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Space Science

Echoes Hint At Accelerating Universe Expansion 41

Posted by timothy from the say-that-12-times-quickly dept.
cr0kin0le writes "400,000 years after the Big Bang, oscillations between gravitationally contracting matter and outward radiation pressure left newly discovered acoustic echoes. Independent teams from U. of Arizona and U. of Durham, England have found circular ripples with wavelengths of 500 million light-years which indirectly imply that universal expansion is accelerating due to dark energy."
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Echoes Hint At Accelerating Universe Expansion More

Echoes Hint At Accelerating Universe Expansion

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  • ... is how long before the RIAA muscles in and starts suing us astronomers for "collecting data".

    Sheesh.

  • Acoustic Echos? (Score:4, Funny)

    by Ignominious Cow Herd ( 540061 ) on Tuesday January 18, 2005 @12:44AM (#11392555) Journal
    God: Hello!

    [400,000 years later]

    Universe: Hello, hello, lo, lo, lo, o...

    (or was that Eddies in the time-space continuum?)
    • Just because our God takes 20.7 billion year vacations ?
    • "Eddies," said Ford, "in the space-time continuum."
      "Ah," nodded Arthur, "is he. Is he." He pushed his hands into the pockets of his dressing gown and looked knowledgeably into the distance.
      "What?" said Ford.
      "Er, who," said Arthur, "is Eddy, then, exactly, then?"

      From Life, the Universe and Everything by Douglas Adams

      *wipes away tear*
  • The Eternal Library has some very strict rules on whispers.
  • Eisenstein notes that, using the length of the sound waves as a cosmic ruler, astronomers can calculate the universe's expansion. Both of the new studies agree with earlier reports that cosmic expansion is speeding up. The universe's first symphony therefore provides independent evidence that the cosmos is filled with dark energy, which causes the acceleration.

    It must be the dark side of The Force.

  • slashdotted (Score:3, Informative)

    by roseblood ( 631824 ) on Tuesday January 18, 2005 @12:53AM (#11392581)
    Slashdotted at 5 comments. Here's the article text (after a 4 minute wait.)

    Ultimate Retro: Modern echoes of the early universe

    Ron Cowen

    Two teams of astronomers have for the first time detected the surviving notes of a cosmic symphony created just after the Big Bang, when the universe was a foggy soup of matter and radiation. The discoverers say that the survival of the acoustic imprint from this early epoch, 13.7 billion years ago, provides compelling new evidence that the blueprint for the present distribution of galaxies was set at the time of the Big Bang by random subatomic fluctuations.

    In 1999, researchers detected a specific pattern of acoustic oscillations in the faint, ancient whisper of radiation--the cosmic microwave background--left over from the Big Bang. This week, Shaun Cole of the University of Durham in England and his colleagues announced that they had discerned remnants of that pattern while analyzing data from the Two-Degree Field Redshift Gravity Survey, a large-scale analysis of 220,000 galaxies. The map covers one-twentieth the area of the sky out to a distance of 2 billion light-years from Earth.

    Another team, led by Daniel Eisenstein of the University of Arizona in Tucson, examined a subset of 46,000 galaxies from another sky map, the Sloan Digital Sky Survey, which covers one-quarter of the sky.

    Each team used a different method of analysis but found the same acoustic pattern. The groups reported their findings this week at a meeting of the American Astronomical Society in San Diego.

    The signals are so weak that, to detect them even in large-galaxy surveys, "both groups had to work quite hard," notes cosmologist David N. Spergel of Princeton University. "The result is another important milestone in establishing a standard model for cosmology."

    The early universe rang like a bell, notes Spergel. As gravity drew together clumps of atomic matter, radiation--then tightly bound to that matter--exerted an outward pressure. The tug-of-war between gravity's pull and radiation's push generated pressure waves, or acoustic oscillations.

    About 400,000 years after the Big Bang, the universe had cooled sufficiently for the radiation to break free from matter and travel unimpeded into space. Now in the form of microwaves, this radiation pervades the universe and provides a snapshot of the cosmos at that early time, ripples and all.

    The small size of the fluctuations, both in the microwave background and the galaxy distribution today, provides additional evidence that most of the mass of the universe is composed of dark matter--an exotic, invisible, and primordial material that has never interacted with light and so had never generated sound waves, notes Spergel.

    Eisenstein notes that, using the length of the sound waves as a cosmic ruler, astronomers can calculate the universe's expansion. Both of the new studies agree with earlier reports that cosmic expansion is speeding up (SN: 5/22/04, p. 330: http://www.sciencenews.org/articles/20040522/bob9. asp). The universe's first symphony therefore provides independent evidence that the cosmos is filled with dark energy, which causes the acceleration.

  • at a campus lecture at my college. The professor gave very good evidence that the universe is expanding at an accellerating rate. The devotional was called "Exploding Stars, Expanding Universe."

    Unfortunately, the school does not have a transcript of the forum, but you can download it in mp3 format for free [byu.edu]

    It was, and still remains, a very good talk about the accelerating expansion of the universe.

    • You've got some big ears, if you heard sounds with wavelengths of 500 million light-years.
    • The methodology used in that study is to look for a specific type of supernova explosion (called Type Ia) and use it as a measure for distance indicator. Such studies have shown that the Universe is not only expanding but also accelerating in expansion.

      In this new topic, the same result is obtained, but with much different methodology being used: detection of density wave at its early stage of evolution in the large scale structure of the Universe. Not that I'm familiar with this latest news. Time to read
  • "Dark energy" and "dark matter" are just ways of saying "energy we can't find" and "matter we can't find," (respectively,) right?

    ~UP

    • Re:someone remind me... (Score:1, Funny)

      by Anonymous Coward
      Dark matter is what Dark Jedi are made of, and Dark Energy powers their Dark Sabers.
    • ...Or dark energy could be a nifty projectile for the Overwatch pulse rifle from a certain game that makes other players "energy we can't find" and "matter we can't find"...

    • Re:someone remind me... (Score:5, Informative)

      by The Datamangler ( 850803 ) on Tuesday January 18, 2005 @05:29AM (#11393510) Journal
      That's what I thought too, but no. It seems dark energy is stuff we can't see using traditional electromagnetic methods. It seems that vacuum energy may be one of the sources of dark energy- there is energy associated with the vacuum of space. If you place 2 metal plates parallel to each other, there is an energy potential between them caused by the vacuum of space(Casimir effect). Kip Thorne describes how to make a time machine this way with sufficiently large plates. (sufficiently large is pretty fu***n big) Also, you may have read that in deep space subatomic particles pop in and out of existence- this is part of the dark energy, too, and somehow related to vacuum energy. For a mildly technical discussion go to http://www.astro.ucla.edu/~wright/cosmo_constant.h tml Also, I recommend Brian Greene's "The elegant Universe" for a superb laymans terms description of the state of knowledge and confusion in astrophysics.
    • That's almost it, but not quite.

      Dark matter is indeed "matter we can't find". It can't, however, be comprised entirely of, for example, gas or planets or tiny stars that we haven't discovered. From various lines of evidence, one can deduce that the vast majority of the missing matter cannot be made up of ordinary matter (stuff made up of protons, electrons, atoms). The best guess is that the dark matter is some kind of stuff that doesn't interact with light, but that outweighs all the visible matter i
    • Both are terms for gravitational energy / particles, but the people who use the 'dark' terms don't know it yet.

      They'll figure it out eventually.

      Rik
  • Just exactly how fast does an acoustic wave travel through a vaccuum?
    • "Just exactly how fast does an acoustic wave travel through a vaccuum?"

      Who cares? Space is not a complete vaccuum.

    • Re:Acoustic? (Score:4, Informative)

      by Frans Faase ( 648933 ) on Tuesday January 18, 2005 @07:07AM (#11393812) Homepage
      First of all space is not a vacum, although from our point of view (being in a dense atmosphere) it is often considered as such. Secondly, at the time the waves occured, space was much smaller and thus also denser and hotter. What they have observed is just the traces of those waves, not the waves themselves. It like those sand patterns on the beach that you see when the tide is low.
      • Seriously though, acoustic waves have to move through some medium which is capable of compression and rarefaction and they don't move at the same rate through all such media, travelling more quickly through water than sea level air here on earth (or is it more quickly through air than water? either way it's not the same).

        So, what's the speed of an acoustic wave moving through a near vaccuum? Faster than the expansion rate of the universe? (Does the edge of the universe return echoes?) Slower? Any standin

        • That's EXACTLY the point of the article.

          The acoustic waves are moving through the plasma at the epoch of recombination at temperatures of about 3000 K. Knowing that, and the fact that yes, they do set up standing waves of a sort, let's us determine the rest. Wayne Hu at the University of Chicago has a great set of tutorial webpages explaining how this all works:
          http://background.uchicago.edu/
  • Dark energy or dark matter or whatever dark clever tag you want to give it is just another way of saying " we don't know what it is so we'll make an educated SWAG (scientific wild ass guess)...just so we don't have to admit to anyone taht that we don't know...

    • Re:PFFFHHHH (Score:3, Interesting)

      by TeknoHog ( 164938 )
      Dark energy or dark matter or whatever dark clever tag you want to give it is just another way of saying " we don't know what it is so we'll make an educated SWAG (scientific wild ass guess)...just so we don't have to admit to anyone taht that we don't know...

      I agree to some extent. It seems too complicated. One problem is IMHO that General Relativity is taken as an absolute gospel, and then we need all these complications to make observations fit theory. Whereas other theories besides GR can explain th

      • Re:PFFFHHHH (Score:3, Informative)

        by radtea ( 464814 )

        From the linked site: "Today's physicist may start his lecture by convincing the audience that there is no understandable logics behind natural phenomena; it is out of date to look for a common sense picture of the physical reality."

        The latter claim (it is out of date to look for a common sense picture of physical reality) is certainly true, and has been true since Newton's time. Newton's theory of gravitation was criticized for being in violation of common sense and being based on "occult qualities".

        Th
      • Very interesting link. Thx!
        It's hard to break the innital resistance towards non-Relativity-based cosmology, without falling into the crackpot theory/pseudoscience realm.

  • Just a illusion (Score:2, Interesting)

    by lazy genes ( 741633 )
    The expansion rate of the expansion of the universe might equal the contraction rate between andromeda and the milkyway.Gravitational lensing in reverse. Can the fabric of space-time around the milky way warp to create this illusion.Dark matter and d-energy could be explained by the contraction and expansion of space-time . I also would like to know why the cmb cant be a phase change of some kind.I know Greenbay cannot be anywhere close to the center of the universe.
  • wavelengths of 500 million light-years

    To find the frequency, don't you have to wait for at least half the frequency to know it? How can they accurately extrapolate a length of 500MLY from about 1LY of data (if indeed they took that length of reading).

    I mean, how accurate could they measure this? what about if it was a really really high frequency weak signal that was bent by a star?

    How do accoustics travel in space? Can you measure the volume and frequency of sound in a room by measuring one molecule of
    • Also, you crazy astrologers, if LS is supposed to be slowing down (or has, or will have would have been in the future, have been...) depending on your point of view.... does this make you nice round 500MLY figure anyless accurate or reliable.

      Also, what are the chances of it being square on 500MLY!! not a tilde in sight!

      ~500MLY ± 1GLY (+/-)
    • To find the frequency, don't you have to wait for at least half the frequency to know it?

      You are partially correct. You need to see at least half of the wave to measure its wavelength. To get the frequency from the wavelength you generally need to know the speed of the wave.

      How can they accurately extrapolate a length of 500MLY from about 1LY of data (if indeed they took that length of reading).

      I think you are confusing lightyears and years. A lightyear is a unit of length. The astronomers here have m

      • I was not confusing what a light year was. I was assuming that the radio wave was travelling ~LS (isn't this the case?)

        I realised after I posted that they would use galaxies 'that far away' to get a cross section, but then I thought, a cross section of what? radiation from those galaxies? radiation from galaxies behind?

        actually, the 3d thingy did look like a FT.

        Makes more sense... so they have tried to spot the ripples in the galxy distribution themselves?

        not actually some wave that is passing through
        • Makes more sense... so they have tried to spot the ripples in the galxy distribution themselves?

          Yes, that is correct. They are looking at the patterns in the distribution of galaxies. They are not detecting radio waves. They are infering accoustic waves (i.e. longitudinal "pressure" waves that propagated through the hot dense matter-radiation soup of the early universe) from the pattern left behind after matter and radiation decoupled. Pretty neat trick, really.

  • Hubble found that nearby objects are red shifted and objects farther away are even more red shifted.

    These observations were explained by saying that the universe is expanding and doing so at an accelerating rate. We've now spent decades trying to adjust this theory to fit new observations.

    What if the original explanation of the observations was backwards?

    Our observations of an expanding universe can also be explained by a collapsing universe. If you simply let the universe fall into a singularity that

  • Brief description (Score:4, Informative)

    by TMB ( 70166 ) on Tuesday January 18, 2005 @07:49PM (#11403407)
    (aside: why is it that the majority of comments on any astrophysics story are really really lame off-topic jokes? I mean, even worse than in your average /. story, which is saying something...)

    Since it looks like most people here haven't read the journal articles (the sciencenews.org article is pretty light on the details), here's the basic idea:

    In the early universe, the universe is mostly smooth except for small density fluctuations. The universe is made up of 3 basic fluids: photons, dark matter, and baryons. Density waves ("acoustic waves") pass through these fluids as far as they can at a given time - in the early universe, the horizon scale is quite small and the waves can't get all that far. Therefore you get horizon-sized acoustic oscillations. Dark matter is pressureless while the photon-baryon fluid isn't, so they react differently to compression... the end result of that is that there are some oscillations on quite large scales that are there because of the baryons.

    What these groups have done using two different surveys (the 2 degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS - they're using the Luminous Red Galaxy (LRG) subsample)) is look at galaxies at moderate redshift (medians of about 0.1 for 2dFGRS and 0.35 for the SDSS LRG sample) and compute the correlation function (in Dan Eisenstein's paper) or power spectrum (in Shaun Cole's paper). These tell you how clustered galaxies are as a function of how far away they are from each other.

    What they both find is that there's a peak around 150 Mpc, exactly as you'd expect for a universe with about 75% vacuum energy and 25% matter, of which about 15% (ie. 15% of 25% = 4% total) is baryonic. The test is pretty sensitive to all of those numbers, and thus provides further evidence that the universe is dominated by a vacuum energy that drives acceleration.

    Here's links to preprints of the papers:

    [TMB]

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