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  • richardmitnick 2:05 pm on December 6, 2019 Permalink | Reply
    Tags: , Computational Solid Mechanics, , , Weizmann Institute of Science   

    From École Polytechnique Fédérale de Lausanne: “Gaining insight into the energy balance of earthquakes” 


    From École Polytechnique Fédérale de Lausanne

    06.12.19
    Sarah Aubort

    1
    Researchers at EPFL’s Computational Solid Mechanics Laboratory and the Weizmann Institute of Science have modeled the onset of slip between two bodies in frictional contact. Their work, a major step forward in the study of frictional rupture, could give us a better understanding of earthquakes – including how far and fast they travel.

    It’s still impossible to determine where and when an earthquake will occur. For example, California has for years been under the threat of the “Big One,” and closer to home, a recent series of small shocks in Valais Canton in early November has raised fears of a major earthquake in the region. Although we can’t predict earthquakes, researchers from EPFL and the Weizmann Institute of Science in Israel have made a step forward in assessing earthquake dynamics through a better understanding of how frictional slip – the relative motion of two bodies in contact under shear stress, such as tectonic plates – begins. Their work has been published in two complementary parts, in Physical Review X and Earth and Planetary Science Letters.

    “We wanted to understand what happens when two bodies in frictional contact suddenly start moving following a gradual increase of the shear stress: the way they start sliding will determine the speed and extent of the movement and, potentially, the severity of an earthquake,” explains Fabian Barras, a doctoral assistant at EPFL’s Computational Solid Mechanics Laboratory (LSMS) during this research, and first author of both articles.

    Parallels between slip front and fracture

    The way in which frictional sliding begins between two bodies is not as uniform as it appears. Ultrafast cameras show that slip starts at a specific point and then spreads to the rest of the surface. “This slip front dynamics is very similar to the way a crack propagates within a brittle material,” says Barras. The researchers’ first publication looks at the similarities between frictional rupture and dynamic fracture. “Although the physics of a crack and a slip front is not exactly the same, they both propagate because of a drop in the material’s load-bearing capacity behind the rupture. Using the analogy with dynamic fracture, we studied the origin of the drop of frictional stress observed in the wake of a slip front when the interface starts to move.”

    The researchers then looked at the concentration of stress at the slip front and used theoretical tools from the field of rupture dynamics to study the energy balance. Unlike the situation with a crack, friction continues to dissipate energy after slip has started. During an earthquake, only part of the available energy is used to propagate the rupture front, and the remainder is dissipated by friction, mainly in the form of heat. It is here that the researchers were able to revise previously used models and achieve a better understanding of how much frictional energy is involved in the propagation of the rupture front.

    They used high-performance computers to simulate seismic ruptures based on generic laws of friction, which reproduce the change in frictional force depending on the slip velocity measured between different types of materials. Using dynamic rupture theory and applying it to friction, the researchers were able to assess laboratory experiments and ensure that their predictions were correct. “We were able to validate our predictions across a wide range of experimentally observed rupture velocities. The theoretical models we developed could in the future help us better understand why certain earthquakes in nature are fast and violent, while others propagate slowly and occur over longer periods of time,” adds Barras.

    Deep geothermal energy and induced seismicity

    These advances in fundamental research could one day be applied to more complex models, such as those representing conditions along tectonic faults, especially where fluids are naturally present or injected into the ground. “Today, several promising technologies in the context of the energy transition – like deep geothermal energy – relies on underground fluid injection. It is important to have a better understanding of how those injections affect seismic activity. I hope to use the tools developed during my PhD to study that impact,” says Barras.

    “This work shows how research developed in a civil engineering laboratory can have very interesting implications for earthquake science and lead to cutting-edge publications in areas such as physics,” says Professor Jean-François Molinari, the head of EPFL’s Computational Solid Mechanics Laboratory. Fabian Barras has also received a grant from the Swiss National Science Foundation to continue his research in a laboratory specializing in fault geology at the University of Oslo.

    2
    Between two solids in frictional contact, slip nucleates at a point on the surface (corresponding to the hypocenter of an earthquake) before spreading to the rest of the interface – just like a crack growing through a brittle material. Using numerical simulation, researchers computed the shear stress profile after the onset of slip and studied the drop of frictional stress observed behind the rupture fronts (blue area in the inset).

    Funding

    This research was made possible through funding from the Swiss National Science Foundation (Grant No. 162569, Fabian Barras PhD), as well as from the Rothschild Caesarea Foundation in order to kick off a collaboration between Jean-François Molinari’s lab at EPFL and Eran Bouchbinder’s theoretical physics group at Weizmann. Eran Bouchbinder would also like to thank the Israel Science Foundation for its support (Grant No. 295/16).

    See the full article here .

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    EPFL bloc

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 2:37 pm on October 28, 2019 Permalink | Reply
    Tags: A decisive function for the young field of multi-messenger astronomy (MMA)., , New insights into high-energy phenomena such as supernova explosions; colliding neutron stars and active black holes., The satellite will search for the origin of the heavy chemical elements., The UV camera which DESY is developing and building will be the heart of the telescope., ULTRASAT satellite, ULTRASAT will study the sky in the ultraviolet range (220 to 280 nanometres wavelength) of the electromagnetic spectrum., Weizmann Institute of Science   

    From DESY: “UV Satellite Will Open New View on Exploding Stars and Black Holes” 

    DESY
    From DESY

    2019/10/28

    DESY to build 100-megapixel camera for Israeli space telescope.

    A new space telescope will open up an unprecedented view of the universe in ultraviolet light: The ULTRASAT satellite will provide fundamental new insights into high-energy phenomena such as supernova explosions, colliding neutron stars and active black holes, all of which can also generate gravitational waves and act as cosmic particle accelerators. On Monday in Rehovot, Israel, the President of the Helmholtz Association, Otmar D. Wiestler, and the Director of the Helmholtz centre DESY, Helmut Dosch, agreed with the Weizmann Institute of Science on a cooperation for German participation in the Israeli-led project. DESY will build the 100-megapixel UV camera for the space telescope. For the project, DESY is working with the German Aerospace Center DLR, which also is a member of the Helmholtz Association.

    Weizmann Institute Campus

    “Helmholtz has had many excellent scientific collaborations with Israeli partners for decades. Together with the Weizmann Institute of Science, we are now taking another important step in the field of astrophysics. I am extremely pleased about this,” said Helmholtz President Otmar D. Wiestler. “The cooperation on the ULTRASAT space telescope has the potential to create a completely new basis for the detection of gravitational waves and related astrophysical events, at the highest international level.”

    DESY Director Helmut Dosch added: “We have a long and fruitful cooperation with a number of Israeli partners. We are now continuing this success story with our participation in Weizmann Institute of Science’s challenging satellite project.” DESY’s Research Director for Astroparticle Physics, Christian Stegmann, emphasised: “ULTRASAT offers us unique insights into the high-energy universe. With the camera for the telescope, DESY will be able to combine and contribute its outstanding expertise in detector development for astroparticle physics and X-ray physics.”

    ULTRASAT will study the sky in the ultraviolet range (220 to 280 nanometres wavelength) of the electromagnetic spectrum and have a particularly large field of view of 225 square degrees – about 1200 times as large as the full moon appears in our sky. “This unique configuration will help us answer some of the big questions in astrophysics,” said Eli Waxman, principal investigator of ULTRASAT at the Weizmann Institute of Science.

    2
    Collage of the satellite with typical observation targets like supernova explosions (top left), merging neutron stars (bottom left) and active black holes (top right). Photomontage: DESY, with material from NASA and Weizmann Institute of Science

    For example, the satellite will search for the origin of the heavy chemical elements. Apart from the lightest elements like hydrogen and helium, the elements were almost exclusively created by nuclear fusion in the cosmos. Stars produce their energy from this nuclear fusion, but this only works up to iron. The fusion of heavier elements such as lead or gold costs energy. Their synthesis takes place in the most powerful processes in the universe, such as the explosion of a star as a supernova or the collision of two neutron stars – the nuclei of burnt-out suns that have collapsed under their own weight to such an extent that they have a density like a gigantic atomic nucleus. Every gold atom on Earth and in the rest of the cosmos comes from an exploding sun or from a neutron star crash.

    “We want to understand exactly how the elements are produced and how they are distributed,” explains David Berge, Lead Scientist at DESY. Both, supernova explosions and neutron star collisions can be followed particularly well in UV light, as Berge points out. “The direct phase of a supernova in the first minutes, hours and days is mainly seen in the UV. During this time, the UV light contains characteristic signatures that indicate the predecessor star.” Later, a shockwave breaks out of the hot fireball, within which charged subatomic particles are also accelerated to high energies. “The satellite can therefore help us to understand the origin of such cosmic particle accelerators,” says Berge. “We also want to find out which type of star explodes in which kind of supernova.”

    ULTRASAT is particularly sensitive to high-energy phenomena. “Everything that gets extremely hot shines brightly in the UV light,” reports DESY researcher Rolf Bühler, project manager for the UV camera. This includes active black holes, which absorb matter from their environment and also accelerate particles, and colliding neutron stars. The observation of neutron star crashes can not only provide information about element synthesis in the cosmos, but is also of great importance for gravitational wave research. “If gravitational waves are registered by merging neutron stars, their position can so far only be coarsely resolved on the basis of the gravitational wave data,” explains Bühler. “ULTRASAT can orient itself to the target region within a maximum of 30 minutes and, thanks to its large field of view, can then determine the exact position almost immediately.”

    3
    Infographic: DESY, Sven Stein

    The satellite thus has a decisive function for the young field of multi-messenger astronomy (MMA), which studies the universe via various messengers such as cosmic particles, gravitational waves and electromagnetic radiation and forms a new area of research at DESY. With its large field of view, the satellite will have a particularly large section of the sky in view and will thus also be able to detect unknown objects that suddenly flare up in the UV range.

    With a total weight of only 160 kilograms and a volume of less than one cubic metre, ULTRASAT (Ultraviolet Transient Astronomy Satellite) is a small scientific satellite. The Weizmann Institute of Science and the Israeli Space Agency ISA share funding and management. The launch is scheduled for 2023. The space telescope will then collect data for three years. It will be put in a high orbit about 35,000 kilometres above Earth’s surface. This guarantees that disturbances from the ultraviolet background radiation, which Earth’s atmosphere reflects from the sun, are negligible and allows large areas of the sky to be surveyed. UV radiation can only be observed from orbit because it is largely absorbed and reflected by the atmosphere.

    The UV camera, which DESY is developing and building, will be the heart of the telescope. It will have a UV-sensitive sensor area of nine by nine centimetres and a resolution of 100 megapixels. With these parameters, the developers are breaking new ground: A UV space camera with such a resolution and sensitivity has never been built before. For the camera, DESY experts in astroparticle physics work together with specialists in detector development from the field of research with synchrotron radiation. With this project, DESY is contributing about 5 million euros to the satellite, which will cost about 70 million euros in total.

    See the full article here .


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    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 10:44 am on January 21, 2019 Permalink | Reply
    Tags: , , , , , , , , , Weizmann Institute of Science   

    Weizmann Institute of Science via Science Alert: “We Just Got Lab-Made Evidence of Stephen Hawking’s Greatest Prediction About Black Holes” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    via

    ScienceAlert

    Science Alert

    21 JAN 2019
    MICHELLE STARR

    Scientists may have just taken a step towards experimentally proving the existence of Hawking radiation. Using an optical fibre analogue of an event horizon – a lab-created model of black hole physics – researchers from Weizmann Institute of Science in Rehovot, Israel report that they have created stimulated Hawking radiation.

    Under general relativity, a black hole is inescapable. Once something travels beyond the event horizon into the heart of the black hole, there’s no return. So intense is the gravitational force of a black hole that not even light – the fastest thing in the Universe – can achieve escape velocity.

    Under general relativity, therefore, a black hole emits no electromagnetic radiation. But, as a young Stephen Hawking theorised in 1974, it does emit something when you add quantum mechanics to the mix.

    This theoretical electromagnetic radiation is called Hawking radiation; it resembles black body radiation, produced by the temperature of the black hole, which is inversely proportional to its mass (watch the video below to get a grasp of this neat concept).

    This radiation would mean that black holes are extremely slowly and steadily evaporating, but according to the maths, this radiation is too faint to be detectable by our current instruments.

    So, cue trying to recreate it in a lab using black hole analogues. These can be built from things that produce waves, such as fluid and sound waves in a special tank, from Bose-Einstein condensates, or from light contained in optical fibre.

    “Hawking radiation is a much more general phenomenon than originally thought,” explained physicist Ulf Leonhardt to Physics World. “It can happen whenever event horizons are made, be it in astrophysics or for light in optical materials, water waves or ultracold atoms.”

    These won’t, obviously, reproduce the gravitational effects of a black hole (a good thing for, well, us existing), but the mathematics involved is analogous to the mathematics that describe black holes under general relativity.

    This time, the team’s method of choice was an optical fibre system developed by Leonhardt some years ago.

    The optical fibre has micro-patterns on the inside, and acts as a conduit. When entering the fibre, light slows down just a tiny bit. To create an event horizon analogue, two differently coloured ultrafast pulses of laser light are sent down the fibre. The first interferes with the second, resulting in an event horizon effect, observable as changes in the refractive index of the fibre.

    The team then used an additional light on this system, which resulted in an increase in radiation with a negative frequency. In other words, ‘negative’ light was drawing energy from the ‘event horizon’ – an indication of stimulated Hawking radiation.

    While the findings were undoubtedly cool, the end goal for such research is to observe spontaneous Hawking radiation.

    Stimulated emission is exactly what it sounds like – emission that requires an external electromagnetic stimulus. Meanwhile the Hawking radiation emanating from a black hole would be of the spontaneous variety, not stimulated.

    There are other problems with stimulated Hawking radiation experiments; namely, they are rarely unambiguous, since it’s impossible to precisely recreate in the lab the conditions around an event horizon.

    With this experiment, for example, it’s difficult to be 100 percent certain that the emission wasn’t created by an amplification of normal radiation, although Leonhardt and his team are confident that their experiment did actually produce Hawking radiation.

    Either way, it’s a fascinating achievement and has landed another mystery in the team’s hands, too – they found the result was not quite as they expected.

    “Our numerical calculations predict a much stronger Hawking light than we have seen,” Leonhardt told Physics World.

    “We plan to investigate this next. But we are open to surprises and will remain our own worst critics.”

    The research has been published in the journal Physical Review Letters.

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 6:38 pm on June 5, 2018 Permalink | Reply
    Tags: A regular quantum computer — one without non-Abelian anyons — would require error correction, Abelian anyons behave more or less like conventional fermions, , But an even more powerful computational platform would come from what’s known as parafermions which have been theorized but not yet shown to exist. Perhaps their existence could also be proven with , Eliminate error correction which is a major stumbling block in the development of quantum computers, For one useful quantum bit of information you need multiple additional quantum bits to correct errors that arise from random fluctuations in the system, Non-Abelian anyons are for lack of a better way of saying it completely insane. They have very strange properties that could be used in quantum computing or more specifically for what’s known as top, Non-Abelian anyons- quantum quasi-particles that retain a “memory” of their relative positions in the past, , Quantum Hall liquid, This work suggests that a particular entity known as a Majorana particle is at work in the particular system that we studied. And that suggests that a Majorana-based quantum computer is possible., topological quantum computing — which requires the presence of non-Abelian anyons — is unique in that it doesn’t need error correction to make the quantum bits useful, Weizmann Institute of Science   

    From Brown University: “New research hints at ‘insane’ particles useful in quantum computing” 

    Brown University
    From Brown University

    June 5, 2018
    Kevin Stacey
    kevin_stacey@brown.edu

    1
    Quantum heat. An image of the experimental setup used to produce evidence of strange quasi-particles called non-Abelian anyons.
    A new measurement of heat conduction in an exotic state of matter points to the presence of strange particles that could be useful in quantum computers.

    In a paper published this week in the journal Nature, a research team including a Brown University physicist has characterized how heat is conducted in a matter state known as a quantum Hall liquid, in which electrons are confined to two dimensions. The findings suggest the presence of non-Abelian anyons, quantum quasi-particles that retain a “memory” of their relative positions in the past. Theorists have suggested that the ability of these particles to retain information could be useful in developing ultra-fast quantum computing systems that don’t require error correction, which is a major stumbling block in the development of quantum computers.

    The research was led by an experimental group at the Weizmann Institute of Science in Rehovot, Israel.

    Weizmann Institute Campus


    Dmitri Feldman, a professor of physics at Brown, was part of the research group. He discussed the findings in an interview.

    Q: Could you explain more about what you and your colleagues found?

    A: We were looking at thermal conductance — which simply means the flow of heat from a higher temperature to a lower temperature — in what’s known as a 5/2 quantum Hall liquid. Quantum Hall liquids are not ‘liquids’ in the conventional sense of the word. The term refers to the behavior of electrons inside certain materials when the electrons become confined in two dimensions in a strong magnetic field.

    What we found was that the quantized heat conductance — meaning a fundamental unit of conductance — in this system is fractional. In other words, the value was not an integer, and that has interesting implications for what’s happening in the system. When the quantum thermal conductance is not an integer, it means that quasi-particles known as non-Abelian anyons are present in this system.

    Q: Can you explain more about non-Abelian anyons?

    A: In the Standard Model of particle physics, there are only two categories of particles: fermions and bosons.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Standard Model of Particle Physics from Symmetry Magazine

    That’s all there is in the world we experience on a daily basis. But in two-dimensional systems like quantum Hall liquids, there can be other types of particles known as anyons. Generally speaking, there are two types of anyons: Abelian anyons and non-Abelian anyons. Abelian anyons behave more or less like conventional fermions, but non-Abelian anyons are, for lack of a better way of saying it, completely insane. They have very strange properties that could be used in quantum computing, or more specifically, for what’s known as topological quantum memory.

    Q: What’s the connection between non-Abelian anyons and quantum computing?

    A: A regular quantum computer — one without non-Abelian anyons — would require error correction. For one useful quantum bit of information, you need multiple additional quantum bits to correct errors that arise from random fluctuations in the system. That’s extremely demanding and a big problem in quantum computing. But topological quantum computing — which requires the presence of non-Abelian anyons — is unique in that it doesn’t need error correction to make the quantum bits useful. That’s because in a non-Abelian system, you can produce states that are completely indistinguishable locally, but globally the states are completely different. So you can have random perturbations of these local quantum numbers, but it won’t change the global quantum numbers, which means the information is safe.

    Q: Where does this line of research go from here?

    A: This work suggests that a particular entity known as a Majorana particle is at work in the particular system that we studied. And that suggests that a Majorana-based quantum computer is possible. But an even more powerful computational platform would come from what’s known as parafermions, which have been theorized but not yet shown to exist. Perhaps their existence could also be proven with similar experimental tools in the future.

    See the full article here .

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    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 8:00 am on October 11, 2017 Permalink | Reply
    Tags: , , , Confirmed: cosmic rays blast from supernovae, Cosmic rays – high energy subatomic particles – are produced within at least one supernova, , GHaFaS, Weizmann Institute of Science   

    From Weizmann via COSMOS: “Confirmed: cosmic rays blast from supernovae” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    COSMOS
    11 October 2017
    Andrew Masterson

    An exploded star first seen by 500 years ago helps astrophysicists to solve a cosmic conundrum.

    1

    Left. Composite image of the remnant of Tycho Brahe’s supernova (1572) using data from the Chandra x-ray satellite observatory (yellow, green, blue (credits NASA/SAO), from the Spitzer infrared satellite observatory (red, credits, NASA/JPL-Caltech), and from the Calar Alto observatory (stars white, credit, Krause et al.). The transparent magenta box shows the field of the ACAM instrument at the Cassegrain focus of the William Herschel Telescope (WHT, ORM, La Palma). Centre, a zoom-in on the ACAM field with a green box showing the size of the field of the 2d spectrograph GHaFaS (WHT, ORM). Right. The reduced and integrated image of GHaFaS in the emission from ionized hydrogen (Ha). NASA/SAO, NASA/JPL-Caltech

    Ending an astronomical mystery, scientists have confirmed that cosmic rays – high energy subatomic particles – are produced within at least one supernova.

    The rays, which consist primarily of protons and atomic nuclei, continuously bombard the Earth’s atmosphere. It’s been known for decades that they originate from outside the solar system, even perhaps outside the galaxy, but how and where they are created has until now remained obscure.

    Now research published in The Astrophysical Journal finds that an as yet unknown mechanism within exploding stars is the likely source. The mechanism acts as an accelerator, producing an unexpectedly wide range of particle velocities that cannot be accounted for by the mass and temperature of the gases involved.

    The discovery was made by a team led by astrophysicist Sladjana Knežević of the Weizmann Institute of Science in Israel, using as instrument known as GHaFaS, mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory in the Canary Islands.


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

    The team focussed the instrument’s attention on a supernova known formally as SN 1572, but more commonly as Tycho’s supernova, after the pioneering astronomer Tycho Brahe who first recorded its existence in in 1572.

    3
    Remnant of SN 1572 as seen in X-ray light from the Chandra X-ray Observatory

    NASA/Chandra Telescope

    The supernova – more correctly, a supernova remnant – has been studied several times in recent years, including by British radio-astronomers in the 1950s, and observers at the California’s Mount Palomar Observatory a decade later. NASA’s orbiting Chandra X-ray Observatory imaged it in 2002

    Caltech Palomar Observatory, located in San Diego County, California, US, at 1,712 m (5,617 ft)

    None of these investigations, however, had sufficient resolution to test the hypothesis that supernovae may be the source of cosmic rays.

    Using the Canary Islands facility, Knežević and his colleagues mapped a section of the dissipating cloud that surrounds the Tycho remnant, including a bright, visible filament. Measuring two levels of hydrogen emission spread, the team found that the results only made sense if somewhere in the remnant an accelerator was producing high energy particles.

    The finding is the first time evidence for such a mechanism has been found, and appears to confirm supernovae as the source of cosmic rays.

    The data has important implications for both astrophysics and particle physics.

    The researchers now intend to combine their results with other measurements of Tycho’s supernova already taken by another facility on the Canary Islands, the larger Gran Telescopio Canariasto, to gain a clearer picture of cosmic ray acceleration.


    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

    See the full article here .

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    STEM Icon

    Stem Education Coalition

    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 12:29 pm on July 9, 2017 Permalink | Reply
    Tags: , , , Weizmann Institute of Science   

    From APS Physics: “Cooperating Lasers Make Topological Defects” 

    Physics LogoAbout Physics

    Physics Logo 2

    Physics

    July 7, 2017
    David Ehrenstein

    1
    A circle of ten interacting lasers (left) can cleanly synchronize their phases, as shown by the sharp distinctions between light and dark rings near the center. But using 20 lasers (right) leads to a 20% likelihood for topological defects, where each laser’s phase is offset from its neighbors’, leading to light and dark rings that are less sharply defined. V. Pal et al., Phys. Rev. Lett. (2017).

    If you cool molten iron slowly, the electron spins can gradually align in a single direction and produce a strong magnetic field. But rapid cooling leads to magnetic domains aligned in various directions, separated by thin boundaries called topological defects. A similar phenomenon may have occurred as the Universe rapidly cooled after the big bang. To study topological defect formation in the lab without the challenges of temperature control, Nir Davidson and colleagues at the Weizmann Institute, Israel, have now developed an experimental model involving interacting laser beams.

    Weizmann Institute Campus

    Imaging the laser intensities allows them to measure the likelihood for topological defects to form for a range of parameters such as the effective “cooling rate.”

    To create their experimental model, Davidson and colleagues placed a disk containing between 10 and 30 holes arranged in a circle inside a laser cavity. This “mask” produced a set of laser beams, each emerging from a different hole and leaking a bit into its two neighboring beams, generating interactions. These interactions caused the phase differences among the beams to change over time. The evolution was so rapid that the team simply observed the final state, by recording the resulting pattern of laser intensities.

    This state represented the combined effects of about 1000 different longitudinal modes in the cavity—essentially 1000 independent experiments running simultaneously, each with a different set of initial phase relationships among the lasers. In many cases, the beams quickly synchronized their phases, but for some initial phase relationships, the beams would get “stuck” in a state where each beam was a fixed phase away from its neighbors. The team showed that, with ten lasers, there are exactly eight of these topological defect states.

    Analysis of the laser patterns allowed the researchers to measure the likelihood of topological defect formation as they varied parameters such as the number of lasers in the ring and the power of the pump light inside the cavity. They found that, with increasing pump power, topological defects became increasingly likely. The team explains this result with simulations showing that the variations in intensity among the beams drop rapidly in time when the pump power is high, whereas low power is associated with slower intensity equilibration. They say that the slower equilibration is the equivalent of a slower cooling rate, and thus, a lower likelihood for topological defects.

    This research is published in Physical Review Letters

    See the full article here .

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    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments (physics@aps.org).

     
  • richardmitnick 11:55 am on June 11, 2017 Permalink | Reply
    Tags: , Dr. Binghai Yan, , Topological materials, Weizmann Institute of Science   

    From Weizmann: “Physics on the edge” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    1
    Dr. Binghai Yan

    Dr. Binghai Yan is taking topological materials higher.

    Creating new materials for everyday life—think bendable electronics, quantum computers, life-saving medical devices and things we haven’t yet dreamed of—requires understanding and creatively brainstorming new possibilities at the atomic level.

    This is the essence Dr. Binghai Yan’s research. His field is topological materials, which is fusing theoretical science with practical engineering and taking the physics world by storm. And yes, his name gives away the other special news: he is the first principal investigator from China hired by the Weizmann Institute.

    Topological materials and states involve a kind of order very different from conventional bulk materials in that electrons (and their lattices of atoms and molecules) on the surface of a crystal or other material behave differently than those in the material itself. In is the special nature of such topological materials and states that can be leveraged for the creation of new materials. He straddles the world of theory—how such states could work—and experimentation—trying out the materials to synthesize new materials and devices such as quantum computers.

    From rural fields to topology

    So how did a Chinese physicist who grew up in a remote farming village in Shandong Province in eastern China make his way to the Weizmann Institute?

    After completing his BSc at Xi’an Jiatong University in Xi’an in 2003, he earned a PhD in physics at the Tsinghua University in Beijing in 2008. He did postdoctoral research at the University of Bremen in Germany, when the field of topological research was beginning to take off. But it was still a relatively niche subject in which few physicists were working. Thanks to a flexible postdoc grant, the prestigious Humboldt Research Fellowship, which allowed him to spend time at other institutions, he spent eight months at Stanford University learning from a leading expert in the field.

    He returned to Germany to become a group leader (the equivalent of a principal investigator) at the Max Planck Institute for Chemical Physics and Solids in Dresden. It was then that he began collaborating with Weizmann Institute colleagues—thanks to an introduction by Prof. Ady Stern at a conference in Germany—including Prof. Erez Berg and Dr. Haim Beidenkopf, all from the Department of Condensed Matter Physics. The collaboration was enabled by an ARCHES Award given by Germany’s Minerva Foundation, which stimulates collaborative projects by German and Israeli scientists. He visited the Weizmann Institute for the first time in 2013 to advance this work.

    The project and the visit were a “fantastic opportunity,” he says, because his Weizmann collaborators were both theoreticians and experimentalists who were eager to learn about the material he was working on—and Dr. Yan needed feedback from theory to advance his investigations by predicting possible new materials and actualize his ideas in experiments. “I immediately realized that we have lots to do,” he says. “Together, we are able to bridge fundamental physics and experimentation.”

    Last year, he received a competing offer from a university in China, but took the Weizmann offer “because of my existing collaborations and potential collaborations, the depth of theory and experiment work here, and the fact that Weizmann is one of the few places that is advancing this field,” he says.

    Dr. Yan has already discovered a new class of topological materials: a three-dimensional, layered, metallic insulating material which he grows in the lab. He has done so by way of his expertise in electron charge and spin, and so this research has implications for the new, hot field of “spintronics”. Spintronics differs from traditional electronics in that it leverages the way in which electrons spin—not only their charge—to find better efficiency with data storage and transfer. This, in turn, has relevance for the new age of quantum computing, and he hopes to collaborate with quantum computing pioneers at the Institute.

    For his wife, Huanhuan Wang, the decision to make a potentially permanent move to Israel—a country she’d never before visited and about which she had little knowledge—was not as obvious as it was for Dr. Yan. “It took a little bit of convincing my wife to come; if you’ve never been here, all you think is political strife,” says Dr. Yan. “But the reality is different. We are really happy here and it is quickly starting to feel like home.”

    The family arrived in February and moved into campus housing. His wife is now pursuing a PhD under the guidance of Prof. Dan Yakir in the Department of Plant and Environmental Sciences. They have two kids, a boy and a girl, who just began learning German, and now are getting used to Hebrew—and they speak Chinese at home.

    Dr. Yan is finding opportunities to collaborate with scientists in Germany and China, and has already begun organizing a workshop on topological systems at the Weizmann Institute (together with Dr. Haim Beidenkopf and Dr. Nurit Avraham, also of the Department of Physics of Condensed Matter Physics), to which he has invited leading European and Chinese physicists and other leaders in the field.

    “Being in Israel, at Weizmann, is not something that I would have anticipated five or 10 years ago,” he says. “But life—like the materials of the future—holds many mysteries.”

    Dr. Yan is supported by the Ruth and Herman Albert Scholars Program for New Scientists.

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 3:13 pm on May 22, 2017 Permalink | Reply
    Tags: A lack of the protein citrin slows children's growth; blocking it in cancer slows tumor growth., , , Dr. Ayelet Erez, , Weizmann Institute of Science,   

    From Weizmann: Women in STEM – “Rare Genetic Defect May Lead to Cancer Drug” Dr. Ayelet Erez 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    17.05.2017
    No writer credit found

    1
    Dr. Ayelet Erez says rare genetic diseases provide a lens on cancer.

    A lack of the protein citrin slows children’s growth; blocking it in cancer slows tumor growth.

    The path to understanding what goes wrong in cancer could benefit from a detour through studies of rare childhood diseases. Dr. Ayelet Erez explains that cancer generally involves dozens – if not hundreds – of mutations, and sorting out the various functions and malfunctions of each may be nearly impossible. Rare childhood diseases, in contrast, generally involve mutations to a single gene. Erez, a geneticist and medical doctor who treats families with genetic cancer in addition to heading a research lab in the Weizmann Institute of Science’s Biological Regulation Department, says that children with rare genetic syndromes may serve as a “lens” when trying to understand the role of a specific gene in a complex disease such as cancer. She and her team have been focusing their sights on a protein they discovered in this way; promising lab tests indicate that blocking this protein might slow the progression of some cancers.

    Her findings place this research in the new field of “cancer metabolism,” which seeks to understand how the aberrant, or uncontrolled metabolic processes in cancers might turned against them to stop their growth.

    She and her team studied cells from children suffering from an extremely rare disease, citrullinemia type II, who are missing the gene for a protein called citrin. Clinically, children with this disease tend to be smaller than average, and to avoid candy. Her research revealed that this protein normally helps keep the body supplied with an amino acid called aspartate which is required to produce DNA and RNA in addition to the breakdown of glucose; so deficiency in this protein causes the cells to divide less.

    Research into another genetic childhood disease, citrullinemia type I, had already given the team the lens they needed to understand how cancer cells rely on aspartate to divide and migrate. Children born with this disease are missing a gene called ASS1; the lack of ASS1 connects the disease to particularly aggressive, hard-to-treat cancers in which this gene tends to be silenced or mutated. Since this gene also requires aspartate to function, Erez and her team surmised that the silencing had less to do with the gene’s function and more with competition for aspartate and the cancer cells’ craving for ever more of this amino acid to help them divide and spread. Interestingly, the dependence on citrin for aspartate supplementation is seen in cancers both with and without ASS1 expression.

    Ayelet and her team realized that citrin – the protein that helps regulate childhood growth – could present a possible target for anticancer therapies. Blocking this protein would hopefully disrupt the cancer’s overactive metabolic cycle, diminish the cancer cells’ aspartate supply and slow their growth, thus making them less aggressive, less likely to spread and possibly more treatable with other, conventional means. To that end, Erez and her group have been developing a molecule to block citrin, and testing it in the lab. Yeda Research and Development Co., Ltd., the technology transfer arm of the Weizmann Institute of Science, is working with Erez to advance her research to the point that it can be developed for biomedical application.

    Dr. Ayelet Erez’s research is supported by the Moross Integrated Cancer Center; the Irving B. Harris Fund; the Adelis Foundation; the Rising Tide Foundation; the Comisaroff Family Trust; and the European Research Council. Dr. Erez is the incumbent of the Leah Omenn Career Development Chair.

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 11:37 am on March 14, 2017 Permalink | Reply
    Tags: , , , , , Weizmann Institute of Science   

    From Weizmann: “Explosive Material: The Making of a Supernova” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    Pre-supernova stars may show signs of instability for months before the big explosion

    14.03.2017

    In the most common type of supernova, the iron core of a massive star suddenly collapses in on itself and the outer layers are thrown out into space in a spectacular explosion. New research led by Weizmann Institute of Science researchers shows that the stars that become so-called core-collapse supernovae might already exhibit instability for several months before the big event, spewing material into space and creating a dense gas shell around themselves. They think that many massive stars, including the red super-giants that are the most common progenitors of these supernovae, may begin the process this way.

    This insight into the conditions leading up to core collapse arose from a unique collaboration called the Palomar Transient Factory, a fully automated sky survey using the telescopes of the Palomar observatory in southern California.


    Palomar Transient Factory, located in San Diego County, California

    Astrophysicists halfway around the globe, in Israel, are on call for the telescope, which scans the California night sky for the sudden appearance of new astronomical “transients” that were not visible before – which can indicate new supernovae. In October, 2013, Dr. Ofer Yaron, in the Weizmann Institute’s Particle Physics and Astrophysics Department, got the message that a potential supernova had been sighted, and he immediately alerted Dr. Dan Perley who was observing that night with the Keck telescope in Hawaii, and NASA’s Swift Satellite.


    Keck Observatory, Mauna Kea, Hawaii, USA


    NASA/SWIFT Telescope

    At Keck, the researchers soon began to record the spectra of the event. Because they had started observing only three hours into the blast, the picture the team managed to assemble was the most detailed ever of the core collapse process. “We had x-rays, ultraviolet, four spectroscopic measurements from between six and ten hours post-explosion to work with,” says Yaron.

    In the most common type of supernova, the iron core of a massive star suddenly collapses in on itself and the outer layers are thrown out into space in a spectacular explosion. New research led by Weizmann Institute of Science researchers shows that the stars that become so-called core-collapse supernovae might already exhibit instability for several months before the big event, spewing material into space and creating a dense gas shell around themselves. They think that many massive stars, including the red super-giants that are the most common progenitors of these supernovae, may begin the process this way.

    This insight into the conditions leading up to core collapse arose from a unique collaboration called the Palomar Transient Factory, a fully automated sky survey using the telescopes of the Palomar observatory in southern California. Astrophysicists halfway around the globe, in Israel, are on call for the telescope, which scans the California night sky for the sudden appearance of new astronomical “transients” that were not visible before – which can indicate new supernovae. In October, 2013, Dr. Ofer Yaron, in the Weizmann Institute’s Particle Physics and Astrophysics Department, got the message that a potential supernova had been sighted, and he immediately alerted Dr. Dan Perley who was observing that night with the Keck telescope in Hawaii, and NASA’s Swift Satellite. At Keck, the researchers soon began to record the spectra of the event. Because they had started observing only three hours into the blast, the picture the team managed to assemble was the most detailed ever of the core collapse process. “We had x-rays, ultraviolet, four spectroscopic measurements from between six and ten hours post-explosion to work with,” says Yaron.

    In a study recently published in Nature Physics, Yaron, Weizmann Institute researchers Profs. Avishay Gal-Yam and Eran Ofek, and their teams, together with researchers from the California Institute of Technology and other institutes in the United States, Denmark, Sweden, Ireland, Israel and the UK, analyzed the unique dataset they had collected from the very first days of the supernova.

    The time window was crucial: It enabled the team to detect material that had surrounded the star pre- explosion, as it heated up and became ionized and was eventually overtaken by the expanding cloud of stellar matter. Comparing the observed early spectra and light-curve data with existing models, accompanied by later radio observations, led the researchers to conclude that the explosion was preceded by a period of instability lasting for around a year. This instability caused material to be expelled from the surface layers of the star, forming the circumstellar shell of gas that was observed in the data. Because this was found to be a relatively standard type II supernova, the researchers believe that the instability they revealed may be a regular warm up act to the immanent explosion.

    “We still don’t really understand the process by which a star explodes as a supernova,” says Yaron, “These findings are raising new questions, for example, about the final trigger that tips the star from merely unstable to explosive. With our globe-spanning collaboration that enables us to alert various telescopes to train their sights on the event, we are getting closer and closer to understanding what happens in that instant, how massive stars end their life and what leads up to the final explosion.”

    2

    Prof. Avishay Gal-Yam’s research is supported by the Benoziyo Endowment Fund for the Advancement of Science; the Yeda-Sela Center for Basic Research; the Deloro Institute for Advanced Research in Space and Optics; and Paul and Tina Gardner. Prof. Gal-Yam is the recipient of the Helen and Martin Kimmel Award for Innovative Investigation.

    Dr. Eran Ofek’s research is supported by the Helen Kimmel Center for Planetary Science; Paul and Tina Gardner, Austin, TX; Ilan Gluzman, Secaucus, NJ; and the estate of Raymond Lapon.

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 10:11 am on March 1, 2017 Permalink | Reply
    Tags: , , , , , , , , Weizmann Institute of Science   

    From Nautilus: “The Physicist Who Denies that Dark Matter Exists” 

    Nautilus

    Nautilus

    3.1.17
    Oded Carmeli

    1
    Mordehai Milgrom Credit: Weizmann Institute

    Maybe Newtonian physics doesn’t need dark matter to work, but Mordehai Milgrom instead.

    He is one of those dark matter people,” Mordehai Milgrom said about a colleague stopping by his office at the Weizmann Institute of Science. Milgrom introduced us, telling me that his friend is searching for evidence of dark matter in a project taking place just down the hall.

    “There are no ‘dark matter people’ and ‘MOND people,’” his colleague retorted.

    “I am ‘MOND people,’” Milgrom proudly proclaimed, referring to Modified Newtonian Dynamics, his theory that fixes Newtonian physics instead of postulating the existence of dark matter and dark energy—two things that, according to the standard model of cosmology, constitute 95.1% of the total mass-energy content of the universe.

    This friendly incident is indicative of (“Moti”) Milgrom’s calmly quixotic character. There is something almost misleading about the 70-year-old physicist wearing shorts in the hot Israeli summer, whose soft voice breaks whenever he gets excited. Nothing about his pleasant demeanor reveals that this man claims to be the third person to correct Newtonian physics: First Max Planck (with quantum theory), then Einstein (with relativity), now Milgrom.

    This year marks Milgrom’s 50th year at the Weizmann. I visited him there to learn more about how it feels to be a science maverick, what he appreciates about Thomas Kuhn’s The Structure of Scientific Revolutions, and why he thinks dark matter and dark energy don’t exist.

    What inspired you to dedicate your life to the motion of stars?

    I remember very vividly the way physics struck me. I was 16 and I thought: Here is a way to understand how things work, far beyond the understanding of my peers. I was drawn to the beauty of finding deeper reasons for events, to the aesthetics of discovering hidden symmetries. It wasn’t a long-term plan. It was a daily attraction. I simply loved physics, the same way other people love art or sports. I never dreamed of one day making a major discovery, like correcting Newton.

    I had a terrific physics teacher at school, but when you study textbook material, you’re studying done deals. You still don’t see the effort that goes into making breakthrough science, when things are unclear and advances are made intuitively and often go wrong. They don’t teach you that at school. They teach you that science always goes forward: You have a body of knowledge, and then someone discovers something and expands that body of knowledge. But it doesn’t really work that way. The progress of science is never linear.

    How did you get involved with the problem of dark matter?

    Toward the end of my Ph.D., the physics department here wanted to expand. So they asked three top Ph.D. students working on particle physics to choose a new field. We chose astrophysics, and the Weizmann Institute pulled some strings with institutions abroad so they would accept us as postdocs. And so I went to Cornell to fill my gaps in astrophysics.

    After a few years in high energy astrophysics, working on the physics of X-ray radiation in space, I decided to move to yet another field: The dynamics of galaxies. It was a few years after the first detailed measurements of the speed of stars orbiting spiral galaxies came in. And, well, there was a problem with the measurements.

    To understand this problem, one needs to wrap one’s head around some celestial rotations. Our planet orbits the sun, which, in turn, orbits the center of the Milky Way galaxy. Inside solar systems, the gravitational pull from the mass of the sun and the speed of the planets are in balance. By Newton’s laws, this is why Mercury, the innermost planet in our solar system, orbits the sun at over 100,000 miles per hour, while the outermost plant, Neptune, is crawling at just over 10,000 miles per hour.

    Now, you might assume that the same logic would apply to galaxies: The farther away the star is from the galaxy’s center, the slower it revolves around it; however, while at smaller radiuses the measurements were as predicted by Newtonian physics, farther stars proved to move much faster than predicted from the gravitational pull of the mass we see in these galaxies. The observed gap got a lot wider when, in the late 1970s, radio telescopes were able to detect and measure the cold gas clouds at the outskirts of galaxies. These clouds orbit the galactic center five times farther than the stars, and thus the anomaly grew to become a major scientific puzzle.

    One way to solve this puzzle is to simply add more matter. If there is too little visible mass at the center of galaxies to account for the speed of stars and gas, perhaps there is more matter than meets the eye, matter that we cannot see, dark matter.

    2
    MOND in the MakingMilgrom’s notes from 1981. On the left, each line represents the data from a separate galaxy. On the right is the MOND prediction, which is the line going through the data points.
    Mordehai Milgrom

    What made you first question the very existence of dark matter?

    What struck me was some regularity in the anomaly. The rotational velocities were not just larger than expected, they became constant with radius. Why? Sure, if there was dark matter, the speed of stars would be greater, but the rotation curves, meaning the rotational speed drawn as a function of the radius, could still go up and down depending on its distribution. But they didn’t. That really struck me as odd. So, in 1980, I went on my Sabbatical in the Institute for Advance Studies in Princeton with the following hunch: If the rotational speeds are constant, then perhaps we’re looking at a new law of nature. If Newtonian physics can’t predict the fixed curves, perhaps we should fix Newton, instead of making up a whole new class of matter just to fit our measurements.

    If you’re going to change the laws of nature that work so well in our own solar system, you need to find a property that differentiates solar systems from galaxies. So I made up a chart of different properties, such as size, mass, speed of rotation, etc. For each parameter, I put in the Earth, the solar system and some galaxies. For example, galaxies are bigger than solar systems, so perhaps Newton’s laws don’t work over large distances? But if this was the case, you would expect the rotation anomaly to grow bigger in bigger galaxies, while, in fact, it is not. So I crossed that one out and moved on to the next properties.

    I finally struck gold with acceleration: The pace at which the velocity of objects changes.

    We usually think of earthbound cars that accelerate in the same direction, but imagine a merry-go-round. You could be going in circles and still accelerate. Otherwise, you would simply fall off. The same goes for celestial merry-go-rounds. And it’s in acceleration that we find a big difference in scales, one that justifies modifying Newton: The normal acceleration for a star orbiting the center of a galaxy is about a hundred million times smaller than that of the Earth orbiting the sun.

    For those small accelerations, MOND introduces a new constant of nature, called a0. If you studied physics in high school, you probably remember Newton’s second law: force equals mass times acceleration, or F=ma. While this is a perfectly good tool when dealing with accelerations much greater than a0, such as those of the planets around our sun, I suggested that at significantly lower accelerations, lower even than that of our sun around the galactic center, force becomes proportional to the square of the acceleration, or F=ma2/a0.

    To put it in other words: According to Newton’s laws, the rotation speed of stars around galactic centers should decrease the farther the star is from the center of mass. If MOND is correct, it should reach a constant value, thus eliminating the need for dark matter.

    What did your colleagues at Princeton think about all this?

    I didn’t share these thoughts with my colleagues at Princeton. I was afraid to come across as, well, crazy. And then, in 1981, when I already had a clear idea of MOND, I didn’t want anyone to jump on my wagon, so to speak, which is even crazier when you think about it. Needless to say,” he laughs, “no one jumped on my wagon, even when I desperately wanted them to.

    Well, you were 35 and you proposed to fix Newton.

    Why not? What’s the big deal? If something doesn’t work, fix it. I wasn’t trying to be bold. I was very naïve at the time. I didn’t understand that scientists are just as swayed as other people by conventions and interests.

    Like Thomas Kuhn’s The Structure of Scientific Revolutions.

    I love that book. I read it several times. It showed me how my life’s story has happened to so many others scientists throughout history. Sure, it’s easy to make fun of people who once objected to what we now know is good science, but are we any different? Kuhn stresses that these objectors are usually good scientists with good reasons to object. It is just that the dissenters usually have a unique point of view of things that is not shared by most others. I laugh about it now, because MOND has made such progress, but there were times when I felt depressed and isolated.

    What’s it like being a science maverick?

    By and large, the last 35 years have been exciting and rewarding exactly because I have been advocating a maverick paradigm. I am a loner by nature, and despite the daunting and doubting times, I much prefer this to being carried with the general flow. I was quite confident in the basic validity of MOND from the very start, which helped me a lot in taking all this in stride, but there are two great advantages to the lingering opposition to MOND: Firstly, it gave me time to make more contributions to MOND than I would had the community jumped on the MOND wagon early on. Secondly, once MOND is accepted, the long and wide resistance to it will only have proven how nontrivial an idea it is.

    By the end of my sabbatical in Princeton, I had secretly written three papers introducing MOND to the world. Publishing them, however, was a whole different story. At first I sent my kernel paper to journals such as Nature and Astrophysical Journal Letters, and it got rejected almost off-hand. It took a long time until all three papers were published, side by side, in Astrophysical Journal.

    The first person to hear about MOND was my wife Yvonne. Frankly, tears come to my eyes when I say this. Yvonne is not a scientist, but she has been my greatest supporter.

    The first scientist to back MOND was another physics maverick: The late Professor Jacob Bekenstein, who was the first to suggest that black holes should have a well-defined entropy, later dubbed the Bekenstein-Hawking entropy. After I submitted the initial MOND trilogy, I sent the preprints to several astrophysicists, but Jacob was the first scientist I discussed MOND with. He was enthusiastic and encouraging from the very start.

    Slowly but surely, this tiny opposition to dark matter grew from just two physicists to several hundred proponents, or at least scientists who take MOND seriously. Dark matter is still the scientific consensus, but MOND is now a formidable opponent that proclaims the emperor has no clothes, that dark matter is our generation’s ether.

    So what happened? As far as dark matter is concerned, nothing really. A host of experiments searching for dark matter, including the Large Hadron Collider, many underground experiments and several space missions, have failed to directly observe its very existence. Meanwhile, MOND was able to accurately predict the rotation of more and more spiral galaxies—over 150 galaxies to date, to be precise.

    All of them? Some papers claim that MOND wasn’t able to predict the dynamics of certain galaxies.

    That’s true and it’s perfectly fine, because MOND’s predictions are based on measurements. Given the distribution of regular, visible matter alone, MOND can predict the dynamics of galaxies. But that prediction is based on our initial measurements. We measure the light coming in from a galaxy to calculate its mass, but we often don’t know the distance to that galaxy for sure, so we don’t know for certain just how massive that galaxy really is. And there are other variables, such as molecular gas, that we can’t observe at all. So yes, some galaxies don’t perfectly match MOND’s predictions, but all in all, it’s almost a miracle that we have enough data on galaxies to prove MOND right, over and over again.

    Your opponents say MOND’s greatest flaw is its incompatibility with relativistic physics.

    In 2004, Bekenstein proposed his TeVeS, or Relativistic Gravitational Theory for MOND. Since then, several different relativistic MOND formulations have been put forth, including one by me, called Bimetric MOND, or BIMOND.

    So, no, incorporating MOND into Einsteinian physics is no longer a challenge. I hear this statement still made, but only from people who parrot others, who themselves are not abreast with the developments of the last 10 years. There are several relativistic versions of MOND. What remains a challenge is demonstrating that MOND can account for the mass anomalies in cosmology.

    Another argument that cosmologists often make is that dark matter is needed not just for motion within galaxies, but on even larger scales. What does MOND have to say about that?

    According to the Big Bang theory, the universe began as a uniform singularity 13.8 billion years ago. And, just as in galaxies, observations made of the cosmic background radiation from the early universe suggest that the gravity of all the matter in the universe is simply not enough to form the different patterns we currently see, like galaxies and stars, in just 13.8 billion years. Once again, dark matter was called to the rescue: It does not emit radiation, but it does engage visible material with gravitation. And so, starting from the 1980s, the new cosmological dogma was that dark matter constituted a staggering 95 percent of all matter in the universe. That lasted, well, right until the bomb hit us in 1998.

    It turned out that the expansion of the universe is accelerating, not decelerating like all of us originally thought. Any form of genuine matter, dark or not, should have slowed down acceleration. And so a whole new type of entity was invented: Dark energy. Now the accepted cosmology is that the universe is made up of 70 percent dark energy, 25 percent dark matter, and 5 percent regular matter.

    But dark energy is just a quick fix, the same as dark matter is. And just as in galaxies, you can either invent a whole new type of energy and then spend years trying to understand its properties, or you can try fixing your theory.

    Among other things, MOND points to a very deep connection between structure and dynamics in galaxies and cosmology. This is not expected in accepted physics. Galaxies are tiny structures within the grand scale of the universe, and those structures can behave differently without contradicting the current cosmological consensus. However, MOND creates this connection, binding the two.

    This connection is surprising: For whatever reason, the MOND constant of a0 is close to the acceleration that characterizes the Universe itself. In fact, MOND’s constant equals the speed of light squared, divided by the radius of universe.

    So, indeed, to your question, the conundrum pointed to is valid at present. MOND doesn’t have a sufficient cosmology yet, but we’re working on it. And once we fully understand MOND, I believe we’ll also fully understand the expansion of the universe, and vice versa: A new cosmological theory would explain MOND. Wouldn’t that be amazing?

    What do you think about the proposed unified theories of physics, which merge MOND with quantum mechanics?

    These all hark back to my 1999 paper on ‘MOND as a vacuum effect’, where it was pointed out that the quantum vacuum in a universe such as ours may produce MOND behavior within galaxies, with the cosmological constant appearing in the guise of the MOND acceleration constant, a0. But I am greatly gratified to see these propositions put forth, especially because they are made by people outside the traditional MOND community. It is very important that researchers from other backgrounds become interested in MOND and bring new ideas to further our understanding of its origin.

    And what if you had a unified theory of physics that explains everything? What then?

    You know, I’m not a religious person, but I often think about our tiny blue dot, and the painstaking work we physicists do here. Who knows? Perhaps somewhere out there, in one of those galaxies I spent my life researching, there already is a known unified theory of physics, with a variation of MOND built into it. But then I think: So what? We still had fun doing the math. We still had the thrill of trying to wrap our heads around the universe, even if the universe never noticed it at all.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
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