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  • richardmitnick 9:24 am on September 17, 2019 Permalink | Reply
    Tags: , , , , , , , Ringing black holes,   

    From Science News: “Gravitational waves from a ringing black hole support the no-hair theorem” 

    From Science News

    September 16, 2019
    Emily Conover

    General relativity suggests the spacetime oddities can be fully described by their mass and spin.

    1

    After two black holes collide and meld into one, the new black hole “rings” (illustrated), emitting gravitational waves before settling down into a quiet state. M. Isi/MIT, NASA

    For black holes, it’s tough to stand out from the crowd: Donning a mohawk is a no-no.

    Ripples in spacetime produced as two black holes merged into one suggest that the behemoths have no “hair,” scientists report in the Sept. 13 Physical Review Letters. That’s another way of saying that, as predicted by Einstein’s general theory of relativity, black holes have no distinguishing characteristics aside from mass and the rate at which they spin (SN: 9/24/10).

    “Black holes are very simple objects, in some sense,” says physicist Maximiliano Isi of MIT.

    Detected by the Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, in 2015, the spacetime ripples resulted from a fateful encounter between two black holes, which spiraled around each other before crashing together to form one big black hole (SN: 2/11/16).

    MIT /Caltech Advanced aLigo

    In the aftermath of that coalescence, the newly formed big black hole went through a period of “ringdown.” It oscillated over several milliseconds as it emitted gravitational waves, similar to the way a struck bell vibrates and makes sound waves before eventually quieting down.

    Reverberating black holes emit gravitational waves not at a single frequency, but with additional, short-lived frequencies known as overtones — much like a bell rings with multiple tones in addition to its main pitch.

    Measuring the ringing black hole’s main frequency as well as one overtone allowed the researchers to compare those waves with the prediction for a hairless black hole. The results agreed within 20 percent.

    That result still leaves some wiggle room for the no-hair theorem to be proved wrong. But, “It’s a clear demonstration that the method works,” says physicist Leo Stein of the University of Mississippi in Oxford, who was not involved with the research. “And hopefully the precision will increase as LIGO improves.”

    The researchers also calculated the mass and spin of the black hole, using only waves from the ringdown period. The figures agreed with the values estimated from the entire event — including the spiraling and merging of the original two black holes — and so reinforced the idea that the resulting black hole’s behavior was determined entirely by its mass and spin.

    But just as a mostly bald man may sport a few strands, black holes could reveal some hair on closer inspection. If they do, that might lead to a solution to the information paradox, a puzzle about what happens to information that falls into a black hole (SN: 5/16/14). For example, in a 2016 attempt to resolve the paradox, physicist Stephen Hawking and colleagues suggested that black holes might have “soft hair” (SN: 4/3/18).

    “It could still be that these objects have more mysteries to them that will only be revealed by future, more sensitive measurements,” Isi says.

    See the full article here .


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  • richardmitnick 8:45 am on September 17, 2019 Permalink | Reply
    Tags: "Explainer: what happens when magnetic north and true north align?", Agonic lines, Angle of declination, Geographic north, ,   

    From CSIROscope: “Explainer: what happens when magnetic north and true north align?” 

    CSIRO bloc

    From CSIROscope

    17 September 2019
    Paul Wilkes

    1
    Very rarely, depending on where you are in the world, your compass can actually point to true north. Image: Shutterstock

    At some point in recent weeks, a once-in-a-lifetime event happened for people at Greenwich in the United Kingdom.

    Magnetic compasses at the historic London area, known as the home of the Prime Meridian, were said to have pointed directly at the north geographic pole for the first time in 360 years.

    This means that, for someone at Greenwich, magnetic north (the direction in which a compass needle points) would have been in exact alignment with geographic north.

    Geographic north (also called “true north”) is the direction towards the fixed point we call the North Pole.

    Magnetic north is the direction towards the north magnetic pole, which is a wandering point where the Earth’s magnetic field goes vertically down into the planet.

    The north magnetic pole is currently about 400km south of the north geographic pole, but can move to about 1,000km away.

    2
    The lines of the Earth’s magnetic field come vertically out of the Earth at the south magnetic pole and go vertically down into the Earth at the north magnetic pole. Image: Nasky/Shutterstock

    How do the norths align?

    Magnetic north and geographic north align when the so-called “angle of declination”, the difference between the two norths at a particular location, is 0°.

    Declination is the angle in the horizontal plane between magnetic north and geographic north. It changes with time and geographic location.

    On a map of the Earth, lines along which there is zero declination are called agonic lines. Agonic lines follow variable paths depending on time variation in the Earth’s magnetic field.

    3
    The declination angle varies between -90° and +90°.

    Currently, zero declination is occurring in some parts of Western Australia, and will likely move westward in coming years.

    That said, it’s hard to predict exactly when an area will have zero declination. This is because the rate of change is slow and current models of the Earth’s magnetic field only cover a few years, and are updated at roughly five-year intervals.

    At some locations, alignment between magnetic north and geographic north is very unlikely at any time, based on predictions.

    4
    Locations on this 2019 map with a green contour line have zero declination. Lines along which declination is zero are called agonic lines.

    The ever-changing magnetic poles

    Most compasses point towards Earth’s north magnetic pole, which is usually in a different place to the north geographic pole. The location of the magnetic poles is constantly changing.

    Earth’s magnetic poles exist because of its magnetic field, which is produced by electric currents in the liquid part of its core. This magnetic field is defined by intensity and two angles, inclination and declination.

    The relationship between geographic location and declination is something people using magnetic compasses have to consider. Declination is the reason a compass reading for north in one location is different to a reading for north in another, especially if there is considerable distance between both locations.

    Bush walkers have to be mindful of declination. In Perth, declination is currently close to 0° but in eastern Australia it can be up to 12°. This difference can be significant. If a bush walker following a magnetic compass disregards the local value of declination, they may walk in the wrong direction.

    The polarity of Earth’s magnetic poles has also changed over time and has undergone pole reversals. This was significant as we learnt more about plate tectonics in the 1960s, because it linked the idea of seafloor spreading from mid-ocean ridges to magnetic pole reversals.

    Geographic north

    Geographic north, perhaps the more straightforward of the two, is the direction that points straight at the North Pole from any location on Earth.

    When flying an aircraft from A to B, we use directions based on geographic north. This is because we have accurate geographic locations for places and need to follow precise routes between them, usually trying to minimise fuel use by taking the shortest route. All GPS navigation uses geographic location.

    Geographic coordinates, latitude and longitude, are defined relative to Earth’s spheroidal shape. The geographic poles are at latitudes of 90°N (North Pole) and 90°S (South Pole), whereas the Equator is at 0°.

    An alignment at Greenwich

    For hundreds of years, declination at Greenwich was negative, meaning compass needles were pointing west of true north.

    At the time of writing this article I used an online calculator to discover that, at the Greenwich Observatory, the Earth’s magnetic field currently has a declination just above zero, about +0.011°.

    The average rate of change in the area is about 0.19° per year, which at Greenwich’s latitude represents about 20km per year. This means next year, locations about 20km west of Greenwich will have zero declination.

    It’s impossible to say how long compasses at Greenwich will now point east of true north.

    Regardless, an alignment after 360 years at the home of the Prime Meridian is undoubtedly a once-in-a-lifetime occurrence.

    See the full article here .


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    SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western Australia

    So what can we expect these new radio projects to discover? We have no idea, but history tells us that they are almost certain to deliver some major surprises.

    Making these new discoveries may not be so simple. Gone are the days when astronomers could just notice something odd as they browse their tables and graphs.

    Nowadays, astronomers are more likely to be distilling their answers from carefully-posed queries to databases containing petabytes of data. Human brains are just not up to the job of making unexpected discoveries in these circumstances, and instead we will need to develop “learning machines” to help us discover the unexpected.

    With the right tools and careful insight, who knows what we might find.

    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

     
  • richardmitnick 8:16 am on September 17, 2019 Permalink | Reply
    Tags: , , , , Professor Martina Stenzel, ,   

    From University of New South Wales: Women in STEM-“UNSW scientist first woman honoured with top chemistry prize” Professor Martina Stenzel 

    U NSW bloc

    From University of New South Wales

    17 Sep 2019
    Lucy Carroll

    Professor Martina Stenzel is the first woman in almost 90 years to be awarded the Royal Society of NSW’s Liversidge Medal.

    1

    One of the world’s leading experts in polymer chemistry, UNSW Sydney Scientia Professor Martina Stenzel, is the first woman to receive the Royal Society of NSW’s Liversidge Medal.

    The top science prize, which has been running since 1931, recognises Australian scientists who have made an outstanding contribution to chemistry research.

    Professor Stenzel, from UNSW Science’s School of Chemistry, is widely regarded as a global pioneer in the application of novel polymer architectures. By developing chemical techniques for new polymer architectures, Professor Stenzel is creating ‘smart’ nanoparticles for drug delivery that are revolutionising the way disease is targeted and treated.

    Her work focuses on the fundamental processes that underpin nanoparticle design to make them suitable for the delivery of proteins, DNA or metal-based drugs to treat cancer – specifically ovarian and pancreatic cancer.

    “The Liversidge Medal is such an established prize and it is truly wonderful to be recognised by this enduring and respected scientific academy,” Professor Stenzel said. “I hope it will encourage more women to enter the fields of chemistry and physics, two natural sciences where female scientists have traditionally been very few and far between.”

    As Co-Director at UNSW’s Centre for Advanced Macromolecular Design, Professor Stenzel leads a team of 20 researchers working to combine synthetic polymers with nature’s building blocks such as carbohydrates, peptides and proteins. The team of researches work at the intersection of polymer science, nanoparticle design and medicine.

    The creation and adaptation of nanoparticles for various biomedical applications is the focus of Professor Stenzel’s current research. By designing nanoparticles of different shapes, sizes and surface functionalities the nanoparticles can then be “loaded” with various drugs, mimicking a water-filled sponge.

    “The beautiful thing about nanoparticles is that they can be modified in endless ways,” Professor Stenzel said. “We are trying to better understand the physical properties of these drug-loaded nanoparticles as it is directly linked to the biological activity. The aim is to create nanoparticles with the right properties that can invade cancer cells but not attack healthy cells.

    “It is incredibly exciting to be able to work more closely with medical researchers, including the ovarian cancer researcher UNSW’s Associate Professor Caroline Ford and pancreatic researchers Associate Professor Joshua McCarroll and Associate Professor Phoebe Phillips to test the ability of patented protein-based nanoparticles to help treat some of the most challenging cancers.”

    Professor Stenzel said that while nanoparticles were most commonly used in cancer treatment, they could potentially be so used for treatment of many other diseases, including Parkinson’s disease, Alzheimer’s, diabetes and infectious diseases.

    Professor Stenzel is a recipient of the LeFevre Medal from the Australian Academy of Science, the H.G. Smith Medal of the Royal Australian Chemical Institute RACI and in 2018 was elected to the Australian Academy of Science.

    The Liversidge Lecture, awarded every two years, is given on the recommendation of the Royal Australian Chemical Institute (RACI). UNSW Scientia Professor Justin Gooding was the last recipient of the award in 2016.

    Professor Stenzel will give the Liversidge Lecture in February 2020. The lectures are published in the Journal and Proceedings of the Society.

    See the full article here.


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    U NSW Campus

    Welcome to UNSW Australia (The University of New South Wales), one of Australia’s leading research and teaching universities. At UNSW, we take pride in the broad range and high quality of our teaching programs. Our teaching gains strength and currency from our research activities, strong industry links and our international nature; UNSW has a strong regional and global engagement.

    In developing new ideas and promoting lasting knowledge we are creating an academic environment where outstanding students and scholars from around the world can be inspired to excel in their programs of study and research. Partnerships with both local and global communities allow UNSW to share knowledge, debate and research outcomes. UNSW’s public events include concert performances, open days and public forums on issues such as the environment, healthcare and global politics. We encourage you to explore the UNSW website so you can find out more about what we do.

     
  • richardmitnick 7:58 am on September 17, 2019 Permalink | Reply
    Tags: "Using a data cube to assess changes in the Earth system", , , , Earth System Data Lab,   

    From European Space Agency: “Using a data cube to assess changes in the Earth system” 

    ESA Space For Europe Banner

    From European Space Agency

    16 September 2019

    1
    Changing Arctic productivity
    Derived from FLUXCOM land–atmosphere energy fluxes, hosted on the Earth System Data Lab
    In parts of the Arctic tundra, temperatures are increasing rapidly as a result of climate change. This has resulted in complex changes in plant communities, with satellite data showing that some parts of the Arctic are ‘greening’ whilst other areas are said to be ‘browning’. Using the Earth System Data Lab, scientists are looking at components such as rock or soil types to understand changes in plant productivity in the Arctic, beyond just temperature. The image shows changes in mean maximum gross primary productivity across five years between 2001–2005 and 2011–2015 at high latitudes (>60°N). Notable changes in gross primary productivity are evident including large increases in northern Canada, and decreases in parts of Alaska and Siberia, highlighting the heterogeneous pattern of productivity change over time.

    Researchers all over the world have a wealth of satellite data at their fingertips to understand global change, but turning a multitude of different data into actual information can pose a challenge. Using examples of Arctic greening and drought, scientists at ESA’s ɸ-week showed how the Earth System Data Lab is making this task much easier.

    ESA’s Earth System Data Lab is a new virtual lab to access a wide array of Earth observations across space, time and variables. It consists of two elements: the data cube and an interface to execute different analyses on the data cube.

    Last year, ESA put out a call – an Early Adopters Call – for young researchers to explore information from data streams produced by several international scientific teams to help shape the future of the Earth System Data Lab.

    Some of these young researchers using the Earth System Data Lab were at ESA’s ɸ-week presenting their findings on, for example, Arctic greening and drought.

    In parts of the Arctic tundra, temperatures are increasing rapidly as a result of climate change. This has resulted in complex changes in plant communities, with satellite data showing that some parts of the Arctic are ‘greening’ whilst other areas are said to be ‘browning’. Understanding changes at high latitudes is crucial as they could be used to predict changes in other places that haven’t yet warmed as much.

    Oliver Baines, from the University of Nottingham in the UK, said, “The work I presented examines whether the inclusion of geodiversity components, such as rock or soil types, can improve our understanding of changes in plant productivity in the Arctic, beyond considering just temperature.

    “Using the Earth System Data Lab, we have been able to examine these relationships to identify the role of abiotic nature at a much larger scale than before.”

    By providing a set of pre-processed datasets all in one place, the virtual lab has made it easier to access, manipulate and analyse different variables including climate, gross primary productivity related to photosynthesis, aerosols and sea-surface temperatures.

    Mr Baines continues, “The hope is that by including a wider variety of abiotic nature, our understanding of changes in the Arctic can be improved and, subsequently, that any future predictions of Arctic environmental change can be refined.”

    The data cube can reveal where big anomalies occur. In the light of the last two summers when Europe was hit by unprecedented heatwaves, and this year’s devastating fires in the Amazon, the relevance of the work being carried out through the virtual lab becomes clear.

    Miguel Mahecha, from the Max Planck Institute for Biogeochemistry in Germany, said, “Only if we succeed in putting these impacts into a global perspective, will we be able to objectively judge their impacts. And, even more importantly, understand and anticipate their impacts under future climate conditions.”

    However, while the question of weather extremes is an issue, long-term change and climate change are a global concern.

    “Large parts of South America, for example, have become less productive and drier over the past decade. But there is a need to understand if this is a real change or just decadal variability. And, the Earth System Data Lab is helping us with this research,” continued Mr Mahecha.

    Another Early Adopter, Karina Winkler from the Karlsruhe Institute of Technology, Germany, is working on using reconstructed land-use data and multiple satellite-derived variables from the Earth System Data Lab. The objective of the project is to model biomass distribution by using deep learning – which shows the potential of reconstructing changes of above-ground biomass over time and at a global scale.

    ESA’s ɸ-week gave researchers the unique opportunity to share and discuss their research and reflect on the value of this new data cube they have to hand.

    See the full article here .


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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large

     
  • richardmitnick 7:21 am on September 17, 2019 Permalink | Reply
    Tags: "New NASA Mission To Investigate Europa For Signs Of Life", , , , , , NASA’s Clipper mission   

    From Ethan Siegel: “New NASA Mission To Investigate Europa For Signs Of Life” 

    From Ethan Siegel
    Sep 16, 2019

    1
    Varied terrain on Europa. Credit: NASA/JPL-Caltech/SETI Institute

    NASA/Europa Clipper annotated

    NASA’s Clipper mission to Jupiter’s second (of four) large moons, Europa, will perform at least 45 close flybys of its main target, monitoring its surface, subsurface ocean, and atmosphere for a series of signatures that could reveal information vital to assessing Europa as a location for potential habitability or biological activity within our own Solar System. (NASA/JPL-CALTECH)




    Is there life beyond Earth, even in our Solar System? This mission might be humanity’s best hope of finding it.

    The biggest question facing humanity might be, “Does life exists beyond Earth?”

    1
    When a planet transits in front of its parent star, some of the light is not only blocked, but if an atmosphere is present, filters through it, creating absorption or emission lines that a sophisticated-enough observatory could detect. If there are organic molecules or large amounts of molecular oxygen, we might be able to find that, too. It’s important that we consider not only the signatures of life we know of, but of possible life that we don’t find here on Earth. (ESA / DAVID SING)

    Planet transit. NASA/Ames

    Other solar systems might possess advanced or planet-altering biological activity, but simple life could exist right here.

    2
    Scanning electron microscope image at the sub-cellular level. While DNA is an incredibly complex, long molecule, it is made of the same building blocks (atoms) as everything else. To the best of our knowledge, the DNA structure that life is based on predates the fossil record. The longer and more complex a DNA molecule is, the more potential structures, functions, and proteins it can encode. (PUBLIC DOMAIN IMAGE BY DR. ERSKINE PALMER, USCDCP)

    In our own Solar System, eight different worlds might be home to unicellular life.

    3
    Among the moons in our Solar System, the largest are Ganymede and Titan (the only moons larger than a planet: Mercury), followed in size by Callisto, Io. the Moon, Europa, and Triton. Along with Pluto, Eris, the Sun and the major planets, these are the only worlds in the Solar System larger than 1,000 km in radius. (NASA, VIA WIKIMEDIA COMMONS USER BRICKTOP; EDITED BY WIKIMEDIA COMMONS USERS DEUAR, KFP, TOTOBAGGINS)

    Europa, among the Solar System largest moons, might experience the most life-friendly conditions.

    All life:

    harvests and metabolizes energy/resources,
    responds to external stimuli,
    grows and adapts,
    and reproduces.

    3
    Acidobacteria, like the example shown here, are likely some of the first photosynthetic organisms of all. They have no internal structure or membranes, loose, free-floating DNA, and are anoxygenic: they do not produce oxygen from photosynthesis. These are prokaryotic organisms that are very similar to the primitive life found on Earth some ~2.5–3 billion years ago. (US DEPARTMENT OF ENERGY / PUBLIC DOMAIN)

    While liquid oceans cover 70% of our surface, diminutive Europa has more water than planet Earth.

    4
    Based on the data collected by Galileo, the previous generation of NASA orbiter to study the Jovian system, we learned that Europa contains more water than all of planet Earth, combined, despite being much physically smaller and less massive in size. This water should exist in the liquid phase beneath the surface ice, providing a potential location for life to arise and thrive. (KEVIN HAND (JPL/CALTECH), JACK COOK (WOODS HOLE OCEANOGRAPHIC INSTITUTION), HOWARD PERLMAN (USGS))

    NASA/Galileo 1989-2003

    Beneath a thick layer of water-ice, Europa’s interior experiences high pressures and temperatures.

    5
    Scientists are all but certain that Europa has an ocean underneath its icy surface, but they do not know how thick this ice might be. This artist concept illustrates two possible cut-away views through Europa’s ice shell. In both, heat escapes, possibly volcanically, from Europa’s rocky mantle and is carried upward by buoyant oceanic currents, but the details will be different and will lead to different observable signatures for the instruments aboard NASA’s Clipper. (NASA/JPL/MICHAEL CARROLL)

    Nearby, massive Jupiter exerts tidal forces on Europa, heating its core while shearing and cracking its icy surface.

    The internal heat melts Europa’s pressurized ice, creating a deep, liquid ocean.

    6
    This cutaway of Jupiter’s 4th largest moon, Europa. shows the internal core and rocky mantle, heated by the tidal forces exerted by Jupiter, surrounded by a large, thick layer of water. Beneath the icy surface, once the pressure and temperature reach a critical level, the water becomes liquid, meaning there must be an ocean beneath this icy crust. (KELVINSONG / WIKIMEDIA COMMONS)

    Hydrothermal vents should line the seafloor: where energy gradients could enable life.

    7
    Deep under the sea, around hydrothermal vents, where no sunlight reaches, life still thrives on Earth. How to create life from non-life is one of the great open questions in science today, but if life can exist down here, perhaps undersea on Europa or Enceladus, there’s life, too. It will be more and better data, most likely collected and analyzed by experts, that will eventually determine the scientific answer to this mystery. (NOAA/PMEL VENTS PROGRAM)

    In 2023, a new NASA mission — the Europa Clipper — will investigate Europa for biosignatures.

    8
    Europa’s crust is largely made up of blocks, which scientists think once broke apart, fragmented, and ‘rafted’ their way into their current configuration. As Europa also possesses a magnetic field, the geologic data strongly supports the idea that Europa contains a deep subsurface ocean, with the reddish-brown areas (in assigned colors) showcasing non-ice material that is thought to result from geologic activity. (NASA/GALILEO/JPL/UNIVERSITY OF ARIZONA)

    This orbiter will utilize nine instruments to investigate Europa’s oceans and atmosphere.

    9
    NASA’s Clipper mission will undertake an orbital path that uses the gravitation of Jupiter and its other many moons to create a series of flybys that give global coverage of Europa under different seasonal and day/night conditions. Measuring time-variations in the results returned by the instruments will be crucial to uncovering all the potential bio-hints that Europa might have to offer. (NASA / JPL-CALTECH)

    Dozens of flybys will reveal their compositions, temperatures, depths, salinities, time-variations, etc.

    With life teeming beneath Earth’s Antarctic ices, Europa may be humanity’s best hope for discovering extraterrestrial life.

    10
    Scenes such as ice, stalactices, icebergs and liquid water are extrememly common in Antarctica. Sources of heat from beneath Earth’s surface create subsurface liquid water ‘lakes’ beneath the Antarctic ice, and living organisms exist and thrive in that environment. Perhaps, beneath the icy ocean of Europa, a similar story will emerge. (Delphine AURES/Gamma-Rapho via Getty Images)

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 10:09 pm on September 16, 2019 Permalink | Reply
    Tags: , , , , ,   

    From Fermi National Accelerator Lab: “Finding the missing pieces in the puzzle of an antineutrino’s energy” 

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    September 16, 2019
    Andrew Olivier

    Charged particles, like protons and electrons, can be characterized by the trails of atoms these particles ionize. In contrast, neutrinos and their antiparticle partners almost never ionize atoms, so their interactions have to be pieced together by how they break nuclei apart.

    But when the breakup produces a neutron, it can silently carry away a critical piece of information: some of the antineutrino’s energy.

    Fermilab’s MINERvA collaboration recently published a paper [Phys.Rev.D] to quantify the neutrons produced by antineutrinos interacting on a plastic target.

    FNAL MINERvA front face Photo Reidar Hahn

    The way antineutrinos change between their various types could help explain why the modern universe is dominated by matter. The most promising model of how this behavior relates particles and antiparticles depends on antineutrino energy. However, neutrons can leave holes in the puzzle of an antineutrino’s identity because they carry away energy and are produced in different quantities by neutrinos and antineutrinos. This MINERvA result is aimed at improving predictions of how neutrons could affect current and future neutrino experiments, including the international Deep Underground Neutrino Experiment, hosted by Fermilab.

    SURF-Sanford Underground Research Facility, Lead, South Dakota, USA


    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    3
    The MINERvA detector at Fermilab helps scientists analyze neutrino interactions with atomic nuclei. Photo: Reidar Hahn

    In this study, MINERvA looked for antineutrino interactions that produce neutrons. The antineutrino interactions that MINERvA studies look like one or more trails of ionized atoms all pointing back to a single nucleus. Unlike charged particles, neutrons can travel many tens of centimeters from an antineutrino interaction before being detected. So, the MINERvA collaboration characterized neutron activity as pockets of ionized atoms spatially isolated from both charged particle tracks and the interaction point.

    An antineutrino interaction can produce other types of neutral particles, which can fake a neutron interaction, and charged particles, which can confuse a neutron counting measurement by themselves ejecting neutrons from nuclei. In addition, when these charged particles have low momentum, they can end up in a mass of ionization too close to the interaction point to be counted separately that also masks evidence for neutral particles. So, neutrons can be counted more accurately in antineutrino interactions that produce few additional particles. MINERvA scientists used conservation of momentum calculations to avoid interactions that produced many charged particles.

    4
    This graphic illustrates a neutrino interaction in the MINERvA detector. The rectangular box highlights the spot where a neutrino interacted inside the detector. The square box just above it highlights the appearance of a neutron resulting from the neutrino interaction. Image: MINERvA

    Other experiments’ measurements of neutrons from antineutrinos have waited for each neutron to lose most of its energy before it can be counted. However, neutrons from MINERvA’s antineutrino sample have enough energy to knock other neutrons out of nuclei they collide with. This chain reaction changes both the original neutrons’ energies and the number of neutrons detected. This result focuses on signs of neutrons within tens of nanoseconds of an antineutrino interaction.

    By understanding neutron production in concert with MINERvA’s characterization of antineutrino interactions on many nuclei, future oscillation studies can quantify how undetected neutrons could affect their conclusions about the differences between neutrinos and antineutrinos.

    Andrew Olivier is a physicist at the University of Rochester and member of the MINERvA collaboration.

    See the full here.


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    FNAL Icon

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 9:15 pm on September 16, 2019 Permalink | Reply
    Tags: 21st century alchemy, , , , , Plasmons   

    From Niels Bohr Institute: “Quantum Alchemy: Researchers use laser light to transform metal into magnet” 

    University of Copenhagen

    Niels Bohr Institute bloc

    From Niels Bohr Institute

    16 September 2019

    Mark Spencer Rudner
    Associate Professor
    Condensed Matter Physics
    Niels Bohr Institutet
    rudner@nbi.ku.dk

    Maria Hornbek
    Journalist
    The Faculty of Science
    maho@science.ku.dk
    +45 22 95 42 83

    CONDENSED MATTER PHYSICS: Pioneering physicists from the University of Copenhagen and Nanyang Technological University in Singapore have discovered a way to get non-magnetic materials to make themselves magnetic by way of laser light. The phenomenon may also be used to endow many other materials with new properties.

    1
    Mark Rudner, Niels Bohr Institute, University of Copenhagen

    2
    Asst Prof Justin Song Chien Wen

    The intrinsic properties of materials arise from their chemistry — from the types of atoms that are present and the way that they are arranged. These factors determine, for example, how well a material may conduct electricity or whether or not it is magnetic. Therefore, the traditional route for changing or achieving new material properties has been through chemistry.

    Now, a pair of researchers from the University of Copenhagen and Nanyang Technological University in Singapore have discovered a new physical route to the transformation of material properties: when stimulated by laser light, a metal can transform itself from within and suddenly acquire new properties.

    1

    “For several years, we have been looking into how to transform the properties of a matter by irradiating it with certain types of light. What’s new is that not only can we change the properties using light, we can trigger the material to change itself, from the inside out, and emerge into a new phase with completely new properties. For instance, a non-magnetic metal can suddenly transform into a magnet,” explains Associate Professor Mark Rudner, a researcher at the University of Copenhagen’s Niels Bohr Institute.

    He and colleague Justin Song of Nanyang Technological University in Singapore made the discovery that is now published in Nature Physics. The idea of using light to transform the properties of a material is not novel in itself. But up to now, researchers have only been capable of manipulating the properties already found in a material. Giving a metal its own ‘separate life’, allowing it to generate its own new properties, has never been seen before.

    By way of theoretical analysis, the researchers have succeeded in proving that when a non-magnetic metallic disk is irradiated with linearly polarized light, circulating electric currents and hence magnetism can spontaneously emerge in the disk.

    Researchers use so-called plasmons (a type of electron wave) found in the material to change its intrinsic properties. When the material is irradiated with laser light, plasmons in the metal disk begin to rotate in either a clockwise or counterclockwise direction. However, these plasmons change the quantum electronic structure of a material, which simultaneously alters their own behavior, catalyzing a feedback loop. Feedback from the plasmons’ internal electric fields eventually causes the plasmons to break the intrinsic symmetry of the material and trigger an instability toward self-rotation that causes the metal to become magnetic.

    Technique can produce properties ‘on demand’

    According to Mark Rudner, the new theory pries open an entire new mindset and most likely, a wide range of applications:

    “It is an example of how the interaction between light and material can be used to produce certain properties in a material ‘on demand’. It also paves the way for a multitude of uses, because the principle is quite general and can work on many types of materials. We have demonstrated that we can transform a material into a magnet. We might also be able to change it into a superconductor or something entirely different,” says Rudner. He adds:

    “You could call it 21st century alchemy. In the Middle Ages, people were fascinated by the prospect of transforming lead into gold. Today, we aim to get one material to behave like another by stimulating it with a laser.”

    Among the possibilities, Rudner suggests that the principle could be useful in situations where one needs a material to alternate between behaving magnetically and not. It could also prove useful in opto-electronics – where, for example, light and electronics are combined for fiber-internet and sensor development.

    The researchers’ next steps are to expand the catalog of properties that can be altered in analogous ways, and to help stimulate their experimental investigation and utilization.

    See the full article here .


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    Niels Bohr Institute Campus

    Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

    The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

    During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

    On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

    The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

    The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

     
  • richardmitnick 8:53 pm on September 16, 2019 Permalink | Reply
    Tags: , , , , , the most massive neutron star yet J0740+6620   

    From PBS NOVA: “Astronomers may have just detected the most massive neutron star yet” 

    From PBS NOVA

    September 16, 2019
    Katherine J. Wu

    1
    An artist’s impression of the pulse from a neutron star being delayed by a white dwarf passing between the neutron star and Earth. Image Credit: BSaxton, NRAO/AUI/NSF

    1

    The sun at the center of our solar system is a big-bodied behemoth, clocking in at more than 4 nonillion pounds (in the U.S., that’s 4 followed by 30 zeros).

    Now, multiply that mass by 2.14, and cram it down into a ball just 15 miles across. That’s an absurdly dense object, one almost too dense to exist. But the key word here is “almost”—because a team of astronomers has just found one such star.

    The newly discovered cosmic improbability, reported today in the journal Nature Astronomy, is a neutron star called J0740+6620 that lurks 4,600 light-years from Earth. It’s the most massive neutron star ever detected, and is likely to remain a top contender for that title for some time: Much denser, researchers theorize, and it would collapse into a black hole.

    Both neutron stars and black holes are stellar corpses—the leftover cores of stars that die in cataclysmic explosions called supernovae. The density of these remnants dictates their fate: The more mass that’s stuffed into a small space, the more likely a black hole will form.

    Neutron stars are still ultra-dense, though, and astronomers don’t have a clear-cut understanding of how matter behaves within them. Extremely massive neutron stars like this one, which exist tantalizingly close to the black hole tipping point, could yield some answers, study author Thankful Cromartie, an astronomer at the University of Virginia, told Ryan F. Mandelbaum at Gizmodo.

    Cromartie and her colleagues first detected J0740+6620, which is a type of rapidly rotating neutron star called a millisecond pulsar, with the Green Bank telescope in West Virginia. The name arises from the way the spinning star’s poles emit radio waves, generating a pulsing pattern that mimics the sweeping motion of a lighthouse beam.

    During their observations, the researchers noted that J0740+6620 is locked into a tight dance with a white dwarf—another kind of dense stellar remnant. The two bodies orbit each other, forming what’s called a binary. When the white dwarf passes in front of the pulsar from our point of view, it forces light from J0740+6620 to take a slightly longer path to Earth, because the white dwarf’s gravity slightly warps the space around it. The team used the delay in J0740+6620’s pulses to calculate the mass of both objects.

    Previous measurements from the Laser Interferometer Gravitational-Wave Observatory (LIGO) suggest that the upper limit for a neutron star’s mass is about 2.17 times that of the sun—a figure that’s just a smidge above J0740+6620’s estimated heft. But with future observations, that number could still change.

    MIT /Caltech Advanced aLigo

    Harshal Gupta, NSF program director for the Green Bank Observatory, called the new paper “a very solid effort in terms of astronomy and the physics of compact objects,” Mandelbaum reports.

    “Each ‘most massive’ neutron star we find brings us closer to identifying that tipping point [when they must collapse],” study author Scott Ransom, an astronomer at the National Radio Astronomy Observatory, said in a statement. “The orientation of this binary star system created a fantastic cosmic laboratory.”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 8:25 pm on September 16, 2019 Permalink | Reply
    Tags: , , , , ,   

    From UC Santa Barbara: “A Quantum Leap” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    September 16, 2019
    James Badham

    $25M grant makes UC Santa Barbara home to the nation’s first NSF-funded Quantum Foundry, a center for development of materials and devices for quantum information-based technologies.

    1
    Professors Stephen Wilson and Ania Bleszynski Jayich will co-direct the campus’s new Quantum Foundry

    We hear a lot these days about the coming quantum revolution. Efforts to understand, develop, and characterize quantum materials — defined broadly as those displaying characteristics that can be explained only by quantum mechanics and not by classical physics — are intensifying.

    Researchers around the world are racing to understand these materials and harness their unique qualities to develop revolutionary quantum technologies for quantum computing, communications, sensing, simulation and other quantum technologies not yet imaginable.

    This week, UC Santa Barbara stepped to the front of that worldwide research race by being named the site of the nation’s first Quantum Foundry.

    Funded by an initial six-year, $25-million grant from the National Science Foundation (NSF), the project, known officially as the UC Santa Barbara NSF Quantum Foundry, will involve 20 faculty members from the campus’s materials, physics, chemistry, mechanical engineering and computer science departments, plus myriad collaborating partners. The new center will be anchored within the California Nanosystems Institute (CNSI) in Elings Hall.

    3
    California Nanosystems Institute

    The grant provides substantial funding to build equipment and develop tools necessary to the effort. It also supports a multi-front research mission comprising collaborative interdisciplinary projects within a network of university, industry, and national-laboratory partners to create, process, and characterize materials for quantum information science. The Foundry will also develop outreach and educational programs aimed at familiarizing students at all levels with quantum science, creating a new paradigm for training students in the rapidly evolving field of quantum information science and engaging with industrial partners to accelerate development of the coming quantum workforce.

    “We are extremely proud that the National Science Foundation has chosen UC Santa Barbara as home to the nation’s first NSF-funded Quantum Foundry,” said Chancellor Henry T. Yang. “The award is a testament to the strength of our University’s interdisciplinary science, particularly in materials, physics and chemistry, which lie at the core of quantum endeavors. It also recognizes our proven track record of working closely with industry to bring technologies to practical application, our state-of-the-art facilities and our educational and outreach programs that are mutually complementary with our research.

    “Under the direction of physics professor Ania Bleszynski Jayich and materials professor Stephen Wilson the foundry will provide a collaborative environment for researchers to continue exploring quantum phenomena, designing quantum materials and building instruments and computers based on the basic principles of quantum mechanics,” Yang added.

    Said Joseph Incandela, the campus’s vice chancellor for research, “UC Santa Barbara is a natural choice for the NSF quantum materials Foundry. We have outstanding faculty, researchers, and facilities, and a great tradition of multidisciplinary collaboration. Together with our excellent students and close industry partnerships, they have created a dynamic environment where research gets translated into important technologies.”

    “Being selected to build and host the nation’s first Quantum Foundry is tremendously exciting and extremely important,” said Rod Alferness, dean of the College of Engineering. “It recognizes the vision and the decades of work that have made UC Santa Barbara a truly world-leading institution worthy of assuming a leadership role in a mission as important as advancing quantum science and the transformative technologies it promises to enable.”

    “Advances in quantum science require a highly integrated interdisciplinary approach, because there are many hard challenges that need to be solved on many fronts,” said Bleszynski Jayich. “One of the big ideas behind the Foundry is to take these early theoretical ideas that are just beginning to be experimentally viable and use quantum mechanics to produce technologies that can outperform classical technologies.”

    Doing so, however, will require new materials.

    “Quantum technologies are fundamentally materials-limited, and there needs to be some sort of leap or evolution of the types of materials we can harness,” noted Wilson. “The Foundry is where we will try to identify and create those materials.”

    Research Areas and Infrastructure

    Quantum Foundry research will be pursued in three main areas, or “thrusts”:

    • Natively Entangled Materials, which relates to identifying and characterizing materials that intrinsically host anyon excitations and long-range entangled states with topological, or structural, protection against decoherence. These include new intrinsic topological superconductors and quantum spin liquids, as well as materials that enable topological quantum computing.

    • Interfaced Topological States, in which researchers will seek to create and control protected quantum states in hybrid materials.

    • Coherent Quantum Interfaces, where the focus will be on engineering materials having localized quantum states that can be interfaced with various other quantum degrees of freedom (e.g. photons or phonons) for distributing quantum information while retaining robust coherence.

    Developing these new materials and assessing their potential for hosting the needed coherent quantum state requires specialized equipment, much of which does not exist yet. A significant portion of the NSF grant is designated to develop such infrastructure, both to purchase required tools and equipment and to fabricate new tools necessary both to grow and characterize the quantum states in the new materials, Wilson said.

    UC Santa Barbara’s deep well of shared materials growth and characterization infrastructure was also a factor in securing the grant. The Foundry will leverage existing facilities, such as the large suite of instrumentation shared via the Materials Research Lab and the California Nanosystems Institute, multiple molecular beam epitaxy (MBE) growth chambers (the university has the largest number of MBE apparatuses in academia), unique optical facilities such as the Terahertz Facility, state-of-the-art clean rooms, and others among the more than 300 shared instruments on campus.

    Data Science

    NSF is keenly interested in both generating and sharing data from materials experiments. “We are going to capture Foundry data and harness it to facilitate discovery,” said Wilson. “The idea is to curate and share data to accelerate discovery at this new frontier of quantum information science.”

    Industrial Partners

    Industry collaborations are an important part of the Foundry project. UC Santa Barbara’s well-established history of industrial collaboration — it leads all universities in the U.S. in terms of industrial research dollars per capita — and the application focus that allows it to to transition ideas into materials and materials into technologies, was important in receiving the Foundry grant.

    Another value of industrial collaboration, Wilson explained, is that often, faculty might be looking at something interesting without being able to visualize how it might be useful in a scaled-up commercial application. “If you have an array of directions you could go, it is essential to have partners to help you visualize those having near-term potential,” he said.

    “This is a unique case where industry is highly interested while we are still at the basic-science level,” said Bleszynski Jayich. “There’s a huge industry partnership component to this.”

    Among the 10 inaugural industrial partners are Microsoft, Google, IBM, Hewlett Packard Enterprises, HRL, Northrop Grumman, Bruker, SomaLogic, NVision, and Anstrom Science. Microsoft and Google have substantial campus presences already; Microsoft’s Quantum Station Q lab is here, and UC Santa Barbara professor and Google chief scientist John Martinis and a team of his Ph.D. student researchers are working with Google at its Santa Barbara office, adjacent to campus, to develop Google’s quantum computer.

    Undergraduate Education

    In addition, with approximately 700 students, UC Santa Barbara’s undergraduate physics program is the largest in the U.S. “Many of these students, as well as many undergraduate engineering and chemistry students, are hungry for an education in quantum science, because it’s a fascinating subject that defies our classical intuition, and on top of that, it offers career opportunities. It can’t get much better than that,” Bleszynski Jayich said.

    Graduate Education Program

    Another major goal of the Foundry project is to integrate quantum science into education and to develop the quantum workforce. The traditional approach to quantum education at the university level has been for students to take physics classes, which are focused on the foundational theory of quantum mechanics.

    “But there is an emerging interdisciplinary component of quantum information that people are not being exposed to in that approach,” Wilson explained. “Having input from many overlapping disciplines in both hard science and engineering is required, as are experimental touchstones for trying to understand these phenomena. Student involvement in industry internships and collaborative research with partner companies is important in addressing that.”

    “We want to introduce a more practical quantum education,” Bleszynski Jayich added. “Normally you learn quantum mechanics by learning about hydrogen atoms and harmonic oscillators, and it’s all theoretical. That training is still absolutely critical, but now we want to supplement it, leveraging our abilities gained in the past 20 to 30 years to control a quantum system on the single-atom, single-quantum-system level. Students will take lab classes where they can manipulate quantum systems and observe the highly counterintuitive phenomena that don’t make sense in our classical world. And, importantly, they will learn various cutting-edge techniques for maintaining quantum coherence.

    “That’s particularly important,” she continued, “because quantum technologies rely on the success of the beautiful, elegant theory of quantum mechanics, but in practice we need unprecedented control over our experimental systems in order to observe and utilize their delicate quantum behavior.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition


    UC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 7:55 pm on September 16, 2019 Permalink | Reply
    Tags: "Where the Rivers Meet the Sea", Estuaries are the borderlands between salt- and freshwater environments and they are incredibly diverse both biologically and physically., Oceanus Magazine,   

    From Oceanus Magazine via Woods Hole Oceanographic Institution: “Where the Rivers Meet the Sea” 

    From Woods Hole Oceanographic Institution

    1

    September 16, 2019
    W. Rockwell Geyer

    The transition from salt to fresh water is turbulent, vulnerable, and incredibly bountiful.

    2

    The sea lions stop bellowing and slip, one by one, off the jetty into the mocha-brown water of the Fraser River, near Vancouver, British Columbia. The surface of the water is smooth, except for a line of ripples moving slowly upriver. The sea lions seem to know that the calm surface belies turmoil beneath.

    The tide has just turned, and a tongue of salt water is first creeping, then galloping, back into the Fraser just a few hours after being expelled by a strong outflow during the previous ebb. Although the surface appears calm, the underwater intersection of fresh and salt water roils with turbulent eddies as strong as any in the ocean. The confusion of swirling water and suspended sediments disorients homeward-bound salmon, providing an easy feast for the sea lions.

    Not all rivers end as dramatically as the Fraser. But the mixing of freshwater streams and rivers with salty ocean tides in a partly enclosed body of water—natural scientists call it an estuary—fuels some of the most productive ecosystems on Earth, and also some of the most vulnerable.

    Long before the advent of civilization, early humans recognized the bounty of the estuary and made these regions a focal point for human habitation. Unfortunately, overdevelopment, poor land use, and centuries of industrial contamination have taken a toll on most estuaries. Boston Harbor, San Francisco Bay, and the Hudson River are poster children for environmental degradation.

    Yet there is hope. Estuaries are the borderlands between salt- and freshwater environments, and they are incredibly diverse both biologically and physically. The diversity and the high energy of the ecosystem make estuaries remarkably resilient. With a better understanding of these systems, we can reverse their decline and restore the ecological richness of these valuable, albeit muddy, environments.
    How does an estuary work?

    From a physicist’s point of view, the density difference between fresh and salt water makes estuaries interesting. When river water meets sea water, the lighter fresh water rises up and over the denser salt water. Sea water noses into the estuary beneath the outflowing river water, pushing its way upstream along the bottom.

    Often, as in the Fraser River, this occurs at an abrupt salt front. Across such a front, the salt content (salinity) and density may change from oceanic to fresh in just a few tens of meters horizontally and as little as a meter vertically.

    Accompanying these strong salinity and density gradients are large vertical changes in current direction and strength. You can’t see these swirling waters from the surface, but a fisherman may find that his net takes on a life of its own when he lowers it into seemingly placid water.

    Pliny the Elder, the noted Roman naturalist, senator, and commander of the Imperial Fleet in the 1st century A.D., observed this peculiar behavior of fishermens’ nets in the Strait of Bosphorus, near Istanbul. Pliny deduced that surface and bottom currents were flowing in opposite directions, and he provided the first written documentation of what we now call the “estuarine circulation.”

    Saltwater intrusion

    The opposing fresh and saltwater streams sometimes flow smoothly, one above the other. But when the velocity difference reaches a certain threshold, vigorous turbulence results, and the salt and fresh water are mixed. Tidal currents, which act independently of estuarine circulation, also add to the turbulence, mixing the salt and fresh waters to produce brackish water in the estuary.

    In the Fraser River, this circulation is confined to a very short and energetic frontal zone near the mouth, sometimes only several hundred meters long. In other estuaries, such as San Francisco Bay, the Chesapeake Bay, or the Hudson River, the salt front and accompanying estuarine circulation extend inland for many miles.

    The landward intrusion of salt is carefully monitored by engineers because of the potential consequences to water supplies if the salt intrusion extends too far. For instance, the city of Poughkeepsie, N.Y., 60 miles north of the mouth of the Hudson River, depends on the river for its drinking water. Roughly once per decade, drought conditions cause the salt intrusion to approach the Poughkeepsie freshwater intake. The last time this happened, in 1995, extra water had to be spilled from dams upstream to keep the salt front from becoming a public health hazard.

    The lifeblood of estuaries

    Estuarine circulation serves a valuable, ecological function. The continual bottom flow provides an effective ventilation system, drawing in new oceanic water and expelling brackish water. If it weren’t for this natural “flushing” process, the waters of the estuary would become stagnant, pollution would accumulate, and oxygen would be depleted.

    This circulation system leads to incredible ecological productivity. Nutrients and dissolved oxygen are continually resupplied from the ocean, and wastes are expelled in the surface waters. This pumping action leads to some of the highest growth rates of microscopic plants (researchers call it “primary production”) in any marine environment. This teeming population of plankton provides a base for diverse and valuable food webs, fueling the growth of some of our most prized fish, birds, and mammals—salmon, striped bass, great blue heron, bald eagles, seals, and otters, to name a few.

    The vigor of the circulation depends in part on the supply of river water to push the salt water back. The San Francisco Bay area has become a center of controversy in recent years because there are many interests competing for the fresh water flowing into the Bay—principally agriculture and urban water supplies extending to Southern California. Environmentalists are determined that San Francisco Bay should get “its share” of the fresh water coming from the Sacramento-San Joachim delta because the vast freshwater habitats in the region are particularly vulnerable to salt intrusion.

    Estuarine circulation is also affected by the tides; stronger tides generally enhance the exchange and improve the ecological function of the system. The Hudson estuary, for example, is tidal for 153 miles inland to Troy, N.Y. The Algonquin Indians called the river Mohicanituk, “the river that flows both ways.”

    Mucking up the system

    Estuaries have their problems. Some are self-inflicted; some are caused by the abuses of human habitation.

    An estuary, with all of its dynamic stirrings, has one attribute that promotes its own destruction: It traps sediment. When suspended mud and solids from a river enter the estuary, they encounter the salt front. Unlike fresh water, which rides up and over the saline layer, the sediment falls out of the surface layer into the denser, saltier layer of water moving into the estuary. As it drops, it gets trapped and accumulates on the bottom. Slowly, the estuary grows muddier and muddier, shallower and shallower.

    Occasionally a major flood will push the salt right out of the estuary, carrying the muddy sediment along with it. Sediment cores in the Hudson River indicate that sediment may accumulate for 10, 20, or even 50 years, laying down layers every year like tree rings. But then a hurricane or big snowmelt floods the river, wipes out the layers of sediment, and sends the mud out to sea.

    The “episodic” behavior of sediment deposition is good news and bad news. It is good because a big storm can keep an estuary from getting too shallow too fast. In fact, it appears that over the last 6,000 years, the natural dredging by large storms has maintained nearly constant water depth in the Hudson estuary.

    The bad news is that the sediment retains a “memory” of all of the contaminants that have passed through it over the years. Environmental regulations are far stricter now than they were 50 years ago, and we have stopped using many chemicals that play havoc with the environment. For instance, polychlorinated biphenyls (PCBs) were banned in the 1970s because they were shown to be toxic to fish and wildlife, and to the humans who consume them. Yet we still have a contamination problem in the Hudson and other rivers because PCBs are slow to decay and each new flood remobilizes these “legacy” contaminants and prolongs our exposure.

    Trickle-down effects

    Billions of dollars are now being spent to clean up American estuaries contaminated by industrial pollution. In Boston, for instance, the new sewage system created to save Boston Harbor cost taxpayers about $5 billion. The Superfund program of the U.S. Environmental Protection Agency collects and spends billions of dollars more to remediate estuaries.

    Often the remediation strategies are complex and controversial. In the case of Hudson River, there is a heated debate about whether PCB-contaminated sediments should be removed—dredged with high-tech methods that theoretically minimize environmental harm—or left undisturbed. That debate pivots on the episodic storm phenomenon: Are the contaminated sediments there to stay, or could they get stirred up when the next hurricane washes through the Hudson Valley?

    Aside from cleanup initiatives, parts of the Hudson need to be dredged for navigational purposes. Dredging is not that costly or difficult, but finding a place to put contaminated sediments is a problem. The Port of New York has been filling up abandoned Pennsylvania coal mines with its contaminated mud, but that is not a long-term solution.

    While the problems of American estuaries are complicated and expensive, they pale in comparison to Asian estuaries. The entire nation of Bangladesh lies within the estuary and lower floodplain of the Ganges-Brahmaputra River. Other Asian rivers such as the Mekong, Chiang Jiang (or Yangtze), and Huang Ho (or Yellow River) are crowded and strained by concentrated human settlements. Global sea-level rise is causing a loss of land, increased flooding, and increased salt intrusion in these estuaries.

    The demand for water upstream for irrigation and domestic use significantly reduces freshwater flow through these systems. The Indus River and Huang Ho estuaries have suffered from drastic reductions of freshwater flow over the past several decades, and the impact of these human alterations is just now being recognized. New policies about land use, water diversion, and even global carbon dioxide production (which affects global warming and sea level rise) will be needed to protect these vulnerable estuarine environments and their human inhabitants.

    Stirring up new ideas

    One of the challenges of estuarine research is that most of the significant problems are interdisciplinary, involving physics, biology, chemistry, geology, and often public policy and economics. Estuaries are also incredibly diverse, coming in all shapes and sizes. Yet scientists are continually challenged by public policymakers to generalize our results from studies of one estuary and apply them to the rest of the world’s estuaries.

    As scientists, one of our roles is to predict changes in the environment, given different natural and human-induced influences. To foresee the health of estuaries in the future, we have some fundamental questions to answer about the present and the past. How far will salt intrude if river flow is cut in half? Do changes in river flow increase or decrease the rate at which sediments shoal the estuary? What effect do such changes have on the fish that spawn in fresh water?

    What we learn will be critical for a human population that increasingly values coastal waters. We need sound public policy to reduce vulnerability to coastal flooding and to protect drinking water, food supplies, and some of the world’s most important habitats. We will develop better policies only if we can ground them in better science.

    Oceanus, the oceanography magazine produced by WHOI,now has an online version at http://oceanusmag.whoi.edu.
    Initial articles feature deep ocean exploration, such as the
    evolutionary puzzle of seafloor life, life beneath the sea floor,
    and undersea earthquakes. Articles on current research in the
    coastal ocean, including the debate over wind farms, are being
    added regularly, and future articles will focus on ocean life,
    from marine mammals to genetics. The online version includes
    an email update function, which emails links to new articles
    when they are posted, printer-friendly versions of each article,
    and an “e-mail this to a friend” function. For visually impaired
    viewers, there is a button to enlarge the screen display. Oceanus
    will cover the work of the Institution’s Ocean Institutes this
    year, then branch out to cover WHOI science more broadly. Print
    issues of the magazine will also be available later this year.

    See the full article here. .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Woods Hole Oceanographic Institute

    Vision & Mission

    The ocean is a defining feature of our planet and crucial to life on Earth, yet it remains one of the planet’s last unexplored frontiers. For this reason, WHOI scientists and engineers are committed to understanding all facets of the ocean as well as its complex connections with Earth’s atmosphere, land, ice, seafloor, and life—including humanity. This is essential not only to advance knowledge about our planet, but also to ensure society’s long-term welfare and to help guide human stewardship of the environment. WHOI researchers are also dedicated to training future generations of ocean science leaders, to providing unbiased information that informs public policy and decision-making, and to expanding public awareness about the importance of the global ocean and its resources.
    Mission Statement

    The Woods Hole Oceanographic Institution is dedicated to advancing knowledge of the ocean and its connection with the Earth system through a sustained commitment to excellence in science, engineering, and education, and to the application of this knowledge to problems facing society.

     
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