"The identity of the Universe's dark matter may finally have been
discovered. In what seems to be the most convincing claim for dark matter so
far, researchers in England and France say gamma rays coming from the centre
of our galaxy show hallmarks of these ghostly particles."

http://www.newscientist.com/news/news.jsp?id=ns99994214

;-Peter


--
Visit the laptop of the Gods
http://www.godchecker.com
mythology with a twist

";-Peter Ramsey" wrote:

"The identity of the Universe's dark matter may finally have been
discovered. In what seems to be the most convincing claim for dark matter so
far, researchers in England and France say gamma rays coming from the centre
of our galaxy show hallmarks of these ghostly particles."

http://www.newscientist.com/news/news.jsp?id=ns99994214

Won't work. If dark matter interacts with electrons and positrons
then it is trivially detectable in existing apparatus across a huge
selection of interaction cross-section kinds and amplitudes.

http://www.phys.lsu.edu/mog/mog22/node8.html

"73% dark energy, 22% dark matter and 4.4% baryons." Look at a
galaxy. 5X as much stuff is dark matter. Look around you. 5X of
everything you see is undetectably freely permeating dark matter. "New
Scientist" is all smoke and no fire. They did not adequately state
the case if it was adequately stated at all.

A "reasonable" dark matter candidate would be Super Symmetry
neutralinos. That won't work with the annihalation gamma ray claim. A
less reasonable candidate would be "mirror Matter." It still won't
wash, either way.

Anything of all but vanishing mass subject to gravitation will clump.
If it clumps it catastrophically clumps into black holes - and
intensely concentrated gravitation bends light (Einstein rings) no
matter what the source of gravitation. To have a huge amount of stuff
and not have it aggregate you need a particle with a rest mass so
small that the thermal background during its creation at the Big Bang
made it relativistic (e.g., neutrinos). For it to be invisible on a
galactic scale it must have no electromagnetic, Strong Force, or Weak
Force interactions. If it did, it would have a mechanism to radiate
energy, cool, and collapse into compact objects.

1) If dark matter is relativistic, then it cannot slow electrons
and positrons to a crawl - First Law of Thermodynamics.

2) If dark matter has no electromagnetic, Strong Force, or Weak
Force interactions, then it cannot slow electrons and positrons short
of a "new" mechanism of interaction.

3) If dark matter has no electromagnetic, Strong Force, or Weak
Force interactions, what keeps it from degenerately gravitationally
collapsing? It must be very hot - in terms of energy vs. rest mass
equvalent - indeed.

4) If dark matter does slow (thermalize, actually) electrons and
positrons, then it is trivially detectable in the lab by said
mechanism of slowing.

I don't see the case having been made to explain observed 511 keV
annihalation radiation.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

Uncle Al wrote in message ...
";-Peter Ramsey" wrote:

"The identity of the Universe's dark matter may finally have been
discovered. In what seems to be the most convincing claim for dark matter so
far, researchers in England and France say gamma rays coming from the centre
of our galaxy show hallmarks of these ghostly particles."

http://www.newscientist.com/news/news.jsp?id=ns99994214

Won't work. If dark matter interacts with electrons and positrons
then it is trivially detectable in existing apparatus across a huge
selection of interaction cross-section kinds and amplitudes.

http://www.phys.lsu.edu/mog/mog22/node8.html

"73% dark energy, 22% dark matter and 4.4% baryons." Look at a
galaxy. 5X as much stuff is dark matter. Look around you. 5X of
everything you see is undetectably freely permeating dark matter. "New
Scientist" is all smoke and no fire. They did not adequately state
the case if it was adequately stated at all.

Is the gravitational redshift from/near the center of our galaxy
measurable? If so, is it consistent with the "extra mass" hypothesized
from the stellar rotation curves?

-Bruce

Uncle Al wrote:
To have a huge amount of stuff and not have it aggregate you need a
particle with a rest mass so small that the thermal background during
its creation at the Big Bang made it relativistic (e.g., neutrinos).
For it to be invisible on a galactic scale it must have no
electromagnetic, Strong Force, or Weak Force interactions.

You've practically just described right-handed neutrinos, which have
exactly these properties, but doesn't require going outside the
Standard Model (or more precisely: the variant of it, in which
neutrinos are just ordinary Dirac spinors with a small positive mass,
instead of Weyl or Majorana spinors).