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  • richardmitnick 5:06 pm on February 4, 2023 Permalink | Reply
    Tags: "The Origin of the Origin of the Universe", Arno Penzias and Bob Wilson and the Holmdel horn antenna, , , , , , , , , ,   

    From Astrobites : “The Origin of the Origin of the Universe” 

    Astrobites bloc

    From Astrobites

    Katherine Lee

    Title: Measurement of the Cosmic Microwave Background Spectrum by the COBE FIRAS Instrument

    Authors: J. C. Mather, E. S. Cheng, D. A. Cottingham, R. E. Eplee Jr., D. J. Fixsen, T. Hewagama, R. B. Isaacman, K. A. Jensen, S. S. Meyer, P. D. Noerdlinger, S. M. Read, L. P. Rosen, R. A. Shafer, E. L. Wright, C. L. Bennett, N. W. Boggess, M. G. Hauser, T. Kelsall, S. H. Moseley Jr., R. F. Silverberg, G. F. Smoot, R. Weiss, and D. T. Wilkinson

    First Author’s Institution: NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

    Status: published in ApJ [open access]

    Back in the mid-20th century, there were two competing theories about the origin of the Universe. Scientists, including Edwin Hubble and Georges Lemaître, had already established that space was expanding.

    Edwin Hubble



    Some argued that if you run this expansion back in time, it implies a beginning when everything must have been compressed into a hot, dense singularity, exploding outward from that point in a “Big Bang”. Other astronomers, however, were uncomfortable with the idea that the Universe even had an origin at all. These scientists, most notably Fred Hoyle, argued instead for a cosmology in which the Universe had always existed and had always been expanding, with new galaxies springing up periodically to fill in the gaps. This picture of our Universe is referred to as the “Steady State Theory”.

    These two theories predict fundamentally different things about the background temperature of the Universe. If matter in the Universe does not originate from a single point, as in the Steady State picture, then we would expect the background radiation to be chaotic in nature; there would be no reason for different unconnected regions of spacetime to look the same as each other.

    However, if everything in the Universe comes from the same initial conditions, then everything should be roughly the same temperature. This can also be expressed as the idea that the Universe should be in thermodynamic equilibrium on large scales, and that if you measure the intensity of background radiation at all frequencies, you should see a blackbody spectrum—the characteristic spectrum of an object in equilibrium, dependent only on the object’s temperature. Thus, a key prediction of the Big Bang theory is that the temperature should be nearly constant over the entire sky, with the differences (called anisotropies) from this constant average temperature being extremely small—around one part in 100,000!

    COBE comes to the rescue

    Big Bang cosmologists in the 1960s believed that the peak of the Universe’s blackbody spectrum should be in the microwave frequency range, defined as between 300 MHz and 300 GHz. This would be expected from a massive explosion of energy at the Big Bang, the light from which would have been redshifted into the microwave range as it traveled through the expanding universe. So, if the Big Bang theory is true, we should expect to see a constant source of background radiation coming from all directions in the microwave sky: a so-called Cosmic Microwave Background, or CMB.

    The detection of this CMB radiation in 1965 by Arno Penzias and Robert Woodrow Wilson, as well as the cosmological interpretation of that detection by Robert Dicke, Jim Peebles, Peter Roll, and David Wilkinson, laid the groundwork for modern cosmology, and was the beginning of the end for the idea that the Universe had no origin.

    However, Penzias and Wilson’s discovery was not an accurate measurement of the CMB’s temperature or spectrum. No anisotropies had been detected, and there was still debate over whether or not the CMB spectrum was truly a blackbody. The goal of the Cosmic Background Explorer (COBE) satellite, launched by NASA in 1989, was to answer these lingering questions.

    COBE was split into three instruments: the Differential Microwave Radiometer (DMR), the Far-InfraRed Absolute Spectrophotometer (FIRAS), and the Diffuse Infrared Background Experiment (DIRBE). DMR measured the CMB anisotropies, while DIRBE mapped infrared radiation from foreground dust.

    igure 1: A diagram of the FIRAS instrument, taken from Figure 1a of Mather et. al. (1999).

    FIRAS, meanwhile, was designed to measure the CMB spectrum. It scanned the entire sky multiple times in order to minimize errors, and measured the temperature over a wide range of frequencies between 30 and FIRAS, meanwhile, was designed to measure the CMB spectrum. It scanned the entire sky multiple times in order to minimize errors and measured the temperature over a wide range of frequencies between 30 and nearly 3000 GHz. After eliminating known sources of interference such as cosmic rays, as well as subtracting the effects of light from the Milky Way galaxy and of the Doppler shift caused by the movement of the Earth through space, these scans were then averaged together to create direct measurements of the CMB intensity at various frequencies.

    Figure 2: The cosmic microwave background spectrum, as measured by FIRAS. It shows a near-perfect blackbody, with any deviations from total thermodynamic equilibrium being much too small to see. This plot is taken from Figure 4 of Fixsen et al. (1996), which notes that “uncertainties are a small fraction of the line thickness.”line thickness.”

    The authors found that the background radiation in our universe is in fact extremely close to being a perfect bThe authors of today’s paper found that the background radiation in our Universe is in fact extremely close to being a perfect blackbody! The final temperature found by FIRAS was reported by Mather et al. (1999) to be 2.725 K, with an uncertainty of just 0.002 K! This is an incredibly high-precision measurement and represents the final nail in the coffin for cosmologies other than the Big Bang. John C. Mather received the Nobel Prize in 2006 for his work as FIRAS’s project lead.

    Figure 3: A comparison of the abilities of the COBE [above], WMAP, and Planck satellites to resolve tiny fluctuations in the CMB temperature, called anisotropies. Image: NASA/JPL-Caltech/ESA (Wikimedia Commons)

    Today, cosmologists use the CMB and its anisotropies to characterize the early history of the universe, find galaxy clusters in the later universe, and even look for new physics! The COBE measurements represented the dawn of a new era in cosmology, and laid the groundwork for modern CMB measurements. The science we do toToday, cosmologists use the CMB and its anisotropies to characterize the early history of the Universe, find galaxy clusters in the later Universe, and even look for new physics! Later full-sky measurements taken by the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck satellite added never-before-seen levels of precision to our ability to study the structure and content of the Universe, and future missions like LiteBIRD will continue to improve our ability to study the CMB even more closely, building on COBE’s groundbreaking data. These experiments still rely upon the CMB temperature established by FIRAS, which remains the definitive result even 23 years after its publication.


    In physical cosmology, cosmic inflation, cosmological inflation is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10^−36 seconds after the conjectured Big Bang singularity to some time between 10^−33 and 10^−32 seconds after the singularity. Following the inflationary period, the universe continued to expand, but at a slower rate. The acceleration of this expansion due to dark energy began after the universe was already over 7.7 billion years old (5.4 billion years ago).

    Inflation theory was developed in the late 1970s and early 80s, with notable contributions by several theoretical physicists, including Alexei Starobinsky at Landau Institute for Theoretical Physics, Alan Guth at Cornell University, and Andrei Linde at Lebedev Physical Institute. Alexei Starobinsky, Alan Guth, and Andrei Linde won the 2014 Kavli Prize “for pioneering the theory of cosmic inflation.” It was developed further in the early 1980s. It explains the origin of the large-scale structure of the cosmos. Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the Universe. Many physicists also believe that inflation explains why the universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the universe is flat, and why no magnetic monopoles have been observed.

    The detailed particle physics mechanism responsible for inflation is unknown. The basic inflationary paradigm is accepted by most physicists, as a number of inflation model predictions have been confirmed by observation; however, a substantial minority of scientists dissent from this position. The hypothetical field thought to be responsible for inflation is called the inflaton.

    In 2002 three of the original architects of the theory were recognized for their major contributions; physicists Alan Guth of M.I.T., Andrei Linde of Stanford, and Paul Steinhardt of Princeton shared the prestigious Dirac Prize “for development of the concept of inflation in cosmology”. In 2012 Guth and Linde were awarded the Breakthrough Prize in Fundamental Physics for their invention and development of inflationary cosmology.

    Alan Guth, from M.I.T., who first proposed Cosmic Inflation.

    Alan Guth’s notes:
    Alan Guth’s original notes on inflation.

    Nobel Prize in Physics for 2011 Expansion of the Universe

    4 October 2011

    The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2011

    with one half to

    Saul Perlmutter
    The Supernova Cosmology Project
    The DOE’s Lawrence Berkeley National Laboratory and The University of California-Berkeley,

    and the other half jointly to

    Brian P. SchmidtThe High-z Supernova Search Team, The Australian National University, Weston Creek, Australia.


    Adam G. Riess

    The High-z Supernova Search Team,The Johns Hopkins University and The Space Telescope Science Institute, Baltimore, MD.

    Written in the stars

    “Some say the world will end in fire, some say in ice…” *

    What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year’s Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves.

    In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

    The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

    The teams used a particular kind of supernova, called Type 1a supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

    For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

    The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

    *Robert Frost, Fire and Ice, 1920

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”


    Please help promote STEM in your local schools.

    Stem Education Coalition

    What do we do?

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

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.

    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

    • Dean Osgood 10:04 pm on February 5, 2023 Permalink | Reply

      Long time no contact.
      I only check emails at most once a day.
      I prefer texting
      We are well and enjoying our mountain top
      Take care


      • richardmitnick 11:31 am on February 6, 2023 Permalink | Reply

        Great to hear from you. I just spoke on the phone at length with Gail. My Facebook page has been ruined by Facebook, presenting to me only “Suggested for you” and leaving no blank box in which to write. I do see your posts via email and am able to respond to them, but I cannot originate anything. This is a find a wide spread problem with solution or option to remove. zi learned that one can try on a different browser and I did and it worked for a while but then also presented only ” Suggested for you”. Facebook was my connection to you and the Silver Springs relatives since I do not travel. I am hoping this will end. Thanks a lot, Facebook.


  • richardmitnick 12:48 pm on December 7, 2019 Permalink | Reply
    Tags: Arno Penzias and Bob Wilson and the Holmdel horn antenna, , , , , , ,   

    From Ethan Siegel: “Ask Ethan: Was The Critical Evidence For The Big Bang Discovered By Accident?” 

    From Ethan Siegel
    Dec 7, 2019

    In science, breakthroughs don’t always begin with a ‘eureka’ moment. Sometimes, the true story is absolutely unbelievable.

    Penzias and Wilson and the ATT Bell labs Holmdel Horn

    A visual history of the expanding Universe includes the hot, dense state known as the Big Bang and the growth and formation of structure subsequently. The full suite of data, including the observations of the light elements and the cosmic microwave background, leaves only the Big Bang as a valid explanation for all we see. As the Universe expands, it also cools, enabling ions, neutral atoms, and eventually molecules, gas clouds, stars, and finally galaxies to form. (NASA / CXC / M. WEISS)

    When it comes to our Universe’s origin story, many competing ideas once thrived. Scientists considered a myriad of different possibilities, all of which were compatible with the full suite of data and the laws of nature, at least as they were known at the time. Yet as our measurements and observations of the cosmos improved, these possibilities were put to the test, with most of them falling away. By the 1960s, only a few possibilities remained, when something truly spectacular occurred: the “smoking gun” of the Big Bang was discovered. But was it a complete accident? That’s what Patrick Pallagi wants to know, asking:

    The cosmic microwave background [CMB] is a landmark evidence of the Big Bang origin of the universe. How come this discovery is labelled as an accidental one?

    CMB per ESA/Planck

    ESA/Planck 2009 to 2013

    Sometimes, the best discoveries are the ones you don’t expect. Sometimes, you even scoop the scientists searching for what you’ve accidentally found.

    If you look farther and farther away, you also look farther and farther into the past. The farthest we can see back in time is 13.8 billion years: our estimate for the age of the Universe. It’s the extrapolation back to the earliest times that led to the idea of the Big Bang. While everything we observe is consistent with the Big Bang framework, it’s not something that can ever be proven. (NASA / STSCI / A. FELID)

    The idea of the Big Bang sprouted back in the 1920s, when scientists were first working out the consequences of a Universe governed by General Relativity. In a Universe that had roughly the same amount of matter-and/or-energy in all locations and with no preferred direction, a number of theoretical solutions arose. The Universe could not be stationary and unchanging, but needed to either be expanding or contracting, and could be spatially flat, closed, or open.

    Just as, mathematically, the square root of 4 could either be +2 or -2, the field equations of General Relativity alone couldn’t determine what the Universe was made of, what its curvature was, or how the fabric of space itself was evolving with time. An enormous observational breakthrough, spearheaded by Edwin Hubble’s measurements of individual stars in what we now know are distant galaxies, paved the way to the expanding Universe.

    First noted by Vesto Slipher back in 1917, some of the objects we observe show the spectral signatures of absorption or emission of particular atoms, ions, or molecules, but with a systematic shift towards either the red or blue end of the light spectrum. When combined with the distance measurements of Hubble, this data gave rise to the initial idea of the expanding Universe: the farther away a galaxy is, the greater its light is redshifted. (VESTO SLIPHER, (1917): PROC. AMER. PHIL. SOC., 56, 403)

    But over on the theoretical side, Georges Lemaître had already worked out one remarkable solution for the expanding Universe: one that began with what he called a “primeval atom,” which became the germ of an idea that would grow into the Big Bang.

    If the fabric of the Universe is expanding today and driving distant, unbound galaxies apart from one another — the same way a ball of bread dough with raisins throughout it leavens and causes the raisins to apparently spread away from each other — then that should mean the Universe is getting sparser and lower in energy as time goes on. Densities drop and photon wavelengths stretch in an expanding Universe. But what was most remarkable about this scenario is that it meant the reverse is also true: if we look backwards in time, the Universe should have been denser and higher in energy.

    The ‘raisin bread’ model of the expanding Universe, where relative distances increase as the space (dough) expands. The farther away any two raisin are from one another, the greater the observed redshift will be by time the light is received. The redshift-distance relation predicted by the expanding Universe is borne out in observations, and has been consistent with what’s been known all the way back since the 1920s. (NASA / WMAP SCIENCE TEAM)

    By the time the 1940s rolled around, Lemaître’s ideas — although nothing had demonstrated them to be incorrect — had failed to gain traction. However, George Gamow was extremely curious about them, and began a research program dedicated to developing these ideas. In particular, he noted that if the Universe was expanding while it was gravitating and cooling, the past would have looked very different from the present.

    If you went back early enough, you should come to a time where stars and galaxies hadn’t yet formed, since matter needs time for gravitation to clump and cluster it together. At some point even earlier, the photons must have been hot enough to prevent the formation of neutral atoms, ionizing them faster than electrons and nuclei can form stable atoms. And even before that, the photons were likely hot enough to blast apart even atomic nuclei, creating a sea of protons and neutrons.

    As the Universe cools, atomic nuclei form, followed by neutral atoms as it cools further. All of these atoms (practically) are hydrogen or helium, and the process that allows them to stably form neutral atoms takes hundreds of thousands of years to complete. (E. SIEGEL)

    Those four theoretical predictions:

    an expanding Universe,
    where stars and galaxies and structure only formed and grew over time,
    where there was a moment of transition between the Universe being an ionized plasma and full of neutral atoms,
    and where the early hot, dense stage led to an epoch before stars where nuclear fusion occurred,

    became the four cornerstones of the theoretical framework of the Big Bang.

    Of course, the Big Bang wasn’t the only game in town; there were alternatives that made different predictions. The Steady-State Universe, for example, contended that the Universe was filled with a matter creation field that constantly created new particles as it expanded, and that the elements we see were made in stars. However, that idea of a transition between a plasma phase and a neutral-atom phase would prove to be the differentiator between the Big Bang and all the remaining alternatives.

    In the hot, early Universe, prior to the formation of neutral atoms, photons scatter off of electrons (and to a lesser extent, protons) at a very high rate, transferring momentum when they do. After neutral atoms form, owing to the Universe cooling to below a certain, critical threshold, the photons simply travel in a straight line, affected only in wavelength by the expansion of space. (AMANDA YOHO)

    Gamow recognized that if the Universe was filled with both matter and radiation, the expansion of space would stretch that radiation to longer and longer wavelengths — and hence, lower energies and lower temperatures — over time. If we want to extrapolate back to a time where the Universe was hot enough to ionize neutral atoms, we’d have to go back to where the mean temperature was thousands of degrees.

    No problem, obviously, thought Gamow. The key would then be to estimate how much the Universe had expanded from that early time until the present day. While Gamow and his students and research collaborators did their best, they only came up with a range of possible values for what this radiation should look like today. Once the Universe becomes neutral, those photons should just stream in a straight line, stretched by the expanding Universe, until they arrive at our eyes at just a few degrees above absolute zero.

    After the Universe’s atoms become neutral, not only did the photons cease scattering, all they do is redshift subject to the expanding spacetime they exist in, diluting as the Universe expands while losing energy as their wavelength continues to redshift. While we can concoct a definition of energy that will keep it conserved, this is contrived and not robust. Energy is not conserved in an expanding Universe. (E. SIEGEL / BEYOND THE GALAXY)

    With the power of hindsight, it’s astonishing to realize what a missed opportunity there was. In 1949, electrical engineer Joseph Weber was hired as a professor and ordered by the University to go get a Ph.D. in something. He approached Gamow, introducing himself by saying, “I’m a microwave engineer with considerable experience. Can you suggest a PhD problem?”

    Gamow simply told him “no.”

    Which is really a shame, because after billions of years of cosmic evolution and the Universe expanding, the microwave portion of the spectrum is exactly where this leftover radiation from the Big Bang — today’s CMB (cosmic microwave background) and yesteryear’s primeval fireball — should remain today. The right microwave experiment would have revealed it; instead, Weber went on to build primitive gravitational wave detectors.

    Joseph Weber with his early-stage gravitational wave detector, known as a Weber bar. A microwave-specialized electrical engineer, Gamow’s dismissal of Weber was an enormous missed opportunity for discovering the CMB. (SPECIAL COLLECTIONS AND UNIVERSITY ARCHIVES, UNIVERSITY OF MARYLAND LIBRARIES)

    More time passed, and by the 1960s, a team of researchers at Princeton — including Bob Dicke, Jim Peebles, David Wilkinson and Peter Roll — starting planning a mission to detect this leftover radiation. Temperature estimates had gotten much better, and the development of a detector (a Dicke radiometer) that could find this radiation via a balloon-borne mission, coupled with Peebles’ theoretical work, made this an imminent possibility.

    However, some 30 miles away, two scientists (Arno Penzias and Bob Wilson) working on satellite communications for Bell Labs (a subsidiary of AT&T) were using a brand new piece of equipment: the Holmdel horn antenna. It was giant, ultra-sensitive, and designed for receiving signals from Earth. However, there was a problem: no matter where in the sky they pointed their antenna, there was this annoying background of noise they just couldn’t seem to get rid of.

    Arno Penzias and Bob Wilson at the location of the antenna in Holmdel, New Jersey, where the cosmic microwave background was first identified. Although many sources can produce low-energy radiation backgrounds, the properties of the CMB confirm its cosmic origin. (PHYSICS TODAY COLLECTION/AIP/SPL)

    Arno Penzias and Robert Wilson, AT&T, Holmdel, NJ USA, with the Holmdel horn antenna, first caught the faint echo of the Big Bang

    They tried everything. They tried turning it off and on again. They tried pointing it towards the Sun and then away from it. They used it during the day. They used it at night. They aimed it at the plane of the Milky Way. They even discovered pigeons roosting in the horn, resulting in a scene where they cleaned the nests out and mopped up all the bird droppings. Still, that background signal remained constant and omnipresent across the entire sky.

    It was only after calling around and sharing their puzzlement that a visiting scientist — who happened to be the referee of a recent Peebles paper — suggested that this might be the long-sought signal of the CMB. Penzias and Wilson gave the Dicke group a call, and after a brief conversation, realized what they had discovered after all. Dicke’s voice rang out through the halls at Princeton, announcing “boys, we’ve been scooped!” Completely by accident, the smoking gun for the Big Bang had just been discovered.

    The unique prediction of the Big Bang model is that there would be a leftover glow of radiation permeating the entire Universe in all directions. The radiation would be just a few degrees above absolute zero, would be the same magnitude everywhere, and would obey a perfect blackbody spectrum. These predictions were borne out spectacularly well, eliminating alternatives like the Steady State theory from viability. (NASA / GODDARD SPACE FLIGHT CENTER / COBE (MAIN); PRINCETON GROUP, 1966 (INSET))

    Over the subsequent years and decades, the evidence for the Big Bang has strengthened by extraordinary amounts, with large-scale structure, primordial light element abundances, and the specific properties and temperature fluctuations in the CMB all in agreement.

    But in 1964, it was a serendipitous accident that resulted in the discovery of the Big Bang’s leftover glow for the very first time. The scientists who unwittingly found it went on to win the Nobel Prize in Physics for their discovery, with Jim Peebles only getting his due 41 years later. Still, this truly accidental discovery only occurred because of Penzias’s and Wilson’s insistence on tracking down the source of that unexpected, omnidirectional noise. There’s an old saying that one astronomer’s noise is another astronomer’s data. By carefully examining every unexplained signal, even the ones you never anticipated, sometimes you can even make a discovery that revolutionizes the Universe.

    See the full article here .


    Please help promote STEM in your local schools.

    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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