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Thursday, November 5, 2009 | Science : Astronomy | print version Print | Comments |

Document Dark Matter And Dark Energy Make Up 95 Percent Of Universe, Detailed Measurements Reveal

by ScienceDaily

Thanks to SPS for the link.
http://www.sciencedaily.com/releases/2009/11/091102121644.htm

blankScienceDaily (Nov. 3, 2009) — A detailed picture of the seeds of structures in the universe has been unveiled by an international team co-led by Sarah Church of the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, and by Walter Gear, of Cardiff University in the United Kingdom. These measurements of the cosmic microwave background -- a faintly glowing relic of the hot, dense, young universe -- put limits on proposed alternatives to the standard model of cosmology and provide further support for the standard cosmological model, confirming that dark matter and dark energy make up 95% of everything in existence, while ordinary matter makes up just 5%.

"When I first started in this field, some people were adamant that they understood the contents of the universe quite well," said Church, deputy director of KIPAC and the U.S. principal investigator of the QUaD project. "But that understanding was shattered when evidence for dark energy was discovered. Now that we again feel we have a very good understanding of what makes up the universe, it's extremely important for us to amass strong evidence using many different measurement techniques that this model is correct, so that this doesn't happen again."

In a paper published in the November 1 issue of The Astrophysical Journal, QUaD researchers release detailed maps of the cosmic microwave background (CMB). The researchers focused their measurements on variations in the CMB's temperature and polarization to learn about the distribution of matter in the early universe. Polarization is an intrinsic extra "directionality" to all light rays that is at right angles to the light ray's direction of travel. Although most light is unpolarized -- consisting of light rays with an equal mix of all polarizations -- the reflection and scattering of a light ray can create polarized light. This property of light is exploited by polarized sunglasses, which block some of the polarized light to reduce glare on sunny days.
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http://www.sciencedaily.com/releases/2009/11/091102121644.htm

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1. Comment #429678 by AMreasonedthinker on November 5, 2009 at 3:18 pm

 avatarI think someone mentioned this in another thread but i highly recommend watching ' a universe from nothing' by Lawrence Krauss on youtube. About an hour long and utterley inspiring. He discusses this, the weight of dark matter, red light shift, the fact that 'nothing' is certainly anything but and expounds the virtues and achievements of recent science brilliantly.

P.S any spelling mistakes in this or any additional posts are actually typing errors :-)

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2. Comment #429685 by emactan on November 5, 2009 at 3:47 pm

In Krauss' talk I remember he said that ordinary matter and energy make up only 1% of the total. Guess he was a bit off there. The thing that most piqued my interest is his revelation that the universe could have come from nothing. I wonder if the last gap religionists have to shove their deity in will eventually be taken away from them as well.

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3. Comment #429686 by AMreasonedthinker on November 5, 2009 at 3:50 pm

 avatarI know, the fact that the only type of universe that could originate from nothing (via quantum fluctuations) is ours!! Also the fact that the universe is flat ..... i could go on and on. the number of revelations in one talk is truly astounding.

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4. Comment #429687 by NewEnglandBob on November 5, 2009 at 3:54 pm

 avatar

The light from the early universe was initially unpolarized but became polarized when it struck moving matter in the very early universe.

If it is initially unpolarized, then while hitting moving matter, wouldn't it become randomly polarized, so therefore remain unpolarized?

Why would hitting moving matter make it polarized in one way?

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5. Comment #429709 by Jos Gibbons on November 5, 2009 at 4:54 pm

Comment #429687 by NewEnglandBob

My best guess is that, after the light is absorbed by matter, it is re-emitted in a particular polarisation because of the selection rules governing which emission transitions are possible. (Electrons can't move from any old state to any other, even if the target is unoccupied, because angular momentum has to be conserved and photons have a specific angular momentum, and also because for a non-zero probability the transition must change the parity of the spatial part of the electron's wavefunction.) There is a quantum number which is conserved when plane-polarised light is emitted or changed when circularly polarised light is emitted, so the light's polarisation is probably down to what is allowed to happen to that number (called ml IIRC). However, if my guess is wrong, anyone who knows more about it than me (Steve, perhaps?) is welcome to explain it all.

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6. Comment #429711 by andersemil on November 5, 2009 at 5:00 pm

 avatar
In Krauss' talk I remember he said that ordinary matter and energy make up only 1% of the total.


I haven't watched the talk, but I find that highly unlikely. It has been widely accepted for many years that there are vast amounts of dark matter inside galaxies, otherwise they would not spin the way they do, where all points move at equal angular velocity. But the number could very well have increased as far as from 50% to 95%

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7. Comment #429718 by AMreasonedthinker on November 5, 2009 at 5:08 pm

 avatarI have watched it twice (although both time late at night and rather 'tired' :-)

But I dont recall if he said 1% - 5% sounded right to me but either way it is an astonishing concept? reminds me of (carl sagen I think) when talking about the possible existence of there being other life in the universe.

(paraphrasing)Either there is other life in the Universe or there is not. Both are truly fascinating concepts!

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8. Comment #429722 by Geraint on November 5, 2009 at 5:37 pm

There's a page eplaining CMB physics here, which might be useful to people trying to understand the polarization stuff:
http://background.uchicago.edu/~whu/

It does get quite technical though. The scattering of light from free electrons does depend on polarization. The reason you end up with a net polarization at some point rather than everything cancelling out is because radiation reflected from different directions ends up with a different polarization. A region of the Universe will receive different amounts of radiation from different directions (because the Universe isn't completely homogeneous).

The signal is weak though: polarization measurements are much harder to do than total intensity measurements.

Regarding the amount of 'ordinary matter' in the Universe, current estimates are that it makes up about 4.6% of the critical density. Dark matter makes up about 22.8%, so you end up with a total of about 27% of the critical density coming from matter. The rest comes mainly from dark energy, with a very small contribution from radiation. It's thought that the total comes to something very close to 100% of the critical density.

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9. Comment #429744 by bamafreethinker on November 5, 2009 at 6:41 pm

 avatarYou can clearly see the FSM in that image (the red sections near the center). PROOF!

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10. Comment #429745 by j.mills on November 5, 2009 at 6:47 pm

 avatarDark energy is everywhere, but you can't see or feel it. Everything in the universe resides inside dark energy.

Hmm...

IT'S GOD!!! The biggest gap of all!

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11. Comment #429750 by Gorgonzola on November 5, 2009 at 7:01 pm

Funnily enough, j. mills, a colleague of mine was explaining to me only recently that she reconciled her religious faith and her physics doctorate by thinking of dark matter as God.

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12. Comment #429764 by Jos Gibbons on November 5, 2009 at 7:46 pm

Comment #429750 by Gorgonzola

I wonder if she thinks it created everything, or answers prayers, or judges people in their afterlife, or hates people of a certain belief or predisposition, or was behind a holy book, or any of the other properties of a REAL god. Pantheism drives me nuts.

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13. Comment #429795 by hiraethog on November 5, 2009 at 8:35 pm

Comment #429744 by bamafreethinker

You could be on to something there! He just likes us to think that it's 95% dark matter to test us out! What a genius He is! BTW, there was one bit of the article I didn't quite get - What exactly is dark matter? or matter for that matter?
Ramen

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14. Comment #429922 by andersemil on November 6, 2009 at 7:01 am

 avatarJust as a follow-up, I'm watching the Laurence Krauss talk mentioned now and he says that 90% of the total mass in galaxies comes from dark matter. 70% of the total energy in the universe is dark energy (the energy of empty space), nearly 30% is dark matter and normal matter is less than 1%. Excellent talk, btw, can heartily recommend it.

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15. Comment #429927 by zecat on November 6, 2009 at 8:29 am

 avatarAbout Krauss' talk: excellent indeed, but I have to admit he lost me when he talked about quantum fluctuations of "nothing". How can "nothing" fluctuate? Nothing is nothing, right?.. What am I missing?..

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16. Comment #429950 by AMreasonedthinker on November 6, 2009 at 10:50 am

 avatarzecat

(apols, not sure how to quote yet) did you see the visual he demonstrated inside the proton? It was wither Universe form nothing lecture or the origins speach he gave recently which was similar but without the religious references

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17. Comment #429960 by zecat on November 6, 2009 at 12:08 pm

 avatarAM

Yes, I did see that. But how can the inside of a proton qualify as "nothing"? Same goes for his imaginary 1 cm3 of intergalactic vacuum. An observer inside this 1 cm3 could measure all sorts of radiations and gravitation. So how could this be considered as "nothing"? Inside a proton, isn't there electrical and gravitational fields? So, how could this be "nothing"? Or, what's the definition of "nothing"? It sounds to me more like what they discovered is that there's nothing like "nothing" in our universe.

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