Dark matter 'proof' called into doubt
a.. 09 September 2006
b.. Stuart Clark
c.. Magazine issue 2568
WHEN Douglas Clowe of the University of Arizona in Tucson announced on 21 August that his team had "direct proof of dark matter's existence", it seemed the issue had been settled. Now proponents of the so-called modified theories of gravity, who explain the motion of stars and galaxies without resorting to dark matter, have hit back and are suggesting that Clowe's team has jumped the gun.

"One should not draw premature conclusions about the existence of dark matter without a careful analysis of alternative gravity theories," writes John Moffat, of the University of Waterloo in Ontario, Canada, who pioneered an alternative theory of gravity known as MOG (http://www.arxiv.org/astro-ph/0608675).

The controversy centres on the pattern of gravitational lensing, or the bending of light, around the Bullet cluster of galaxies, which formed from the collision of two clusters. While most of the Bullet cluster's visible mass lies in a pool ...

Source: NewScientist (Requires subscription - arxiv paper is free)
http://www.newscientistspace.com/art...mg19125684.200


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Posted by
Robert Karl Stonjek

Robert Karl Stonjek wrote:

Dark matter 'proof' called into doubt

* 09 September 2006
* Stuart Clark
* Magazine issue 2568

WHEN Douglas Clowe of the University of Arizona in Tucson announced on
21 August that his team had "direct proof of dark matter's existence",
it seemed the issue had been settled. Now proponents of the so-called
modified theories of gravity, who explain the motion of stars and
galaxies without resorting to dark matter, have hit back and are
suggesting that Clowe's team has jumped the gun.

"One should not draw premature conclusions about the existence of dark
matter without a careful analysis of alternative gravity theories,"
writes John Moffat, of the University of Waterloo in Ontario, Canada,
who pioneered an alternative theory of gravity known as MOG
(http://www.arxiv.org/astro-ph/0608675).

The controversy centres on the pattern of gravitational lensing, or the
bending of light, around the Bullet cluster of galaxies, which formed
from the collision of two clusters. While most of the Bullet cluster's
visible mass lies in a pool ...

Source: NewScientist (Requires subscription - arxiv paper is free)
http://www.newscientistspace.com/art...mg19125684.200
http://www.newscientistspace.com/article/mg19125684.200?DCMP=NLC-nletter&nsref=mg19125684.200


--
Posted by
Robert Karl Stonjek


More on Dark Matter

21 Aug 2006 - NASA announced updated information about the "bullet
cluster" 1E0657-56 today. Two clusters of galaxies have recently
collided in this X-ray source. This cluster is filled with hot gas so
X-ray observations by the Chandra X-ray Observatory show where the
ordinary matter is located. 90% of the ordinary matter (the "baryonic"
matter) is hot gas. The new results [Clowe et al., Bradac et al.] use
gravitational lensing of background galaxies to show where the sources
of gravity are located. The sources of gravity in the cluster are not
located where the ordinary matter is located, so this cluster is a
counter-example to MOND. All of this was known in 2003 but with less
precision. Sean Carroll has a nice post about this at Cosmic Variance

See: http://www.astro.ucla.edu/~wright/cosmolog.htm#News

Robert Karl Stonjek wrote:

[...]

Interesting article, thanks. MOG seems worth looking at, barring some
major problem I'm unaware of.

It does make one important point that I think is worth considering:

"We learn from the results presented here that one should not draw
premature
conclusions about the existence of dark matter without a careful
analysis of alterna-
tive gravity theories and their predictions for galaxy lensing and
cluster lensing, in
particular, for the interacting cluster 1E0657-56."

That being said, I am amused that MOND still isn't getting it right and
is still considered viable anyway by some folks.

Robert Karl Stonjek wrote:
Dark matter 'proof' called into doubt
a.. 09 September 2006
b.. Stuart Clark
c.. Magazine issue 2568


They observed deviations from motion predicted by the GR field
equations. This deviation was predicted by one of various _inferred
models_ of Dark Matter. According to the scientific establishment, this
constitutes proof of the existence of Dark Matter!

In other words,

1. Gravity makes things fall up.

2. Experiment reveals things fall down.

3. There must exist 'fairy dust' which interacts with the equations of
1 such that 1 is not falsified by 2.

4. The more experiments that show things fall down, the more evidence
there is for 'fairy dust' and the underlying gravity theory.


Replace (1) with General Relativity and 'fairy dust' with Dark Matter,
and that's pretty much what Modern Cosmology has become - a historical
laughing stock.

wrote:
Robert Karl Stonjek wrote:
Dark matter 'proof' called into doubt
a.. 09 September 2006
b.. Stuart Clark
c.. Magazine issue 2568


They observed deviations from motion predicted by the GR field
equations. This deviation was predicted by one of various _inferred
models_ of Dark Matter. According to the scientific establishment, this
constitutes proof of the existence of Dark Matter!

You have no idea what constitues proof, much less what the word "proof"
means.

Your insane ranting about 9/11, the moon landing, and everything else
is a decent demonstration of your ability to understand a topic.


In other words,

1. Gravity makes things fall up.

Dead on arrival. Gravity does not make things fall up, nor does GR or
Newton say that it does.

Why do you post to sci.physics if every time you speak you get it
wrong?

[...]

Eric Gisse wrote:
wrote:
Robert Karl Stonjek wrote:
Dark matter 'proof' called into doubt
a.. 09 September 2006
b.. Stuart Clark
c.. Magazine issue 2568


They observed deviations from motion predicted by the GR field
equations. This deviation was predicted by one of various _inferred
models_ of Dark Matter. According to the scientific establishment, this
constitutes proof of the existence of Dark Matter!

You have no idea what constitues proof, much less what the word "proof"
means.

Your insane ranting about 9/11, the moon landing, and everything else
is a decent demonstration of your ability to understand a topic.


In other words,

1. Gravity makes things fall up.

Dead on arrival. Gravity does not make things fall up, nor does GR or
Newton say that it does.

Why do you post to sci.physics if every time you speak you get it
wrong?
What's the symbol for something going
right over someone's head?
/:-)?
John