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  • richardmitnick 3:05 pm on November 21, 2019 Permalink | Reply
    Tags: "Two million-year-old ice cores provide first direct observations of an ancient climate", , , Princeton University   

    From Princeton University: “Two million-year-old ice cores provide first direct observations of an ancient climate” 

    Princeton University
    From Princeton University

    Nov. 21, 2019
    Morgan Kelly, Princeton Environmental Institute

    Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica that provide the first direct observations of Earth’s climate at a time when the furred early ancestors of modern humans still roamed.

    1
    Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica — the oldest yet recovered — that provide the first direct observations of prehistoric atmospheric conditions and temperatures. They used data from the ice cores to answer long-held questions about how our current colder, longer glacial cycle emerged.
    Photo by Sean Mackay, Boston University.

    Gas bubbles trapped in the cores — which are the oldest yet recovered — contain pristine samples of carbon dioxide, methane and other gases that serve as “snapshots” of prehistoric atmospheric conditions and temperatures, the researchers recently reported in the journal Nature. The cores were collected in the remote Allan Hills of Antarctica.

    First author Yuzhen Yan, who received his Ph.D. in geosciences from Princeton in 2019, explained that because ice flows and compresses over time, continual ice cores only extend back to 800,000 years ago. The cores he and his co-authors retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot.

    2
    Gas bubbles trapped in the cores contain pristine samples of carbon dioxide, methane and other gases that serve as “snapshots” of the ancient climate. Because ice flows and compresses over time, the cores the researchers retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot. Photo by Sean Mackay, Boston University.

    “You don’t get a sense of how things changed continually, but you get an idea of big changes over time,” said Yan, whose graduate research on ice cores supported by a 2016 Walbridge Fund Graduate Award for Environmental Research from the Princeton Environmental Institute (PEI) was a basis for the current work.

    The ice cores reported in Nature are the latest to come out of the research group of senior author John Higgins, a Princeton associate professor of geosciences, PEI associated faculty and Yan’s doctoral co-adviser. A previous team led by Higgins recovered a 1 million-year-old ice core from the Allan Hills, which was the oldest ice core ever recorded by scientists when it was reported in the journal Proceedings of the National Academy of Sciences in 2015. The cores were dated by measuring isotopes of the gas argon trapped in bubbles in the ice, a technique developed by co-author Michael Bender, Princeton professor of geosciences, emeritus, and PEI associated faculty.

    “The ability to measure atmospheric composition directly is one of the biggest advantages of ice cores,” Yan said. “That’s why people spend years and years in the most isolated places getting them.”

    In the latest publication, the researchers use data from the ice cores to answer long-held questions about how our current glacial cycle emerged. Up until roughly 1.2 million years ago, Earth’s ice ages consisted of thinner, smaller glaciers that came and went every 40,000 years on average.

    Then, after what is known as the Mid-Pleistocene Transition, there emerged our current world characterized by colder and longer glacial cycles of 100,000 years. The two periods are known as the 40k and 100k world, respectively.

    3
    The researchers collected the 2 million-year-old ice cores in the remote Allan Hills, where high winds help create the environmental conditions that draw ancient ice towards the surface. They found that although a long-term decline in atmospheric carbon dioxide did not directly lead to today’s colder glacial cycle, temperature and global ice volume nonetheless tracked carbon dioxide closely. Photo by Sean Mackay, Boston University.

    Some existing theories have stated that the 100k world — which includes the last ice age that ended 11,700 years ago — came about because of a long-term decline in atmospheric carbon dioxide, Yan said. But the researchers found that this was not the case — average carbon dioxide was relatively steady through the 40k and 100k worlds. While the lowest temperatures and carbon dioxide levels of the 40k world were greater than the low points of the 100k world, the highest levels of both ages were similar.

    “It could be the case that after the Mid-Pleistocene Transition, something occurred that lowered global glacial temperatures and atmospheric carbon dioxide values,” Yan said. “This is the first time we have direct access to these greenhouse gas measurements. The ice core also opens up an array of new measurement possibilities that can give us insights into the 40k world when glacial cycles were very different from what we have today.”

    Although a long-term decline in average atmospheric carbon dioxide may not have directly led to the 100k world, the researchers nonetheless observed a correlation between carbon dioxide and global temperature, Bender said.

    “To say that carbon dioxide is not a factor would be completely wrong,” Bender said. “During the 40,000- and 100,0000-year glacial-interglacial cycles, temperature and global ice volume tracks carbon dioxide rather closely. Carbon dioxide changes are required to get from the cooler glacial temperatures to the warmer interglacial temperatures.”

    5
    The newly reported cores are the latest to come out of the research group of senior author John Higgins, Princeton associate professor of geosciences. A previous team led by Higgins recovered a 1 million-year-old ice core from the Allan Hills, which was the oldest ever recorded when it was reported in 2015. Photo by Sean Mackay, Boston University.

    The amount of carbon dioxide now in the atmosphere tops 400 parts-per-million (ppm), which is nearly 100 ppm higher than the highest levels of the 40k world, Yan said.

    “We’re seeing carbon dioxide levels not seen in 2 million years,” Yan said. “While our data suggest that long-term carbon dioxide decline was not the decisive factor in the Mid-Pleistocene Transition, it does not mean that carbon dioxide does not have the capability to bring about global-scale changes.

    “We’re in a different situation now — carbon dioxide is the major player in our current world,” he said. “If we want to look into the geologic past for an analogy of what’s going on in our world today, we need to go beyond 2 million years to find it.”

    Yan, Higgins and Bender worked on the study in Nature with Preston Cosslett Kemeny, a Hertz Foundation Fellow at the California Institute of Technology who received his bachelor’s degree in geosciences and certificates in environmental studies and planets and life from Princeton in 2015. Co-authors also included Edward Brook at Oregon State University; Heather Clifford, Paul Mayewski and Andrei Kurbatov at the University of Maine; Sean Mackay, a past postdoctoral researcher at Princeton now at Boston University; and Jessica Ng and Jeffrey Severinghaus at the Scripps Institute of Oceanography.

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 12:42 pm on October 8, 2019 Permalink | Reply
    Tags: , Princeton University, Traverse supercomputer   

    From insideHPC: “Traverse Supercomputer to accelerate fusion research at Princeton” 

    From insideHPC

    October 8, 2019
    Rich Brueckner

    Princeton’s High-Performance Computing Research Center recently hosted a ribbon-cutting ceremony for Traverse, it’s newest supercomputer. Traverse is a 1.4 petaflop HPC cluster that ranks among the top 500 systems in the world.

    “Traverse is a mini version of ORNL’s Summit, thereby providing a stepping stone for the research community to one of the world’s fastest supercomputers,” said Curt Hillegas, associate CIO, Research Computin. “Getting experience using Traverse will allow our research groups to adapt their codes, so they can use the current leadership-class machines and be best prepared for the new exascale systems — capable of at least one exaFLOPS, or a billion billion calculations per second — expected to come online in the upcoming two years.”

    Exascale speeds are expected to help fusion researchers finally clear the remaining hurdles in the development of safe and sustainable fusion energy. “At that scale we will be able to simulate and optimize fusion reactors, speeding the deployment of fusion energy in the global battle against climate change,” explained Steven Cowley, PPPL director. “We are very grateful to the University for this marvelous facility.”

    1
    Shown at Princeton’s Sept. 30 ribbon-cutting for the Traverse supercomputer are, from left to right: Craig Ferguson, deputy director for operations and chief operating officer at the Princeton Plasma Physics Laboratory (PPPL); Steven Cowley, director of PPPL; David McComas, Princeton University’s vice president for PPPL; Chelle Reno, Princeton University’s assistant vice president for operations for PPPL; and Jay Dominick, Princeton University’s vice president for information technology and chief information officer. Photo: Denise Applewhite, Office of Communications.

    Plasma, the hot ionized gas that fuels fusion reactions, must be heated to very high temperatures for the particles to fuse and release their energy. The focus of much fusion research is preventing the swings in density and temperature that cause instabilities such as plasma disruptions, edge localized modes and energetic-particle driven modes. Machine learning (ML) techniques are helping researchers create better models for rapid control and containment of plasma.

    “Artificial intelligence (AI) and machine learning techniques could be a game changer,” said C.S. Chang, who heads the Center for High-fidelity Boundary Plasma Simulation at PPPL. “Due to the complicated nonlinear physics involved in these problems, using a supercomputer became a necessity for theoretical understanding. PPPL scientists will use Traverse to attack many of these problems in experiments, to collaborate with domestic and international researchers, and to help predict plasma performance in ITER, the international plasma research project using the world’s largest magnetic fusion device, or tokamak.”

    The AI advantages for scientific discovery are numerous, explained Chang. The hope is that equations will be solved much faster without going through traditional time-consuming numerical processes; experimental and theoretical data will be used to formulate simple equations that govern the physics processes; and the plasma will be controlled almost instantaneously, in millisecond time-frames too fast for human intervention.

    “A GPU-dominated computer such as Traverse is ideal for such AI/ML studies,” said Chang. “Solving these, and other important, physics and AI/ML problems on Traverse will greatly enhance the capabilities of graduate students, postdoctoral scientists and researchers, and their ability to advance these highly impactful areas in the world fusion and computational science research.”

    “Traverse is a major initiative in the University-DOE partnership,” McComas said. “Princeton and the U.S. Department of Energy have a long-standing commitment to the shared missions of fundamental research, world-leading education and fusion as a safe energy source. With the launch of Traverse, we look forward to even stronger connections between the University, PPPL and the DOE, and to accelerating leading-edge research needed to make fusion an abundant, safe and sustainable energy source for the U.S. and humanity.”

    See the full article here .

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    Founded on December 28, 2006, insideHPC is a blog that distills news and events in the world of HPC and presents them in bite-sized nuggets of helpfulness as a resource for supercomputing professionals. As one reader said, we’re sifting through all the news so you don’t have to!

    If you would like to contact me with suggestions, comments, corrections, errors or new company announcements, please send me an email at rich@insidehpc.com. Or you can send me mail at:

    insideHPC
    2825 NW Upshur
    Suite G
    Portland, OR 97239

    Phone: (503) 877-5048

     
  • richardmitnick 8:46 pm on September 19, 2019 Permalink | Reply
    Tags: , , , , Princeton University, Topology, Weyl loops   

    From Discovery at Princeton University: “Princeton physicists discover topological behavior of electrons in three-dimensional magnetic material” 

    Discovery at Princeton

    Princeton University
    From From Discovery at Princeton University

    1

    September 19, 2019

    Princeton physicists discover topological behavior of electrons in three-dimensional magnetic material.

    An international team of researchers led by scientists at Princeton University has found that a magnetic material at room temperature enables electrons to behave counterintuitively, acting collectively rather than as individuals. Their collective behavior mimics massless particles and anti-particles that coexist in an unexpected way and together form an exotic loop-like structure.

    The key to this behavior is topology—a branch of mathematics that is already known to play a powerful role in dictating the behavior of electrons in crystals. Topological materials can contain massless particles in the form of light, or photons. In a topological crystal, the electrons often behave like slowed-down light yet, unlike light, carry electrical charge.

    Topology has seldom been observed in magnetic materials, and the finding of a magnetic topological material at room temperature is a step forward that could unlock new approaches to harnessing topological materials for future technological applications.

    “Before this work, evidence for the topological properties of magnets in three dimensions was inconclusive. These new results give us direct and decisive evidence for this phenomenon at the microscopic level,” said M. Zahid Hasan, the Eugene Higgins Professor of Physics at Princeton, who led the research. “This work opens up a new continent for exploration in topological magnets.”

    Hasan and his team spent more than a decade studying candidate materials in the search for a topological magnetic quantum state.

    “The physics of bulk magnets has been understood for many decades. A natural question for us is: Can magnetic and topological properties together produce something new in three dimensions?” Hasan said.

    Thousands of magnetic materials exist, but most did not have the correct properties, the researchers found. The magnets were too difficult to synthesize, the magnetism was not sufficiently well understood, the magnetic structure was too complicated to model theoretically, or no decisive experimental signatures of the topology could be observed.

    Then came a lucky turning point.

    “After studying many magnetic materials, we performed a measurement on a class of room-temperature magnets and unexpectedly saw signatures of massless electrons,” said Ilya Belopolski, a postdoctoral researcher in Hasan’s laboratory and co-first author of the study. “That set us on the path to the discovery of the first three-dimensional topological magnetic phase.”

    2
    Researchers in the laboratory of M. Zahid Hasan (second from left). Photo by Denise Applewhite, Princeton University

    The exotic magnetic crystal consists of cobalt, manganese and gallium, arranged in an orderly, repeating three-dimensional pattern. To explore the material’s topological state, the researchers used a technique called angle-resolved photoemission spectroscopy. In this experiment, high-intensity light shines on the sample, forcing electrons to emit from the surface. These emitted electrons can then be measured, providing information about the way the electrons behaved when they were inside the crystal.

    “It’s an extremely powerful experimental technique, which in this case allowed us to directly observe that the electrons in this magnet behave as if they are massless. These massless electrons are known as Weyl fermions,” said Daniel Sanchez, a Princeton visiting researcher and Ph.D. student at the University of Copenhagen, and another co-first author of the study.

    A key insight came when the researchers studied the Weyl fermions more closely and realized that the magnet hosted an infinite series of distinct massless electrons that takes the form of a loop, with some electrons mimicking properties of particles and some of anti-particles. This collective quantum behavior of the electrons has been termed a magnetic topological Weyl fermion loop.

    “It truly is an exotic and novel system,” said Guoqing Chang, a postdoctoral researcher in Hasan’s group and co-first author of the study. “The collective electron behavior in these particles is unlike anything familiar to us in our everyday experience—or even in the experience of particle physicists studying subatomic particles. Here we are dealing with emergent particles obeying different laws of nature.”

    It turns out that a key driver of these properties is a mathematical quantity that describes the infinite series of massless electrons. The researchers were able to pin down the role of topology by observing subtle changes in the difference of the behavior of electrons living on the surface of the sample and deeper in its interior. The technique to demonstrate topological quantities through the contrasts of surface and bulk properties was pioneered by Hasan’s group and used to detect Weyl fermions, a finding published in 2015. The team recently used an analogous approach to discover a topological chiral crystal, work published in the journal Nature earlier this year that was also led by Hasan’s group at Princeton and included Daniel Sanchez, Guoqing Chang and Ilya Belopolski as leading authors.

    Theoretical predictions

    The relationship between the topology and magnetic quantum loop particles was explored in the Hasan group’s theoretical predictions published in October 2017 in Physical Review Letters. However, the group’s theoretical interest in topological magnets dates back much earlier to theoretical predictions published in Nature Materials in 2010. These theoretical works by Hasan’s group were funded by U.S. Department of Energy’s office of Basic Energy Sciences.

    “This work represents the culmination of about a decade of seeking to realize a topological magnetic quantum phase in three dimensions,” Hasan said.

    In 2016, Duncan Haldane, Princeton’s Sherman Fairchild University Professor of Physics, won the Nobel Prize in Physics for his theories predicting the properties of one- and two-dimensional topological materials.

    An important aspect of the result is that the material retains its magnetism up to 400 degrees Celsius—well above room temperature—satisfying a key requirement for real-world technological applications.

    “Before our work, topological magnetic properties were typically observed when the thin films of materials were extremely cold—a fraction of a degree above absolute zero—requiring specialized equipment simply to achieve the necessary temperatures. Even a small amount of heat would thermally destabilize the topological magnetic state,” Hasan said. “The quantum magnet studied here exhibits topological properties at room temperature.”

    A topological magnet in three dimensions reveals its most exotic signatures only on its surface—electron wavefunctions take the shape of drumheads. This is unprecedented in previously known magnets and constitute the telltale signature of a topological magnet. The researchers observed such drumhead-shaped electronic states in their data, providing the crucial decisive evidence that it is a novel state of matter.

    Patrick Lee, the William & Emma Rogers Professor of Physics at the Massachusetts Institute of Technology, who was not involved in the study, commented on the importance of the finding. “The Princeton group has long been at the forefront of discovering new materials with topological properties,” Lee said. “By extending this work to a room temperature ferromagnetic and demonstrating the existence of a new kind of ‘drumhead’ surface states, this work opens up a new domain for further discoveries.”

    To understand their findings, the researchers studied the arrangement of atoms on the surface of the material using several techniques, such as checking for the right kind of symmetry using the scanning tunneling microscope in Hasan’s Laboratory for Topological Quantum Matter and Advanced Spectroscopy located in the basement of Princeton’s Jadwin Hall.

    An important contributor to the finding was the cutting-edge spectroscopy equipment used to carry out the experiment. The researchers used a dedicated photoemission spectroscopy beamline recently built at the Stanford Synchrotron Radiation Lightsource, part of the SLAC National Accelerator Laboratory in Menlo Park, California.

    SLAC SSRL Campus


    SLAC/SSRL

    “The light used in the SLAC photoemission experiment is extremely bright and focused down to a tiny spot only several tens of micrometers in diameter,” said Belopolski. “This was important for the study.”

    The work was carried out in close collaboration with the group of Professor Hsin Lin at the Institute of Physics, Academia Sinica in Taiwan, and Professor Claudia Felser at the Max Planck Institute for the Chemical Physics of Solids in Dresden, Germany, including postdoctoral researcher Kaustuv Manna as co-first author. Co-authors included researchers from Shenzhen University, University of Missouri, National Cheng Kung University, National Sun Yat-Sen University and Northwestern University.

    Driven by the tantalizing possibility of applications, the researchers went one step further and applied electromagnetic fields to the topological magnet to see how it would respond. They observed an exotic electromagnetic response up to room temperature, which could be directly traced back to the quantum loop electrons.

    “We have many topological materials, but among them it has been difficult to show a clear electromagnetic response arising from the topology,” Hasan added. “Here we have been able to do that. It sets up a whole new research field for topological magnets.”

    The study, “Discovery of topological Weyl fermion lines and drumhead surface states in a room temperature magnet,” by Ilya Belopolski, Kaustuv Manna, Daniel S. Sanchez, Guoqing Chang, Benedikt Ernst, Jiaxin Yin, Songtian S. Zhang, Tyler Cochran, Nana Shumiya, Hao Zheng, Bahadur Singh, Guang Bian, Daniel Multer, Maksim Litskevich, Xiaoting Zhou, Shin-Ming Huang, Baokai Wang, Tay-Rong Chang, Su-Yang Xu, Arun Bansil, Claudia Felser, Hsin Lin and Zahid Hasan appears in the Sept. 19 issue of Science.

    See the full article here .

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    Princeton University Campus

    Discovery at Princeton University

    Whatever the controversy of the day, the way forward in science relies on following the evidence, wherever it may lead. Princeton researchers are at the forefront of this path, both through theoretical advances in artificial intelligence and machine learning, and through innovations in data science that are helping to address societal challenges, such as eviction and its impacts, energy-efficient transportation, marine “dead zones,” attitudes on immigration, and many more.

    The search for understanding is at the heart of University research, whether the quest leads to beautiful theorems, practical inventions or a new interpretation of art (page 26). Princeton is a place where all of these aspects of research coexist, cross-fertilize and intermingle. But why take my word for it? Let the pages of Discovery be the data that convince you.

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 12:04 pm on July 26, 2019 Permalink | Reply
    Tags: "Small but mighty: A mini plasma-powered satellite under construction may launch a new era in space exploration", A fleet of CubeSats, , Princeton University   

    From Princeton University and PPPL: “Small but mighty: A mini plasma-powered satellite under construction may launch a new era in space exploration” 

    Princeton University
    From Princeton University

    PPPL

    July 26, 2019
    John Greenwald, Princeton Plasma Physics Laboratory

    A tiny satellite under construction at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) could open new horizons in space exploration. Princeton University students are building the device, a cubic satellite or “CubeSat,” as a testbed for a miniaturized rocket thruster with unique capabilities being developed at PPPL.

    1
    The CubeSat’s thruster, whose development is led by PPPL physicist Yevgeny Raitses, holds the promise of increased flexibility for the tiny satellites, more than a thousand of which have been launched by universities, research centers and commercial interests around the world. The proposed propulsion device — powered by plasma — could raise and lower the orbits of CubeSats circling the Earth, a capability not broadly available to small spacecraft today, and would hold the potential for exploration of deep space.

    “Essentially, we will be able to use these miniature thrusters for many missions,” Raitses said.

    A fleet of CubeSats

    One example: A fleet made up of hundreds of such micropowered CubeSats could capture in fine detail the reconnection process in the magnetosphere, the magnetic field that surrounds the Earth, said physicist Masaaki Yamada. Yamada is the principal investigator of the PPPL Magnetic Reconnection Experiment, which studies magnetic reconnection — the separation and explosive snapping together of magnetic field lines in plasma that triggers auroras, solar flares and geomagnetic storms that can disrupt cell phone service and power grids on Earth.

    Key advantage

    The miniaturized engine scales down a cylindrical thruster with a high volume-to-surface geometry developed at the PPPL Hall Thruster Experiment, which Raitses leads and launched with PPPL physicist Nat Fisch in 1999. The experiment investigates the use of plasma — the state of matter composed of free-floating electrons and atomic nuclei, or ions — for space propulsion.

    A key advantage of the miniaturized cylindrical Hall thruster will be its ability to produce a higher density of rocket thrust than existing plasma thrusters used for most CubeSats now orbiting Earth. The miniaturized thruster can achieve both increased density and a high specific impulse — the technical term for how efficiently a rocket burns fuel — that will be many times greater than that produced by chemical rockets and cold-gas thrusters typically used on small satellites.

    High specific-impulse thrusters use much less fuel and can lengthen satellite missions, making them more cost-effective. Equally important is the fact that a high specific impulse can produce a large enough increase in a satellite’s momentum to enable the spacecraft to change orbits — a feature not available on currently orbiting CubeSats. Finally, high thrust density will enable satellites to accomplish complex fuel-optimized orbits in a reasonable time.

    These capabilities provide many benefits. For example, a CubeSat might descend to lower orbit to track hurricanes or monitor shoreline changes and return to a higher orbit where the drag force on a satellite is weaker, requiring less fuel for propulsion.

    The foot-long CubeSat, which Princeton has dubbed a “TigerSat,” consists of three 4-inch aluminum cubes stacked vertically together. Sensors, batteries, radio equipment and other instruments will fill the CubeSat, with a miniaturized thruster roughly equal in diameter to two U.S. quarters housed at either end. A thruster will fire to change orbits when the satellite passes the Earth’s equator.

    Mechanical and aerospace engineering students

    Building the CubeSat are some 10 Princeton graduate and undergraduate students in the Department of Mechanical and Aerospace Engineering, with Daniel Marlow, the Evans Crawford 1911 Professor of Physics, serving as faculty advisor. Undergraduates include Andrew Redd (Class of 2020), who leads design and construction of the CubeSat, and Seth Freeman (Class of 2022), who is working full-time on the project over the summer. Working on thruster development is Jacob Simmonds, a third-year graduate engineering student, whose thesis advisors are Raitses and Yamada. “This project began as a prototype of Yamada’s CubeSat and has evolved into its own project as a testbed for the plasma thruster,” Simmonds said.

    Also under construction at PPPL is a test facility designed to simulate key aspects of the CubeSat’s operation. Undergraduates working on their own time are building the satellite and this facility. “To the extent that students and their advisors have identified well-defined questions associated with the TigerSat project, they can get independent work credit,” Marlow said. “Also, some problem sets in the introductory physics course for undergraduates that I teach have questions related to the TigerSat flight plan.”

    Simmonds, while working on the thruster, is drafting a proposal for NASA’s Cubic Satellite Launch Initiative that is due in November. Projects selected by the Initiative, which promotes public-private technology partnerships and low-cost technology development, have launch costs covered on commercial and NASA vehicles. Plans call for a TigerSat launch in the fall of 2021.

    Value of collaboration

    For Raitses, this project demonstrates the value of Princeton engineering students collaborating with PPPL and of University faculty cooperating with the Laboratory. “This is something that is mutually beneficial,” he said, “and something that we want to encourage.”

    Support for the thruster work comes from Laboratory Directed Research and Development funds made available through the DOE Office of Science. Basic science aspects of the novel thruster based on low-temperature magnetized plasma is supported by the Air Force Office of Scientific Research. Princeton University supports construction of the CubeSat and the test facility.

    PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit http://www.energy.gov/science.

    See the full article here .

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    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.


    PPPL campus


    Princeton University campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 4:37 pm on July 24, 2019 Permalink | Reply
    Tags: , Portable scanners, Princeton University   

    From Princeton University: “Innovative tiny laser has potential uses in drug quality control, medical diagnosis, airplane safety” 

    Princeton University
    From Princeton University

    July 24, 2019
    Molly Sharlach

    In a major step toward developing portable scanners that can rapidly measure molecules on the pharmaceutical production line or classify tissue in patients’ skin, a Princeton-led team of researchers have created an imaging system that uses lasers small and efficient enough to fit on a microchip.

    The team demonstrated the system’s resolution by using it to image a U.S. quarter. Fine details like the eagle’s wing feathers, as small as one-fifth of a millimeter wide, were clearly visible.

    The system emits and detects electromagnetic radiation at terahertz frequencies — higher than radio waves but lower than the long-wave infrared light used for thermal imaging. Imaging using terahertz radiation has long been a goal for engineers, but the difficulty of creating practical systems that work in this frequency range has stymied most applications and resulted in what engineers call the “terahertz gap.”

    1
    Laser-generated images. A new imaging technology rapidly measures the chemical compositions of solids. A conventional image of a sample pill is shown at left; at right, looking at the same surface with terahertz frequencies reveals various ingredients as different colors. Such images would aid quality control and development in pharmaceutical manufacturing, as well as medical diagnosis. Images courtesy of the researchers

    “Here, we have a revolutionary technology that doesn’t have any moving parts and uses direct emission of terahertz radiation from semiconductor chips,” said Gerard Wysocki, an associate professor of electrical engineering at Princeton University and one of the leaders of the research team.

    Terahertz radiation can penetrate substances such as fabrics and plastics, is non-ionizing and therefore safe for medical use, and can be used to view materials difficult to image at other frequencies. It could potentially be used as a diagnostic tool for skin cancer, for example, even as its ability to image metal could be applied to test airplane wings for damage after being struck by an object in flight.

    The new system, described in a paper published in the June issue of the journal Optica, can quickly probe the identity and arrangement of molecules or expose structural damage to materials.

    The device uses stable beams of radiation at precise frequencies. The setup is called a frequency comb because it contains multiple “teeth” that each emit a different, well-defined frequency of radiation. The radiation interacts with molecules in the sample material. A dual-comb structure allows the instrument to efficiently measure the reflected radiation. Unique patterns, or spectral signatures, in the reflected radiation allow researchers to identify the molecular makeup of the sample.

    While current terahertz imaging technologies are expensive to produce and cumbersome to operate, the new system is based on a semiconductor design that costs less and can generate many images per second. This speed could make it useful for real-time quality control of pharmaceutical tablets on a production line and other fast-paced uses.

    “Imagine that every 100 microseconds a tablet is passing by, and you can check if it has a consistent structure and there’s enough of every ingredient you expect,” said Wysocki.

    2
    Gerard Wysocki (left), an associate professor of electrical engineering, and Jonas Westberg, an associate research scholar, helped create a new terahertz imaging system that represents a major step toward developing portable scanners that can rapidly measure molecules in pharmaceuticals or classify tissue in patients’ skin. Photo by David Kelly Crow

    As a proof of concept, the researchers created a tablet with three zones containing common inert ingredients in pharmaceuticals — forms of glucose, lactose and histidine. The terahertz imaging system identified each ingredient and revealed the boundaries between them, as well as a few spots where one chemical had spilled over into a different zone. This type of “hot spot” represents a frequent problem in pharmaceutical production that occurs when the active ingredient is not properly mixed into a tablet.

    While the technology makes the industrial and medical use of terahertz imaging more feasible than before, it still requires cooling to a low temperature, a major hurdle for practical applications. Many researchers are now working on lasers that will potentially operate at room temperature. The Princeton team said its dual-comb hyperspectral imaging technique will work well with these new room-temperature laser sources, which could then open many more uses.

    In addition to Wysocki, the paper’s Princeton authors are former visiting graduate student Lukasz Sterczewski (currently a postdoctoral scholar at NASA’s Jet Propulsion Laboratory) and associate research scholar Jonas Westberg. Other co-authors are Yang Yang, David Burghoff and Qing Hu of the Massachusetts Institute of Technology; and John Reno of Sandia National Laboratories.

    Terahertz hyperspectral imaging with dual chip-scale combs by Lukasz A. Sterczewski, Jonas Westberg, Yang Yang, David Burghoff, John Reno, Qing Hu and Gerard Wysocki was published in the June issue of the journal Optica (Vol. 6, Issue 6, pp. 766-771, DOI: 10.1364/OPTICA.6.000766). Support for the research was provided in part by the Defense Advanced Research Projects Agency and the U.S. Department of Energy.

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 2:35 pm on July 10, 2019 Permalink | Reply
    Tags: , , , , , , , Princeton University   

    From Princeton University: “Princeton scientists spot two supermassive black holes on collision course with each other” 

    Princeton University
    From Princeton University

    1
    Titanic Twosome: A Princeton-led team of astrophysicists has spotted a pair of supermassive black holes, roughly 2.5 billion light-years away, that are on a collision course (inset). The duo can be used to estimate how many detectable supermassive black hole mergers are in the present-day universe and to predict when the historic first detection of the background “hum” of gravitational waves will be made.
    Image courtesy of Andy Goulding et al./Astrophysical Journal Letters 2019

    July 10, 2019

    Each black hole’s mass is more than 800 million times that of our sun. As the two gradually draw closer together in a death spiral, they will begin sending gravitational waves rippling through space-time.


    Two Black Holes Merge into One.
    LIGO Lab Caltech : MIT
    Published on Feb 11, 2016
    A computer simulation shows the collision of two black holes, a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO. LIGO detected gravitational waves, or ripples in space and time generated as the black holes spiraled in toward each other, collided, and merged. This simulation shows how the merger would appear to our eyes if we could somehow travel in a spaceship for a closer look. It was created by solving equations from Albert Einstein’s general theory of relativity using the LIGO data.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    The two merging black holes are each roughly 30 times the mass of the sun, with one slightly larger than the other. Time has been slowed down by a factor of about 100. The event took place 1.3 billion years ago.

    The stars appear warped due to the incredibly strong gravity of the black holes. The black holes warp space and time, and this causes light from the stars to curve around the black holes in a process called gravitational lensing. The ring around the black holes, known as an Einstein ring, arises from the light of all the stars in a small region behind the holes, where gravitational lensing has smeared their images into a ring.

    The gravitational waves themselves would not be seen by a human near the black holes and so do not show in this video, with one important exception. The gravitational waves that are traveling outward toward the small region behind the black holes disturb that region’s stellar images in the Einstein ring, causing them to slosh around, even long after the collision. The gravitational waves traveling in other directions cause weaker, and shorter-lived sloshing, everywhere outside the ring.

    Those cosmic ripples will join the as-yet-undetected background noise of gravitational waves from other supermassive black holes. Even before the destined collision, the gravitational waves emanating from the supermassive black hole pair will dwarf those previously detected from the mergers of much smaller black holes and neutron stars.

    “Collisions between enormous galaxies create some of the most extreme environments we know of, and should theoretically culminate in the meeting of two supermassive black holes, so it was incredibly exciting to find such an immensely energetic pair of black holes so close together in our Hubble Space Telescope images,” said Andy Goulding, an associate research scholar in astrophysical sciences at Princeton who is the lead author on a paper appearing July 10 in Astrophysical Journal Letters.

    “Supermassive black hole binaries produce the loudest gravitational waves in the universe,” said co-discoverer and co-author Chiara Mingarelli, an associate research scientist at the Flatiron Institute’s Center for Computational Astrophysics in New York City. Gravitational waves from supermassive black hole pairs “are a million times louder than those detected by LIGO.

    .”

    “When these supermassive black holes merge, they will create a black hole hundreds of times larger than the one at the center of our own galaxy,” said Princeton graduate student Kris Pardo, a co-author on the paper.

    The two supermassive black holes are especially interesting because they are around 2.5 billion light-years away from Earth. Since looking at distant objects in astronomy is like looking back in time, the pair belong to a universe 2.5 billion years younger than our own. Coincidentally, that’s roughly the same amount of time the astronomers estimate the black holes will take to begin producing powerful gravitational waves.

    In the present-day universe, the black holes are already emitting these gravitational waves, but even at light speed the waves won’t reach us for billions of years. The duo is still useful, though. Their discovery can help scientists estimate how many nearby supermassive black holes are emitting gravitational waves that we could detect right now.

    Detecting the gravitational wave background would help answer some of the biggest unknowns in astronomy, such as how often galaxies merge and whether supermassive black hole pairs merge at all, or if they become stuck in a near-endless waltz around each other.

    “It’s a major embarrassment for astronomy that we don’t know if supermassive black holes merge,” said Jenny Greene, a professor of astrophysical sciences at Princeton and a co-author on the paper. “For everyone in black hole physics, observationally this is a long-standing puzzle that we need to solve.”

    Supermassive black holes can contain millions or even billions of suns’ worth of mass. Nearly all galaxies, including our own Milky Way, contain at least one of these behemoths at their core.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory


    SGR A and SGR A* from Penn State and NASA/Chandra

    When galaxies merge, their supermassive black holes meet up and begin orbiting one another. Over time, this orbit tightens as gas and stars pass between the black holes and steal energy.

    Once the supermassive black holes get too close, though, this energy theft all but stops. Some theories suggest that they stall at around 1 parsec apart (roughly 3.2 light-years). This slowdown lasts nearly indefinitely and is known as the “final parsec problem.” In this scenario, only very rare groups of three or more supermassive black holes result in mergers.

    Astronomers can’t just look for stalled pairs, because long before the black holes are a parsec apart, they’re too close to distinguish as two separate objects. Moreover, they don’t produce strong gravitational waves until they overcome the final parsec hurdle and get closer together. (Observed as they were 2.5 billion years ago, the newfound supermassive black holes appear about 430 parsecs apart.)

    If the final parsec problem turns out not to be a problem, then astronomers expect that the universe is filled with the clamor of gravitational waves from supermassive black hole pairs in the process of merging. “This noise is called the gravitational wave background, and it’s a bit like a chaotic chorus of crickets chirping in the night,” Goulding said. “You can’t discern one cricket from another, but the volume of the noise helps you estimate how many crickets are out there.”

    If two supermassive black holes do collide and combine, it will send a thundering “chirp” that will dwarf the background chorus – but it’s no small task to “hear” it.

    The telltale gravitational waves generated by merging supermassive black holes are outside the frequencies currently observable by experiments such as LIGO and Virgo, which have detected the mergers of much smaller black holes and neutron stars. Scientists hunting for the larger gravitational waves from supermassive black hole collisions rely on arrays of special stars called pulsars that act like metronomes, sending out radio waves in a steady rhythm. If a passing gravitational wave stretches or compresses the space between Earth and the pulsar, the rhythm will be thrown off slightly.

    Detecting the gravitational wave background using one of these pulsar timing arrays takes patience and plenty of monitored stars. A single pulsar’s rhythm might be disrupted by only a few hundred nanoseconds over a decade. The louder the background noise, the larger the timing disruptions and the quicker the detection will be made.

    Goulding, Greene and the other observational astronomers on the team detected the two titans with the Hubble Space Telescope. Although supermassive black holes aren’t directly visible through an optical telescope like Hubble, they are surrounded by bright clumps of luminous stars and warm gas drawn in by the powerful gravitational tug.

    Stars around SGR A* including S0-2 Andrea Ghez Keck/UCLA Galactic Center Group.

    For its time in history, the galaxy harboring the newfound supermassive black hole pair “is basically the most luminous galaxy in the universe,” Goulding said. What’s more, the galaxy’s core is shooting out two unusually colossal plumes of gas. When they pointed Hubble at it to uncover the origins of its spectacular gas clouds, the researchers discovered that the system contained not one but two massive black holes.

    The observational astronomers then teamed up with gravitational wave physicists Mingarelli and Pardo to interpret the finding in the context of the gravitational wave background. The discovery provides an anchor point for estimating how many merging supermassive black holes are within detection distance of Earth. Previous estimates relied on computer models of how often galaxies merge, rather than actual observations of supermassive black hole pairs.

    Based on the data, Pardo and Mingarelli predicted that in an optimistic scenario, there are about 112 nearby supermassive black holes emitting gravitational waves. The first detection of the gravitational wave background from supermassive black hole mergers should therefore come within the next five years or so. If such a detection isn’t made, that would be evidence that the final parsec problem may be insurmountable. The team is currently looking at other galaxies similar to the one harboring the newfound supermassive black hole binary. Finding additional pairs will help them further hone their predictions.

    “This is the first example of a close pair of such massive black holes that we’ve found, but there may well be additional binary black holes remaining to be discovered,” said co-author Professor Michael Strauss, the associate chair of Princeton’s Department of Astrophysical Sciences. “The more we can learn about the population of merging black holes, the better we will understand the process of galaxy formation and the nature of the gravitational wave background.”

    See the full article here .

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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 11:50 am on May 8, 2019 Permalink | Reply
    Tags: "Five projects will explore sustainability using the Princeton campus as a laboratory", Adding renewables to the electrical grid, Building better compost, Building without waste, Farming on campus lands, Field-testing solar-powered smart windows, Princeton University   

    From Princeton University: “Five projects will explore sustainability using the Princeton campus as a laboratory” 

    Princeton University
    From Princeton University

    May 8, 2019
    Catherine Zandonella, Office of the Dean for Research

    1
    In 2012, the University completed a restoration of meandering and stepped form for a portion of the stream along Washington Road to mitigate erosion and flood risks and improve the riparian habitat. Photo by Christopher Lillja, Facilities Organization.

    Research projects that explore energy-saving technologies, sustainable farming and resource reuse have been selected to receive Dean for Research Innovation Funds for the Campus as a Lab.

    The five projects will be conducted with the University’s grounds as the laboratory or testbed for the exploration of technologies or practices that enhance sustainability and environmental responsibility. The campus serves as a real-world setting where ideas and theories can be tried on a relatively small scale, with the goal of scaling up successful projects beyond campus.

    Princeton aims to engage the entire University community in creating a more sustainable campus and world through its new Sustainability Action Plan, announced on Earth Day, April 22. The campus as a lab projects are one aspect of this broad endeavor.

    A faculty-led committee chose the winning proposals based on quality, originality and potential impact on the campus or in the field of study. All projects involve either graduate students or postdoctoral researchers, or undergraduate students.

    Funding for the Dean for Research Innovation Funds for the Campus as a Lab comes from the Princeton Environmental Institute, Office of the Dean for Research, Andlinger Center for Energy and the Environment, High Meadows Foundation Sustainability Fund, and Facilities. The funding program is administered by the Office of the Dean for Research in collaboration with the Office of Sustainability.

    Adding renewables to the electrical grid

    2
    Minjie Chen and Darren Hammell. Photos by David Kelly Crow and Princeton Power Systems.

    To meet the challenge of including renewable energy sources such as wind and solar to the electrical grid — the network of power stations and lines that deliver electricity to homes and businesses — a team of researchers will build a prototype grid to allow experimentation on ways to coordinate electricity from renewable and non-renewable sources. Solar and wind energy production fluctuates widely depending on weather and time of day. An electric grid with a large percentage of renewable integration may become highly unstable if not coordinated correctly.

    The research team, led by Minjie Chen, assistant professor of electrical engineering and the Andlinger Center for Energy and the Environment, and Darren Hammell, the Gerhard R. Andlinger Visiting Fellow in Energy and the Environment, will test ways to incorporate solar, wind, battery and other sources of power by building a testing environment called the Andlinger Distributed Energy and Power Testbed (ADEPT). The testbed will be highly programmable to allow the team to explore various configurations of power supplies as well as spikes in power usage, such as the greater demand posed from charging electric vehicles. The project will also explore innovations in how to meet spikes in user demand, such as programming the grid to autonomously cluster into “micro-grids” to defend against cyberattacks or natural hazards, and using smart technologies to enhance grid stability.

    Building without waste

    3
    Erin Besler and Stefana Parascho. Photos by Andy Scott and Andreas Thoma.

    Reducing and reusing leftover construction materials — typically scraps of metal, wood and concrete —is the focus of a new initiative to improve the ecological footprint of architecture. The project, led by Erin Besler and Stefana Parascho, two assistant professors in the School of Architecture, has two parts: new design tools to cut down the ordering of excess materials and innovative robotic assembly methods to reuse existing materials.

    To reduce construction leftovers, the team will build an intuitive-to-use design tool that improves architectural planning. For existing leftovers, which often come in irregular shapes that can be a challenge to reuse, a team made up of faculty, graduate students and Facilities staff members will use computational approaches and robotics to design structures incorporating the materials. The project offers a way for architects, contractors and builders to develop more sustainable approaches to planning and constructing buildings. For the broader public, the project offers the opportunity to experience cast-off materials in architectural designs and structures.

    Selected projects involving undergraduate research:

    Field-testing solar-powered smart windows

    4
    Lynn Loo. Photo by David Kelly Crow.

    A new smart-window technology that uses solar power to darken or lighten window glass — which saves energy by reducing the need for heating and cooling indoor spaces — will be tested this summer on buildings around campus. The technology involves coating windows with a film of flexible, transparent solar cells that convert sunlight into electrical energy to drive the change in transparency. Developed in the laboratory of Lynn Loo, director of the Andlinger Center for Energy and the Environment and the Theodora D. ’78 and William H. Walton III ’74 Professor in Engineering, these organic photovoltaic cells could power smart windows without the need for an external electrical power supply, allowing this technology to address retrofits and upgrades of existing windows.

    To determine how these solar-powered smart windows perform in real-world situations, undergraduate Matthew Marquardt, Class of 2020, will install and evaluate them in campus buildings. In collaboration with engineers at Andluca Technologies, a startup founded by members of the Loo group, Marquardt will design hardware to monitor and control the solar cells via the internet of things, integrate the solar cells with smart windows, and develop software to optimize the energy savings and benefit to occupants.

    Building better compost

    5
    Xinning Zhang. Photo by Chris Fascenelli, Office of Communications.

    A team of researchers will work with Princeton’s on-campus composting facility to explore conditions for creating high-quality compost that is high in nutrients and low in greenhouse gas emissions. The facility, known as the Sustainable Composting Research at Princeton (S.C.R.A.P.) Lab, houses a biodigester that converts campus food scraps into nutrient-rich plant food, helping to divert food waste from landfills and reduce reliance on chemical fertilizers. The biodigester consists of a large barrel that rotates to mix air with food waste and a carbon source — such as wood chips or cardboard — to aerobically decompose the materials into compost in just five days.

    The team, which will include an undergraduate researcher and be led by Xinning Zhang, assistant professor of geosciences and the Princeton Environmental Institute, will test various proportions of food waste, carbon inputs and air as well as operating conditions to identify conditions that create compost with superior levels of nutrients while reducing the natural emission of greenhouse gases due to biodegradation of compostable materials. The team will also explore the use of waste cardboard from the campus to replace wood chips.

    Farming on campus lands

    6
    Daniel Rubenstein and Gina Talt. Photos by Igor Heifetz and Denise Applewhite, Office of Communications.

    A new study will explore how to improve Princeton’s land stewardship practices in ways that encourage sustainability while improving agricultural yield. Princeton University enables local farmers to raise crops on large portions of its land, but in recent years farmers have reported finding it hard to make a profit due to crop consumption by deer. Additionally, years of growing monoculture crops with herbicides and fertilizers have led to nutrient-deficient soils and a system reliant on fossil-fuel-based inputs to suppress weeds.

    The project — led by Daniel Rubenstein, the Class of 1877 Professor of Zoology, a professor in the Department of Ecology and Evolutionary Biology, and director of the Princeton Environmental Institute’s certificate Program in Environmental Studies, along with Gina Talt, food systems project specialist with the Office of Sustainability — will involve undergraduates in examining the cost-effectiveness of fencing the lands to keep out deer while also exploring a variety of soil enriching and anti-weed control methods. The team will grow field corn in one-acre test plots, including fenced and non-fenced areas, to compare how farming practices affect crop growth, soil health and farmland profitability. The sustainable practices to be tested include applying compost made from campus food scraps, planting cover crops during the off-season, and weeding with equipment rather than applying herbicides.

    See the full article here .

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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 2:58 pm on March 13, 2019 Permalink | Reply
    Tags: "Astronomers discover 83 supermassive black holes in the early universe", , , , , Princeton University,   

    From Princeton University: “Astronomers discover 83 supermassive black holes in the early universe” 

    Princeton University
    From Princeton University

    March 13, 2019
    Liz Fuller-Wright

    Astronomers from Japan, Taiwan and Princeton University have discovered 83 quasars powered by supermassive black holes in the distant universe, from a time when the universe was less than 10 percent of its present age.

    “It is remarkable that such massive dense objects were able to form so soon after the Big Bang,” said Michael Strauss, a professor of astrophysical sciences at Princeton University who is one of the co-authors of the study. “Understanding how black holes can form in the early universe, and just how common they are, is a challenge for our cosmological models.”

    This finding increases the number of black holes known at that epoch considerably, and reveals, for the first time, how common they are early in the universe’s history. In addition, it provides new insight into the effect of black holes on the physical state of gas in the early universe in its first billion years. The research appears in a series of five papers published in The Astrophysical Journal and the Publications of the Astronomical Observatory of Japan.

    2
    Light from one of the most distant quasars known, powered by a supermassive black hole lying 13.05 billion light-years away from Earth. The image was obtained by the Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope. The other objects in the field are mostly stars in our Milky Way or galaxies along the line of sight. Image courtesy of the National Astronomical Observatory of Japan

    NAOJ Subaru Hyper Suprime-Cam


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    Supermassive black holes, found at the centers of galaxies, can be millions or even billions of times more massive than the sun. While they are prevalent today, it is unclear when they first formed, and how many existed in the distant early universe. A supermassive black hole becomes visible when gas accretes onto it, causing it to shine as a “quasar.” Previous studies have been sensitive only to the very rare, most luminous quasars, and thus the most massive black holes. The new discoveries probe the population of fainter quasars, powered by black holes with masses comparable to most black holes seen in the present-day universe.

    3
    An artist’s impression of a quasar. A supermassive black hole sits at the center, and the gravitational energy of material accreting onto it is released as light.
    Image courtesy of Yoshiki Matsuoka

    HSC has a gigantic field-of-view — 1.77 degrees across, or seven times the area of the full moon — mounted on one of the largest telescopes in the world. The HSC team is surveying the sky over the course of 300 nights of telescope time, spread over five years.

    The team selected distant quasar candidates from the sensitive HSC survey data. They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope [above]; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile.


    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level


    Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    The team selected distant quasar candidates from the sensitive HSC survey data. They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile. The survey has revealed 83 previously unknown very distant quasars. Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year — in other words, if you chunked the universe into imaginary cubes that are a billion light-years on a side, each would hold one supermassive black hole.

    4
    The 100 quasars identified from the HSC data. The top seven rows show the 83 newly discovered quasars while the bottom two rows represent 17 previously known quasars in the survey area. They appear extremely red due to the cosmic expansion and absorption of light in intergalactic space. All the images were obtained by HSC.
    Image courtesy of the National Astronomical Observatory of Japan

    The sample of quasars in this study are about 13 billion light-years away from the Earth; in other words, we are seeing them as they existed 13 billion years ago. As the Big Bang took place 13.8 billion years ago, we are effectively looking back in time, seeing these quasars and supermassive black holes as they appeared only about 800 million years after the creation of the (known) universe.

    5
    If the history of the universe from the Big Bang to the present were laid out on a football field, Earth and our solar system would not appear until our own 33-yard line. Life appeared just inside the 28-yard line and dinosaurs went extinct halfway between the 1-yard line and the goal. All of human history, since hominids first climbed out of trees, takes place within an inch of the goal line. On this timeline, the supermassive black holes discovered by Princeton astrophysicist Michael Strauss and his international team of colleagues would appear back on the universe’s 6-yard line, very shortly after the Big Bang itself.
    Image by Kyle McKernan, Office of Communications

    The survey has revealed 83 previously unknown very distant quasars. Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year — in other words, if you chunked the universe into imaginary cubes that are a billion light-years on a side, each would hold one supermassive black hole.

    It is widely accepted that the hydrogen in the universe was once neutral, but was “reionized” — split into its component protons and electrons — around the time when the first generation of stars, galaxies and supermassive black holes were born, in the first few hundred million years after the Big Bang. This is a milestone of cosmic history, but astronomers still don’t know what provided the incredible amount of energy required to cause the reionization. A compelling hypothesis suggests that there were many more quasars in the early universe than detected previously, and it is their integrated radiation that reionized the universe.

    “However, the number of quasars we observed shows that this is not the case,” explained Robert Lupton, a 1985 Princeton Ph.D. alumnus who is a senior research scientist in astrophysical sciences. “The number of quasars seen is significantly less than needed to explain the reionization.” Reionization was therefore caused by another energy source, most likely numerous galaxies that started to form in the young universe.

    The present study was made possible by the world-leading survey ability of Subaru and HSC. “The quasars we discovered will be an interesting subject for further follow-up observations with current and future facilities,” said Yoshiki Matsuoka, a former Princeton postdoctoral researcher now at Ehime University in Japan, who led the study. “We will also learn about the formation and early evolution of supermassive black holes, by comparing the measured number density and luminosity distribution with predictions from theoretical models.”

    Based on the results achieved so far, the team is looking forward to finding yet more distant black holes and discovering when the first supermassive black hole appeared in the universe.

    The HSC collaboration includes astronomers from Japan, Taiwan and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University.

    The results of the present study are published in the following five papers — the second paper in particular.

    [1] “Discovery of the First Low-luminosity Quasar at z > 7”, by Yoshiki Matsuoka1, Masafusa Onoue2, Nobunari Kashikawa3,4,5, Michael A Strauss6, Kazushi Iwasawa7, Chien-Hsiu Lee8, Masatoshi Imanishi4,5, Tohru Nagao and 40 co-authors, including Princeton astrophysicists James Bosch, James Gunn, Robert Lupton and Paul Price, appeared in the Feb. 6 issue of The Astrophysical Journal Letters, 872 (2019),

    [2] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6,” appeared in the Dec. 20 issue of The Astrophysical Journal, 869 (2018), 150

    [3] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 ≤ z ≤ 6.9,” was published July 3, 2018 in The Astrophysical Journal Supplement Series, 237 (2018), 5

    [4] “Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 quasars and luminous galaxies at 5.7 < z ≤ 6.8,” was published July 5, 2017 in Publications of the Astronomical Society of Japan, 70 (2018), S35

    [5] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). I. Discovery of 15 Quasars and Bright Galaxies at 5.7 < z < 6.9”, was published Aug. 25, 2016 in The Astrophysical Journal, 828 (2016), 26 .

    See the full article here .

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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 11:52 am on December 19, 2018 Permalink | Reply
    Tags: AdS/CFT, Beyond Einstein: Physicists find surprising connections in the cosmos, , From tiny bits of string, , Our world when we get down to the level of particles is a quantum world, , Princeton University, Relatability between gravity and subatomic particles provides a sort of Rosetta stone for physics, The idea that fundamental particles are actually tiny bits of vibrating string was taking off and by the mid-1980s “string theory” had lassoed the imaginations of many leading physicists,   

    From Princeton University: “Beyond Einstein: Physicists find surprising connections in the cosmos” 

    Princeton University
    From Princeton University

    Dec. 17, 2018
    Catherine Zandonella

    1
    Gravity, the force that brings baseballs back to Earth and governs the growth of black holes, is mathematically relatable to the peculiar antics of the subatomic particles that make up all the matter around us. Illustration by J.F. Podevin

    Albert Einstein’s desk can still be found on the second floor of Princeton’s physics department. Positioned in front of a floor-to-ceiling blackboard covered with equations, the desk seems to embody the spirit of the frizzy-haired genius as he asks the department’s current occupants, “So, have you solved it yet?”

    Einstein never achieved his goal of a unified theory to explain the natural world in a single, coherent framework. Over the last century, researchers have pieced together links between three of the four known physical forces in a “standard model,” but the fourth force, gravity, has always stood alone.

    No longer. Thanks to insights made by Princeton faculty members and others who trained here, gravity is being brought in from the cold — although in a manner not remotely close to how Einstein had imagined it.

    Though not yet a “theory of everything,” this framework, laid down over 20 years ago and still being filled in, reveals surprising ways in which Einstein’s theory of gravity relates to other areas of physics, giving researchers new tools with which to tackle elusive questions.

    The key insight is that gravity, the force that brings baseballs back to Earth and governs the growth of black holes, is mathematically relatable to the peculiar antics of the subatomic particles that make up all the matter around us.

    This revelation allows scientists to use one branch of physics to understand other seemingly unrelated areas of physics. So far, this concept has been applied to topics ranging from why black holes run a temperature to how a butterfly’s beating wings can cause a storm on the other side of the world.

    This relatability between gravity and subatomic particles provides a sort of Rosetta stone for physics. Ask a question about gravity, and you’ll get an explanation couched in the terms of subatomic particles. And vice versa.

    “This has turned out to be an incredibly rich area,” said Igor Klebanov, Princeton’s Eugene Higgins Professor of Physics, who generated some of the initial inklings in this field in the 1990s. “It lies at the intersection of many fields of physics.”

    From tiny bits of string

    The seeds of this correspondence were sprinkled in the 1970s, when researchers were exploring tiny subatomic particles called quarks. These entities nest like Russian dolls inside protons, which in turn occupy the atoms that make up all matter. At the time, physicists found it odd that no matter how hard you smash two protons together, you cannot release the quarks — they stay confined inside the protons.

    One person working on quark confinement was Alexander Polyakov, Princeton’s Joseph Henry Professor of Physics. It turns out that quarks are “glued together” by other particles, called gluons. For a while, researchers thought gluons could assemble into strings that tie quarks to each other. Polyakov glimpsed a link between the theory of particles and the theory of strings, but the work was, in Polyakov’s words, “hand-wavy” and he didn’t have precise examples.

    Meanwhile, the idea that fundamental particles are actually tiny bits of vibrating string was taking off, and by the mid-1980s, “string theory” had lassoed the imaginations of many leading physicists. The idea is simple: just as a vibrating violin string gives rise to different notes, each string’s vibration foretells a particle’s mass and behavior. The mathematical beauty was irresistible and led to a swell of enthusiasm for string theory as a way to explain not only particles but the universe itself.

    One of Polyakov’s colleagues was Klebanov, who in 1996 was an associate professor at Princeton, having earned his Ph.D. at Princeton a decade earlier. That year, Klebanov, with graduate student Steven Gubser and postdoctoral research associate Amanda Peet, used string theory to make calculations about gluons, and then compared their findings to a string-theory approach to understanding a black hole. They were surprised to find that both approaches yielded a very similar answer. A year later, Klebanov studied absorption rates by black holes and found that this time they agreed exactly.

    That work was limited to the example of gluons and black holes. It took an insight by Juan Maldacena in 1997 to pull the pieces into a more general relationship. At that time, Maldacena, who had earned his Ph.D. at Princeton one year earlier, was an assistant professor at Harvard. He detected a correspondence between a special form of gravity and the theory that describes particles. Seeing the importance of Maldacena’s conjecture, a Princeton team consisting of Gubser, Klebanov and Polyakov followed up with a related paper formulating the idea in more precise terms.

    Another physicist who was immediately taken with the idea was Edward Witten of the Institute for Advanced Study (IAS), an independent research center located about a mile from the University campus. He wrote a paper that further formulated the idea, and the combination of the three papers in late 1997 and early 1998 opened the floodgates.

    “It was a fundamentally new kind of connection,” said Witten, a leader in the field of string theory who had earned his Ph.D. at Princeton in 1976 and is a visiting lecturer with the rank of professor in physics at Princeton. “Twenty years later, we haven’t fully come to grips with it.”

    2

    Two sides of the same coin

    This relationship means that gravity and subatomic particle interactions are like two sides of the same coin. On one side is an extended version of gravity derived from Einstein’s 1915 theory of general relativity. On the other side is the theory that roughly describes the behavior of subatomic particles and their interactions.

    The latter theory includes the catalogue of particles and forces in the “standard model” (see sidebar), a framework to explain matter and its interactions that has survived rigorous testing in numerous experiments, including at the Large Hadron Collider.

    In the standard model, quantum behaviors are baked in. Our world, when we get down to the level of particles, is a quantum world.

    Notably absent from the standard model is gravity. Yet quantum behavior is at the basis of the other three forces, so why should gravity be immune?

    The new framework brings gravity into the discussion. It is not exactly the gravity we know, but a slightly warped version that includes an extra dimension. The universe we know has four dimensions, the three that pinpoint an object in space — the height, width and depth of Einstein’s desk, for example — plus the fourth dimension of time. The gravitational description adds a fifth dimension that causes spacetime to curve into a universe that includes copies of familiar four-dimensional flat space rescaled according to where they are found in the fifth dimension. This strange, curved spacetime is called anti-de Sitter (AdS) space after Einstein’s collaborator, Dutch astronomer Willem de Sitter.

    The breakthrough in the late 1990s was that mathematical calculations of the edge, or boundary, of this anti-de Sitter space can be applied to problems involving quantum behaviors of subatomic particles described by a mathematical relationship called conformal field theory (CFT). This relationship provides the link, which Polyakov had glimpsed earlier, between the theory of particles in four space-time dimensions and string theory in five dimensions. The relationship now goes by several names that relate gravity to particles, but most researchers call it the AdS/CFT (pronounced A-D-S-C-F-T) correspondence.

    3

    Tackling the big questions

    This correspondence, it turns out, has many practical uses. Take black holes, for example. The late physicist Stephen Hawking startled the physics community by discovering that black holes have a temperature that arises because each particle that falls into a black hole has an entangled particle that can escape as heat.

    Using AdS/CFT, Tadashi Takayanagi and Shinsei Ryu, then at the University of California-Santa Barbara, discovered a new way to study
    entanglement in terms of geometry, extending Hawking’s insights in a fashion that experts consider quite remarkable.

    In another example, researchers are using AdS/CFT to pin down chaos theory, which says that a random and insignificant event such as the flapping of a butterfly’s wings could result in massive changes to a large-scale system such as a faraway hurricane. It is difficult to calculate chaos, but black holes — which are some of the most chaotic quantum systems possible — could help. Work by Stephen Shenker and Douglas Stanford at Stanford University, along with Maldacena, demonstrates how, through AdS/CFT, black holes can model quantum chaos.

    One open question Maldacena hopes the AdS/CFT correspondence will answer is the question of what it is like inside a black hole, where an infinitely dense region called a singularity resides. So far, the relationship gives us a picture of the black hole as seen from the outside, said Maldacena, who is now the Carl P. Feinberg Professor at IAS.

    “We hope to understand the singularity inside the black hole,” Maldacena said. “Understanding this would probably lead to interesting lessons for the Big Bang.”

    The relationship between gravity and strings has also shed new light on quark confinement, initially through work by Polyakov and Witten, and later by Klebanov and Matt Strassler, who was then at IAS.

    Those are just a few examples of how the relationship can be used. “It is a tremendously successful idea,” said Gubser, who today is a professor of physics at Princeton. “It compels one’s attention. It ropes you in, it ropes in other fields, and it gives you a vantage point on theoretical physics that is very compelling.”

    The relationship may even unlock the quantum nature of gravity. “It is among our best clues to understand gravity from a quantum perspective,” said Witten. “Since we don’t know what is still missing, I cannot tell you how big a piece of the picture it ultimately will be.”

    Still, the AdS/CFT correspondence, while powerful, relies on a simplified version of spacetime that is not exactly like the real universe. Researchers are working to find ways to make the theory more broadly applicable to the everyday world, including Gubser’s research on modeling the collisions of heavy ions, as well as high-temperature superconductors.

    Also on the to-do list is developing a proof of this correspondence that draws on underlying physical principles. It is unlikely that Einstein would be satisfied without a proof, said Herman Verlinde, Princeton’s Class of 1909 Professor of Physics, the chair of the Department of Physics and an expert in string theory, who shares office space with Einstein’s desk.

    “Sometimes I imagine he is still sitting there,” Verlinde said, “and I wonder what he would think of our progress.”

    See the full article here .

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    Please help promote STEM in your local schools.

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 1:27 pm on October 24, 2018 Permalink | Reply
    Tags: Biermann battery effect, , , , Princeton University,   

    From COSMOS Magazine: “Supercomputer finds clues to violent magnetic events” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    24 October 2018
    Phil Dooley

    1
    An aurora over Iceland, the product of sudden magnetic reconnection. Credit Natthawat/Getty Images

    Researchers are a step closer to understanding the violent magnetic events that cause the storms on the sun’s surface and fling clouds of hot gas out into space, thanks to colossal computer simulations at Princeton University in the US.

    The disruptions in the magnetic field, known as magnetic reconnections, are common in the universe – the same process causes the aurora in high latitude skies – but existing models are unable to explain how they happen so quickly.

    A team led by Jackson Matteucci decided to investigate by building a full three-dimensional simulation of the ejected hot gas, something that required enormous computing power. The results are published in the journal Physical Review Letters.

    The researchers modelled more than 200 million particles using Titan, the biggest supercomputer [no longer true, the writer should have known that] in the US.

    ORNL Cray Titan XK7 Supercomputer, once the fastest in the world.

    They discovered that a three-dimensional interaction called the Biermann battery effect was at the heart of the sudden reconnection process.

    Discovered in the fifties by German astrophysicist Ludwig Biermann, the Biermann battery effect shows how magnetic fields can be generated in charged gases, known as plasma.

    In such plasmas, if a region develops in which there is a temperature gradient at right angles to a density gradient, a magnetic field is created that encircles it.

    Astrophysicists propose that this effect might take place in interstellar plasma clouds, such as nebulae, and generate the cosmic magnetic fields that we see throughout the universe.

    In contrast with the huge scale of cosmic plasma clouds, magnetic reconnection happens at a scale of microns when two magnetic fields collide, says Matteucci.

    He likens the process to collisions between two sizable handfuls of rubber bands. In stable circumstances the magnetic field lines are loops, like the bands. But sometimes turbulence in the plasma pushes these band analogues together so forcefully that they sever and reconnect to different ones, thus forming loops at different orientations.

    Some of the new loops are stretched taut and snap back, providing the energy that ejects material so violently, and causes magnetic storms or glowing auroras.

    The Princeton simulation showed that as the fields collide there is a sudden spike in the temperature in a very localised region, which sets off the Biermann battery effect, suddenly creating a new magnetic field in the midst of the collision. It’s this newly-appearing field that severs the lines and allows them to reconfigure.

    Although Matteucci’s simulations are for tiny plasma clouds generated by lasers hitting foil, he says they could help us understand large-scale processes in the atmosphere.

    “If you do a back of the envelope calculation, you find it could play an important role in reconnection in the magnetosphere, where the solar wind collides with the Earth’s magnetic field,” he says.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

     
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