It is currently Thu Oct 17, 2019 6:55 pm


Post new topic Reply to topic  [ 5 posts ] 
Author Message
PostPosted: Thu Jul 22, 2010 1:11 am 
Offline

Joined: Sun Aug 13, 2006 12:29 pm
Posts: 663
Location: Goosnargh, north of Preston, UK
The National Radio Astronomy Observatory (NRAO) have issued the following press release. See here for full details.

Quote:
Radio Astronomers Develop New Technique for Studying Dark Energy (July 21, 2010) : Pioneering observations with the National Science Foundation's giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. The new tool promises to provide valuable clues about the nature of the mysterious "dark energy" believed to constitute nearly three-fourths of the mass and energy of the Universe...

_________________
David Entwistle


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Thu Jul 22, 2010 7:50 pm 
Offline

Joined: Sat Dec 11, 2004 8:18 pm
Posts: 6501
Location: Manchester
Dear David
According to August's Sky at Night Magazine recent assessments suggest that there might be errors in NASA's WMAP satellite data as a result of which the amounts of Dark Matter and Dark Energy might be significantly less than previously thought.
Researchers at Durham University are now questioning the conventional wisdom that the Universe is dominated by dark matter and dark energy.
Best wishes from Cliff


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Sat Jul 24, 2010 9:55 am 
Offline

Joined: Sun Aug 13, 2006 12:29 pm
Posts: 663
Location: Goosnargh, north of Preston, UK
Cliff wrote:
Dear David
According to August's Sky at Night Magazine recent assessments suggest that there might be errors in NASA's WMAP satellite data as a result of which the amounts of Dark Matter and Dark Energy might be significantly less than previously thought.
Researchers at Durham University are now questioning the conventional wisdom that the Universe is dominated by dark matter and dark energy.
Best wishes from Cliff


Hi Cliff,

I need to do some more reading to follow this, but the WMAP results are available here and here I think the Hinshaw et al paper, which is being challenged, is here. The University of Durham press release, which details the report challenging some of the findings, is available here. I think the Utane Sawangwit & Tom Shanks paper referred to is available here - this paper certainly outlines the thrust of the argument.

The paper is too technical for me to understand - I think they're talking about uncertainties regarding gain profile and side-lobes in the beam profile of the instrument, but I'm not sure. The paper certainly opens in a rather strident way....

Quote:
The standard λCDM cosmological model is a quite perplexing mixture of impressive observational successes (e.g. Hinshaw et al. 1, Komatsu et al. 2, Hicken et al. 3, Kessler et al. 4) coupled with wider implications which make the model complicated to the point of implausibility.


They then go on to detail the implications and add...

Quote:
The above issues mean that the standard model requires remarkable observations in its support and the most remarkable of these is represented by the acoustic peaks in the CMB power-spectrum as measured by WMAP (eg Hinshaw et al. 14) and other CMB experiments....


It'll be interesting to see how this plays out.

_________________
David Entwistle


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Sat Jul 24, 2010 3:20 pm 
Offline

Joined: Sat Dec 11, 2004 8:18 pm
Posts: 6501
Location: Manchester
Dear David
All these matters are well beyond me really.
However, in my simplistic way of looking at things I'm no big fan of dark matter and dark energy. Indeed since "inflation got invented" cosmology has rather seemed to go down hill for me.
That said I recently attended a talk by an advanced student in cosmology and from what they said I thought I detected a possible threat to what I sometimes think may be a sort of "computer modelling over-confidence" in a modern cosmology. But then again I sometimes think it might be wishful bad-thinking on my part.
After all I have neither the matematical, computer skills, nor observations to back my wishful thinking up.
Best wishes from Cliff - But I'll say Mond for ever !!!


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Sun Jul 25, 2010 11:12 am 
Offline

Joined: Sun Aug 13, 2006 12:29 pm
Posts: 663
Location: Goosnargh, north of Preston, UK
Cliff wrote:
Dear David
All these matters are well beyond me really.


Hi Cliff,

I've read, or at least scanned, a number of the papers relevant to the WMAP debate and I think I've got the thrust of the argument, but the details are complex and largely beyond me. However, while reading up on the subject I did come across this very nice image, which featured in APOD, several years ago. The dipole is just one of the foreground effects which needs to be removed to get at the cosmic background...

COBE Dipole: Speeding Through the Universe
Image
Credit: DMR, COBE, NASA, Four-Year Sky Map

Quote:
Explanation: Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group of Galaxies. The Local Group falls toward the Virgo Cluster of Galaxies. But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background (CMB). In the above all-sky map, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder. The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation. This high speed was initially unexpected and its magnitude is still unexplained.


See the above link for additional details.

_________________
David Entwistle


Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group