Another one taken from an old-time email to a MD friend who is highly interested in physics and astro as well..
-M
Greg-
On Tue, 10 Apr 2007, Greg R. wrote:
> Mandeep,
>
> So you study "weak gravitational lensing?" You must be
> familiar with the recent publications on the
> time-evolving distribution of the dark matter scaffold
> allegedly from "homogeneous" to "clumpy" consistencies
Yep, some of the folks i worked with at Caltech are partly responsible for
some of those images, indeed,
> ... although the images I have seen are not quite as
> cut & dried, but perhaps it is true--I suspect it
> is--which may be more clear should they get data
> closer to the beginning of our Universe rather than
> just halfway back (I am sure that is easier said than
> done).
Yes, we are slowly getting there though, we can see some of the brightest
galaxies all the way back to about 1 billion years post-Big Bang now, and JWST
-- the successor to the Hubble Telescope, with about 10 times the
collecting area or so -- will go even further, and see many more back
then, when it's launched in 7 or so years (currently it's planned for
launch in 2013, and parts of it are being steadily built, the mirrors
ground, etc.). [Hah -M in 2014]
> I was intrigued with the MOND theory as a description
> of the dark matter effect, but that idea has taken an
> observational hit recently and I have not heard much
> of a rebuttal.
Well, those MOND (Modified Newtonian Dynamics) guys are always writing
papers, trying to make their models work (and yes, the Bullet
Cluster observations of DM separated from galaxy cluster gas seen last
year, which is what you're referring to, is a hard one for them).
But DM is much the preferred explanation for most cosmologists. But - at some level, it
ain't really really there until you see it. That is, until we actually
detect DM directly in detectors on Earth, it's gonna be hard to fully
"believe" in it. That's how it goes.
People have been trying hard to find it for a long, long time, with many
different types of detectors, but the cross section with normal matter may
be so low - or nonexistent - that it's never seeable. We don't know yet.
LHC *may* see it in decays of heavy particles that require momentum
balancing (the same way that neutrinos were first theorized in 1932 by
Pauli). at LHC we have about 2-3 years before we'll know for pretty sure
if it's easily visible there. or we'll see whatever else is out there.
we have about 5-10 more to be totally sure whether it sees something new..
or not. So it's a darn exciting time for particle physicists [i'd still say that now, in 2014.. maybe just a bit less emphatically, now].
The tension in the air is *palpable*, let me tell you.
-M
-M
Greg-
On Tue, 10 Apr 2007, Greg R. wrote:
> Mandeep,
>
> So you study "weak gravitational lensing?" You must be
> familiar with the recent publications on the
> time-evolving distribution of the dark matter scaffold
> allegedly from "homogeneous" to "clumpy" consistencies
Yep, some of the folks i worked with at Caltech are partly responsible for
some of those images, indeed,
> ... although the images I have seen are not quite as
> cut & dried, but perhaps it is true--I suspect it
> is--which may be more clear should they get data
> closer to the beginning of our Universe rather than
> just halfway back (I am sure that is easier said than
> done).
Yes, we are slowly getting there though, we can see some of the brightest
galaxies all the way back to about 1 billion years post-Big Bang now, and JWST
-- the successor to the Hubble Telescope, with about 10 times the
collecting area or so -- will go even further, and see many more back
then, when it's launched in 7 or so years (currently it's planned for
launch in 2013, and parts of it are being steadily built, the mirrors
ground, etc.). [Hah -M in 2014]
> I was intrigued with the MOND theory as a description
> of the dark matter effect, but that idea has taken an
> observational hit recently and I have not heard much
> of a rebuttal.
Well, those MOND (Modified Newtonian Dynamics) guys are always writing
papers, trying to make their models work (and yes, the Bullet
Cluster observations of DM separated from galaxy cluster gas seen last
year, which is what you're referring to, is a hard one for them).
But DM is much the preferred explanation for most cosmologists. But - at some level, it
ain't really really there until you see it. That is, until we actually
detect DM directly in detectors on Earth, it's gonna be hard to fully
"believe" in it. That's how it goes.
People have been trying hard to find it for a long, long time, with many
different types of detectors, but the cross section with normal matter may
be so low - or nonexistent - that it's never seeable. We don't know yet.
LHC *may* see it in decays of heavy particles that require momentum
balancing (the same way that neutrinos were first theorized in 1932 by
Pauli). at LHC we have about 2-3 years before we'll know for pretty sure
if it's easily visible there. or we'll see whatever else is out there.
we have about 5-10 more to be totally sure whether it sees something new..
or not. So it's a darn exciting time for particle physicists [i'd still say that now, in 2014.. maybe just a bit less emphatically, now].
The tension in the air is *palpable*, let me tell you.
-M
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