Re: Cosmic acceleration rediscovered

From: greywolf42 (mingstb_at_marssim-ss.com)
Date: 01/01/05 

Date: Sat, 01 Jan 2005 18:08:51 GMT

Greg Hennessy <greg.hennessy@tantalus.cox.net> wrote in message
news:cr1p65$4j8$1@tantalus.no-ip.org...
> In article <W8YAd.71709$Bw5.53988@news.flashnewsgroups.com>,
> greywolf42 <mingstb@marssim-ss.com> wrote:

{snip higher levels}

> > > The "diminution of brightness" is an observable.
> >
> > *Apparent* brightness is an observable. "Diminution" from an otherwise
> > expected value requires a theory for the expected value.
>
> Wrong. You compare the surface brightness seen behind a cluster

How do you see "behind" something? Your *theory* tells you it's from
behind, correct?

> with
> the surface brightenss elsewhere. The fraction of the sky behind a
> cluster is quite small. The change in the surface brightness is *NOT*
> related to the value of the Hubble parameter. If you think so you show
> you do not understand the S-Z effect.

Sigh. Look, *you* claim that the S-Z effect results in a diminution of
surface brightness. (I don't see it in S-Z's paper, but that's another
matter.) Many people (including S&Z in the paper you referenced)
claim that the S-Z effect is related to the Hubble parameter. Simple logic
implies because change in surface brightness is related to the S-Z effect,
and the S-Z effect is related to the Hubble parameter; that change in
surface brightness is related to the Hubble parameter.

{snip higher levels}

> > > You seem quite fond of claiming astronomical observations are noise.
> >
> > Only when we claim results in the region that is below the physical
> > resolution of our instruments (i.e. the CMBR). And the CMBR is not
> > necessarily an astronomical observation.
>
> Wether or not a particular observation is below the physical
> resolition of an instrument depends on the instrument. Many different
> instruments have looked for the S-Z effect, and found them.

Variations in the CMBR are typically found at less than the physical
resolutions of the instruments. Specifically, all instruments up to and
including COBE found no variations from pure thermal down to the physical
resolution of the instruments. Variations were all based on computer
modelling of the remaining noise.

Specifially, to what "many different instruments" are you referring?

> > > I don't know why you think corrections predicted by the theory are "ad
> > > hoc", but they are needed for accurate work, and do not indicate a
> > > flaw with the procedure.
> >
> > Well, these are 'corrections' needed to make the observations match
> > theory.

{An "invisible" snip by Greg}
=============
> > And the value for the optical depth and peculiar motion is not
> > determined by any independent method, but by how one can make
> > the results match theory. That's what makes them ad hoc.
> > Ad hoc does not mean unreasonable.
=============

> Those are the corrections *predicted* by the theory.

That's the problem. The "corrections" are not independent of the theory.

> If I use a radar to detect the distance to a plane, will you then
> object that the value of the distance I find is "ad hoc" because I've
> made my observation match theory?

Bad analogies usually indicate that one has realized one has lost the
argument. Of course, "invisible" snipping of selected parts of a sentence
guarantee it.

> > > Well, here we agree, the S-Z effect is not a result of circular
> > > reasoning.
> >
> > The idea isn't. The application is circular, however.
>
> There is not circularity in the application of the S-Z effect. You are
> incorrect when you claim the surface brightness decrement is related
> to the value of the Hubble parameter.

If the Hubble parameter is related to the S-Z effect, and the surface
brightness decrement is related to the S-Z effect, then they are related to
each other.

> > > Well, I don't know why you claim we "want" the scatterings in any
> > > particular place, but you only get the scatterings in hot regions
> > > because that is were the relativistic electrons are. You don't have
> > > relativistic electrons in cold regions.
> >
> > But you have non-relativistic electrons in cold regions. Which are
> > assumed (by the S-Z methodologies) to have no effect whatsoever.
> > In short, the S-Z theorists assume that the CMBR is affected solely
> > by hot electrons, but never by cold electrons .
>
> And your problem with that is?

Given by the rest of the sentence that you "invisibly" snipped:
=============
> > .... which make up the vast majority of electrons
> > encountered by CMBR photons (from BB and S-Z theory).
=============

Snipping the argument, and implying that it didn't exist, does not make it
go away.

> If I try to measure the velocities of
> moving cars by using a doppler radar, will you complain that the still
> cars won't cause a doppler shift?

Bad analogies usually indicate that one has realized one has lost the
argument. Of course, "invisible" snipping of selected parts of a sentence
guarantee it.

> We think we have photons moving from the remnants of the big bang. We
> think these photons sometimes move in areas with hot electrons,
> sometimes they move in areas with cold electrons. When the photons
> move through hot electrons, we think they are inverse compton
> scattered in a way to change their power spectrum. When the photons
> move through the areas with cold electrons, we don't think anything
> happens.
>
> You have a problem with that because????

Because you ignore the "forward" Compton scattering effect.

> > The original comment was an ironical laugh about big bangers on the
> > group trotting out an authority that had been recently shown to be
> > totally ignorant of the realities of astronomical observation.

{Another classic "invisible" snip by Greg.}
===============
> > Zel'dovich really
> > truly believed that stellar images on photographic plates were
> > mathematical points (at least in 1963). And that basic
> > misunderstanding was the foundation of his 'hand-wavy' style.
===============

> Well, if given the choice between Zeldovich and yourself as whom I
> consider totally ignorant of the realities of astronomical
> observation, I choose you.

But you have no basis for this choice, except perhaps worship of authority.
Zel'dovich's misunderstanding (at least in 1963) is in black and white.
Which is why you snipped the evidence.

> > > Tell me what you think is "hand-wavy" about it.
> >
> > AFAICT, the S-Z "effect" is a miniscule temperature shift (temperature
> > fluctuations of relic radiation) on the order of 10^-4 or -5. It is
> > this effect that S&Z spend all their time calculating. I only see one
> > mention in the S-Z paper of what might be what you call "decrements"
> > or diminution of brightness. This is a single sentence on page 5:
> >
> > "The value delta T over T mentioned above is the change of temperature
> > measured by an observer moving together with the plasma: an observer on
> > Earth also measures a change of intensity (fluctuation) due to the
> > Doppler effect which equals delta T over T = (u / c) cos theta, where u
> > is the velocity of the plasma and theta is the angle between the
> > velocity and the direction of the observer."
> >
> > The above sentence is a classic hand-wave.

{Now Greg's invisible snips reach the downright dishonest, in light of his
following comment:}
===================
> > Either that, or it's a
> > poorly-worded reference to an effect derived by Sakharov (i.e. not the
> > S-Z effect). I don't see any mention of intensity decrements in either
> > the abstract, introduction, discussion (where details of predictions for
> > delta T over T exist), or conclusion sections. Did I miss something?
===================

I take it by Greg's snip, that he can't provide any support for the claim of
intensity decrements; as part of the S-Z effect.

> Do you use "hand wave" to mean "arguments I don't understand"?

No, I mean arguments that have no supporting logic or calculations contained
within them.

> The sentence you quote simply says that in addition to the change in
> surface brightness

The problem is that there is no support given for the claim of change in
surface brightness. This does not mean that there *is* no such effect. It
simply means that the paper gives no support for the idea.

> changes from cosmological changes there is a
> brightness change from doppler shifts from the earths orbit around the
> sun. Given that Sunyaev and Zeldovich give the formula for such a
> tempature shift, I'm clueless as to why you call this handwaving.

Temperature shift is not intensity decrement.

> However, every time Sunyaev and Zeldovich talk about delta T over T
> that is the temperture decrement I am talking about.

???? Temperature is not intensity. You've never mentioned "temperature
decrement" before.

> Although even
> there the essence of the S-Z effect is that the inverse compton
> scattering alters the background spectrum by taking flux from the
> Rayleigh Jeans side and moving to the Wein side of the spectrum.

According to the S-Z paper, it is an apparent temperature increase in the
CMBR, that arises from collision with hot electrons. Though S-Z use the
term "fluctuation." And that would be an apparent temperature increase, not
decrement.

{snip higher levels}

> > > No, I don't mean that. If you understand the S-Z effect, you know it
> > > predicts a decrement in the background behind a cluster as compared to
> > > the background not behind a cluster.
> >
> > I understand that many people claim this as a "prediction" of the S-Z
> > effect. Again, how do you observationally determine whether you are
> > observing CMBR from "behind" a galaxy cluster, rather than from in
> > front? All we observe are angular locations on the celestial sphere.
>
> Well, if the photons that are attributed to the background are indeed
> local, then you won't see the S-Z effect.

True, but that's a theoretical argument.

> And obviously, the photons
> we are observed don't have tags on them saying "I was emitted umpty
> squat light years away".

That is my point.

> However, if you have two models,

We don't. We only have one under discussion. The S-Z effect.

> one that
> says the photons in the 3 degree background come from recombination at
> z 1000, and a second theory that says the photons from the 3 degree
> background come from local sources, and the first predicts a S-Z
> effect, and the second doesn't, and you observe a S-Z effect, then you
> conclude that the photons are being emitted from behind the cluters.

But *real* observations do not depend upon even one theory. Let alone
requiring two theories (one you are claiming to test, and another chosen
solely as a throw-away strawman).

> > > > > A decrement in the surface brightness is observed.
> > > >
> > > > And the value of this "decrement" is what? Please provide numbers,
> > > > statistical significance, and citation. I think you'll find that it
> > > > merely noise processing.
> > >
> > > A pretty good listing is located at
> > > http://nedwww.ipac.caltech.edu/level5/Birkinshaw/Birk9_1.html.
> >
> > I get an error that http://nedwww.ipac.caltech.edu/ and all permutations
> > cannot be found. Are you sure this is the link you wanted?
>
> That url works fine for me, both at work and at home. It is indeed the
> link I want.

OK, it works now. Seems to have been a temporary glitch.

Looking at Table 4, we see that the error bars on all the measurements are
substantial fractions (and often many times the value of) the claimed
"measured" value. Which clearly demonstrates my point about noise
processing.

> > I was pointing out the references, above, that the S-Z effect was not
> > matching BB theory. Current papers are fully circular, as I have
> > pointed out.
>
> The second reference you posted wasn't about the S-Z effect, and so is
> irrelevent. The first link
> (http://groups-beta.google.com/group/sci.astro/msg/454452a1cfe33c0a)
> claims that the value of Ho obtained (64 +- 8) is "too low". Given
> that the WMAP value of Ho (the best we have) is that Ho is 72, please
> explain to me why 64 +- 8 doesn't match 72.

But WMAP does not measure H_0. WMAP *assumes* H_0. (More noise
processing.)

And the reason that I said that the above link contradicts the BB, is
because the paper claimed that it did. 

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

Relevant Pages

  • Re: Cosmic acceleration rediscovered
    ... You compare the surface brightness seen behind a cluster ... > claim that the S-Z effect is related to the Hubble parameter. ... >> sometimes they move in areas with cold electrons. ...
    (sci.astro)
  • Re: Cosmic acceleration rediscovered
    ... The change in the surface brightness is *NOT* ... instruments have looked for the S-Z effect, ... >> because that is were the relativistic electrons are. ... We think we have photons moving from the remnants of the big bang. ...
    (sci.astro)