[ExI] Dark doubts

[Damien Broderick]

On 6/17/2010 1:14 AM, Gregory Jones wrote:

>  >   What about the 96% of all that is that isn't atoms and photons?  - s
>
> We lose that.  For now.  Unless or until all that computronium figures
> out how to make use of it to create more computronium, in which case the
> fun is multiplied by a factor of 25.

Maybe it's not even there:

Doubts about universe's dark side
Thursday, 17 June 2010

by Heather Catchpole
Cosmos Online

SYDNEY: Errors in the way physicists estimate the effects of dark matter 
and dark energy on the leftover heat from the Big Bang has thrown their 
existence into doubt, say British scientists.

Physicists' general model of the universe includes two 'dark' concepts.

Dark energy is a force that explains the way that galaxies accelerate 
away from each other, while dark matter was postulated to explain the 
observations that galaxies have more mass than can be accounted for by 
stars and gas.

Evidence for the 'dark side' comes primarily from studies of the Cosmic 
Background Radiation (CMB), the leftover 'glow' from the Big Bang, which 
has been analysed in detail by the Wilkinson Microwave Anisotropy Probe 
(WMAP), a NASA satellite telescope launched in 2001 that provided the 
first full-sky map of the CMB.

Large errors in WMAP data

Now, some scientists say errors in the WMAP data may be larger than 
expected.

This would mean that there is no need to include dark matter and dark 
energy in models of the cosmos.

Their results have been accepted for publication in the journal Monthly 
Notices of the Royal Astronomical Society.

Results still need to be proven

"If our results prove correct then it will become less likely that dark 
energy and exotic dark matter particles dominate the universe," says 
astronomer Tom Shanks from Durham University, in England.

"So the evidence that the Universe has a 'dark side' will weaken."

WMAP data shows ripples in the CMB that are linked to the composition of 
the universe, thought to be roughly 4% normal matter to 22% dark matter 
and 74% dark energy.

Dark matter a result of telescope adjustment?

"Big ripples in the CMB imply a cold dark matter component for the 
Universe. Our question is whether the large size of these ripples can be 
caused by the WMAP telescope over-smoothing the CMB data due to optical 
effects," Shanks told Cosmos.

Shanks and graduate student Utane Sawangwit were also part of a team 
that last year found other data that supports doubts about dark matter 
(Monthly Notices of the Royal Astronomical Society, Dec 2009).

Data from the Sloan Digital Sky Survey, 2.5 metre telescope in New 
Mexico that is mapping one-quarter of the sky, showed that photons 
travelling through clusters of galaxies aren't red-shifted in their 
wavelengths by the clusters' gravity as much as the standard dark matter 
model predicts.

"If our result is repeated in new surveys of galaxies in the Southern 
Hemisphere then this could mean real problems for the existence of dark 
energy," says Sawangwit.

Dark matter model still strong, experts say

But Australian astronomer Geraint Lewis says the dark matter model 
"hasn't fallen over yet".

"It's not a religious creed - it should be tested, but it has held up 
every time someone has taken a swing at it," he says.

Evidence for dark energy also comes from other areas of astronomy, such 
as the High-Z supernova search, he points out.

"Even if the CMB is out, it might make us more uncertain but I don't 
think there is enough slop [in the WMAP data] to make dark matter and 
dark energy go away," he says.