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  • richardmitnick 9:58 am on September 13, 2017 Permalink | Reply
    Tags: A Grand Presentation, , , , , , Ethan Siegel   

    From Ethan Siegel: “A New Record Nears: The World’s Largest Telescope Prepares For Completion” An Excellent Presentation… 

    Ethan Siegel
    9.13.17

    …With a Bit of a Premature Title

    1
    This artist’s rendering shows a night view of the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. ESO/L. Calçada

    If you want to learn more about the Universe than you ever have before, there’s only so much you can do. You can improve your optics and your seeing, making your mirrors smoother and defect-free than ever before. You can improve your conditions, through adaptive optics or optimizing your observatory’s location. You can work on your camera/CCD/grism technology, to make the most of every single photon your telescope is capable of collecting. But even if you do all that, there’s one improvement that will take you beyond anything you’ve ever accomplished before: size. The larger your primary mirror, the deeper, faster, and higher-resolution you’ll be able to image anything you look at in the Universe.

    Currently, there are a number of 10-meter (33-foot) diameter optical telescopes in the world, with the Giant Magellan Telescope, at 25 meters (82 feet), poised to break that record in just a few years.

    Giant Magellan Telescope, to be at Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile

    But an even more ambitious project, the 39 meter (128 foot) diameter Extremely Large Telescope (ELT) by the European Southern Observatory (ESO), began construction in 2014. By time the mid-2020s come around, it will blow everything else away.

    3
    The construction design for the ELT, revealed in 2016, was the basis for this artist’s rendition of what the completed telescope, with the dome open, will look like in approximately 7 years. ESO/L. Calçada/ACe Consortium

    Not only will it take images that are 16 times sharper and with 256 times the light-gathering power than Hubble, but it will enable us to do science that’s unfathomable with our current instruments. We can directly detect light from extra-solar planets — planets around other stars beyond our own — and break it up spectroscopically, discerning what’s in their atmospheres. For the largest planets of all around the closest stars, we’ll even be able to take the first direct images of those worlds. It will also take unprecedented images of the most distant, earliest galaxies in the Universe; of supermassive black holes at the centers of other galaxies; will enable the detection of water and organic (carbon-based) molecules in protoplanetary disks around newly forming stars; and it will probe the nature and properties of dark matter and dark energy. With a telescope this large and high-quality, so much new science becomes possible.

    4
    The evolving protoplanetary disk, with large gaps, around the young star HL Tauri. ALMA image on the left, VLA image on the right. With the ELT, new views of a protoplanetary disk like this, including in the optical, will become possible at last. Carrasco-Gonzalez, et al.; Bill Saxton, NRAO/AUI/NSF

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    But the key to it all is the size and quality of the primary mirrors. I had the opportunity to speak with Marc Cayrel, the project manager of the optics — the eyes of the telescope — for the ELT. In order to build a telescope this large, you need to build an effective surface that’s properly shaped to focus the incoming light across an area 39 meters in diameter with a large hole in the center: the equivalent of 1000 square meters. (For comparison, Hubble’s area is 4.5 square meters.) The surface needs to be smooth down to an incredible 7.5 nanometers: just 1/100th the size of the wavelengths of light it will collect. You cannot build a single mirror that large to that level of smoothness, so the only option is to do it in segments. With material manufactured by SCHOTT, made out of their unique, low-expansion ZERODUR® material, and then polished by SAFRAN-REOSC, the ELT will boast the largest primary mirror of any optical telescope in humanity’s history.

    5
    This aerial image shows a 1:1 scale model of the European Extremely Large Telescope’s primary mirror, assembled next to the Asiago Astrophysical Observatory near Asiago, Italy. The segmented structure is necessary for a telescope of this size and weight, particularly at the desired optical accuracy. ESO/Sergio Dalle Ave & Roberto Ragazzoni (INAF-OAPD)

    In an incredible technical achievement, the primary mirror will be built out of 798 hexagonal segments, each one 1.4 meters in size, as measured from corner-to-corner. Each segment is a mere 50 millimeters (about two inches) thick, with the mechanics underneath, forms a complete assembly that can be moved in-and-out of the telescope. Each individual segment can be polished to a smoothness of 7.5 nanometers (where that’s the root-mean-square smoothness), achieving the optical goal. The big advantage to that smoothness is image quality, since you need to be that tiny fraction of the light’s wavelength you’re collecting in order to do high contrast imaging, particularly for objects that are so far away. A special reflective coating is then physically added to the top, to make the most of every photon that comes in and strikes the primary mirror.

    6
    A completed, cut, and polished 1.4 meter segment for the ELT primary mirror. © SCHOTT

    Manufacturing, polishing, and constructing these mirrors and the assemblies will take approximately seven years, as the ELT needs around 800 of them. Because they’re hexagonal (six-sided) mirrors that need to make a completed mirror of a particular geometric shape, that means that there are 133 unique shapes you need to complete the mirrors: 798 ÷ 6 = 133. If you didn’t produce them with the required gradient in your mirror shapes, you’d wind up with optical aberration, which was the original flaw with the Hubble Space Telescope! But the coatings themselves are delicate and temporary, and must be done on-site. So that means you need a dedicated production facility, where you can crank out about one mirror coating every day; even at that, it will take over two years to get all the individual mirrors telescope-ready.

    7
    The before-and-after difference between Hubble’s original view (left) with the mirror flaws, and the corrected images (right) after the proper optics were applied. NASA / STScI

    NASA/ESA Hubble Telescope

    Being present here on Earth, the reflective coatings on the mirror are subject to wear-and-tear. Even though the optical quality of a mirror is stable over timescales of decades, the additional layers only last for about 18 months until they need maintenance. That means stripping the mirror coating completely and applying a new coat on a continuous basis. Even if you could replace one or two every day — because the telescope is only used at night — you couldn’t possibly keep all the segments in continuous operation with just the 798 mirrors you have for the telescope. Instead, you need to manufacture an “extra” 133 mirrors, one of each unique shape, so you can replace the mirror you need to repair-and-recoat without jeopardizing the full telescope mirror, for a total of 931 mirrors.

    This means, of course, that you need an extra storage facility for 133 mirrors, an on-site segment stripping and recoating facility, and to basically turn your observatory into a factory whenever you’re not viewing the sky. The plan for the ELT is to have it be in a state of continuous maintenance every day, where a mirror is removed and replaced with a newly recoated one, which means that it can be in a state of continuous operation every night.

    8
    This diagram shows the novel 5-mirror optical system of ESO’s Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope’s giant concave 39-metre segmented primary mirror (M1), it then bounces off two further 4-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. ESO

    Even with 798 perfectly configured, polished, and coated mirrors, your challenges aren’t over. You don’t just need that high accuracy surface for each mirror segment, you need that same accuracy between all of the mirrors combined, and at once. In order to get the tolerance between mirror segments down to that level of precision, you need to account for Earth’s gravity, which will deform the mirrors, and temperature differences and fluctuations. Three position actuators can align each segment assembly for height, tip, and tilt, which will align the mirrors relative to one another continuously: up to four times per second. But the other necessary alignments come from a nine-actuator warping harness that’s on the underside of each mirror segment. These actuators apply torques to compensate for the distortion of each mirror, where the shape and curvature can be optimized, producing required nanometer-level accuracy. Warping adjustments can be done several times per night, as necessary, depending on what’s being observed and what the thermal conditions are.

    9
    It’s not just the assembly structure that needs to be tilted, torqued, and pointed, but the actuators on the reverse side of each mirror. That’s the only way to achieve the required 7.5 nanometer precision not just on each mirror, but between every mirror in the primary array. ESO/H.-H. Heyer

    Next, you need to create the shape of the overall mirror that you want to achieve: what we call a “set point” for the primary mirror. By beginning your night by looking at a star and analyzing the light coming from it after it reflects off the mirror, you can determine how each of the 798 mirrors must be moved, relative to one another, to achieve that perfect focus. Once you’ve done that calibration, the mirrors are all considered phase-locked. During the night, that set point will be used for observations, achieving very good accuracy throughout.

    But to maintain that set point throughout your observations, you need to make tiny, continuous adjustments to the individual mirrors. The air temperature will change; gravity will be present; there will be internal vibrations to the telescope assembly; there will even be wind effects that are substantial. It’s like seeing ripples in a lake or pond due to the wind: if you need a perfectly smooth surface, you have to clean those up. Very small adjustments will be made to each individual mirror about four-to-five times per second, which keeps you phase-locked and at that set point all throughout that night, and at that required 7.5 nanometer accuracy.

    10
    Each mirror begins as a properly-shaped circular disk, with the correct gradient for whichever of the 133 ‘spots’ it will take up in the primary mirror array. Only after polishing down to that 7.5 nanometer tolerance will the mirror be cut to a 1.4 meter hexagonal segment, with the final coating applied subsequent to that. SCHOTT/ESO

    There are also going to be gaps between the individual mirror segments, along with edge effects. There are, after all, 798 mirrors with six edges each; that’s nearly 5,000 edges total! It’s very difficult to polish a mirror evenly all the way to the edge, otherwise you get “turn-down” of the surface near the edges. To overcome that, you polish a disc 1.5 meters in diameter, then carve out your 1.4 meter hexagonal segment, and only then apply your final coating. Still, the hexagonal segments, even with gaps tuned to be only 4 millimeters between each segment, will create an image artifact that can’t be avoided: diffraction spikes. Unlike Hubble, which has four spikes on each star, ELT will have six, due to the hexagonal gaps.

    11
    The star powering the Bubble Nebula, estimated at approximately 40 times the mass of the Sun. Note how the diffraction spikes, due to the telescope itself, interfere with nearby detailed observations of fainter structures. NASA, ESA, Hubble Heritage Team.

    Even at that, there are techniques for helping out on that front. If you image something very distant or wide-field, the spikes are barely perceptible. But if you’re trying to image something faint that’s very close to something bright, that’s when the spikes are a nightmare. By minimizing the gap-space as a function of surface area — 99% of the telescope’s surface is mirror — you help minimize the magnitude of the spikes. And by using shear imaging, where you take two images that are slightly mis-positioned and then subtract them, you can remove most of the effects of those diffraction spikes.

    12
    The Extremely Large Telescope (ELT), with a main mirror 39 metres in diameter, will be the world’s biggest eye on the sky when it becomes operational early in the next decade. This is a detailed preliminary design, showcasing the anatomy of the entire observatory. ESO

    The ELT, by the nature of its size, its power, its weight, and its complexity, could never have been a “build-it-and-you’re-done” type of telescope. It needs to be continuously adjusted throughout the night to maintain the optimal mirror shape; it needs to be re-calibrated night-to-night to achieve that perfect set point; it needs to have its mirrors recoated every 18 months to keep that ideal smoothness and reflectivity. But if you do all of that, and you use the optimal techniques and instruments — from pointing-and-tracking to adaptive optics to imaging methodology — the ELT has the capability to outclass every other optical telescope ever built, on Earth or in space. It’s going to be an incredible technical achievement when complete, an achievement that requires continuous work to maintain. But the science we’ll get from it will be unlike anything else our world has ever seen.

    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,” says Ethan

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  • richardmitnick 11:59 am on September 4, 2017 Permalink | Reply
    Tags: , , , , Ethan Siegel, The ‘Eye of Creation’ holds the secret to cosmic life and death   

    From Ethan Siegel: “The ‘Eye of Creation’ holds the secret to cosmic life and death” 

    Ethan Siegel
    9.4.17

    Every star dies, but not every would-be star really lives.

    “The origin and evolution of life are connected in the most intimate way with the origin and evolution of the stars.” -Carl Sagan

    Supernovae may be the most spectacular cosmic explosions, but planetary nebulae are hundreds of times as numerous.

    1
    The color-coded layers correspond to different temperatures and elements, with the red hydrogen on the outskirts and heavier elements like carbon, oxygen, and silicon found on the interior layers. Image credit: NASA, ESA, and C.R. O’Dell (Vanderbilt University).

    When they run out of nuclear fuel, Sun-like stars blow off their outer layers and contract into a central white dwarf.

    2
    Neutral gas is seen in globules where the blue bubble meets the gaseous disk, which the white dwarf works to evaporate. Image credit: NASA, ESA, and C.R. O’Dell (Vanderbilt University).

    The outer nebula consists of hydrogen, blown off first, while the white dwarf is mostly carbon and oxygen.

    3
    In this contrast-enhanced view, the structure of the evaporating gas globules at the interior edge of the Helix Nebula is put on display. Each globule is only around the mass of the Moon, and evaporates too quickly to form anything of substance. Image credit: NASA, ESA, and C.R. O’Dell (Vanderbilt University); Processing by E. Siegel.

    The white dwarf is small, but hot enough to evaporate the cold, neutral gas clumps surrounding it.

    4
    This close-up of the Helix Nebula showcases the details of the evaporating gas that are in the process of being returned to the interstellar medium, where it will participate in future generations of star formation. Image credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner (STScI), and T.A. Rector (NRAO).

    NASA/ESA Hubble Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    These evaporating gas globules are too small to form new stars, and instead return their material to the interstellar medium.


    The Helix nebula has a disk-like and bubble-like structure to it, formed by the dying central star.

    6
    In this infrared image, the red, central glow is the final layer(s) of gas blown off by the dying star, while the colder, green details were blown off many thousands of years earlier. Image credit: NASA/JPL-Caltech/Univ. of Ariz.

    An infrared view highlights the neutral, cold gas.

    8
    The ESO’s VISTA telescope took this image of the Helix Nebula, highlighting the gaseous, neutral structures that lie on its outskirts. The heated gas that obscures this view in the visible is simply transparent in the infrared, allowing further details to be seen. Image credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit.


    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    All of it will evaporate over time, while the central star is so hot it barely shows up at these cold wavelengths.

    9
    Meanwhile, an ultraviolet view from GALEX highlights not only the bright, hot, central white dwarf, but the reflected ultraviolet light off of the surrounding material, as well as the emission lines from ionized hydrogen. Image credit: NASA/JPL-Caltech/SSC.

    NASA/Galex telescope

    In the ultraviolet, however, the hot, reflected starlight is visible everywhere.

    10
    This combined image from NASA’s Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX). In death, the star’s dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core. Image credit: NASA/JPL-Caltech.

    NASA/Spitzer Infrared Telescope

    The infrared and ultraviolet together showcase the tenuous, gaseous details that are lost in the optical.

    A multiwavelength view is required to reveal the full suite of structure here.

    11
    In a combined image that doesn’t include visible-light data, the gas globules truly stand out. However, they are temporary, and will be fully evaporated only a few thousand years into the future. Image credit: NASA/JPL-Caltech.

    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,” says Ethan

     
  • richardmitnick 8:40 am on September 3, 2017 Permalink | Reply
    Tags: , , , , Ethan Siegel, What science experiments will open the door to the future?   

    From Ethan Siegel: “Ask Ethan: What science experiments will open the door to the future?” 

    Ethan Siegel

    9.2.17

    1
    The ALPHA collaboration has come the closest of any experiment to measuring the behavior of neutral antimatter in a gravitational field. Depending on the results, this could open the door to incredible new technologies. Image credit: Maximilien Brice/CERN.

    Many sci-fi technologies will remain in the realm of fiction unless physics changes. But some experiments could uncover just that!

    “Imagination makes us aware of limitless possibilities. How many of us haven’t pondered the concept of infinity or imagined the possibility of time travel? In one of her poems, Emily Bronte likens imagination to a constant companion, but I prefer to think of it as a built-in entertainment system.”
    -Alexandra Adornetto

    The dream of instantaneous communication, interstellar spaceships, and the ability to travel backwards in time are staples of science fiction. In many ways, they represent humanity’s greatest hopes, and yet they rely on technologies that go beyond what science currently knows is possible. Still, with ongoing experiments at the frontiers of discovery, it’s possible that a new door will open at any time. If we get lucky, what’s just over the horizon? That’s what Igor Zhbanov wants to know:

    Provided that we have some luck, what science experiments that are going to happen withing a couple of decades could open us a way to build some sci-fi movie tech?

    There are a number of fantastic possibilities that could reshape our reality by time the 21st century comes to an end.

    2
    All rockets ever envisioned require some type of fuel, but if a dark matter engine were created, new fuel is always to be found simply by traveling through the galaxy. Image credit: NASA/MSFC.

    Dark matter could be an unlimited fuel source that we don’t need to carry with us. One of the biggest mysteries in science is just what, exactly, the nature of dark matter is. We know it exists thanks to indirect observations, and we know that it’s abundant. If you added up all the dark matter present within a large galaxy like our own, you’d find there’s five times as much of it as there is normal (atom-based) matter. It’s almost certainly made out of a particle with some generic properties:

    it has a mass,
    it doesn’t have an electric or color charge,
    it does have a gravitational interaction,
    and, at some level, it should be able to collide with itself and/or normal matter.

    We know, from Einstein’s famous E = mc², that there’s a tremendous amount of energy stored in this dark matter: five times as much as in all the normal matter combined. If the Universe is kind to us, we just might be able to harness it.

    3
    The mass distribution of cluster Abell 370. reconstructed through gravitational lensing, shows two large, diffuse halos of mass, consistent with dark matter with two merging clusters to create what we see here. Around and through every galaxy, cluster, and massive collection of normal matter exists 5 times as much dark matter, overall. Image credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey (Durham University, UK), the Hubble SM4 ERO Team and ST-ECF.

    There are a multitude of experiments looking for the collisions of dark matter with both normal matter and itself. In general, there are two types of particles: fermions (with half-integer spins) and bosons (with integer spins). If dark matter is a boson, that means it’s most likely its own antiparticle, which means that if you can harness two dark matter particles and make them interact with one another, they’ll annihilate. And if they annihilate, then they produce pure energy. In other words, it’s a free, unlimited source of energy everywhere you go. And because it’s everywhere, you don’t even need to carry it with you as you traverse the Universe. So when you hear about experiments looking for dark matter, the unlimited, free energy we get out is the ultimate dream.

    4
    An illustration of the warp field from Star Trek, which shortens the space in front of it while lengthening the space behind it. Image credit: Trekky0623 of English Wikipedia.

    Antimatter could have negative mass, which means it might be the key to warp drive. If you want to travel to the stars, conventional energy and fuel sources will only get you so far. Or, more literally, they’ll only get you so fast: you’ll forever be limited by the speed of light. The nearest Sun-like star with potentially habitable worlds, Tau Ceti, is approximately 12 light-years away, which means even arriving there and sending back word of what it’s like is a venture that takes at least a generation. But if we could contract the space in front of us as we voyaged across interstellar space, while simultaneously expanding the space behind us, we could get there much faster. That’s the idea behind warp drive, which was put on solid physical footing by astrophysicist Miguel Alcubierre in 1994.

    5
    The Alcubierre solution to General Relativity, enabling motion similar to warp drive. This solution requires negative mass. Image credit: Wikimedia Commons user AllenMcC.

    In order to achieve the proper configuration of spacetime required to achieve warp drive, two things are needed: a tremendous amount of energy, and the existence of negative mass. That negative mass, which is only speculative, is required to deform spacetime in the proper way to make warp drive possible. Yet we’ve never measured the mass of antimatter particles; whether they fall “down” or “up” in a gravitational field is an experiment that has yet to be conclusively performed. CERN’s ALPHA experiment is currently working to measure the gravitational effects of antimatter, and how it behaves in a gravitational field. If the answer is that it falls “up” in a gravitational field, we just might get our negative mass, and warp drive might be possible after all.

    6
    The Virtual IronBird tool for the CAM (Centrifuge Accommodation Module) is one way to create artificial gravity, but requires a lot of energy and only allows a very specific, center-seeking type of force. True artificial gravity would require something to behave with negative mass. Image credit: NASA Ames.

    Negative mass would also allow us to create artificial gravity. That same possibility — that some type of negative mass exists in the Universe — would enable us to create an artificial gravity field in a way that we presently cannot. The existence of positive and negative charges in electromagnetism enable us to create conductors, which allow us to manipulate the electric fields between them and shield ourselves from any electric fields outside of them. Gravitation, as we presently understand it, only possesses one type of charge: positive mass. However, the existence of a negative mass would enable us to create a true zero-gravity environment if we configured it properly, while simultaneously empowering us to create an artificial gravity field of whatever magnitude we wanted between two positive mass/negative mass systems.

    7
    The idea of traveling back in time is presently relegated to the realm of science fiction. However, if there are closed time-like curves allowed in our Universe, it’s not only possible, it’s inevitable. Image credit: Genty / Pixabay.

    A rotating Universe could allow us to travel back in time. Time travel is not only possible, it’s inevitable… in the forward direction. With space and time unified into the fabric of spacetime, it would require some major shakeup to physics-as-we-know-it to enable time travel in the backwards direction. It’s pretty easy to come back to your starting location in space: the Earth does this when it returns to its starting point around the Sun, but it’s traveled forward in time a considerable amount (one year) to do so. A “closed space-like curve” is easy to achieve. To come back to your starting location in time requires something extraordinary, however: a “closed time-like curve” is a feature our expanding, matter-filled Universe doesn’t have. Unless, that is, the Universe rotates.

    8
    t wouldn’t simply be an individual galaxy that rotated to produce closed time-like curves, but the entire Universe on a global scale. Image credit: University of Warwick.

    In a Universe that rotates, there exists an exact solution where if the matter density and the cosmological constant (i.e., dark energy) have specific values, the Universe must have closed time-like curves. So far, we’ve only placed constraints on the overall, global rotation of the Universe, but we haven’t ruled it out. If the Universe turns out to be rotating at a particular rate that balances exactly what the matter density and cosmological constant values require, then it’s completely possible to travel back in time and come back to your exact starting point not only in space, but in spacetime. Large-scale, deep surveys, like types the upcoming WFIRST or LSST observatories will perform, may reveal such a rotation, if it exists.

    NASA/WFIRST

    LSST


    LSST Camera, built at SLAC



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

    There are always more exotic possibilities that are scientifically allowed — teleportation of physical objects, instantaneous travel between discontinuous locations (wormholes), or faster-than-light communication — but those would require significantly more complex finagling that just one experiment giving unexpected-but-plausible results. Nevertheless, we are compelled to look. Science isn’t a story that just has an endpoint, where we learn all there is to know, and then we stop. It’s a continuing detective story, where each discovery, each data point, and each experiment inevitably leads to deeper questions down the road. Wherever that road winds up taking us, it’s important to envision the possibilities, and what it would take to make them come true, at every step along the journey.

    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,” says Ethan

     
  • richardmitnick 12:18 pm on July 16, 2017 Permalink | Reply
    Tags: Ask Ethan: How close are we to a Theory of Everything?, , , , , Electromagnetic and weak and strong and gravitational forces are the four fundamental forces known to exist in this Universe, Ethan Siegel, Formulation of the Standard Model in 1968, , It’s not even a certainty that there even is a theory of everything, , , The Standard Model can be written as a single equation but all the forces within are not unified   

    From Ethan Siegel: “Ask Ethan: How close are we to a Theory of Everything?” 

    Ethan Siegel
    July 15, 2017

    1
    The idea that the forces, particles and interactions that we see today are all manifestations of a single, overarching theory is an attractive one, requiring extra dimensions and lots of new particles and interactions. Image credit: Wikimedia Commons user Rogilbert.

    “Those who begin coercive elimination of dissent soon find themselves exterminating dissenters. Compulsory unification of opinion achieves only the unanimity of the graveyard.” -Robert Jackson

    Since well before Einstein, it was the dream of those who study the Universe to find a single equation to govern as many phenomena as possible. Rather than have a separate law for each and every physical property the Universe has, we could unify these laws into a single, overarching framework. All the laws of electric charge, magnetism, electric currents, induction and more were unified into a single framework by James Clerk Maxwell in the mid-1800s. Ever since, physicists have dreamed of a Theory of Everything: a single equation governing all the laws of the Universe. What progress have we made? That’s the question of Paul Harding, who wants to know:

    “Has science made any progress with regards to the Grand Unified Theory and the Theory of Everything? And could you elaborate on what it would mean if we did find a unified equation?”

    Yes, we’ve made progress, but we’re not there yet. Not only that, but it’s not even a certainty that there even is a theory of everything.

    2
    The electromagnetic, weak, strong and gravitational forces are the four fundamental forces known to exist in this Universe. Image credit: Maharishi University of Management.

    The laws of nature, as we’ve discovered them so far, can be broken down into four fundamental forces: the force of gravity, governed by General Relativity, and the three quantum forces that govern particles and their interactions, the strong nuclear force, the weak nuclear force, and the electromagnetic force. The earliest attempts at a unified theory of everything came shortly after the publication of General Relativity, before we understood that there were fundamental laws to govern nuclear forces. These ideas, known as Kaluza-Klein theories, sought to unify gravitation with electromagnetism.

    3
    The idea of unifying gravitation with electromagnetism goes all the way back to the early 1920s, and the work of Theodr Kaluza and Oskar Klein. Image credit: SLAC National Accelerator Laboratory.

    SLAC Campus

    By adding an extra spatial dimension to Einstein’s General Relativity, a fifth dimension overall (in addition to the standard three space and one time) gave rise to Einstein’s gravity, Maxwell’s electromagnetism, and a new, extra scalar field. The extra dimension would need to be small enough to avoid interfering with the laws of gravity, and the details were such that the extra scalar field needed to have no discernible effects on the Universe. Since there was no way to formulate a quantum theory of gravity with this, the discovery of quantum physics and the nuclear forces — which this attempt at unification couldn’t account for — caused this to fall out of favor.

    4
    The quarks, antiquarks, and gluons of the standard model have a color charge, in addition to all the other properties like mass and electric charge. The Standard Model can be written as a single equation, but all the forces within are not unified. Image credit: E. Siegel.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    However, the strong and weak nuclear forces led to the formulation of the Standard Model in 1968, which brought the strong, weak, and electromagnetic forces under the same overarching umbrella. Particles and their interactions were all accounted for, and a slew of new predictions were made, including a big one about unification. At high energies of around 100 GeV (the energy required to accelerate a single electron to a potential of 100 billion volts), a symmetry unifying the electromagnetic and the weak forces would be restored. New, massive bosons were predicted to exist, and with the discovery of the W and Z bosons in 1983, this prediction was confirmed. The four fundamental forces were reduced down to three.

    5
    The idea of unification holds that all three of the Standard Model forces, and perhaps even gravity at higher energies, are unified together in a single framework. Image credit: © ABCC Australia 2015 http://www.new-physics.com.

    Unification was already an interesting idea, but models took off. People assumed that at higher energies still, the strong force would unify with the electroweak; that was where the idea of Grand Unification Theories (GUTs) came from. Some assumed that at even higher energies, perhaps around the Planck scale, the gravitational force would unify as well; this is one of the main motivations for string theory. What’s very interesting about these ideas, however, is that if you want to have unification, you need to restore symmetries at higher energies. And if the Universe has symmetries at high energies that are broken today, that translates into something observable: new particles and new interactions.

    6
    The Standard Model particles and their supersymmetric counterparts. This spectrum of particles is an inevitable consequence of unifying the four fundamental forces in the context of String Theory. Image credit: Claire David.

    So what new particles and interactions are predicted? This depends on which variant of unification theories you go for, but include:

    Heavy, neutral, dark-matter-like particles,
    supersymmetric partner particles,
    magnetic monopoles,
    heavy, charged, scalar bosons,
    multiple Higgs-like particles,
    and particles that mediate proton decay.

    Although we can be certain, from indirect observations, that there is some origin to our Universe’s dark matter, none of these particles or predicted decays have been observed to exist.

    7
    In 1982, an experiment running under the leadership of Blas Cabrera, one with eight turns of wire, detected a flux change of eight magnetons: indications of a magnetic monopole. Unfortunately, no one was present at the time of detection, and no one has ever reproduced this result or found a second monopole. Image credit: Cabrera B. (1982). First Results from a Superconductive Detector for Moving Magnetic Monopoles, Physical Review Letters, 48 (20) 1378–1381.

    This is a pity, in many regards, because we’ve searched, and hard. In 1982, one of the experiments searching for magnetic monopoles registered a single positive result, spawning many copycats which attempted to discover large numbers of others. Unfortunately, that one positive result was anomalous, and no one has ever replicated it. Also in the 1980s, people began building giant tanks of water and other atomic nuclei, searching for evidence of proton decay. While those tanks eventually wound up being repurposed as neutrino detectors, not a single proton has ever been observed to decay. The proton lifetime is now constrained to be greater than 1035 years: some 25 orders of magnitude greater than the age of the Universe.

    8
    The water-filled tank at Super Kamiokande, which has set the most stringent limits on the lifetime of the proton. In later years, detectors set up in this fashion have made outstanding neutrino observatories, but have yet to detect a single proton decay. Image credit: Kamioka Observatory, ICRR, University of Tokyo.

    This is also too bad, because Grand Unification offers a clean and elegant path to generating the matter/antimatter asymmetry in the Universe. At very early times, the Universe is hot enough to produce matter-and-antimatter pairs of all the particles that can possibly exist. In most GUTs, two of those particles that exist are superheavy X-and-Y bosons, which are charged, and contain both quark and lepton couplings. There’s expected to be an asymmetry in the way the matter versions and the antimatter versions decay, and they can give rise to a leftover presence of matter over antimatter, even if there was none initially. Unfortunately, again, we have yet to find any positive evidence for such particles and/or interactions.

    9
    An equally-symmetric collection of matter and antimatter (of X and Y, and anti-X and anti-Y) bosons could, with the right GUT properties, give rise to the matter/antimatter asymmetry we find in our Universe today. Image credit: E. Siegel / Beyond The Galaxy.

    Ethan Siegel Beyond the Galaxy

    Some physicists contend that the Universe must have these symmetries, and the evidence must simply lie at energies too high for even the LHC to probe.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    But others are coming around to a more uncomfortable possibility: perhaps nature doesn’t unify. Perhaps there is no Grand Unified Theory that describes our physical reality; perhaps a quantum theory of gravity doesn’t unify with the other forces; perhaps the problems of baryogenesis and dark matter have other solutions that aren’t rooted in these ideas. After all, the ultimate arbiter of what the Universe is like isn’t our ideas about it, but rather the results of experiment and observations. We can only ask the Universe what it’s like; it’s up to us to listen to what it tells us and go from there.

    6
    The Standard Model Lagrangian is a single equation encapsulating the particles and interactions of the Standard Model. It has five independent parts: the gluons (1), the weak bosons (2), how matter interacts with the weak force and the Higgs field (3), the ghost particles that subtract the Higgs-field redundancies (4), and the Fadeev-Popov ghosts, which affect the weak interaction redundancies (5). Neutrino masses are not included. Image credit: Thomas Gutierrez, who insists there is one ‘sign error’ in this equation.

    Although we can write the Standard Model as a single equation, it isn’t really a unified entity in the sense that there are multiple, separate, independent terms to govern different components of the Universe. The various parts of the Standard Model don’t interact with each other, as color charge doesn’t affect the electromagnetic or weak forces, and there are unanswered questions about why interactions that should occur, like CP-violation in the strong force, don’t.

    7
    When symmetries are restored (at the top of the potential), unification occurs. However, the breaking of symmetries, at the bottom of the hill, corresponds to the Universe we have today, complete with new species of massive particles. Image credit: Luis Álvarez-Gaumé & John Ellis, Nature Physics 7, 2–3 (2011).

    It’s the hope of many that unification holds the answer to these questions, and will solve many of the open problems and puzzles in physics today. However, any sort of additional symmetries — symmetries which are restored at high energies but are broken today — lead to new particles, new interactions, and new physical rules that the Universe plays by. We’ve tried to reverse-engineer some predictions using what rules we’d need for things to work out, yet the particles and unifications we were hoping to find never materialized. Unification won’t help you derive emergent properties like chemistry, biology, geology, or consciousness, but will help us better understand the origin of where everything came from, and how.

    8
    The cosmic history of the entire known Universe shows that we owe the origin of all the matter within it, and all the light, ultimately, to the end of inflation and the beginning of the Hot Big Bang. Image credit: E. Siegel / ESA and the Planck Collaboration.

    ESA/Planck

    Of course, there is the other possibility: that the Universe simply doesn’t unify. That the multiple different laws and rules we have are there for a reason: these symmetries that we’ve invented are simply our own mathematical inventions, and not descriptive of the physical Universe. For every elegant, beautiful, compelling physical theory that’s out there, there’s an equally elegant, beautiful, and compelling physical theory that is wrong. In these matters, as in all scientific matters, it’s up to humanity to ask the right questions. But it’s up to the Universe to tell us the answers. Whatever they are, that’s the Universe we have. It’s up to us to figure out what those answers mean.

    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,” says Ethan

     
  • richardmitnick 12:30 pm on July 14, 2017 Permalink | Reply
    Tags: , , , , Ethan Siegel, That extra ingredient is a heavy isotope of hydrogen: deuterium, The Universe was born almost exclusively with mere hydrogen and helium, This One Imperfection In Nuclear Physics Allowed Earth To Exist   

    From Ethan Siegel: “This One Imperfection In Nuclear Physics Allowed Earth To Exist” 

    Ethan Siegel
    Jul 13, 2017

    1
    The Bubble Nebula is on the outskirts of a supernova remnant occurring thousands of years ago. Nebulae like this showcase where massive stars are born, and also where heavy elements get added back into the Universe, giving rise to rocky planets and organic materials like what we find here on Earth. T.A. Rector/University of Alaska Anchorage, H. Schweiker/WIYN and NOAO/AURA/NSF.

    NOAO WIYN Telescope, Kitt Peak National Observatory, Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers (55 mi) west-southwest of Tucson, Arizona

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    In order to create a rocky planet that’s teeming with life, the Universe needed to create large amounts of the heavy elements required for life’s processes. To make many of those elements, such as Tin, Iodine, Selenium, Molybdenum, Zinc, and Copper, you need supernovae to have occurred many times in our galaxy’s past. To get many more, such as Iron, Calcium, Cobalt, Sulfur, and Potassium, you need stars massive enough to create them. Yet the Universe was born, almost exclusively, with mere hydrogen and helium. If all you had was hydrogen and helium, it would be impossible to make a star more massive than about three times the Sun’s mass; these heavy elements would never be created and spread throughout the Universe. The only reason we can exist, today, is because one tiny imperfection in the early Universe allows the stars to grow hundreds of times as massive.

    2
    The ultra-massive star Wolf-Rayet 124, shown with its surrounding nebula, is one of thousands of Milky Way stars that could be our galaxy’s next supernova. It’s also much, much larger and more massive than you’d be able to form in a Universe containing only hydrogen and helium. Hubble Legacy Archive / A. Moffat / Judy Schmidy.

    NASA/ESA Hubble Telescope

    In order for the Universe to exist as we know it, we need these massive stars. In a star like our Sun, the central region reaches high enough temperatures to fuse hydrogen into helium, which we’ll do until the core run out of fuel. When that happens, the inner parts of the Sun contract down, heating up to temperatures large enough to fuse helium into carbon, along with trace amounts of other elements. But when we’re out of helium fuel, that’s the end-of-the-line for the Sun; we don’t have it in us to fuse carbon or any heavier elements. It takes a star at least eight times as massive as the Sun to do that. It’s those very same massive stars that end their lives in supernovae, creating and recycling large amounts of heavy elements back into the Universe.

    3
    Supernova remnants provide all the evidence we need to know that supernovae are responsible for providing the vast majority of heavy elements found in the Universe today. NASA/JPL-Caltech.

    In most Milky Way-sized galaxies, we see multiple supernovae every century, indicating that these massive stars are common. In fact, there’s strong evidence that wherever in the Universe you form large bursts of stars, even for the first time, you’ll make many stars massive enough to create these heavy elements. But if all you had were hydrogen and helium, this would create a huge problem: hydrogen fusion begins at temperatures of approximately 4,000,000 K, which requires at least 1.6 × 1029 kg of mass to collapse down into a star. Once hydrogen fusion ignites, however, the outward flux becomes so energetic, very quickly, that no new mass can be added to that star. Once you become a star, you push those gaseous elements that would otherwise gravitate towards you away, preventing your star from growing further.

    4
    A combination of instruments on the ESO’s very large telescope reveals wide-field and narrow-angle views of the Tarantula Nebula. The cluster shown at the center contains some of the most massive stars in the known Universe, including many over 100 solar masses.
    ESO/P. Crowther/C.J. Evans.

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    If all you had were conventional hydrogen and helium, where hydrogen is made of one proton and helium is made of two protons and two neutrons, your proto-star would contract down rapidly, heating up to fusion temperatures in short order and emitting large amounts of high-intensity light. This radiation pushes against the nearby material that helped form the star in the first place, blowing it away from the star and overcoming gravity. You might form stars up to about three times the mass of the Sun, but the more massive ones — the ones we need to create an Earth-like world — would never come to exist.

    5
    Stars form in a wide variety of sizes, colors and masses, including many bright, blue ones that are tens or even hundreds of times as massive as the Sun. This is demonstrated here in the open star cluster NGC 3766, in the constellation of Centaurus. ESO.

    Thankfully, the Universe has, even from birth, an extra ingredient that makes much more massive stars possible. That extra ingredient is a heavy isotope of hydrogen: deuterium, which contains a proton and a neutron together. When you have deuterium and normal hydrogen nuclei together, it takes only a temperature of 1,000,000 K to fuse them together into helium-3, producing radiation that’s much less violent and forceful. This deuterium-burning is the first nuclear reaction to happen in a proto-star, and it pushes the core outwards enough to cause the temperature to rise far more slowly than if there were only hydrogen. Even a small amount of deuterium, less than 0.01% of the initial star’s mass, can delay the temperature increase up to hydrogen fusion by tens of millions of years, buying gravitation the time it needs to grow stars up to tens or even hundreds of times the mass of the Sun.

    6
    From beginning with just protons and neutrons, the Universe builds up helium-4 rapidly, with small but calculable amounts of deuterium and helium-3 left over as well. E. Siegel / Beyond The Galaxy.

    8

    So where did this deuterium come from? During the first few seconds after the Big Bang, the Universe was made of protons and neutrons, which attempt to fuse in a chain reaction to form heavier elements. But that first step involves making deuterium, which is easily destroyed by the high-energy radiation permeating the young Universe. It isn’t until minutes have passed that you can make deuterium without it being blasted apart. While this leads to a Universe that’s about 75% hydrogen and 25% helium, there are tiny, trace amounts of deuterium and helium-3 that get formed, along with even smaller amounts of lithium-7.

    9
    The abundances of helium, deuterium, helium-3 and lithium-7 are highly dependent on only one parameter, the baryon-to-photon ratio, if the Big Bang theory is correct. The fact that we have 0.0025% deuterium is needed to allow stars to form as massive as they do. NASA, WMAP Science Team and Gary Steigman.

    NASA/WMAP

    Even though only about 0.0025% of the Universe, by mass, becomes deuterium (about 1/40,000th) in this process, that’s enough to give even the first stars up to 50 million years to grow in size before hydrogen fusion takes over. Once you make stars that massive, the standard story of hydrogen-helium-carbon fusion takes place, generating large quantities of heavier elements that will get returned to the Universe for future generations of stars.

    10
    The nebula from supernova remnant W49B, still visible in X-rays, radio and infrared wavelengths. It takes a star at least 8-10 times as massive as the Sun to go supernova, and create the necessary heavy elements the Universe requires to have a planet like Earth. X-ray: NASA/CXC/MIT/L.Lopez et al.; Infrared: Palomar; Radio: NSF/NRAO/VLA.

    NASA/Chandra Telescope

    Caltech Palomar Intermediate Palomar Transient Factory telescope at the Samuel Oschin Telescope at Palomar Observatory,located in San Diego County, California, United States

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    Rocky planets become possible; the essential elements for life get spread throughout the Universe. By time many billions of years have passed, planets like Earth can form, and organic materials like sugars, amino acids, and aromatic hydrocarbons will simply bind together naturally. The raw ingredients for everything we know life requires automatically pop into place.

    11
    A multiwavelength view of the galactic center, showing stars, gas, radiation and black holes, among other sources. Heavy elements and complex molecules also abound, and much of this material will be useful in forming future generations of stars. NASA/ESA/SSC/CXC/STScI.

    But without that tiny bit of inefficiency — without that easily-destroyed deuterium left over from the Big Bang to delay the fusion reactions in the cores of stars — it would all be impossible. Our Universe is an imperfect place. But that’s an absolute necessity. Without those imperfections, we’d never be able to exist.

    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,” says Ethan

     
  • richardmitnick 4:15 pm on July 8, 2017 Permalink | Reply
    Tags: , , , , , E=MC2 wins, Ethan Siegel, , , Sir Arthur Eddington, Sir Isaac Newton   

    Brought Foward by Larry Zamick, Rutgers Physics: From Ethan Siegel: “The Last 100 Years: 1919, Einstein and Eddington” 

    Ethan Siegel
    June 11, 2009 [Lary has been at this longer than I.]

    100 years ago, the way we viewed our Universe was vastly different than the way we view it now. The night sky, with stars, planets, comets, asteroids, nebulae, and the Milky Way, was viewed to make up the entire contents of the Universe.

    1
    The Universe was static, governed by two laws only: Newton’s Gravity and Maxwell’s Electromagnetism. There were the first hints that the Universe was made up of quantum particles, such as the photoelectric effect, Rutherford’s first hints at the existence of the nucleus, and Planck’s view that energy was quantized. But other than that — and Einstein’s new Theory of Special Relativity, there were very few mysteries about the Universe in 1909. But one of them would change our view of the Universe forever.

    2
    You see, there was a tiny, tiny problem with the planet Mercury. Its orbit just wasn’t quite right. Kepler’s Laws (which can be derived from Newton’s Gravity) said that all the planets should move in ellipses around the Sun. But Mercury (above) doesn’t quite do that. Mercury makes an ellipse that precesses — or rotates — ever so slightly. Specifically, it precessed at a rate of 1.555 degrees per century. A greatly exaggerated example of precession is shown below:

    3
    Now, physicists and astronomers have always been very detail-oriented people. So they calculated what the effects of the Earth’s equinoxes precessing were, and were able to account for 1.396 of those degrees. They realized that there were seven other major planets (and the asteroids) acting on Mercury, and that was able to account for another 0.148 degrees. That left them with only 0.011 degrees per century that was different between their theoretical predictions and their observations. But this minuscule difference was significant enough that it led some to consider that Newton’s Law of Universal Gravitation might be wrong.

    4
    Newton said that mass and separation distance was what determined gravity. There was a force that he called “action at a distance” that made everything attract. But during the time from 1909-1916, a new theory came about.

    5
    The same guy who discovered the photoelectric effect, special relativity, and E=mc^2 came up with a new theory of gravity. Instead of an “action at a distance” due to mass, this new theory said that space gets bent by energy, and causes everything — even massless things — to bend beneath what we see as gravity.

    6
    Now this new theory was very interesting for a few reasons. First off, it accounted for those 0.011 degrees that Newton’s Gravity did not. Second, it predicted — as a simple solution — the existence of black holes. And third, it predicted that something very exciting and testable would happen: that light would be bent by gravity.

    7
    Big deal, said Newton’s advocates. If I take E=mc^2, and I know that light has energy, I can just substitute E/c^2 for mass in Newton’s equations, and get a prediction that Newton’s gravity would bend light, too. It just so happened that Einstein’s bending was predicted to be twice as much as Newton’s bending, and that there was a total Solar Eclipse coming up in 1919. The stage was set for the most dramatic test of gravity ever.

    8
    The director of Cambridge Observatory, Sir Arthur Eddington, led an expedition to observe the total solar eclipse of May 29, 1919. During an eclipse, the sky gets dark enough that you can see stars, even close to the Sun. So Eddington set out to map the position of the stars when they were close to the Sun, and see how the Sun bent the light. Would it match up with Einstein’s prediction, Newton’s prediction, or would it not bend at all?

    9
    Image credit: American Institute of Physics.

    Lo and behold, Einstein’s prediction was spot on. Just like that, Newton’s theory of Universal Gravitation, the most solid foundation in all of physics — unchallenged for over 200 years — was obsolete. All of this was done in the years 1909-1919, and it was just the start of changing how we view the Universe.

    And (FYI) so far, in the 90 years since, every single prediction of Einstein’s gravity that’s ever been tested — from gravitational lensing to binary pulsar decay to time dilation in a gravitational field — have confirmed General Relativity as the most successful physical theory of all-time.

    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,” says Ethan

    Rutgers, The State University of New Jersey, Larry’s school as a Professor of Physics and mine as a student is a leading national research university and the state’s preeminent, comprehensive public institution of higher education. Rutgers is dedicated to teaching that meets the highest standards of excellence; to conducting research that breaks new ground; and to providing services, solutions, and clinical care that help individuals and the local, national, and global communities where they live.

    Founded in 1766, Rutgers teaches across the full educational spectrum: preschool to precollege; undergraduate to graduate; postdoctoral fellowships to residencies; and continuing education for professional and personal advancement.

    Rutgers smaller
    Please give us back our original beautiful seal which the University stole away from us.
    As a ’67 graduate of University college, second in my class, I am proud to be a member of

    Alpha Sigma Lamda, National Honor Society of non-tradional students.

     
    • Jose 3:08 pm on September 20, 2017 Permalink | Reply

      Gravity is a little big bigger than in Newton’s law; it increases with speed -kinetic energy- where the maximum is the double gravity in the case of light.
      Global Physics also predicts the anomalous precession of Mercury’s orbit as Paul Gerber did 20 years before Einstein. https://molwick.com/en/gravitation/077-mercury-orbit.html

      Like

  • richardmitnick 9:28 am on July 2, 2017 Permalink | Reply
    Tags: Ask Ethan: Could We Save The Earth By Migrating It Away From The Sun?, Ethan Siegel, Physically possible? Absolutely. With current technology? Not a chance.   

    From Ethan Siegel: “Ask Ethan: Could We Save The Earth By Migrating It Away From The Sun?” 

    Ethan Siegel
    Jul 1, 2017

    1
    The NEXIS Ion Thruster, at Jet Propulsion Laboratories, is a prototype for a long-term thruster that could move large-mass objects over very long timescales. NASA / JPL.

    Someday, in the distant future, the Earth’s oceans will boil, destroying all life on the planet’s surface and potentially rendering Earth completely inhospitable. It’s the type of global warming that no human can avert: the gradual warming that the Sun experiences by burning its core fuel over its lifetime. But there may be a way to keep the Earth inhabited if we plan a very long-term solution: migrating the entire Earth. Is this really plausible, though? That’s what Mathieu Nisen wants to know:

    “I want to dream a bit: do you think it could be physically feasible to migrate the earth’s orbit with our current knowledge in science?”

    To find out, we need to figure out how hot it’s going to get, and how fast, in order to move the Earth quickly enough to save it.

    2
    This cutaway showcases the various regions of the surface and interior of the Sun, including the core, which is where nuclear fusion occurs. Wikimedia Commons user Kelvinsong.

    The way any star gets its energy is by fusing lighter elements into heavier ones in its core. Our Sun, in particular, fuses hydrogen into helium in regions where the core temperature exceeds 4,000,000 K. The hotter things get, the faster the rate of fusion; the very center of the core may be as hot as 15,000,000 K. This rate is almost perfectly constant, but not quite. Over very long periods of time, the percentage of hydrogen-to-helium in the core changes, causing the interior to heat up a little bit more over billions of years. When it heats up, three things happen:

    It gets more luminous, meaning it outputs more total energy over time,
    It swells slightly in size, increasing appreciably in radius by a few percent every billion years,
    And its temperature remains almost perfectly constant, changing by less than 1%-per-billion years.

    3
    The Sun has increased in size, brightness, and temperature according to the curves above, and those three quantities will continue to evolve as shown by their respective lines into the future. Wikimedia Commons user RJHall, based on Ribas, Ignasi (2010).

    All of this adds up to one uncomfortable fact: the amount of energy that reaches the Earth is very slowly increasing over time. For every 110 million years that pass, the solar luminosity increases by about 1%, which means that the energy reaching the Earth also rises by 1% over that exact same time. Back when the Earth was four billion years younger, our planet received barely 70% of the energy we do today. And after another one-to-two billion years, if we do nothing else to mitigate it, eventually this increase will cause a severe problem for Earth. At that point, we will hit a mean surface temperature of 373 kelvin (100 °C / 212 °F). In other words, at some point, the Sun will become so hot that the Earth’s oceans will boil.

    4
    If the surface temperature becomes too high, our planet will be unable to support the existence of liquid water on the surface. NASA Goddard Space Flight Center.

    So how can we mitigate it? There are a few potential solutions:

    We can set up a series of large reflectors at the L1 Lagrange point, preventing some of the incident light from reaching the Earth.
    We can geoengineer the atmosphere/albedo of our planet to reflect more light and absorb less.
    We can de-greenhouse our planet, removing molecules like methane and carbon dioxide from the atmosphere.
    We can abandon Earth and focus on terraforming outer worlds, such as Mars.

    5
    A possible pathway for the eventual terraforming of Mars to be more Earth-like. English Wikipedia user Ittiz.

    Any of these would work, in theory, but would also require a tremendous amount of effort and ongoing maintenance.

    However, the solution of migrating the Earth to a more distant orbit would be permanent! And although we’d have to push our orbit out quite considerably to keep temperatures constant, timescales of hundreds of millions of years give us plenty of time, if we need it. To cancel out an effect of a 1% increase in the luminosity of the Sun, we’d need to push Earth an additional 0.5% away from the Sun; to cancel out an increase of 20% (what we expect over the next 2 billion years, total), we need the Earth an extra 9.5% more distant than we are now. Instead of the Earth being a mean distance of 149,600,000 km from the Sun, we’d be looking at more like 164,000,000 km.

    6
    The Earth-Sun distance has not changed by much over the past 4.5 billion years. But if the Sun is going to heat up and we don’t want Earth to heat up commensurately, we should seriously consider migrating our planet outward. ISS Expedition 7 Crew, EOL, NASA.

    This is going to take a lot of energy! To move the Earth — all six septillion (6 × 1024) kilograms of it — that extra distance away from the Sun is going to change our orbital parameters by quite a bit. If we were to push Earth’s mean distance from the Sun out to 164,000,000 km (102 million miles), there would be some significant changes we’d notice:

    It would take an extra 14.6% longer for the Earth to complete a single revolution around the Sun.
    To maintain a stable orbit, our orbital speed would have to slow down, from 30 km/s to 28.5 km/s.
    If the period of Earth’s rotation stayed the same (24 hours), we’d have 418 days in a year, instead of 365.
    The Sun would appear slightly smaller in the sky — by about 10% — and the Sun’s effects on the tides would weaken by a few centimeters.

    7
    If the Sun swelled in size but Earth migrated outward, the two effects would not quite cancel; the Sun would appear slightly smaller from Earth overall. Public domain.

    But in order to get the Earth out that far, we’d need to make a very big energetic change: we’d need to alter the gravitational potential energy of the Sun-Earth system. Even accounting for all the other factors, including the slower-moving Earth around the Sun, we’d have to change the Earth’s orbital energy by 4.7^1035 Joules, which is the equivalent of 1.3^1020 Terawatt-hours: about 1015 times humanity’s total annual energy supply. You might think that given two billion years would help, and it does, but only a little. We would need about 500,000 times the amount of energy that humanity presently generates today, globally, all pumped into migrating the planet outward in order to migrate the Earth to a safe, consistent distance.

    8
    The speed at which planets revolve around the Sun is dependent on their distance from the Sun. Migrating Earth outwards, slowly, by 9.5% ought not perturb the orbits of the other planets. NASA / JPL.

    The conversion technology is the least of our worries; the biggest concern is more fundamental: how do we get all that energy? Realistically, there’s only one place that has enough for those needs, and that is the Sun itself. At present, the Earth receives about 1,500 Watts of power per square meter from the Sun. In order to obtain enough power to migrate the Earth in the right amount of time, we’d need to build an array (in space) that collected that entire 4.7^1035 Joules of energy, evenly, over a time period of two billion years. That means an array that’s 5^1015 square meters in size (and 100% efficient), or the equivalent of the entire surface area of ten Earths.

    9
    The concept of space-based solar power has been around for a long time, but no one has ever conceived of an array that’s 5 billion square kilometers in size. NASA.

    So to migrate the Earth to a higher, safe orbit, that’s what it takes: five billion square kilometers of a 100%-efficient solar array, whose energy goes entirely into pushing the Earth into a more distant orbit around the Sun for two billion years. Physically possible? Absolutely. With current technology? Not a chance. And is it practically possible? Almost definitely not, at least not with what we currently know. The reason that migrating the entire planet is so difficult is twofold: because of how strong the Sun’s gravitational pull is and how massive the Earth is. But this is the planet we have and the Sun we have, and the Sun is going to heat up, regardless of what we do. Until we find a way to gather and utilize that massive amount of energy, we’re going to need other strategies if we want to survive the ultimate global warming apocalypse!

    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,” says Ethan

     
  • richardmitnick 8:37 pm on June 24, 2017 Permalink | Reply
    Tags: Ask Ethan: Can Failed Stars Eventually Succeed?, , , , , Ethan Siegel   

    From Ethan Siegel: “Ask Ethan: Can Failed Stars Eventually Succeed?” 

    Ethan Siegel
    Jun 24, 2017


    The closest brown dwarf system to Earth, Luhman 16, contains enough total mass to form a red dwarf star if everything within it were combined. The question of whether this will ever happen in our Universe is an interesting one. Janella Williams, Penn State University.

    In the night sky, the most apparent thing of all are the stars, found in every direction we dare to look. But for every star that gathers enough mass to ignite nuclear fusion in its core, burning hydrogen into helium and turning matter into energy via E = mc2, there are many other objects that didn’t make it that far. Most collections of mass that start to form in a nebula never get big enough to become a star, and instead become fragmented gas clouds, asteroids, rocky worlds, gas giants, or brown dwarfs. The brown dwarfs are the “failed stars” of the Universe, having gathered enough mass to ignite some rare-isotope fusion reactions, but not enough to become true stars. But many brown dwarfs come in binary pairs, leading Ibnul Hussaini to wonder if they might, someday, merge:

    “Will the orbit of these [brown dwarfs] over a long period of time, eventually become smaller and smaller from the loss of energy through gravitational waves? Will they then eventually end up merging? If so, what happens in a [brown dwarf] merger? Will they merge to become an actual star that goes through fusion? Or is it something else entirely?”

    In astronomy, as in life, just because you didn’t make it on the first try doesn’t mean you’ll never get there. Let’s start by looking at the ones that make it.

    2
    An illustration of a giant planet around a red dwarf star. The difference between a planet, a failed star, and a true star comes down to one thing only: mass. ESO.

    In order to ignite nuclear fusion in the core of a star — to get hydrogen nuclei to fuse — you need to reach a temperature of around 4,000,000 K. The gas that stars form from in interstellar space begins at relatively cold temperatures: just a few tens of degrees above absolute zero. But once gravitation kicks in, it causes this cloud of gas to collapse. When collapse occurs, the atoms inside gain speed, collide with each other, and heat up. If there were only a small number of atoms present, they’d emit that heat out into the interstellar medium, sending light streaming throughout the galaxy. But when you get large numbers of atoms together, they trap that heat, causing the interior of the gas cloud to heat up.

    3
    The constellation of Orion, along with the great molecular cloud complex and including its brightest stars. Many new stars are presently forming here due to the collapse of gas, which traps the heat from stellar formation. Rogelio Bernal Andreo.

    If you form something very small, like of the mass of an asteroid, Earth, or even Jupiter, you might heat up to thousands or even tens of thousands of degrees in your core, but you’ll still be very far away from that fusion temperature. But if you hit a certain critical mass — about thirteen times the mass of Jupiter — you’ll achieve a temperature of about 1,000,000 K. That’s not enough to begin fusing hydrogen into helium, but is a critical temperature for a very specific reaction: deuterium fusion. About 0.002% of the hydrogen in the Universe doesn’t just have a single proton as its nucleus, but rather a proton and a neutron bound together, known as a deuteron. At temperatures of a million degrees, a deuteron and a proton can fuse together into helium-3 (an uncommon isotope of helium), a reaction which releases energy.

    4
    The proton-proton chain responsible for producing the vast majority of the Sun’s power is an example of nuclear fusion. In deuterium fusion, only the deuterium (H-2) + proton (H-1) going to helium-3 (He-3) reaction can occur. Borb / Wikimedia Commons.

    This is important! This release of energy, particularly during the protostar (i.e., star-formation) phase, generates high-energy radiation that pushes back against internal gravitational collapse, preventing the very center from getting too hot and hitting that 4,000,000 K threshold. This buys you extra time — tens of thousands of years or more — allowing you to gather more and more mass. Once you start fusing pure hydrogen (i.e., protons) in your core, the energy release is so intense that stars don’t grow any larger, so those early, first stages are critical. If it weren’t for deuterium fusion, the most massive stars would cap out at only about three times the mass of our Sun, instead of the hundreds of solar masses they reach in our backyard.

    5
    A composite image of the first exoplanet ever directly imaged (red) and its brown dwarf parent star, as seen in the infrared. A true star would be much physically larger and higher in mass than the brown dwarf shown here. European Southern Observatory (ESO).

    In order to ever reach that 4,000,000 K temperature in your core, and thereby become a true star, you need a minimum of about 7.5% the mass of our Sun: around 1.5 × 1029 kg of mass. To become a deuterium-fusing brown dwarf, also known as a failed star, you need somewhere between 2.5 × 1028 kg and 1.5 × 1029 kg of mass. And just as there are binary stars out there in great numbers, so, too, are there binary brown dwarfs.

    6
    These are the two brown dwarfs that make up Luhman 16, and they may eventually merge together to create a star. NASA/JPL/Gemini Observatory/AURA/NSF.

    Gemini/North telescope at Mauna Kea, Hawaii, USA

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    In fact, the closest brown dwarf to us, the system Luhman 16, is a binary system, while other brown dwarfs have been known to have giant planets orbiting them. In the specific case of Luhman 16, the masses of the two brown dwarfs are determined to be:

    Between 8.0 × 1028 kg and 1.0 × 1029 kg, for the primary, and
    between 6.0 × 1028 kg and 1.0 × 1029 kg, for the secondary.

    In other words, there’s an excellent chance that if these two failed stars, orbiting at about three times the Earth-Sun distance from one another, were to merge, they would form an actual star. In fact, any addition of mass that takes a failed star over that mass threshold to begin burning hydrogen in its core ought to do it.

    7
    The two brown dwarfs that make up Luhman 16 have been imaged twelve separate times by the Hubble Space Telescope, indicating their motion and relative orbits over a multi-year time period. Image credit: Hubble / ESA, L. Bedin / INAF.

    Ibnul’s hunch is on the right track: yes, it’s true that orbiting masses do emit gravitational waves, and that the emission of these waves will cause orbits to decay. But for these masses and distances, we’re talking about decay times of somewhere in the neighborhood of 10200 years, which is much, much longer than the lifetime of the Universe. In fact, it’s much longer than the lifetime of any star at all, of the galaxy, or even of the galaxy’s central black hole. If you wait around for gravitational waves to turn this binary pair of brown dwarfs into a star, you’re going to be waiting a disappointingly long time.

    8
    The inspiral and merger scenario for brown dwarfs as well-separated as these two are would take a very long time due to gravitational waves. But collisions are quite likely. Just as red stars colliding produce blue straggler stars, brown dwarf collisions can make red dwarf stars. Melvyn B. Davies, Nature 462, 991-992 (2009).

    Every once in a while, you get random collisions between objects in space. Just the fact that stars, failed stars, rogue planets and more move through the galaxy, primarily influenced by gravitation, means that there’s a finite chance that you’ll just randomly get a collision between two objects. This is a much better strategy than waiting for gravitational waves to take your orbits down, except in the most extreme cases. On timescales of about 1018 years, “only” about 100 million times older than the Universe presently is, brown dwarfs will randomly collide with either other brown dwarfs or stellar corpses, giving new life to a failed star. About 1% of brown dwarfs, according to current estimates, will meet that fate.

    9
    The Sun’s atmosphere is not confined to the photosphere or even the corona, but rather extends out for millions of miles in space, even under non-flare or ejection conditions. NASA’s Solar Terrestrial Relations Observatory.

    NASA/STEREO spacecraft

    But even if you can’t wait for gravitational radiation, and even if you don’t get lucky enough to collide with another brown dwarf in interstellar space, you still have a chance to merge. We normally think of stars as having a certain extent in space: that they take up a certain volume. For that matter, that’s how we think of Earth’s atmosphere, too: as a hard edge, with a boundary between what we consider the atmosphere and outer space. How foolish is that! In reality, atoms and particles extend outward for millions of miles (or kilometers), with flares from stars reaching well beyond the orbit of Earth. It was recently discovered that brown dwarfs emit flares, too, so just as a satellite in low-Earth orbit will fall back down to our planet, the friction from a brown dwarf in orbit around another will eventually draw them in. It won’t quite work for Luhman 16, but if the distance between the two failed stars were more like the Sun-Mercury distance, rather than the Sun-Ceres distance, this effect would have a shot.

    10
    Luigi Bedin’s multi-year study observing the motions of the failed stars in Luhman 16 has shown us how their positions and motions have changed over time, with the cycloid nature resulting from Earth’s motion during the year. Hubble / ESA, L. Bedin / INAF.

    NASA/ESA Hubble Telescope

    So what happens if you do get a merger or a collision? These events are rare and will, for the most part, take much longer than the present age of the Universe to occur. By that point, even a brown dwarf will have burned up all of its deuterium, while the corpse will have cooled off to just a few degrees above absolute zero at the surface. But the energy of a collision or merger ought to create enough heat and pressure in the core that we should — so long as we cross that critical mass threshold — still ignite nuclear fusion in the core. The star will be low-mass, red in color, and extremely long-lived, burning for more than 10 trillion years. When a failed star at last ignites, it will most likely be the only star shining in the galaxy for its entire life; these events will be that rare and spaced out in time. Yet the type of star you become is interesting in its own right.

    11
    When two brown dwarfs, far into the future, finally do merge together, they will likely be the only light shining in the night sky, as all other stars have gone out. The red dwarf that results will be the only primary light source left in the Universe at that time. user Toma/Space Engine; E. Siegel.

    It will burn its fuel so slowly that the helium-4 which gets made — the product of the core’s hydrogen fusion — will eventually convect out of the core, enabling more hydrogen to fuse in the core. The convection is efficient enough that 100% of the star’s hydrogen should burn to completion, leaving a solid mass of helium atoms. There won’t be enough mass to burn that helium any further, so the stellar remnant will contract down to a type of star that doesn’t yet exist in the Universe today: a helium white dwarf. It will take roughly a quadrillion years for this white dwarf to cool down and stop emitting light, during which time other brown dwarfs in the galaxy will collide and ignite. By time a failed star finally succeeds and goes through its entire life cycle, becoming a black dwarf, another failed star will gets its opportunity.

    12
    An accurate size/color comparison of a white dwarf (L), Earth reflecting our Sun’s light (middle), and a black dwarf (R). When white dwarfs finally radiate the last of their energy away, they will all eventually become black dwarfs. BBC / GCSE (L) / SunflowerCosmos (R).

    If you managed to achieve some type of immortality, you could, in theory, travel from failed star to failed star, continuing on by drawing your energy from the Universe’s final, rare successes. Most failed stars will remain failures forever, but the few that succeed will be burning long after all other lights have gone out. As Winston Churchill famous said, “Success is not final, failure is not fatal: it is the courage to continue that counts.” Perhaps that applies to even the stars, even moreso than to ourselves.

    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,” says Ethan

     
  • richardmitnick 2:49 pm on June 22, 2017 Permalink | Reply
    Tags: Ethan Siegel, , What Ethan left out   

    From Ethan Siegel: “The future of astronomy: thousands of radio telescopes that can see beyond the stars” 

    Ethan Siegel
    June 21, 2017

    [SO, DID ETHAN FINALLY DISCOVER SKA? IT LOOKS LIKE THAT IS TRUE. I DID A SEARCH, “ETHAN SIEGEL AND SKA” AND CAME UP WITH NOTHING BUT THIS POST. ETHAN, WHAT ROCK HAVE YOU BEEN LIVING UNDER? COME BACK TO ME AND ENLIGHTEN ME.]

    The future of astronomy: thousands of radio telescopes that can see beyond the stars.

    1
    The Square Kilometer Array will, when completed, be comprised of an array of thousands of radio telescopes, capable of seeing farther back into the Universe than any observatory that has measured any type of star or galaxy. Image credit: SKA Project Development Office and Swinburne Astronomy Productions.

    Never heard of SKA, the square kilometer Array? Once it starts taking data, you’ll never forget it.

    SKA Square Kilometer Array

    SKA South Africa

    “Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.” -Dave Barry

    By building bigger telescopes, going to space, and looking from ultraviolet to visible to infrared wavelengths, we can view stars and galaxies as far back as stars and galaxies go. But for millions of years in the Universe, there were no stars, no galaxies, nor anything that emitted visible light. Prior to that, the only light that existed was the leftover glow from the Big Bang, along with the neutral atoms created during the first few hundred thousand years.

    CMB per ESA/Planck

    ESA/Planck

    For those millions of years, there’s simply never been a way to gather information from the electromagnetic part of the spectrum. But a combination of advances in computing and the new construction of an array of thousands of large-scale radio telescopes across twelve countries opens up an incredible possibility like never before: the ability to map the neutral atoms themselves.

    2
    Distant sources of light — even from the cosmic microwave background [CMB, above] — must pass through clouds of gas. If there’s neutral hydrogen present, it can absorb that light, or, if it’s excited in some way, it can emit light of its own. Image credit: Ed Janssen, ESO [Includes inage of ESO’s VLT at Cerro Paranel, Chile].

    How can you see neutral atoms? After all, unless you’re dealing in either reflected light or with atoms that are themselves in an excited state, neutral atoms are some of the most optically boring materials that there are. Atoms are made of negatively charged electrons surrounding a positively charged nucleus, capable of occupying a variety of quantum states. But early on, for millions of years after the Big Bang, 92% of the atoms are the most boring type that exists: hydrogen, with a single proton and electron. While many different energy states exist, without any external source to excite it, hydrogen atoms are doomed to live in the lowest-energy (ground) state.

    3
    The energy levels and electron wavefunctions that correspond to different states within a hydrogen atom. The energy levels are quantized in multiples of Planck’s constant, but even the lowest energy, ground state has two possible configurations depended on the relative electron/proton spin. Image credit: PoorLeno of Wikimedia Commons.

    But when you first make neutral hydrogen, not all the atoms are perfectly in the ground state. You see, in addition to energy levels, the particles in atoms also have a property called spin: their intrinsic angular momentum. A particle like a proton or an electron can either be spin up (+½) or spin down (-½), and so a hydrogen atom can either have the spins aligned (both up or both down) or anti-aligned (one up and the other down). The anti-aligned combination is slightly lower in energy, but not by much. The transition from an aligned state to an anti-aligned one takes millions of years to occur, and when it does, the atom emits a photon of a very particular wavelength: 21 centimeters.

    4
    The 21-centimeter hydrogen line comes about when a hydrogen atom containing a proton/electron combination with aligned spins (top) flips to have anti-aligned spins (bottom), emitting one particular photon of a very characteristic wavelength. Image credit: Tiltec of Wikimedia Commons.

    Every time you undergo a burst of star formation, you ionize hydrogen atoms, meaning that electrons will fall back onto protons eventually, forming a large number of aligned atoms. By looking for this 21-cm signal, we can:

    construct a map of nearby, recent star formation,
    detect absorbing, neutral sources of anti-aligned gas,
    build a 3D map of neutral gas throughout the Universe,
    detect how star clusters and galaxies formed and evolved over time,
    and possibly detect the absorption and emission features of hydrogen gas immediately after, during, and possibly even before the formation of the first stars.

    5
    Before the formation of the first stars, there’s still neutral hydrogen gas to observe, if we look for it in the right way. Image credit: European Southern Observatory.

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


    Somehow, this image seems fitting at this point.

    Next year, in 2018, just as the James Webb Space Telescope prepares for launch,

    NASA/ESA/CSA Webb Telescope annotated

    construction will begin on the Square Kilometer Array (SKA) [This is not correct. much has already been done. If Ethan skips over it, I will not let it pass uncovered.] SKA will wind up, at completion, being an array of some 4,000 radio telescopes, each approximately 12 meters in diameter, and capable of detecting this 21-cm line back farther than any galaxy we’ve ever seen. While the current galactic record-holder comes from when the Universe was just 400 million years old — 3% of its current age — SKA should be able to get the first 1% of the Universe that even James Webb might not see.

    6
    Only because this distant galaxy, GN-z11, is located in a region where the intergalactic medium is mostly reionized, can Hubble reveal it to us at the present time. James Webb will go much farther, but SKA will image the hydrogen that’s invisible to all other optical and infrared observatories. Image credit: NASA, ESA, and A. Feild (STScI).

    To go beyond the first stars, or to arrive at a cosmic destination where no ultraviolet or visible light can pass through the opaque, intergalactic medium, you need to probe what’s actually there. And in this Universe, the overwhelming majority of what’s there, at least that we can detect, is hydrogen. That’s what we know is out there, and that’s what we’re building SKA with the intention of seeing. It will collect more than ten times the data per second than any array today; it will have more than ten times the data collecting power; and it is expected to map the entire Universe from here all the way back to before the first galaxies. We will learn, in the most powerful way ever, how stars, galaxies, and the gas in the Universe grew up and evolved over time.

    7
    A single dish that’s currently part of the MeerKAT array will be incorporated into the Square Kilometer Array, along with around 4,000 other equivalent dishes. Image credit: SKA Africa Technical Newsletter, 1 (2016).

    A better image, and this is just South Africa:

    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA

    According to Simon Ratcliffe, SKA scientist, we know some of what we’re going to find with SKA, but it’s the unknowns that are the most exciting.

    “Every time we’ve set out to measure something, we’ve discovered something entirely surprising.”

    Radio astronomy has brought us pulsars, quasars, microquasars, and mysterious sources like Cygnus X-1, which turned out to be black holes. The entire Universe is out there, waiting for us to discover it. When SKA is completed, it will shed a light on the Universe beyond stars, galaxies, and even gravitational waves. It will show us the invisible Universe as it truly is. As with anything in astronomy, all we need to do is look with the right tools.

    O.K., not O.K., here is some of what Ethan did not include:

    SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western
    Australia

    Murchison Widefield Array,SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO)

    Artist’s impression of the Mid-Frequency Aperture Array telescope when deployed on the African site (C) SKA Organisation

    SKA LOFAR core (“superterp”) near Exloo, Netherlands

    6
    EMBRACE is the Electronic MultiBeam Radio Astronomy ConcEpt which is the Pathfinder instrument for the SKA at frequencies between 500MHz and 1500MHz.

    Seriously, Ethan, come back to me and tell me why you did not include these assets. After that, do a serious piece on Radio Astronomy that includes the Jansky VLA, the EHT, the European VLBI, The Global mm-VLBI Array, the NRAO VLBA. GBO, Parkes, The Goldstone Deep Space Communications Complex, NASA’s DEEP SPACE NETWORK, and whatever else is slipping my mind. I could put in all of the images because I have them. But, you are fantastic with images, so I will leave it to you to do it right.

    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,” says Ethan

     
  • richardmitnick 4:24 pm on June 17, 2017 Permalink | Reply
    Tags: , , , Can The Universe Ever Expand Faster Than The Speed Of Light?, , Ethan Siegel   

    From Ethan Siegel: “Can The Universe Ever Expand Faster Than The Speed Of Light?” 

    Ethan Siegel
    Jun 17, 2017

    1
    This image represents the evolution of the Universe, starting with the Big Bang. NASA / GSFC

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

    It’s the most fundamental law of special relativity, and the realization that led Einstein to some of the greatest physics breakthroughs of all time: the idea that nothing can travel faster than light. That holds true even today, as all massless particles in a vacuum move exactly at the speed of light, while anything else — a massive particle anywhere or a massless one in a medium — are doomed to move slower than the speed of light. But when it comes to the expanding Universe, this seems like it might not still hold. Kevin Forward wants to know, as he asks:

    In the first millionths of a second of the Big Bang did the universe not expand faster than the speed of light?

    As a spoiler: no, it didn’t expand faster than light then, nor at any other time, nor will it ever do so. But there’s a good reason why one might think it once did.

    2
    Our Universe, from the hot Big Bang until the present day, underwent a huge amount of growth and evolution, and continues to do so.
    NASA / CXC / M.Weiss

    Our Universe, as we see it today, has been around for 13.8 billion years since the hot Big Bang. But if you’re asking how far we can see in any direction, the answer isn’t 13.8 billion light years; it’s much farther than that. You might, if you think very hard, imagine that twice that distance is possible: if a light-emitting object were 13.8 billion light years away 13.8 billion years ago, perhaps it emitted light while it was speeding away from us, maybe even at a speed approaching the speed of light. If a bright object existed back then and was constantly moving away from us at 299,792 km/s, its light would be just arriving now, while the object itself would be 27.6 billion light years distant. All of that is solid reasoning, but it makes an assumption that isn’t necessarily good: that space itself is static.

    3
    The Hercules galaxy cluster showcases a great concentration of galaxies many hundreds of millions of light years away. The farther away we look, the less reliable the assumption that we can treat an observed object as being in the same location in space and time that we are.
    ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute

    ESO Omegacam on VST at ESO’s Cerro Paranal observatory

    ESO VST telescope, at ESO’s Cerro Paranal Observatory, with an elevation of 2,635 metres (8,645 ft) above sea level

    The space we inhabit isn’t static; it’s expanding. In fact, we can measure what the expansion rate is today, what it was like in the distant past, and at every epoch in between. As it turns out, an object that was merely 168 meters away at the Big Bang (okay, at 10^33 seconds after the Big Bang) would only have its light reach us today, 13.8 billion years later, after an incredible journey, and an incredible amount of stretching, and would presently be 46.1 billion light years away.

    4
    The observable Universe might be 46 billion light years in all directions from our point of view, but there’s certainly more, unobservable Universe, perhaps even an infinite amount, just like ours beyond that. This is just the limit of what’s observable to us today. Frédéric MICHEL and Andrew Z. Colvin, annotated by E. Siegel

    “A-ha,” you proclaim, “that means space expanded faster than light!”

    Did it though? Because for something to go faster-than-light, it needs to have a speed inherent to it: something you can measure in, for example, kilometers per second. But that’s not how the Universe expands at all.

    5
    At greater distances and earlier times in the Universe, it was expanding more rapidly. But this does not mean it expanded at a faster speed, but rather at a faster rate, which is a speed-per-unit-distance. NASA, ESA, and A. Feild (STScI)

    Instead, the Universe expands as a speed per unit distance: we normally measure it in kilometers per second per megaparsec, where one megaparsec is about 3.26 million light years. If the expansion rate is 70 km/s/Mpc, that means, on average, an object that’s 10 Mpc away should expand away at 700 km/s; one that’s 200 Mpc away should recede at 14,000 km/s; and one that’s 5,000 Mpc away should appear to be moving away at 350,000 km/s.

    6
    The farther a galaxy is, the faster it expands away from us, and the more its light gets redshifted, necessitating that we look at longer and longer wavelengths. Beyond a certain distance, galaxies become unreachable by anything we emit today, even at the speed of light. Larry McNish of RASC Calgary Center

    Does that mean anything is moving faster than light, though? Let’s go all the way back to Einstein’s special theory of relativity, and ask what it means when we say that nothing can move faster than light. It means that, if you have two objects at the same spacetime event — occupying the same space at the same time — then they can’t move relative to one another at a speed faster than the speed of light. Even if one is moving north at 99% the speed of light and the other moves south at 99% the speed of light, they won’t be moving at 198% the speed of light relative to each other, but 99.995% the speed of light. No matter how fast each one moves, they will never exceed the speed of light relative to one another.

    7
    Particles might move very quickly, either in the same direction, opposite directions, or at an angle relative to one another. But when you measure the speed between two particles, it only makes sense, in the context of relativity, if you measure their speeds at the same location in space and time. NASA/Sonoma State University/Aurore Simonnet

    That’s why it’s called relativity in the first place, because it measures relative motion between two objects at the same location in space and time. But that type of relativity — special relativity — only sets the rules in your local, non-expanding space. General relativity adds another layer on top of that: the fact that space itself expands. By measuring the amount of normal matter, dark matter, dark energy, neutrinos, radiation and more present in the Universe today, and how light reaching us from all different distances in the Universe redshifts with that expansion, we can reconstruct exactly how big the Universe was at any point in the past.

    8
    The timeline of our observable Universe’s history, where the observable portion expands to larger and larger sizes as we move forward in time away from the Big Bang. NASA / WMAP science team

    NASA WMAP

    When it was approximately 10,000 years old, the observable Universe was already 10 million light years in size. When it was just one year old, the observable Universe was nearly 100,000 light years in size. When it was one second old, it was already more than 10 light years in size. That sure does sound like expanding faster than light, doesn’t it? But at no point did any particle move faster than light relative to any other particle that it interacted with.

    9
    A graph of the size/scale of the observable Universe vs. the passage of cosmic time. This is displayed on a log-log scale, with a few major size/time milestones identified. E. Siegel

    Instead, all that happened was that the space between particles expanded, and as it did, it increased the distance between them and stretched the wavelength of radiation present within that space. This has continued for the billions of years of cosmic history that took place since, and continues to take place today. While we may never reach any objects farther away than 15.6 billion light years today, even if we went at the speed of light, that’s not because they’re receding faster than light, but because the space between different locations continues to expand.

    The key takeaway is that space doesn’t expand at a particular speed, but rather at a particular rate: a speed-per-unit-distance. As a result, the farther away you look, the more the expansion of space affects the distance between you and that object you’re viewing. As long as it’s expanding, you can calculate a distance that, if you exceed it, everything appears to be receding away from you faster than 299,792 m/s. The farther away an object is, you can be sure that its light will be redder, its distance will be greater, and it will appear to be moving away from you more and more quickly. But faster than the speed of light? You need to be in the same location in order to measure that. Relative to our location, nothing moves faster than light, and that’s true in every location in the Universe at all times. Space expands, but not only does it not expand faster than light, it doesn’t expand at a speed at all!

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

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

     
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