Cosmological Simulations: Illustris Or Illusion?

On Thursday, May 29, 2014 2:48:24 AM UTC-4, Phillip Helbig---undress to reply wrote:

YOU say it is untestable, ignoring claims that it is. Please rebut

them.

See Peter Woit's many discussions (and additional commentary) on the multiverse, anthropic reasoning and related pseudo-science at Not Even Wrong.

Also read Jim Baggott's new book Farewell To Reality.

In article , "Robert L.
Oldershaw" writes:

On Thursday, May 29, 2014 2:48:24 AM UTC-4, Phillip Helbig---undress to reply wrote:

YOU say it is untestable, ignoring claims that it is. Please rebut

them.

See Peter Woit's many discussions (and additional commentary) on the multiverse, anthropic reasoning and related pseudo-science at Not Even Wrong.

Also read Jim Baggott's new book Farewell To Reality.

How about some references to active scientists, i.e. those who publish
papers?

On Friday, May 30, 2014 3:11:27 AM UTC-4, Phillip Helbig---undress to reply wrote:

How about some references to active scientists, i.e. those who publish

papers?

If you look at postings at arXiv.org you will find many papers that
buy into the prevailing paradigms. No surprise there.

However there are also well-published professional physicists who have
attacked various weaknesses of the prevailing paradigms. In the past
Feynman and Glashow come to mind. More recently Steinhardt, Kroupa,
Loeb, Smolin, etc. come immediately to mind. I think if I wasted a few
hours researching this issue I could come up with many more examples
of professional physicists who think the prevailing paradigm and
current pseudo-scientific trends are problematic.

However, I suspect that you would only say that these people are
'wrong-thinkers' and crackpots, so I will not spend more time on this
debating dodge of yours.

[Mod. note: attributing opinions to people without waiting to hear
what they will say is also a 'debating dodge'. Let's have fewer of
them and more substance, please. In particular, if there are no
concrete points to discuss directly related to research in
astrophysics, this part of the thread should end here. -- mjh]

In article , "Robert L.
Oldershaw" writes:

However there are also well-published professional physicists who have
attacked various weaknesses of the prevailing paradigms. In the past
Feynman and Glashow come to mind. More recently Steinhardt, Kroupa,
Loeb, Smolin, etc. come immediately to mind.

Various weaknesses, yes, but their claims are not your claims. Of
course, the enemy of one's enemy is one's friend, but that's usually not
a stable long-term strategy. One also has to distinguish debates about
details from debates about the foundations. I don't think any of those
you mention above think that they are ignored by the community, that a
new paradigm is on the rise etc. I remember reading Halton Arp's book
where he DOES claim that he has been ignored by the community, deemed a
crackpot etc. Then I got to the back flap, where it says he "is on the
staff of the Max Planck Institute for Astrophysics". With criticism
like this, who needs support? (Actually, he is a guest of the institute
(I believe due to the initiative of Simon White, one of the directors),
and not really on the staff, but still.)

[Mod. note: 'Was': he died late last year -- mjh]

On Saturday, May 31, 2014 8:28:57 AM UTC-4, Phillip Helbig---undress to reply wrote:
Various weaknesses, yes, but their claims are not your claims. Of
course, the enemy of one's enemy is one's friend, but that's usually not
a stable long-term strategy. One also has to distinguish debates about
details from debates about the foundations. I don't think any of those
you mention above think that they are ignored by the community, that a
new paradigm is on the rise etc. I remember reading Halton Arp's book
where he DOES claim that he has been ignored by the community, deemed a

You seem to arguing with a straw man version of my explicit and
limited themes in this thread and related threads of recent weeks.

This thread is about the Illustris simulation and what simulations can
and cannot do for scientific understanding. We seem to have drifted
way off topic.

[Mod. note: thread drift is normal and acceptable, as long as it
doesn't go too far from 'research in astrophysics'. Participants
should focus on writing interesting posts about research in
astrophysics and leave moderation to, well, the moderator -- mjh]

On Tuesday, May 20, 2014 2:32:54 AM UTC-4, Robert L. Oldershaw wrote:

Given a large number of dedicated workers and over
50 years of tinkering with a very complicated set
of models involving numerous adjustable parameters
and theoretical add-ons, is it surprising that the
set of models can be used to reproduce observations
fairly well? Hardly!

There is a vast difference between having adjustable parameters, and
being infinitely adjustable. If I have a quadratic polynomial with
adjustable coefficients, I still will not be able to fit most
arbitrary curves.

More concretely, if I have a model simulation of a universe with only
hot dark matter, then I will not be able to create anything that
resembles the observed void structure, no matter how many parameters I
adjust. And even more concretely, if my simulation contains only
baryonic dark matter, then I will not be able to simulate the void
structure of the universe. The large scale structure of the universe
is one of many pieces of evidence that most of the mass of the
universe does not consist of baryons.


--Wayne

On 6/1/2014 8:03 AM, Robert L. Oldershaw wrote:
...
... way off topic.

[Mod. note: thread drift is normal and acceptable,

It's even fundamentally unavoidable: everything can be
related to a certain subject, given a line of reasoning.
One might perhaps define a kind of "distance" between
concepts and impose a limitation on it, but would it be
appropriate for an astronomy group to be scared of
distances?!

--
Jos