Galactic pancake mystery solved

http://news.bbc.co.uk/2/hi/science/nature/4422555.stm

Shneor

Yes, there's nothing like using a naive, first-order model in a computer
simulation to to validate another unexplained and unobservable phenomenon.

Modern cosmology (in the guise of science) marches on -- LOL!


shneor wrote:
http://news.bbc.co.uk/2/hi/science/nature/4422555.stm

Shneor

On Thu, 07 Apr 2005 17:02:33 -0600, Tim Killian
wrote:

Yes, there's nothing like using a naive, first-order model in a computer
simulation to to validate another unexplained and unobservable phenomenon.

The article doesn't describe any details of the simulation, but
apparently you are familiar with it. Perhaps you could share your
knowledge- I would be very interested in the simulation technique, even
if it is "naive" and "first-order". Presumably you were at the talk,
since the work hasn't been published yet.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Tim Killian wrote in
:

Yes, there's nothing like using a naive, first-order model in a
computer simulation to to validate another unexplained and
unobservable phenomenon.


1. How do you know the that the model they used was naive?

2. The phenomenon they were attempting to model was certainly observed.
Otherwise why would they be attempting to explain it.

Modern cosmology (in the guise of science) marches on -- LOL!


What do you suggest they do? Give up and say this stuff can never be
understood?

Klazmon.





shneor wrote:
http://news.bbc.co.uk/2/hi/science/nature/4422555.stm

Shneor

"Chris L Peterson" wrote in message
...
On Thu, 07 Apr 2005 17:02:33 -0600, Tim Killian

wrote:

Yes, there's nothing like using a naive, first-order model in a
computer
simulation to to validate another unexplained and unobservable
phenomenon.

The article doesn't describe any details of the simulation, but
apparently you are familiar with it. Perhaps you could share your
knowledge- I would be very interested in the simulation technique,
even
if it is "naive" and "first-order". Presumably you were at the talk,
since the work hasn't been published yet.

The paper can be found on arXiv.org
http://arxiv.org/abs/astro-ph/0503400

Llanzlan Klazmon wrote:
1. How do you know the that the model they used was naive?

From reading the rest of his posts, it seems that he considers all (or
most) of cosmology to be naive and first-order. So it naturally stands
to reason that this simulation should also be naive and first order.

Of course, before any science can progress to second order and less
naive, it must generally pass through a naive and first order phase.
So I applaud the efforts of the researchers in question. I would agree
that the pancake mystery has not been *solved* exactly, but that is the
wording of the reporter, I think, and in any event, the distribution
appears to be less mysterious and troubling than it was at first.

It's been my experience that science as reported in the mainstream
press sounds much more certain and definitive than what is actually
published in the underlying journals. Of course, there are researchers
who perhaps simplify too much in interviews; that might contribute to
that disparity.

What do you suggest they do? Give up and say this stuff can never be
understood?

Since it entertains Tim to no end to heckle the efforts of researchers
in cosmology, I should think he would want them to continue. I for one
wouldn't want him to be disappointed.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

On Fri, 8 Apr 2005 00:54:02 +0100, "OG"
wrote:

The paper can be found on arXiv.org
http://arxiv.org/abs/astro-ph/0503400

Thanks- all I had found was the abstract.

Interesting stuff. One thing for sure, this is far from a "first-order
model". The list of physical processes included is impressive. As far as
"naive"... well, I guess that's a value judgment. It seems pretty well
thought out to me, and whenever a simulation matches an observation you
have to at least take it seriously. But I don't think Tim takes any
cosmological theories seriously.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Llanzlan Klazmon wrote:

Tim Killian wrote in
:


Yes, there's nothing like using a naive, first-order model in a
computer simulation to to validate another unexplained and
unobservable phenomenon.



1. How do you know the that the model they used was naive?


Because it's the first instance for use of the high-res N body model in
this application. The authors admit that they assumed a distribution for
the dark matter "halo", even though no such distribution has ever been
measured! Yes, I'd call that naive.


2. The phenomenon they were attempting to model was certainly observed.
Otherwise why would they be attempting to explain it.


Yes, they know where the 11 satellite galaxies are located -- wow. I was
referring to their "cold, dark matter" blather.



Modern cosmology (in the guise of science) marches on -- LOL!



What do you suggest they do? Give up and say this stuff can never be
understood?



No, but building your castle on a foundation of sand is never a good
idea. Science should be about observation, repeatable experiments and
fact, not video-game computer models, wishful thinking, or arm-waving
explanations using untenable assumptions.

Tim Killian wrote in
:



Llanzlan Klazmon wrote:

Tim Killian wrote in
:


Yes, there's nothing like using a naive, first-order model in a
computer simulation to to validate another unexplained and
unobservable phenomenon.



1. How do you know the that the model they used was naive?


Because it's the first instance for use of the high-res N body model
in this application. The authors admit that they assumed a
distribution for the dark matter "halo", even though no such
distribution has ever been measured! Yes, I'd call that naive.

I would call it the best avialable model at this stage. You should write
and tell them your concerns along with your suggested improvements.



2. The phenomenon they were attempting to model was certainly
observed. Otherwise why would they be attempting to explain it.


Yes, they know where the 11 satellite galaxies are located -- wow. I
was referring to their "cold, dark matter" blather.



I don't see a problem with that myself, as a working hypothesis to
explain the rotation curves of galaxies. If the hypothesis is wrong
these types of simulations can help to falsify it no?



Modern cosmology (in the guise of science) marches on -- LOL!



What do you suggest they do? Give up and say this stuff can never be
understood?



No, but building your castle on a foundation of sand is never a good
idea. Science should be about observation, repeatable experiments and
fact, not video-game computer models, wishful thinking, or arm-waving
explanations using untenable assumptions.


Well the obvious counter example to this argument is the neutrino. It
was required to balance the books in certain nuclear reactions. The dark
matter hypothesis is comparable. Sure it could be wrong but you have to
start from somewhere. Your comments about video game computer models are
absurd. Try telling Boeing they aren't allowed to use computer
simulations in their aircraft design program.

Klazmon.

I have nothing against theoretical physicists who ply their trade and
work every day to expand our understanding. And there have been numerous
triumphs in the past century where mathematical models were key
contributors to legitimate advances in science. Behind every one of
these models was an extraordinary intellect, not just a fast computer.

That said, I'm bothered by the increasing use of computer of simulations
that are visually appealing (I liken them to video games), but lack any
depth in their underlying structure. I recently did some work at a small
university wind tunnel and had a chance to talk to its director. Even
though it was a modern, well instrumented facility, he was concerned
that the tunnel would eventually be closed because students and most
faculty preferred simulations and computer models to the relative
drudgery associated with actual physical measurements. There is no doubt
that the computer modeling is less expensive than making physical
measurements, but are the students learning as much? Do they have a true
understanding of the code running on the super computer, or are they
simply awed by the machine? When they go out in the world are they going
to have the depth of understanding to make meaningful contributions?




Llanzlan Klazmon wrote:
Tim Killian wrote in
No, but building your castle on a foundation of sand is never a good
idea. Science should be about observation, repeatable experiments and
fact, not video-game computer models, wishful thinking, or arm-waving
explanations using untenable assumptions.



Well the obvious counter example to this argument is the neutrino. It
was required to balance the books in certain nuclear reactions. The dark
matter hypothesis is comparable. Sure it could be wrong but you have to
start from somewhere. Your comments about video game computer models are
absurd. Try telling Boeing they aren't allowed to use computer
simulations in their aircraft design program.

Klazmon.