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Echoes Hint At Accelerating Universe Expansion
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."
... is how long before the RIAA muscles in and starts suing us astronomers for "collecting data".
Sheesh.
Oddly enough the above got labelled "Offtopic" and not "Troll". Perhaps there is some truth to this after all...
God: Hello!
[400,000 years later]
Universe: Hello, hello, lo, lo, lo, o...
(or was that Eddies in the time-space continuum?)
Lump lingered last in line for brains, and the ones she got were sorta rotten and insane.
The Eternal Library has some very strict rules on whispers.
The message on the other side of this sig is false.
It must be the dark side of The Force.
- Never underestimate the power of human stupidity.
Slashdotted at 5 comments. Here's the article text (after a 4 minute wait.)
. asp). The universe's first symphony therefore provides independent evidence that the cosmos is filled with dark energy, which causes the acceleration.
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
There are lies, damned lies, and statistics.
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
It was, and still remains, a very good talk about the accelerating expansion of the universe.
There's no place like ~/
"Dark energy" and "dark matter" are just ways of saying "energy we can't find" and "matter we can't find," (respectively,) right?
~UP
Eat the Path.
Just exactly how fast does an acoustic wave travel through a vaccuum?
I see even classic Slashdot is now pretty much unusable on dial up anymore.
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...
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.
Just like I said! Good one, Matt!
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 matter that the waves are passing through? Yes, I think you can, but, if this is just a vibing molecule having a hippy time... these 'accoustics' are really not travelling through matter are they, so are they accoustic? (I cannot be bothered to lookup our meaning of the greek word accou (I hear, well actually 'accou?' means can you hear me))
I am confuzzled. I can imagine radiation waves (energy) being measured in this way, but then it comes down to, how can they be sure what they measured?
#hostfile 0.0.0.0 primidi.com 0.0.0.0 www.primidi.com 0.0.0.0 radio.weblogs.com
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 in the universe by a factor of ~7. It's not just stuff we haven't seen, it's stuff we can't see (at least not in ordinary ways). This weird stuff is also required by current models to explain how structure forms in the universe.
Dark energy is also "energy we can't find", but it's a lot more than that. "Dark energy" is the name given to whatever phenomenon is causing the expansion of the universe to accelerate (as noticed by the research in this article, as well as earlier work studying distant supernovae). It has an anti-gravity-like behavior, which is weird (to say the least).
So on the one hand, dark energy and dark matter are just the "missing" stuff we need to throw in to get our estimates of the amount of visible matter and the amount of total matter to jibe. Both components do have very strange properties which affect the way the universe is today, however, so whatever stuff they are made of is very unusual!
Hubble found that nearby objects are red shifted and objects farther away are even more red shifted.
:P
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 is at an infinite distance away everything will appear red shifted in exactly the same way it does now.
Objects closer than us to the singularity will appear to be accelerating away. Although objects further away from the singularity will still be falling in, they won't be accelerating as fast as us (who are nearer) so they'll appear to be shooting away from us as well.
Objects perpendicular to the direction of acceleration will appear blue shifted but only if they are *exactly* perpendicular. If the singularity is an infinite distance away that slice of space were blue shifting will occur will be infinitely thin (hence won't exist).
So there.
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]