrino). Neutrinoless double beta decay starts with zero and ends with two. As a note, we want to see this violation happen. I’m just pointing out that this decay is breaking a not-that-well-supported rule.

    And the neutrinoless double beta decay is really, really rare—its half life, the amount of time it takes for half of the possible events to happen, is several times the age of the universe. So scientists might have to sit and watch this vat for a very, very long time. But hey, that’s why they have so much germanium.

    GERDA isn’t the only experiment looking for this decay—there’s the MAJORANA experiment, the CUORE-0, COBRA, and others.

    U Washington Majorana Demonstrator Experiment at SURF

    3
    Yale CUORE-0

    Anyway, now that we’ve got the working GERDA detector…it’s time to watch and wait.

    Yale CUORE-0

    If we don’t spot this decay, we might just have to go looking for other evidence of neutrinos being their own antiparticles. And there’s so much more about neutrinos we don’t know—we can’t even accurately measure their mass, for example.

    See the full article here .

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    “We come from the future.”

    GIZMOGO pictorial

     
  • richardmitnick 11:55 am on March 30, 2017 Permalink | Reply
    Tags: Asteroid Bee-Zed, , , , , , GIZMODO, or 2015 BZ509   

    From GIZMODO: “This Backwards-Orbiting Asteroid Has Been Flirting With Death For a Million Years” 

    GIZMODO bloc

    GIZMODO

    3.30.17
    George Dvorsky

    1
    The retrograde asteroid is shown in green. (Credit: Paul Weigert/Western University)

    Most asteroids orbit the Sun in a counterclockwise fashion, but a newly-discovered object nicknamed Bee-Zed goes against the grain, spinning around the Solar System the opposite way. Not only that, it frequently ventures within Jupiter’s orbital space—putting it on a potential collision course with the gas giant and its 6,000 co-orbiting asteroids.

    Of the millions of documented asteroids in the Solar System, a scant 82 of them, or 0.01 percent, orbit the Sun in a retrograde motion. But as a new study in Nature points out, asteroid Bee-Zed, or 2015 BZ509, is exceptional even among these backwards-orbiting misfits. It has the distinction of being the only known retrograde object in the Solar System that shares its orbital plane with another planet, in this case mighty Jupiter.

    What makes this celestial anomaly stranger still is that Jupiter is accompanied by 6,000 “Trojan” asteroids, the vast majority of which follow the gas giant in a prograde orbit (a small number of Trojans orbit Jupiter in a retrograde motion, but unlike Bee-Zed, they don’t orbit the Sun independently). Similar to a racecar driver going the wrong way around a track, Bee-Zed is careening towards these objects with each trip around the Sun. According to calculations made by Western University astronomer Paul Weigert, Bee-Zed has been doing this for at least a million years, amounting to tens of thousands of successful “laps” around the Sun. So far, it has emerged unscathed from these close encounters.

    Bee-Zed’s success may not be an accident. As noted in the study, Jupiter’s gravity is causing the rogue asteroid to weave in and out of the planet’s path each time the two objects pass. It’s the only asteroid known to have this relationship with a planet, and this state of “synchronicity” should allow Bee-Zed to avoid a catastrophic collision with either Jupiter or one of its Trojans for the next million years at least. This analysis is based on calculations and observations made with the Large Binocular Camera on the Large Binocular Telescope in Mt. Graham, Arizona.


    Large Binocular Telescope, Mount Graham, Arizona, USA

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    With each orbit Bee-Zed and Jupiter make around the sun, the retrograde object passes once inside and once outside the gas giant. This results in two opposing gravitational nudges that keeps the object on a safe path. Even though Bee-Zed crosses Jupiter’s orbital plane, it never actually gets too close; the nearest the two objects get to each other is about 109 million miles, roughly the distance between Earth and the Sun. So for Bee-Zed, it’s like playing “chicken” with a massive semi-truck—but the space rock only ventures onto its path when the truck is still far, far away.

    Not much is known about Bee-Zed, which was discovered by the Panoramic Survey Telescope And Rapid Response System (Pan-STARRS) in 2015.


    Pan-STARRS1 located on Haleakala, Maui, HI, USA

    And although astronomers presume it to be a rocky asteroid, they aren’t even entirely sure—it could be an ice-covered comet. In fact, it may have originated from the same place as Halley’s Comet, perhaps the most famous retrograde object in the Solar System.

    See the full article here .

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  • richardmitnick 1:31 pm on March 28, 2017 Permalink | Reply
    Tags: , , , GIZMODO, , , SUPERRADIANCE   

    From PI via GIZMODO: “Mind-Blowing New Theory Connects Black Holes, Dark Matter, and Gravitational Waves” 

    Perimeter Institute
    Perimeter Institute

    GIZMODO

    3.28.17
    Ryan F. Mandelbaum

    The past few years have been incredible for physics discoveries. Scientists spotted the Higgs boson, a particle they’d been hunting for almost 50 years, in 2012, and gravitational waves, which were theorized 100 years ago, in 2016. This year, they’re slated to take a picture of a black hole. So, thought some theorists, why not combine all of the craziest physics ideas into one, a physics turducken? What if we, say, try to spot the dark matter radiating off of black holes through their gravitational waves?

    It’s really not that strange of an idea. Now that scientists have detected gravitational waves, ripples in spacetime spawned by the most violent physical events, they want to use their discovery to make real physics observations. They think they have a way to spot all-new particles that might make up dark matter, an unknown substance that accounts for over 80 percent of all of the gravity in the universe.

    The basic idea is that we’re trying to use black holes… the densest, most compact objects in the universe, to search for new kinds of particles,” Masha Baryakhtar, postdoctoral researcher at the Perimeter Institute for Theoretical Physics in Canada, told Gizmodo. Especially one particle: “The axion. People have been looking for it for 40 years.”

    Black holes are the universe’s sinkholes, so strong that light can’t escape their pull once it’s entered. They’ve got such powerful gravitational fields that they produce gravitational waves when they collide with each other. Dark matter might not be made from particles (specks of mass and energy), but if it was, we might observe it as axions, particles around one quintillion (a billion billion) times lighter than an electron, hanging around black holes. Now that you understand all the terms, here’s how the theory works.

    Baryakhtar and her teammates think that black holes are more than just bear traps for light, but nuclei at the center of a sort of gravitational atom. The axions would be the electrons, so to speak. If you already know about black holes, you know they have incredibly hot, high-energy discs of gas orbiting them, produced by the friction between particles accelerated by the black hole’s gravity. This theory ignores that stuff, since axions wouldn’t interact via friction.

    Keeping with the atom analogy, the axions can jump around the black hole, gaining and losing energy the same way that electrons do. But electrons interact via electromagnetism, so they let out electromagnetic waves, or light waves. Axions interact via gravity, so they let out gravitational waves. But like I said earlier, axions are tiny. Unlike a tiny atom, the black hole in these “gravity atoms” rotates, supercharging the space around it and coaxing it into producing more axions. Despite the axion’s tiny mass, this so-called superradiance process could generate 10^80 axions, the same number of atoms in the entire universe, around a single black hole. Are you still with me? Crazy spinning blob makes lots of crazy stuff.

    Craziest of all, we should be able to hear a gravitational wave hum from these axions moving around and releasing gravitational waves in our detectors, similar to the way you see spectral lines coming off of electrons in atoms in chemistry class. “You’d see this at a particular frequency which would be roughly twice the axion mass,” said Baryakhtar.

    There are giant gravitational wave detectors scattered around the world; presently there’s one called LIGO (Laser Interferometer Gravitational Wave Observatory) in Washington State, another LIGO in Louisiana, and one called Virgo in Italy that are sensitive enough to detect gravitational waves, and with upgrades, to detect axions and prove their theory right.



    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA



    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Scientists would essentially need to record data, play it back, and tune their analysis like a radio to pick up the signal at just the right frequency.

    There are other ways the team thinks it could spot this superradiance effect, by measuring the spins in sets of colliding black holes. If black holes really do produce axions, scientists would see very few quickly-spinning black holes in collisions, since the superradiance effects would slow down some of the colliding black holes and create a visible effect in the data, according to the research published this month in the journal Physical Review D. The black hole spins would have a specific pattern which we should be able to spot in the gravitational wave detector data.

    Other scientists were immediately excited about this paper. “I’m always super excited about new ways to detect my favorite pet particle, the axion! Also, SUPERRADIANCE!” Dr. Chanda Prescod-Weinstein, the University of Washington axion wrangler, told Gizmodo in an email. “It’s so cool, and I haven’t read a paper that talked about [superradiance] in years. So it was really fun to see superradiance and axions in one paper.”

    There are a few drawbacks, as there are with any theory. These theorized black hole atoms would have to produce axions of a certain mass, but that mass isn’t an ideal one for the axion to be a dark matter particle, said Prescod-Weinstein. Plus, the second detection idea, the one that looks at the spin rate of colliding black holes, might not work. “They say [in the paper] that they don’t take into account the potential influence of another black hole” in the colliding pair, Dr. Lionel London, a research associate at Cardiff University School of Physics and Astronomy specializing in gravitational wave modeling, told Gizmodo. “If this does turn out to be a significant effect and they’re not including it, this could cast doubt on their results.” But there’s hope. “There’s good reason to believe the effect of a companion [black hole] won’t be large.”

    When would we spot these kinds of events? As of now, the LIGO and Virgo gravitational wave detectors probably aren’t ready. “With the current sensitivity we’re on the edge” of detecting axions, said Baryakhtar. “But LIGO will continue improving their instruments and at design sensitivity we might be able to see as many as 1000s of these axion signals coming in,” she said. Thousands of hums from these black hole-atoms.

    So, if you’ve gotten all the way to this point of the story and still don’t understand what’s going on, a recap: We’ve got these gravitational wave detectors that cost hundreds of millions of dollars each, that are good at spotting really crazy things going on in the universe. Theorists have come up with an interesting way to use them to solve one of the most important interstellar mysteries: What the heck is dark matter? As with most new ideas in theoretical physics, this is something cool to think about and isn’t ready for the big time… yet.

    “I think that timescale is always a concern, but we’re just getting started with LIGO discoveries,” said Prescod-Weinstein. “So who knows what’s around the corner over the next 10 years.”

    See the full article here .

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    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 11:40 am on February 15, 2017 Permalink | Reply
    Tags: An entire landscape possibly reshaping itself, An iceberg nearly seven times the size of New York City, Antarctic Peninsula’s Larsen C ice shelf, GIZMODO, Glaciology, How ice shelves break, Iceberg calving on a grand scale, UK-based Project MIDAS monitoring the rift via satellites   

    From GIZMODO: “What Happens When That Enormous Antarctic Ice Shelf Finally Breaks?” 

    GIZMODO bloc

    GIZMODO

    2.15.17
    Maddie Stone

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    Rift in the Larsen C ice shelf photographed by NASA’s IceBridge aerial survey in November 2016. Image: NASA/John Sonntag

    For the past few months, scientists have watched with bated breath as a rift in the Antarctic Peninsula’s Larsen C ice shelf grows longer by the day. Eventually, the rift will make a clean break, expelling a 2,000 square mile chunk of ice into the sea. It’ll be an epic sight to behold—but what happens after the ice is gone?

    Glaciologists, who have been tracking the rift since it first appeared on the Larsen C ice shelf in 2014, are now scrambling to answer that very question. So-called iceberg calving is a natural geophysical process along the Antarctica’s frosty fringes; think of it as the planetary equivalent of your fingernails growing too long and breaking off. But this is one of the largest such events on record, with the potential to dramatically reshape the entire peninsula.

    Moreover, while there’s little direct evidence linking the Larsen C ice shelf breakup to climate change, scientists worry that the processes playing out here could be but a taste of what’s to come for West Antarctica, as rising air and sea temperatures cause this vast, icy mantle to weaken from above and below.

    “What we’re worried about is what we’re seeing here is going to happen everywhere else,” Thomas Wagner, director of NASA’s polar science program told Gizmodo. “[Larsen C] is a natural laboratory for understanding how ice shelves break.”

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    Timelapse of the growing rift in the Larsen C ice shelf captured by ESA’s Sentinel-1 satellite. Image: Project MIDAS

    Over 100 miles long, up to two miles wide, and lengthening at a rate of five football fields per day, the rift in the Larsen C ice shelf has been in and out of the spotlight since it first emerged on the eastern flank of the Antarctic Peninsula in 2014. Since punching its way through a section of softer, more ductile ice, the rift has followed a predictable pattern—periods of quietude, punctuated by sudden growth spurts—that experts say is typical of ice shelf calving. But over the last two months, things have accelerated “quite a lot,” according to Martin O’Leary, a glaciologist with the UK-based Project MIDAS, which is monitoring the rift via satellites. “Now we’re paying attention to every satellite image that comes through to see if it jumps again,” he told Gizmodo.

    Having grown an impressive 17 miles (27 km) since December, the Larsen C rift has about 12 miles (20 km) to go before it reaches the other end of the shelf, snaps off, and spits out an iceberg nearly seven times the size of New York City.

    This could happen any day. “It could go tomorrow, it could go in a year’s time,” O’Leary said, adding that the ice “has to leave eventually.” That’s because additional ice is constantly pushing seaward from the peninsula’s interior, exerting a powerful shear force on the ever-weakening shelf.

    The good news is, we don’t have to worry about Larsen C’s breakup contributing to sea level rise. Ice shelves are, by definition, already sitting on top of water. “It’s already made its sea level rise contribution,” O’Leary said.

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    The ice shelves at the tip of the Antarctic Peninsula have been changing dramatically in recent decades, as illustrated in this composite satellite photo showing the historic ice extent prior to calving events. Image: NASA Earth Observatory

    Aside from possibly setting a few penguins adrift, the real concern with Larsen C’s imminent calving is what it’ll mean for the rest of the shelf—and for the ice currently tethered to land on the Antarctic Peninsula, which can still contribute to sea level rise, albeit probably just a few millimeters. Glaciologists often liken ice shelves to corks in a champagne bottle: remove them, and all the stuff they’ve bottled up starts to escape. This may be especially true for the Larsen C ice shelf, which appears to be snapping off at two crucial pinning points where land meets ice.

    “We expect this to create a new zone where calving happens more readily, now that we’ve removed these pinning points,” Wagner said. “And when these ice shelves break up, the ice behind surges into the ocean, getting thinner.”

    In other words, Larsen C’s soon-to-be iceberg could be the tip of a much larger, proverbial iceberg, of an entire landscape reshaping itself. The changes glaciologists expect around Larsen C jibe with a bigger-picture pattern of ice retreat across the peninsula, including earlier calving events at the neighboring ice shelves Larsen A and B, which scientists have attributed to rising temperatures.

    Whether or not climate change is playing a direct role in the action on Larsen C, it’s a clearly force to be reckoned with across the Antarctic Peninsula, where average temperatures have risen a staggering 3 degrees Celsius (5.4 degrees Fahrenheit) since pre-industrial times. (Globally-averaged temperatures have risen roughly a single degree Celsius over the same time period.)

    “We may see that one this chunk of [ice] is gone, Larsen C [starts] becoming more vulnerable to climate impacts,” O’Leary said.

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    Bird’s eye view of the Amundsen sea embayment, where major glaciers of the West Antarctic ice sheet empty into the ocean. Pope, Smith, and Kohler glaciers were the focus of this study. Image: NASA/GSFC/SVS

    Most importantly to researchers, the breakup of the Larsen C ice shelf could be a harbinger of what’s to come in other vulnerable parts of West Antarctica, particularly the Amundsen Sea embayment to the south, where warming waters are already causing the enormous Pine Island and Thwaites glaciers to melt and retreat. A summary of a scientific workshop compiled last year by the National Snow and Ice Data Center warns that “a significant retreat of the Thwaites Glacier system would trigger a wider collapse of most of the West Antarctic Ice Sheet.” That entire ice sheet contains enough water to raise global sea level by 3.3 meters (over ten feet), on a timescale of decades to centuries.

    “This is going to happen on other ice shelves,” Wagner said, adding that NASA and others have a unique opportunity with Larsen C, to study a massive iceberg calving event from satellites, airborne surveys like Operation IceBridge, and ground-based data. “We’re gonna watch how the ice shelf responds mechanically [as it breaks]. Larsen C is how we model what’s going to happen to Thwaites.”

    In other words, far more disturbing than the breakup of the Larsen C ice shelf is what it can tell us about our future.

    See the full article here .

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  • richardmitnick 12:45 pm on January 25, 2017 Permalink | Reply
    Tags: , , , , GIZMODO, , The speed of dark   

    From GIZMODO: “What’s the Speed of Dark?” 

    GIZMOGO pictorial
    GIZMODO
    1.24.17
    Sophie Weiner

    1
    Illustration: Jim Cooke/Gizmodo

    The speed of light is one of the most important constants in physics. First measured by Danish astronomer Olaus Roemer in 1676, it was Albert Einstein who realized that light sets an ultimate speed limit for our universe, of 186,000 rip-roaring miles per second. But while the immutability of lightspeed is drilled into physics students at a young age, Einstein’s laws also state that all motion is relative, which got us thinking: what’s the speed of light’s nefarious doppleganger, darkness?

    We’re not the first to ask this question (shout out comedian Steven Wright) or take it seriously, but in asking scientists and researchers, we left the interpretation of “darkness” open, eliciting some fascinating responses from experts on black holes and quantum physics. It turns out, darkness could be just as fast as light, or it could be infinitely slower—it all depends on your perspective.

    George Musser

    The speed of dark? The easy answer is that it’s just the speed of light. Switch off the sun and our sky would go dark eight minutes later. But easy is boring! For starters, what we commonly call the “speed of light” is the speed of propagation, and that’s not always the deciding factor. A shadow swoops across the landscape at a speed governed by the object that casts it. For instance, as a lighthouse beacon rotates, it lights up the surroundings at regular intervals. The ground speed of its shadow increases with distance from the lighthouse.

    Go far enough away and the shadow will wash over you faster than the propagation speed of light. (This happens for real in rotating neutron stars in the cosmos, with measurable consequences.) All the speed of light means in this case is that there’s a delay: if the lighthouse points toward you at 12 o’clock, you will see the flash a little later. But that doesn’t affect the pace of events you see at your location.

    While we’re at it, is there even such a thing as darkness? If you did switch off the sun, Earth wouldn’t go completely dark. Light from stars, nebulae, and the big bang would fill the sky. The planet and everything on it, including our bodies, would blaze in the infrared. Depending on how, exactly, you’d managed to switch the sun off, it would keep on glowing for eons. As long as we were able to see, we’d see something. No light detector can register total darkness, because, if nothing else, quantum fluctuations produce tiny flashes of light. Even a black hole, the darkest conceivable object, emits some light. In physics, unlike human affairs, light always chases away dark.

    Darkness isn’t a physical category, but a state of mind. Photons hitting, or not hitting, retinal cells may trigger the experience, but do not explain the subjective experience of darkness, any more than the length of waves explains the experience of color or sound. Our conscious experience changes from moment to moment, but the individual frames of that experience are timeless. In that sense, darkness has no speed.

    And what about speed in general—is there such a thing? It presupposes a framework of space, and scientists see phenomena in quantum physics where spatial concepts seem not to apply—suggesting, to some, that space is derived from a more fundamental level of reality where these is no such as thing as position, distance, or speed. It must be the level that Steven Wright operates on.

    Avi Loeb

    Close to a black hole, matter falls in at a speed that is close to the speed of light. Once it enters the so-called event-horizon of the black holes, nothing can escape. Even light is trapped inside the horizon forever. Hence a black hole can be thought of as the ultimate prison.

    A star like the Sun can be shredded (“spaghettified”) into a stream of gas if it passes too close to a massive black hole, like the one (weighting six billion solar masses) at the center of the Milky Way galaxy.

    As matter falls into the black hole, it often rubs against itself and heats up. As a result it radiates. If the accretion rate is high enough, the force of the radiation flowing out could potentially stop additional matter from falling in. Many of the most massive black holes in the universe, weighting billions of solar masses, are observed to accrete at the maximum possible rate (also called the Eddington limit, after Sir Arthur Eddington who discovered theoretically the maximum radiation output possible for gravity to overcome the radiation force).

    Neil DeGrasse Tyson

    The speed of dark… Consider dark getting erased by light. The light erases it at the speed of light so the speed of dark would be negative the speed of light. If light is a vector, it has magnitude and direction, so… to call it negative means it’s in a negative direction. The dark is receding rather than advancing. I’d call it negative the speed of light.

    Sarah Caudill

    A black hole has gravity so strong that not even light can escape once it has passed the event horizon, an invisible boundary marking the point of no return. Because the black hole has such strong gravity, time dilation will affect observations from outside the strong gravitational field.

    For example, a distant observer watching a glowing object fall into a black hole will see it slow down and fade, eventually becoming so dim it cannot be seen. This observer won’t ever see the object cross the event horizon.

    We can also take the perspective of stuff falling into the black hole, instead of a distant observer. For example, if we take a black hole in the center of a glowing gas cloud, say from a star that has been broken up by passing too close to the black hole, the material will form a flattened disk, known as an accretion disk. This gas will fall into the black hole, but it is not instantaneous. There is a speed limit enforced by the radiation pressure from the hot gas which will fight against the inward force of gravity from the black hole. As the gas falls into the black hole, the black hole grows in size. If a black hole that is 10 times as massive as our Sun is accreting at the maximum allowed rate, in about a billion years it could have reached 100 million times the mass of our Sun.

    David Reitze

    Basically, it depends on whether you’re the matter being consumed by the infinite abyss of a black hole or you’re far enough away to be a dispassionate observer watching someone else falling into the infinite abyss. If you happen to be the unlucky matter falling in, the speed is potentially very large, in principle approaching the speed of light.

    If you’re the observer and you’re far enough away, the speed with which matter is consumed is dramatically slowed down due to an effect known as gravitational time dilation—clocks run slower in gravitational fields, and much slower in the immense gravitational fields near the event horizon of the black hole. By ‘far enough away’, I mean that in your local reference frame, your stationary relative to the black hole (i.e, not getting sucked in) and your local clock is not affected by the gravitational field of the black hole. In fact, to the far away person it will take an infinite amount of time for something to travel to the event horizon of the black hole.

    Niayesh Afshordi

    I believe the speed “of dark” is infinite! In classical physics, the vast darkness of space could be just empty vacuum. However, we have learnt from quantum mechanics that there is no real dark or empty space. Even where there is no light that we can see, electromagnetic field can fluctuate in and out of existence, especially on small scales and short times. Even gravitational waves, the ripples in the geometry of spacetime that were recently observed by the LIGO observatory, should have these quantum fluctuations.

    The problem is that the gravity of these quantum ripples is infinite. In other words, currently there is no sensible theory of quantum gravity that people could agree on. One way to avoid the problem is if the speed “of dark”, i.e. the quantum ripples, goes to infinity (or becomes arbitrarily big) on small scales and short times. Of course, that’s only one possibility, but is a simple (and my favourite) way to understand big bang, black holes, dark energy, and quantum gravity.

    See the full article here .

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  • richardmitnick 9:30 am on January 9, 2017 Permalink | Reply
    Tags: After More Than 100 Years, , California's Iconic Tunnel Tree Is No More, GIZMODO, The Pioneer Cabin Tree, Yosemite’s Wawona Tunnel Tree   

    From GIZMODO: “After More Than 100 Years, California’s Iconic Tunnel Tree Is No More” 

    GIZMOGO pictorial

    GIZMODO

    1.9.17
    Hudson Hongo

    1
    Pioneer Cabin Tree. http://www.stancoe.org

    The Pioneer Cabin Tree, a giant sequoia in Calaveras Big Trees State Park that was tunneled through in the 1880s, has fallen due to severe winter weather. It was believed to be hundreds of years old.

    2
    Calaveras Big Trees Association

    Since it was first hollowed out in imitation of Yosemite’s Wawona Tunnel Tree, thousands of tourists and vehicles have passed through the sequoia. The Wawona tree was killed by the process and later fell during a storm in the 1960s, but the Pioneer Cabin Tree clung on, showing signs of life well into the 21st century.

    2
    Yosemite’s Wawona Tunnel Tree. Credit: https://www.flickr.com/photos/94207108@N02/24177368222

    “The pioneer cabin tree was chosen because of its extremely wide base and large fire scar,” wrote park interpretive specialist Wendy Harrison in 1990. “A few branches bearing green foliage tell us that this tree is still managing to survive.”

    On Facebook, where the tree’s death was first announced, park visitors shared generations of memories involving the giant sequoia. The Calaveras Big Trees Association, however, offered a simple message about the tree’s return to the earth it sprouted from so many years ago.

    “This iconic and still living tree—the tunnel tree—enchanted many visitors,” wrote the association. “The storm was just too much for it.”

    See the full article here .

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  • richardmitnick 12:54 pm on December 17, 2016 Permalink | Reply
    Tags: GIZMODO, Here's What Would Happen If a Giant Asteroid Struck the Ocean,   

    From GIZMODO: “Here’s What Would Happen If a Giant Asteroid Struck the Ocean” 

    GIZMODO bloc

    GIZMODO

    12.14.16
    Maddie Stone

    1
    Image: Los Alamos National Laboratory

    Seventy percent of Earth’s surface is covered by water, meaning if we were unfortunate enough to be struck by an enormous asteroid, it’d probably make a big splash. A team of data scientists at Los Alamos National Laboratory recently decided to model what would happen if an asteroid struck the sea. Despite the apocalyptic subject matter, the results are quite beautiful.

    Galen Gisler and his colleagues at LANL are using supercomputers to visualize how the kinetic energy of a fast-moving space rock would be transferred to the ocean on impact. The results, which Gisler presented at the American Geophysical Union meeting this week, may come as a surprise to those who grew up on disaster movies like Deep Impact. Asteroids are point sources, and it turns out waves generated by point sources diminish rapidly, rather than growing more ferocious as they cover hundreds of miles to swallow New York.

    The bigger concern, in most asteroid-on-ocean situations, is water vapor.

    “The most significant effect of an impact into the ocean is the injection of water vapor into the stratosphere, with possible climate effects” Gisler said. Indeed, Gisler’s simulations show that large (250 meter-across) rock coming in very hot could vaporize up to 250 metric megatons of water. Lofted into the troposphere, that water vapor would rain out fairly quickly. But water vapor that makes it all the way up to the stratosphere can stay there for a while. And because it’s a potent greenhouse gas, this could have a major effect on our climate.

    Of course, not all asteroids make it to the surface at all. Smaller sized ones, which are much more common in our solar neighborhood, tend to explode while they’re still in the sky, creating a pressure wave that propagates outwards in all directions. Gisler’s models show that when these “airburst” asteroids strike over the ocean, they produce less stratospheric water vapor, and smaller waves. “The airburst considerably mitigates the effect on the water,” he said.

    Overall, Gisler says, asteroids over the ocean pose less of a danger to humans than asteroids over the land. There’s one big exception, however, and that’s asteroids that strike near a coastline.

    “An impact or an airburst [near] a populated shore will be very dangerous,” Gisler said. In that case, the gigantic, city-devouring tsunami every B-list disaster movie has primed you for might actually arrive.

    See the full article here .

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  • richardmitnick 2:11 pm on September 30, 2016 Permalink | Reply
    Tags: , , GIZMODO, Massive Earthquake Along the San Andreas Fault Is Disturbingly Imminent,   

    From GIZMODO: “Massive Earthquake Along the San Andreas Fault Is Disturbingly Imminent” 

    GIZMODO bloc

    GIZMODO

    9.30.16
    George Dvorsky

    1
    The USGS estimates a 1 in 100 chance of the San Andreas Fault rupturing between now and October 4. (Image: SanAndreasFault.org)

    A series of quakes under the Salton Sea may be a signal that the San Andreas Fault is on the verge of buckling. For the next few days, the risk of a major earthquake along the fault is as high as 1 in 100. Which, holy crap.

    The United States Geological Survey has been tracking a series of earthquakes near Bombay Beach, California. This “earthquake swarm” is happening under the Salton Sea, and over 140 events have been recorded since Monday September 26. The quakes range from 1.4 to 4.3 in magnitude, and are occurring at depths between 2.5 to 5.5 miles (4 to 9 km).

    2
    Quakes recorded under the Salton Sea on September 27, 2016. (Image: USGS)

    For seismologists, these quakes could represent some seriously bad news. The swarm is located near a set of cross-faults that are connected to the southernmost end of the San Andreas Fault. Troublingly, some of these cross-faults could be adding stress to the San Andreas Fault when they shift and grind deep underground. Given this region’s history of major earthquakes, it’s got some people a bit nervous.

    Calculations show that from now until October 4, the chance of a magnitude 7 or greater earthquake happening along the Southern San Andreas Fault is as high as 1 in 100, and as low as 1 in 3,000. On the plus side, the likelihood of it happening decreases with each passing day. These estimates are based on models developed to assess the probabilities of earthquakes and aftershocks in California.

    “Swarm-like activity in this region has occurred in the past, so this week’s activity, in and of itself, is not necessarily cause for alarm,” cautions the USGS.

    That being said, this is only the third swarm that has been recorded in this area since sensors were installed in 1932, and it’s much worse than the ones recorded in 2001 and 2009. This particular stretch of the San Andreas Fault hasn’t ruptured since 1680, and given that big quakes in this area happen about once every 150 to 200 years, this fault line is considerably overdue.

    A big fear is that the rupturing of the southern portion of the San Andreas fault could cause a domino effect along the entire stretch, cracking the fault from Imperial County through to Los Angeles County. Another possibility is that the Salton Sea swarm could cause the nearby San Jacinto fault system to rupture, which would in turn trigger the collapse of the San Andreas Fault.

    Should the Big One hit, it won’t be pretty. Models predict a quake across the southern half of California with a magnitude around 7.8. Such a quake would cause an estimated 1,800 deaths, 50,000 injuries, and over $200 billion in damage.

    But as the USGS researchers point out, this is far from an inevitability. The swarm under the Salton Sea may subside, or fail to influence the gigantic fault nearby. Moreover, the estimates provided by the scientists are exactly that—estimates. The science of earthquake prediction is still very much in its infancy, and these models are very likely crunching away with insufficient data. No need to panic just yet.

    See the full article here .

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  • richardmitnick 9:11 pm on September 12, 2016 Permalink | Reply
    Tags: , , GIZMODO,   

    From GIZMODO: “We Were Wrong About Where the Moon Came From” 

    GIZMODO bloc

    GIZMODO

    9.12.16
    Ria Misra

    1
    Artist’s concept of moon-Earth crash (Image: Dana Berry/SwRI)

    The moon is our almost constant frenemy in space, lighting our nights and spoiling our star-views in equal turns. But now, new measurements from Apollo-era moon rocks suggest that the moon and Earth had a much more savage past than we knew.

    A new paper out today in Nature says that the moon formed as a result of a more violent space collision than previously believed. Since the 1970s, many researchers have championed a theory in which the moon was created from thrown-off debris when a Mars-sized body grazed Earth in a relatively low-contact collision. Instead, the researchers say new evidence shows that the impact was more “like a sledgehammer hitting a watermelon.”

    The old theory of the moon’s origin—in which it formed from debris from a grazing collision—neatly explains both the moon’s size and orbital position. But a test on some lunar rocks from the Apollo mission revealed something odd which that theory couldn’t explain.

    “We’re still remeasuring the old Apollo samples from the the ‘70s, because the tech has been developing in recent years. We can measure much smaller differences between Earth and the moon, so we found a lot of things we didn’t find in the 1970s,” Kun Wang, an assistant professor at Washington University who is the lead author of the paper told Gizmodo. “The old models just could not explain the new observations.”

    If the four-decade old theory were correct, then researchers would expect to find that well over half of the moon’s material had come from that Mars-sized body that scraped Earth to form the moon. But the researchers weren’t finding signs of that in the samples; instead, chemical analyses on the samples were returning isotopic compound readings that were nearly identical.

    They started to do more and more advanced tests to try and pinpoint any differences in the signatures. They finally found one—but one that suggested that the samples’ origins were even more tightly connected than previously expected.

    The isotope signatures were the same, except for more of a heavy-potassium isotope in the lunar samples which would have required incredibly hot temperatures to separate out. A violent collision between the Earth and the Mars-sized impactor could have caused those incredibly high temperatures. In this model, the temperatures were so high and the force so powerful that the impactor and even much of Earth vaporized on contact. That vapor then expanded out over an area 500 times the size of the Earth before finally cooling and condensing into the moon.

    “We need a much, much bigger impact to form a moon according to our study,” explained Wang. “The giant impact itself should be called extremely giant impact. The amount of energy required isn’t even close.”

    This new data doesn’t just change our conception of how the moon was formed, though. It also suggests an early solar system that was much more volatile than we knew—and it could be just the beginning of what new analyses on old lunar samples could teach us.

    “Everything we know about the early solar system is from our study of meteorites and lunar samples, all those really really old rocks,” said Wang. “It has changed our understanding of the early solar system, it’s much more violent than we thought.”

    The researchers will continue to study the Apollo lunar samples to try and pull yet more clues from them. Even now, they suspect that these samples that we’ve been holding on to for decades could have more secrets to reveal.

    See the full article here .

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  • richardmitnick 4:39 pm on August 30, 2016 Permalink | Reply
    Tags: , , GIZMODO, ,   

    From GIZMODO: “How We’ll Get Our First Big Clue About Life on Proxima b” 

    GIZMODO bloc

    GIZMODO

    1
    Artist’s concept of Proxima b orbiting Proxima Centauri. (Image: ESO./L. Calçada/Nick Resigner)

    Last week, astronomers announced that our nearest neighboring star hosts an Earth-sized planet in the habitable zone—an exciting prospect for alien life, and a possible second home for humanity. But before we assemble the interstellar welcoming party to greet our cosmic neighbors, we need to figure out whether Proxima b is capable of supporting life at all. Thanks to the James Webb Space Telescope, that question could be answered in less than three years.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    “It is controversial whether or not life can exist in low mass star systems like Proxima Centauri,” Harvard astronomer Avi Loeb told Gizmodo. “Some people have argued that such planets cannot have an atmosphere.”

    That’s why Loeb, along with Harvard astronomer Laura Kreidberg, has just submitted a paper to Astrophysical Journal Letters describing how we can use the JWST—the highly-anticipated successor to Hubble that launches in 2018—to answer this critical question within just a few days of observation.

    The concern that Proxima b may be a dead, airless world stems from the fact that it orbits its dim red dwarf star, Proxima Centauri, at a distance of just 4.6 million miles. (Earth, for comparison, is 93 million miles from the Sun.) This tight orbit affords Proxima b enough sunlight for Earth-like temperatures and liquid water, but it also subjects the planet to powerful, atmosphere-stripping solar winds. What’s more, it virtually ensures that Proxima b is tidally locked, with a permanent dayside and a permanent nightside. Unfortunately, models suggest that the atmospheres of tidally locked planets may be prone to sudden collapse, as volatile gases freeze out on the nightside.

    But atmospheres can also be replenished through volcanic activity, and on planets with strong magnetic fields, they’re less likely to escape. Since we know nothing of Proxima b’s volcanic activity or magnetic field strength, we can’t even make an educated guess about its prospects of having an atmosphere. But we’re dying to know, because an atmosphere means oceans are possible, and the two together mean life is.

    That’s where the JWST comes in. As Loeb and Kreidberg discuss in their paper, the key to sniffing out Proxima b’s atmosphere lies in the planet’s infrared heat signature. And it just so happens that Hubble’s successor is highly attuned to the infrared part of the spectrum.

    “As Proxima b moves about its star, there is no day-night variation,” Loeb explained. “The day side is hot and the night side is cold. But the temperature difference between day and night depends on whether the planet is bare rock, or if it has an atmosphere or ocean, because these redistribute heat.”

    In other words, the temperature difference between Proxima b’s day side and its night side will be larger if there is no atmosphere. In fact, the day side will re-emit all of the energy it absorbs from Proxima Centauri as a blackbody, and we can calculate exactly how much blackbody radiation there should be. The night side, on the other hand, will be hell frozen over.

    If the temperature difference between day and night is less extreme, we can infer the presence of an atmosphere. Conveniently, it won’t take long for the JWST to measure IR emissions from both faces of Proxima b as it orbits its star—an entire year only takes 11.2 Earth days.

    If Proxima b does have an atmosphere, the next step will be figuring out what it’s made of. We’ll specifically want to look for things like oxygen, water vapor, and methane, which could indicate habitable conditions if not active biological processes. This, however, requires us to catch starlight as it bounces off or filters through the planet’s atmosphere—an extraordinarily difficult thing to do. While the JWST might be able to detect a few compounds including ozone, full atmospheric analysis will have to wait for future ground-based observatories like the Extremely Large Telescope, which is expected to see first light in the mid-2020s.

    “The important thing is that in a couple of years, we should be able to start learning about the atmosphere [of Proxima b],” Loeb said. “If there is one, it’s quite likely there’d be a call for a special mission to study just this planet.”

    As we continue building the tools to study Proxima b from Earth, Loeb is already thinking about how we might pay the planet a visit. He’s chairing the advisory committee for Breakthrough Starshot, a billionaire-backed effort to develop tiny, laser-propelled spacecraft that can travel at up to 20 percent the speed of light. While Breakthrough Starshot was initially packaged as a voyage to the nearby binary star system Alpha Centauri, the discovery of Proxima b changes everything.

    “I think it’s extremely important, psychologically, to have a target,” Loeb said. “If you ask a person to build a ship without knowing where it will sail, it’s quite different than if you have a destination in mind. The fact that we now have a target, in the habitable zone, is very exciting.”

    See the full article here .

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