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  • richardmitnick 10:16 am on September 14, 2018 Permalink | Reply
    Tags: , , , , Dark Energy, , Dark matter clusters could reveal nature of dark energy,   

    From Horizon The EU Research and Innovation Magazine: “Dark matter clusters could reveal nature of dark energy” 


    From Horizon The EU Research and Innovation Magazine

    10 September 2018
    Jon Cartwright

    Gravitational lensing in galaxy clusters such as Abell 370 are helping scientists to measure the dark matter distribution. Image credit – NASA, ESA, the Hubble SM4 ERO Team and ST-ECF

    Scientists are hoping to understand one of the most enduring mysteries in cosmology by simulating its effect on the clustering of galaxies.

    That mystery is dark energy – the phenomenon that scientists hypothesise is causing the universe to expand at an ever-faster rate. No-one knows anything about dark energy, except that it could be, somehow, blowing pretty much everything apart.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Meanwhile, dark energy has an equally shady cousin – dark matter.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington

    This invisible substance appears to have been clustering around galaxies, and preventing them from spinning themselves apart, by lending them an extra gravitational pull.

    Such a clustering effect is in competition with dark energy’s accelerating expansion. Yet studying the precise nature of this competition might shed some light on dark energy.

    ‘Many dark energy models are already ruled out with current data,’ said Dr Alexander Mead, a cosmologist at the University of British Columbia in Vancouver, Canada, who is working on a project called Halo modelling. ‘Hopefully in future we can rule more out.’

    Gravitational lensing

    Currently, the only way dark matter can be observed is by looking for the effects of its gravitational pull on other matter and light. The intense gravitational field it produces can cause light to distort and bend over large distances – an effect known as gravitational lensing.

    By mapping the dark matter ​in distant parts of the cosmos, scientists can work out how much dark matter clustering there is – and in principle how that clustering is being affected by dark energy.

    The link between gravitational lensing and dark matter clustering is not straightforward, however. To interpret the data from telescopes, scientists must refer to detailed cosmological models – mathematical representations of complex systems.

    Dr Mead is developing a clustering model that he hopes will have enough accuracy to distinguish between different dark-energy hypotheses.

    ‘An analogy I like a lot is with turbulence. In turbulent fluid flow you can talk about currents and eddies, which are nice words, but the reality of how fluid in a pipe goes from flowing calmly to flowing in a turbulent fashion is extremely complicated.’


    ‘If dark energy turns out to be a dynamical phenomenon this will have a profound implication not only on cosmology, but on our understanding of fundamental physics.’

    Dr Pier Stefano Corasaniti, Paris Observatory, France

    Fifth force

    One of the more exotic theories is that dark energy is the result of a hitherto undetected fifth force, in addition to nature’s four known forces – gravity, electromagnetism, and the strong and weak nuclear forces inside atoms.

    A more common hypothesis for dark energy, however, is known as the cosmological constant, which was put forward by Albert Einstein as part of his general theory of relativity. It is often believed to describe an all-pervading sea of virtual particles that are continually popping into and out of existence throughout the universe.

    One way to rule out the cosmological constant hypothesis, of course, is to prove that dark energy is not constant at all. This is the goal of Dr Pier Stefano Corasaniti of the Paris Observatory in France, who – in a project called EDECS – is approaching dark-matter clustering from a different direction.

    Instead of attempting to model clustering from gravitational lensing data, he is beginning specifically with a dynamical – that is, not constant – hypothesis of dark energy, and trying to predict how dark matter would cluster if this was the case.

    Pushing the limits

    There are, in principle, infinite ways dark energy can vary in space and time, although many theories have already been ruled out by existing observations. Dr Corasaniti is focussing his simulations on types of dynamical dark energy that push at the edges of these observational limits, paving the way for tests with future experiments.

    The simulations, which trace the evolution of numerous, ‘N-body’ dark matter particles, require supercomputers running for long periods of time, processing several petabytes (one thousand million million bytes) of data.

    ‘We have run among the largest cosmological N-body simulations ever realised,’ Dr Corasaniti said.

    Dr Corasaniti’s simulations predict that the way dark energy evolves over time ought to affect dark matter clustering. This, in turn, alters the efficiency with which galaxies form in ways that would not be the case with constant dark energy.

    The predictions his models are making could be tested with the help of forthcoming telescopes such as the Large Synoptic Survey Telescope in Chile and the Square Kilometre Array in Australia and South Africa, as well as by satellite missions such as Euclid (EUropean Cooperation for LIghtning Detection) and WFIRST (Wide Field Infrared Survey Telescope).


    LSST Camera, built at SLAC

    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    SKA Square Kilometer Array

    SKA South Africa

    ESA/Euclid spacecraft


    ‘If dark energy turns out to be a dynamical phenomenon this will have a profound implication not only on cosmology, but on our understanding of fundamental physics,’ said Dr Corasaniti.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 12:21 pm on September 13, 2018 Permalink | Reply
    Tags: , Dark Energy, Lambda leads the way, , , , The Cosmic Landscape   

    From Stanford University: “Lambda leads the way” 

    Stanford University Name
    From Stanford University

    September 13, 2018
    Ker Than

    Most physicists think that dark energy, the cosmological constant, and lambda all refer to a repulsive energy infused in empty space itself. (Image credit: Eric Nyquist)

    The discovery of dark energy in the 1990s marked a time of reckoning for string theorists: Either their theory had to account for the newfound force that was pushing space-time apart or they had to admit that string theory may never describe the universe we actually live in. This story is part 4 of a five-part series.

    In 1998, astronomers hunting halfway across the universe for the ebbing light of exploded stars announced they had discovered evidence that the universe’s expansion is speeding up and not, as had been suspected since 1929, slowing down.

    The realization came as “a thunderbolt to physicists, something so shocking that we are still reeling from the impact,” Leonard Susskind wrote in his book The Cosmic Landscape.

    Leonard Susskind by Linda Cicero-Stanford News Service

    “Physicists everywhere were asking, ‘Is the experiment wrong?’” Renata Kallosh recalled.

    But with every passing year, new experiments confirmed the results: Expansion is accelerating, not slowing down. For those results to be true, an elusive force that physicists had come to refer to as “dark energy” must be real.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Einstein had predicted the existence of dark energy in 1917 when he applied his general theory of relativity to the structure of space-time. He needed a hypothetical force to prevent the universe from collapsing, so he invented a repulsive, space-filling energy that he called the cosmological constant, or lambda. When astronomers discovered in the 1920s that the universe is expanding, Einstein realized that lambda was no longer necessary and he scrapped the idea, calling it his “biggest blunder.”

    But Einstein may have been too hard on himself. Today, most physicists think that dark energy, the cosmological constant and lambda all refer to a repulsive energy infused in empty space itself. Quantum mechanics predicts that the spontaneous creation and annihilation of ghostly “virtual particles” generates an anti-gravitational force whose influence grows with the age and size of the universe.

    When astronomers were able to measure lambda experimentally, they found it had a positive but bewilderingly tiny value that was about a trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion times weaker than theory predicted. The Nobel Prize-winning physicist Steven Weinberg called this humiliating mismatch between observation and theory “the bone in our throat.”

    Equally perplexing, lambda’s tiny value lay just within the narrow range able to support life. If it were much larger, the universe would expand too quickly for galaxies and stars to form; much smaller, and creation would collapse back into a point.

    “Theoretical physics was upside down because of this experimental discovery,” Kallosh said. “We had no explanation whatsoever.”

    The cosmological constant problem

    The first tentative steps toward resolving what came to be known as the “cosmological constant problem” were taken in 2000 by theorists Joseph Polchinski of the University of California, Santa Barbara, and Raphael Bousso, a Stanford postdoc and a former student of Stephen Hawking. The pair published a paper showing that string theory could give rise to an enormous number of unique vacuum states – vastly more than previously thought. “The vacuum state is what remains if you remove all of the particles from the universe,” Andrei Linde explained. “The properties of a vacuum determine what its particles will look like and what the physics of their interactions will be if it were populated.”

    “Theoretical physics was upside down because of this experimental discovery. We had no explanation whatsoever.”
    —Renata Kallosh
    Professor of Physics

    Each vacuum described, in essence, a potential universe with its own singular take on particles and forces. “It was already known that string theory had lots of solutions,” Susskind said, “but their paper showed that it could have a vast number, and among them could be solutions that had these rare traits like a very low cosmological constant.”

    But despite offering tantalizing hints of string theory universes that could accommodate dark energy, Polchinski and Bousso, who is now at the University of California, Berkeley, stopped short of actually finding one. “They had a correct but imprecise collection of arguments for this diversity,” Susskind said. “They had no real examples of it.”

    In search of de Sitter

    The first reasonably concrete example was discovered by theoretical physicist Eva Silverstein, a professor at the Stanford Institute for Theoretical Physics who was motivated by dark energy’s discovery to search for a mechanism that could create a so-called “de Sitter” solution to string theory. De Sitter solutions (named after the Dutch astronomer Willem de Sitter) represent expanding universes with a positive cosmological constant similar to our own. Silverstein wanted to know if a solution existed in string theory that was compatible with the universe that astronomers actually observe. If none could be found, then string theorists had been wasting their time building castles in the air.

    Up to that point, string theorists had focused on solutions for universes with a negative lambda called anti-de Sitter space-time. “De Sitter solutions are more complex, and until the discovery of dark energy, no one bothered,” Silverstein said. “Some even argued that de Sitter solutions weren’t possible in string theory, and it remains a complicated subject. But these ‘no go’ arguments did not consider the leading contributions to the potential energy in string theory.”

    In 2001, Silverstein published a paper in which she proposed a mechanism for combining various ingredients from string theory – extra dimensions, orientifolds, fluxes and so on – in specific ways to create a de Sitter model. She also predicted that any de Sitter solutions would need to contain certain features. She argued, for example, that the path to positive lambda was indirect and would require making a negative contribution first. “One thing I pointed out early on is that negative contributions to the potential energy, in the right place to produce a local dip in it, would be needed,” Silverstein said, “and that this role could be played by orientifolds, which are defects in string theory’s extra dimensions that have a controlled amount of negative energy.”

    Shamit Kachru, Renata Kallosh and Andrei Linde are three of the four authors of an influential paper that came to be known as KKLT. The paper helped lay the groundwork for the String Theory Landscape. (Image credit: L.A. Cicero)


    Early in 2003, Kallosh and Linde received an email from Shamit Kachru, who had been visiting the string theorist Sandip Trivedi in India. The quartet of physicists was engaged in a long-distance brainstorming session and Kachru’s message contained the kernel of an idea that had come to him during a flight layover in New Delhi.

    When Kallosh plotted data that Kachru had sent, up popped on her computer a chart with the same potential energy dip that Silverstein had predicted. However, this dip had been generated using different string theory ingredients and assumptions. “I knew we were onto something then,” Kallosh said.

    Later that year, the four of them published their results in a famous paper that would come to be known simply as KKLT (after the authors’ last initials). KKLT described a class of de Sitter solutions that incorporated a certain symmetry, called supersymmetry, that many physicists were expecting to see confirmed in particle collider experiments.

    “KKLT was a very important paper,” said particle physicist Savas Dimopoulos, the Hamamoto Family Professor in the School of Humanities and Sciences. “We don’t see supersymmetric particles in nature, so if symmetry did exist in the early universe, it’s been broken. What KKLT did was point out a breaking mechanism.”

    KKLT was also important for psychological reasons. “It was written by members from different parts of the physics community,” Kachru said. “Renata was a supergravity person, Andrei was an inflation person, and Sandip and I were more mathematical string theorists. All of us were saying that this kind of solution of string theory, which allows accelerated expansion due to dark energy, is something to take seriously.”

    For these reason, KKLT’s mathematical model, or “construction,” grabbed physicists’ attention in a way that earlier ones had not. Among those affected were Michael Douglas and Frederik Denef, both at Rutgers University at the time, who used the KKLT construction to famously calculate that there might exist as many as 10500 unique “vacua,” or possible universes, with a small cosmological constant. (For perspective, the total number of particles in the observable universe is estimated to be about 1090.)

    Around the same time, Susskind published a paper of his own expanding upon his colleagues’ findings. “I was more of a cheerleader than anything else,” Susskind said. “My paper was really just saying, ‘Hey guys, are you paying attention to this? This is happening.’”

    Susskind is also credited with naming the emerging concept within string theory of countless hypothetical universes with varying properties: He called it the “anthropic Landscape of string theory,” or the “String Theory Landscape” for short. “The Landscape doesn’t refer to a real place,” Susskind said. “It’s a scientific term borrowed from biology and physics that refers to an energy landscape with lots of hills and valleys. In string theory, the Landscape is incredibly rich, and our universe lies in one of the rare, habitable, low-lying valleys.”


    “In string theory, the Landscape is incredibly rich, and our universe lies in one of the rare, habitable, low-lying valleys.”
    —Leonard Susskind, Professor of Physics

    Susskind also reminded his fellow physicists that they already knew of a mechanism that could generate the tremendous diversity of universes predicted by string theory. This “natural candidate” had been pointed out by Bousso and Polchinski years earlier.

    Recalling his collaboration with Bousso in 2000, Polchinski, who died in February 2018, wrote in his memoir: “But when Bousso came back a few months later … he had added an important part of the story, the cosmology that allowed the theory to explore all these states. It was just Linde’s eternal chaotic inflation. … I had always assumed that such a thing would not be part of string theory, but in fact it arose quite naturally.”

    A Rube Goldberg construction

    If the measure of a theory’s beauty is the ratio of how many things it explains to how many assumptions it makes to explain them, then the constructions by Silverstein and KKLT are not pretty. Their authors rummaged through string theory’s pantry for exotic ingredients and combined them in wildly creative ways to concoct their imaginary universes. The KKLT construction in particular, Susskind said, was made up of “jury-rigged, Rube Goldberg contraptions” – a reference to the American inventor famous for his cartoon sketches of gadgets that performed simple tasks in convoluted ways.

    But the contrived nature of the de Sitter constructions mattered less to theorists than the fact that they existed at all. In a theory where infinite solutions are possible, Susskind argued, “simplicity and elegance are not considerations.” In all their long years of searching, KKLT and its kin were the clearest signs physicists had ever found that string theory could produce universes roughly resembling our own. The constructions the Stanford theorists produced gave powerful support to physicists’ hope that a mathematical version of our cosmos lay hidden somewhere within string theory’s labyrinthine equations and infinite solutions, and that – with ingenuity, luck and perhaps a late-night revelation or two – it might one day be found.

    See the full article here .

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    Stanford University campus. No image credit

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 8:15 am on September 5, 2018 Permalink | Reply
    Tags: A Type IV civilization would be undetectable to us, A Type V master race that would function like gods able to harness energy not only from this universe but all universes in all dimensions, , At 100000 times the energy usage we have now we’d have access to 10¹⁷ watts of energy as a Type I civilization, , , Dark Energy, Dyson ring and Dyson bubble, , Micro-scale developed by John D. Barrow, , Physicist Michio Kaku, The Kardashev scale designed by astrophysicist Nikolai Kardashev, The trick for a galactic species would be the constraints of the laws of physics, These feats are very sci-fi and as far as we know impossible to accomplish. But then again we’re a lowly Type 0 civilization with no idea what may lie ahead, To colonize all the stars we could use self-replicating robots that would assemble and maintain the Dyson swarms, We’re a Type Zero Civilization   

    From Medium: “We’re a Type Zero Civilization” 

    From Medium

    Aug 11, 2018
    Updated 9.5.18
    Ella Alderson

    When will we move up the scale?

    Image: Juanmrgt/iStock/Getty Images Plus

    The Kardashev scale, designed by astrophysicist Nikolai Kardashev, was created to assess how advanced a civilization is by taking into consideration multiple factors, including population growth, technology, and energy demands. The idea is that the more advanced the people are, the higher and more complex their energy usage will be. When we first appeared on Earth 200,000 years ago, for example, our species was few in number, and the extent of our energy source was, really, just fire. We now number in the billions and use a combination of wind, solar, and nuclear energy sources, though our main energy supply comes from fossil fuels (it really seems like we just moved on to burning bigger and badder things). The International Energy Agency estimates that each year our societies use an estimated 17.37 terrawatt-hours.

    All of this may sound fairly advanced — we’ve come a long way from just using logs to fuel our everyday lives. Yet in reality, we’re really quite primitive compared to where we could be. We still get the majority of our energy from dead plants and animals, a source that will eventually run out sooner or later, and which is helping destroy our planet in the process.

    So where do we place on the Kardashev scale? We’re a zero: 0.72, to be more exact. Here’s what we need to move forward.

    Type I

    To become a Type I civilization we would have to harness all the available energy of our home planet at 100% efficiency. This means capturing the energy of every wave, every beam of sunlight, and every bit of fossil fuel we can dig up. To do that without rendering the entire planet uninhabitable, we’d have to use nuclear fusion. And to create all the energy we need via this method, we would require 280 k/s of hydrogen and helium every second, or 89 billion grams of hydrogen per year. You can gather more than that from one square km of ocean water.

    With this ability to harness all energy from Earth also comes the ability to control all of the planet’s natural forces, including volcanoes, geothermal vents, earthquakes, and climate. At 100,000 times the energy usage we have now, we’d have access to 10¹⁷ watts of energy as a Type I civilization. Consider, for example, the ability to control a hurricane. One such storm can release the power of hundreds of hydrogen bombs.

    While controlling the weather may sound very fantastical, physicist Michio Kaku theorizes that we’ll reach Type I status in the next 100–200 years, as we continue to grow in population at about 3% per year.

    Dyson ring concept drawing (Source: Vedexent/Wikipedia)
    Dyson bubble concept drawing (Source: PNG Crusade Bot/Wikipedia)/CC BY 2.5

    After we’ve been able to harness all the energy from our home planet, we’ll move on to harnessing all the energy of our home star, the sun. One way of doing this is to build a Dyson swarm around the star, or a group of panels capable of reflecting light into small solar power plants which could then send those light beams to Earth for our use. Similar to the work of controlling the forces here on Earth, we’d be able to control the star as well, including the manipulation of solar flares. Another way to get enough energy for a Type II civilization would be to build a fusion reactor on a huge scale or to use a reactor to essentially drain the hydrogen from a nearby gas giant, like Jupiter.

    At this point we’re a few thousand years into the future and using 10²⁶ watts of energy. A stellar civilization capable of gathering energy on this scale has become immune to extinction.

    Type III

    We’ve gone from controlling all the energy of our home planet to our home star and, now, our galaxy. Take the Dyson swarm proposed above and extend it to cover all 100 billion stars of the Milky Way. A civilization this advanced, and with access to this many resources, would truly be a master race, having at their disposal 10³⁶ watts of energy. Hundreds of thousands, even millions of years of evolution would mean that we as a race would look very different, both biologically and in terms of merging with our technology in becoming cyborgs or even fully robotic.

    To colonize all the stars we could use self-replicating robots that would assemble and maintain the Dyson swarms, though it’s likely we’ll have found a new energy source by then. This could include tapping into the energy of the black hole at the center of the Milky Way, or even using gamma ray bursts. Another possibility, though they have been yet undetected, would be to find a white hole and to use the energy that emanates from it.

    The trick for a galactic species would be the constraints of the laws of physics — how can they be united when their colonies are light years away? They’d have to find a way to move at the speed of light or, even better, create wormholes to other locations.

    Kardashev ended the scale here because he didn’t believe it could go any further, stating that any civilizations beyond Type III would be too advanced to even fathom. But other astronomers have since extended the scale to include Type IV and Type V.

    Type IV and V

    A Type IV civilization would be undetectable to us. It would be able to harness the entire energy of the universe and move across all of space, appearing as nothing more than a work of nature. Some speculate that giant voids in space, like the one 1.8 billion light years across and missing 90% of its galaxies, could be proof of a civilization making use of the universe. But a civilization this advanced might not even harness energy as we know it anymore, choosing instead to move into more exotic substances, like dark energy. They might also live inside black holes, controlling 10⁴⁶ watts of energy. These feats are very sci-fi and, as far as we know, impossible to accomplish. But then again we’re a lowly Type 0 civilization with no idea what may lie ahead.

    It gets even more fantastical when one considers a Type V master race that would function like gods, able to harness energy not only from this universe, but all universes in all dimensions. Its energy usage and access to knowledge would be incomprehensible.


    The micro-dimensional mastery extension to the Kardashev scale was proposed by John D. Barrow, a scientist who decided to take civilization ranking in the opposite direction, choosing instead to base his scale on how small a people’s control could reach. This scale is outlined differently:

    Type I-minus: controlling matter at the observable level, that is, being to manipulate things we can see and touch.

    Type II-minus: controlling genes

    Type III-minus: controlling molecules

    Type IV-minus: controlling atoms

    Type V-minus: controlling protons

    Type VI-minus: controlling elementary particles, like quarks

    Type Omega-minus: controlling fundamental elements of spacetime

    Whether using the original or micro version, the beautiful thing about the Kardashev scale is that it’s not just full of fascinating and alien concepts; it’s also a blueprint for where we could go if our species could just make it the next 100 years. Will the human race emerge from our planet and thrive in the universe just as we emerged from Africa and grew to thrive around the world?

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 5:17 pm on August 20, 2018 Permalink | Reply
    Tags: , , , , , Dark Energy, , , , , The scientific theories battling to explain the universe   

    From CNN: “The scientific theories battling to explain the universe” 

    From CNN

    August 17, 2018
    FNAL’s Don Lincoln

    In human history, there have been many interesting and epic feuds — the Hatfields and McCoys, Bette Davis and Joan Crawford, or the Notorious B.I.G and Tupac. Many of us love to read in tabloids or history books about the salacious details of how the bad blood came to be.

    Just like these human characters, scientific theories can also fall into disagreement, causing just as much drama in the science world.

    Recently, a group of scientists claimed to have found a fatal tension between two of the scientific community’s most mind-blowing theories: superstrings and dark energy. If the authors are correct, one of the two theories is in trouble.

    Superstring theory is a candidate theory of everything, with the operative word being “candidate,” meaning it is not yet accepted by the scientific community. It tries to explain all observed phenomena of the universe with a single principle. At its core, it predicts that the smallest building blocks of the cosmos aren’t the familiar atoms and protons, neutrons, and electrons; nor are the smallest building blocks the even-smaller quarks and lepton that my colleagues and I have discovered. Instead, superstring theory suggests that the very smallest building blocks of all are tiny and vibrating “strings.”

    These strings can vibrate in different ways — essentially different notes — with each note looking like one of the known subatomic particles. Waxing slightly poetic, superstring theory explains the universe as a vast and cosmic symphony.

    The other popular theory, called dark energy, is quite different. Astronomers have long known that the universe is expanding. For decades, we thought we understood that, because gravity is an attractive force, this expansion would slow over the lifetime of the universe. It was therefore a surprise when, in 1998, astronomers discovered that not only was the expansion of the universe not slowing down — it was speeding up.

    To explain this observation, astronomers added a type of energy — called dark energy — to Einstein’s equations describing the behavior of gravity. Dark energy is an energy field that permeates the entire universe. And, because the expansion of the universe is accelerating, dark energy must exist and it must be positive. The reason we know that is simple. If the dark energy didn’t exist or was negative, the expansion of the universe would be slowing down.

    So, what is it about these two theories that has caused such a conflict?

    In a nutshell, it’s hard to make a superstring theory with positive energy and yet the accelerating expansion of the universe demands it. If one theory is completely accurate it means that a key aspect of the other is wrong. And, on the face of it, things look bad for superstring theory. This is because while dark energy is still a theory, the accelerating expansion of the universe is not. Thus, dark energy is probably true, while superstring theory still remains only a conjecture.

    But there’s a reason that scientists aren’t rushing to media platforms to spread the news that superstring theory has been disproved.

    It’s because superstring theory is fiendishly complex. Aside from the prediction of subatomic vibrating strings, it also predicts that there are more dimensions of space than our familiar three. In fact, the theory predicts that there are nine in total — 10 if you include time. You’d think that this would be a fatal flaw of the theory, but these additional dimensions are thought to be invisibly small.

    Since these extra dimensions (if they exist) are smaller than our best instrumentation can detect, we don’t know what their shapes are, and scientists must consider all possibilities. But there are a lot of possibilities. In fact, there are more configurations than there are atoms in a million universes just like ours. It’s a crazy big number.

    So, what conclusion can we draw?

    With so many possible configurations, it would seem that superstring theory could predict just about anything, yet the scientists who pointed out the theories’ disagreement are making the bold claim that none of these configurations result in the existence of a positive and constant energy (aka, the theory of dark energy).

    And all the data recorded so far have made scientists feel relatively confident that dark energy not only exists, but is also both positive and nearly constant, making it seem likely that, if only one of these theories can be true, it’s dark energy for the win. Still, it’s premature to make any conclusions about the superstrings. It’s possible that scientists are not right about the nature of dark energy and they are using powerful instruments like the Dark Energy Survey to refine their measurements.

    The bottom line is that physicists are going to have to take this new idea seriously. It’s not quite a WWE cage match, but it’s going to be fun to watch these theories fight it out.

    See the full article here .


    Please help promote STEM in your local schools.

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  • richardmitnick 9:20 am on August 14, 2018 Permalink | Reply
    Tags: , , , , Dark Energy, DECam at the Blanco telescope, , ,   

    From Fermi National Accelerator Lab: “Mapping the universe in 3-D: Fermilab contributes to the Dark Energy Spectroscopic Instrument” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    August 13, 2018
    Jordan Rice

    In 1998, scientists discovered that the universe’s expansion is accelerating. Physicists don’t know how or why the universe is accelerating outward, but they gave the mysterious force behind this phenomenon a name: dark energy.

    Scientists know a great deal about the effects of dark energy, but they don’t know what it is. Cosmologists approximate that 68 percent of the universe’s total energy must be made of the stuff. One way to get a better handle on dark energy and its effects is to create detailed maps of the universe, plotting its expansion. Scientists, engineers and technicians are currently building the Dark Energy Spectroscopic Instrument, or DESI, to do just that.

    DESI will help create the largest 3-D map of galaxies to date, one that will span a third of the entire sky, stretch back 11 billion light-years, and record approximately 35 million galaxies and quasars.

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    It will measure the spectra of light emanating from galaxies to determine their distances from Earth. Other surveys have created maps that locate galaxies’ lateral positions in the sky, but scientists using DESI will be able to take more precise measurements of their distance from us, creating high-resolution, 3-D maps.

    DESI is currently being installed at the Mayall 4-Meter Telescope at Kitt Peak National Observatory in Tucson, Arizona. Once installation is complete, it will run for five years.

    Mayall telescope interior

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)

    The DESI project is managed at the U.S. Department of Energy’s Lawrence Berkley National Laboratory (Berkeley Lab) in California, and the U.S. DOE’s Fermilab is contributing to the ambitious effort with specialty systems for collecting and analyzing the galactic light.

    “The collaborative effort to build DESI is an example of how science draws on expertise from multiple institutions toward a common goal, one that humanity is always moving toward: understanding the fundamentals of our universe,” said Berkeley Lab’s Michael Levi, DESI project director.

    One of the largest pieces Fermilab is contributing is the DESI corrector barrel. Fermilab collaborators designed, built and tested the barrel, which is roughly the size of a telephone booth. It plays a critical role: holding DESI’s six giant lenses in perfect alignment. To ensure spot-on precision, the barrel is designed so that the lenses are accurately positioned to within the width of a human hair. Collaborators at University College London recently finished installing the lenses in the barrel, and the whole ensemble will soon be lifted onto the telescope.

    “The barrel needs to be extremely precise,” said Gaston Gutierrez, Fermilab scientist managing the corrector barrel construction. “If there is any misalignment of the lenses, the error will be highly magnified, and the images will be blurred.”

    Fermilab also designed and built large structures that will support a cage surrounding the barrel. These were delivered to the Mayall in April, and their installation has begun.

    To convert the light from galaxies into digital information for analysis, DESI will use high-tech versions of the familiar components in typical hand-held cameras — charge coupled devices, or CCDs. Fermilab packaged and tested these sensitive devices before delivering them to Tucson.

    The job of collecting the galactic light belongs to DESI’s 5,000 fiber-optic cables, which will help record the spectra of each galaxy. For roughly 20 minutes, each one of the fibers will aim at a single galaxy and record its spectrum. Then the telescope will move to a new position in the sky, and all 5,000 fibers will be moved to point at new galaxies. Fermilab is developing the software that tells the instrument where in the sky to point those fibers. Without this automation, DESI would not be able to measure the millions of objects it plans to study.

    To fully understand the spectra that DESI will collect, scientists need to keep detailed information about the instrument and telescope status. In addition to the DESI barrel, Fermilab is creating an electronic logbook and a database to store the instrument control systems operational data. These will be used to keep track of the information on the systems required to operate DESI, such as how to read the CCDs, direct the telescope and ensure the apparatus for recording the spectra is working properly.

    Fermilab is developing the software that tells DESI where in the sky to point its 5,000 fiber-optic cables, a fraction of which are shown here. Photo: Lawrence Berkeley National Laboratory

    DESI’s predecessor, called the Dark Energy Camera (DECam), is currently mounted on Chile’s Victor Blanco telescope, the sister telescope of the Mayall.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    In 2012, researchers and technicians completed DECam’s construction for use in the five-year Dark Energy Survey, hosted by Fermilab. The same scientists who designed DECam are bringing their expertise and knowledge to DESI.

    The Dark Energy Survey and DECam serve as stepping stones to DESI. The DESI project will improve our understanding of the nature of dark energy by using the Dark Energy Survey’s results as a baseline. DECam’s data will also help DESI find the galaxies so the latter can take more precise spectra measurements to determine the galaxy’s redshift: The farther away a galaxy is from us, the more its light is stretched and shifted in the direction of redder (longer) wavelengths, by the expansion of the universe.

    “For the Dark Energy Survey, we are just taking images, but for DESI we are pointing fibers at galaxies and measuring spectra,” said Fermilab’s Brenna Flaugher, project manager of DES and one of the leading scientists for DESI. “So, it is sort of the next level of resolution in redshift.”

    DESI’s final pieces are planned to be installed by April 2019, with first light planned for May of that year.

    “DESI will help us understand the nature of dark energy,” Flaugher said. “And that will lead to a better understanding of the evolution of our universe.”

    Work on DESI is supported by DOE’s Office of Science along with several international partners.

    See the full article here .


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    FNAL Icon

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



    FNAL Muon g-2 studio

    FNAL Short-Baseline Near Detector under construction

    FNAL Mu2e solenoid

    Dark Energy Camera [DECam], built at FNAL

    FNAL DUNE Argon tank at SURF


    FNAL Don Lincoln


    FNAL Cryomodule Testing Facility

    FNAL Minos Far Detector

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

    FNAL/NOvA experiment map

    FNAL NOvA Near Detector


    FNAL Holometer

  • richardmitnick 12:47 pm on August 10, 2018 Permalink | Reply
    Tags: , , , , , Dark Energy, Dark Energy Survey Reveals Stellar Streams,   

    From AAS NOVA: “Dark Energy Survey Reveals Stellar Streams” 


    From AAS NOVA

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Over billions of years, globular clusters and dwarf galaxies orbiting the Milky Way have been torn apart and stretched out by tidal forces. The disruption of these ancient stellar populations results in narrow trails of stars called stellar streams. These stellar streams can help us understand how the Milky Way halo was constructed and what our galaxy’s dark matter distribution is like — but how do we find them?

    Along with cosmological simulations, like the Millennium Simulation pictured here, stellar streams can help us understand how dark matter is distributed in galaxies like the Milky Way. [Max Planck Institute for Astrophysics]

    On the Trail of Tidal Streams

    Understanding how our galaxy came to look the way it does is no easy task. Trying to discern the structure and formation history of the outer reaches of the Milky Way from our vantage point on Earth is a bit like trying to see the forest for the trees — while also trying to learn how old the forest is and where the trees came from!

    One way to do so is to search for the stellar streams that form when globular clusters and dwarf galaxies are disrupted and torn apart by our galaxy. Stellar streams tend to be faint, diffuse, and obscured by foreground stars, which makes them tricky to observe. Luckily, recent data releases from the Dark Energy Survey are perfectly suited to the task.

    Dark Energy Survey Brings Faint Stars to Light

    Nora Shipp (University of Chicago) and collaborators analyzed three years of data from the Dark Energy Survey in search of these stellar streams. The Dark Energy Survey is well-suited for stellar-stream hunts since it covers a wide area (5,000 square degrees of the southern sky) and can observe objects as faint as 26th magnitude.

    Shipp and collaborators use a matched-filter technique to pinpoint the old, low-metallicity stars that belong to stellar streams. This method uses the modeled properties of stars of a certain age — synthetic isochrones — to identify stars within a background stellar stream with minimal contamination from foreground stars.

    Using their matched filters, the authors found 15 stellar streams, 11 of which had never been seen before. They then estimated the age, metallicity, and distance modulus for each stream — all critical to understanding how the individual streams fit into the larger picture of galactic structure.

    A closer look at the stellar streams in the first quadrant of the surveyed area. Top: Density map of stars with a distance modulus of 15.4. Bottom: Stars with a distance modulus of 17.5. [Adapted from Shipp et al. 2018]

    Reconstructing the Galactic Halo

    These 11 newly discovered stellar streams will greatly enhance our understanding of the history of the galactic halo. Spectroscopy can help clarify the ages of these structures, while kinematic studies can help us understand if and how these structures are associated.

    Future work may also help us discern the origin of the streams; the stark dichotomy in the mass-to-light ratios of the stellar streams discovered in this work hints that it may be possible to link some streams to globular clusters and others to dwarf galaxies. Look for this and more exciting results from galactic archaeologists in the future!


    N. Shipp et al 2018 ApJ 862 114. doi:10.3847/1538-4357/aacdab

    Related journal articles
    See the full article for further references with links.

    See the full article here .


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    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

  • richardmitnick 12:54 pm on July 15, 2018 Permalink | Reply
    Tags: Dark Energy, , , Joshua Frieman, ,   

    From University of Chicago: “Studying universe requires ‘archaeology on the grand scale,’ physicist says” 

    U Chicago bloc

    From University of Chicago

    Jul 12, 2018
    Ali Sundermier

    Prof. Josh Frieman. Photo by Drew Reynolds

    Joshua Frieman looks to future as head of particle physics research at Fermilab.

    Particle physics research from Fermilab and SLAC are helping to improve our daily lives and the products we use. | Illustration by Sandbox Studio, Chicago.

    As director of the Dark Energy Survey, an international collaboration to map several hundred million galaxies using one of the world’s most powerful digital cameras, Fermilab scientist and University of Chicago professor Josh Frieman, PhD’89, leads more than 400 scientists from over 25 institutions across the world in the quest to unravel mysteries of the universe.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    The role, he said, has given him the opportunity to work with diverse groups of people toward a common goal, a skill that comes in handy as he takes on the role of Particle Physics Division head at the Department of Energy’s Fermi National Accelerator Laboratory.

    “Not only is Josh an outstanding scientist, he’s demonstrated an ability to lead a collaboration of hundreds of researchers who are situated all over the world,” said Fermilab Deputy Director Joe Lykken. “It requires a kind of cooperative spirit and skill that makes him perfect to lead one of the largest and most scientifically diverse divisions at Fermilab.”

    With a physicist for a father, Frieman said physics was certainly in the air when he was growing up. But it wasn’t until he was halfway through his undergraduate career that he discovered his passion for cosmology.

    “It was around 1980,” he said, “when the field was starting to go through a renaissance by marrying ideas from particle physics with cosmology so that we could make theories of the early universe. The idea of cosmology as archaeology on the grand scale—that we could make observations of the universe and use them like pottery shards to piece together the first few moments after the Big Bang—was very compelling to me. That’s how I decided to become a physicist, through the desire to understand the beginning of the universe.”

    Frieman did his graduate work on cosmological theory at the University of Chicago, going on to complete a postdoctoral position at SLAC National Accelerator Laboratory. In the late 1980s, he returned to Illinois to join the scientific staff at Fermilab, teaching astronomy and astrophysics part-time at the University of Chicago.

    Although Frieman started out in cosmological theory, as the field of cosmology evolved his interests became increasingly entangled with observations as opposed to pure theory, he said. In the late 1990s, he began working on the Sloan Digital Sky Survey, a project that later inspired him and other colleagues to develop the idea for the Dark Energy Survey.

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

    “My career has been partly a migration or expansion from theory to observations,” Frieman said. “Though I still think of myself as a lapsed or recovering theorist. Over that evolution, I have become involved with larger and larger international collaborations.”

    Frieman takes over as head of the Particle Physics Division from Fermilab scientist Patty McBride, who will become deputy spokesperson of the Compact Muon Solenoid experiment, one of the two major ongoing experiments at Europe’s Large Hadron Collider.

    CERN CMS Higgs Event

    CERN/CMS Detector

    The Particle Physics Division is home to a number of major efforts at Fermilab, including as an anchor to the U.S. participation in and contribution to the Compact Muon Solenoid experiment.

    Frieman said one of his main focuses is going to be working with the scientific staff to create a new vision for how to probe cosmic phenomena such as dark energy, dark matter and cosmic inflation, areas in which he has a wealth of experience.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington


    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:

    “I’m looking forward to the excitement of creating that plan and putting the laboratory on a good path toward its future in the cosmic frontier,” he said.

    The division also leads the laboratory’s muon program, and it works to answer questions about dark energy, dark matter and the cosmic microwave background [CMB].

    FNAL Muon G-2 studio

    CMB per ESA/Planck

    ESA/Planck 2009 to 2013

    In support of these scientific efforts, Frieman said, the division has a large complement of people conducting technical and engineering work as well as research and development towards new sorts of technologies for high-energy physics experiments.

    “It’s quite a broad portfolio, and part of the division head’s responsibilities is managing all of that effort,” Frieman said. “I’m hoping to enable people to accomplish the different objectives of each of those projects, which involve designing, building, operating and analyzing particle physics experiments, understanding them through theory, and interpreting and providing context for them.”

    To Frieman, the most rewarding aspect of working in physics is working with people to make discoveries about the universe.

    “What I’m looking forward to most is the continued excitement of discovery,” Frieman said. “It’s why many of us go into science. Increasingly we see that science, and in particular big science like particle physics, has become a real team or even community effort. And these communities face significant challenges. I see a large part of my job as fostering a positive environment in which this community can thrive so that people can do their best work and make fundamental discoveries. We’re making progress here every day, and that’s quite exciting.”

    See the full article here .

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    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

  • richardmitnick 10:18 am on May 14, 2018 Permalink | Reply
    Tags: , Dark Energy, , , University of Sidney   

    From University of Sidney and Durham University via COSMOS: “Multiverse theory cops a blow after dark energy findings” 


    U Sidney bloc

    University of Sidney


    Durham U bloc

    Durham University



    14 May 2018
    Andrew Masterson

    Each universe in a multiverse contains different levels of dark energy, according to the dominant theory. Credit: Stolk/Getty Images

    The question of dark energy in one universe does not require others to provide an answer.

    A hypothetical multiverse seems less likely after modelling by researchers in Australia and the UK threw one of its key assumptions into doubt.

    The multiverse concept suggests that our universe is but one of many. It finds support among some of the world’s most accomplished physicists, including Brian Greene, Max Tegmark, Neil deGrasse Tyson and the late Stephen Hawking.

    One of the prime attractions of the idea is that it potentially accounts for an anomaly in calculations for dark energy.

    The mysterious force is thought to be responsible for the accelerating expansion of our own universe. Current theories, however, predict there should be rather more of it around than there appears to be. This throws up another set of problems: if the amount of dark energy around was as much as equations require – and that is many trillions of times the level that seems to exist – the universe would expand so rapidly that stars and planets would not form – and life, thus, would not be possible.

    The multiverse idea to an extent accounts for and accommodates this oddly small – but life-permitting – dark energy quotient. Essentially it permits a curiously self-serving explanation: there are a vast number of universes all with differing amounts of dark energy. We exist in one that has an amount low enough to permit stars and so on to form, and thus life to exist. (And we find ourselves here, runs the logic, because we couldn’t find ourselves anywhere else.)

    So far, so anthropic. But now a group of astronomers, including Luke Barnes from the University of Sydney in Australia and Jaime Salcido from Durham University in the UK, has published two papers in the journal Monthly Notices of the Royal Astronomical Society [Galaxy formation efficiency and the multiverse explanation of the cosmological constant with EAGLE simulations and The impact of dark energy on galaxy formation. What does the future of our Universe hold? that show the dark energy and star formation balance isn’t quite as fine as previous estimates have suggested.

    The team created simulations of the universe using the supercomputer architecture contained within the Evolution and Assembly of GaLaxies and their Environments (EAGLE) project. This is a UK-based collaboration that models some 10,000 galaxies over a distance of 300 million-light years, and compares the results with actual observations from the Hubble Telescope and other observatories.

    The simulations allowed the researchers to adjust the amount of dark energy in the universe and watch what happened.

    The results were a surprise. The research revealed that the amount of dark energy could be increased a couple of hundred times – or reduced equally drastically – without substantially affecting anything else.

    “For many physicists, the unexplained but seemingly special amount of dark energy in our universe is a frustrating puzzle,” says Salcido.

    “Our simulations show that even if there was much more dark energy or even very little in the universe then it would only have a minimal effect on star and planet formation.”

    And this, he suggests, implies that life could potentially exist in many multiverse universes – ironically enough, an uncomfortable conclusion.

    “The multiverse was previously thought to explain the observed value of dark energy as a lottery – we have a lucky ticket and live in the universe that forms beautiful galaxies which permit life as we know it,” says Barnes.

    “Our work shows that our ticket seems a little too lucky, so to speak. It’s more special than it needs to be for life. This is a problem for the multiverse; a puzzle remains.”

    It is a puzzle that goes right to the heart of the matter: if the dark energy assumptions are flawed, does a multiverse even exist? The researchers acknowledge that their results do not preclude it – but they do diminish the likelihood.

    “The formation of stars in a universe is a battle between the attraction of gravity, and the repulsion of dark energy,” says co-author Richard Bower, also from Durham University.

    “We have found in our simulations that universes with much more dark energy than ours can happily form stars. So why such a paltry amount of dark energy in our universe?

    “I think we should be looking for a new law of physics to explain this strange property of our universe, and the multiverse theory does little to rescue physicists’ discomfort.”

    See the full article here .

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    Durham U campus

    Durham University is distinctive – a residential collegiate university with long traditions and modern values. We seek the highest distinction in research and scholarship and are committed to excellence in all aspects of education and transmission of knowledge. Our research and scholarship affect every continent. We are proud to be an international scholarly community which reflects the ambitions of cultures from around the world. We promote individual participation, providing a rounded education in which students, staff and alumni gain both the academic and the personal skills required to flourish.

    U Sidney campus

    Our founding principle as Australia’s first university was that we would be a modern and progressive institution. It’s an ideal we still hold dear today.

    When Charles William Wentworth proposed the idea of Australia’s first university, University of Sidney, in 1850, he imagined “the opportunity for the child of every class to become great and useful in the destinies of this country”.

    We’ve stayed true to that original value and purpose by promoting inclusion and diversity for the past 160 years.

    It’s the reason that, as early as 1881, we admitted women on an equal footing to male students. Oxford University didn’t follow suit until 30 years later, and Jesus College at Cambridge University did not begin admitting female students until 1974.

    It’s also why, from the very start, talented students of all backgrounds were given the chance to access further education through bursaries and scholarships.

    Today we offer hundreds of scholarships to support and encourage talented students, and a range of grants and bursaries to those who need a financial helping hand.

  • richardmitnick 7:14 am on March 20, 2018 Permalink | Reply
    Tags: , , , , Cosmological-constant problem, , Dark Energy, In 1998 astronomers discovered that the expansion of the cosmos is in fact gradually accelerating, , , , , Saul Perlmutter UC Berkeley Nobel laureate, , Why Does the Universe Need to Be So Empty?, Zero-point energy of the field   

    From The Atlantic Magazine and Quanta: “Why Does the Universe Need to Be So Empty?” 

    Quanta Magazine
    Quanta Magazine

    Atlantic Magazine

    The Atlantic Magazine

    Mar 19, 2018
    Natalie Wolchover

    Physicists have long grappled with the perplexingly small weight of empty space.

    The controversial idea that our universe is just a random bubble in an endless, frothing multiverse arises logically from nature’s most innocuous-seeming feature: empty space. Specifically, the seed of the multiverse hypothesis is the inexplicably tiny amount of energy infused in empty space—energy known as the vacuum energy, dark energy, or the cosmological constant. Each cubic meter of empty space contains only enough of this energy to light a light bulb for 11 trillionths of a second. “The bone in our throat,” as the Nobel laureate Steven Weinberg once put it [http://hetdex.org/dark_energy.html
    ], is that the vacuum ought to be at least a trillion trillion trillion trillion trillion times more energetic, because of all the matter and force fields coursing through it.


    Somehow the effects of all these fields on the vacuum almost equalize, producing placid stillness. Why is empty space so empty?

    While we don’t know the answer to this question—the infamous “cosmological-constant problem”—the extreme vacuity of our vacuum appears necessary for our existence. In a universe imbued with even slightly more of this gravitationally repulsive energy, space would expand too quickly for structures like galaxies, planets, or people to form. This fine-tuned situation suggests that there might be a huge number of universes, all with different doses of vacuum energy, and that we happen to inhabit an extraordinarily low-energy universe because we couldn’t possibly find ourselves anywhere else.

    Some scientists bristle at the tautology of “anthropic reasoning” and dislike the multiverse for being untestable. Even those open to the multiverse idea would love to have alternative solutions to the cosmological constant problem to explore. But so far it has proved nearly impossible to solve without a multiverse. “The problem of dark energy [is] so thorny, so difficult, that people have not got one or two solutions,” says Raman Sundrum, a theoretical physicist at the University of Maryland.

    To understand why, consider what the vacuum energy actually is. Albert Einstein’s general theory of relativity says that matter and energy tell space-time how to curve, and space-time curvature tells matter and energy how to move. An automatic feature of the equations is that space-time can possess its own energy—the constant amount that remains when nothing else is there, which Einstein dubbed the cosmological constant. For decades, cosmologists assumed its value was exactly zero, given the universe’s reasonably steady rate of expansion, and they wondered why. But then, in 1998, astronomers discovered that the expansion of the cosmos is in fact gradually accelerating, implying the presence of a repulsive energy permeating space. Dubbed dark energy by the astronomers, it’s almost certainly equivalent to Einstein’s cosmological constant. Its presence causes the cosmos to expand ever more quickly, since, as it expands, new space forms, and the total amount of repulsive energy in the cosmos increases.

    However, the inferred density of this vacuum energy contradicts what quantum-field theory, the language of particle physics, has to say about empty space. A quantum field is empty when there are no particle excitations rippling through it. But because of the uncertainty principle in quantum physics, the state of a quantum field is never certain, so its energy can never be exactly zero. Think of a quantum field as consisting of little springs at each point in space. The springs are always wiggling, because they’re only ever within some uncertain range of their most relaxed length. They’re always a bit too compressed or stretched, and therefore always in motion, possessing energy. This is called the zero-point energy of the field. Force fields have positive zero-point energies while matter fields have negative ones, and these energies add to and subtract from the total energy of the vacuum.

    The total vacuum energy should roughly equal the largest of these contributing factors. (Say you receive a gift of $10,000; even after spending $100, or finding $3 in the couch, you’ll still have about $10,000.) Yet the observed rate of cosmic expansion indicates that its value is between 60 and 120 orders of magnitude smaller than some of the zero-point energy contributions to it, as if all the different positive and negative terms have somehow canceled out. Coming up with a physical mechanism for this equalization is extremely difficult for two main reasons.

    First, the vacuum energy’s only effect is gravitational, and so dialing it down would seem to require a gravitational mechanism. But in the universe’s first few moments, when such a mechanism might have operated, the universe was so physically small that its total vacuum energy was negligible compared to the amount of matter and radiation. The gravitational effect of the vacuum energy would have been completely dwarfed by the gravity of everything else. “This is one of the greatest difficulties in solving the cosmological-constant problem,” the physicist Raphael Bousso wrote in 2007. A gravitational feedback mechanism precisely adjusting the vacuum energy amid the conditions of the early universe, he said, “can be roughly compared to an airplane following a prescribed flight path to atomic precision, in a storm.”

    Compounding the difficulty, quantum-field theory calculations indicate that the vacuum energy would have shifted in value in response to phase changes in the cooling universe shortly after the Big Bang. This raises the question of whether the hypothetical mechanism that equalized the vacuum energy kicked in before or after these shifts took place. And how could the mechanism know how big their effects would be, to compensate for them?

    So far, these obstacles have thwarted attempts to explain the tiny weight of empty space without resorting to a multiverse lottery. But recently, some researchers have been exploring one possible avenue: If the universe did not bang into existence, but bounced instead, following an earlier contraction phase, then the contracting universe in the distant past would have been huge and dominated by vacuum energy. Perhaps some gravitational mechanism could have acted on the plentiful vacuum energy then, diluting it in a natural way over time. This idea motivated the physicists Peter Graham, David Kaplan, and Surjeet Rajendran to discover a new cosmic bounce model, though they’ve yet to show how the vacuum dilution in the contracting universe might have worked.

    In an email, Bousso called their approach “a very worthy attempt” and “an informed and honest struggle with a significant problem.” But he added that huge gaps in the model remain, and “the technical obstacles to filling in these gaps and making it work are significant. The construction is already a Rube Goldberg machine, and it will at best get even more convoluted by the time these gaps are filled.” He and other multiverse adherents see their answer as simpler by comparison.

    See the full article here .

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  • richardmitnick 3:36 pm on February 16, 2018 Permalink | Reply
    Tags: , , , , , , Dark Energy, , European backed missions,   

    From CERN Courier: “Europe defines astroparticle strategy” 

    CERN Courier

    Feb 16, 2018


    Multi-messenger astronomy, neutrino physics and dark matter are among several topics in astroparticle physics set to take priority in Europe in the coming years, according to a report by the Astroparticle Physics European Consortium (APPEC).

    The APPEC strategy for 2017–2026, launched at an event in Brussels on 9 January, is the culmination of two years of consultation with the astroparticle and related communities. It involved some 20 agencies in 16 countries and includes representation from the European Committee for Future Accelerators, CERN and the European Southern Observatory (ESO).

    Lying at the intersection of astronomy, particle physics and cosmology, astroparticle physics is well placed to search for signs of physics beyond the standard models of particle physics and cosmology. As a relatively new field, however, European astroparticle physics does not have dedicated intergovernmental organisations such as CERN or ESO to help drive it. In 2001, European scientific agencies founded APPEC to promote cooperation and coordination, and specifically to formulate a strategy for the field.

    Building on earlier strategies released in 2008 and 2011, APPEC’s latest roadmap presents 21 recommendations spanning scientific issues, organisational aspects and societal factors such as education and industry, helping Europe to exploit tantalising potential for new discoveries in the field.

    The recent detection of gravitational waves from the merger of two neutron stars (CERN Courier December 2017 p16) opens a new line of exploration based on the complementary power of charged cosmic rays, electromagnetic waves, neutrinos and gravitational waves for the study of extreme events such as supernovae, black-hole mergers and the Big Bang itself. “We need to look at cross-fertilisation between these modes to maximise the investment in facilities,” says APPEC chair Antonio Masiero of the INFN and the University of Padova. “This is really going to become big.”

    APPEC strongly supports Europe’s next-generation ground-based gravitational interferometer, the Einstein Telescope, and the space-based LISA detector.

    ASPERA Einstein Telescope

    ESA/NASA eLISA space based the future of gravitational wave research

    In the neutrino sector, KM3NeT is being completed for high-energy cosmic neutrinos at its site in Sicily, as well as for precision studies of atmospheric neutrinos at its French site near Toulon.

    Artist’s expression of the KM3NeT neutrino telescope

    Europe is also heavily involved in the upgrade of the leading cosmic-ray facility the Pierre Auger Observatory in Argentina.

    Pierre Auger Observatory in the western Mendoza Province, Argentina, near the Andes, at an altitude of 1330 m–1620 m, average ~1400 m

    Significant R&D work is taking place at CERN’s neutrino platform for the benefit of long- and short-baseline neutrino experiments in Japan and the US (CERN Courier July/August 2016 p21), and Europe is host to several important neutrino experiments. Among them are KATRIN at KIT in Germany, which is about to begin measurements of the neutrino absolute mass scale, and experiments searching for neutrinoless double-beta decay (NDBD) such as GERDA and CUORE at INFN’s Gran Sasso National Laboratory (CERN Courier December 2017 p8).

    KIT Katrin experiment

    CUORE experiment UC Berkeley, experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS), a search for neutrinoless double beta decay

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    There are plans to join forces with experiments in the US to build the next generation of NDBD detectors. APPEC has a similar vision for dark matter, aiming to converge next year on plans for an “ultimate” 100-tonne scale detector based on xenon and argon via the DARWIN and Argo projects.

    DARWIN Dark Matter experiment

    APPEC also supports ESA’s Euclid mission, which will establish European leadership in dark-energy research, and encourages continued European participation in the US-led DES and LSST ground-based projects.

    Dark Energy Camera [DECam], built at FNAL

    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    Following from ESA’s successful Planck mission, APPEC strongly endorses a European-led satellite mission, such as COrE, to map the cosmic-microwave background and the consortium plans to enhance its interactions with its present observers ESO and CERN in areas of mutual interest.


    “It is important at this time to put together the human forces,” says Masiero. “APPEC will exercise influence in the European Strategy for Particle Physics, and has a significant role to play in the next European Commission Framework Project, FP9.”

    A substantial investment is needed to build the next generation of astroparticle-physics research, the report concedes. According to Masiero, European agencies within APPEC currently invest around €80 million per year in astroparticle-related activities, in addition to funding large research infrastructures. A major effort in Europe is necessary for it to keep its leading position. “Many young people are drawn into science by challenges like dark matter and, together with Europe’s existing research infrastructures in the field, we have a high technological level and are pushing industries to develop new technologies,” continues Masiero. “There are great opportunities ahead in European astroparticle physics.”

    See the full article here .

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