Tagged: BICEP2 Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 1:52 pm on January 30, 2015 Permalink | Reply
    Tags: , BICEP2, , keck Array South Pole   

    From ESA- “Planck: gravitational waves remain elusive” 

    ESASpaceForEuropeBanner
    European Space Agency

    30 January 2015
    Markus Bauer
    ESA Science and Robotic Exploration Communication Officer
    Tel: +31-71-565-6799
    Mob: +31-61-594-3-954
    Email: Markus.Bauer@esa.int

    Jan Tauber
    ESA Planck Project Scientist
    Tel: +31-71-565-5342
    Email: Jan.Tauber@esa.int

    1
    Planck view of BICEP2 field

    Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves.

    ESA Planck
    ESA/Planck

    BICEP 2
    BICEP2

    Keck Array
    Keck Array

    The Universe began about 13.8 billion years ago and evolved from an extremely hot, dense and uniform state to the rich and complex cosmos of galaxies, stars and planets we see today.

    An extraordinary source of information about the Universe’s history is the Cosmic Microwave Background, or CMB, the legacy of light emitted only 380 000 years after the Big Bang.

    Cosmic Background Radiation Planck
    CMB per Planck

    ESA’s Planck satellite observed this background across the whole sky with unprecedented accuracy, and a broad variety of new findings about the early Universe has already been revealed over the past two years.

    But astronomers are still digging ever deeper in the hope of exploring even further back in time: they are searching for a particular signature of cosmic ‘inflation’ – a very brief accelerated expansion that, according to current theory, the Universe experienced when it was only the tiniest fraction of a second old.

    This signature would be seeded by gravitational waves, tiny perturbations in the fabric of space-time, that astronomers believe would have been generated during the inflationary phase.

    Gravitational Wave Background
    Theorized gravitational wave pattern

    Interestingly, these perturbations should leave an imprint on another feature of the cosmic background: its polarisation.

    When light waves vibrate preferentially in a certain direction, we say the light is polarised.

    The CMB is polarised, exhibiting a complex arrangement across the sky. This arises from the combination of two basic patterns: circular and radial (known as E-modes), and curly (B-modes).

    Different phenomena in the Universe produce either E- or B-modes on different angular scales and identifying the various contributions requires extremely precise measurements. It is the B-modes that could hold the prize of probing the Universe’s early inflation.

    “Searching for this unique record of the very early Universe is as difficult as it is exciting, since this subtle signal is hidden in the polarisation of the CMB, which itself only represents only a feeble few percent of the total light,” says Jan Tauber, ESA’s project scientist for Planck.

    Planck is not alone in this search. In early 2014, another team of astronomers presented results based on observations of the polarised CMB on a small patch of the sky performed 2010–12 with BICEP2, an experiment located at the South Pole. The team also used preliminary data from another South Pole experiment, the Keck Array.

    They found something new: curly B-modes in the polarisation observed over stretches of the sky a few times larger than the size of the full Moon.

    The BICEP2 team presented evidence favouring the interpretation that this signal originated in primordial gravitational waves, sparking an enormous response in the academic community and general public.

    However, there is another contender in this game that can produce a similar effect: interstellar dust in our Galaxy, the Milky Way.

    3
    Planck view of Galactic dust

    The Milky Way is pervaded by a mixture of gas and dust shining at similar frequencies to those of the CMB, and this foreground emission affects the observation of the most ancient cosmic light. Very careful analysis is needed to separate the foreground emission from the cosmic background.

    Critically, interstellar dust also emits polarised light, thus affecting the CMB polarisation as well.

    “When we first detected this signal in our data, we relied on models for Galactic dust emission that were available at the time,” says John Kovac, a principal investigator of BICEP2 at Harvard University, in the USA.

    “These seemed to indicate that the region of the sky chosen for our observations had dust polarisation much lower than the detected signal.”

    The two ground-based experiments collected data at a single microwave frequency, making it difficult to separate the emissions coming from the Milky Way and the background.

    On the other hand, Planck observed the sky in nine microwave and sub-millimetre frequency channels, seven of which were also equipped with polarisation-sensitive detectors. By careful analysis, these multi-frequency data can be used to separate the various contributions.

    The BICEP2 team had chosen a field where they believed dust emission would be low, and thus interpreted the signal as likely to be cosmological.

    However, as soon as Planck’s maps of the polarised emission from Galactic dust were released, it was clear that this foreground contribution could be much higher than previously expected.

    In fact, in September 2014, Planck revealed for the first time that the polarised emission from dust is significant over the entire sky, and comparable to the signal detected by BICEP2 even in the cleanest regions.

    So, the Planck and BICEP2 teams joined forces, combining the satellite’s ability to deal with foregrounds using observations at several frequencies – including those where dust emission is strongest – with the greater sensitivity of the ground-based experiments over limited areas of the sky, thanks to their more recent, improved technology. By then, the full Keck Array data from 2012 and 2013 had also become available.

    “This joint work has shown that the detection of primordial B-modes is no longer robust once the emission from Galactic dust is removed,” says Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institut d’Astrophysique Spatiale in Orsay, France.

    “So, unfortunately, we have not been able to confirm that the signal is an imprint of cosmic inflation.”

    Deflecting light from the Big Bang

    Another source of B-mode polarisation, dating back to the early Universe, was detected in this study, but on much smaller scales on the sky.

    This signal, first discovered in 2013, is not a direct probe of the inflationary phase but is induced by the cosmic web of massive structures that populate the Universe and change the path of the CMB photons on their way to us.

    This effect is called ‘gravitational lensing’, since it is caused by massive objects bending the surrounding space and thus deflecting the trajectory of light much like a magnifying glass does. The detection of this signal using Planck, BICEP2 and the Keck Array together is the strongest yet.

    As for signs of the inflationary period, the question remains open.

    “While we haven’t found strong evidence of a signal from primordial gravitational waves in the best observations of CMB polarisation that are currently available, this by no means rules out inflation,” says Reno Mandolesi, principal investigator of the LFI instrument on Planck at University of Ferrara, Italy.

    In fact, the joint study sets an upper limit on the amount of gravitational waves from inflation, which might have been generated at the time but at a level too low to be confirmed by the present analysis.

    “This analysis shows that the amount of gravitational waves can probably be no more than about half the observed signal,” says Clem Pryke, a principal investigator of BICEP2 at University of Minnesota, in the USA.

    “The new upper limit on the signal due to gravitational waves agrees well with the upper limit that we obtained earlier with Planck using the temperature fluctuations of the CMB,” says Brendan Crill, a leading member of both the Planck and BICEP2 teams from NASA’s Jet Propulsion Laboratory in the USA.

    “The gravitational wave signal could still be there, and the search is definitely on.”

    “A Joint Analysis of BICEP2/Keck Array and Planck Data” by the BICEP2/Keck and Planck collaboration has been submitted to the journal Physical Review Letters.
    The study combines data from ESA’s Planck satellite and from the US National Science Foundation ground-based experiments BICEP2 and the Keck Array, at the South Pole.

    The analysis is based on observations of the CMB polarisation on a 400 square degree patch of the sky. The Planck data cover frequencies between 30 GHz and 353 GHz, while the BICEP2 and Keck Array data were taken at a frequency of 150 GHz.

    A public release of Planck data products will follow next week.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large

     
  • richardmitnick 4:07 am on January 15, 2015 Permalink | Reply
    Tags: , BICEP2, ,   

    From NOVA: “From Discovery to Dust” 

    PBS NOVA

    NOVA

    Wed, 29 Oct 2014
    Amanda Gefter

    The idea was too beautiful to be wrong.

    That you could start with nothing, apply some basic laws of physics, and get a universe out of it—a universe that was uniform on the largest scales but replete with the lumps and bumps we call stars and galaxies, a universe, that is, that looks like ours—well, it didn’t matter that the theory didn’t quite work at first. It was just too beautiful to be wrong.

    Inflation

    In Alan Guth’s original version of the theory in 1980, the nothingness at the beginning of time wasn’t really nothing at all. It was a field, the inflaton, and it teetered at the edge of a cliff, momentarily stable but not in its most stable, or lowest energy, state. This gave spacetime a negative pressure, creating a kind of anti-gravitational force that would push outward, sending the inflaton—that nascent field that would give birth to inflation—plummeting toward stability, causing the universe to expand exponentially, growing a million trillion trillion times bigger in the blink of an eye.

    1
    Barred spiral galaxy NGC 1672
    Inflation explains how everything from galaxies to dust may have come about.

    It was creation nearly ex nihilo—all you needed was the tiniest speck of a universe and inflation would transform it into something truly cosmic. There was just one problem: the plunge to the lowest energy state was a kind of phase transition, like water vapor condensing to liquid, and the transition would dissolve the inflaton into a sea of bubbles—pockets of lowest-energy regions—which would eventually collide and merge, collisions that would leave astronomical upheavals more disfiguring than anything we see on the sky today.

    Then, in 1981, Andrei Linde saved inflation from itself. He suggested that we didn’t have to worry about those bubbles because inflation could make them so big that our entire universe could fit inside just one of them. It didn’t matter what happened out at the edges or beyond—we’d never see it anyway.

    There was just one problem. The smooth, scarless space inside the bubble was too smooth, the density of matter so perfectly uniform that nothing so lumpy as stars or galaxies could ever form. It was Linde’s friend and fellow physicist Slava Mukhanov who had the solution: quantum fluctuations.

    Inflation was creation nearly ex nihilo.

    Quantum fluctuations are born of [Werner] Heisenberg’s uncertainty principle, which says that certain pairs of physical characteristics—position and momentum, time and energy—are bound together by a fundamental elusiveness, wherein the more accurately we can specify one, the more wildly the value of the other fluctuates. The universe cannot be perfectly uniform—uncertainty will not allow it. At a precise moment in time, energy varies recklessly; at a well-defined position, momentum soars and swerves. Precise moments and well-defined positions normally mean tiny scales of time and space, but inflation blows all that up. Inflation, Mukhanov told Linde, could take these tiny quantum fluctuations on the order of 10-33 cm and stretch them to astronomical proportions, creating slight peaks and valleys throughout space and laying a gravitational blueprint for what would eventually become a network of stars and galaxies.

    Still, Linde wasn’t satisfied. Getting inflation to start and end in just the right way required the whole thing to be improbably fine-turned. It was beautiful, but unnatural. There would be two more years of work before he found the solution: chaos. Inflation didn’t require fine-tuning, he realized; it didn’t need to teeter on a cliff’s edge. If the inflaton started off in a highly-probable and totally random state, then somewhere amongst the mess, there was bound to be a region with the right properties to spark inflation. From a sea of chaos, a vast island of order would emerge.

    That’s where the universe stood in the cold Moscow winter of 1986. Gorbachev had recently taken office as the General Secretary of the Communist Party and had just set into motion the perestroika—the restructuring of the Russian political, economic, and educational systems. For physicists like Linde, this engendered a strange silence. The old system for getting academic papers published abroad had been scrapped, but it hadn’t yet been replaced by a new one. So while inflation was being developed in the U.S., Russian physicists were forced to wait.

    Linde waited in bed. The doctors told him he was perfectly healthy, but he felt awful nonetheless. He was passing the time reading detective stories when the phone rang. It was the administration from the Lebedev Physical Institute, where he worked. They told him he was to travel to Italy to give a public lecture. He didn’t want to go. Under Gorbachev, Linde was allowed only one trip abroad each year, and he wasn’t about to waste it on a public lecture where he wouldn’t be working with other physicists or learning anything new. He told them he was too ill to travel. You are ill today, they said, but you’ll likely be healthy again soon, no? Or are you saying you are unable to go abroad at all?

    Linde grew scared. He knew if he said that he was unable to go abroad, they might never let him leave again—ever. He needed to prove that he could make the trip, and quickly. It was a Friday. He needed to get to the Hospital of the Academy of Sciences in order to obtain a certificate of health, but he was just learning how to drive and couldn’t risk a battle with the Moscow ice. He decided to pay for a taxi, a financial decision that didn’t come easy. Over the weekend he prepared the necessary travel documentation, and on Monday invested in another taxi ride to the Institute. He paid secretaries to immediately type up his paperwork, which he then ran to every corner of the Institute to get every last signature required. That bureaucratic nightmare ought to have taken a month and a half, and he accomplished it in four days. He dropped off the papers, went home, and collapsed into bed. He didn’t get up for two days.

    Soon the phone was ringing again. The trip was set, they told him, but the Italians wanted to see his lecture ahead of time—the day after tomorrow. Suddenly, Linde realized he had a golden opportunity. He could get around the systemless system and publish abroad! Instead of handing over his public lecture, he could write a new paper, give it to the powers that be and they would send it abroad for him—by diplomatic mail, no less. There was just one catch: he had half an hour to do it. It was the only way to get it typed up in time.

    Linde sat with his head in his hands, rolling it from side to side. Think, think. He felt like a compressed spring—he would either bounce to new heights or break under the stress. He knew that theorists can’t simply order up good ideas at will—physics doesn’t work that way. But today, he thought, it was going to have to.

    Thirty minutes later, he had come up with the theory of the chaotic self-reproducing inflationary multiverse. It was his greatest piece of work.

    Linde’s new theory reached beyond the bounds of the bubble. In his earlier version, our little patch of inflationary universe would arise from some small stretch of chaos. But while our universe was growing, what was happening behind the scenes? Surely there would be other regions where inflation could crop up. They’d be rare, but it didn’t matter—they would grow so big so rapidly that they would soon dominate the landscape. Each inflationary region creates more of itself—it’s self-reproducing. The process ends locally within each island universe, but on the largest scales it carries on, producing universe after universe after universe. In a half hour, Linde had taken our single universe, once the whole of everything there ever was or would be, and duplicated it, multiplied it, mutated it, sent it through a sequence of funhouse mirrors until it emerged on the other side a mere speck again, a humble, lone bubble in an infinite and growing multiverse.
    Seeing gravity waves…it would be like a fish seeing water.

    When he first developed the idea of inflation, Linde never for a second thought that it would be technologically feasible to test it. In principle, there were ways—you could look for the tiniest temperature fluctuations in the remnant heat from the Big Bang, those tiny quantum fluctuations that seeded the stars and galaxies, but that was a precision measurement he could barely fathom at the time. And if you wanted to dream even bigger, well, there ought to be something even more fundamental—quantum fluctuations of spacetime itself, primordial gravity waves. Seeing gravity waves…it would be like a fish seeing water. And seeing primordial gravity waves…well, it’s not just any water, it’s the first water, the origin of water, the origin of everything. But the technological skill that it would take to make that kind of measurement—it was downright unthinkable.

    On good days, he didn’t care. He knew the theory was right, he knew it in his bones. He knew it with the same kind of certainty that Einstein had about general relativity: When observations of the 1919 eclipse came in, proving that gravity bends light just as general relativity predicted, a reporter asked [Albert] Einstein how he would’ve felt had the experiment turned out differently. “I would have felt sorry for the dear Lord,” Einstein replied, “because the theory is correct.”

    The Device

    There was a problem with the antennas.

    When Chao-Lin Kuo arrived at NASA’s Jet Propulsion Laboratory in Cañada Flintridge, California in 2003, the BICEP. team was trying to implement Jamie Bock’s vision for a new polarization detector in their search for primordial gravity waves. Not that the old detectors didn’t work, but the things were unwieldy. Three copper feed horns, a handmade filter, and two detectors per pixel, all hand assembled. It’s not that they weren’t sensitive—they were nearly as sensitive as you can get. Rather, if they wanted better measurements, they didn’t need more sensitive detectors, they needed more detectors—quickly and cheaply. Bock’s vision was to digitize the whole assemblage and print them on circuit boards with microlithography, creating a kind of mass-producible polarimeter-on-a-chip. If it worked, it would change everything. It would be like upgrading from vacuum tubes to integrated circuits. But the team was stuck. They had designed a beautiful antenna array, but its readings kept coming out wrong.

    2
    BICEP2 Detector
    A single polarization detector

    The plan was to mount the detector to a radio telescope at the South Pole, where it would catch light that’s been traveling through an expanding cosmos for the last 13.8 billion years and measure its polarization, or the direction in which the photons are waving relative to the direction of their motion. If they could pin down each photon’s polarization with enough precision and map them across the sky, they’d have some hope of discerning a pattern known as a B-mode, the signature of primordial gravity waves. Kuo, a 30-year-old postdoc, set to work, putting the array through a host of tests until he figured out the problem: it was because the feed lines were crossed. The array looked like a series of X’s, but at the center of each X, the antennas were picking up each other’s signals and screwing up the reading. He set to work on a new design.

    Kuo knew he had to keep the antennas at right angles from one another so they could subtract the horizontal polarization from the vertical and take the difference. And he had to keep them as symmetric as possible, because the difference they were looking for was one part in 30 million. One part in 30 million. All to find a B-mode. How exactly do you make something like that?

    When he really thought about it, this thing they were trying to do, this thing they were trying to measure, it pushed the bounds of sanity. But Kuo already had a taste for pulling something like this off. As a grad student back at Berkeley, he had worked on the ACBAR experiment, which took measurements of the cosmic microwave background temperature fluctuations.

    Cosmic Microwave Background  Planck
    CMB per ESA/Planck

    ESA Planck
    ESA/Planck

    The idea that you could build something with your own two hands, point it at the sky, and see the faintest details of the nascent universe some 14 billion years in the past…well, you had to see it to believe it. You see the pattern. It’s not an image in a textbook or an idea in your mind—it’s on the sky. You look at it and suddenly you realize that you are one of a handful of human beings who has ever cast his eyes on the Big Bang. Well, it’s not exactly the Big Bang; it’s 380,000 years later–a mere eyeblink in the cosmic course of things, but still. To see back to the very beginning, the very first fraction of the very first second, you need something better than light. You need gravity.
    …suddenly you realize that you are one of a handful of human beings who has ever cast his eyes on the Big Bang.

    Kuo tried design after design. On some level, the antennae weren’t all that different from the kind you’d find in a cell phone, except this cell phone needed to answer calls from the beginning of time. The antenna array would shuffle the incoming photons down to the focal plane, where electromagnetism would be converted to heat and measured by an ultrasensitive thermometer. If you want to capture a signal that’s been steadily weakened over 14 billion years, you better make sure there’s virtually no heat and zero polarization coming from the instrument itself or it will totally swamp the measurement. That means keeping the detectors cooled to 0.25 Kelvin, just the slightest shiver above absolute zero. In the old way of thinking, the signal had to be transported off the focal plane and out of the cooling element to be read out by some room temperature electronics, but the transmission itself through heat conducting wires could warm the focal plane enough to drown out the signal. So Bock’s idea was to have the signals read by superconducting electronics on the focal plane itself using quantum-scale magnetic sensors developed at the National Institute of Standards and Technology in Colorado.

    In the meantime, they deployed the old detector to the South Pole in an experiment they named BICEP1. For three years, from 2006 to 2008, it would collect that nascent light and look for the slightest patterns of polarization.

    2
    The BICEP2 focal plane

    Back at JPL, it was Kuo’s fifth design that stuck. He built an antenna array that looked like a series of H’s, with spaces between the vertical and horizontal lines to avoid having the feed lines intersect. Once the array had been fabricated at JPL, it was time to put them to the test. Kuo placed them carefully in the cryostat. Then he waited.

    It would take several days to get things cold enough. First, liquid nitrogen would cool it down to 77 Kelvin. Then the liquid helium would kick in, lowering the temperature to 4 Kelvin. Finally, a few cubic centimeters of helium-3, a rare isotope. With helium-3, you have to tread carefully. The stuff is expensive; as a byproduct of plutonium production, it’s a controlled substance.

    While Kuo waited, he thought about inflation. If that exponential expansion really gave birth to the universe, it ought to have taken quantum fluctuations in spacetime and blown them up across the sky. Some 380,000 years later, the photons that make up the cosmic microwave background radiation would have navigated that same warped spacetime, a journey that would imprint itself uniquely in their polarization. Find the B-mode polarization and you’ve found inflation’s smoking gun. Looking around the lab, he wondered if he was the only one worrying about inflation. These guys were hardware wizards—they want to build cool things. Most of them didn’t have a lot of faith in theory. Kuo respected that. But for him, he needed to understand why he was doing this. Yes, he wanted to build a kickass detector. But he also wanted to know how the universe began.

    Once the helium-3 had everything cooled to 0.25 Kelvin, Kuo had to test the things, to see if they worked and to diagnose any problems. Start by sticking something room temperature in front of it and see what temperature reads out. Then something cooled with liquid nitrogen. Shine a source of microwaves at it, rotate their polarization, watch what happens. He ran every calibration test he could think of. The antenna array worked.

    Kuo had transformed Bock’s vision into a groundbreaking—and more important, functioning—detector. Because they used lithography, they could pack 512 of them on the focal plane, which meant BICEP2 would achieve the same sensitivity as BICEP1 in one-tenth the detection time, much like a bigger camera sensor can capture more stars at night. Kuo’s timing couldn’t have been better. BICEP1 was going off-line and the new technology had to ship out on the first flights of the year to Antarctica in September.

    Despite the pioneering technology, the truth was, no one on the team seemed to believe that a detection was in the cards. Even if inflation were correct, there was a good chance that primordial gravity waves would be way too small to measure. They just thought they’d use the telescope as a proving ground for the technology so that later it could be confidently incorporated into a next-generation space satellite. Satellites are expensive, and if something breaks once it’s up in orbit, you’re out of luck. So the BICEP2 team figured they’d take the technology out for a terrestrial test drive; in the meantime, they could place more upper limits on the amplitude of gravity waves and constrain some inflationary models in the process.
    No one on the team seemed to believe that a detection was in the cards.

    The physicist Andrew Lange had said that this was a wild goose chase. Still, Kuo couldn’t help hoping. Every once in awhile, he figured, you catch a goose. When [Arno] Penzias and [Robert] Wilson first discovered the cosmic microwave background in 1964, they thought it was literally pigeon shit. At least the BICEP2 team knew what they were looking for.

    In the middle of all that, Kuo had moved up the coast, from Pasadena to Palo Alto. He took a position at Stanford University, where he recruited an eager young grad student named Jamie Tolan to work with him on the measurement. One day, Tolan approached his advisor—he was writing a proposal for a NASA graduate student fellowship, and he asked Kuo to read the draft. In the proposal, Tolan laid out the goal of BICEP2: to see just how elusive primordial gravity waves are. Kuo smiled at Tolan. That’s not it, he told him. The goal is to detect them.

    The Questions

    Linde had wanted to be a geologist. His father was a radio physicist, his mother an experimental physicist who studied cosmic rays. The younger Linde wanted to do something different, something tangible. Something like rocks. But during the summer vacation between 7th and 8th grade, the Linde family drove from Moscow to the Black Sea. For a week, Linde sat in the back seat reading. He had brought two books: one on stars and the universe, the other on Einstein’s theory of special relativity. When they arrived at the Black Sea, three physicists stepped out of that car.

    At Moscow State University, Linde sought his colleagues’ advice: should he be a theorist or an experimentalist? The truth was, he didn’t think he was that great at calculation. He did, however, possess a certain intuition coupled with an obsessive mind. Once he became interested in a question, he couldn’t stop thinking about it. Linde soon realized he wasn’t nearly as impressed by measurements as he was by explanatory power. He didn’t want data—he wanted answers. Answers to big questions, the biggest: What happened when he was born? What will happen when he dies? What is it to feel, to think, to live, to exist? But he figured he’d start with simpler questions, the kind with more straightforward answers, like, how does an airplane fly? He promised himself he’d get to the hard ones eventually. There was no denying it. He was a theorist through and through.

    Eventually the hard questions snuck back in. When Linde came up with chaotic eternal inflation in that fateful half hour, he immediately realized the implications. In an infinite multiverse where physical constants can vary from one universe to the next, everything that can happen will happen—an infinite number of times. Every possible world, every incarnation of reality, every possible version of you living every possible version of your life. What then does it mean to want something, to do something, to be something? It was a vertiginous thought, but Linde didn’t let it get to him. So what if there were infinite Andrei Lindes? If I killed myself, he figured, it’s not like I’d survive as a copy—my death would simply become the moment that I was no longer identical to my copy, because I, unlike him, would be dead.

    In any case, it wasn’t clear that the copies existed in any meaningful way. That was the thing about quantum mechanics—the very nature of things seem to be determined by what an observer can measure. In the world of classical physics, you could have two baseballs that were identical in every way, and yet it’s fair to say that there are two of them. In the quantum realm, if you have two indistinguishable particles, you only have one particle. Wheeler and Feynman had emphasized that—in a sense, they said, there’s only one electron in the universe. Linde could never quite shake that.

    Even those quantum fluctuations—the very fluctuations that gave rise to the stars, polarized the microwave light, and created universe after universe—they are determined directly by what an observer can measure. Position and momentum, time and energy—these partners bound by uncertainty are so bound because the accurate measurement of one precludes the accurate measurement of the other. A particle doesn’t have a simultaneous position and momentum because an observer can’t measure a simultaneous position and momentum. Gravity waves are waves of uncertainty—uncertainty not only of existence but of observation. It was a fact that seemed to suggest that observers play some deep role in the nature of reality, a fact that Linde kept tucked away in the back of his mind. What is it to feel, to think, to live, to exist? If there was no observer who could simultaneously observe more than one Andrei Linde, then on some level you might say there’s still only one.

    Despite this, Linde was convinced that the existence of all those parallel universes held great explanatory power. While the multiverse was ultimately governed by the same laws of physics—by quantum mechanics and relativity, by inflation itself—each universe would be born with its own local sub-laws, a set of accidents that would determine its geometry, its physical constants, its particles, its forces, its own unique history. Inflation meant diversity. And diversity, Linde realized, was its own kind of explanation.

    So many features of our universe appear inexplicably fine-tuned for the existence of biological life. Change the strength of a force here or the mass of a particle there and poof!—no stars, no carbon, no life. Such coincidences demand explanation, and inflation had one: the strengths and masses vary from universe to universe, and we just happen to find ourselves in the one in which we can live. The inflationary multiverse may not have been predictive or observable, but it was explanatory. It could explain the illusion of design, the comprehensibility of the cosmos, the unreasonable effectiveness of mathematics. It could explain why the cosmological constant is so small and why the universe is so big. It could explain why we are here, why anything is here, because at the end of the day, Linde knew, physics isn’t really about the universe. It’s about us.
    Linde didn’t like being told what to think.

    The mass of the electron is 2,000 times lighter than that of the proton. Why? Well, if it were ten-times heavier or ten times lighter we wouldn’t be here to ask. Spacetime has four large dimensions. Why? Well, any more dimensions and the gravitational force between two objects would fall off faster than r-2; any fewer and general relativity couldn’t support any such forces all. Either way, you’ve got no stable planetary systems and no life.

    Such explanations are called “anthropic,” and they made people nervous, the theoretical physics equivalent of “just because.” Colleagues told Linde he shouldn’t think about such things, but he didn’t like being told what to think. When he decided to include a section on the anthropic principle in the cosmology book he wrote, his editor in Moscow told him to take it out. If you leave it in, she said, you’ll lose the respect of your colleagues. Yes, Linde replied, but if I take it out, I’ll lose my respect for myself.

    As far as he was concerned, the metaphysical is always brought into the fold of physics in the end, and inflation meant that the burden of proof was on those who wished to believe in a single universe. Einstein had once said, “What really interests me is whether God had any choice in the creation of the world.” He wanted the universe to be a singular specimen of logical perfection and uniqueness. Not Linde. Linde wanted diversity, choice. In Russia, they only had one choice of cheese.
    At the Bottom of the World

    It was Kuo’s fourth visit here, at the bottom of the world, but he still wasn’t used to the whiteness of it all. Everything, everywhere—just white. A blank spot on the world, like someone forgot to fill it in. An endless white that makes you think about infinity. He must’ve been ten years old the first time he thought about it, whether the universe was infinite or finite. That was back in Taiwan—some 8,000 miles from here—where the sun still sets on a summer’s night. It hadn’t made sense to him, as a boy, that reality would just come to an end, that there was a place beyond which there is no more place. What if you sat there at the edge and threw a ball? Where would it go? Someone else had made the same argument, he remembered. A philosopher? Now, as a physicist, he knew it wasn’t so simple— that the universe could be curved and closed, like the surface of a sphere, finite but without an edge. He supposed he had always been a physicist. Funny how all this white makes you think of that. Of all the colors, he missed green the most. Green and the smell of humidity. He had never realized what humidity smelled like until it was gone.

    3
    An LC-130 takes off from the Amundsen-Scott South Pole Station.

    It was hard to say how many days he had been here—hard to differentiate time when the scenery never changes, the weather never shifts, and the sun never goes down. Getting here had been an adventure, as usual. He had flown some 15 hours from California to Christchurch, New Zealand, for a stopover at the International Antarctic Center, where he traded his belongings for extreme cold weather gear before boarding an Air Force aircraft and flying another 14 hours to McMurdo Station here in Antarctica. From McMurdo it was another three-hour flight to the Amundsen-Scott South Pole Station on a plane that landed on skis. Stepping out onto the ice sheet, he had marveled again at the sky, so perfectly blue—the clearest sky on the planet.

    That’s why they were here. Antarctica is the largest desert on Earth. The altitude gets you up above most of the problematic parts of the atmosphere and the biting cold takes care of the rest—any stray water vapor in the air is frozen out of the sky, leaving microwave light from the early universe to stream through unimpeded. It also helps that the sun only rises and sets once a year.

    It was December now; he would be here until Valentine’s Day. The sun would set in March. He didn’t know how the “winter overs”—the people who stayed here past March—did it, not when -20°F was a warm summer day. Of course, the science station had grown more comfortable lately. It had a sauna now and a greenhouse for growing hydroponic fruits and vegetables. Earlier, they used to give you this weird yellow powder, and you’d mix it with water, fry it up, and call it a meal. Now, you could enjoy fresh produce in the cafeteria then go play on the basketball court or relax in the library or game room.

    Between the porthole windows in the doors and the firemen’s lockers lining the corridors, the place looked like the perfect combination of a research ship and a high school. Ship was more accurate—the Amundsen-Scott station, perched on Antarctica’s high plateau, stands on stilts to avoid the snow that never thaws atop a glacier some 9,000 feet thick that ever so slowly drifts.

    4
    The Dark Sector Lab

    To get to work, Kuo would walk along the ice sheet, across the airplane runway, upwind to the Dark Sector lab, so-named because all white light and radio transmission is forbidden there. The lab was hardly a mile away, but cold, wind, and altitude have a funny way of stretching distance. By the time he reached the telescope, he was queasy and out of breath.

    BICEP2 was a refracting telescope with a small aperture—just 26 centimeters. It could afford to be small because the features it was looking for were the size of the full moon on the sky. All of its moving parts were kept inside where it’s warm. Only its head poked out through a hole they had cut in the roof. The telescope was focused on a 20° patch of the so-called Southern Hole, the cleanest stretch of sky available with a clear view straight out of our Milky Way. At the South Pole, the same patch of sky just keeps spinning in circles above you; it never slips behind the horizon or disappears from sight. The telescope can stare it down for years and never blink.

    BICEP2 observed only photons with a frequency of 150 GHz, filtering everything else out. They had opted for a single frequency because it was the only way to optimize every part of the instrument. When you’re trying to avoid dust, which can polarize your light and mimic the signal of gravity waves, 150 GHz is the sweet spot. It’s where you’re most likely to see the clearest signal of gravity waves. The two possible impostors, magnetized radiation from extreme astronomical phenomenon and interstellar dust, rise at low and high frequencies respectively. But 150 GHz is right in the Goldilocks middle. It also happens to be the peak frequency of the cosmic microwave background, the photons that flew out of the dense early universe 380,000 years ago.

    The telescope had two lenses that focused the light, a design similar to Galileo’s, except that this one fed the light into the most sensitive superconducting detectors ever built. Kuo and his team were here to assemble the thing and then take some calibrations, but even turning a screw was proving to be difficult in the cold.

    Once the telescope was up and running it would start collecting data, which it would store temporarily on the computers at the South Pole. But soon a low Earth orbit communications satellite would appear above the horizon and relay the data from the South Pole station to NASA’s White Sands complex in New Mexico. From there it would bounce around the U.S. until it landed in a cluster of computers at Harvard University, which the BICEP2 team could later access from California.

    California. Kuo wondered what his wife and children were doing back home in Stanford. They were probably enjoying the green, green grass and the warmth of a more fleeting sun.

    The Observer and the Observed

    California. Linde moved here in 1990 with his wife, Renata Kallosh, and their two sons. A year earlier they had left Moscow for Switzerland, intending to spend a year at CERN before heading back to the Soviet Union. But offers came in while they were there, including a double offer from Stanford University for both Linde and Kallosh, who is a string theorist, and so they changed course and immigrated to the U.S.

    In the two decades that followed, evidence for inflation mounted, and, in 2003, cosmologists hit the jackpot. NASA’s Wilkinson Microwave Anisotropy Probe (WMAP)—an 1,800-pound spacecraft that orbited the sun nearly a million miles out— had produced an unprecedented map of the microwave sky, measuring temperature differences in the near-uniform radiation down to one part in 100,000.

    NASA WMAP satellite
    WMAP

    Cosmic Background Radiation per WMAP
    CMB per WMAP

    Those slight hot and cold spots traced quantum fluctuations in the density of matter 380,000 years after the Big Bang, when the microwave light was first emitted. The pattern in the map bore out several key predictions of inflation with astounding precision. Even the inflation doubters were coming around. Now there was just one piece of evidence missing: B-mode polarization, the mark of primordial gravity waves.

    Linde wasn’t worried about B-modes. Most versions of inflation predicted them at amplitudes way too small to measure, which meant that even a non-detection could be a strange kind of confirmation, at least for those who already believed. As far as he was concerned, the experimental evidence was already overwhelming. Still, he supposed, on the off-chance they did discover B-modes—well, it would just drive home the fact that quantum mechanics needs to be taken seriously, even at cosmic scales. The beauty of inflation was that it provided the missing link between the tiny quantum world and the largest scales of the universe. We are the great-great-great-grandchildren of quantum fluctuations, he liked to say.

    When you try to apply the laws of quantum mechanics to the universe as a whole, you hit a paradox: all things quantum are defined in terms of what an observer can measure, but no one can measure the universe as a whole because, by definition, you can’t be outside the universe. The issue was captured most perfectly in the famous Wheeler-DeWitt equation, which showed that the quantum state of the universe could not evolve in time, stuck, as it were, in a frozen, eternal moment. As Linde often put it, without observers, the universe is dead.

    Linde knew that the only way to get time flowing was to observe the universe from here, on the inside. When we look out at the cosmos through a telescope, he thought, we don’t see ourselves in the picture. And so we split the world in two: observer and observed. We make a measurement, and the universe comes to life. It sounded awfully solipsistic, but there it was.

    As Linde often put it, without observers, the universe is dead.

    Everyone assumed you can talk about “observers” without talking about consciousness—things like Geiger counters or space telescopes—but Linde wasn’t so sure. If you remove subjective experience from the picture, he thought, there’s no more picture. He couldn’t help wondering whether consciousness was the missing ingredient that would make the ultimate theory of physics consistent. The idea was inspired by gravity waves.

    Back in the day, physicists thought of space and time as tools that we use to describe the motion of matter—not as things in their own right. It was Einstein who realized that even if you emptied the universe of matter, spacetime itself would remain and could exhibit a behavior all of its own: it could wave. Gravity waves meant that spacetime was equally as real and fundamental as matter itself. Later theoretical developments—namely supergravity—extended the symmetries of this space-time so that matter turned out to be nothing deeper than excitations of the geometry of superspace. In other words, it was spacetime that was fundamental and matter was derived, a tool for describing the excitations of spacetime.

    Linde wondered if consciousness awaited the same vindication. Today we think of it as a tool we use to describe the external world, and not as an entity on its own. But what if the external world were empty? What if consciousness was fundamental and the universe derived? Could space, time, and matter together be nothing more than excitations, the gravity waves of consciousness?

    What is it to feel, to think, to live, to exist? It was still the only question he really cared to answer. The rest was just details.

    The Signal

    They must have made a mistake.

    They had screwed up the analysis or there was some design flaw they hadn’t accounted for yet. A signal this bright—it had to be coming from the instrument itself. There was no way this thing was coming from the sky.

    BICEP2 had collected data for three years and now the team had set out to scour it for B-modes. But they barely had to scour. The B-modes were glaring.

    They couldn’t figure out what they’d done wrong. They could have sworn they’d accounted for any spurious polarization, any stray morsel of heat. The detectors had passed every last performance test with flying colors. Where was this thing coming from?

    They split the data in half, made a map from the first year and a half of observation and a map from the second year and a half. Then they subtracted them. They figured if the signal went away, they’d know it had been in both halves equally, that it hadn’t changed over time. But if it had changed over time—well then it wasn’t cosmological, it was an engineering blip. They ran the test. The signal canceled out. It wasn’t a blip.

    They split and recombined the data in every which way, pushed themselves to imagine even the most unlikely scenarios that would have the signal originating in the instrument. Again and again they came up empty handed. Eventually there was no alternative left standing: the signal was coming from the sky.

    Of course, there was always the issue of the dust. Everyone knew that interstellar dust in the Milky Way could polarize the photons and mimic the effect of gravity waves. Obviously the dust contributed to the signal, but the question was, how much? The Southern Hole at 150 GHz ought to be pretty clean. That’s why they chose it. But you never know.

    Obviously dust contributed to the signal, but the question was, how much?

    The team didn’t have access to any full sky maps with a decent signal-to-noise of polarized emissions from dust—but they knew exactly who did. The ESA’s Planck satellite had been mapping the dust from space and ought to be able to tell them exactly how much of it was contributing to their signal. The BICEP2 team submitted a request to share data. Request denied. They waited, then tried again. Request denied. Was the Planck team being competitive or did they simply feel the data wasn’t ready? Who could say. Either way, Kuo and his team were simply going to have to make do with whatever data they could get their hands on.

    3
    As the Milky Way passes overhead, charged particles of the aurora australis billow over the Dark Sector.

    They combed the literature for the leading dust models and fed the results of five of them into their own model. Unfortunately, the models were all built from observations of unpolarized dust at various points on the sky, which were then extrapolated. But without Planck’s actual data, it was their best shot.

    They used the models to create fake maps of dust, and they put in 3 million CPU hours on the Harvard supercomputer simulating the results 500 times. The signal wasn’t going away. Even after they subtracted the signal for the dust, the B-modes appeared to be still sitting there in plain sight.

    That’s when they noticed that a member of the Planck team, J.P. Bernard, had given a public lecture on the dust data. His presentation contained a slide with an image of the dust map. The BICEP team figured it was time to get creative. They digitized the image, reverse engineering it to extract their best guess at the raw data. They knew it was an uncertain procedure, but that was ok—they weren’t staking their claim on it. They were just going to use it as model #6.

    Again they subtracted the dust, and again the B-modes remained visible, bright as day.

    They had to strike the right balance between being careful and being quick. A signal this bright—someone else was bound to see it. They could feel the competition nipping at their heels. They all agreed to not say a word about it to anyone. Not until they were sure. They were at three-sigma certainty—that meant there was a 1 in 740 chance that the signal was a statistical fluke. In physics, three sigma is considered evidence. Five sigma, a 1 in 3.5 million chance…well that’s a discovery.

    5
    The B-mode pattern from BICEP2

    For a year they sat on the result. Kuo was hoping to hell it was real, though if you asked him to bet on it, he wouldn’t risk the money. He had a nagging fear that the B-modes were nothing more than mathematical contamination, just mundane E-mode polarization leaking out. The problem was that BICEP2 had only studied a small patch of sky. Each fragment of data is just a little line segment—it’s only when you look at the way those lines are drawn across the entire sky that a pattern emerges. If the line segments form a series of symmetric shapes, like circular ripples, that’s an E-mode: the standard pattern produced by the same old density fluctuations that create the hot and cold spots in the CMB. But if the pattern looks asymmetric, like pinwheels turning in a given direction, that’s the jackpot. Only primordial gravity waves can turn those pinwheels.

    They had data from a 20° patch of sky, which is to say, not a lot. What do you do with the line segments out toward the edges? You see hints of pattern there, perhaps a slight arc, a suggestion of a pinwheel. But what if it’s a circle? Your statistics start to break down. So you throw away some signal, a sacrifice to the gods of error bars. But how to strike just the right balance between signal and certainty was far from clear.

    One evening in Stanford, after he’d had dinner and helped put the kids to bed, Kuo noticed an e-mail from his grad student, Tolan.

    Two years earlier, Kuo had urged Tolan to find a better way to distinguish the E-modes from the B-modes out at the edges. Tolan began working on the problem on the side, “off pipeline.” They were told again and again, stick to the pipeline, it’s the only way to keep things running smoothly, and it was. Everyone treated Tolan’s work as a kind of side hobby, so he just kept at it, posting updates now and then to the team’s internal website.

    Kuo opened the e-mail. I’ve got a preliminary posting of the matrix estimator. Tolan had done it. He had found a way to cleanly separate the B-modes from the E-modes, and he had run their data. Kuo prepared himself for disappointment. He was sure the signal had disappeared. He clicked on the link to the internal website and scanned Tolan’s results.

    The signal hadn’t disappeared.

    The signal had gotten stronger.

    The error bars had shrunk, and the certainty had risen—from three sigma to five sigma. A discovery.

    That night, the sun went down, but Kuo couldn’t sleep.

    In the morning he e-mailed Tolan: If this signal is real, this is the home run of all home runs…

    If it were real, it would be the closest anyone had ever come to seeing the beginning of time. It would be the smoking gun proof of inflation. It would be a direct look at the quantum mechanical underpinnings of the universe, probing physics at energies a trillion times greater than what particle physicists could achieve in the hallowed tunnels of the LHC. If it were real, Kuo could finally tell his ten-year-old self the answer: if the universe isn’t infinite, it is really damn big.

    Funny, the difference between experiment and theory. Theory is the stuff of great drama, littered with “aha” moments. It’s Archimedes shouting, “eureka!” in the bathtub, it’s Guth writing, “spectacular realization” in his notebook, it’s Linde waking his wife to tell her, “I think I know how the universe was created.” But experiment—experiment is more like life. It’s messy and it happens gradually after a good amount of soldering and shivering and the turning of screws. Sometimes the results are null—and sometimes the results are dust—but little by little it adds up to something tangible and true.
    Never Again?

    Linde and his wife were packing their things for a Caribbean vacation.

    They needed it. They’d been working together again, writing paper after paper, producing a whirlwind of work. Linde couldn’t believe how much they’d done. Every time he had a good idea, he was convinced it would be his last.

    As people, and as physicists, they were a perfect match. Where Linde had physical intuition, Kallosh had mathematical intuition. What was difficult for one came easy for the other. They saw the universe differently, and while the process was painful, they each raised the other up in their thinking. Not that it seemed so grand in the moment. Every time they were finishing yet another paper, they’d end up shouting, “Never again!” But they’d take a break, perhaps a vacation, and then they’d start all over again. That’s just how it was in their household. Ideas were nourishment. Physics was air.

    Linde thought back to his younger days. It was funny now to think he’d ever wondered exactly what he ought to be. Now he understood that he was a theorist for the same reason an artist is an artist or a poet is a poet—because it’s too painful not to be.
    At The Door

    Kuo walked up the long driveway, the cameraman keeping pace behind him. For Kuo, the B-mode measurement was a technological achievement, the end of a marathon, the feeling of knowing that he had played an indelible part in the grand unfolding of science. But he knew that for Linde it would be something different: a moral victory, the triumph of reason and intuition, a validation 30 years coming. He was itching to tell him, he was rehearsing it in his mind. Five sigma. Clear as day. R equals 0.2. He raised his hand to knock on Linde’s door.

    Epilogue

    As of October 2014, maps made by Planck suggest that there is far more polarized dust in the Milky Way than theoretical models had predicted and that the entire B-mode signal measured by BICEP2 may be due to dust. Physicists and astronomers still need more data to determine the source of the signal and to figure out whether gravity waves are lurking behind the dust. Kuo is gearing up to head back down to the South Pole in December to set up BICEP3. The new instrument’s field of view will be three times larger than BICEP2’s and will measure light at a frequency of 95GHz. By comparing its results with BICEP2, Kuo and his team say they will be able to differentiate gravity waves from dust. As for Linde, he is hard at work incorporating inflationary theory into theories of fundamental physics, satisfied that the experimental evidence for inflation is overwhelming even in the absence of gravity waves and motivated, as ever, by the theory’s explanatory power and beauty. Science carries on.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 12:25 pm on December 5, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , , ,   

    From physicsworld: “Planck offers another glimpse of the early universe” 

    physicsworld
    physicsworld.com

    Dec 4, 2014
    Tushna Commissariat

    Results of four years of observations made by the Planck space telescope provide the most precise confirmation so far of the Standard Model of cosmology, and also place new constraints on the properties of potential dark-matter candidates. That is the conclusion of astronomers working on the €700m mission of the European Space Agency (ESA). Planck studies the intensity and the polarization of the cosmic microwave background (CMB), which is the thermal remnant of the Big Bang. These latest results will no doubt frustrate cosmologists, because Planck has so far failed to shed much light on some of the biggest mysteries of physics, including what constitutes the dark matter and dark energy that appears to dominate the universe.

    e
    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe)

    ESA Planck
    ESA Planck schematic
    ESA/Planck

    Cosmic Background Radiation Planck
    Cosmic Background Radiation per Planck

    WMAP
    NASA/WMAP spacecraft

    Cosmic Background Radiation per WMAP
    Cosmic Background Radiation per WMAP

    Planck ran from 2009–2013, and the first data were released in March last year, comprising temperature data taken during the first 15 months of observations. A more complete data set from Planck will be published later this month, and is being previewed this week at a conference in Ferrara, Italy (Planck 2014 – The microwave sky in temperature and polarization). So far, Planck scientists have revealed that a previous disagreement of 1–1.5% between Planck and its predecessor – NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) – regarding the mission’s “absolute-temperature” measurements has been reduced to 0.3%.

    Winnowing dark matter

    Planck’s latest measurement of the CMB polarization rules out a class of dark-matter models involving particle annihilation in the early universe. These models were developed to explain excesses of cosmic-ray positrons that have been measured by three independent experiments – the PAMELA mission, the Alpha Magnetic Spectrometer and the Fermi Gamma-Ray Space Telescope.

    INFN PAMELA spacecraft
    PAMELA

    AMS-02
    AMS-02

    NASA Fermi Telescope
    NASA/Fermi

    The Planck collaboration also revealed that it has, for the first time, “detected unambiguously” traces left behind by primordial neutrinos on the CMB. Such neutrinos are thought to have been released one second after the Big Bang, when the universe was still opaque to light but already transparent to these elusive particles. Planck has set an upper limit (0.23 eV/c2) on the sum of the masses of the three types of neutrinos known to exist. Furthermore, the new data exclude the existence of a fourth type of neutrino that is favoured by some models.

    Planck versus BICEP2

    Despite the new data, the collaboration did not give any insights into the recent controversy surrounding the possible detection of primordial “B-mode” polarization of the CMB by astronomers working on the BICEP2 telescope.

    BICEP 2
    BICEP 2 interior
    BICEP 2 with South Pole Telescope

    If verified, the BICEP2 observation would be “smoking-gun” evidence for the rapid “inflation” of the early universe – the extremely rapid expansion that cosmologists believe the universe underwent a mere 10–35 s after the Big Bang. A new analysis of polarized dust emission in our galaxy, carried out by Planck earlier in September, showed that the part of the sky observed by BICEP2 has much more dust than originally anticipated, and while this did not completely rule out BICEP2’s original claim, it established that the dust emission is nearly as big as the entire BICEP2 signal. Both Planck and BICEP2 have since been working together on joint analysis of their data, but a result is still forthcoming.

    [THIS IS THE BEST WE CAN DO UNTIL ESA RELEASES THEIR LATEST FINDINGS FROM PLANCK]

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 9:44 pm on December 3, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , , ,   

    From Ethan Siegel: “The Moment of Truth for BICEP2″ 

    Starts with a bang
    Starts with a Bang

    Dec 2, 2014
    Ethan Siegel

    “The paradigm of physics — with its interplay of data, theory and prediction — is the most powerful in science.” -Geoffrey West

    Earlier this year, the BICEP2 experiment shook up the world of cosmology, announcing that they had detected gravitational waves originating from before the Big Bang! Not only did they announce this, but they announced that they had done so with a signal in excess of 5σ, which is regarded as the gold standard for a detection in physics.

    BICEP 2
    BICEP 2 interior
    BICEP2 (With South Pole Telescope

    1
    Image credit: BICEP2 Collaboration — P. A. R. Ade et al, 2014 (R).

    But this may all turn out — despite the hoopla — to be absolutely nothing. Or, as it were, nothing more than a phantasm, as the observed signal may have originated from a source as mundane as our own galaxy, and have nothing to do with anything from billions of years ago!

    How did we get into this mess, and how do we get out of it? The answer to both questions is “science,” and it’s a great illustration of how the process and the body of knowledge actually evolves. Put your preconceptions of how it ought to work aside, and let’s dive in!

    2
    Image credit: ESA and the Planck Collaboration.

    This is a snapshot of the cosmic microwave background (CMB), the leftover glow from the Big Bang, as viewed by the Planck satellite. Planck has the best resolution of any all-sky map of the CMB, getting down to resolutions smaller than one tenth of a degree. The temperature fluctuations are minuscule: on the order of just a few tens of microKelvin, less than 0.01% of the actual CMB temperature.

    3
    Image credit: Wikimedia Commons user SuperManu.

    But buried in this signal is another, even more subtle one: the signal of photon polarization.

    4
    Image credit:the BICEP2 collaboration, via http://www.cfa.harvard.edu/news/2014-05.

    Basically, when photons pass through electrically charged particles in certain configurations, their polarizations — or how their electric and magnetic fields are oriented — are affected. If we look at how the two types of polarization, the E-modes and B-modes, are affected on a variety of angular scales, we ought to be able to reconstruct what caused these signals.

    2
    7
    Images credit: Amanda Yoho [Upper]; http://b-pol.org/ [Lower], of an E-mode polarization pattern at left and a B-mode pattern at right.

    A portion of this signal, in addition to charged particles, could also originate from gravitational waves created in the early Universe. There are two main classes of models of inflation that give us a Universe consistent with what we observe in all ways: new inflation, which was actually the second model (and first viable model) ever proposed, and chaotic inflation, which was the third model (and second viable one).

    9
    o
    Images credit: two inflation potentials, with chaotic inflation [Upper] and new inflation [Lower] shown. Chaotic inflation generates very large gravitational waves, while new inflation generates tiny ones. Generated by me, using google graph.

    These two models of inflation make vastly different predictions for gravitational radiation: new inflation predicts gravitational waves (and primordial B-modes) that are extraordinarily tiny, and well beyond the reach of any current or even planned experiment or observatory, while chaotic inflation predicts huge B-modes, some of the largest ones allowable. These signatures have a characteristic frequency spectrum and affect all wavelengths of light identically, so it should be an easy signal to find if our equipment is sensitive to it.

    And that’s where BICEP2 comes in.

    y
    Image credit: Sky and Telescope / Gregg Dinderman, via http://www.skyandtelescope.com/news/First-Direct-Evidence-of-Big-Bang-Inflation-250681381.html.

    Rather than measuring the whole sky, BICEP2 measured just a tiny fraction of the sky — about three fingers held together at arm’s length worth — but were able to tease out both the E-mode and B-mode polarization signals. And based on their analysis of the B-modes, which was very careful and very good, mind you, they claimed the greater-than-5σ detection.

    What this means is that they had enough data so that the odds that what they were seeing was a “fluke” of having observed just a serendipitous patch of sky was tiny, or a one in 1.7 million chance. Flukes happen all the time at the one-in-100 level or the one-in-1,000, but one-in-1.7 million flukes… well, let’s just say you don’t win the lotto jackpot very often.

    But there’s another type of error that they didn’t report. Not a statistical error, which is the kind you can improve on by taking more data, but a systematic error, which could be an effect that causes what you think is your signal, but is actually due to some other source! This type of error normally goes undetected because if you knew about it you’d account for it!

    This is exactly what happened a couple of years ago, if you remember the “faster-than-light-neutrino” business. An experiment at CERN had reported the early arrival by just a few nanoseconds of thousands upon thousands of neutrinos, meaning that they would have exceeded the speed of light by something like 0.003%, a small but meaningful amount. As it turned out, the neutrinos weren’t arriving early; there was a loose cable that accounted for the error!

    f
    Image credit: ESA / Planck Collaboration, via http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1101_planck/news1101_planck-en-print.html.

    Well, one of the things the BICEP2 team didn’t measure was the galactic foreground emission. Polarized light — including light that contains these B-modes — gets emitted by the Milky Way galaxy, and that can contaminate your signal. The BICEP2 team used a very clever trick to try and eliminate this, by interpolating unreleased Planck data about galactic foregrounds, but when the Planck team actually released their data, the foregrounds were significantly different from what BICEP2 had anticipated. And with the new Planck data, the announcement of a “discovery” needed to be walked back; the evidence was now something like a one-in-200 chance of being a fluke.

    l
    Image credit: John Kovac, viahttp://cosmo2014.uchicago.edu/depot/invited-talk-kovac-john.pdf.

    In other words, although gravitational waves could have caused this signal, so could other, far more mundane sources, including just our boring old galaxy!

    Sometime later this month, the Planck team will release their all-sky polarization results, and either at that moment or shortly thereafter, we’ll find out whether there really are gravitational waves from inflation that can be detected with our current generation of telescopes, satellites and observatories. We’ll find out whether chaotic inflation is right, or whether we need to keep searching for the gravitational wave signal from before the Big Bang. We already have the density fluctuation signal, so we can be confident that inflation happened. It’s just a question of which type.

    n
    Image credit: Bock et al. (2006, astro-ph/0604101); modifications by me.

    Stay curious, stay hungry for more knowledge, but always demand that your scientific claims be independently verified, that your possible systematic errors be checked, and that you have overwhelming evidence before believing the extraordinary claims. It’s easy to make a bold statement; it’s hard to start a bona fide scientific revolution!

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
  • richardmitnick 7:12 pm on October 21, 2014 Permalink | Reply
    Tags: , , , BICEP2, ,   

    From Daily Galaxy: “Astrophysicists Using Big Bang’s Primordial Light to Probe Largest Structures in the Universe” 

    Daily Galaxy
    The Daily Galaxy

    October 21, 2014
    The Daily Galaxy via University of California – Berkeley

    An international team of physicists has measured a subtle characteristic in the polarization of the cosmic microwave background radiation that will allow them to map the large-scale structure of the universe, determine the masses of neutrinos and perhaps uncover some of the mysteries of dark matter and dark energy. The POLARBEAR team is measuring the polarization of light that dates from an era 380,000 years after the Big Bang, when the early universe was a high-energy laboratory, a lot hotter and denser than now, with an energy density a trillion times higher than what they are producing at the CERN collider.

    Cosmic Background Radiation Planck
    CMB per Planck

    The Large Hadron Collider near Geneva is trying to simulate that early era by slamming together beams of protons to create a hot dense soup from which researchers hope new particles will emerge, such as the newly discovered Higgs boson. But observing the early universe, as the POLARBEAR group does may also yield evidence that new physics and new particles exist at ultra-high energies.

    The team uses these primordial photon’s light to probe large-scale gravitational structures in the universe, such as clusters or walls of galaxies that have grown from what initially were tiny fluctuations in the density of the universe. These structures bend the trajectories of microwave background photons through gravitational lensing, distorting its polarization and converting E-modes into B-modes. POLARBEAR images the lensing-generated B-modes to shed light on the intervening universe.

    In a paper published this week in the Astrophysical Journal, the POLARBEAR consortium, led by University of California, Berkeley, physicist Adrian Lee, describes the first successful isolation of a “B-mode” produced by gravitational lensing in the polarization of the cosmic microwave background radiation.

    Polarization is the orientation of the microwave’s electric field, which can be twisted into a “B-mode” pattern as the light passes through the gravitational fields of massive objects, such as clusters of galaxies.

    lens

    “We made the first demonstration that you can isolate a pure gravitational lensing B-mode on the sky,” said Lee, POLARBEAR principal investigator, UC Berkeley professor of physics and faculty scientist at Lawrence Berkeley National Laboratory (LBNL). “Also, we have shown you can measure the basic signal that will enable very sensitive searches for neutrino mass and the evolution of dark energy.”

    The POLARBEAR team, which uses microwave detectors mounted on the Huan Tran Telescope in Chile’s Atacama Desert, consists of more than 70 researchers from around the world. They submitted their new paper to the journal one week before the surprising March 17 announcement by a rival group, the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) experiment, that they had found the holy grail of microwave background research. That team reported finding the signature of cosmic inflation – a rapid ballooning of the universe when it was a fraction of a fraction of a second old – in the polarization pattern of the microwave background radiation.

    Huan Tran Telescope
    Huan Tran Telescope (Kavli IPMU)

    BICEP 2
    BICEP2 with South Pole Telescope

    Subsequent observations, such as those announced last month by the Planck satellite, have since thrown cold water on the BICEP2 results, suggesting that they did not detect what they claimed to detect.

    While POLARBEAR may eventually confirm or refute the BICEP2 results, so far it has focused on interpreting the polarization pattern of the microwave background to map the distribution of matter back in time to the universe’s inflationary period, 380,000 years after the Big Bang.

    POLARBEAR’s approach, which is different from that used by BICEP2, may allow the group to determine when dark energy, the mysterious force accelerating the expansion of the universe, began to dominate and overwhelm gravity, which throughout most of cosmic history slowed the expansion.

    BICEP2 and POLARBEAR both were designed to measure the pattern of B-mode polarization, that is, the angle of polarization at each point in an area of sky. BICEP2, based at the South Pole, can only measure variation over large angular scales, which is where theorists predicted they would find the signature of gravitational waves created during the universe’s infancy. Gravitational waves could only have been created by a brief and very rapid expansion, or inflation, of the universe 10-34 seconds after the Big Bang.

    In contrast, POLARBEAR was designed to measure the polarization at both large and small angular scales. Since first taking data in 2012, the team focused on small angular scales, and their new paper shows that they can measure B-mode polarization and use it to reconstruct the total mass lying along the line of sight of each photon.

    The polarization of the microwave background records minute density differences from that early era. After the Big Bang, 13.8 billion years ago, the universe was so hot and dense that light bounced endlessly from one particle to another, scattering from and ionizing any atoms that formed. Only when the universe was 380,000 years old was it sufficiently cool to allow an electron and a proton to form a stable hydrogen atom without being immediately broken apart. Suddenly, all the light particles – called photons – were set free.

    “The photons go from bouncing around like balls in a pinball machine to flying straight and basically allowing us to take a picture of the universe from only 380,000 years after the Big Bang,” Lee said. “The universe was a lot simpler then: mainly hydrogen plasma and dark matter.”

    These photons, which, today, have cooled to a mere 3 degrees Kelvin above absolute zero, still retain information about their last interaction with matter. Specifically, the flow of matter due to density fluctuations where the photon last scattered gave that photon a certain polarization (called E-mode polarization).

    “Think of it like this: the photons are bouncing off the electrons, and there is basically a last kiss, they touch the last electron and then they go for 14 billion years until they get to telescopes on the ground,” Lee said. “That last kiss is polarizing.”

    While E-mode polarization contains some information, B-mode polarization contains more, because photons carry this only if matter around the last point of scattering was unevenly or asymmetrically distributed. Specifically, the gravitational waves created during inflation squeezed space and imparted a B-mode polarization that BICEP2 may have detected. POLARBEAR, on the other hand, has detected B-modes that are produced by distortion of the E-modes by gravitational lensing.

    While many scientists suspected that the gravitational-wave B-mode polarization might be too faint to detect easily, the BICEP2 team, led by astronomers at Harvard University’s Center for Astrophysics, reported a large signal that fit predictions of gravitational waves. Current doubt about this result centers on whether or not they took into account the emission of dust from the galaxy that would alter the polarization pattern.

    In addition, BICEP2’s ability to measure inflation at smaller angular scales is contaminated by the gravitational lensing B-mode signal.

    “POLARBEAR’s strong suit is that it also has high angular resolution where we can image this lensing and subtract it out of the inflationary signal to clean it up,” Lee said.

    Two other papers describing related results from POLARBEAR were accepted in the spring by Physical Review Letters.

    One of those papers is about correlating E-mode polarization with B-mode polarization, which “is the most sensitive channel to cosmology; that’s how you can measure neutrino masses, how you might look for early behavior of dark energy,” Lee said.

    The [basically blue] image [above] shows the scale of a large quasar group” (LQG), the largest structure ever seen in the entire universe that runs counter to our current understanding of the scale of the universe. Even traveling at the speed of light, it would take 4 billion years to cross. This is significant not just because of its size but also because it challenges the Cosmological Principle, which has been widely accepted since [Albert] Einstein, the assumption that the universe, when viewed at a sufficiently large scale, looks the same no matter where you are observing it from.

    See the full article here.

    ScienceSprings relies on technology from

    MAINGEAR computers

    Lenovo
    Lenovo

    Dell
    Dell

     
  • richardmitnick 2:02 pm on September 22, 2014 Permalink | Reply
    Tags: , , , , BICEP2, , ,   

    From Symmetry: “Cosmic dust proves prevalent” 

    Symmetry

    September 22, 2014
    Kathryn Jepsen

    Space dust accounts for at least some of the possible signal of cosmic inflation the BICEP2 experiment announced in March. How much remains to be seen.

    Space is full of dust, according to a new analysis from the European Space Agency’s Planck experiment.

    planck

    That includes the area of space studied by the BICEP2 experiment, which in March announced seeing a faint pattern left over from the big bang that could tell us about the first moments after the birth of the universe.

    gwb
    Gravitational Wave Background from BICEP2

    The Planck analysis, which started before March, was not meant as a direct check of the BICEP2 result. It does, however, reveal that the level of dust in the area BICEP2 scientists studied is both significant and higher than they thought.

    “There is still a wide range of possibilities left open,” writes astronomer Jan Tauber, ESA project scientist for Planck, in an email. “It could be that all of the signal is due to dust; but part of the signal could certainly be due to primordial gravitational waves.”

    BICEP2 scientists study the cosmic microwave background, a uniform bath of radiation permeating the universe that formed when the universe first cooled enough after the big bang to be transparent to light. BICEP2 scientists found a pattern within the cosmic microwave background, one that would indicate that not long after the big bang, the universe went through a period of exponential expansion called cosmic inflation. The BICEP2 result was announced as the first direct evidence of this process.

    The problem is that the same pattern, called B-mode polarization, also appears in space dust. The BICEP2 team subtracted the then known influence of the dust from their result. But based on today’s Planck result, they didn’t manage to scrub all of it.

    How much the dust influenced the BICEP2 result remains to be seen.

    In November, Planck scientists will release their own analysis of B-mode polarization in the cosmic microwave background, in addition to a joint analysis with BICEP2 specifically intended to check the BICEP2 result. These results could answer the question of whether BICEP2 really saw evidence of cosmic inflation.

    “While we can say the dust level is significant,” writes BICEP2 co-leader Jamie Bock of Caltech and NASA’s Jet Propulsion Laboratory, “we really need to wait for the joint BICEP2-Planck paper that is coming out in the fall to get the full answer.”

    [Me? I am rooting for my homey, Alan Guth, from Highland Park, NJ, USA]

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


    ScienceSprings relies on technology from

    MAINGEAR computers

    Lenovo
    Lenovo

    Dell
    Dell

     
  • richardmitnick 11:18 am on July 11, 2014 Permalink | Reply
    Tags: , , , BICEP2, , ,   

    From BBC- “Cosmic inflation: BICEP2 and Planck to share data” 

    BBC

    3 July 2014
    Jonathan Amos

    spt
    The BICEP2 telescope studied a small patch of sky in detail above the South Pole

    Scientists on rival projects looking for evidence that the early Universe underwent a super-expansion are in discussion about working together.

    The negotiations between the US-led BICEP2 group and Europe’s Planck Collaboration are at an early stage.

    BICEP2 announced in March that its South Pole telescope had found good evidence for “cosmic inflation“.

    South Pole Telescope
    South Pole Telescope

    Cosmic Background Radiation Planck
    CMB from Planck

    But to be sure, it needs the best data on factors that confound its research – data that Planck has been compiling.

    If the two teams come to an arrangement, it is more likely they will hammer down the uncertainties.

    “We’re still discussing the details but the idea is to exchange data between the two teams and eventually come out with a joint paper,” Dr Jan Tauber, the project scientist on the European Space Agency’s Planck satellite, told BBC News.

    This paper, hopefully, would be published towards the end of the year, he added.

    dust
    Foreground dust per Planck

    The question of whether the BICEP2 team did, or did not, identify a signal on the sky for inflation has gripped the science world for weeks.

    The group used an extremely sensitive detector in its Antarctic telescope to study light coming to Earth from the very edge of the observable Universe – the famous Cosmic Microwave Background (CMB) radiation.
    Planck artist impression The Planck satellite was launched in 2009 to map the Cosmic Microwave Background

    BICEP2 looked for swirls in the polarisation of the light.

    This pattern in the CMB’s directional quality is a fundamental prediction of inflation – the idea that there was an ultra-rapid expansion of space just fractions of a second after the Big Bang.

    The twists, known as B-modes, are an imprint of the waves of gravitational energy that would have accompanied the violent growth spurt.

    But this primordial signal – if it exists – is expected to be extremely delicate, and a number of independent scientists have expressed doubts about the American team’s finding. And the BICEP2 researchers themselves lowered their confidence in the detection when they formally published their work in a Physical Review Letters paper last month.

    At issue is the role played by foreground dust in our galaxy.

    Nearby spinning grains can produce an identical polarisation pattern, and this effect must be removed to get an unambiguous view of the primordial, background signal.

    The BICEP2 team used every piece of dust information it could source on the part of the sky it was observing above Antarctica.

    What it lacked, however, was access to the dust data being compiled by the Planck space telescope, which has mapped the microwave sky at many more frequencies than BICEP2.

    This allows it to more easily characterise the dust and discern its confounding effects.
    Dust Planck released dust information close to the galactic plane in May

    In May, the Planck Collaboration published dust polarisation information gathered close to the galaxy’s centre – where the grains are most abundant.

    In a few weeks’ time, the Planck team plans to release further information detailing galactic dust in high latitude regions, including the narrow patch of the southern sky examined by BICEP2.

    And then, in late October, the Planck Collaboration is expected to say something about whether it can detect primordial B-modes.

    As Dr Tauber explained, Planck’s approach to the problem is a different one to BICEP2’s.

    “Planck’s constraints on primordial B-modes will come from looking at the whole sky with relatively low sensitivity as compared to BICEP2,” he said.

    “But because we can look at the whole sky, it makes up for some of that [lower sensitivity] at least. On the other hand, we have to deal with the foregrounds – we can’t ignore them at all.

    “At the same time, we will work together with BICEP2 so that we can contribute our data to improve the overall assessment of foregrounds and the Cosmic Microwave Background.

    “We hope to start working with them very soon, and if all goes well then we can maybe publish in the same timeframe as our main result [at the end of October].”

    See the full article here.


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 12:12 pm on June 24, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , , ,   

    From SLAC Lab: “SLAC, Stanford Scientists Play Key Roles in Confirming Cosmic Inflation” 


    SLAC Lab

    March 19, 2014
    Glennda Chui

    Chao-Lin Kuo and Kent Irwin Helped Develop Technology for Imaging Gravitational Waves

    Two scientists at Stanford University and SLAC National Accelerator Laboratory made key contributions to the discovery of the first direct evidence for cosmic inflation – the rapid expansion of the infant universe in the first trillionth of a trillionth of a trillionth of a second after the Big Bang.

    Chao-Lin Kuo is one of four co-leaders of the BICEP2 collaboration that announced the discovery on Monday. An assistant professor at SLAC and Stanford, he led the development of the BICEP2 detector and is building the BICEP3 follow-on experiment in his Stanford lab for deployment at the South Pole later this year.

    ck
    Chao-Lin Kuo at the South Pole research station where the BICEP2 experiment operated from 2010 to 2012. (Photo courtesy of Chao-Lin Kuo)

    BICEP 2
    BICEP With South Pole Telescope

    Kent Irwin invented the type of sensor used in BICEP2 as a graduate student at Stanford, adapted it for X-ray experiments and studies of the cosmos during a 20-year career at the National Institute for Standards and Technology, and returned to SLAC and Stanford as a professor in September to lead a major initiative in sensor development.

    ki
    Kent Irwin (Matt Beardsley/SLAC)

    Both are members of the Kavli Institute for Particle Physics and Astrophysics (KIPAC), which is jointly run by SLAC and Stanford.

    “It’s exciting that the same technology I developed as a grad student to search for tiny particles of dark matter is also being used to do research on the scale of the universe and to study the practical world of batteries, materials and biology in between,” Irwin said. His group is working toward installing a version of the BICEP2 sensors at SLAC’s X-ray light sources – Stanford Synchrotron Radiation Lightsource (SSRL) and Linac Coherent Light Source (LCLS) – as well as at a planned LCLS upgrade.

    Searching for Ripples in Space-time

    BICEP is a series of experiments that began operating at the South Pole in January 2006, taking advantage of the cold, clear, dry conditions to look for a faint, swirling polarization of light in the Cosmic Microwave Background (CMB) radiation. The light in the CMB dates back to 380,000 years after the Big Bang; before that, the early universe was opaque and no light could get through.

    Cosmic Background Radiation Planck
    CMB Planck

    But some theories predicted that gravitational waves – ripples in space-time – would have been released in the first tiny fraction of a second after the Big Bang, as the universe expanded exponentially in what is known as “cosmic inflation.” If that were the case, scientists might be able to detect the imprint of those waves in the form of a slight swirling pattern known as “B-mode polarization” in the CMB.

    On Monday, researchers from the BICEP2 experiment, which ran from January 2010 through December 2012, announced that they had found that smoking-gun signature, confirming the rapid inflation that had been theorized more than 30 years ago by Alan Guth and later modified by Andrei Linde, a Russian theorist who is now at Stanford.

    Building a Better Detector

    Kuo started working on BICEP1 as a postdoctoral researcher at Caltech in 2003. The circuitry in the experiment’s detectors was all made by hand. For the next-generation detector, BICEP2, the collaborating scientists wanted something that could be mass-produced in larger quantities, allowing them to pack more sensors into the array and collect data 10 times faster. So Kuo also started designing that technology, which used photolithography – a standard tool for making computer chips – to print sensors onto high-resolution circuit boards.

    sunset
    The sun sets behind BICEP2 (in the foreground) and the South Pole Telescope (in the background). (Steffen Richter, Harvard University)

    b2
    The BICEP2 detector shown in this electron-beam micrograph works by converting the light from the cosmic microwave background into heat. A titanium film tuned on its transition to a superconducting state makes a sensitive thermometer to measure this heat. The sensors are cooled to just 0.25 degrees above absolute zero to minimize thermal noise. (Anthony Turner, JPL)

    In 2008 Kuo arrived at SLAC and Stanford and began working on the next-generation experiment, BICEP3, for which he is principal investigator. Scheduled for deployment at the South Pole later this year, BICEP3 will look at a larger patch of the sky and collect data 10 times faster than its predecessor; it’s also more sensitive and more compact.

    SLAC took on a bigger role in this research in October 2013 by awarding up to $2 million in Laboratory Directed Research and Development funding over three years for the “KIPAC Initiative for Cosmic Inflation,” with Kuo as principal investigator. The grant establishes a large-scale Cosmic Microwave Background program at the lab, with part of the funding going toward BICEP3, and has a goal of establishing KIPAC as a premier institute for the study of cosmic inflation. There are also plans to establish a comprehensive development, integration, and testing center at SLAC for technologies to further explore the CMB, which holds clues not only to gravitational waves and cosmic inflation but also to dark matter, dark energy and the nature of the neutrino.

    A Fancy Thermometer for Tiny Signals

    Kent Irwin entered the picture in the early 1990s, while a graduate student in the laboratory of Stanford/SLAC Professor Blas Cabrera. There he invented the superconducting Transition Edge Sensor, or TES, for the Cryogenic Dark Matter Search, which is trying to detect incoming particles of dark matter in a former iron mine in Minnesota. When he moved to NIST, he and his team adapted the technology for other uses and also developed a very sensitive way to read out the signal from the sensors with devices known as SQUID multiplexers.

    Printing TES devices on circuit boards and using the SQUID multiplexers to read them out made it possible to create large TES arrays and greatly expanded their applications in astronomy, nuclear non-proliferation, materials analysis and homeland defense. It was also the key factor in allowing the BICEP team to expand the number of detectors in its experiments from 98 in BICEP1 to 500 in BICEP2, and opens the path to even larger arrays that will greatly increase the sensitivity of future experiments.

    A TES is “basically a very fancy thermometer,” Irwin says. “We’re measuring the power coming from the CMB.” The TES receives a microwave signal from an antenna and translates it into heat; the heat then warms a piece of metal that’s chilled to the point where it hovers on the edge of being superconducting – conducting electricity with 100 percent efficiency and no resistance. When a material is at this edge, a tiny bit of incoming heat causes a disproportionately large change in resistance, giving scientists a very sensitive way to measure small temperature changes. The TES devices for BICEP2 were built at NASA’s Jet Propulsion Laboratory, and Irwin’s team at NIST made the SQUID multiplexers.

    The Road Ahead

    Looking ahead, CMB researchers in the United States developed a roadmap leading to a fourth-generation experiment as part of last year’s Snowmass Summer Study, which lays out a long-term direction for the national high energy physics research program. That experiment would deploy hundreds of thousands of detector sensors and stare at a much broader swath of the cosmos at an estimated cost of roughly $100 million.

    “These are incredibly exciting times, with theory, technology and experiment working hand in hand to give us an increasingly clear picture of the very first moments of the universe,” said SLAC Lab Director Chi-Chang Kao. “I want to congratulate everyone in the many collaborating institutions who made this spectacular result possible. We at SLAC are looking forward to continuing to invest and work in this area as part of our robust cosmology program.”

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 12:22 pm on April 23, 2014 Permalink | Reply
    Tags: , , , BICEP2,   

    From Symmetry: “A ‘crack in the cosmic egg'” 

    Symmetry

    April 23, 2014
    This article is based on a Kavli Foundation press release.

    Last month, scientists on the BICEP2 experiment announced the first hard evidence for cosmic inflation, the process by which the infant universe swelled from microscopic to cosmic size in an instant.

    BICEP 2
    BICEP2 and the South Pole Telescope

    Scientists have thought for more than three decades that we might someday find such a signal, so the discovery was not entirely unexpected. What was unexpected, however, was just how strong the signal turned out to be.

    “The theoretical community is abuzz,” theorist Michael Turner, director of the Kavli Institute for Cosmological Physics and a University of Chicago professor, said in a recent discussion. “We got the signal we were looking for—that’s good—but we shouldn’t have gotten one according to the highbrow theorists because they say it should be too small. So we got a surprise. And often in science, that’s the case. We like to the experimenters to find what we predict, but we also like surprises.”

    The BICEP2 experiment—the second generation of the Background Imaging of Cosmic Extragalactic Polarization experiment—consists of a telescope at the South Pole (pictured above, on left) built to look back to the universe’s first light.

    Turner moderated a conversation, broadcast as a Google+ Hangout, about the result with BICEP2 postdoctoral researcher Walter Ogburn of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University; KICP Deputy Director John Carlstrom, who leads two other experiments that study the early universe; and BICEP2 physicist Abigail Vieregg, a professor at the University of Chicago and KICP.

    The BICEP2 surprise is still so new that additional implications keep coming to light each week. It’s already clear that the result rules out many theoretical models of inflation—most of them, in fact—because they predict a signal much weaker than the one detected. In addition, the discovery also seems to disprove a theory that says that the universe expands, collapses and expands again in an ongoing cycle.

    “It’s a funny thing when you’re on the inside of a discovery like this,” Vieregg said during the Google+ Hangout. “It’s only when you release the results to the world and watch the reaction of the community that, at least for me, it really hits home how important it is. If this is what we think it is, it’s a very big deal.”

    Turner said the result could very well be a “crack in the cosmic egg,” offering clues that even the most accepted theoretical assumptions contain inaccuracies.

    “Maybe we need to… allow some new physics in there,” Carlstrom said. “Maybe there are more neutrinos. Maybe they’re more massive than we thought. Or maybe it’s something none of us have thought of yet.”

    Theorists will carefully consider these ideas and their implications over the coming months and years. Meanwhile, the signal still needs to be experimentally confirmed.

    Results from other telescopes, including the Planck satellite and the South Pole Telescope, are expected in the coming year. After that, the next step will be to measure the signal’s intricacies, searching for evidence of how inflation started and how exactly the universe worked in its high-energy infancy. Those results, in turn, may shed light on some of our biggest questions about how the universe began and how the forces of nature are unified.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 12:15 pm on March 25, 2014 Permalink | Reply
    Tags: , , , BICEP2, ,   

    From Berkeley Lab: “Setting a Trap for Gravity Waves” 


    Berkeley Lab

    March 18, 2014
    Paul Preuss paul_preuss@lbl.gov

    In 1996 Uros Seljak was a postdoc at Harvard, contemplating ways to extract information from the cosmic microwave background (CMB). The distribution of anisotropies, slight temperature differences, in the CMB had much to say about the large-scale structure of the universe. If it were also possible to detect the polarization of the CMB itself, however, a much wider window would be opened – polarization could even reveal the tracks of gravitational waves.

    Cosmic Background RadiationXMM Newton
    CMB from ESA/Planck

    Gravitational waves are distortions of space on a small scale, and have no consequence for the large-scale structure of the universe,” says Seljak, now a professor of physics and astronomy at UC Berkeley and a faculty scientist in Berkeley Lab’s Physics Division. “Both result from perturbations during inflation, but the seeds of large-scale structure are described by a scalar field, and gravitational waves by a tensor field.”

    Cosmologists already assumed that inflation theory was essentially correct: virtually instantaneous expansion after the big bang explained how regions of the universe never otherwise in contact had in fact started from the same initial conditions. Here was a way to test inflation directly.

    Seljak posted a paper to arXiv (soon published in the Astrophysical Journal), becoming the first to predict how polarization could be used to find CMB tensor signals, including gravitational waves. Marc Kamionkowski, Arthur Kosowsky, and Albert Stebbins of Fermilab independently posted their similar proposal shortly thereafter. In further work with Matias Zaldarriaga, Seljak named the E and B modes of CMB polarization, borrowing the symbols for light’s electric and magnetic fields – scalar fields produce E-mode polarization; a gravitational tensor field can produce both.

    Fast forward to the year 2000, when Adrian Lee, a professor of astrophysics at UC Berkeley and faculty scientist in the Lab’s Physics Division, came up with the idea of suspending the recently invented transition-edge sensor bolometer(TES), creating what he describes as “a trampoline that heats up when an energy pulse lands on it” – the more energy, the bigger the reaction.

    Lee integrated suspended TESs with other functions in flat chips suitable for the focal planes of CMB telescopes. He proposed just such a telescope, the POLARBEAR experiment, initiated with support from Berkeley Lab’s Laboratory Directed Research and Development (LDRD). BICEP2 and many other CMB telescopes also use versions of these focal-plane chips.

    BICEP 2
    BICEP2 at the South Pole Telescope

    On Monday, March 17, 2014, the BICEP2 collaboration grabbed the brass ring: first detection of B-mode polarization from gravitational waves, thus first direct evidence of inflation – a signal far stronger than most scientists had expected.

    “We look forward to working with BICEP2 to refine their measurements,” says Lee. “Until now, the best evidence for inflation was a slight ‘tilt’ in the CMB scalar field. POLARBEAR’s higher resolution could detect a similar tilt in the tensor field, a double confirmation of inflation.”

    Among the many implications of the large B-mode signal, says Seljak: “It may force us in the direction of string theory. It also fits in with models of continuing inflation that produce multiple universes.”

    Berkeley Lab has played an important part in opening the cosmic frontier to even wider vistas.

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal


    ScienceSprings is powered by MAINGEAR computers

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
Follow

Get every new post delivered to your Inbox.

Join 454 other followers

%d bloggers like this: