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  • richardmitnick 1:46 pm on September 13, 2019 Permalink | Reply
    Tags: , , , , Dark Energy, ,   

    From NASA JPL-Caltech: “NASA’s WFIRST Will Help Uncover the Universe’s Fate” 

    NASA JPL Banner

    From NASA JPL-Caltech

    September 13, 2019

    Calla Cofield
    Jet Propulsion Laboratory, Pasadena, Calif.
    626-808-2469
    calla.e.cofield@jpl.nasa.gov

    Written by Ashley Balzer
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    1
    NASA WFIRST depiction. Credit: NASA’s Goddard Space Flight Center

    Scientists have discovered that a mysterious pressure dubbed “dark energy” makes up about 68% of the total energy content of the cosmos, but so far we don’t know much more about it.

    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

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    Exploring the nature of dark energy is one of the primary reasons NASA is building the Wide Field Infrared Survey Telescope (WFIRST), a space telescope whose measurements will help illuminate the dark energy puzzle. With a better understanding of dark energy, we will have a better sense of the past and future evolution of the universe.

    An Expanding Cosmos

    Until the 20th century, most people believed that the universe was static, remaining essentially unchanged throughout eternity. When Einstein developed his general theory of relativity in 1915, describing how gravity acts across the fabric of space-time, he was puzzled to find that the theory indicated the cosmos must either expand or contract. He made changes to preserve a static universe, adding something he called the “cosmological constant,” even though there was no evidence it actually existed. This mysterious force was supposed to counteract gravity to hold everything in place.

    However, as the 1920s were coming to a close, astronomer Georges Lemaitre, and then Edwin Hubble, made the startling discovery that with very few exceptions, galaxies are racing away from each other.

    Edwin Hubble looking through a 100-inch Hooker telescope at Mount Wilson in Southern California, 1929 discovers the Universe is Expanding

    The universe was far from static – it was ballooning outward. Consequently, if we imagine rewinding this expansion, there must have been a time when everything in the universe was almost impossibly hot and close together.

    The End of the Universe: Fire or Ice?

    The Big Bang theory describes the expansion and evolution of the universe from this initial superhot, superdense state. Scientists theorized that gravity would eventually slow and possibly even completely reverse this expansion. If the universe had enough matter in it, gravity would overcome the expansion, and the universe would collapse in a fiery “Big Crunch.”

    If not, the expansion would never end – galaxies would grow farther and farther away until they pass the edge of the observable universe. Our distant descendants might have no knowledge of the existence of other galaxies since they would be too far away to be visible. Much of modern astronomy might one day be reduced to mere legend as the universe gradually fades to an icy black.

    The Universe Isn’t Just Expanding – It’s Accelerating

    Astronomers have measured the rate of expansion by using ground-based telescopes to study relatively nearby supernova explosions. The mystery escalated in 1998 when Hubble Space Telescope observations of more distant supernovae helped show that the universe actually expanded more slowly in the past than it does today.(?) The expansion of the universe is not slowing down due to gravity, as everyone thought. It’s speeding up.

    Saul Perlmutter [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt and Adam Riess [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

    Fast forward to today. While we still don’t know what exactly is causing the acceleration, it has been given a name – dark energy. This mysterious pressure remained undiscovered for so long because it is so weak that gravity overpowers it on the scale of humans, planets and even the galaxy. It is present in the room with you as you read, within your very body, but gravity counteracts it so you don’t go flying out of your seat. It is only on an intergalactic scale that dark energy becomes noticeable, acting like a sort of weak opposition to gravity.

    What Is Dark Energy?

    What exactly is dark energy? More is unknown than known, but theorists are chasing down a couple of possible explanations. Cosmic acceleration could be caused by a new energy component, which would require some adjustments to Einstein’s theory of gravity – perhaps the cosmological constant, which Einstein called his biggest blunder, is real after all.

    Alternatively, Einstein’s theory of gravity may break down on cosmological scales. If this is the case, the theory will need to be replaced with a new one that incorporates the cosmic acceleration we have observed. Theorists still don’t know what the correct explanation is, but WFIRST will help us find out.

    WFIRST Will Illuminate Dark Energy

    Previous missions have gathered some clues, but so far they haven’t yielded results that strongly favor one explanation over another. With the same resolution as Hubble’s cameras but a field of view that is 100 times larger, WFIRST will generate never-before-seen big pictures of the universe. The new mission will advance the exploration of the dark energy mystery in ways that other telescopes can’t by mapping how matter is structured and distributed throughout the cosmos, and also by measuring large numbers of distant supernovae. The results will indicate how dark energy acts across the universe, and whether and how it has changed over cosmic history.

    The mission will use three survey methods to search for an explanation of dark energy. The High Latitude Spectroscopic Survey will measure accurate distances and positions of millions of galaxies using a “standard ruler” technique. Measuring how the distribution of galaxies varies with distance will give us a window into the evolution of dark energy over time. This study will connect the galaxies’ distances with the echoes of sound waves just after the Big Bang and will test Einstein’s theory of gravity over the age of the universe.

    The High Latitude Imaging Survey will measure the shapes and distances of multitudes of galaxies and galaxy clusters. The immense gravity of massive objects warps space-time and causes more distant galaxies to appear distorted. Observing the degree of distortion allows scientists to infer the distribution of mass throughout the cosmos. This includes all of the matter we can see directly, like planets and stars, as well as dark matter – another dark cosmic mystery which is visible only through its gravitational effects on normal matter. This survey will provide an independent measurement of the growth of large-scale structure in the universe and how dark energy has affected the cosmos.

    WFIRST will also conduct a survey of one type of exploding star, building on the observations that led to the discovery of accelerated expansion. Type Ia supernovae occur when a white dwarf star explodes. Type Ia supernovae generally have the same absolute brightness at their peak, making them so-called “standard candles.” That means astronomers can determine how far away they are by seeing how bright they look from Earth – and the farther they are, the dimmer they appear. Astronomers will also look at the particular wavelengths of light coming from the supernovae to find out how fast the dying stars are moving away from us. By combining distances with brightness measurements, scientists will see how dark energy has evolved over time, providing a cross-check with the two high-latitude surveys.

    “The WFIRST mission is unique in combining these three methods. It will lead to a very robust and rich interpretation of the effects of dark energy and will allow us to make a definite statement about the nature of dark energy,” said Olivier Doré, a research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and leader of the team planning the first two survey methods with WFIRST.

    Discovering how dark energy has affected the universe’s expansion in the past will shed some light on how it will influence the expansion in the future. If it continues to accelerate the universe’s expansion, we may be destined to experience a “Big Rip.” In this scenario, dark energy would eventually become dominant over the fundamental forces, causing everything that is currently bound together – galaxies, planets, people – to break apart. Exploring dark energy will allow us to investigate, and possibly even foresee, the universe’s fate.

    For more information about WFIRST, visit:

    http://www.nasa.gov/wfirst.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA JPL Campus

    Jet Propulsion Laboratory (JPL)) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge, on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo

    NASA image

     
  • richardmitnick 9:00 am on September 12, 2019 Permalink | Reply
    Tags: , Dark Energy, , University of Hawai’i   

    From University of Hawaii via Science Alert: “Black Holes May Hide Cores of Pure Dark Energy That Keep The Universe Expanding 

    From University of Hawaii

    via

    ScienceAlert

    Science Alert

    12 SEP 2019
    MIKE MCRAE

    1
    (Just_Super/iStock)

    A fifty-year-old hypothesis predicting the existence of bodies dubbed Generic Objects of Dark Energy (GEODEs) is getting a second look in light of a proposed correction to assumptions we use to model the way our Universe expands.

    If this new version of a classic cosmological model is correct, some black holes could hide cores of pure dark energy, pushing our Universe apart at the seams.

    University of Hawai’i astrophysicist Kevin Croker and mathematician Joel Weiner teamed up to challenge the broadly accepted notion that when it comes to the Universe’s growing waistline, its contents are largely irrelevant.

    “For 80 years, we’ve generally operated under the assumption that the Universe, in broad strokes, was not affected by the particular details of any small region,” said Croker.

    “It is now clear that general relativity can observably connect collapsed stars – regions the size of Honolulu – to the behaviour of the Universe as a whole, over a thousand billion billion times larger.”

    Not only could this alternative interpretation of fundamental physics change how we understand the Universe’s expansion, but we might need to also consider how that growth might affect compact objects like the cores of collapsing stars.

    The fact that space has been steadily adding real estate for the past 13.8 billion years is by now a widely accepted feature of our Universe.

    The set of equations we use to describe this expansion was first put to paper just under a century ago by the Russian physicist Alexander Friedmann. They provided a solution to Einstein’s theory of general relativity that now underpins our big picture model of cosmology.

    As useful as Friedmann’s equations have been, they’re based on the assumption that any matter floating around inside this expanding space is more or less made of the same kind of stuff, and spread out fairly evenly.

    This means we tend to ignore the swirls of stars and galaxies – just like we might not include ducks in the hydrodynamics of a lake.

    But Croker and Weiner wonder what might happen to space and the objects it contains if we made some reasonable changes to the assumptions that inform these equations.

    The consequences aren’t trivial.

    According to their adjusted model, the averaged contributions of our metaphorical ducks might affect the lake’s water after all.

    What’s more, the lake’s expansion would also affect how the ducks swim, causing them to lose or gain energy depending on their species.

    Theoretically, this interpretation would mean we need to take the Universe’s growth into account when describing certain phenomena, such as the death of a star.

    In 1966, a Russian physicist named Erast Gliner considered how some densities of space close to the Big Bang might look – in terms of relativity – like a vacuum that could counter the effects of gravity.

    His solution would look like a black hole from the outside. But inside would be a bubble of energy shoving against the surrounding Universe.

    Half a century later, astrophysicists are on the hunt for just such a pushing power that might be responsible for the Universe’s expansion picking up speed over time.

    Today we refer to this undescribed force as dark energy, but could Gliner’s pockets of relativistic nothingness be the source of our Universe’s accelerating expansion?

    Based on Croker and Weiner’s work, if just a few ancient stars were to have collapsed into Gliner’s GEODEs instead of the more typical puckered space of a singularity, their average effect on expanding space would look just like dark energy.

    The pair go further, applying their corrected model to the first observation of gravitational waves from a black hole collision as measured by LIGO.

    To make the math fit, it’s assumed the stars that formed the merging black holes formed in a low-metallicity environment, which makes them somewhat rare.

    Technically, the energy of a GEODE should evolve as the Universe grows, effectively compacting as a cosmological equivalent of a ‘blueshift’.

    If the merging black holes were GEODEs, according to the researchers, there’d be no need to assume the black holes were born in an unusual patch of space.

    “What we have shown is that if GEODEs do exist, then they can easily give rise to observed phenomena that presently lack convincing explanations,” the researchers said.

    “We anticipate numerous other observational consequences of a GEODE scenario, including many ways to exclude it. We’ve barely begun to scratch the surface.”

    Testing assumptions like these is a vital part of physics. We’re a long way off including GEODEs in any official astrophysical zoo of weird objects, but it’s possible these could be the dark hearts of the Universe we’ve been looking for.

    This research was published in The Astrophysical Journal.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    System Overview

    The University of Hawai‘i System includes 10 campuses and dozens of educational, training and research centers across the Hawaiian Islands. As the public system of higher education in Hawai‘i, UH offers opportunities as unique and diverse as our Island home.

    The 10 UH campuses and educational centers on six Hawaiian Islands provide unique opportunities for both learning and recreation.

    UH is the State’s leading engine for economic growth and diversification, stimulating the local economy with jobs, research and skilled workers.

     
  • richardmitnick 12:22 pm on August 19, 2019 Permalink | Reply
    Tags: , , , , Dark Energy,   

    From Imperial College London: “Lab-based dark energy experiment narrows search options for elusive force” 

    Imperial College London
    From Imperial College London

    19 August 2019
    Hayley Dunning

    1
    No image caption or credit.

    An experiment to test a popular theory of dark energy has found no evidence of new forces, placing strong constraints on related theories.

    Dark energy is the name given to an unknown force that is causing the universe to expand at an accelerating rate.

    Some physicists propose dark energy is a ‘fifth’ force that acts on matter, beyond the four already known – gravitational, electromagnetic, and the strong and weak nuclear interactions.

    However, researchers think this fifth force may be ‘screened’ or ‘hidden’ for large objects like planets or weights on Earth, making it difficult to detect.

    Now, researchers at Imperial College London and the University of Nottingham have tested the possibility that this fifth force is acting on single atoms, and found no evidence for it in their most recent experiment.

    This could rule out popular theories of dark energy that modify the theory of gravity, and leaves fewer places to search for the elusive fifth force.

    Finding the fifth force

    The experiment, performed at Imperial College London and analysed by theorists at the University of Nottingham, is reported today in Physical Review Letters.

    Professor Ed Copeland, from the Centre for Astronomy & Particle Physics at the University of Nottingham, said: “This experiment, connecting atomic physics and cosmology, has allowed us to rule out a wide class of models that have been proposed to explain the nature of dark energy, and will enable us to constrain many more dark energy models.”

    The experiment tested theories of dark energy that propose the fifth force is comparatively weaker when there is more matter around – the opposite of how gravity behaves.

    This would mean it is strong in a vacuum like space, but is weak when there is lots of matter around. Therefore, experiments using two large weights would mean the force becomes too weak to measure.

    Experiment with a single atom

    The researchers instead tested a larger weight with an incredibly small weight – a single atom – where the force should have been observed if it exists.

    The team used an atom interferometer to test whether there were any extra forces that could be the fifth force acting on an atom. A marble-sized sphere of metal was placed in a vacuum chamber and atoms were allowed to free-fall inside the chamber.

    The theory is, if there is a fifth force acting between the sphere and atom, the atom’s path will deviate slightly as it passes by the sphere, causing a change in the path of the falling atom. However, no such force was found.

    Professor Ed Hinds, from the Department of Physics at Imperial, said: “It is very exciting to be able to discover something about the evolution of the universe using a table-top experiment in a London basement.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Imperial College London

    Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

     
  • richardmitnick 1:27 pm on August 2, 2019 Permalink | Reply
    Tags: "We Have Already Entered The Sixth And Final Era Of Our Universe", , , , , Dark Energy, , ,   

    From Ethan Siegel: “We Have Already Entered The Sixth And Final Era Of Our Universe” 

    From Ethan Siegel
    Aug 2, 2019

    Timeline of the Inflationary Universe WMAP

    From the inflationary state that preceded the Big Bang to our cold, lonely, dark energy-dominated fate, the Universe goes through six different eras. We’re living in the last one already.

    The Universe is not the same today as it was yesterday. With each moment that goes by, a number of subtle but important changes occur, even if many of them are imperceptible on measurable, human timescales. The Universe is expanding, which means that the distances between the largest cosmic structures are increasing with time.

    A second ago, the Universe was slightly smaller; a second from now, the Universe will be slightly larger. But those subtle changes both build up over large, cosmic timescales, and affect more than just distances. As the Universe expands, the relative importance of radiation, matter, neutrinos, and dark energy all change. The temperature of the Universe changes. And what you’d see in the sky would change dramatically as well. All told, there are six different eras we can break the Universe into, and we’re already in the final one.

    2
    How matter (top), radiation (middle), and a cosmological constant (bottom) all evolve with time in an expanding Universe. As the Universe expands, the matter density dilutes, but the radiation also becomes cooler as its wavelengths get stretched to longer, less energetic states. Dark energy’s density, on the other hand, will truly remain constant if it behaves as is currently thought: as a form of energy intrinsic to space itself. (E. SIEGEL / BEYOND THE GALAXY)

    The reason for this can be understood from the graph above. Everything that exists in our Universe has a certain amount of energy in it: matter, radiation, dark energy, etc. As the Universe expands, the volume that these forms of energy occupy changes, and each one will have its energy density evolve differently. In particular, if we define the observable horizon by the variable a, then:

    matter will have its energy density evolve as 1/a³, since (for matter) density is just mass over volume, and mass can easily be converted to energy via E = mc²,
    radiation will have its energy density evolve as 1/a⁴, since (for radiation) the number density is the number of particles divided by volume, and the energy of each individual photon stretches as the Universe expands, adding an additional factor of 1/a relative to matter,
    and dark energy is a property of space itself, so its energy density remains constant (1/a⁰), irrespective of the Universe’s expansion or volume.

    3
    A visual history of the expanding Universe includes the hot, dense state known as the Big Bang and the growth and formation of structure subsequently. The full suite of data, including the observations of the light elements and the cosmic microwave background, leaves only the Big Bang as a valid explanation for all we see. As the Universe expands, it also cools, enabling ions, neutral atoms, and eventually molecules, gas clouds, stars, and finally galaxies to form. (NASA / CXC / M. WEISS)

    A Universe that has been around longer, therefore, will have expanded more. It will be cooler in the future and was hotter in the past; it was gravitationally more uniform in the past and is clumpier now; it was smaller in the past and will be much, much larger in the future.

    By applying the laws of physics to the Universe, and comparing the possible solutions with the observations and measurements we’ve obtained, we can determine both where we came from and where we’re headed. We can extrapolate our past history all the way back to the beginning of the hot Big Bang and even before, to a period of cosmic inflation. We can extrapolate our current Universe into the far distant future as well, and foresee the ultimate fate that awaits everything that exists.

    4
    Our entire cosmic history is theoretically well-understood, but only because we understand the theory of gravitation that underlies it, and because we know the Universe’s present expansion rate and energy composition. Light will always continue to propagate through this expanding Universe, and we will continue to receive that light arbitrarily far into the future, but it will be limited in time as far as what reaches us. We will need to probe to fainter brightnesses and longer wavelengths to continue to see the objects presently visible, but those are technological, not physical, limitations. (NICOLE RAGER FULLER / NATIONAL SCIENCE FOUNDATION)

    When we draw the dividing lines based on how the Universe behaves, we find that there are six different eras that will come to pass.

    Inflationary era: which preceded and set up the hot Big Bang.
    Primordial Soup era: from the start of the hot Big Bang until the final transformative nuclear & particle interactions occur in the early Universe.
    Plasma era: from the end of non-scattering nuclear and particle interactions until the Universe cools enough to stably form neutral matter.
    Dark Ages era: from the formation of neutral matter until the first stars and galaxies reionize the intergalactic medium of the Universe completely.
    Stellar era: from the end of reionization until the gravity-driven formation and growth of large-scale structure ceases, when the dark energy density dominates over the matter density.
    Dark Energy era: the final stage of our Universe, where the expansion accelerates and disconnected objects speed irrevocably and irreversibly away from one another.

    We already entered this final era billions of years ago. Most of the important events that will define our Universe’s history have already occurred.

    5
    Fluctuations in spacetime itself at the quantum scale get stretched across the Universe during inflation, giving rise to imperfections in both density and gravitational waves. Whether inflation arose from an eventual singularity or not is unknown, but the signatures of whether it occurred are accessible in our observable Universe. (E. SIEGEL, WITH IMAGES DERIVED FROM ESA/PLANCK AND THE DOE/NASA/ NSF INTERAGENCY TASK FORCE ON CMB RESEARCH)

    1.) Inflationary era. Prior to the hot Big Bang, the Universe wasn’t filled with matter, antimatter, dark matter or radiation. It wasn’t filled with particles of any type. Instead, it was filled with a form of energy inherent to space itself: a form of energy that caused the Universe to expand both extremely rapidly and relentlessly, in an exponential fashion.

    Inflation

    4
    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:

    Alan Guth’s original notes on inflation

    It stretched the Universe, from whatever geometry it once had, into a state indistinguishable from spatially flat.
    It expanded a small, causally connected patch of the Universe to one much larger than our presently visible Universe: larger than the current causal horizon.
    It took any particles that may have been present and expanded the Universe so rapidly that none of them are left inside a region the size of our visible Universe.
    And the quantum fluctuations that occurred during inflation created the seeds of structure that gave rise to our vast cosmic web today.

    And then, abruptly, some 13.8 billion years ago, inflation ended. All of that energy, once inherent to space itself, got converted into particles, antiparticles, and radiation. With this transition, the inflationary era ended, and the hot Big Bang began.

    CMB per ESA/Planck

    ESA/Planck 2009 to 2013

    6
    At the high temperatures achieved in the very young Universe, not only can particles and photons be spontaneously created, given enough energy, but also antiparticles and unstable particles as well, resulting in a primordial particle-and-antiparticle soup. Yet even with these conditions, only a few specific states, or particles, can emerge. (BROOKHAVEN NATIONAL LABORATORY)

    2.) Primordial Soup era. Once the expanding Universe is filled with matter, antimatter and radiation, it’s going to cool. Whenever particles collide, they’ll produce whatever particle-antiparticle pairs are allowed by the laws of physics. The primary restriction comes only from the energies of the collisions involved, as the production is governed by E = mc².

    As the Universe cools, the energy drops, and it becomes harder and harder to create more massive particle-antiparticle pairs, but annihilations and other particle reactions continue unabated. 1-to-3 seconds after the Big Bang, the antimatter is all gone, leaving only matter behind. 3-to-4 minutes after the Big Bang, stable deuterium can form, and nucleosynthesis of the light elements occurs. And after some radioactive decays and a few final nuclear reactions, all we have left is a hot (but cooling) ionized plasma consisting of photons, neutrinos, atomic nuclei and electrons.

    7
    At early times (left), photons scatter off of electrons and are high-enough in energy to knock any atoms back into an ionized state. Once the Universe cools enough, and is devoid of such high-energy photons (right), they cannot interact with the neutral atoms, and instead simply free-stream, since they have the wrong wavelength to excite these atoms to a higher energy level. (E. SIEGEL / BEYOND THE GALAXY)

    3.) Plasma era. Once those light nuclei form, they’re the only positively (electrically) charged objects in the Universe, and they’re everywhere. Of course, they’re balanced by an equal amount of negative charge in the form of electrons. Nuclei and electrons form atoms, and so it might seem only natural that these two species of particle would find one another immediately, forming atoms and paving the way for stars.

    Unfortunately for them, they’re vastly outnumbered — by more than a billion to one — by photons. Every time an electron and a nucleus bind together, a high-enough energy photon comes along and blasts them apart. It isn’t until the Universe cools dramatically, from billions of degrees to just thousands of degrees, that neutral atoms can finally form. (And even then, it’s only possible because of a special atomic transition.)

    At the beginning of the Plasma era, the Universe’s energy content is dominated by radiation. By the end, it’s dominated by normal and dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    This third phase takes us to 380,000 years after the Big Bang.

    9
    Schematic diagram of the Universe’s history, highlighting reionization. Before stars or galaxies formed, the Universe was full of light-blocking, neutral atoms. While most of the Universe doesn’t become reionized until 550 million years afterwards, with some regions achieving full reionization earlier and others later. The first major waves of reionization begin happening at around 250 million years of age, while a few fortunate stars may form just 50-to-100 million years after the Big Bang. With the right tools, like the James Webb Space Telescope, we may begin to reveal the earliest galaxies.(S. G. DJORGOVSKI ET AL., CALTECH DIGITAL MEDIA CENTER)

    4.) Dark Ages era. Filled with neutral atoms, at last, gravitation can begin the process of forming structure in the Universe. But with all these neutral atoms around, what we presently know as visible light would be invisible all throughout the sky.

    Why’s that? Because neutral atoms, particularly in the form of cosmic dust, are outstanding at blocking visible light.

    In order to end these dark ages, the intergalactic medium needs to be reionized. That requires enormous amounts of star-formation and tremendous numbers of ultraviolet photons, and that requires time, gravitation, and the start of the cosmic web. The first major regions of reionization take place 200–250 million years after the Big Bang, but reionization doesn’t complete, on average, until the Universe is 550 million years old. At this point, the star-formation rate is still increasing, and the first massive galaxy clusters are just beginning to form.

    10
    The galaxy cluster Abell 370, shown here, was one of the six massive galaxy clusters imaged in the Hubble Frontier Fields program. Since other great observatories were also used to image this region of sky, thousands of ultra-distant galaxies were revealed. By observing them again with a new scientific goal, Hubble’s BUFFALO (Beyond Ultra-deep Frontier Fields And Legacy Observations) program will obtain distances to these galaxies, enabling us to better understand how galaxies formed, evolved, and grew up in our Universe. When combined with intracluster light measurements, we could gain an even greater understanding, via multiple lines of evidence of the same structure, of the dark matter inside. (NASA, ESA, A. KOEKEMOER (STSCI), M. JAUZAC (DURHAM UNIVERSITY), C. STEINHARDT (NIELS BOHR INSTITUTE), AND THE BUFFALO TEAM)

    5.) Stellar era. Once the dark ages are over, the Universe is now transparent to starlight. The great recesses of the cosmos are now accessible, with stars, star clusters, galaxies, galaxy clusters, and the great, growing cosmic web all waiting to be discovered. The Universe is dominated, energy-wise, by dark matter and normal matter, and the gravitationally bound structures continue to grow larger and larger.

    The star-formation rate rises and rises, peaking about 3 billion years after the Big Bang. At this point, new galaxies continue to form, existing galaxies continue to grow and merge, and galaxy clusters attract more and more matter into them. But the amount of free gas within galaxies begins to drop, as the enormous amounts of star-formation have used up a large amount of it. Slowly but steadily, the star-formation rate drops.

    As time goes forward, the stellar death rate will outpace the birth rate, a fact made worse by the following surprise: as the matter density drops with the expanding Universe, a new form of energy — dark energy — begins to appear and dominate. 7.8 billion years after the Big Bang, distant galaxies stop slowing down in their recession from one another, and begin speeding up again. The accelerating Universe is upon us. A little bit later, 9.2 billion years after the Big Bang, dark energy becomes the dominant component of energy in the Universe. At this point, we enter the final era.

    10
    The different possible fates of the Universe, with our actual, accelerating fate shown at the right. After enough time goes by, the acceleration will leave every bound galactic or supergalactic structure completely isolated in the Universe, as all the other structures accelerate irrevocably away. We can only look to the past to infer dark energy’s presence and properties, which require at least one constant, but its implications are larger for the future.(NASA & ESA)

    6.) Dark Energy age.

    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

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    Once dark energy takes over, something bizarre happens: the large-scale structure in the Universe ceases to grow. The objects that were gravitationally bound to one another before dark energy’s takeover will remain bound, but those that were not yet bound by the onset of the dark energy age will never become bound. Instead, they will simply accelerate away from one another, leading lonely existences in the great expanse of nothingness.

    The individual bound structures, like galaxies and groups/clusters of galaxies, will eventually merge to form one giant elliptical galaxy. The existing stars will die; new star formation will slow down to a trickle and then stop; gravitational interactions will eject most of the stars into the intergalactic abyss. Planets will spiral into their parent stars or stellar remnants, owing to decay by gravitational radiation. Even black holes, with extraordinarily long lifetimes, will eventually decay from Hawking radiation.

    In the end, only black dwarf stars and isolated masses too small to ignite nuclear fusion will remain, sparsely populated and disconnected from one another in this empty, ever-expanding cosmos. These final-state corpses will exist even googols of years onward, continuing to persist as dark energy remains the dominant factor in our Universe.

    This last era, of dark energy domination, has already begun. Dark energy became important for the Universe’s expansion 6 billion years ago, and began dominating the Universe’s energy content around the time our Sun and Solar System were being born. The Universe may have six unique stages, but for the entirety of Earth’s history, we’ve already been in the final one. Take a good look at the Universe around us. It will never be this rich — or this easy to access — ever again.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 10:54 am on July 27, 2019 Permalink | Reply
    Tags: "Ask Ethan: Can We Really Get A Universe From Nothing?", , , , , Because dark energy is a property of space itself when the Universe expands the dark energy density must remain constant., , , , Dark Energy, , Galaxies that are gravitationally bound will merge together into groups and clusters while the unbound groups and clusters will accelerate away from one another., , Heisenberg uncertainty principle, Negative gravity?, ,   

    From Ethan Siegel: “Ask Ethan: Can We Really Get A Universe From Nothing?” 

    From Ethan Siegel
    July 27, 2019

    1
    Our entire cosmic history is theoretically well-understood in terms of the frameworks and rules that govern it. It’s only by observationally confirming and revealing various stages in our Universe’s past that must have occurred, like when the first stars and galaxies formed, and how the Universe expanded over time, that we can truly come to understand what makes up our Universe and how it expands and gravitates in a quantitative fashion. The relic signatures imprinted on our Universe from an inflationary state before the hot Big Bang give us a unique way to test our cosmic history, subject to the same fundamental limitations that all frameworks possess. (NICOLE RAGER FULLER / NATIONAL SCIENCE FOUNDATION)

    And does it require the idea of ‘negative gravity’ in order to work?

    The biggest question that we’re even capable of asking, with our present knowledge and understanding of the Universe, is where did everything we can observe come from? If it came from some sort of pre-existing state, we’ll want to know exactly what that state was like and how our Universe came from it. If it emerged out of nothingness, we’d want to know how we went from nothing to the entire Universe, and what if anything caused it. At least, that’s what our Patreon supporter Charles Buchanan wants to know, asking:

    “One concept bothers me. Perhaps you can help. I see it in used many places, but never really explained. “A universe from Nothing” and the concept of negative gravity. As I learned my Newtonian physics, you could put the zero point of the gravitational potential anywhere, only differences mattered. However Newtonian physics never deals with situations where matter is created… Can you help solidify this for me, preferably on [a] conceptual level, maybe with a little calculation detail?”

    Gravitation might seem like a straightforward force, but an incredible number of aspects are anything but intuitive. Let’s take a deeper look.

    2
    Countless scientific tests of Einstein’s general theory of relativity have been performed, subjecting the idea to some of the most stringent constraints ever obtained by humanity. Einstein’s first solution was for the weak-field limit around a single mass, like the Sun; he applied these results to our Solar System with dramatic success. We can view this orbit as Earth (or any planet) being in free-fall around the Sun, traveling in a straight-line path in its own frame of reference. All masses and all sources of energy contribute to the curvature of spacetime. (LIGO SCIENTIFIC COLLABORATION / T. PYLE / CALTECH / MIT)

    MIT /Caltech Advanced aLigo



    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    LSC LIGO Scientific Collaboration


    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2018


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    If you have two point masses located some distance apart in your Universe, they’ll experience an attractive force that compels them to gravitate towards one another. But this attractive force that you perceive, in the context of relativity, comes with two caveats.

    The first caveat is simple and straightforward: these two masses will experience an acceleration towards one another, but whether they wind up moving closer to one another or not is entirely dependent on how the space between them evolves. Unlike in Newtonian gravity, where space is a fixed quantity and only the masses within that space can evolve, everything is changeable in General Relativity. Not only does matter and energy move and accelerate due to gravitation, but the very fabric of space itself can expand, contract, or otherwise flow. All masses still move through space, but space itself is no longer stationary.

    3
    The ‘raisin bread’ model of the expanding Universe, where relative distances increase as the space (dough) expands. The farther away any two raisin are from one another, the greater the observed redshift will be by time the light is received. The redshift-distance relation predicted by the expanding Universe is borne out in observations, and has been consistent with what’s been known going all the way back to the 1920s. (NASA / WMAP SCIENCE TEAM)

    NASA/WMAP 2001 to 2010

    The second caveat is that the two masses you’re considering, even if you’re extremely careful about accounting for what’s in your Universe, are most likely not the only forms of energy around. There are bound to be other masses in the form of normal matter, dark matter, and neutrinos. There’s the presence of radiation, from both electromagnetic and gravitational waves. There’s even dark energy: a type of energy inherent to the fabric of space itself.

    Now, here’s a scenario that might exemplify where your intuition leads you astray: what happens if these masses, for the volume they occupy, have less total energy than the average energy density of the surrounding space?

    4
    The gravitational attraction (blue) of overdense regions and the relative repulsion (red) of the underdense regions, as they act on the Milky Way. Even though gravity is always attractive, there is an average amount of attraction throughout the Universe, and regions with lower energy densities than that will experience (and cause) an effective repulsion with respect to the average. (YEHUDA HOFFMAN, DANIEL POMARÈDE, R. BRENT TULLY, AND HÉLÈNE COURTOIS, NATURE ASTRONOMY 1, 0036 (2017))

    You can imagine three different scenarios:

    1.The first mass has a below-average energy density while the second has an above-average value.
    2.The first mass has an above-average energy density while the second has a below-average value.
    3.Both the first and second masses have a below-average energy density compared to the rest of space.

    In the first two scenarios, the above-average mass will begin growing as it pulls on the matter/energy all around it, while the below-average mass will start shrinking, as it’s less able to hold onto its own mass in the face of its surroundings. These two masses will effectively repel one another; even though gravitation is always attractive, the intervening matter is preferentially attracted to the heavier-than-average mass. This causes the lower-mass object to act like it’s both repelling and being repelled by the heavier-mass object, the same way a balloon held underwater will still be attracted to Earth’s center, but will be forced away from it owing to the (buoyant) effects of the water.

    5
    The Earth’s crust is thinnest over the ocean and thickest over mountains and plateaus, as the principle of buoyancy dictates and as gravitational experiments confirm. Just as a balloon submerged in water will accelerate away from the center of the Earth, a region with below-average energy density will accelerate away from an overdense region, as average-density regions will be more preferentially attracted to the overdense region than the underdense region will. (USGS)
    6

    So what’s going to happen if you have two regions of space with below-average densities, surrounded by regions of just average density? They’ll both shrink, giving up their remaining matter to the denser regions around them. But as far as motions go, they’ll accelerate towards one another, with exactly the same magnitude they’d accelerate at if they were both overdense regions that exceeded the average density by equivalent amounts.

    You might be wondering why it’s important to think about these concerns when talking about a Universe from nothing. After all, if your Universe is full of matter and energy, it’s pretty hard to understand how that’s relevant to making sense of the concept of something coming from nothing. But just as our intuition can lead us astray when thinking about matter and energy on the spacetime playing field of General Relativity, it’s a comparable situation when we think about nothingness.

    7
    A representation of flat, empty space with no matter, energy or curvature of any type. With the exception of small quantum fluctuations, space in an inflationary Universe becomes incredibly flat like this, except in a 3D grid rather than a 2D sheet. Space is stretched flat, and particles are rapidly driven away. (AMBER STUVER / LIVING LIGO)

    You very likely think about nothingness as a philosopher would: the complete absence of everything. Zero matter, zero energy, an absolutely zero value for all the quantum fields in the Universe, etc. You think of space that’s completely flat, with nothing around to cause its curvature anywhere.

    If you think this way, you’re not alone: there are many different ways to conceive of “nothing.” You might even be tempted to take away space, time, and the laws of physics themselves, too. The problem, if you start doing that, is that you lose your ability to predict anything at all. The type of nothingness you’re thinking about, in this context, is what we call unphysical.

    If we want to think about nothing in a physical sense, you have to keep certain things. You need spacetime and the laws of physics, for example; you cannot have a Universe without them.

    8
    A visualization of QCD illustrates how particle/antiparticle pairs pop out of the quantum vacuum for very small amounts of time as a consequence of Heisenberg uncertainty.

    The quantum vacuum is interesting because it demands that empty space itself isn’t so empty, but is filled with all the particles, antiparticles and fields in various states that are demanded by the quantum field theory that describes our Universe. Put this all together, and you find that empty space has a zero-point energy that’s actually greater than zero. (DEREK B. LEINWEBER)

    But here’s the kicker: if you have spacetime and the laws of physics, then by definition you have quantum fields permeating the Universe everywhere you go. You have a fundamental “jitter” to the energy inherent to space, due to the quantum nature of the Universe. (And the Heisenberg uncertainty principle, which is unavoidable.)

    Put these ingredients together — because you can’t have a physically sensible “nothing” without them — and you’ll find that space itself doesn’t have zero energy inherent to it, but energy with a finite, non-zero value. Just as there’s a finite zero-point energy (that’s greater than zero) for an electron bound to an atom, the same is true for space itself. Empty space, even with zero curvature, even devoid of particles and external fields, still has a finite energy density to it.

    9
    The four possible fates of the Universe with only matter, radiation, curvature and a cosmological constant allowed. The top three possibilities are for a Universe whose fate is determined by the balance of matter/radiation with spatial curvature alone; the bottom one includes dark energy. Only the bottom “fate” aligns with the evidence. (E. SIEGEL / BEYOND THE GALAXY)

    From the perspective of quantum field theory, this is conceptualized as the zero-point energy of the quantum vacuum: the lowest-energy state of empty space. In the framework of General Relativity, however, it appears in a different sense: as the value of a cosmological constant, which itself is the energy of empty space, independent of curvature or any other form of energy density.

    Although we do not know how to calculate the value of this energy density from first principles, we can calculate the effects it has on the expanding Universe. As your Universe expands, every form of energy that exists within it contributes to not only how your Universe expands, but how that expansion rate changes over time. From multiple independent lines of evidence — including the Universe’s large-scale structure, the cosmic microwave background, and distant supernovae — we have been able to determine how much energy is inherent to space itself.

    10
    Constraints on dark energy from three independent sources: supernovae, the CMB (cosmic microwave background) and BAO (which is a wiggly feature seen in the correlations of large-scale structure). Note that even without supernovae, we’d need dark energy for certain, and also that there are uncertainties and degeneracies between the amount of dark matter and dark energy that we’d need to accurately describe our Universe. (SUPERNOVA COSMOLOGY PROJECT, AMANULLAH, ET AL., AP.J. (2010))

    This form of energy is what we presently call dark energy, and it’s responsible for the observed accelerated expansion of the Universe. Although it’s been a part of our conceptions of reality for more than two decades now, we don’t fully understand its true nature. All we can say is that when we measure the expansion rate of the Universe, our observations are consistent with dark energy being a cosmological constant with a specific magnitude, and not with any of the alternatives that evolve significantly over cosmic time.

    Because dark energy causes distant galaxies to appear to recede from one another more and more quickly as time goes on — since the space between those galaxies is expanding — it’s often called negative gravity. This is not only highly informal, but incorrect. Gravity is only positive, never negative. But even positive gravity, as we saw earlier, can have effects that look very much like negative repulsion.

    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

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    11
    How energy density changes over time in a Universe dominated by matter (top), radiation (middle), and a cosmological constant (bottom). Note that dark energy doesn’t change in density as the Universe expands, which is why it comes to dominate the Universe at late times. (E. SIEGEL)

    If there were greater amounts of dark energy present within our spatially flat Universe, the expansion rate would be greater. But this is true for all forms of energy in a spatially flat Universe: dark energy is no exception. The only different between dark energy and the more commonly encountered forms of energy, like matter and radiation, is that as the Universe expands, the densities of matter and radiation decrease.

    But because dark energy is a property of space itself, when the Universe expands, the dark energy density must remain constant. As time goes on, galaxies that are gravitationally bound will merge together into groups and clusters, while the unbound groups and clusters will accelerate away from one another. That’s the ultimate fate of the Universe if dark energy is real.

    Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    So why do we say we have a Universe that came from nothing? Because the value of dark energy may have been much higher in the distant past: before the hot Big Bang. A Universe with a very large amount of dark energy in it will behave identically to a Universe undergoing cosmic inflation. In order for inflation to end, that energy has to get converted into matter and radiation. The evidence strongly points to that happening some 13.8 billion years ago.

    When it did, though, a small amount of dark energy remained behind. Why? Because the zero-point energy of the quantum fields in our Universe isn’t zero, but a finite, greater-than-zero value. Our intuition may not be reliable when we consider the physical concepts of nothing and negative/positive gravity, but that’s why we have science. When we do it right, we wind up with physical theories that accurately describe the Universe we measure and observe.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 10:30 am on June 19, 2019 Permalink | Reply
    Tags: "eROSITA – the hunt for Dark Energy begins", , , , , Dark Energy,   

    From DLR German Aerospace Center: “eROSITA – the hunt for Dark Energy begins” 

    DLR Bloc

    From DLR German Aerospace Center

    18 June 2019

    Martin Fleischmann
    German Aerospace Center (DLR)
    Space Administration, Strategy and Communications
    Tel.: +49 228 447-120
    Fax: +49 228 447-386

    Elisabeth Mittelbach
    German Aerospace Center (DLR)
    Communications, Space Administration
    Tel.: +49 228 447-385
    Fax: +49 228 447-386

    Dr Thomas Mernik
    German Aerospace Center (DLR)
    Space Administration, Space Science
    Tel.: +49 228 447-111
    Fax: +49 173 3555497

    1
    On 21 June 2019, the Spektrum-Röntgen-Gamma (SRG) spacecraft with the German X-ray telescope eROSITA will set off for the second Lagrange point.

    2
    With its seven X-ray detectors, the German space telescope will observe the entire sky, search for hot sources and map them.

    3
    eROSITA will help solve the mystery of Dark Energy.

    On 21 June 2019 the Spektrum-Röntgen-Gamma (Spektr-RG / SRG) spacecraft will be launched from the Kazakh steppe, marking the start of an exciting journey. SRG will be carrying the German ‘extended ROentgen Survey with an Imaging Telescope Array’ (eROSITA) X-ray telescope and its Russian ART-XC partner instrument. A Proton rocket will carry the spacecraft from the Baikonur Cosmodrome towards its destination – the second Lagrange point of the Sun-Earth system, L2, which is 1.5 million kilometres from Earth.

    LaGrange Points map. NASA

    In orbit around this equilibrium point, eROSITA will embark upon the largest ever survey of the hot Universe. The space telescope will use its seven X-ray detectors to observe the entire sky and search for and map hot sources such as galaxy clusters, active black holes, supernova remnants, X-ray binaries and neutron stars. “eROSITA’s X-ray ‘eyes’ are the best that have ever been launched as part of a space telescope. Their unique combination of light-collecting area, field-of-view and resolution makes them approximately 20 times more sensitive than the ROSAT telescope that flew to space in the 1990s. ROSAT also incorporated advanced technology that was ‘made in Germany’. With its enhanced capabilities, eROSITA will help researchers gain a better understanding of the structure and development of the Universe, and also contribute towards investigations into the mystery of Dark Energy,” says Walther Pelzer, Executive Board Member for the Space Administration at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), which supported the development of eROSITA at the Max Planck Institute for Extraterrestrial Physics (MPE).

    Dark Energy – a ‘cosmic fuel’ that is accelerating the expansion of the Universe

    The Universe has been expanding continuously since the Big Bang. Until the 1990s, it was thought that this cosmic expansion would slow down and eventually come to a halt. Then, the astrophysicists Saul Perlmutter, Adam Riess and Brian Schmidt observed stellar explosions that were visible from a great distance and always emitted the same amount of light. They measured their distances and could hardly believe their findings. “The Type 1a supernovae observed exhibited lower brightness levels than expected. It was clear that the Universe was not slowing down as it expanded – quite the opposite, in fact. It is gathering speed and its components are being driven further and further apart at an ever-increasing rate,” explains Thomas Mernik, eROSITA Project Manager at the DLR Space Administration. With this discovery, the three researchers turned science upside and were awarded the Nobel Prize in Physics in 2011. Yet Perlmutter, Riess and Schmidt have left us with one crucial question: “What is the ‘cosmic fuel’ that powers the expansion of the Universe? Since no one has yet been able to answer this question, and the ingredients of this catalyst are unknown, it is simply referred to as Dark Energy. eROSITA will now attempt to track down the cause of this acceleration,” explains Mernik.

    Galaxy clusters – a key to Dark Energy

    Very little is known about the Universe. The ingredients that make up four percent of its energy density – ‘normal’ material such as protons and neutrons – is only a very small part of the ‘Universe recipe’. What the other 96 percent is composed of remains a mystery. Today it is believed that 26 percent is Dark Matter. However, the largest share, estimated at 70 percent, is comprised of Dark Energy. To track this down, scientists must observe something unimaginably large and extremely hot: “Galaxy clusters are composed of up to several thousand galaxies that move at different velocities within a common gravitational field. Inside, these strange structures are permeated by a thin, extremely hot gas that can be observed through its X-ray emissions. This is where eROSITA’s X-ray ‘eyes’ come into play. They allow us to observe galaxy clusters and see how they move in the Universe, and above all, how fast they are travelling. We hope that this motion will tell us more about Dark Energy,” explains Thomas Mernik.

    Map of the entire hot Universe – the largest cosmic catalogue

    Scientists are not just interested in the movement patterns of galaxy clusters. They also want to count and map these structures. Up to 10,000 such clusters should be ‘captured’ by eROSITA’s X-ray ‘eyes’ – more than have ever been observed before. In addition, other hot phenomena such as active galactic nuclei, supernova remnants, X-ray binaries and neutron stars will be observed and identified. eROSITA will scan the entire every six months for this purpose and create a deep and detailed X-ray map of the Universe over four years. This will make it possible for eROSITA to produce the largest-ever cosmic catalogue of hot objects and thus improve our scientific understanding of the structure and development of the Universe.

    eROSITA – seven X-ray ‘eyes’ looking into the Universe

    The German telescope consists of two core components – its optics and the associated detectors. The former consists of seven mirror modules aligned in parallel. Each module has a diameter of 36 centimetres and consists of 54 nested mirror shells, whose surface is composed of a paraboloid and a hyperboloid (Wolter-I optics). “The mirror modules collect high-energy photons and focus them onto the CCD X-ray cameras, which were specially developed for eROSITA at our semiconductor laboratory in Garching. These form the second core component of eROSITA and are located at the focus of each of the mirror systems. The highly sensitive cameras are the best of their kind and, together with the mirror modules, form an X-ray telescope featuring an unrivalled combination of light-collecting area and field-of-view,” explains Peter Predehl, eROSITA Principal Investigator at MPE.

    Spektrum-Röntgen-Gamma – a space mission with numerous partners

    Spektrum-Röntgen-Gamma (SRG) is a space mission with numerous partners. On the Russian side, it involves the space agency Roscosmos, the space company Lavochkin and the Space Research Institute of the Russian Academy of Sciences (IKI) . The German eROSITA X-ray telescope was developed and built by the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, in collaboration with the Leibniz Institute of Astrophysics in Potsdam (AIP) and the universities of Erlangen-Nuremberg, Hamburg and Tübingen with the support of the DLR Space Administration. Furthermore, the Universities of Munich and Bonn will participate in analysing eROSITA data. The partner institutes involved in the eROSITA telescope have created software for data analysis, mission planning and simulations, as well as components of the hardware. However the main responsibility lay with MPE. “As a rule, an instrument as complex as eROSITA can only be implemented by a major institute with the help of an industrial Prime Contractor. However, together with MPE, we took a different path and let the institute conduct the development work on its own,” says Thomas Mernik. The project management, product assurance and system design were key tasks performed by MPE itself. It also delegated other tasks to industry, such as the manufacturing of the mirrors, the structure, the thermal insulation, mechanical precision parts, electronics boards and much more. “Since eROSITA is about to embark on its journey into space, in retrospect we can say that this approach was very successful and sensible,” says Mernik.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    DLR Center

    DLR is the national aeronautics and space research centre of the Federal Republic of Germany. Its extensive research and development work in aeronautics, space, energy, transport and security is integrated into national and international cooperative ventures. In addition to its own research, as Germany’s space agency, DLR has been given responsibility by the federal government for the planning and implementation of the German space programme. DLR is also the umbrella organisation for the nation’s largest project management agency.

    DLR has approximately 8000 employees at 16 locations in Germany: Cologne (headquarters), Augsburg, Berlin, Bonn, Braunschweig, Bremen, Goettingen, Hamburg, Juelich, Lampoldshausen, Neustrelitz, Oberpfaffenhofen, Stade, Stuttgart, Trauen, and Weilheim. DLR also has offices in Brussels, Paris, Tokyo and Washington D.C.

     
  • richardmitnick 2:11 pm on June 11, 2019 Permalink | Reply
    Tags: , Dark Energy, , , , Future Circular Collider (FCC), If we don’t push the frontiers of physics we’ll never learn what lies beyond our current understanding., , Lepton collider, New accelerators ecplored, , , , Proton collider,   

    From Ethan Siegel: “Does Particle Physics Have A Future On Earth?” 

    From Ethan Siegel
    Jun 11. 2019

    1
    The inside of the LHC, where protons pass each other at 299,792,455 m/s, just 3 m/s shy of the speed of light. As powerful as the LHC is, the cancelled SSC could have been three times as powerful, and may have revealed secrets of nature that are inaccessible at the LHC. (CERN)

    If we don’t push the frontiers of physics, we’ll never learn what lies beyond our current understanding.

    At a fundamental level, what is our Universe made of? This question has driven physics forward for centuries. Even with all the advances we’ve made, we still don’t know it all. While the Large Hadron Collider discovered the Higgs boson and completed the Standard Model earlier this decade, the full suite of the particles we know of only make up 5% of the total energy in the Universe.

    CERN CMS Higgs Event


    CERN ATLAS Higgs Event

    Standard Model of Particle Physics

    We don’t know what dark matter is, but the indirect evidence for it is overwhelming.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    Same deal with dark energy.

    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

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    Or questions like why the fundamental particles have the masses they do, or why neutrinos aren’t massless, or why our Universe is made of matter and not antimatter. Our current tools and searches have not answered these great existential puzzles of modern physics. Particle physics now faces an incredible dilemma: try harder, or give up.

    2
    The Standard Model of particle physics accounts for three of the four forces (excepting gravity), the full suite of discovered particles, and all of their interactions. Whether there are additional particles and/or interactions that are discoverable with colliders we can build on Earth is a debatable subject, but one we’ll only know the answer to if we explore past the known energy frontier. (CONTEMPORARY PHYSICS EDUCATION PROJECT / DOE / NSF / LBNL)

    The particles and interactions that we know of are all governed by the Standard Model of particle physics, plus gravity, dark matter, and dark energy. In particle physics experiments, however, it’s the Standard Model alone that matters. The six quarks, charged leptons and neutrinos, gluons, photon, gauge bosons and Higgs boson are all that it predicts, and each particle has been not only discovered, but their properties have been measured.

    As a result, the Standard Model is perhaps a victim of its own success. The masses, spins, lifetimes, interaction strengths, and decay ratios of every particle and antiparticle have all been measured, and they agree with the Standard Model’s predictions at every turn. There are enormous puzzles about our Universe, and particle physics has given us no experimental indications of where or how they might be solved.

    3
    The particles and antiparticles of the Standard Model have now all been directly detected, with the last holdout, the Higgs Boson, falling at the LHC earlier this decade. All of these particles can be created at LHC energies, and the masses of the particles lead to fundamental constants that are absolutely necessary to describe them fully. These particles can be well-described by the physics of the quantum field theories underlying the Standard Model, but they do not describe everything, like dark matter. (E. SIEGEL / BEYOND THE GALAXY)

    It might be tempting, therefore, to presume that building a superior particle collider would be a fruitless endeavor. Indeed, this could be the case. The Standard Model of particle physics has explicit predictions for the couplings that occur between particles. While there are a number of parameters that remain poorly determined at present, it’s conceivable that there are no new particles that a next-generation collider could reveal.

    The heaviest Standard Model particle is the top quark, which takes roughly ~180 GeV of energy to create. While the Large Hadron Collider can reach energies of 14 TeV (about 80 times the energy needed to create a top quark), there might not be any new particles present to find unless we reach energies in excess of 1,000,000 times as great. This is the great fear of many: the possible existence of a so-called “energy desert” extending for many orders of magnitude.

    4
    There is certainly new physics beyond the Standard Model, but it might not show up until energies far, far greater than what a terrestrial collider could ever reach. Still, whether this scenario is true or not, the only way we’ll know is to look. In the meantime, properties of the known particles can be better explored with a future collider than any other tool. The LHC has failed to reveal, thus far, anything beyond the known particles of the Standard Model. (UNIVERSE-REVIEW.CA)

    But it’s also possible that there is new physics present at a modest scale beyond where we’ve presently probed. There are many theoretical extensions to the Standard Model that are quite generic, where deviations from the Standard Model’s predictions can be detected by a next-generation collider.

    If we want to know what the truth about our Universe is, we have to look, and that means pushing the present frontiers of particle physics into uncharted territory. Right now, the community is debating between multiple approaches, with each one having its pros and cons. The nightmare scenario, however, isn’t that we’ll look and won’t find anything. It’s that infighting and a lack of unity will doom experimental physics forever, and that we won’t get a next-generation collider at all.

    5
    A hypothetical new accelerator, either a long linear one or one inhabiting a large tunnel beneath the Earth, could dwarf the sensitivity to new particles that prior and current colliders can achieve. Even at that, there’s no guarantee we’ll find anything new, but we’re certain to find nothing new if we fail to try. (ILC COLLABORATION)

    When it comes to deciding what collider to build next, there are two generic approaches: a lepton collider (where electrons and positrons are accelerated and collided), and a proton collider (where protons are accelerated and collided). The lepton colliders have the advantages of:

    the fact that leptons are point particles, rather than composite particles,
    100% of the energy from electrons colliding with positrons can be converted into energy for new particles,
    the signal is clean and much easier to extracts,
    and the energy is controllable, meaning we can choose to tune the energy to a specific value and maximize the chance of creating a specific particle.

    Lepton colliders, in general, are great for precision studies, and we haven’t had a cutting-edge one since LEP was operational nearly 20 years ago.

    CERN LEP Collider

    5
    At various center-of-mass energies in electron/positron (lepton) colliders, various Higgs production mechanisms can be reached at explicit energies. While a circular collider can achieve much greater collision rates and production rates of W, Z, H, and t particles, a long-enough linear collider can conceivably reach higher energies, enabling us to probe Higgs production mechanisms that a circular collider cannot reach. This is the main advantage that linear lepton colliders possess; if they are low-energy only (like the proposed ILC), there is no reason not to go circular. (H. ABRAMOWICZ ET AL., EUR. PHYS. J. C 77, 475 (2017))

    It’s very unlikely, unless nature is extremely kind, that a lepton collider will directly discover a new particle, but it may be the best bet for indirectly discovering evidence of particles beyond the Standard Model. We’ve already discovered particles like the W and Z bosons, the Higgs boson, and the top quark, but a lepton collider could both produce them in great abundances and through a variety of channels.

    The more events of interest we create, the more deeply we can probe the Standard Model. The Large Hadron Collider, for example, will be able to tell whether the Higgs behaves consistently with the Standard Model down to about the 1% level. In a wide series of extensions to the Standard Model, ~0.1% deviations are expected, and the right future lepton collider will get you the best physics constraints possible.

    6
    The observed Higgs decay channels vs. the Standard Model agreement, with the latest data from ATLAS and CMS included. The agreement is astounding, and yet frustrating at the same time. By the 2030s, the LHC will have approximately 50 times as much data, but the precisions on many decay channels will still only be known to a few percent. A future collider could increase that precision by multiple orders of magnitude, revealing the existence of potential new particles.(ANDRÉ DAVID, VIA TWITTER)

    These precision studies could be incredibly sensitive to the presence of particles or interactions we haven’t yet discovered. When we create a particle, it has a certain set of branching ratios, or probabilities that it will decay in a variety of ways. The Standard Model makes explicit predictions for those ratios, so if we create a million, or a billion, or a trillion such particles, we can probe those branching ratios to unprecedented precisions.

    If you want better physics constraints, you need more data and better data. It isn’t just the technical considerations that should determine which collider comes next, but also where and how you can get the best personnel, the best infrastructure and support, and where you can build a (or take advantage of an already-existing) strong experimental and theoretical physics community.

    7
    The idea of a linear lepton collider has been bandied about in the particle physics community as the ideal machine to explore post-LHC physics for many decades, but that was under the assumption that the LHC would find a new particle other than the Higgs. If we want to do precision testing of Standard Model particles to indirectly search for new physics, a linear collider may be an inferior option to a circular lepton collider. (REY HORI/KEK)

    There are two general classes proposals for a lepton collider: a circular collider and a linear collider. Linear colliders are simple: accelerate your particles in a straight line and collide them together in the center. With ideal accelerator technology, a linear collider 11 km long could reach energies of 380 GeV: enough to produce the W, Z, Higgs, or top in great abundance. With a 29 km linear collider, you could reach energies of 1.5 TeV, and with a 50 km collider, 3 TeV, although costs rise tremendously to accompany longer lengths.

    Linear colliders are slightly less expensive than circular colliders for the same energy, because you can dig a smaller tunnel to reach the same energies, and they don’t suffer energy losses due to synchrotron radiation, enabling them to reach potentially higher energies. However, the circular colliders offer an enormous advantage: they can produce much greater numbers of particles and collisions.

    Future Circular Collider (FCC)Larger LHC


    The Future Circular Collider is a proposal to build, for the 2030s, a successor to the LHC with a circumference of up to 100 km: nearly four times the size of the present underground tunnels. This will enable, with current magnet technology, the creation of a lepton collider that can produce ~1⁰⁴ times the number of W, Z, H, and t particles that have been produced by prior and current colliders. (CERN / FCC STUDY)

    While a linear collider might be able to produce 10 to 100 times as many collisions as a prior-generation lepton collider like LEP (dependent on energies), a circular version can surpass that easily: producing 10,000 times as many collisions at the energies required to create the Z boson.

    Although circular colliders have substantially higher event rates than linear colliders at the relevant energies that produce Higgs particles as well, they begin to lose their advantage at energies required to produce top quarks, and cannot reach beyond that at all, where linear colliders become dominant.

    Because all of the decay and production processes that occur in these heavy particles scales as either the number of collisions or the square root of the number of collisions, a circular collider has the potential to probe physics with many times the sensitivity of a linear collider.

    7
    A number of the various lepton colliders, with their luminosity (a measure of the collision rate and the number of detections one can make) as a function of center-of-mass collision energy. Note that the red line, which is a circular collider option, offers many more collisions than the linear version, but gets less superior as energy increases. Beyond about 380 GeV, circular colliders cannot reach, and a linear collider like CLIC is the far superior option. (GRANADA STRATEGY MEETING SUMMARY SLIDES / LUCIE LINSSEN (PRIVATE COMMUNICATION))

    The proposed FCC-ee, or the lepton stage of the Future Circular Collider, would realistically discover indirect evidence for any new particles that coupled to the W, Z, Higgs, or top quark with masses up to 70 TeV: five times the maximum energy of the Large Hadron Collider.

    The flipside to a lepton collider is a proton collider, which — at these high energies — is essentially a gluon-gluon collider. This cannot be linear; it must be circular.

    8
    The scale of the proposed Future Circular Collider (FCC), compared with the LHC presently at CERN and the Tevatron, formerly operational at Fermilab. The Future Circular Collider is perhaps the most ambitious proposal for a next-generation collider to date, including both lepton and proton options as various phases of its proposed scientific programme. (PCHARITO / WIKIMEDIA COMMONS)

    There is really only one suitable site for this: CERN, since it not only needs a new, enormous tunnel, but all the infrastructure of the prior stages, which only exist at CERN. (They could be built elsewhere, but the cost would be more expensive than a site where the infrastructure like the LHC and earlier colliders like SPS already exist.)

    The Super Proton Synchrotron (SPS), CERN’s second-largest accelerator.

    Just as the LHC is presently occupying the tunnel previously occupied by LEP, a circular lepton collider could be superseded by a next-generation circular proton collider, such as the proposed FCC-pp. However, you cannot run both an exploratory proton collider and a precision lepton collider simultaneously; you must decommission one to finish the other.

    9
    The CMS detector at CERN, one of the two most powerful particle detectors ever assembled. Every 25 nanoseconds, on average, a new particle bunch collides at the center-point of this detector. A next-generation detector, whether for a lepton or proton collider, may be able to record even more data, faster, and with higher-precision than the CMS or ATLAS detectors can at present. (CERN)

    It’s very important to make the right decision, as we do not know what secrets nature holds beyond the already-explored frontiers. Going to higher energies unlocks the potential for new direct discoveries, while going to higher precisions and greater statistics could provide even stronger indirect evidence for the existence of new physics.

    The first-stage linear colliders are going to cost between 5 and 7 billion dollars, including the tunnel, while a proton collider of four times the LHC’s radius, with magnets twice as strong, 10 times the collision rate and next-generation computing and cryogenics might cost a total of up to $22 billion, offering as big a leap over the LHC as the LHC was over the Tevatron. Some money could be saved if we build the circular lepton and proton colliders one after the other in the same tunnel, which would essentially provide a future for experimental particle physics after the LHC is done running at the end of the 2030s.

    10
    The Standard Model particles and their supersymmetric counterparts. Slightly under 50% of these particles have been discovered, and just over 50% have never showed a trace that they exist. Supersymmetry is an idea that hopes to improve on the Standard Model, but it has yet to make successful predictions about the Universe in attempting to supplant the prevailing theory. However, new colliders are not being proposed to find supersymmetry or dark matter, but to perform generic searches. Regardless of what they’ll find, we’ll learn something new about the Universe itself. (CLAIRE DAVID / CERN)

    The most important thing to remember in all of this is that we aren’t simply continuing to look for supersymmetry, dark matter, or any particular extension of the Standard Model. We have a slew of problems and puzzles that indicate that there must be new physics beyond what we currently understand, and our scientific curiosity compels us to look. In choosing what machine to build, it’s vital to choose the most performant machine: the ones with the highest numbers of collisions at the energies we’re interested in probing.

    Regardless of which specific projects the community chooses, there will be trade-offs. A linear lepton collider can always reach higher energies than a circular one, while a circular one can always create more collisions and go to higher precisions. It can gather just as much data in a tenth the time, and probe for more subtle effects, at the cost of a lower energy reach.

    Will it be successful? Regardless of what we find, that answer is unequivocally yes. In experimental physics, success does not equate to finding something, as some might erroneously believe. Instead, success means knowing something, post-experiment, that you did not know before you did the experiment. To push beyond the presently known frontiers, we’d ideally want both a lepton and a proton collider, at the highest energies and collision rates we can achieve.

    There is no doubt that new technologies and spinoffs will come from whichever collider or colliders come next, but that’s not why we do it. We are after the deepest secrets of nature, the ones that will remain elusive even after the Large Hadron Collider finishes. We have the technical capabilities, the personnel, and the expertise to build it right at our fingertips. All we need is the political and financial will, as a civilization, to seek the ultimate truths about nature.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 9:12 am on May 12, 2019 Permalink | Reply
    Tags: , , , , Dark Energy, , Dark nature is observable only indirectly by its effects   

    From COSMOS Magazine: “Multiple measurements close in on dark energy” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    06 May 2019
    Andrew Masterson

    Cerro Tololo Inter-American Observatory, located on Cerro Tololo in the Coquimbo Region of northern Chile, Altitude 2,207 m (7,241 ft)

    An extensive analysis of four different phenomena within the universe points the way to understanding the nature of dark energy, a collaboration between more than 100 scientists reveals.

    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

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    Dark energy – the force that propels the acceleration of the expanding universe – is a mysterious thing. It’s nature, write telescope scientist Timothy Abbott from the Cerro Tololo Inter-American Observatory, in Chile, and colleagues, “is unknown, and understanding its properties and origin is one of the principal challenges in modern physics”.

    Indeed, there is a lot at stake. Current measurements indicate that dark energy can be smoothly incorporated into the theory of general relativity as a cosmological constant; but, the researchers note, those measurements are far from precise and incorporate a wide range of potential variations.

    “Any deviation from this interpretation in space or time would constitute a landmark discovery in fundamental physics,” they note.

    The heart of the problem, of course, is that dark nature is observable only indirectly, by its effects.

    These fall into two categories. First, it deforms galactic architectures through accelerating the expansion of the universe. Second, it suppresses growth in some parts of the cosmic structure.

    However, it is not the only force that can produce such results, and the danger thus always exists that what is assumed to be evidence of dark matter activity may in fact be something else altogether.

    Current approaches to measuring dark matter are problematic. All of them begin with the cosmic microwave background (CMB), the relic radiation that fills space, generated just 400,000 years after the Big Bang.

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    At that point in the history of the universe the influence of dark matter was minimal. It increased significantly as spacetime expanded ever more and ever faster.

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

    The second pillar for measuring it, thus, comprises observations of “low-redshift” phenomena – wavelengths stretched over vast distances, allowing calculations of conditions within the universe the past several billion years.

    Red shift and wave length shift-The Earliest Stars And Galaxies In The Universe Science at ESA

    Combining the two measurements and then extrapolating forwards to the present day, Abbott and colleagues note, “can be a powerful test of our models, but it requires precise, independent constraints from low-redshift experiments”.

    It follows, then, that any increase in the precision of low-redshift measurements will also increase the precision of dark energy calculations, reducing (or perhaps increasing) the chances that a previously undiscovered physics is in play in the universe.

    The researchers approach this challenge by invoking a combination of multiple observational probes for low-redshift phenomena – namely, those measuring Type Ia supernova light curves, fluctuations in the density of visible (or “baryonic”) matter, weak gravitational lensing, and galaxy clustering.

    To do this, they use the results of the Dark Energy Survey (DES), a collaboration of research institutions in the US, South America and Europe that studies observations made by the Victor M Blanco telescope in Chile, which is fitted with specialised instruments for dark energy detection.

    Presenting the first tranche of results from the survey, Abbott and colleagues reveal progress towards constraining the nature of dark energy.

    The DES findings, they report, absolutely – and independent of CMB-based research – rule out a universe in which dark energy doesn’t exist. They also report that the results suggest the universe is spatially flat, and derive a tighter constraint on the density of baryon matter.

    These results, they suggest, constrain the state of “of dark energy and its energy density in the Universe” … “to a precision that is almost a factor of three better than the 7 previous best single-experiment result from the CMB”.

    Further planned DES surveys, they conclude, will likely sharpen up knowledge of the impact of dark energy in the universe by orders of magnitude.

    The research is published in the journal Physical Review Letters.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 3:43 pm on May 1, 2019 Permalink | Reply
    Tags: , , , , Dark Energy   

    From “Physics”: “Dark Energy Faces Multiple Probes” 

    Physics LogoAbout Physics

    Physics Logo 2

    From “Physics”

    May 1, 2019
    Nikhil Padmanabhan
    Department of Physics and Department of Astronomy
    Yale University

    The Dark Energy Survey has combined its analysis of four cosmological observables to constrain the properties of dark energy—paving the way for cosmological surveys that will run in the next decade.

    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

    1
    Figure 1: Area of the sky observed by the Dark Energy Survey in its 5-year mission. The different colors indicate different observation runs. SV: preliminary science verification run; Y1: year 1; Y2: year 2; SN fields: areas containing the supernovae used as standard candles to monitor the Universe’s expansion.

    One of the top goals in cosmology today is understanding the dark energy that is responsible for the accelerated expansion of the Universe. Is the dark energy consistent with the cosmological constant of general relativity—representing a constant energy density filling space homogenously? Or can we find deviations from general relativity on cosmological scales that suggest a more complex nature for gravity? Questions like these motivate the current and next generations of surveys that aim to map out ever larger volumes of the Universe, using a wide variety of probes to constrain the properties of dark energy. The Dark Energy Survey (DES) has now derived such constraints from the combined analysis of four canonical observables related to dark energy: supernovae, baryon acoustic oscillations, gravitational lensing, and galaxy clustering [1]. The resulting bounds confirm what we knew from previous studies, which focused on single probes. But the results indicate that this multiprobe approach could allow surveys in the 2020s to improve such constraints by orders of magnitude, possibly bringing us close to solving the dark energy puzzle.

    Measurements of dark energy traditionally come in two “flavors.” The first measures the geometric expansion of the Universe. It includes observations of supernovae and of baryon acoustic oscillations (BAO). Type Ia supernovae can be used as “standard candles”—their known brightness allows astronomers to estimate their distance. In the 1990s, measurements of the recession speed (or redshift) of supernovae as a function of distance led to the discovery that the expansion of the Universe was accelerating, upsetting predictions based on models of a matter-dominated Universe [2]. BAO are also related to spatial distances, but they serve instead as “standard rulers” that can calibrate cosmic lengths. BAO are fluctuations in the density of matter caused by acoustic waves in the primordial photon-baryon plasma of the early Universe. The length of the BAO standard rulers can be estimated from cosmic microwave background (CMB) measurements. By observing the angular size of the BAO rulers at different times, scientists can directly measure the geometric background expansion of the Universe.

    The second flavor of measurements focuses on dark energy’s effect on the growth rate of cosmic structures, both visible and dark. The accelerated expansion causes these structures to grow slower, as gravity has less time to pull in matter around over-dense regions. The growth suppression can be characterized by observing the distribution of matter. The DES traces the matter distribution through weak lensing—measurements of subtle, coherent distortions of the shapes of background galaxies due to the gravitational lensing of foreground matter. From such distortions, the distribution of foreground matter (which is mostly dark matter) can be inferred. The small magnitude of the weak-lensing effect makes it challenging to measure and susceptible to systematic observational errors, but a number of surveys, including the DES [3], were able to produce maps of the matter distribution using weak lensing.

    Another approach to measure structure-growth suppression is to trace out the matter distribution by mapping out the positions of visible galaxies. Measuring distances to galaxies requires determining their redshifts through spectroscopy. While the DES doesn’t have high-resolution spectroscopy capabilities, it partially addresses this challenge by imaging the sky through five spectral filters, acquiring low-resolution spectra that provide approximate measurements of distances to galaxies. These distance errors blur out the three-dimensional structure, but the resulting maps are still a powerful probe of gravitational structure formation. While these galaxy maps are less noisy than the weak-lensing maps, they are limited because we don’t know exactly how dark matter is distributed with respect to visible galaxies. However, the DES Collaboration has developed techniques based on correlating weak-lensing data with visible galaxy distributions, which allows it to use the higher signal-to-noise galaxy maps for cosmology.

    Imaging a large area of the Southern Sky (Fig. 1) with the 4-m Victor M. Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile, the DES Collaboration has, for the first time, combined all four dark energy probes in a single analysis. The primary results of this work are independent constraints on the cosmological densities of both dark matter and dark energy (Fig 2). The DES Collaboration also constrains the dark energy equation of state parameter ( w). As Fig. 2 shows, these constraints are not yet competitive with the best constraints derived from other experiments that combine galaxy surveys with CMB data. However, demonstrating the feasibility of a multiprobe approach within a single survey is, in my view, the most important aspect of the work, as it has several advantages over single-probe surveys. First, since all the probes derive from a single survey, calibrations and systematic errors can be consistently controlled across the multiple probes—a harder task for studies that compile data from separate experiments. Second, the Collaboration can uniformly apply the same blinding strategy—an analysis approach in which information is withheld from the researchers carrying out the analysis to reduce observer bias. Finally, the simultaneous characterization of the four probes allows the survey to carry out the cross-correlation analyses described above. While all of the above is, in principle, possible using separate experiments, in practice it is extremely challenging. What’s more, the richness of the data from a multiprobe analysis may inspire novel tests of gravity and dark energy that hadn’t been previously thought about.

    3
    Figure 2: Constraints on dark energy density (ΩΛ) and on matter density (Ωm). Gray contours are constraints from DES data on weak gravitational lensing, large-scale structure, supernovae, and BAO. Green contours are the best available constraints…Y. Guo et al., Phys. Rev. Lett. (2019)

    The results of the DES multiprobe analysis bode very well for the next decade of dark energy research. In the short term, we can expect the DES Collaboration to significantly improve on its constraints. The data analyzed in this work represent only a fraction of the overall data that the DES has already taken. The final dataset will have three times more data for the weak-lensing and galaxy-clustering measurements and include 10 times more supernovae. Statistically, this should yield a factor of 2–4 improvement in the constraints presented here. As constraints get tighter, tensions among different observables could potentially signal cracks in existing cosmological models. There are already intriguing disagreements between local measurements of the Hubble constant compared with its value inferred by CMB and BAO [4], as well as hints of disagreements on the amount of structure revealed by CMB and weak lensing [5]. The full DES analysis may help resolve these discrepancies, or possibly—and that would be even more exciting—exacerbate them.

    In the longer term, we can look forward to results from a number of similarly powerful ongoing surveys, and from even larger surveys planned over the next decade. These include photometric surveys like the DES (such as the Kilo-Degree Survey, the Hyper Suprime-Cam Survey, and the Large Synoptic Survey Telescope), spectroscopic surveys (the Extended Baryon Oscillation Spectroscopic Survey and surveys planned with the 4-m Multi-Object Spectroscopic Telescope and the Dark Energy Spectroscopic Instrument), two satellite missions that will combine both photometric and spectroscopic observations (the Euclid telescope and the Wide Field Infrared Survey Telescope), CMB measurements (the Simons Observatory and the Stage-4 CMB experiment), and surveys that use newer probes like the 21-cm hydrogen line and gravitational waves. The breadth of these programs ensures that the DES measurements are just the beginning of an exciting exploration of one of the most intriguing cosmological questions.

    5
    KiDS, the Kilo-Degree Survey, is a large optical imaging survey in the Southern sky, designed to tackle some of the most fundamental questions of cosmology and galaxy formation of today. Using the VLT Survey Telescope (VST), located at the ESO Paranal Observatory, KiDS will map 1500 square degrees of the night sky in four broad-band filters (u, g, r, i).

    NAOJ Subaru Hyper Suprime-Cam

    LSST


    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.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    LBNL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018


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

    BOSS Spectrograph – SDSS-III

    ESA/Euclid spacecraft

    NASA/WFIRST

    This research is published in Physical Review Letters

    References

    T. M. C. Abbott et al., “Cosmological constraints from multiple probes in the Dark Energy Survey,” Phys. Rev. Lett. 122, 171301 (2019).
    A. G. Riess et al., “Observational evidence from supernovae for an accelerating universe and a cosmological constant,” Astron. J. 116, 1009 (1998); S. Perlmutter et al., “Discovery of a supernova explosion at half the age of the Universe,” Nature 391, 51 (1998); “Erratum: Discovery of a supernova explosion at half the age of the Universe,” 392, 311 (1998).
    M. A. Troxel et al., “Dark Energy Survey Year 1 results: Cosmological constraints from cosmic shear,” Phys. Rev. D 98 (2018).
    Wendy L. Freedman, “Cosmology at at crossroads: Tension with the Hubble Constant,” arXiv:1706.02739.
    H. Hildebrandt et al., “KiDS-450: cosmological parameter constraints from tomographic weak gravitational lensing,” Mon. Not. R. Astron. Soc. 465, 1454 (2016); E. van Uitert et al., “KiDS+GAMA: cosmology constraints from a joint analysis of cosmic shear, galaxy–galaxy lensing, and angular clustering,” 476, 4662 (2018); S. Joudaki et al., “KiDS-450 + 2dFLenS: Cosmological parameter constraints from weak gravitational lensing tomography and overlapping redshift-space galaxy clustering,” 474, 4894 (2017); C. Hikage et al., “Cosmology from cosmic shear power spectra with Subaru Hyper Suprime-Cam first-year data,” Publ. Astron. Soc. Jpn. 71, 43 (2019); C. Chang et al., “A unified analysis of four cosmic shear surveys,” Mon. Not. R. Astron. Soc. 482, 3696 (2018).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 9:22 am on April 8, 2019 Permalink | Reply
    Tags: , and the Fate of Our Universe", , , , , Dark Energy, ,   

    From AAS NOVA: “Supernovae, Dark Energy, and the Fate of Our Universe” 

    AASNOVA

    From AAS NOVA

    5 April 2019
    Susanna Kohler

    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

    What’s the eventual fate of our universe? Is spacetime destined to continue to expand forever? Will it fly apart, tearing even atoms into bits? Or will it crunch back in on itself? New results from Dark Energy Survey supernovae address these and other questions.

    Uncertain Expansion

    1
    The evolution of the scale of our universe. Measurements suggest that the universe is currently expanding, but does dark energy behaves like a cosmological constant, resulting in continued accelerating expansion like now? Or might we instead be headed for a Big Rip or Big Crunch? [NASA/CXC/M. Weiss]

    At present, the fabric of our universe is expanding — and not only that, but the its expansion is accelerating. To explain this phenomenon, we invoke what’s known as dark energy — an unknown form of energy that exists everywhere and exerts a negative pressure, driving the expansion.

    Since this idea was first proposed, we’ve conducted decades of research to better understand what dark energy is, how much of it there is, and how it influences our universe.

    In particular, dark energy’s still-uncertain equation of state determines the universe’s ultimate fate. If the density of dark energy is constant in time, our universe will continue its current accelerating expansion indefinitely. If the density increases in time, the universe will end in the Big Rip — space will expand at an ever-increasing acceleration rate until even atoms fly apart. And if the density decreases in time, the universe will recollapse in the Big Crunch, ending effectively in a reverse Big Bang.

    Which of these scenarios is correct? We’re not sure yet. But there’s a project dedicated to finding out: the Dark Energy Survey (DES).

    The Hunt for Supernovae

    DES was conducted with the Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile. After six years taking data, the survey officially wrapped up observations this past January.

    One of DES’s several missions was to make detailed measurements of thousands of supernovae. Type Ia supernovae explode with a prescribed absolute brightness, allowing us to determine their distance from observations. DES’s precise measurements of Type Ia supernovae allow us to calculate the expansion of the space between us and the supernovae, probing the properties of dark energy.

    Though DES scientists are still in the process of analyzing the tens of terabytes of data generated by the project, they recently released results from the first three years of data — including the first DES cosmology results based on supernovae.

    Refined Measurements

    2
    Constraints on the dark energy equation of state w from the DES supernova survey. Combining this data with constraints from the cosmic microwave background radiation suggest an equation of state consistent with a constant density of dark energy (w = –1). [Abbott et al. 2019]

    Using a sample of 207 spectroscopically confirmed DES supernovae and 122 low-redshift supernovae from the literature, the authors estimate the matter density of a flat universe to be Ωm = 0.321 ± 0.018. This means that only ~32% of the universe’s energy density is matter (the majority of which is dark matter); the remaining ~68% is primarily dark energy.

    From their observations, the DES team is also able to provide an estimate for the dark-energy equation of state w, finding that w = –0.978 ± 0.059. This result is consistent with a constant density of dark energy (w = –1), which would mean that our universe will continue to expand with its current acceleration indefinitely.

    These results are exciting, but they use only ~10% of the supernovae DES discovered over the span of its 5-year survey. This means that we can expect even further refinements to these measurements in the future, as the DES collaboration analyzes the remaining data!

    Citation

    “First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: Constraints on Cosmological Parameters,” T. M. C. Abbott et al 2019 ApJL 872 L30.
    https://iopscience.iop.org/article/10.3847/2041-8213/ab04fa/meta

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

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    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

     
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