Tagged: Big Bang Science Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 1:00 pm on June 17, 2017 Permalink | Reply
    Tags: , Big Bang Science, ,   

    From phys.org: “No Universe without Big Bang” 


    June 15, 2017

    Credit: J.-L. Lehners (Max Planck Institute for Gravitational Physics)

    According to Einstein’s theory of relativity, the curvature of spacetime was infinite at the big bang. In fact, at this point all mathematical tools fail, and the theory breaks down. However, there remained the notion that perhaps the beginning of the universe could be treated in a simpler manner, and that the infinities of the big bang might be avoided. This has indeed been the hope expressed since the 1980s by the well-known cosmologists James Hartle and Stephen Hawking with their “no-boundary proposal”, and by Alexander Vilenkin with his “tunnelling proposal”. Now scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam and at the Perimeter Institute in Canada have been able to use better mathematical methods to show that these ideas cannot work.

    One of the principal goals of cosmology is to understand the beginning of our universe. Data from the Planck satellite mission shows that 13.8 billion years ago the universe consisted of a hot and dense soup of particles. Since then the universe has been expanding. This is the main tenet of the hot big bang theory, but the theory fails to describe the very first stages themselves, as the conditions were too extreme. Indeed, as we approach the big bang, the energy density and the curvature grow until we reach the point where they become infinite.

    As an alternative, the “no-boundary” and “tunneling” proposals assume that the tiny early universe arose by quantum tunnelling from nothing, and subsequently grew into the large universe that we see. The curvature of spacetime would have been large, but finite in this beginning stage, and the geometry would have been smooth – without boundary (see Fig. 1, left panel). This initial configuration would replace the standard big bang. However, for a long time the true consequences of this hypothesis remained unclear. Now, with the help of better mathematical methods, Jean-Luc Lehners, group leader at the AEI, and his colleagues Job Feldbrugge and Neil Turok at Perimeter Institute, managed to define the 35 year old theories in a precise manner for the first time, and to calculate their implications [Physical Review D]. The result of these investigations is that these alternatives to the big bang are no true alternatives. As a result of Heisenberg’s uncertainty relation, these models do not only imply that smooth universes can tunnel out of nothing, but also irregular universes. In fact, the more irregular and crumpled they are, the more likely (see Fig. 1, right panel). “Hence the “no-boundary proposal” does not imply a large universe like the one we live in, but rather tiny curved universes that would collapse immediately”, says Jean-Luc Lehners, who leads the “theoretical cosmology” group at the AEI.

    Hence one cannot circumvent the big bang so easily. Lehners and his colleagues are now trying to figure out what mechanism could have kept those large quantum fluctuations in check under the most extreme circumstances, allowing our large universe to unfold.

    The big bang, in its complicated glory, retains all its mystery.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

  • richardmitnick 12:44 pm on February 20, 2017 Permalink | Reply
    Tags: , Big Bang Science, ,   

    From ALMA via ESO: “ALMA’s Hole in the Universe” 

    ALMA Array


    20 February 2017
    No writer credit

    Credit: ALMA (ESO/NAOJ/NRAO)/T. Kitayama (Toho University, Japan)/ESA/Hubble & NASA

    The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light — which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) — has now expanded to permeate the entire cosmos, filling it with detectable photons.

    CMB per ESA/Planck
    CMB per ESA/Planck

    The CMB can be used to probe the cosmos via something known as the Sunyaev-Zel’dovich (SZ) effect, which was first observed over 30 years ago. We detect the CMB here on Earth when its constituent microwave photons travel to us through space. On their journey to us, they can pass through galaxy clusters that contain high-energy electrons. These electrons give the photons a tiny boost of energy. Detecting these boosted photons through our telescopes is challenging but important — they can help astronomers to understand some of the fundamental properties of the Universe, such as the location and distribution of dense galaxy clusters.

    This image shows the first measurements of the thermal Sunyaev-Zel’dovich effect from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile (in blue). Astronomers combined data from ALMA’s 7- and 12-metre antennas to produce the sharpest possible image. The target was one of the most massive known galaxy clusters, RX J1347.5–1145, the centre of which shows up here in the dark “hole” in the ALMA observations. The energy distribution of the CMB photons shifts and appears as a temperature decrease at the wavelength observed by ALMA, hence a dark patch is observed in this image at the location of the cluster.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon
    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small

    ESO 50 Large


  • richardmitnick 4:49 pm on February 12, 2017 Permalink | Reply
    Tags: Big Bang Science, , oscillon, U Basel   

    From U Basel: “Ancient Signals From the Early Universe” 


    U Basel

    February 12, 2017
    No writer credit

    The animation shows a computer simulation of an oscillon, a strong localized fluctuation of the inflaton field of the early universe. According to the calculations of Prof. Stefan Antusch and his team, oscillons produced a characteristic peak in the otherwise broad spectrum of gravitational waves. © Department of Physics, University of Basel

    For the first time, theoretical physicists from the University of Basel in Switzerland have calculated the signal of specific gravitational wave sources that emerged fractions of a second after the Big Bang. The source of the signal is a long-lost cosmological phenomenon called “oscillon”. The journal Physical Review Letters has published the results.

    Although Albert Einstein had already predicted the existence of gravitational waves, their existence was not actually proven until fall 2015, when highly sensitive detectors received the waves formed during the merging of two black holes. Gravitational waves are different from all other known waves. As they travel through the universe, they shrink and stretch the space-time continuum; in other words, they distort the geometry of space itself. Although all accelerating masses emit gravitational waves, these can only be measured when the mass is extremely large, as is the case with black holes or supernovas.

    Gravitational waves transport information from the Big Bang

    However, gravitational waves not only provide information on major astrophysical events of this kind but also offer an insight into the formation of the universe itself. In order to learn more about this stage of the universe, Prof. Stefan Antusch and his team from the Department of Physics at the University of Basel are conducting research into what is known as the stochastic background of gravitational waves. This background consists of gravitational waves from a large number of sources that overlap with one another, together yielding a broad spectrum of frequencies. The Basel-based physicists calculate predicted frequency ranges and intensities for the waves, which can then be tested in experiments.

    A highly compressed universe

    Shortly after the Big Bang, the universe we see today was still very small, dense, and hot. “Picture something about the size of a football,” Antusch explains. The whole universe was compressed into this very small space, and it was extremely turbulent. Modern cosmology assumes that at that time the universe was dominated by a particle known as the inflaton and its associated field.

    Oscillons generate a powerful signal

    The inflaton underwent intensive fluctuations, which had special properties. They formed clumps, for example, causing them to oscillate in localized regions of space. These regions are referred to as oscillons and can be imagined as standing waves. “Although the oscillons have long since ceased to exist, the gravitational waves they emitted are omnipresent – and we can use them to look further into the past than ever before,” says Antusch.

    Using numerical simulations, the theoretical physicist and his team were able to calculate the shape of the oscillon’s signal, which was emitted just fractions of a second after the Big Bang. It appears as a pronounced peak in the otherwise rather broad spectrum of gravitational waves. “We would not have thought before our calculations that oscillons could produce such a strong signal at a specific frequency,” Antusch explains. Now, in a second step, experimental physicists must actually prove the signal’s existence using detectors.

    Original article

    Stefan Antusch, Francesco Cefalà, and Stefano Orani
    Gravitational Waves from Oscillons after Inflation
    Physical Review Letters (2017), doi: 10.1103/PhysRevLett.118.011303

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition



    The University of Basel fosters the development of critically thinking and tolerant individuals who are capable of taking initiative and taking on responsibility. It is the aim of the University to enable these individuals to deepen their knowledge and field-specific academic training and further education.

    Through research and teaching, the University imparts the insights past down over the ages in addition to producing new knowledge. It is guided by the principle of meaningfulness and purpose rather than feasibility.

    The University is aware of the duties arising from knowledge, fulfilling these duties through critical reflection and the services it provides. It takes its own position concerning problems facing society.

    The University realizes its aims by taking responsibility with respect to future generations, the society that supports them, the international academic community and the culture that is passed down from generation to generation.

  • richardmitnick 4:51 pm on August 23, 2016 Permalink | Reply
    Tags: , , Big Bang Science, ,   

    From Symmetry: “Five facts about the Big Bang” 

    Symmetry Mag


    Matthew R. Francis

    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    Inflationary Universe. NASA/WMAP
    Inflationary Universe. NASA/WMAP

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

    It’s the cornerstone of cosmology, but what is it all about?

    Astronomers Edwin Hubble and Milton Humason in the early 20th century discovered that galaxies are moving away from the Milky Way. More to the point: Every galaxy is moving away from every other galaxy on average, which means the whole universe is expanding. In the past, then, the whole cosmos must have been much smaller, hotter and denser.

    That description, known as the Big Bang model, has stood up against new discoveries and competing theories for the better part of a century. So what is this “Big Bang” thing all about?

    The Big Bang happened everywhere at once.

    The universe has no center or edge, and every part of the cosmos is expanding. That means if we run the clock backward, we can figure out exactly when everything was packed together—13.8 billion years ago. Because every place we can map in the universe today occupied the same place 13.8 billion years ago, there wasn’t a location for the Big Bang: Instead, it happened everywhere simultaneously.

    The Big Bang may not describe the actual beginning of everything.

    “Big Bang” broadly refers to the theory of cosmic expansion and the hot early universe. However, sometimes even scientists will use the term to describe a moment in time—when everything was packed into a single point. The problem is that we don’t have either observations or theory that describes that moment, which is properly (if clumsily) called the “initial singularity.”

    The initial singularity is the starting point for the universe we observe, but there might have been something that came before.

    The difficulty is that the very hot early cosmos and the rapid expansion called “inflation” that likely happened right after the singularity wiped out most—if not all—of the information about any history that preceded the Big Bang. Physicists keep thinking of new ways to check for signs of an earlier universe, and though we haven’t seen any of them so far, we can’t rule it out yet.

    The Big Bang theory explains where all the hydrogen and helium in the universe came from.

    In the 1940s, Ralph Alpher and George Gamow calculated that the early universe was hot and dense enough to make virtually all the helium, lithium and deuterium (hydrogen with a neutron attached) present in the cosmos today; later research showed where the primordial hydrogen came from. This is known as “Big Bang nucleosynthesis,” and it stands as one of the most successful predictions of the theory. The heavier elements (such as oxygen, iron and uranium) were formed in stars and supernova explosions.

    The best evidence for the Big Bang is in the form of microwaves. Early on, the whole universe was dense enough to be completely opaque. But at a time roughly 380,000 years after the Big Bang, expansion spread everything out enough to make the universe transparent.

    The light released from this transition, known as the cosmic microwave background (CMB), still exists.

    Cosmic Microwave Background per ESA/Planck
    Cosmic Microwave Background per ESA/Planck

    It was first observed in the 1960s by Arno Penzias and Robert Wilson.

    Big Ear, Arno Penzias and Robert Wilson, AT&T, Holmdel, NJ USA
    Big Ear, Arno Penzias and Robert Wilson, AT&T, Holmdel, NJ USA

    That discovery cemented the Big Bang theory as the best description of the universe; since then, observatories such WMAP and Planck have used the CMB to tell us a lot about the total structure and content of the cosmos.

    One of the first people to think scientifically about the origin of the universe was a Catholic priest.

    In addition to his religious training and work, Georges Lemaître was a physicist who studied the general theory of relativity and worked out some of the conditions of the early cosmos in the 1920s and ’30s.


    His preferred metaphors for the origin of the universe were “cosmic egg” and “primeval atom,” but they never caught on, which is too bad, because …

    It seems nobody likes the name “Big Bang.”

    Until the 1960s, the idea of a universe with a beginning was controversial among physicists. The name “Big Bang” was actually coined by astronomer Fred Hoyle, who was the leading proponent of an alternative theory, where universe continues forever without a beginning.

    His shorthand for the theory caught on, and now we’re kind of stuck with it. Calvin and Hobbes’ attempt to get us to adopt “horrendous space kablooie” has failed so far.

    The Big Bang is the cornerstone of cosmology, but it’s not the whole story. Scientists keep refining the theory of the universe, motivated by our observation of all the weird stuff out there. Dark matter (which holds galaxies together) and dark energy (which makes the expansion of the universe accelerate) are the biggest mysteries that aren’t described by the Big Bang theory by itself.

    Our view of the universe, like the cosmos itself, keeps evolving as we discover more and more new things. But rather than fading away, our best explanation for why things are the way they are has remained—the fire at the beginning of the universe.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • 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 .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

  • 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.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

  • 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.

    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 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.

    STEM Icon

    Stem Education Coalition

  • 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.

    ScienceSprings relies on technology from

    MAINGEAR computers



Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc
%d bloggers like this: