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  • richardmitnick 4:29 pm on October 15, 2017 Permalink | Reply
    Tags: , CMB - Cosmic Microwave Background, , , , ,   

    From Goddard: “NASA’s James Webb Space Telescope and the Big Bang: A Short Q&A with Nobel Laureate Dr. John Mather” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    Oct. 11, 2017
    Maggie Masetti
    NASA’s Goddard Space Flight Center

    1
    Dr. John Mather, a Nobel laureate and the senior project scientist for NASA’s James Webb Space Telescope. Credits: NASA/Chris Gunn

    Q: What is the Big Bang?

    A: The Big Bang is a really misleading name for the expanding universe that we see. We see an infinite universe with distant galaxies all rushing away from each other.

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

    The name Big Bang conveys the idea of a firecracker exploding at a time and a place — with a center. The universe doesn’t have a center, at least not one we can find. The Big Bang happened everywhere at once and was a process happening in time, not a point in time. We know this because 1) we see galaxies rushing away from each other, not from a central point; 2) we see the heat that was left over from early times, and that heat uniformly fills the universe; and 3) we can calculate and imagine what the universe was like when the parts were much closer together, and the calculations match everything we can see.

    Q: Can we see the Big Bang?

    A: No, the Big Bang itself is not something we can see.

    Q: What can we see?

    A: We can see the heat radiation that was there when the universe was young. We see this heat as it was about 380,000 years after the expansion of the universe began 13.8 billion years ago (which is what we refer to as the Big Bang). This heat covers the entire sky and fills the universe. (In fact it still does.) We were able to map it with satellites we (NASA and ESA) built called the Cosmic Background Explorer (COBE), the Wilkinson Microwave Anisotropy Probe (WMAP), and Planck. The universe at this point was extremely smooth, with only tiny ripples in temperature.

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA

    NASA/COBE

    1
    All-sky image of the infant universe, created from nine years of data from the Wilkinson Microwave Anisotropy Probe (WMAP).
    Credits: NASA/WMAP Science Team

    NASA/WMAP

    CMB per ESA/Planck


    ESA/Planck

    Q: I heard the James Webb Space Telescope will see back further than ever before. What will Webb see?

    NASA/ESA/CSA Webb Telescope annotated

    A: COBE, WMAP, and Planck all saw further back than Webb, though it’s true that Webb will see farther back than Hubble.

    NASA/ESA Hubble Telescope

    Webb was designed not to see the beginnings of the universe, but to see a period of the universe’s history that we have not seen yet.

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

    Specifically, we want to see the first objects that formed as the universe cooled down after the Big Bang. That time period is perhaps hundreds of millions of years later than the one COBE, WMAP, and Planck were built to see. We think that the tiny ripples of temperature they observed were the seeds that eventually grew into galaxies. We don’t know exactly when the universe made the first stars and galaxies — or how for that matter. That is what we are building Webb to help answer.

    Q: Why can’t Hubble see the first stars and galaxies forming?

    A: The only way we can see back to the time when these objects were forming is to look very far away. Hubble isn’t big enough or cold enough to see the faint heat signals of these objects that are so far away.

    Q: Why do we want to see the first stars and galaxies forming?

    A: The chemical elements of life were first produced in the first generation of stars after the Big Bang. We are here today because of them — and we want to better understand how that came to be! We have ideas, we have predictions, but we don’t know. One way or another the first stars must have influenced our own history, beginning with stirring up everything and producing the other chemical elements besides hydrogen and helium. So if we really want to know where our atoms came from, and how the little planet Earth came to be capable of supporting life, we need to measure what happened at the beginning.

    Dr. John Mather is the senior project scientist for the James Webb Space Telescope. Dr. Mather shares the 2006 Nobel Prize for Physics with George F. Smoot of the University of California for their work using the COBE satellite to measure the heat radiation from the Big Bang.

    The James Webb Space Telescope, the scientific complement to NASA’s Hubble Space Telescope, will be the premier space observatory of the next decade. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

    For more information about the Webb telescope, visit: http://www.webb.nasa.gov or http://www.nasa.gov/webb

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

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  • richardmitnick 9:33 am on October 9, 2017 Permalink | Reply
    Tags: , , Baryons, , CMB - Cosmic Microwave Background, , , ,   

    From New Scientist: “Half the universe’s missing matter has just been finally found” 

    NewScientist

    New Scientist

    9 October 2017
    Leah Crane

    1
    Discoveries seem to back up many of our ideas about how the universe got its large-scale structure
    Andrey Kravtsov (The University of Chicago) and Anatoly Klypin (New Mexico State University). Visualisation by Andrey Kravtsov

    The missing links between galaxies have finally been found. This is the first detection of the roughly half of the normal matter in our universe – protons, neutrons and electrons – unaccounted for by previous observations of stars, galaxies and other bright objects in space.

    Two separate teams found the missing matter – made of particles called baryons rather than dark matter – linking galaxies together through filaments of hot, diffuse gas.

    “The missing baryon problem is solved,” says Hideki Tanimura at the Institute of Space Astrophysics in Orsay, France, leader of one of the groups. The other team was led by Anna de Graaff at the University of Edinburgh, UK.

    Because the gas is so tenuous and not quite hot enough for X-ray telescopes to pick up, nobody had been able to see it before.

    “There’s no sweet spot – no sweet instrument that we’ve invented yet that can directly observe this gas,” says Richard Ellis at University College London. “It’s been purely speculation until now.”

    So the two groups had to find another way to definitively show that these threads of gas are really there.

    Both teams took advantage of a phenomenon called the Sunyaev-Zel’dovich effect that occurs when light left over from the big bang passes through hot gas. As the light travels, some of it scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background [CMB] – our snapshot of the remnants from the birth of the cosmos.

    CMB per ESA/Planck

    ESA/Planck

    Stack ‘em up

    In 2015, the Planck satellite created a map of this effect throughout the observable universe. Because the tendrils of gas between galaxies are so diffuse, the dim blotches they cause are far too slight to be seen directly on Planck’s map.

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

    Both teams selected pairs of galaxies from the Sloan Digital Sky Survey that were expected to be connected by a strand of baryons. They stacked the Planck signals for the areas between the galaxies, making the individually faint strands detectable en masse.

    Tanimura’s team stacked data on 260,000 pairs of galaxies, and de Graaff’s group used over a million pairs. Both teams found definitive evidence of gas filaments between the galaxies. Tanimura’s group found they were almost three times denser than the mean for normal matter in the universe, and de Graaf’s group found they were six times denser – confirmation that the gas in these areas is dense enough to form filaments.

    “We expect some differences because we are looking at filaments at different distances,” says Tanimura. “If this factor is included, our findings are very consistent with the other group.”

    Finally finding the extra baryons that have been predicted by decades of simulations validates some of our assumptions about the universe.

    “Everybody sort of knows that it has to be there, but this is the first time that somebody – two different groups, no less – has come up with a definitive detection,” says Ralph Kraft at the Harvard-Smithsonian Center for Astrophysics in Massachusetts.

    “This goes a long way toward showing that many of our ideas of how galaxies form and how structures form over the history of the universe are pretty much correct,” he says.

    Journal references: arXiv, 1709.05024
    A Search for Warm/Hot Gas Filaments Between Pairs of SDSS Luminous Red Galaxies

    and 1709.10378v1
    Missing baryons in the cosmic web revealed by the Sunyaev-Zel’dovich effect

    See the full article here .

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  • richardmitnick 12:44 pm on September 15, 2017 Permalink | Reply
    Tags: , , , CMB - Cosmic Microwave Background, , , Timescape cosmology, Universe   

    From Motherboard: “New Supernova Analysis Questions Dark Energy, Cosmic Acceleration” 

    motherboard

    Motherboard

    Sep 15 2017
    Michael Byrne

    Timescape cosmology offers a way around one of the universe’s best mysteries.

    1
    Andrew Pontzen and Fabio Governato/ Wikimedia Commons

    One of my personal favorite features of the universe is that it is at this moment being ripped to shreds. Granted, it’s so far a very slow ripping, but, thanks to a peculiar property often referred to as dark energy, the universe is not just expanding, but it is accelerating in its expansion.

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

    It will continue to do so, which means that as time increases, it will expand faster and faster. Eventually all of this ripping will render existence an endless expanse of cold nothingness. Space will have been shredded and scattered to infinity.

    This is a still pretty new understanding. Though Einstein kinda-sorta predicted it, it wasn’t until the 1990s that observations of distant supernovae indicated to astronomers that space is receding from itself, that there is some fundamental-seeming driver―commonly referred to as dark energy―that makes empty spaces want to become bigger and emptier. The evidence was that light from these supernovae appeared to be redshifted, a phenomenon where life waves become stretched out as a light source moves away from the observer.

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

    According to a paper published this week in the Monthly Notices of the Royal Astronomical Society, we might just be wrong about all of this. The accelerating expansion may just be a sort of illusion driven by an incorrect assumption about the nature of the distribution of mass across the universe. As cosmological assumptions go, it’s a big one: The universe will remain, on average, smooth and uniform in all locations and from all perspectives.

    Maybe not?

    In more technical terms, we’re talking about the cosmological properties of isotropy and homogeneity. Together, they form the cosmological principle, which is mostly supported by the apparent uniformity of the cosmic microwave background. What the authors behind the current study suggest is that maybe the cosmological principle is bunk, and, if this is the case, then observations of distant supernovae take on a different meaning because we can no longer assume that the universe looks about the same for every observer in every location.

    “While the remarkable isotropy of the CMB points to an initial state with a very high degree of smoothness, the late epoch Universe encompasses a complex cosmic web of structures,” the paper notes.

    CMB per ESA/Planck

    ESA/Planck

    “It is dominated in volume by voids that are threaded and surrounded by clusters of galaxies distributed in sheets, knots and filaments.” In other words, space doesn’t really look all that smooth and uniform after all.

    The researchers’ alternative has a name: the timescape scenario. Because matter distributions may differ across the universe, different observers and different points within that space can be imagined to have their own relatively independent clocks (per Einstein, gravity bends light and so it bends time). With different notions of time, these different locations will then have different notions of cosmic expansion.

    The study doesn’t read like a classic crank/contrarian screed and the authors seem willing enough to concede that there may well be nothing to it. It will just depend on more data. In the meantime, the timescape scenario may at least serve as a “diagnostic tool” or alternative perspective that can help astronomers better test current understandings of the large-scale structure of the universe.

    See the full article here .

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    The future is wonderful, the future is terrifying. We should know, we live there. Whether on the ground or on the web, Motherboard travels the world to uncover the tech and science stories that define what’s coming next for this quickly-evolving planet of ours.

    Motherboard is a multi-platform, multimedia publication, relying on longform reporting, in-depth blogging, and video and film production to ensure every story is presented in its most gripping and relatable format. Beyond that, we are dedicated to bringing our audience honest portraits of the futures we face, so you can be better informed in your decision-making today.

     
  • richardmitnick 4:21 pm on August 4, 2017 Permalink | Reply
    Tags: , , , CMB - Cosmic Microwave Background, , , , ,   

    From Quanta: “Scientists Unveil a New Inventory of the Universe’s Dark Contents” 

    Quanta Magazine
    Quanta Magazine

    August 3, 2017
    Natalie Wolchover

    In a much-anticipated analysis of its first year of data, the Dark Energy Survey (DES) telescope experiment has gauged the amount of dark energy and dark matter in the universe by measuring the clumpiness of galaxies — a rich and, so far, barely tapped source of information that many see as the future of cosmology.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    The analysis, posted on DES’s website today and based on observations of 26 million galaxies in a large swath of the southern sky, tweaks estimates only a little. It draws the pie chart of the universe as 74 percent dark energy and 21 percent dark matter, with galaxies and all other visible matter — everything currently known to physicists — filling the remaining 5 percent sliver.

    The results are based on data from the telescope’s first observing season, which began in August 2013 and lasted six months. Since then, three more rounds of data collection have passed; the experiment begins its fifth and final planned observing season this month. As the 400-person team analyzes more of this data in the coming years, they’ll begin to test theories about the nature of the two invisible substances that dominate the cosmos — particularly dark energy, “which is what we’re ultimately going after,” said Joshua Frieman, co-founder and director of DES and an astrophysicist at Fermi National Accelerator Laboratory (Fermilab) and the University of Chicago. Already, with their first-year data, the experimenters have incrementally improved the measurement of a key quantity that will reveal what dark energy is.

    Both terms — dark energy and dark matter — are mental place holders for unknown physics. “Dark energy” refers to whatever is causing the expansion of the universe to accelerate, as astronomers first discovered it to be doing in 1998. And great clouds of missing “dark matter” have been inferred from 80 years of observations of their apparent gravitational effect on visible matter (though whether dark matter consists of actual particles or something else, nobody knows).

    The balance of the two unknown substances sculpts the distribution of galaxies. “As the universe evolves, the gravity of dark matter is making it more clumpy, but dark energy makes it less clumpy because it’s pushing galaxies away from each other,” Frieman said. “So the present clumpiness of the universe is telling us about that cosmic tug-of-war between dark matter and dark energy.”

    2
    The Dark Energy Survey uses a 570-megapixel camera mounted on the Victor M. Blanco Telescope in Chile (left). The camera is made out of 74 individual light-gathering wafers.

    A Dark Map

    Until now, the best way to inventory the cosmos has been to look at the Cosmic Microwave Background [CMB]: pristine light from the infant universe that has long served as a wellspring of information for cosmologists, but which — after the Planck space telescope mapped it in breathtakingly high resolution in 2013 — has less and less to offer.

    CMB per ESA/Planck

    ESA/Planck

    Cosmic microwaves come from the farthest point that can be seen in every direction, providing a 2-D snapshot of the universe at a single moment in time, 380,000 years after the Big Bang (the cosmos was dark before that). Planck’s map of this light shows an extremely homogeneous young universe, with subtle density variations that grew into the galaxies and voids that fill the universe today.

    Galaxies, after undergoing billions of years of evolution, are more complex and harder to glean information from than the cosmic microwave background, but according to experts, they will ultimately offer a richer picture of the universe’s governing laws since they span the full three-dimensional volume of space. “There’s just a lot more information in a 3-D volume than on a 2-D surface,” said Scott Dodelson, co-chair of the DES science committee and an astrophysicist at Fermilab and the University of Chicago.

    To obtain that information, the DES team scrutinized a section of the universe spanning an area 1,300 square degrees wide in the sky — the total area of 6,500 full moons — and stretching back 8 billion years (the data were collected by the half-billion-pixel Dark Energy Camera mounted on the Victor M. Blanco Telescope in Chile). They statistically analyzed the separations between galaxies in this cosmic volume. They also examined the distortion in the galaxies’ apparent shapes — an effect known as “weak gravitational lensing” that indicates how much space-warping dark matter lies between the galaxies and Earth. These two probes — galaxy clustering and weak lensing — are two of the four approaches that DES will eventually use to inventory the cosmos. Already, the survey’s measurements are more precise than those of any previous galaxy survey, and for the first time, they rival Planck’s.

    4

    “This is entering a new era of cosmology from galaxy surveys,” Frieman said. With DES’s first-year data, “galaxy surveys have now caught up to the cosmic microwave background in terms of probing cosmology. That’s really exciting because we’ve got four more years where we’re going to go deeper and cover a larger area of the sky, so we know our error bars are going to shrink.”

    For cosmologists, the key question was whether DES’s new cosmic pie chart based on galaxy surveys would differ from estimates of dark energy and dark matter inferred from Planck’s map of the cosmic microwave background. Comparing the two would reveal whether cosmologists correctly understand how the universe evolved from its early state to its present one. “Planck measures how much dark energy there should be” at present by extrapolating from its state at 380,000 years old, Dodelson said. “We measure how much there is.”

    The DES scientists spent six months processing their data without looking at the results along the way — a safeguard against bias — then “unblinded” the results during a July 7 video conference. After team leaders went through a final checklist, a member of the team ran a computer script to generate the long-awaited plot: DES’s measurement of the fraction of the universe that’s matter (dark and visible combined), displayed together with the older estimate from Planck. “We were all watching his computer screen at the same time; we all saw the answer at the same time. That’s about as dramatic as it gets,” said Gary Bernstein, an astrophysicist at the University of Pennsylvania and co-chair of the DES science committee.

    Planck pegged matter at 33 percent of the cosmos today, plus or minus two or three percentage points. When DES’s plots appeared, applause broke out as the bull’s-eye of the new matter measurement centered on 26 percent, with error bars that were similar to, but barely overlapped with, Planck’s range.

    “We saw they didn’t quite overlap,” Bernstein said. “But everybody was just excited to see that we got an answer, first, that wasn’t insane, and which was an accurate answer compared to before.”

    Statistically speaking, there’s only a slight tension between the two results: Considering their uncertainties, the 26 and 33 percent appraisals are between 1 and 1.5 standard deviations or “sigma” apart, whereas in modern physics you need a five-sigma discrepancy to claim a discovery. The mismatch stands out to the eye, but for now, Frieman and his team consider their galaxy results to be consistent with expectations based on the cosmic microwave background. Whether the hint of a discrepancy strengthens or vanishes as more data accumulate will be worth watching as the DES team embarks on its next analysis, expected to cover its first three years of data.

    If the possible discrepancy between the cosmic-microwave and galaxy measurements turns out to be real, it could create enough of a tension to lead to the downfall of the “Lambda-CDM model” of cosmology, the standard theory of the universe’s evolution. Lambda-CDM is in many ways a simple model that starts with Albert Einstein’s general theory of relativity, then bolts on dark energy and dark matter. A replacement for Lambda-CDM might help researchers uncover the quantum theory of gravity that presumably underlies everything else.

    What Is Dark Energy?

    According to Lambda-CDM, dark energy is the “cosmological constant,” represented by the Greek symbol lambda Λ in Einstein’s theory; it’s the energy that infuses space itself, when you get rid of everything else. This energy has negative pressure, which pushes space away and causes it to expand. New dark energy arises in the newly formed spatial fabric, so that the density of dark energy always remains constant, even as the total amount of it relative to dark matter increases over time, causing the expansion of the universe to speed up.

    The universe’s expansion is indeed accelerating, as two teams of astronomers discovered in 1998 by observing light from distant supernovas. The discovery, which earned the leaders of the two teams the 2011 Nobel Prize in physics, suggested that the cosmological constant has a positive but “mystifyingly tiny” value, Bernstein said. “There’s no good theory that explains why it would be so tiny.” (This is the “cosmological constant problem” that has inspired anthropic reasoning and the dreaded multiverse hypothesis.)

    On the other hand, dark energy could be something else entirely. Frieman, whom colleagues jokingly refer to as a “fallen theorist,” studied alternative models of dark energy before co-founding DES in 2003 in hopes of testing his and other researchers’ ideas. The leading alternative theory envisions dark energy as a field that pervades space, similar to the “inflaton field” that most cosmologists think drove the explosive inflation of the universe during the Big Bang. The slowly diluting energy of the inflaton field would have exerted a negative pressure that expanded space, and Frieman and others have argued that dark energy might be a similar field that is dynamically evolving today.

    DES’s new analysis incrementally improves the measurement of a parameter that distinguishes between these two theories — the cosmological constant on the one hand, and a slowly changing energy field on the other. If dark energy is the cosmological constant, then the ratio of its negative pressure and density has to be fixed at −1. Cosmologists call this ratio w. If dark energy is an evolving field, then its density would change over time relative to its pressure, and w would be different from −1.

    Remarkably, DES’s first-year data, when combined with previous measurements, pegs w’s value at −1, plus or minus roughly 0.04. However, the present level of accuracy still isn’t enough to tell if we’re dealing with a cosmological constant rather than a dynamic field, which could have w within a hair of −1. “That means we need to keep going,” Frieman said.

    The DES scientists will tighten the error bars around w in their next analysis, slated for release next year; they’ll also measure the change in w over time, by probing its value at different cosmic distances. (Light takes time to reach us, so distant galaxies reveal the universe’s past). If dark energy is the cosmological constant, the change in w will be zero. A nonzero measurement would suggest otherwise.

    Larger galaxy surveys might be needed to definitively measure w and the other cosmological parameters. In the early 2020s, the ambitious Large Synoptic Survey Telescope (LSST) will start collecting light from 20 billion galaxies and other cosmological objects, creating a high-resolution map of the universe’s clumpiness that will yield a big jump in accuracy.

    LSST


    LSST Camera, built at SLAC



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

    The data might confirm that we occupy a Lambda-CDM universe, infused with an inexplicably tiny cosmological constant and full of dark matter whose nature remains elusive. But Frieman doesn’t discount the possibility of discovering that dark energy is an evolving quantum field, which would invite a deeper understanding by going beyond Einstein’s theory and tying cosmology to quantum physics.

    “With these surveys — DES and LSST that comes after it — the prospects are quite bright,” Dodelson said. “It is more complicated to analyze these things because the cosmic microwave background is simpler, and that is good for young people in the field because there’s a lot of work to do.”

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 1:01 pm on July 17, 2017 Permalink | Reply
    Tags: , , , CMB - Cosmic Microwave Background, , , , How big is the universe?, ,   

    From COSMOS: “How big is the universe?” 

    Cosmos Magazine bloc

    COSMOS

    17 July 2017
    Cathal O’Connell

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

    “Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.” – Douglas Adams, Hitchhikers Guide to the Galaxy.

    In one sense the edge of the universe is easy to mark out: it’s the distance a beam of light could have travelled since the beginning of time. Anything beyond is impossible for us to observe, and so outside our so-called ‘observable universe’. You might guess that the distance from the centre of the universe to the edge is simply the age of the universe (13.8 billion years) multiplied by the speed of light: 13.8 billion light years.

    But space has been stretching all this time; and just as an airport walkway extends the stride of a walking passenger, the moving walkway of space extends the stride of light beams. It turns out that in the 13.8 billion years since the beginning of time, a light beam could have travelled 46.3 billion light years from its point of origin in the Big Bang. If you imagine this beam tracing a radius, the observable universe is a sphere whose diameter is double that: 92.6 billion light years.

    “Since nothing is faster than light, absolutely anything could in principle happen outside the observable universe,” says Andrew Liddle, an astronomer at the University of Edinburgh. “It could end and we’d have no way of knowing.”

    But we have good reasons to suspect the entire Universe (capitalised now to distinguish from the merely observable universe) goes on a lot further than the part we can observe – and that it is possibly infinite. So how can we know what goes on beyond the observable universe?

    Imagine a bacterium swimming in a fishbowl. How could it know the true extent of its seemingly infinite world? Well, distortions of light from the curvature of the glass might give it a clue. In the same way, the curvature of the universe tells us about its ultimate size.

    “The geometry of the universe can be of three different kinds,” says Robert Trotta, an astrophysicist at Imperial College London. It could be closed (like a sphere), open (like a saddle) or flat (like a table).

    2
    Universal geometry: the universe could be closed like sphere, open like a saddle or flat like a table. The first option would make it finite; the other two, infinite.
    Cosmos Magazine.

    The key to measuring its curvature is the cosmic microwave background (CMB) radiation – a wash of light given out by the fireball of plasma that pervaded the universe 400,000 years after the Big Bang. It’s our snapshot of the universe when it was very young and about 1,000 times smaller than it is today.

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA

    NASA/COBE

    Cosmic Microwave Background NASA/WMAP

    NASA/WMAP satellite

    CMB per ESA/Planck

    ESA/Planck

    Just as ancient geographers once used the curviness of the Earth’s horizon to work out the size of our planet, astronomers are using the curvinesss of the CMB at our cosmic horizon to estimate the size of the universe.

    The key is to use satellites to measure the temperature of different features in the CMB. The way these features distort across the CMB landscape is used to calculate its geometry. “So determining the size and geometry, of the Universe helps us determine what happened right after its birth,” Trotta says.

    Since the late 1980s, three generations of satellites have mapped the CMB with ever improving resolution, generating better and better estimates of the universe’s curvature. The latest data, released in March 2013, came from the European Space Agency’s Planck telescope. It estimated the curvature to be completely flat, at least to within a measurement certainty of plus or minus 0.4%.

    The extreme flatness of the universe supports the theory of cosmic inflation. This theory holds that in a fraction of a second (10−36 second to be precise) just after its birth, the universe inflated like a balloon, expanding many orders of magnitude while stretching and flattening its surface features.

    Perfect flatness would mean the universe is infinite, though the plus or minus 0.4% margin of error means we can’t be sure. It might still be finite but very big. Using the Planck data, Trotta and his colleagues worked out the minimum size of the actual Universe would have to be at least 250 times greater than the observable universe.

    The next generation of telescopes should improve on the data from the Planck telescope. Whether they will give us a definitive answer about the size of the universe remains to be seen. “I imagine that we will still treat the universe as very nearly flat and still not know well enough to rule out open or closed for a long time to come,” says Charles Bennet, head of the new CLASS array of microwave telescopes in Chile.

    As it turns out, owing to background noise there are fundamental limits to how well we can ever measure the curvature, no matter how good the telescopes get. In July 2016, physicists at Oxford worked out we cannot possibly measure a curvature below about 0.01%. So we still have a ways to go, though measurements so far, and the evidence from inflation theory, has most physicists weighing toward the view the universe is probably infinite. An impassioned minority, however, have had a serious problem with that.

    Getting rid of infinity, the great British physicist Paul Dirac said, is the most important challenge in physics. “No infinity has ever been observed in nature,” notes Columbia University astrophysicist Janna Levin in her 2001 memoir How the Universe got its Spots. “Nor is infinity tolerated in a scientific theory.”

    So how come physicists keep allowing that the universe itself may be infinite? The idea goes back to the founding fathers of physics. Newton, for example, reasoned that the universe must be infinite based on his law of gravitation. It held that everything in the universe attracted everything else. But if that were so, eventually the universe would be pulled towards a single point, in the way that a star eventually collapses under its own weight. This was at odds with his firm belief the universe had always existed. So, he figured, the only explanation was infinity – the equal pull in all directions would keep the universe static, and eternal.

    Albert Einstein, 250 years later at the start of the 20th century, similarly envisioned an eternal and infinite universe. General relativity, his theory of the universe on the grandest scales, plays out on an infinite landscape of spacetime.

    Mathematically speaking, it is easier to propose a universe that goes on forever than to have to deal with the edges. Yet to be infinite is to be unreal – a hyperbole, an absurdity.

    In his short story The Library of Babel, Argentinian writer Jorge Luis Borges imagines an infinite library containing every possible book of exactly 410 pages: “…for every sensible line of straightforward statement, there are leagues of senseless cacophonies, verbal jumbles and incoherences.” Because there are only so many possible arrangements of letters, the possible number of books is limited, and so the library is destined to repeat itself.

    An infinite Universe leads to similar conclusions. Because there are only so many ways that atoms can be arranged in space (even within a region 93 billion light years across), an infinite Universe requires that there must be, out there, another huge region of space identical to ours in every respect. That means another Milky Way, another Earth, another version of you and another of me.

    Physicist Max Tegmark, of the Massachusetts Institute of Technology, has run the numbers. He estimates that, in an infinite Universe, patches of space identical to ours would tend to come along about every 1010115 metres (an insanely huge number, one with more zeroes after it than there are atoms in the observable universe). So no danger of bumping into your twin self down at the shops; but still Levin does not accept it: “Is it arrogance or logic that makes me believe this is wrong? There’s just one me, one you. The universe can’t be infinite.”

    Levin was one of the first theorists to approach general relativity from a new perspective. Rather than thinking about geometry, which describes the shape of space, she looked at its topology: the way it was connected.

    All those assumptions about flat, closed or open universes were only valid for huge, spherical universes, she argued. Other shapes could be topologically ‘flat’ and still finite.

    “Your idea of a donut-shaped universe is intriguing, Homer,” says Stephen Hawking in a 1999 episode of The Simpsons. “I may have to steal it.” Actually, the show’s writers had already stolen the idea from Levin—who published her analysis of a donut-shaped universe in 1998.

    A donut, she noted, actually had – “topologically speaking” – zero curvature because the negative curvature on the inside is balanced by the positive curvature on the outside. The (near) zero curvature measured in the CMB was therefore as consistent with a donut as with a flat surface.

    5
    One ring theory to rule them all: CMB data doesn’t rule out a donut-shape, but it would be an awfully big one. Mehau Kulyk / Getty Images.

    In such a universe, Levin realised, you might cross the cosmos in a spaceship, the way sailors crossed the globe, and find yourself back where you started. This idea inspired Australian physicist Neil Cornish, now based at Montana State University, to think about how the very oldest light, from the CMB, might have circumnavigated the cosmos. If the donut universe were below a threshold size, that would create a telltale signature, which Cornish called “circles in the sky”. Alas, when CMB data came back from the Wilkinson Microwave Anisotropy Probe (WMAP) in 2001, no such signatures were found. That doesn’t rule out the donut theory entirely; but it does mean that the universe, if it is a donut, is an awfully big one.

    Attempts to directly prove or disprove the infinity of the universe seem to lead us to a dead-end, at least with current technology. But we might do it by inference, Cornish believes. Inflation theory does a compelling job of explaining the key features of our universe; and one of the offshoots of inflation is the multiverse theory.

    It’s the kind of theory that, when you first hear it, seems to have sprung from the mind of a science-fiction author indulging in mind-expanding substances. Actually it was first proposed by influential Stanford physicist Andrei Linde in the 1980s. Linde – together with Alan Guth at MIT and Alexei Starobinsky at Russia’s Landau Institute for Theoretical Physics – was one of the architects of inflation theory.

    Guth and Starobinsky’s original ideas had inflation petering out in the first split second after the big bang; Linde, however, had it going on and on, with new universes sprouting off like an everlasting ginger root.

    Linde has since showed that “eternal inflation” is probably an inevitable part of any inflation model. This eternal inflation, or multiverse, model is attractive to Linde because it solves the greatest mystery of all: why the laws of physics seem fine-tuned to allow our existence.

    The strength of gravity is just enough to allow stable stars to form and burn, the electromagnetic and nuclear forces are just the right strength to allow atoms to form, for complex molecules to evolve, and for us to come to be.

    In each newly sprouted universe these constants get assigned randomly. In some, gravity might be so strong that the universe recollapses immediately after its big bang. In others, gravity would be so weak that atoms of hydrogen would never condense into stars or galaxies. With an infinite number of new universes sprouting into and out of existence, by chance one will pop up that is fit for life to evolve.

    6
    Infinite variety: in the the eternal inflation model, new universes sprout off like an everlasting ginger root. Andrei Linde.

    The multiverse theory has its critics, notably another co-founder of inflation theory, Paul Steinhardt. who told Scientific American in 2014: “Scientific ideas should be simple, explanatory, predictive. The inflationary multiverse as currently understood appears to have none of those properties.” Meanwhile Paul Davies at the University of Arizona wrote in The New York Times that “invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen creator”.

    But in another sense the multiverse is the simpler of the two inflation models. In a few lines of equations, or just a few sentences of speech, the multiverse gives us a mechanism to explain the origin of our universe, just as Charles Darwin’s theory of natural selection explained the origin of species. As Max Tegmark puts it: “Our judgment therefore comes down to which we find more wasteful and inelegant: many worlds or many words.”

    To settle the issue, we will need to know more about what went down in the first split-second of the universe. Perhaps gravitational waves will be the answer, a way to ‘hear’ the vibrations of the big bang itself.

    Whether infinite or finite, stand-alone or one of an endless multitude, the universe is surely a mindbending place. Which brings us back to The Hitchhiker’s Guide to the Galaxy: “If there’s any real truth, it’s that the entire multidimensional infinity of the Universe is almost certainly being run by a bunch of maniacs.”

    See the full article here .

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  • richardmitnick 9:11 am on July 12, 2017 Permalink | Reply
    Tags: , , , , CMB - Cosmic Microwave Background, , ,   

    From astrobites: “What’s your Cosmology? Ask CMB Maps” 

    Astrobites bloc

    Astrobites

    July 12, 2017
    Gourav Khullar

    Title: Cosmological-parameter determination with Microwave Background Maps
    Authors: G. Jungman, M. Kamionkowski, A. Kosowsky and D. N. Spergel
    First Author’s Institution: Dept. of Physics, Syracuse University, New York, USA

    Status: Physical Review D (1996), [open access]

    There are papers that talk of groundbreaking discoveries. There are papers which review the current status of the field, akin to bringing you up-to-date with what’s going on. And then there are papers that open up portals to new sub-fields, with the clarity of their message and the precision of the questions they pose. Today’s paper is one such publication, which in 1996 started an interesting journey in the world of Cosmic Microwave Background (CMB) and Observational Cosmology.

    The Beginning

    Discovered for the first time in the 1970s, CMB studies have relied on measuring the temperature of this relic radiation today, which has sent photons to us from the era when the universe was essentially a plasma of matter and radiation. This era of the universe is where we can see the earliest ‘CMB photons’, a surface aptly called the surface of last scattering. Measuring its temperature gives us an idea about the energy content of the universe at that surface, which decreases as the photons travel towards us and lose energy in an ever-expanding universe.

    2
    Fig 1. The CMB Temperature map of the entire sky, observed by WMAP (as of 2012). The different colors correspond to different temperatures, at the minute scale of micro-Kelvins.

    NASA/WMAP satellite

    It was discovered in 1992 by the Nobel prize-winning satellite COBE that this radiation was isotropic to one parts in 100000, i.e. the uniformity of the CMB temperature across two points in the sky was only different by 10^-5!

    NASA/COBE

    Following this, studies were undertaken to discuss what these anisotropies, or non-uniformities actually meant. Today, we know of several mechanisms that answer this question – mechanisms that have gained credence with results from CMB telescopes like WMAP, PLANCK, the Atacama Cosmology Telescope, and the South Pole Telescope.

    CMB per ESA/Planck


    ESA/Planck

    3
    The Atacama Cosmology Telescope (ACT) is a six-metre telescope on Cerro Toco in the Atacama Desert in the north of Chile, near the Llano de Chajnantor Observatory.

    South Pole Telescope SPTPOL

    But back in 1996, these programs did not exist. The authors of our paper undertook the task of figuring out the theory of a future mission that could conclusively tell us about the nature of the universe back at the last CMB surface. This in turn, would help us characterize the early universe as well as the evolution of the universe between us and the surface of last scattering. What is the study of the evolution of universe since the big bang, but observational cosmology!

    Cosmological Parameters

    Observational cosmology is a game of measuring the following parameters with utmost accuracy and precision:

    Total Density of the universe Ω – baryonic matter, dark matter, radiation, curvature/space
    Hubble Constant H0, acceleration of the universe
    The Cosmological Constant Λ, responsible for the accelerated expansion of the current universe
    Inflation parameters, to constrain the perturbations of pre-CMB and near-CMB era universe
    Mass of neutrino species, that affect structure formation in the universe
    Ionization history of the universe

    Where do CMB observations come into the picture here? CMB is mostly measured in the form of temperature maps, a representation of the energy of the CMB photons across the sky (now, and by extrapolation back in the early universe). This information is best displayed as temperature differences as a function of angular scales in the sky, or ell’s as they are called. The term ell (or l) comes from the fact that on a 3-D sphere like the universe, the best way to compare two different points is to expand the temperature using spherical harmonics (which have ell’s or l in them), just as we expand points on a 2-D surface in terms of sine and cosine. If ell’s are hard to imagine, angular scales are more intuitive (check top axis on Figure 2)!

    3
    Fig 2. Anisotropies as a function of angular scale (or ell’s) in the sky, as observed by different telescopes e.g. WMAP, Boomerang. The solid line is a theoretical model that fits the observations.

    A better resolution of the telescope allows us to distinguish between temperatures in nearby regions, i.e. at smaller scales (or higher ell, in CMB lingo). A better sensitivity allows us to capture minute differences in this temperature. The authors in today’s paper assume a sensitivity and resolution better than COBE, and talk about their projections of a future experiment (which turned out to be WMAP)!

    CMB Anisotropies: Predictions

    The authors go about their predictions by describing the basic accepted theory (at the time) surrounding CMB generation, and what could have possibly caused the width and peaks of the anisotropies look the way they do (seen in Fig 2). Let’s see if we can capture a few of the ideas put forward here.

    4
    Fig 3. Different predictions of cosmological parameters as a function of ell’s (or angular scale), from today’s paper. Each solid line in each panel is a prediction of the CMB map for a specific value of that parameter, keeping the other three parameters constant.

    1.If the cosmological constant is too high in the universe, it increases the distance between us and the surface of last scattering, and subsequently in the anisotropy map.
    2.Moreover, if there is more structure between us and the CMB because of the evolution of the universe(e.g. galaxy clusters), that would make the photons scatter more off this structure, and hence increase the peaks (or strengths) of these anisotropies.
    3.If more perturbations were going on when the CMB was a plasma(at a time when the universe was tiny and most of the points in the sky were in close proximity with each other), the anisotropies seen at large scale NOW (that used to be close by back then) would be larger. Hence, this would mean higher peaks at lower ell, or higher angular scales.
    4.The biggest peak in Figure 2, is seen at an angular scale (or ell) of the horizon at surface of last scattering. We call this a horizon, because that is literally the edge of the universe that could communicate with each other back in the CMB era. This was a fixed physical scale, but what it looks to us today depends entirely on whether our universe is flat, closed or open. For example, in an open universe (like a sphere), the subtended angular scale would look wider than in a flat universe. Hence, the spectrum would move to a lower ell (or higher scales).

    What has happened since?

    5
    Fig 4.The three squares are 10-square degree patches of the sky. The difference in colors are displaying the different resolution and sensitivities of the three generations of CMB telescopes. COBE kickstarted the field of CMB anistropies, while Planck clearly sets the current standards.

    Predictions like these form the core content of this paper, which led to several anisotropy studies in the future. WMAP, the natural all-sky successor to COBE, put amazing constraints on CMB anisotropies in temperature in 2001 (Fig 1). The Planck satellite is the current standard for CMB studies at low-ell (large angular scales e.g. across the sky), with SPT and ACT contributing to high-ell (smaller angular scale e.g. galaxy clusters) studies. The future is even brighter for CMB (literally, and metaphorically), as we look forward to higher sensitivities, and resolution that helps with smaller and smaller angular scales in the sky.

    As John Carlstrom – astrophysicist at the University of Chicago and a pioneer in CMB studies – rightly says, “CMB is a gift that keeps on giving!”

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 11:27 am on June 25, 2017 Permalink | Reply
    Tags: , , , CMB - Cosmic Microwave Background, , D.O.E. Office of Science, , , , Lambda-Cold Dark Matter Accelerated Expansion of the Universe, ,   

    From US D.O.E. Office of Science: “Our Expanding Universe: Delving into Dark Energy” 

    DOE Main

    Department of Energy Office of Science

    06.21.17
    Shannon Brescher Shea
    shannon.shea@science.doe.gov

    Space is expanding ever more rapidly and scientists are researching dark energy to understand why.

    1
    This diagram shows the timeline of the universe, from its beginnings in the Big Bang to today. Image courtesy of NASA/WMAP Science Team.

    The universe is growing a little bigger, a little faster, every day.

    And scientists don’t know why.

    If this continues, almost all other galaxies will be so far away from us that one day, we won’t be able to spot them with even the most sophisticated equipment. In fact, we’ll only be able to spot a few cosmic objects outside of the Milky Way. Fortunately, this won’t happen for billions of years.

    But it’s not supposed to be this way – at least according to theory. Based on the fact that gravity pulls galaxies together, Albert Einstein’s theory predicted that the universe should be expanding more slowly over time. But in 1998, astrophysicists were quite surprised when their observations showed that the universe was expanding ever faster. Astrophysicists call this phenomenon “cosmic acceleration.”

    “Whatever is driving cosmic acceleration is likely to dominate the future evolution of the universe,” said Josh Frieman, a researcher at the Department of Energy’s (DOE) Fermilab [FNAL] and director of the 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

    While astrophysicists know little about it, they often use “dark energy” as shorthand for the cause of this expansion. Based on its effects, they estimate dark energy could make up 70 percent of the combined mass and energy of the universe. Something unknown that both lies outside our current understanding of the laws of physics and is the major influence on the growth of the universe adds up to one of the biggest mysteries in physics. DOE’s Office of Science is supporting a number of projects to investigate dark energy to better understand this phenomenon.

    The Start of the Universe

    Before scientists can understand what is causing the universe to expand now, they need to know what happened in the past. The energy from the Big Bang drove the universe’s early expansion. Since then, gravity and dark energy have engaged in a cosmic tug of war. Gravity pulls galaxies closer together; dark energy pushes them apart. Whether the universe is expanding or contracting depends on which force dominates, gravity or dark energy.

    Just after the Big Bang, the universe was much smaller and composed of an extremely high-energy plasma. This plasma was vastly different from anything today. It was so dense that it trapped all energy, including light. Unlike the current universe, which has expanses of “empty” space dotted by dense galaxies of stars, this plasma was nearly evenly distributed across that ancient universe.

    As the universe expanded and became less dense, it cooled. In a blip in cosmic time, protons and electrons combined to form neutral hydrogen atoms. When that happened, light was able to stream out into the universe to form what is now known as the “cosmic microwave background [CMB].”

    CMB per ESA/Planck


    ESA/Planck

    Today’s instruments that detect the cosmic microwave background provide scientists with a view of that early universe.

    Back then, gravity was the major force that influenced the structure of the universe. It slowed the rate of expansion and made it possible for matter to coalesce. Eventually, the first stars appeared about 400 million years after the Big Bang. Over the next several billion years, larger and larger structures formed: galaxies and galaxy clusters, containing billions to quadrillions (a million billion) of stars. While these cosmic objects formed, the space between galaxies continued to expand, but at an ever slower rate thanks to gravitational attraction.

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

    But somewhere between 3 and 7 billion years after the Big Bang, something happened: instead of the expansion slowing down, it sped up. Dark energy started to have a bigger influence than gravity. The expansion has been accelerating ever since.

    Scientists used three different types of evidence to work out this history of the universe. The original evidence in 1998 came from observations of a specific type of supernova [Type 1a]. Two other types of evidence in the early 2000s provided further support.

    “It was this sudden avalanche of results through cosmology,” said Eric Linder, a Berkeley Lab researcher and Office of Science Cosmic Frontier program manager.

    Now, scientists estimate that galaxies are getting 0.007 percent further away from each other every million years. But they still don’t know why.

    What is Dark Energy?

    “Cosmic acceleration really points to something fundamentally different about how the forces of the universe work,” said Daniel Eisenstein, a Harvard University researcher and former director of the Sloan Digital Sky Survey. “We know of four major forces: gravity, electromagnetism, and the weak and strong forces. And none of those forces can explain cosmic acceleration.”

    So far, the evidence has spurred two competing theories.

    The leading theory is that dark energy is the “cosmological constant,” a concept Albert Einstein created in 1917 to balance his equations to describe a universe in equilibrium. Without this cosmological constant to offset gravity, a finite universe would collapse into itself.

    Today, scientists think the constant may represent the energy of the vacuum of space. Instead of being “empty,” this would mean space is actually exerting pressure on cosmic objects. If this idea is correct, the distribution of dark energy should be the same everywhere.

    All of the observations fit this idea – so far. But there’s a major issue. The theoretical equations and the physical measurements don’t match. When researchers calculate the cosmological constant using standard physics, they end up with a number that is off by a huge amount: 1 X 10^120 (1 with 120 zeroes following it).

    “It’s hard to make a math error that big,” joked Frieman.

    That major difference between observation and theory suggests that astrophysicists do not yet fully understand the origin of the cosmological constant, even if it is the cause of cosmic acceleration.

    The other possibility is that “dark energy” is the wrong label altogether. A competing theory posits that the universe is expanding ever more rapidly because gravity acts differently at very large scales from what Einstein’s theory predicts. While there’s less evidence for this theory than that for the cosmological constant, it’s still a possibility.

    The Biggest Maps of the Universe

    To collect evidence that can prove or disprove these theories, scientists are creating a visual history of the universe’s expansion. These maps will allow astrophysicists to see dark energy’s effects over time. Finding that the structure of the universe changed in a way that’s consistent with the cosmological constant’s influence would provide strong evidence for that theory.

    There are two types of surveys: imaging and spectroscopic. The Dark Energy Survey and Large Synoptic Survey Telescope (LSST) are imaging surveys, while the Baryon Oscillation Spectroscopic Survey (part of the Sloan Digital Sky Survey), eBOSS, and the Dark Energy Spectroscopic Instrument are spectroscopic.


    LSST Camera, built at SLAC



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

    BOSS Supercluster Baryon Oscillation Spectroscopic Survey (BOSS)

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

    Imaging surveys use giant cameras – some the size of cars – to take photos of the night sky. The farther away the object, the longer the light has taken to reach us. Taking pictures of galaxies, galaxy clusters, and supernovae at various distances shows how the distribution of matter has changed over time. The Dark Energy Survey, which started collecting data in 2013, has already photographed more than 300 million galaxies. By the time it finishes in 2018, it will have taken pictures of about one-eighth of the entire night sky. The LSST will further expand what we know. When it starts in 2022, the LSST will use the world’s largest digital camera to take pictures of 20 billion galaxies.

    “That is an amazing number. It could be 10% of all of the galaxies in the observable universe,” said Steve Kahn, a professor of physics at Stanford and LSST project director.

    However, these imaging surveys miss a key data point – how fast the Milky Way and other galaxies are moving away from each other. But spectroscopic surveys that capture light outside the visual spectrum can provide that information. They can also more accurately estimate how far away galaxies are. Put together, this information allows astrophysicists to look back in time.

    The Baryon Oscillation Spectroscopic Survey (BOSS), part of the larger Sloan Digital Sky Survey, was one of the biggest projects to take, as the name implies, a spectroscopic approach. It mapped more than 1.2 million galaxies and quasars.

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

    However, there’s a major gap in BOSS’s data. It could measure what was going on 5 billion years ago using bright galaxies and 10 billion years ago using bright quasars. But it had nothing about what was going on in-between. Unfortunately, this time period is most likely when dark energy started dominating.

    “Seven billion years ago, dark energy starts to really dominate and push the universe apart more rapidly. So we’re making these maps now that span that whole distance. We start in the backyard of the Milky Way, our own galaxy, and we go out to 7 billion light years,” said David Schlegel, a Berkeley Lab researcher who is the BOSS principal investigator. That 7 billion light years spans the time from when the light was originally emitted to it reaching our telescopes today.

    Two new projects are filling that gap: the eBOSS survey and the Dark Energy Spectroscopic Instrument (DESI). eBOSS will target the missing time span from 5 to 7 billion years ago.

    4
    SDSS eBOSS.

    DESI will go back even further – 11 billion light years. Even though the dark energy was weaker then relative to gravity, surveying a larger volume of space will allow scientists to make even more precise measurements. DESI will also collect 10 times more data than BOSS. When it starts taking observations in 2019, it will measure light from 35 million galaxies and quasars.

    “We now realize that the majority of … the universe is stuff that we’ll never be able to directly measure using experiments here on Earth. We have to infer their properties by looking to the cosmos,” said Rachel Bean, a researcher at Cornell University who is the spokesperson for the LSST Dark Energy Science Collaboration. Solving the mystery of the galaxies rushing away from each other, “really does present a formidable challenge in physics. We have a lot of work to do.”

    See the full article here .

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    The mission of the Energy Department is to ensure America’s security and prosperity by addressing its energy, environmental and nuclear challenges through transformative science and technology solutions.

    Science Programs Organization

    The Office of Science manages its research portfolio through six program offices:

    Advanced Scientific Computing Research
    Basic Energy Sciences
    Biological and Environmental Research
    Fusion Energy Sciences
    High Energy Physics
    Nuclear Physics

    The Science Programs organization also includes the following offices:

    The Department of Energy’s Small Business Innovation Research and Small Business Technology Transfer Programs, which the Office of Science manages for the Department;
    The Workforce Development for Teachers and Students program sponsors programs helping develop the next generation of scientists and engineers to support the DOE mission, administer programs, and conduct research; and
    The Office of Project Assessment provides independent advice to the SC leadership regarding those activities essential to constructing and operating major research facilities.

     
  • richardmitnick 10:10 am on June 18, 2017 Permalink | Reply
    Tags: , , , Celestial boondocks: Study supports the idea that we live in a void, CMB - Cosmic Microwave Background,   

    From U Wisconsin Madison: “Celestial boondocks: Study supports the idea that we live in a void” 

    U Wisconsin

    University of Wisconsin

    June 6, 2017
    Terry Devitt

    Cosmologically speaking, the Milky Way and its immediate neighborhood are in the boondocks.

    In a 2013 observational study, Ryan Keenan, a postdoctoral researcher at Academia Sinica in Taiwan and a UW–Madison alumnus, and his former UW advisor, astronomer Amy Barger, showed that our galaxy, in the context of the large-scale structure of the universe, resides in an enormous void — a region of space containing far fewer galaxies, stars and planets than expected.

    Now, a new study by a UW–Madison undergraduate, also a student of Barger’s, not only firms up the idea that we exist in one of the holes of the Swiss cheese structure of the cosmos, but helps ease the apparent disagreement or tension between different measurements of the Hubble Constant, the unit cosmologists use to describe the rate at which the universe is expanding today.

    1
    The universe as simulated by the Millennium Simulation is structured like Swiss cheese in filaments and voids. The Milky Way, according to UW–Madison astronomers, exists in one of the holes or voids of the large-scale structure of the cosmos. Millennium Simulation Project.

    Results from the new study were presented here today (June 6, 2017) at a meeting of the American Astronomical Society.

    The tension arises from the realization that different techniques astrophysicists employ to measure how fast the universe is expanding give different results. “No matter what technique you use, you should get the same value for the expansion rate of the universe today,” explains Ben Hoscheit, the Wisconsin student presenting his analysis of the apparently much larger than average void that our galaxy resides in. “Fortunately, living in a void helps resolve this tension.”

    The reason for that is that a void — with far more matter outside the void exerting a slightly larger gravitational pull — will affect the Hubble Constant value one measures from a technique that uses relatively nearby supernovae, while it will have no effect on the value derived from a technique that uses the cosmic microwave background (CMB), the leftover light from the Big Bang.

    CMB per ESA/Planck


    ESA/Planck

    _____________________________________________________________________

    The new study not only firms up the idea that we exist in one of the holes of the Swiss cheese structure of the cosmos, but sheds light on how we measure the rate at which the universe is expanding today.
    _____________________________________________________________________

    The new Wisconsin report is part of the much bigger effort to better understand the large-scale structure of the universe. The structure of the cosmos is Swiss cheese-like in the sense that it is composed of “normal matter” in the form of voids and filaments. The filaments are made up of superclusters and clusters of galaxies, which in turn are composed of stars, gas, dust and planets. Dark matter and dark energy, which cannot yet be directly observed, are believed to comprise approximately 95 percent of the contents of the universe.

    The void that contains the Milky Way, known as the KBC void for Keenan, Barger and the University of Hawaii’s Lennox Cowie, is at least seven times as large as the average, with a radius measuring roughly 1 billion light years. To date, it is the largest void known to science. Hoscheit’s new analysis, according to Barger, shows that Keenan’s first estimations of the KBC void, which is shaped like a sphere with a shell of increasing thickness made up of galaxies, stars and other matter, are not ruled out by other observational constraints.

    “It is often really hard to find consistent solutions between many different observations,” says Barger, an observational cosmologist who also holds an affiliate graduate appointment at the University of Hawaii’s Department of Physics and Astronomy. “What Ben has shown is that the density profile that Keenan measured is consistent with cosmological observables. One always wants to find consistency, or else there is a problem somewhere that needs to be resolved.”

    The bright light from a supernova explosion, where the distance to the galaxy that hosts the supernova is well established, is the “candle” of choice for astronomers measuring the accelerated expansion of the universe. Because those objects are relatively close to the Milky Way and because no matter where they explode in the observable universe, they do so with the same amount of energy, it provides a way to measure the Hubble Constant.

    2
    A map of the local universe as observed by the Sloan Digital Sky Survey. The orange areas have higher densities of galaxy clusters and filaments. Sloan Digital Sky Survey

    SDSS Telescope at Apache Point Observatory, NM, USA


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

    Alternatively, the cosmic microwave background is a way to probe the very early universe. “Photons from the CMB encode a baby picture of the very early universe,” explains Hoscheit. “They show us that at that stage, the universe was surprisingly homogeneous. It was a hot, dense soup of photons, electrons and protons, showing only minute temperature differences across the sky. But, in fact, those tiny temperature differences are exactly what allow us to infer the Hubble Constant through this cosmic technique.”

    A direct comparison can thus be made, Hoscheit says, between the ‘cosmic’ determination of the Hubble Constant and the ‘local’ determination derived from observations of light from relatively nearby supernovae.

    The new analysis made by Hoscheit, says Barger, shows that there are no current observational obstacles to the conclusion that the Milky Way resides in a very large void. As a bonus, she adds, the presence of the void can also resolve some of the discrepancies between techniques used to clock how fast the universe is expanding.

    See the full article here .

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    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • richardmitnick 4:57 pm on May 30, 2017 Permalink | Reply
    Tags: , , , , , CMB - Cosmic Microwave Background, , , ,   

    From Universe Today: “What Was Cosmic Inflation? The Quest to Understand the Earliest Universe” 

    universe-today

    Universe Today

    30 May, 2017
    Fraser Cain

    The Big Bang. The discovery that the Universe has been expanding for billions of years is one of the biggest revelations in the history of science. In a single moment, the entire Universe popped into existence, and has been expanding ever since.

    We know this because of multiple lines of evidence: the cosmic microwave background radiation, the ratio of elements in the Universe, etc. But the most compelling one is just the simple fact that everything is expanding away from everything else. Which means, that if you run the clock backwards, the Universe was once an extremely hot dense region.

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    A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)).

    Let’s go backwards in time, billions of years. The closer you get to the Big Bang, the closer everything was, and the hotter it was. When you reach about 380,000 years after the Big Bang, the entire Universe was so hot that all matter was ionized, with atomic nuclei and electrons buzzing around each other.

    Keep going backwards, and the entire Universe was the temperature and density of a star, which fused together the primordial helium and other elements that we see to this day.

    Continue to the beginning of time, and there was a point where everything was so hot that atoms themselves couldn’t hold together, breaking into their constituent protons and neutrons. Further back still and even atoms break apart into quarks. And before that, it’s just a big question mark. An infinitely dense Universe cosmologists called the singularity.

    When you look out into the Universe in all directions, you see the cosmic microwave background radiation. That’s that point when the Universe cooled down so that light could travel freely through space.

    And the temperature of this radiation is almost exactly the same in all directions that you look. There are tiny tiny variations, detectable only by the most sensitive instruments.

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    Cosmic microwave background seen by Planck. Credit: ESA

    ESA/Planck

    When two things are the same temperature, like a spoon in your coffee, it means that those two things have had an opportunity to interact. The coffee transferred heat to the spoon, and now their temperatures have equalized.

    When we see this in opposite sides of the Universe, that means that at some point, in the ancient past, those two regions were touching. That spot where the light left 13.8 billion years ago on your left, was once directly touching that spot on your right that also emitted its light 13.8 billion years ago.

    This is a great theory, but there’s a problem: The Universe never had time for those opposite regions to touch. For the Universe to have the uniform temperature we see today, it would have needed to spend enough time mixing together. But it didn’t have enough time, in fact, the Universe didn’t have any time to exchange temperature.

    Imagine you dipped that spoon into the coffee and then pulled it out moments later before the heat could transfer, and yet the coffee and spoon are exactly the same temperature. What’s going on?

    To address this problem, the cosmologist Alan Guth proposed the idea of cosmic inflation in 1980. That moments after the Big Bang, the entire Universe expanded dramatically.

    4
    Alan Guth, 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

    5
    Alan Guth’s notes. http://www.bestchinanews.com/Explore/4730.html

    And by “moments”, I mean that the inflationary period started when the Universe was only 10^-36 seconds old, and ended when the Universe was 10^-32 seconds old.

    And by “expanded dramatically”, I mean that it got 10^26 times larger. That’s a 1 followed by 26 zeroes.

    Before inflation, the observable Universe was smaller than an atom. After inflation, it was about 0.88 millimeters. Today, those regions have been stretched 93 billion light-years apart.

    This concept of inflation was further developed by cosmologists Andrei Linde, Paul Steinhardt, Andy Albrecht and others.

    Inflation resolved some of the shortcomings of the Big Bang Theory.

    The first is known as the flatness problem. The most sensitive satellites we have today measure the Universe as flat. Not like a piece-of-paper-flat, but flat in the sense that parallel lines will remain parallel forever as they travel through the Universe. Under the original Big Bang cosmology, you would expect the curvature of the Universe to grow with time.

    4
    The horizon problem in Big Bang cosmology. How is it that distant parts of the universe possess such similar physical properties? Credit: Addison Wesley.

    The second is the horizon problem. And this is the problem I mentioned above, that two regions of the Universe shouldn’t have been able to see each other and interact long enough to be the same temperature.

    The third is the monopole problem. According to the original Big Bang theory, there should be a vast number of heavy, stable “monopoles”, or a magnetic particle with only a single pole. Inflation diluted the number of monopoles in the Universe so don’t detect them today.

    Although the cosmic microwave background radiation appears mostly even across the sky, there could still be evidence of that inflationary period baked into it.

    5
    The Big Bang and primordial gravitational waves. Credit: bicepkeck.org

    In order to do this, astronomers have been focusing on searching for primordial gravitational waves. These are different from the gravitational waves generated through the collision of massive objects. Primordial gravitational waves are the echoes from that inflationary period which should be theoretically detectable through the polarization, or orientation, of light in the cosmic microwave background radiation.

    A collaboration of scientists used an instrument known as the Background Imaging of Cosmic Extragalactic Polarization (or BICEP2) to search for this polarization, and in 2014, they announced that maybe, just maybe, they had detected it, proving the theory of cosmic inflation was correct.

    Gravitational Wave Background from BICEP 2 which ultimately failed to be correct. The Planck team determined that the culprit was cosmic dust.

    Unfortunately, another team working with the space-based Planck telescope posted evidence that the fluctuations they saw could be fully explained by intervening dust in the Milky Way.


    Bicep 2 Collaboration Steffen Richter Harvard

    6
    Planck’s view of its nine frequencies. Credit: ESA and the Planck Collaboration

    The problem is that BICEP2 and Planck are designed to search for different frequencies. In order to really get to the bottom of this question, more searches need to be done, scanning a series of overlapping frequencies. And that’s in the works now.

    BICEP2 and Planck and the newly developed South Pole Telescope as well as some observatories in Chile are all scanning the skies at different frequencies at the same time.

    South Pole Telescope SPTPOL

    Distortion from various types of foreground objects, like dust or radiation should be brighter or dimmer in the different frequencies, while the light from the cosmic microwave background radiation should remain constant throughout.

    There are more telescopes, searching more wavelengths of light, searching more of the sky. We could know the answer to this question with more certainty shortly.

    One of the most interesting implications of cosmic inflation, if proven, is that our Universe is actually just one in a vast multiverse. While the Universe was undergoing that dramatic expansion, it could have created bubbles of spacetime that spawned other universes, with different laws of physics.

    In fact, the father of inflation, Alan Guth, said, “It’s hard to build models of inflation that don’t lead to a multiverse.”

    And so, if inflation does eventually get confirmed, then we’ll have a whole multiverse to search for in the cosmic microwave background radiation.

    The Big Bang was one of the greatest theories in the history of science. Although it did have a few problems, cosmic inflation was developed to address them. Although there have been a few false starts, astronomers are now performing a sensitive enough search that they might find evidence of this amazing inflationary period. And then it’ll be Nobel Prizes all around.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 7:32 pm on April 25, 2017 Permalink | Reply
    Tags: , , , CMB - Cosmic Microwave Background, , ,   

    From Durham via phys.org: “New survey hints at exotic origin for the Cold Spot” 

    Durham U bloc

    Durham University

    phys.org

    April 25, 2017

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    Figure 1. The map of the cosmic microwave background (CMB) sky produced by the Planck satellite. Red represents slightly warmer regions, and blue slightly cooler regions. The Cold Spot is shown in the inset, with coordinates on the x- and y-axes, and the temperature difference in millionths of a degree in the scale at the bottom. Credit: ESA and Durham University

    ESA/Planck

    A supervoid is unlikely to explain a ‘Cold Spot’ in the cosmic microwave background, according to the results of a new survey, leaving room for exotic explanations like a collision between universes. The researchers, led by postgraduate student Ruari Mackenzie and Professor Tom Shanks in Durham University’s Centre for Extragalactic Astronomy, publish their results in the Monthly Notices of the Royal Astronomical Society.

    The cosmic microwave background (CMB), a relic of the Big Bang, covers the whole sky. At a temperature of 2.73 degrees above absolute zero (or -270.43 degrees Celsius), the CMB has some anomalies, including the Cold Spot. This feature, about 0.00015 degrees colder than its surroundings, was previously claimed to be caused by a huge void, billions of light years across, containing relatively few galaxies.

    The accelerating expansion of the universe causes voids to leave subtle redshifts on light as it passes through via the integrated Sachs-Wolfe effect. In the case of the CMB this is observed as cold imprints. It was proposed that a very large foreground void could, in part, imprint the CMB Cold Spot which has been a source of tension in models of standard cosmology.

    Previously, most searches for a supervoid connected with the Cold Spot have estimated distances to galaxies using their colours. With the expansion of the universe more distant galaxies have their light shifted to longer wavelengths, an effect known as a cosmological redshift.

    The more distant the galaxy is, the higher its observed redshift. By measuring the colours of galaxies, their redshifts, and thus their distances, can be estimated. These measurements though have a high degree of uncertainty.

    In their new work, the Durham team presented the results of a comprehensive survey of the redshifts of 7,000 galaxies, harvested 300 at a time using a spectrograph deployed on the Anglo-Australian Telescope.


    AAO Anglo Australian Telescope near Siding Spring, New South Wales, Australia

    From this higher fidelity dataset, Mackenzie and Shanks see no evidence of a supervoid capable of explaining the Cold Spot within the standard theory.

    2
    Figure 2. The 3-D galaxy distribution in the foreground of the CMB Cold Spot, where each point is a cluster of galaxies. The galaxy distribution in the Cold Spot (black points, at right) is compared to the same in an area with no background Cold Spot (red points, at left). The number and size of low galaxy density regions in both areas are similar, making it hard to explain the existence of the CMB Cold Spot by the presence of ‘voids’. Credit: Durham University

    The researchers instead found that the Cold Spot region, before now thought to be underpopulated with galaxies, is split into smaller voids, surrounded by clusters of galaxies. This ‘soap bubble’ structure is much like the rest of the universe, illustrated in Figure 2 by the visual similarity between the galaxy distributions in the Cold Spot area and a control field elsewhere.

    Mackenzie commented: “The voids we have detected cannot explain the Cold Spot under standard cosmology. There is the possibility that some non-standard model could be proposed to link the two in the future but our data place powerful constraints on any attempt to do that.”

    If there really is no supervoid that can explain the Cold Spot, simulations of the standard model of the universe give odds of 1 in 50 that the Cold Spot arose by chance.

    Shanks added: “This means we can’t entirely rule out that the Spot is caused by an unlikely fluctuation explained by the standard model. But if that isn’t the answer, then there are more exotic explanations.

    ‘Perhaps the most exciting of these is that the Cold Spot was caused by a collision between our universe and another bubble universe. If further, more detailed, analysis of CMB data proves this to be the case then the Cold Spot might be taken as the first evidence for the multiverse – and billions of other universes may exist like our own.”

    For the moment, all that can be said is that the lack of a supervoid to explain the Cold Spot has tilted the balance towards these more unusual explanations, ideas that will need to be further tested by more detailed observations of the CMB.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Durham U campus

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

     
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