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  • richardmitnick 8:05 am on September 14, 2015 Permalink | Reply
    Tags: , Big Bang Science, ,   

    From COSMOS- “New model of the cosmos: a Universe that begins again” 

    Cosmos Magazine bloc


    14 Sep 2015
    Michael D. Lemonick

    The failure so far to find gravitational waves has some cosmologists wondering if the ‘inflationary’ theory of the Big Bang is right. Michael D. Lemonick explains.

    On 17 March, 2014, the Harvard-Smithsonian Centre for Astrophysics held a press conference to announce “a major discovery”. It was not an exaggeration. A team of astrophysicists had detected evidence of gravitational waves from a time when the Universe was almost indescribably young.

    Gravitational Wave Background
    Representation of possible gravitational waves from BICEP2

    BICEP 2

    It was the most powerful confirmation yet of the 30-year-old theory of inflation which explains why the cosmos looks the way it does. The distribution of galaxies, the relative proportions of ordinary matter and dark matter3, the curvature of space-time, the fact that the cosmos looks essentially the same no matter where you look – all of this can be understood if you assume that the entire visible Universe expanded for the briefest interval from something about the size of a proton to something about the size of a grapefruit at faster than the speed of light when it was less than a billionth of a trillionth of a trillionth of a second old. In the words of University of California, Santa Cruz, cosmologist Joel Primack: “No theory this beautiful has ever been wrong.”

    Evidently, it had been proven right. Using an exquisitely sensitive microwave telescope known as BICEP2 located at the South Pole, Harvard’s John Kovac and a team of observers had detected a twist in the orientation of microwaves generated about 300,000 years after the Big Bang. Known as B-mode polarisation, it had been predicted by inflation theory. The fantastic energy released by an inflating Universe would have rippled space-time itself.

    Alternative theories about how the Universe got its structure – such as the one developed by Princeton University’s Paul Steinhardt – did not predict these ripples. “If this is correct, we’re finished,” Steinhardt commented. He had been one of the pioneers of inflation theory but had since abandoned it in favour of his own competing theory.

    The swirls detected in this picture of the Milky Way were initially believed to be caused by gravitational waves, but later measurements showed cosmic dust could create the same effect.Credit: ESA / Planck Collaboration

    ESA Planck
    ESA PLanck

    The announcement at the Harvard press conference reverberated in headlines around the world. “Space Ripples Reveal Big Bang’s Smoking Gun,” trumpeted the New York Times. “Primordial gravitational wave discovery heralds ‘whole new era’ in physics,” declared the Guardian. Like virtually every other story that appeared on that day, there were dutiful caveats along the lines of “The results will require confirmation …” They barely dented the feverish tone.

    Within days of the announcement the reporters were wishing they’d been more than merely dutiful. Kovac’s scientific report (revealed online on arXiv – a forum for work to be published soon) wasn’t released until the press conference. Once other astrophysicists got a look at it, they became suspicious. Primordial gravitational waves aren’t the only thing that could polarise microwaves. The Milky Way’s swirling dust clouds could do it too – “schmutz”, Princeton’s David Spergel called it, using a Yiddish word meaning “dirt.”

    As independent physicists scrutinised the report more closely, they became increasingly sceptical as to whether the Harvard team had seen gravitational waves at all. Finally in February 2015, a combined analysis of the data from Kovac’s BICEP2 team; the Keck Array (located next to BICEP2 at the South Pole); and Planck, the European Space Agency’s orbiting space observatory, left the researchers in no doubt. “What we see”, Kovac conceded “is compatible with no inflationary gravitational waves”.

    Keck Array
    Keck Array

    That hardly means that inflation is dead. What these three very sensitive instruments saw is also compatible with inflationary gravitational waves hiding within the dust. Inflation, moreover, isn’t a single theory: it’s a class of theories, and many predict gravitational waves 10 orders of magnitude lower than any existing instrument is capable of detecting. “Am I worried?” asks Stanford University theorist Andrei Linde, one of the founders of inflation theory. “Why should I be?”

    But for a small number of theoretical astrophysicists, the failure to detect gravitational waves raises the stock for an alternative theory of the birth of the Universe. Known as the cyclic model, it was first proposed in 2003 by Princeton’s Steinhardt and Neil Turok, then at the University of Cambridge (now director of Canada’s Perimeter Institute for Theoretical Physics). These days it is championed by a handful of theorists mostly in the US and the UK. It posits that the observable Universe has gone through alternating phases of expansion and contraction – perhaps forever.

    This model of cosmology explains everything we know about the Universe just as well as inflation does, they say. A major point of departure though, is that primordial gravitational waves are not part of the cyclical model.

    While most physicists are not even close to abandoning inflation, they don’t rule out that this beautiful theory may also be wrong. “Paul has a bunch of concerns about the inflation theory, which I think are valid,” says Charles Bennett, an experimental physicist at Johns Hopkins University.

    Joanna Dunkley, a cosmologist at the University of Cambridge, agrees the failure to detect gravitational waves “should make us think more seriously about whether inflation is the only option”.

    “I think most of the community is focused on inflationary models, and I think some of that is fashion,” adds David Spergel, Steinhardt’s Princeton colleague.

    Neil Turok argues the case for a cyclic view of the Universe.Credit: Peter Power

    Fashion explains some of their focus, perhaps, but hardly all of it. When inflation theory first emerged in the 1980s, it was nothing short of breathtaking in the way it explained a series of problems that had bedevilled cosmologists since the 1964 discovery of the cosmic microwave background (CMB) radiation.

    Cosmic Background Radiation Planck
    CMB per Planck

    At the time, there were two competing theories about how the Universe began. One was the Steady State, which posited that the Universe has always been expanding, and that new matter is created to fill in the gaps as existing matter spreads apart.

    The other was the Big Bang, ironically coined by English astronomer Sir Fred Hoyle as a term of ridicule – he was the leading proponent of the Steady State. The original idea here was that the Universe was born out of the violent expansion of an extremely dense, hot gas cloud (a modern version holds that it began from a singularity – a pinpoint of sub-atomic proportions) which has been expanding ever since. If that were true, then the brilliant light generated by that bang should still be echoing through the Universe – except the expansion of the Universe would have stretched the light into the microwave region of the electromagnetic spectrum.

    Paul Steinhardt is another insurgent challenging the theory of inflation.Credit: Beverly Schaefer

    In 1964, radio astronomers Arno Penzias and Robert Wilson at the Bell Telephone Laboratories in New Jersey, stumbled across that stretched ancient light. They were experimenting with Bell Lab’s giant radio antenna – originally built to track satellites – to see if they could repurpose it to peer at the Universe.

    Robert Woodrow Wilson (left) with Arno Allan Penzias at the Bell Labs giant radio antenna

    Annoyingly, their efforts were thwarted by a mysterious microwave frequency hiss in the antenna. When the meticulous pair had ruled out all other explanations (including pigeon poop) they suggested the hiss was cosmic in origin. Around the same time, just an hour’s drive to the west, Robert Dicke and several other physicists at Princeton University were setting out to look for relic microwaves from the Big Bang. Penzias and Wilson heard about Dicke’s project and called during one of his group meetings. As those who were present recall, Dicke listened patiently, hung up and said “boys, we’ve been scooped”.

    Both groups published simultaneously in The Astrophysical Journal in 1965 (only Penzias and Wilson got the Nobel, however). The discovery tipped the scales firmly in favour of the Big Bang.

    Cosmologists leapt at the opportunity to study the CMB in detail – it was the first glimpse of our youthful, 400,000-year-old Universe. It turned out to be a mysterious place. For one thing, they were struck by its uncannily uniform temperature – it hovers at 2.725° above absolute zero, varying by no more than one part in 100,000 in either direction, no matter where in the sky you look. The turbulent super-heated gas cloud from which the Universe erupted would have had spots that varied significantly in temperature and density and some of that messiness should have been on show in the structure of the early expanded Universe.

    Another problem was that while the strapping 400,000-year-old Universe was as smooth and even as a baby’s bottom, the mature universe is wrinkled with features such as galaxies. But how did these age-related wrinkles arise?

    Physicists were also worried by the apparent topology of the early Universe. Over large scales, their measurements showed that it appeared to be geometrically “flat”. And it was unclear why monopoles – particles with either a north or south magnetic charge but not both – had never been found.

    Cosmologists scratched their heads for more than a decade. Then in 1980 a young physicist named Alan Guth figured out these conundrums would vanish if a proton-sized Universe experienced an ultra-fast expansion in its very earliest moments.

    Alan Guth

    A proton-sized beginning that suddenly inflated would explain the evenness of the Universe. It would have ballooned out so fast there was no time for any fluctuations to wrinkle the expanding fabric of space-time.

    On the other hand, the fact that the entire Universe was once sub-atomic in size made it subject to quantum effects such as “uncertainty” – a state in which physical variables can fluctuate unpredictably. These random quantum fluctuations seeded the wrinkles that gave rise to features such as galaxies.

    Finally, inflation explained why the visible cosmos appears so flat. Perhaps it started off with significant curvature like the surface of a balloon. Imagine that you’re a fly balancing on the ball. Suddenly, it expands to the size of the Sun. You’re still standing on a curved surface, but to you it now looks utterly flat as far as the eye can see. Without the rapid expansion, the balloon wouldn’t have expanded sufficiently to create the flatness we observe.

    Guth’s original version of inflation left some gaps but they were filled by Linde, turning the theory into a robust set of predictions that cosmologists have been testing ever since.

    There was a problem, however.

    “We discovered early on that we completely misunderstood something at the beginning,” says Steinhardt, who was one of the pioneers of inflation theory. “We thought that inflation was essentially a story about stretching the Universe. And then we thought if you add a little bit of quantum mechanics to explain why the Universe isn’t perfectly uniform” – why it has galaxies and clusters of galaxies – “we seem to have a consistent story”.

    However, there’s no such thing as a little bit of quantum mechanics, says Steinhardt. “Quantum physics is constantly producing fluctuations in all forms of energy, including the energy that’s driving inflation, so that it ends in some places a little bit later than others,” he says.

    He and others soon realised that quantum uncertainty complicated matters.

    In our patch of the Universe, for instance, inflation stopped billions of years ago, but in some other patches it’s still going on. Given inflation’s breakneck expansion rate, these regions would now be unimaginably large – as though bits of the original balloon had bulged outward to form gigantic protuberances, much larger than the original. “This will occur over and over and over again,” Steinhardt explains. Linde, who is mostly responsible for this idea, calls it “chaotic inflation” or “eternal inflation”. It means that our own visible Universe is just one patch in a far larger multiverse – a patch within a patch within a patch, ad infinitum – and each patch could have its own unique laws of physics. “The multiverse will explore every conceivable physical property and possibility and produce every conceivable outcome,” says Steinhardt.

    And that’s the problem. “What can you predict from such a theory?” Steinhardt asks. “Nothing. Literally nothing, since anything that’s physically possible will occur.” But it’s worse than that: since an infinite number of patches exist with an infinite variety of physical laws and constants, the fundamental question that physicists have been trying to answer since the time of Aristotle – why is the Universe the way it is? – becomes meaningless. It’s the way it is because the Universe is every possible way all at once. Ours happens to look the way it does because that’s the part we happen to be living in. This is what’s known as the anthropic principle, and since it says in essence that there’s no explanation for anything, it pulls the rug out from under science. That doesn’t make it wrong, but physicists tend to abhor it.

    There’s a second problem as well. “It’s remarkable that we have a theory that can describe what’s going on and match the observations so beautifully,” says Spergel. “But it doesn’t explain how it got into that phase.” In other words inflation might have happened but nobody knows why it started. Inflationary theorists say that’s a problem to be solved later, says Steinhardt. “But it’s a big problem to be solved later,” he says, “because we’ve been trying to solve that problem and we think the conditions under which inflation could begin are very, very rare.” Unless you believe in a Creator, that’s not a good place to be.

    There was a third problem: dark energy. In 1999 cosmologists confirmed that this mysterious force is ballooning out the Universe at an ever-accelerating rate. Inflation theory, conceived in the 1980s, was blissfully unaware of dark energy.

    “It was a total surprise,” says the Perimeter Institute’s Turok. “Inflation was already something of an artificial add-on to the Big Bang, and now you’ve got this new add-on, which has nothing to do with inflation.” Turok says you also have to account for the fact that inflation dominated the earliest moments of our part of the Universe, then went away – and that dark energy (tiny compared with the energy of inflation) would emerge billions of years later to dominate the Universe.

    Inflationists consider dark energy to be something entirely different from inflation – a second expansionary force that only became significant many billions of years after inflation ran out of steam. The fact that you need to explain not one, but two different forces makes Steinhardt and Turok uncomfortable with the inflation model. “It’s horribly fine-tuned,” says Turok.

    For this pair of physicists, dark energy had finally robbed inflationary theory of its beautiful shine. There had to be a simpler, better theory. After several years of intensive work, they came up with the cyclic model.

    In the cyclic model, dark energy doesn’t suddenly turn off after the creation of the Universe and then return. Instead, it is dark energy – which we can observe as opposed to inflation which is theoretical – that drives the initial expansion of the Universe and continues the process, strengthening as the Universe ages.

    Ultimately it also reverses direction, a possibility that other theorists had considered even before the cyclic Universe scenario was proposed. The reversal takes a long time – perhaps as much as 10500 years. But eventually the Universe collapses to a tiny size (the model doesn’t specify precisely how small, but it’s far larger than inflation calls for). Then the dark energy reverses direction again, the Universe begins to expand, and a new cycle bounces into being. “In this model,” Turok says, “there is no inflation, and dark energy isn’t a bizarre add-on: it’s essential.”

    By positing a Universe that expands for many billions of years, then contracts then expands again, perhaps infinitely many times, Steinhardt’s and Turok’s theory addresses many of the same mysteries inflation appeared to solve.

    For example, because the cosmos has gone through many, many cycles, it has had ample time for different regions to have come into temperature equilibrium, so there’s no problem with the fact that opposite sides of the visible Universe look essentially the same. And the topological “flatness” of the visible Universe might emerge not from ultra-fast expansion but from the effect of dark energy during the contraction. Precisely how the reversal happens is something Turok and Steinhardt haven’t worked out yet. “There’s a lot of effort in the field right now,” says Steinhardt, “different approaches for thinking about these bounces, but they all have the feature that they are continuous processes, meaning there can’t be anything too crazy that happens as you’re going through them”– for example, nothing as crazy as the singularity where density becomes infinite and physics breaks down – a state that appears inevitable if the Universe expands only once.

    While both physicists are convinced that the cyclic theory is more straightforward and plausible than the inflationary model, they realise their arguments won’t be enough to wean their colleagues away from inflation. Both theories match existing observations very well, and neither Steinhardt nor Turok is prepared to say the cyclic model is clearly better at this point. But there’s one observation that could decide between them. Gravitational waves are predicted by inflation; cyclic models say they shouldn’t exist.

    If the BICEP2 telescope had actually found the signal its scientists claimed last spring, that would have been the end of the road for Steinhardt’s ideas. The fact that it didn’t, he says, should inspire other physicists and astrophysicists to take another look at cyclic models.

    For Steinhardt, cosmology is experiencing a challenge akin to that faced by planetary astronomers of the mid-1500s. Ptolemy’s Earth-centred Solar System was the reigning view but contested by Copernicus’ Sun-centered theory. “Copernicus could explain some things conceptually that Ptolemy couldn’t”, says Steinhardt, “and vice versa”. It was only when Kepler realised the planets follow elliptical rather than circular paths that Copernicus’ model pulled ahead. In Steinhardt’s view this is a Kepler moment.

    Most physicists aren’t quite ready for that. “It’s still possible with the BICEP2 and Planck data that there could be a whopping great gravitational wave signature,” says Cambridge’s Joanna Dunkley. “It’s not that BICEP2 has got no signal at all, it’s just the signal is much more likely to be dust than the Big Bang.” As observers continue to refine their observations of the dust, however, it will become easier for them to subtract the dust signal electronically and see if there are any truly primordial polarised microwaves hiding behind it – much as they do now when observing vanishingly dim galaxies through the Earth’s atmosphere.

    And even if no inflation signal emerges out of the dust, the waves could well be out there but beyond the limits of current detectors to find them. “There’s a very large spectrum of possibilities for the intensity of those gravity waves,” says Guth.

    That could change over the next few years, however, as Planck satellite data continues to be analysed and as other ground-based CMB detectors continue their watch for signals from the ancient Universe. They include the balloon-borne SPIDER detector, which just completed a loop around Antarctica; the Atacama Cosmology Telescope, the POLARBEAR experiment and the Cosmology Large Angular Scale Surveyor in Chile; the South Pole Telescope; the Harvard group’s Keck Array, and more. All of them are looking for polarised light – some scanning larger patches of sky in less detail, others looking at small patches more intensively. “A lot of people are thinking up new ways to measure this very, very tiny signal,” says Lyman Page, Steinhardt’s Princeton colleague “and we’ve been thinking about it for years”.

    Princeton Atacama Technology Telescope
    Princeton Atacama Cosmology Telescope

    POLARBEAR McGill Telescope
    POLARBEAR Telescope

    Cosmology Large Angular Scale Surveyor
    Cosmology Large Angular Scale Surveyor

    South Pole Telescope
    South Pole Telescope

    Each instrument will make valuable observations in its own right, says Bill Jones, a Princeton physicist who works with the SPIDER experiment. “It’s sort of like a force multiplier in the sense that we can take advantage of the different strengths that they have in order to really nail the signal,” he says.

    Like most of his colleagues, Jones acknowledges that the cyclic models are interesting –even intriguing. But he adds: “I think that when the average cosmologist wakes up in the morning, he or she probably still thinks something like inflation happened.”

    Steinhardt, Turok and the other crusaders for the cyclic model are fine with that. For now.

    See the full article here .

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  • richardmitnick 2:41 pm on February 26, 2015 Permalink | Reply
    Tags: , Big Bang Science,   

    From livescience: “Big Bang, Deflated? Universe May Have Had No Beginning” 


    February 26, 2015
    Tia Ghose


    If a new theory turns out to be true, the universe may not have started with a bang. In the new formulation, the universe was never a singularity, or an infinitely small and infinitely dense point of matter. In fact, the universe may have no beginning at all. “Our theory suggests that the age of the universe could be infinite,” said study co-author Saurya Das, a theoretical physicist at the University of Lethbridge in Alberta, Canada. The new concept could also explain what dark matter — the mysterious, invisible substance that makes up most of the universe — is actually made of, Das added.

    Big Bang under fire

    According to the Big Bang theory, the universe was born about 13.8 billion years ago. All the matter that exists today was once squished into an infinitely dense, infinitely tiny, ultra-hot point called a singularity. This tiny fireball then exploded and gave rise to the early universe. The singularity comes out of the math of Einstein’s theory of general relativity, which describes how mass warps space-time, and another equation (called Raychaudhuri’s equation) that predicts whether the trajectory of something will converge or diverge over time. Going backward in time, according to these equations, all matter in the universe was once in a single point — the Big Bang singularity.

    But that’s not quite true. In Einstein’s formulation, the laws of physics actually break before the singularity is reached. But scientists extrapolate backward as if the physics equations still hold, said Robert Brandenberger, a theoretical cosmologist at McGill University in Montreal, who was not involved in the study. “So when we say that the universe begins with a big bang, we really have no right to say that,” Brandenberger told Live Science. There are other problems brewing in physics — namely, that the two most dominant theories, quantum mechanics and general relativity, can’t be reconciled. Quantum mechanics says that the behavior of tiny subatomic particles is fundamentally uncertain. This is at odds with Einstein’s general relativity, which is deterministic, meaning that once all the natural laws are known, the future is completely predetermined by the past, Das said.

    And neither theory explains what dark matter, an invisible form of matter that exerts a gravitational pull on ordinary matter but cannot be detected by most telescopes, is made of.

    Quantum correction

    Das and his colleagues wanted a way to resolve at least some of these problems. To do so, they looked at an older way of visualizing quantum mechanics, called Bohmian mechanics. In it, a hidden variable governs the bizarre behavior of subatomic particles. Unlike other formulations of quantum mechanics, it provides a way to calculate the trajectory of a particle. Using this old-fashioned form of quantum theory, the researchers calculated a small correction term that could be included in Einstein’s theory of general relativity. Then, they figured out what would happen in deep time.

    The upshot? In the new formulation, there is no singularity, and the universe is infinitely old.

    A way to test the theory

    One way of interpreting the quantum correction term in their equation is that it is related to the density of dark matter, Das said. If so, the universe could be filled with a superfluid made of hypothetical particles, such as the gravity-carrying particles known as gravitons, or ultra-cold, ghostlike particles known as axions, Das said. One way to test the theory is to look at how dark matter is distributed in the universe and see if it matches the properties of the proposed superfluid, Das said. “If our results match with those, even approximately, that’s great,” Das told Live Science.

    However, the new equations are just one way to reconcile quantum mechanics and general relativity. For instance, a part of string theory known as string gas cosmology predicts that the universe once had a long-lasting static phase, while other theories predict there was once a cosmic “bounce,” where the universe first contracted until it reached a very small size, then began expanding, Brandenberg said.

    Either way, the universe was once very, very small and hot.

    “The fact that there’s a hot fireball at very early times: that is confirmed,” Brandenberg told Live Science. “When you try to go back all the way to the singularity, that’s when the problems arise.”

    The new theory was explained in a paper published Feb. 4 in the journal Physical Letters B, and another paper that is currently under peer review, which was published in the preprint journal arXiv.

    See the full article here.

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  • richardmitnick 11:53 am on February 14, 2015 Permalink | Reply
    Tags: , , Big Bang Science, ,   

    From Ethan Siegel: “How can we still see the Big Bang?” 

    Starts with a bang
    Starts with a Bang

    Feb 14, 2015
    Ethan Siegel

    If it happened billions of years ago, what’s it still doing here?

    “We like to admit to only that which already glows, although it is nobler to support brightness before it glows, not afterwards.” –Dejan Stojanovic

    Sometimes, the simplest questions make for the most profound answers, and give us the opportunity to really dig deep into how we view the fabric of the Universe itself. This week, after sifting through your questions and suggestions for our Ask Ethan column, I couldn’t pass up the spectacular but straightforward question of Joseph McFarland, who wants to know:

    Why do we continue to detect the cosmic background radiation?
    Is the fact that we continue to eternally see the cosmic background radiation billions of years after it was generated proof of either inflation, or that the universe must be curved back upon itself (i.e. that it is finite but unbounded)?
    Or if neither of these are requirements, then what are other explanations?

    I want you to think about the history of the Universe.

    Image credit: NASA / CXC / M.Weiss.

    In particular, I want you to think of why it’s such a remarkable thing that we do detect the Cosmic Microwave Background at all. The story starts at the moment of the Big Bang, or more specifically, at the hot Big Bang.

    Image credit: RHIC collaboration, Brookhaven, via http://www.bnl.gov/newsroom/news.php?a=11403.

    The hot Big Bang refers to a time some 13.8 billion years ago, when the Universe first emerged from an inflationary state — one where all the energy in it was inherent to space itself — and got converted into matter, antimatter and radiation. We can think of this as inflation being a field that’s in an unstable state, like a ball at the top of a hill, that then rolls down that hill and into a valley.

    While the ball is at the top of the hill, space itself expands at an exponential rate. When the ball rolls into the valley, and starts oscillating back-and-forth, that energy-of-space gets converted into matter, antimatter and radiation: a process known as reheating.

    Image credit: E. Siegel. Inflation ends when the ball rolls into the valley.

    The Universe still continues to expand, but because it’s filled with matter, antimatter and radiation, it no longer maintains a very large expansion rate for long. The expansion rate is tied — in General Relativity — to the energy density of the Universe, or how much energy there is per-unit-volume.

    When all you had was energy inherent to space itself, as the Universe expanded, you simply made more empty space, and the energy density stayed the same. But now that you’ve got stuff in the Universe instead, it dilutes (and gets less dense) as the Universe expands. In the case of radiation, the wavelength of light also stretches, which is why the Universe not only gets less dense, it also cools as time goes on.

    Images credit: TAKE 27 LTD / Science Photo Library, via Nature {above], Chris Palma of Penn State / Chaisson and McMillan, Astronomy [below].

    As the Universe expands and cools, from an incredibly hot, dense, uniform, rapidly expanding state down to a cool, sparse, clumpy, slowly expanding state, a huge number of important events happen:

    The fundamental symmetries of nature that are restored at the highest energies become broken, giving rise to things like particle rest masses.
    The Universe gets cool enough so that photons stop spontaneously forming matter/antimatter pairs. The excess antimatter annihilates away, leaving only 1 matter particle per ~1,400,000,000 photons.
    The interaction strength and rate drops significantly enough that neutrinos stop interacting with everything else in the Universe.
    The photon temperature drops enough so that the first stable, atomic nuclei can form without immediately being blasted apart.
    The temperature drops even further — by about another factor of a million — so that neutral atoms can stably form.

    And after that, the overdense regions grow into stars, galaxies and clusters of galaxies, giving rise to the Universe we see today, all while the photon energy continues to drop thanks to the ongoing expansion.

    Image credit: NASA / GSFC, via http://cosmictimes.gsfc.nasa.gov/universemashup/archive/pages/expanding_universe.html

    That next-to-last step — the one about the atoms becoming neutral — is where the Cosmic Microwave Background (CMB) originates. Prior to that time, the atoms were all ionized, meaning that they were simply positively charged nuclei and free electrons, bathed in a sea of photons. But photons have an extremely large scattering cross-section with electrons, meaning that they bounced around a tremendous amount.

    It’s only when the Universe cooled enough to become neutral that photons stopped seeing free electrons and started seeing only neutral, stable atoms. Because neutral atoms only absorb photons at very particular frequencies, and most of the photons that exist are not at those frequencies, these atoms are effectively transparent to all the photons that exist in the Universe!

    Images credit: Amanda Yoho, of the ionized plasma [upper] before the CMB is emitted, followed by the transition to a neutral Universe [lower] that’s transparent to photons.

    But because the Universe has been expanding and cooling for so long, you can take our location in space and fix it, and recognize one disconcerting fact: all the light from the Big Bang in the regions surrounding our own has been passing us by, continuously, for 13.8 billion years.

    All the stars, galaxies, large-scale structure, gas clouds and cosmic voids located thousands, millions, billions or even tens of billions of light-years away saw their CMB light pass us by ages and ages ago.

    Image credit: Wikimedia Commons user Unmismoobjetivo; of a logarithmic view of the Universe as centered on the Earth.

    Yet — to the point of Joseph’s original question — we still see the CMB, which corresponds (today) to a surface that’s some 45.3 billion light-years away.

    The fact that we still see the CMB at all tells us something very important: the Big Bang happened everywhere at once in a region of space that’s at least 45.3 billion light-years in radius, as seen from our perspective.

    Image credit: NASA/WMAP SCIENCE TEAM.

    And the fact that the CMB is not only visible in all directions, but is of a uniform temperature in all directions tells us — in the context of an inflationary Universe — that the amount that the (observable) Universe inflated must have taken it from an initial size that was, at maximum, 10^-29 meters (or less than a trillionth of 1% the size of a proton) and grew it by at least a factor of 10,000,000,000,000,000,000,000.

    The part of the Universe that we see, today, as our observable Universe could have been even smaller than that scale of 10^-29 meters, initially, and the amount that inflation grew that initial patch of space could have been arbitrarily larger than the factor of 10^22; there is no upper limit on that.

    Image credit: ESA and the Planck collaboration.

    So when we look at the Cosmic Microwave Background, at its uniformity and its small-scale, low-magnitude fluctuations, and the fact that there are no regions of it that are identifiable with one another (i.e., that the Universe does not exhibit a closed topology), we can conclude from this alone that the Big Bang must have occurred everywhere at once in a large region as viewed from our perspective.

    In the context of inflation — something we know an awful lot about — this gives us a lower bound as to the duration and scope of inflation, and ties it in to our observable Universe. The reason the CMB is still around is because the Big Bang, which itself came about at the end of inflation, happened over an incredibly large region of space, a region that’s at least as large as where we observe the CMB to still be. In all probability, that true region is much larger, and that not only will observers anywhere in the Universe see roughly the same CMB, but that we’ll continue to see it (albeit, redshifted a little farther) arbitrarily far into the future.

    Images credit: Wikimedia Commons users Theresa Knott and chris 論, modified by me (L); NASA / COBE science team (R), DMR (top) and FIRAS (bottom).

    Thanks for a great question, Joseph, and thanks to all of you for sending in a great selection of questions and suggestions for Ask Ethan! The truths of the Universe are written on the face of the Universe itself, and we’re doing everything we can to uncover them!

    See the full article here.

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    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 10:23 am on November 30, 2014 Permalink | Reply
    Tags: , , , Big Bang Science, ,   

    From SPACE.com: “The Expanding Universe: From the Big Bang to Today” An Oldie but Worth Your Time 

    space-dot-com logo


    March 21, 2013
    Charles Q. Choi

    The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10-34 of a second or so old — that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age — it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light. During this period, the universe doubled in size at least 90 times, going from subatomic-sized to golf-ball-sized almost instantaneously.

    After inflation, the growth of the universe continued, but at a slower rate. As space expanded, the universe cooled and matter formed. One second after the Big Bang, the universe was filled with neutrons, protons, electrons, anti-electrons, photons and neutrinos.

    During the first three minutes of the universe, the light elements were born during a process known as Big Bang nucleosynthesis. Temperatures cooled from 10^32 degrees K to 10^9 degrees K, and protons and neutrons collided to make deuterium, an isotope of hydrogen. Most of the deuterium combined to make helium, and trace amounts of lithium were also generated.

    For the first 380,000 years or so, the universe was essentially too hot for light to shine. The heat of creation smashed atoms together with enough force to break them up into a dense plasma, an opaque soup of protons, neutrons and electrons that scattered light like fog.
    The globular cluster NGC 6397 contains around 400,000 stars and is located about 7,200 light years away in the southern constellation Ara. With an estimated age of 13.5 billion years, it is likely among the first objects of the Galaxy to form after the Big Bang.

    The globular cluster NGC 6397 contains around 400,000 stars and is located about 7,200 light years away in the southern constellation Ara. With an estimated age of 13.5 billion years, it is likely among the first objects of the Galaxy to form after the Big Bang.
    Credit: European Southern Observatory

    Roughly 380,000 years after the Big Bang, matter cooled enough for atoms to form during the era of recombination, resulting in a transparent, electrically neutral gas. This set loose the initial flash of light created during the Big Bang, which is detectable today as Cosmic Microwave Background radiation. However, after this point, the universe was plunged into darkness, since no stars or any other bright objects had formed yet.

    Cosmic Microwave Background  Planck
    CMB per ESA/Planck

    ESA Planck

    About 400 million years after the Big Bang, the universe began to emerge from the cosmic dark ages during the epoch of reionization. During this time, which lasted more than a half-billion years, clumps of gas collapsed enough to form the first stars and galaxies, whose energetic ultraviolet light ionized and destroyed most of the neutral hydrogen.

    Although the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity, about 5 or 6 billion years after the Big Bang, a mysterious force now called dark energy began speeding up the expansion of the universe again, a phenomenon that continues today.

    A little after 9 billion years after the Big Bang, our solar system was born.

    The Big Bang

    The Big Bang did not occur as an explosion in the usual way one think about such things, despite one might gather from its name. The universe did not expand into space, as space did not exist before the universe. Instead, it is better to think of the Big Bang as the simultaneous appearance of space everywhere in the universe. The universe has not expanded from any one spot since the Big Bang — rather, space itself has been stretching, and carrying matter with it.

    Since the universe by its definition encompasses all of space and time as we know it, it is beyond the model of the Big Bang to say what the universe is expanding into or what gave rise to the Big Bang. Although there are models that speculate about these questions, none of them have made realistically testable predictions as of yet.


    The universe is currently estimated at roughly 13.7 billion years old, give or take 130 million years. In comparison, the solar system is only about 4.6 billion years old.

    This estimate came from measuring the composition of matter and energy density in the universe. This allowed researchers to compute how fast the universe expanded in the past. With that knowledge, they could turn the clock back and extrapolate when the Big Bang happened. The time between then and now is the age of the universe.


    Scientists think that in the earliest moments of the universe, there was no structure to it to speak of, with matter and energy distributed nearly uniformly throughout. The gravitational pull of small fluctuations in the density of matter back then gave rise to the vast web-like structure of stars and emptiness seen today. Dense regions pulled in more and more matter through gravity, and the more massive they became, the more matter they could pull in through gravity, forming stars, galaxies and larger structures known as clusters, superclusters, filaments and walls, with “great walls” of thousands of galaxies reaching more than a billion light years in length. Less dense regions did not grow, evolving into area of seemingly empty space called voids.

    Map of voids and superclusters within 500 million light years from Milky Way
    Richard Powell


    Until about 30 years ago, astronomers thought that the universe was composed almost entirely of ordinary atoms, or “baryonic matter.” However, recently there has been ever more evidence that suggests most of the ingredients making up the universe come in forms that we can not see.

    It turns out that atoms only make up 4.6 percent of the universe. Of the remainder, 23 percent is made up of dark matter, which is likely composed of one or more species of subatomic particles that interact very weakly with ordinary matter, and 72 percent is made of dark energy, which apparently is driving the accelerating expansion of the universe.

    When it comes to the atoms we are familiar with, hydrogen makes up about 75 percent, while helium makes up about 25 percent, with heavier elements making up only a tiny fraction of the universe’s atoms.


    The shape of the universe and whether or not it is finite or infinite in extent depends on the struggle between the rate of its expansion and the pull of gravity. The strength of the pull in question depends in part on the density of the matter in the universe.

    If the density of the universe exceeds a specific critical value, then the universe is “closed” and “positive curved” like the surface of a sphere. This means light beams that are initially parallel will converge slowly, eventually cross and return back to their starting point, if the universe lasts long enough. If so, the universe is not infinite but has no end, just as the area on the surface of a sphere is not infinite but has no beginning nor end to speak of. The universe will eventually stop expanding and start collapsing in on itself, the so-called “Big Crunch”.

    If the density of the universe is less than this critical density, then the geometry of space is “open” and “negatively curved” like the surface of a saddle. If so, the universe has no bounds, and will expand forever.

    If the density of the universe exactly equals the critical density, then the geometry of the universe is “flat” with zero curvature like a sheet of paper. If so, the universe has no bounds and will expand forever, but the rate of expansion will gradually approach zero after an infinite amount of time. Recent measurements suggest that the universe is flat with only a 2 percent margin of error.

    It is possible that the universe has a more complicated shape overall while seeming to possess a different curvature. For instance, the universe could have the shape of a torus, or doughnut.


    Expanding Universe

    In the 1920s, astronomer Edwin Hubble discovered the universe was not static. Rather, it was expanding, a find that revealed the universe was apparently born in a Big Bang.

    After that, it was long thought the gravity of matter in the universe was certain to slow the expansion of the universe. Then, in 1998, the Hubble Space Telescope’s observations of very distant supernovae revealed that a long time ago, the universe was expanding more slowly than it is today. In other words, the expansion of the universe was not slowing due to gravity, but instead inexplicably was accelerating. The name for the unknown force driving this accelerating expansion is dark energy, and it remains one of the greatest mysteries in science.

    NASA Hubble Telescope
    NASA Hubble schematic
    NASA/ESA Hubble

    See the full article, with video, here.

    Please help promote STEM in your local schools.

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  • richardmitnick 10:17 am on November 23, 2014 Permalink | Reply
    Tags: , , , Big Bang Science, ,   

    From Ethan Siegel:- “Ask Ethan #63: The Birth of Space and Time” 

    Starts with a bang
    Starts with a Bang

    Nov 22, 2014
    Ethan Siegel

    If there’s something before the Big Bang, then what does that mean for the beginning of our Universe?

    “You can try to lie to yourself. You can try to tell yourself that you put in the time. But you know — and so do I.” -J.J. Watt

    It’s been half a century since the greatest new predictions of the Big Bang were confirmed, changing our conception of the Universe forever. Rather than having existed forever, and rather than the part accessible to us being infinite in extent, we now know that all we perceive has only been around for a hair under 14 billion years of cosmic time, with our Sun and Solar System present for merely the last third of it. Which is what makes today’s Ask Ethan question so interesting, courtesy of Sebastián:

    When did the space-time begin? When I was a child, I learned that the Big Bang was the beginning of everything. I guess this picture is not currently true, since before [?] the Big Bang there was the cosmic inflation, and the Big Bang was not even a bang but a state where the Universe was hotter and denser. If there was inflation before the Big Bang, then there was space-time before the Big Bang, right?

    There are three things we need to think about to fully address Sebastián’s question, and the first one is what we mean by space and time.

    Image credit: Firefly / Serenity.

    You may be used to our everyday experiences of space — notions like length, width and depth — and time, which you might simply think of as the answers to the questions of where and when. This actually isn’t such a bad conception of things, but there are two things you need to know about space and time that might be a little bit less than intuitive. In fact, it literally took an [Albert] Einstein to figure it all out, and even he needed some help!

    The first is that space and time weren’t separable notions, as [Isaac] Newton thought they were. If you move through space, it fundamentally changes how time passes for you, and if two people move through space at different rates relative to one another, the way they experience time for themselves and the way they see time passing for the other person will be different from one another.

    Image credit: John D. Norton of Pittsburgh, via http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/Special_relativity_clocks_rods/index.html.

    The way this makes the most sense — and it wasn’t Einstein who figured this out, but rather the mathematician Hermann Minkowski — is to consider a unified concept of spacetime, where instead of three spatial dimensions and one time dimension, we consider a new four dimensional entity known as spacetime. Speaking in 1908, Minkowski put forth the idea:

    The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.

    Although Einstein was initially resistant to this revolution, his eventual acceptance of it led to an even greater revelation.

    Image credit: NASA, ESA, L. Calcada.

    The idea that not only were space and time connected into a unified 4D fabric, spacetime, but that the curvature of this 4D fabric was caused by the presence of matter and energy! Just as motion through spacetime affected how different observers experience the passage of time and the distances of space, the presence of matter and energy (and of curvature in general) affects the experience of space and time, too.

    And in the most extreme examples of concentrations of matter and energy — into a singularity — notions of space and time break down!

    Image credit: © Astronomical Society of the Pacific.

    Our most common conceptions of singularities are at the centers of black holes, where we achieve an arbitrarily large (and possibly infinite) density of matter and energy at a single point. In this case, our conception of spacetime breaks down, as Einstein’s equations give nonsensical results.

    Which brings up the second thing we need to think of: the framework of the Big Bang!

    Image credit: NASA, ESA, the GOODS team and M. Giavalisco (STScI); Hubble Space Telescope.

    NASA Hubble Telescope
    NASA Hubble schematic
    NASA/ESA Hubble

    We think of the Universe as being a relatively cold, empty place today, save for the dense concentrations of matter, stars, planets and life that have formed over the billions of years the Universe has been around. Thanks to gravity, electromagnetism and the [strong and weak]nuclear forces, we’ve built up this towering cosmic structure that ranges from the subatomic scale all the way up to tremendous clusters of galaxies.

    But if we go back in time, we discover that not only were things more gravitationally uniform in the past, but also that our cooling, expanding Universe was hotter (since wavelengths of light were shorter) and denser, all due to the nature of the way spacetime expands.

    Image credit: Take 27 LTD / Science Photo Library (main); Chaisson & McMillan (inset).

    We can go as far back in time as we like, to the earliest stages imaginable, to ever higher energies, hotter temperatures and increasing densities. We can go back to:

    A time before any stars or galaxies formed, to when the Universe was just a sea of warm, neutral atoms.
    A time when it was too hot to form neutral atoms at all, when the Universe was just an ionized plasma of nuclei and electrons.
    A time when it was too hot to even form simple nuclei, as free protons and neutrons (along with electrons and photons) reigned.
    A time when densities and temperatures were so high that particle collisions routinely and spontaneously created matter/antimatter pairs of all the known particles in the Universe.

    And you might think to go even further than that, to an arbitrary high density, high temperature and to an “event” in spacetime that also corresponds to a singularity: a moment where the entire Universe is concentrated into a single point.

    Image credit: wiseGEEK, © 2003 — 2014 Conjecture Corporation, via http://www.wisegeek.com/what-is-cosmology.htm#; original from Shutterstock/ DesignUA.

    If this were the case, this is exactly where space and time began, as there’s no such thing as “where” outside of space, and no such thing as “when” outside of time. But there would have been a myriad of puzzles that were simply unexplained about our Universe if we accepted this as the true beginning, as we now have physics that teaches us that we can’t go arbitrarily far back, but rather that a state of inflation — of an exponentially expanding spacetime with energy inherent to space itself — preceded and led to the hot, dense expanding state that we identify with the Big Bang.

    Image credit: ESA and the Planck collaboration, modified by me.

    Because the moment that energy, all bound up in space itself, gets converted into matter and radiation, the exponential expansion ends, and gives us a Universe that appears just as we conceive our early Universe to have been.

    Image generated by me. Each “X” represents a region where inflation ends and a Universe like ours is born; each box without one continues to inflate. At all times into the future, there are more boxes without “X”s than with one. But it does go arbitrarily far back to the past, with no “beginning” to spacetime.

    But now that leads to the third and final point, keeping our notions of singularities in spacetime and the Big Bang in mind: if the Universe before the Big Bang — back during inflation — consisted of exponentially expanding spacetime, where did that spacetime come from?

    As crazy as it seems, there are three very intuitive options.

    The Universe could have had a beginning, before which nothing existed.
    It could have existed eternally, like an infinite line extending in both directions.
    It could have been cyclic like the circumference of a circle, repeating over and over again infinitely.

    Image credit: me.

    If we went with the old Big Bang (and no inflation) picture, the evidence would favor option 1: the Universe being born at the “moment” of infinite, arbitrarily high energies, and along with it, the birth of spacetime.

    However, inflation changes that tremendously. It tells us that rather than a singularity at “t=0”, or where the Big Bang occurred, it tells us that the Universe existed in an inflationary state, or a state where it was exponentially expanding, for an indeterminately long amount of time.

    Images credit: me. Blue and red lines represent a “traditional” Big Bang scenario, where everything starts at time t=0, including spacetime itself. But in an inflationary scenario (yellow), we never reach a singularity, where space goes to a singular state; instead, it can only get arbitrarily small in the past, while time continues to go backwards forever.

    So it appears to favor option 2: the Universe being eternal to the past.

    But there’s a catch to even that, as it turns out. There is a theorem that tells us that an inflationary Universe is past-timelike incomplete: that an ever-expanding Universe must have began from a singularity.

    Image credit: Cosmic Inflation by Don Dixon.

    But that may not be fair, in the sense that the theorem is based on the known laws of physics, and applying them to a time when the known laws of physics break down. Furthermore, as huge and full-of-stuff as our Universe is, the amount of material (and hence, information) in it is still not infinite! With some ~10^90 particles (including photons and neutrinos), going back all the way to the hot, dense expanding state of the Big Bang and then some 10^-30 seconds before to the last moments of inflation, there are some things that are still observationally inaccessible to us.

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

    Unfortunately, one of those things is where that inflating spacetime came from!

    Whether all this means that an inflating Universe couldn’t have lasted forever or whether that means our current rules of physics are not applicable to figuring out whether it lasted forever, had a beginning or is cyclical are unknown. It’s even possible that time is cyclical, and that the cycles change with each iteration! For all our progress, we still have the same three options that philosophers and theologians have considered for millennia: time is finite, time is infinite, or time is cyclical.

    Image credit: me.

    The only thing we know is that if there was a singularity in the past, it didn’t have anything to do with our Hot Big Bang that every particle of matter-and-energy in our observable Universe is traceable to.

    And unless we figure out a new way to gain information about what happened before the Universe observable to us existed in any meaningful sense, the answer may forever be beyond the reach of what is knowable. Not every Ask Ethan question is going to have a definitive answer, but rather this is the best we know given our current body of knowledge. I’m pleased to announce that the next five Ask Ethan questions that are chosen will also be the winner of a free holiday giveaway (to be announced tomorrow), so don’t just send in your questions and suggestions here, but also let me know how to contact you, in case you’re one of the lucky winners!

    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 7:35 pm on August 7, 2014 Permalink | Reply
    Tags: , Big Bang Science, ,   

    From Perimeter Institute: “The Black Hole at the Birth of the Universe” 

    Perimeter Institute
    Perimeter Institute

    August 7, 2014
    Colin Hunter

    The big bang poses a big question: if it was indeed the cataclysm that blasted our universe into existence 13.7 billion years ago, what sparked it?

    Three Perimeter Institute researchers have a new idea about what might have come before the big bang. It’s a bit perplexing, but it is grounded in sound mathematics, testable, and enticing enough to earn the cover story in Scientific American, called The Black Hole at the Beginning of Time.

    What we perceive as the big bang, they argue, could be the three-dimensional “mirage” of a collapsing star in a universe profoundly different than our own.

    “Cosmology’s greatest challenge is understanding the big bang itself,” write Perimeter Institute Associate Faculty member Niayesh Afshordi, Affiliate Faculty member and University of Waterloo professor Robert Mann, and PhD student Razieh Pourhasan.

    Conventional understanding holds that the big bang began with a singularity – an unfathomably hot and dense phenomenon of spacetime where the standard laws of physics break down. Singularities are bizarre, and our understanding of them is limited.

    “For all physicists know, dragons could have come flying out of the singularity,” Afshordi says in an interview with Nature.

    The problem, as the authors see it, is that the big bang hypothesis has our relatively comprehensible, uniform, and predictable universe arising from the physics-destroying insanity of a singularity. It seems unlikely.

    So perhaps something else happened. Perhaps our universe was never singular in the first place.

    Their suggestion: our known universe could be the three-dimensional “wrapping” around a four-dimensional black hole’s event horizon. In this scenario, our universe burst into being when a star in a four-dimensional universe collapsed into a black hole.

    In our three-dimensional universe, black holes have two-dimensional event horizons – that is, they are surrounded by a two-dimensional boundary that marks the “point of no return.” In the case of a four-dimensional universe, a black hole would have a three-dimensional event horizon.

    In their proposed scenario, our universe was never inside the singularity; rather, it came into being outside an event horizon, protected from the singularity. It originated as – and remains – just one feature in the imploded wreck of a four-dimensional star.

    The researchers emphasize that this idea, though it may sound “absurd,” is grounded firmly in the best modern mathematics describing space and time. Specifically, they’ve used the tools of holography to “turn the big bang into a cosmic mirage.” Along the way, their model appears to address long-standing cosmological puzzles and – crucially – produce testable predictions.

    Of course, our intuition tends to recoil at the idea that everything and everyone we know emerged from the event horizon of a single four-dimensional black hole. We have no concept of what a four-dimensional universe might look like. We don’t know how a four-dimensional “parent” universe itself came to be.

    But our fallible human intuitions, the researchers argue, evolved in a three-dimensional world that may only reveal shadows of reality.

    They draw a parallel to Plato’s allegory of the cave, in which prisoners spend their lives seeing only the flickering shadows cast by a fire on a cavern wall.

    “Their shackles have prevented them from perceiving the true world, a realm with one additional dimension,” they write. “Plato’s prisoners didn’t understand the powers behind the sun, just as we don’t understand the four-dimensional bulk universe. But at least they knew where to look for answers.”

    See the full article here.

    About Perimeter

    Perimeter Institute is a leading centre for scientific research, training and educational outreach in foundational theoretical physics. Founded in 1999 in Waterloo, Ontario, Canada, its mission is to advance our understanding of the universe at the most fundamental level, stimulating the breakthroughs that could transform our future. Perimeter also trains the next generation of physicists through innovative programs, and shares the excitement and wonder of science with students, teachers and the general public.

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  • richardmitnick 5:23 pm on May 21, 2014 Permalink | Reply
    Tags: , , , Big Bang Science, , Penzias and Wilson   

    From NPR: “Big Bang’s Ripples: Two Scientists Recall Their Big Discovery” 


    National Public Radio (NPR)

    On May 20, 1964, two astronomers working at a New Jersey laboratory turned a giant microwave antenna toward what they thought would be a quiet part of the Milky Way. They weren’t searching for anything; they were trying to make adjustments to their instrument before looking at more interesting things in the sky.

    planck's image.
    In 2009, the European Space Agency launched the Planck satellite, which offers the best map yet of the microwave sky. Planck indicates that ordinary matter (the stuff of stars and planets) is only about 5 percent of the universe.

    ESA Planck

    What they discovered changed science forever: and found the faint afterglow of the Big Bang.

    “[Arno]Penzias and [Robert] Wilson rocked my world,” says , Charles Bennett an astronomer at Johns Hopkins University in Baltimore. Bennett is one of hundreds of scientists who are still studying the Big Bang’s afterglow to learn more about the universe’s origins, and its eventual fate.

    Robert W. Wilson (left) and Arno Penzias pose next to their antenna after winning the Nobel Prize in 1978 for discovering the Big Bang’s afterglow

    It was an unlikely discovery from an unlikely pair. Penzias was born in 1933 in Bavaria. He is Jewish, and he and his family fled Nazi Germany in 1939. They settled in the Bronx, where his father found work in the leather trade. He went to the City College of New York, hoping to become an engineer. Then a professor recommended physics: “He said, ‘Physicists think they can do anything an engineer can do,’ ” Penzias recalls. He decided to give it a try.

    Wilson was born and raised in Houston. The son of a chemical engineer working in the oil business, he began his academic career as a middling student in high school. “I barely got into Rice [University] — perhaps because my father was an alum,” Wilson says.

    They both found their way into astronomy and met at a conference in 1962. Penzias was working for Bell Telephone Laboratories at the time, and was eager for Wilson to join him.

    By then, Wilson had a reputation as an intelligent, precise scientist, though he was “rather shy at the time,” he says. He was impressed by the endlessly talkative Penzias. “Seemed like it might be a good collaboration,” Wilson says. “I think, in the end, it was an excellent collaboration.”

    It may seem odd that two astronomers would work at a telephone lab. But Bell Labs had something special: a state-of-the-art antenna for detecting microwaves.

    Yes, as in microwave ovens. But microwaves are actually a form of light. And in the 1960s, Bell Labs was trying to use them to transmit long-distance calls. Known as “Project Echo,” the experiment used this superantenna to bounce a signal off a giant mylar balloon in orbit above the Earth. The call went from a site in Holmdel, N.J., near the laboratory headquarters, out to Goldstone in California.

    After Project Echo, Penzias and Wilson were given control of the antenna. For satellite communications to work properly, AT&T engineers wanted to better understand how signals passed through the atmosphere. “I think they probably told management a couple of astronomers would be very helpful,” Wilson says.

    NASA’s Cosmic Background Explorer satellite was launched in 1989. COBE showed that the field of background microwaves wasn’t entirely even.

    NASA’s Cosmic Background Explorer satellite was launched in 1989. COBE showed that the field of background microwaves wasn’t entirely even.

    They set to work, studying microwaves coming from space. One of the first things they did was turn the telescope toward a quiet part of the sky in order to calibrate it. But when they pointed it toward the edge of the Milky Way, they heard static. “Like the hiss that an old FM receiver might have made with an unused channel,” Wilson says.

    “I did all sorts of things to try to find what this other source of noise could be,” Penzias says.

    There was a nearby military base. Maybe its powerful radar was causing interference. So Penzias gave them a call:
    The Holmdel Horn Antenna at Bell Telephone Laboratories in New Jersey was built in 1959 to make the first phone call via satellite.

    The Holmdel Horn Antenna at Bell Telephone Laboratories in New Jersey was built in 1959 to make the first phone call via satellite.

    “And I would say, ‘Good afternoon, sergeant; is the radar on?’

    “And he said, ‘No! Who is this?’

    “And I hung up.”

    Another possibility? Birds.

    “There was a pair of pigeons living in the antenna,” Wilson says. Wilson and Penzias got on their lab coats, climbed inside their giant microwave contraption, and wiped out the pigeon poop. The birds kept roosting in there. Penzias and a lab technician eventually took matters into their own hands: “The only humane way of doing it was to buy a box of shotgun shells,” Penzias says. “So that’s what finally happened to the pigeons.”

    But when they turned on the de-pigeoned antenna, the static was still there.

    The Holmdel Horn Antenna at Bell Telephone Laboratories in New Jersey was built in 1959 to make the first phone call via satellite.

    Penzias and Wilson spent months crossing off possible sources of interference. “It wasn’t the radar; it wasn’t the cars on the Garden State Parkway. We went through absolutely everything,” Penzias recalls.

    Then one day, another researcher suggested the source might not be on Earth. It might not even be in the galaxy. Calculations years before had shown that if the Big Bang really happened, its afterglow would still be visible — and it would show up today as microwaves coming from all directions.

    The static they were getting in New Jersey came from all directions. It was everywhere. Had they just found the remains of the Big Bang?

    “We were a little skeptical but were very pleased to have any explanation of what we were seeing,” says Wilson.

    NASA’s second satellite, launched in 2001, provided a more detailed view of ripples in the microwaves. The ripples correspond to matter that eventually turned into galaxies.
    NASA / WMAP Science Team

    Other scientists were considerably more excited, says , Steven Weinberg a Nobel Prize-winning physicist and author of The First Three Minutes. Before the discovery, the study of the universe’s origins was an abstruse corner of physics filled with impossible-to-prove theories.

    But the microwave background changed that. “Suddenly, it became worthwhile for theorists like myself to study the early universe,” Weinberg recalls.

    Researchers like Charles Bennett have devoted their careers to studying the background. They’ve built satellites and set up telescopes in the remote reaches of Antarctica. It turns out that when you look closely at the microwave glow, you discover tiny variations — ripples left over from the violent swirling of the early universe.

    The ripples are filled with details of how it all began.

    “It told us a tremendous amount about the universe, including its age — 13.8 billion years — but also a census of what it’s made of, the shape of the universe and many other aspects of the universe that we just didn’t know before,” Bennett says.

    The microwaves also show researchers hints of what they don’t know — and there’s a lot we don’t know. Only about 5 percent of the universe is made of ordinary matter. Another quarter is what’s known as ; itinteracts with ordinary matter only through gravity. The rest — nearly 70 percent of all the stuff out there — is , a mysterious force pushing the universe apart.

    And this dark energy may spell the end of the universe. If it continues to push, it may eventually push even atoms apart.

    For Wilson, this is the dark side of his discovery 50 years ago: If the universe had a beginning, a Big Bang, it seems inevitable that it will also have an end.

    “I don’t like the idea that whatever we do as humanity will ultimately be lost in some end of the universe,” Wilson says. “Yes, I guess I wish that the universe might live forever.”

    But he considers himself lucky to have made this discovery. He and Penzias won the Nobel Prize. They went on to have full careers and happy lives. And the end of the universe is still a very long way away.

    See the full article here.

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  • richardmitnick 2:17 pm on April 1, 2014 Permalink | Reply
    Tags: , , , Big Bang Science, , , , ,   

    From Symmetry: “The oldest light in the universe” 

    [I know that I have covered this topic before, but Symmetry’s article is the very best that I have seen.]

    April 01, 2014
    Lori Ann White

    The Cosmic Microwave Background, leftover light from the big bang, carries a wealth of information about the universe—for those who can read it.

    Fifty years ago, two radio astronomers [Arno Penzias and Robert Wilson, both Nobel Laureates] from Bell Labs discovered a faint, ever-present hum in their [radio] telescope that they couldn’t identify. After ruling out radio broadcasts, radar signals, a too-warm receiver and even droppings from pigeons nesting inside the scope, they realized they’d found a soft cosmic static that originated from beyond our galaxy. Indeed, it seemed to fill all of space.

    Fast-forward five decades, and the static has a well-known name: the cosmic microwave background, or CMB. Far from a featureless hum, these faint, cold photons, barely energetic enough to boost a thermometer above absolute zero, have been identified as the afterglow of the big bang.

    Cosmic Microwave Background Planck
    Cosmic Microwave Background from ESA/Planck

    ESA Planck

    This light—the oldest ever observed—offers a baby picture of the very early universe. How early? The most recent result, announced on Saint Patrick’s Day 2014 by the researchers of the BICEP2 experiment, used extremely faint signals imprinted on CMB photons to reach back to the first trillionth of a trillionth of a trillionth of a second after the big bang—almost more of a cosmic sonogram than a baby picture. This image offered the first direct evidence for the era of cosmic inflation, when space itself ballooned outward in a turbocharged period of expansion.

    BICEP 2
    BICEP2 at the South Pole Telescope

    BICEP / Keck Array; The BICEP2 detector array under a microscope
    The BICEP2 telescope at the South Pole uses novel technology developed at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. The focal plane shown here is an array of devices that use superconductivity to gather, filter, detect, and amplify polarized light from the cosmic microwave background — relic radiation left over from the Big Bang that created our universe. The microscope is showing a close-up view of one of the 512 pixels on the focal plane, displayed on the screen in the background. Each pixel is made from a printed antenna that collects polarized millimeter-wavelength radiation, with a filter that selects the wavelengths to be detected. A sensitive detector is fabricated on a thin membrane created through a process called micro-machining. The antennas and filters on the focal plane are made from superconducting materials. An antenna is seen on the close-up shot in the background with the green meandering lines. The detector uses a superconducting film as a sensitive thermometer to detect the heat from millimeter-wave radiation that was collected by the antenna and dissipated at the detector. A detector is seen on the close-up shot in the background to the right of the pink square. Finally, a tiny electrical current from the sensor is measured with amplifiers on the focal plane called SQUIDs (Superconducting QUantum Interference Devices), developed at National Institute of Standards and Technology, Boulder, Colo. The amplifiers are the rectangular chips on the round focal plane. The focal planes are manufactured using optical lithography techniques, similar to those used in the industrial production of integrated circuits for computers.

    CMB photons have more to tell us. Combined with theoretical models of cosmic growth and evolution, ongoing studies will expand this view of the very early universe while also looking forward in time. The goal is to create an entire album chronicling the growth of the universe from the very moments of its birth to today.

    Further studies promise clear insight into which of the many different models of inflation shaped our universe, and can also help us understand dark matter, dark energy and the mass of the neutrino—if researchers can read the CMB in enough detail.

    That’s not easy, though, because the afterglow has faded. During its epic 13-billion-year-plus journey, light that originally blazed through the universe has stretched with space itself, its waves growing billions of times longer and cooler and quieter.

    Relic radiation

    The Standard Model of Cosmology says that about 13.8 billion years ago, the universe was born from an unimaginably hot, dense state. Before a single second had ticked away, cosmic inflation [first proposed by Dr. Alan Guth, M.I.T.] increased the volume of the universe by an amount that varies according to the particular model, but always features a 10 followed by about 30 to 80 zeroes.


    When inflation hit the brakes, leftover energy from that expansion created many of the particles we see around us today: gluons, quarks, photons, electrons and their bigger brethren, muons and taus, and neutrinos. Primordial photons scattered off free-floating electrons, bouncing around inside the gas cloud that was the universe. Hundreds of thousands of years later, the cosmic cloud of particles cooled enough that single protons and helium nuclei could capture the electrons they needed to form neutral hydrogen and helium. This rounded up the free electrons, clearing the fog and releasing the photons. The universe began to shine.

    These photons are the cosmic microwave background. Although now weak, they are everywhere; CMB photons bathe the Earth—and every other star, planet, black hole and hunk of rock in the universe—in their cold light.

    Cosmic sonograms

    The latest big discovery coaxed from CMB data peeks back into the earliest moments of the universe.

    Using cutting-edge sensors, the BICEP2 telescope located at the South Pole detected a type of signal that has been predicted at one strength or another by every version of inflation theory out there: a type of polarization to the CMB light called “B-mode polarization.”

    According to the theories, tiny variations in the energy of the pre-inflation universe caused primordial gravitational waves—ripples in the fabric of space-time—that ballooned outward with inflation. Even before they became the CMB, photons interacted with these ripples, causing the photons’ wavelengths to take on a slight twist. It was this twist that the BICEP2 collaboration measured as a swirling polarization pattern.

    “BICEP2 clearly detected B-mode polarization at precisely the angular scales predicted by inflation,” says Chao-Lin Kuo, one of four principal investigators on the experiment. “This is an incredible combination of big theoretical ideas, teamwork, focus and cutting-edge technologies. The development of mass-produced superconducting polarization detectors and quantum current sensors made a real difference to our success in getting to B-modes first.”

    A discovery of this magnitude calls for further confirmation—not of the signals, which were very clear, but of their inflationary origin. If it holds, the B-mode polarization signals will also give scientists more details about the inflationary event that took place. For example, it can tell us about the energy scale of the universe—essentially the amount of energy poured into the instant of inflation. The BICEP2 result puts this at about 1016 billion electronvolts. For comparison, the Large Hadron Collider’s most powerful proton beams smash together at 104 billion electronvolts—a number with 12 fewer zeros than the first.

    Such information can help scientists determine which of the many different models of inflation actually describes the beginning of our universe. To Walt Ogburn, a postdoctoral researcher at Stanford University and a member of the BICEP2 team, the first view of primordial B-mode polarization does more than turn inflationary theory into fact: It breaks through into uncharted territory in high-energy physics. “What drove inflation is not in the Standard Model,” Ogburn says. By definition, proof of inflation offers evidence that there’s something more out there that’s not yet discovered, and that something big we don’t yet fully understand helped drive the evolution of the early universe.

    Baby picture

    The detection of B-mode polarization is the latest in a long string of scientific discoveries base on information coaxed from these scarce, faint photons.

    The first successes in probing the CMB came almost two decades after it was identified. Beginning with Relikt-1, a Soviet satellite-based experiment launched in 1983, and continuing all the way up to the present, a variety of balloons and satellites have mapped the temperature of the CMB. They found it was 2.7 kelvin across the whole of the sky, with only small, scattered variations in temperature of about one part in 100,000.

    In that temperature map cosmologists saw the image of the infant universe.

    “We’ve learned an enormous amount from the temperature [patterns],” says Lyman Page, also a cosmologist at Princeton. Page was one of the original researchers on what, until this year, was probably the best-known CMB instrument, the Wilkinson Microwave Anisotropy Probe [WMAP]. He now focuses on the Atacama Cosmology Telescope, and few people know more about how to make the CMB give up its secrets.

    ACT Telescope
    Princeton ACT

    Page explains that both the overall sameness of the temperature and the pattern of these minor variations told cosmologists that when the universe began, it was compact enough to be in thermal equilibrium: a dense, nearly featureless plasma of immense energies. But within that plasma, quantum fluctuations caused tiny variations in energy density.

    Then, during cosmic inflation, space grew enormously in all directions. This magnified the variations like an inflating balloon expands ink spots sprayed on it into larger and larger blotches.

    This is the same process that generated the gravitational waves imaged by BICEP2. The gravitational waves left telltale swirling polarization patterns in the CMB without doing much else. However, the dense areas—“blotches” on the otherwise smooth map of the sky—became important seeds of all structures in the universe.

    They grew and cooled, morphed from variations in energy density to variations in matter density. The denser regions attracted more matter as the universe continued to expand, eventually building up large-scale structures we see stitched across the universe today.

    When combined with other theories and measurements, Page says, the temperature variations provide strong evidence that our universe began with the big bang. They have also helped cosmologists improve estimates for how much dark matter and dark energy existed in the early universe (and likely still exist today), and backed the notion that the geometry of the universe is flat.

    “The CMB is really a beautiful signal,” says the University of Chicago’s John Carlstrom, who, like Page, is an expert in extracting information from a few faint photons. He leads the South Pole Telescope project, which uses several instruments mounted on a telescope not too far from BICEP2, to learn more about the CMB. The signal, he continues, offers “very precise measurements of conditions at recombination,” which is the name given to the time when the CMB photons escaped from the primordial cloud of cooling plasma.

    South Pole Telescope
    South Pole Telescope

    These temperature maps—in combination with the primordial B-mode signals detected by BICEP2—cover a time period from a tiny fraction of a second after the birth of the universe to about 380,000 years after that. In the coming years, cosmologists want to expand that picture to include everything that’s happened in the more than 13 billion years since recombination. Many predictions exist for what happened during this huge span of time, but scientists need rock-solid empirical data to compare their theoretical models against.

    BICEP2 revealed a faint but distinctive twist in the polarization pattern of the CMB. Here the lines represent polarization; the red and blue shading show the degree of the clockwise and counter-clockwise twist. Courtesy of: BICEP2

    Filling in the photo album

    CMB photons have more important information to offer, and a new generation of experiments is listening to what they have to say. Situated mostly on the high, dry, cold deserts of the South Pole and the Atacama Plateau in Chile, or in high-flying balloons that rise above much of the atmosphere, new instruments use the CMB to refine our knowledge of how the universe has evolved.

    As the CMB photons traveled through the universe, they were pulled this way and that by gravity, bearing witness to everything that happened on their way from the beginning to now. Using these photons as messengers, the new instruments are helping scientists carefully tease out the story of what the photons saw along their journey.

    Interactions with the hot gas that surrounded and infused galaxy clusters, for example, left a mark on some of the photons in the form of a tiny boost in energy, which is detectable as a very slight adjustment to the temperature map.

    The new instruments also measure a different type of B-mode polarization, added to the CMB photons long after inflation. This type of twist occurs when the photons brush up against the gravity of large-scale cosmic structures comprising both regular matter and dark matter, and it was detected for the first time just last year by SPTpol, a polarization-sensitive microwave camera mounted on the South Pole Telescope.


    Taken together, these measurements of tiny temperature differences and polarization can help scientists map matter distributions over time and improve estimates of how much of the universe is made up of dark matter versus the normal matter we see in stars and planets. It can also help tease apart the difference between expansion due to the momentum left from the big bang and expansion due to dark energy. This will yield an accurate four-dimensional map of the universe, revealing the movement of matter through space and time.

    Further measurements are poised to reveal more information about the contributions to our cosmos of a tiny particle with big implications: the neutrino. Its mass is currently not known to any respectable precision, yet this number is of great importance to predictions regarding the neutrinos’ influence on the growing universe.

    Experiments so far have seen three types of neutrinos [electron neutrinos, muon neutrinos and tau neutrinos, yet some theories predict a fourth type, called a sterile neutrino, as well.

    “Neutrinos are the second most plentiful particle in the universe—after photons,” says Bradford Benson, a scientist at Fermilab and a member of the SPTpol team. “The total mass of all the neutrinos in the universe should at least equal the mass of all the stars.”

    When the universe was smaller, that neutrino mass could have had a significant influence on the universe’s developing structure. As the universe expanded, two things happened: Clumps of heavier, slower-moving particles grew even bigger by pulling in more matter, while the light, speedy neutrinos escaped; and space expanded while the number of neutrinos stayed the same such that, as their density decreased, their gravitational influence decreased as well.

    As they traveled among the growing cosmic structures, the CMB photons recorded these changes in the relative density of neutrinos. Scientists are now mining this record to determine how the influence of neutrinos has evolved over time, and can use the information to estimate their mass. Combined with CMB measurements of dark matter and expansion due to dark energy, scientists expect this research to refine their view of the universe past and present, revealing how matter and energy interacted in the early universe to make the universe we see today.

    Old light, new science

    Using the CMB to discover primordial gravitational waves has been a tremendous step forward. “What’s truly amazing is that the CMB may still hide more secrets even after we found the holy grail,” says Kuo, referring to BICEP2’s discovery.

    Temperature maps, scattered photons and twisted light still have more to tell us. Over the next decade, CMB measurements are poised to help us understand the immense forces of the big bang, illuminate the physics of the early universe and explain the matter and energy we see around us today.

    “Having this signal has helped turn cosmology into a precision science,” Carlstrom says. “We’ve gone from being told, ‘You guys don’t really know what you’re measuring’ to having inde-pendent measurements with levels of precision that rival particle physics.”

    And the benefits are only set to increase. “The study of the CMB is a fantastic field, a very rich field,” Page says. “The microwave background is still going to be a useful tool in 20 years.”

    That’s not bad for a few frigid photons.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

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  • richardmitnick 1:10 pm on September 25, 2013 Permalink | Reply
    Tags: , , Big Bang Science,   

    From isgtw: “Simulating the big bang and beyond” 

    September 25, 2013
    Amber Harmon

    The universe is a vast and mysterious place, but we are beginning to understand it better thanks to some powerful technology. Scientists around the world are using supercomputers to simulate how the big bang led to the formation of galaxies, such as our own Milky Way. A new project sponsored by three of the US Department of Energy’s (DOE’s) National Labs will enable scientists to study this vastness – with a new cosmological simulation analysis toolbox – in greater detail.

    Cosmic Background Radiation
    Cosmic Background Radiation from XMM-Newton

    Modeling the universe with a computer is a highly complex task. To simulate the evolution of galaxies, scientists look to supercomputers for help. Simulations that produce galaxies also produce extreme amounts of data – each dataset could potentially require hundreds of terabytes of storage. Many different scientific analyses and processing sequences are carried out with each data set, making it impractical to rerun simulations for each new study. Efficient storage and sharing of data among scientists is paramount.

    Fermi National Accelerator Laboratory (Fermilab), near Chicago, Illinois, US, is developing a partnership with Argonne and Lawrence Berkeley National Laboratories to develop a state-of-the art, cosmological simulation analysis toolbox. The partnership seeks to take advantage of the DOE’s investments in supercomputers and high-performance computing codes.

    “The three labs are developing an open platform, web-based front end that will enable the scientific community to download, transfer, manipulate, search, and record simulation data,” says Robert Roser, head of Fermilab’s scientific computing division. “Scientists will be able to upload and share applications, as well as carry out complex computational analyses.”

    The team is enhancing existing high-performance computing, high-energy physics, and cosmology-specific software systems to handle the large datasets of galaxy-formation simulations. Team members are also benefiting from expertise they’ve gained by working on the big data challenges posed by particle physics experiments at the Large Hadron Collider at CERN, near Geneva, Switzerland.

    “This is an exciting project for Fermilab, Argonne, and Berkeley Labs. Large-scale simulations of cosmological structure formation are key discovery tools in the department’s Cosmic Frontier program,” Roser says. “Not only will this new project provide important tools for Cosmic Frontier scientists and the many institutions involved in this research, but it will also serve as a prototype for a successful big data software project spanning many groups and communities.”

    See the full article here.

    iSGTW is an international weekly online publication that covers distributed computing and the research it enables.

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

    In its current incarnation, iSGTW is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

    You can read iSGTW via our homepage, RSS, or email. For the complete iSGTW experience, sign up for an account or log in with OpenID and manage your email subscription from your account preferences. If you do not wish to access the website’s features, you can just subscribe to the weekly email.”

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