Re: Galaxies without dark matter halos?

In article <[EMAIL PROTECTED]>, greywolf42
<[EMAIL PROTECTED]> writes: 

> >> "Dark Energy" may not be observed.  The observation is that the Hubble
> >> constant is not linear at far distances.  "Dark Energy" is the ad hoc
> >> rationale to account for the observation (the new epicycle).
> >
> > The point is that the non-linearity is NOT completely arbitrary, but is
> > easily explained by an idea which has been around for decades.
> 
> 'Dark energy' has not been around for decades.  It was not even floated
> until the observations of supernovae disproved the linear Hubble assumption.

First mistake: there never was a "linear Hubble assumption".  Go back 
and read cosmology papers from the 1920s and 1930s.  The relation 
between apparent magnitude (of "standard candles") and redshift is 
linear at small redshifts only.  ("To first order, the relationship is 
linear".  Duh.  No big deal.)  Admittedly, there is some confusion 
since there is an EXACT linear relation---at all redshifts---between 
velocity and distance, but both the velocity and the distance involved 
are not observable quantities.  However, since you mention the 
observations of supernovae, I assume you are referring to the relation 
between the observables apparent magnitude and redshift.  To clear up 
any remaining confusion:

@ARTICLE      {EHarrison93a,
               AUTHOR       = "Edward R. Harrison",
               TITLE        = "The Redshift-Distance and Velocity-Distance
                               Laws",
               JOURNAL      = APJ,
               YEAR         = "1993",
                 VOLUME       = "403",
                 NUMBER       = "1",
                 PAGES        = "28",
                 MONTH        = jan,}

Second mistake: "dark energy" is simply the cosmological constant, by 
any other name.  (I don't like the name, simply because it confuses 
things.)  Some people see "dark energy" to be more general: different 
equation of state, time-dependent.  But there have been speculations 
about time-dependent cosmological "constants" for a long time as well.  
(Unlike the Hubble constant, where "constant" means "constant everywhere 
in space at a given cosmic time", the cosmological constant has more the 
meaning of "constant of integration".  The capital-Lambda (i.e. not 
normalised with the Hubble constant) is, in the simplest theories, 
indeed constant with time.)

You make it sound like people were surprised by the non-linearity of the 
Hubble diagram for SN Ia!  Far from it!  What was surprising was a) the 
technical achievement of gathering the observations and b) the 
confirmation by an independent group.

> The m-z diagram for supernovae could as easily be explained by the modified
> QM theory of JP Vigier.  Which really *has* been around for decades.  The
> m-z curve is in fact a curve of the type predicted by Vigier's theory.  

Quantitative reference please.

> >>No need to distort my position with a strawman argument.  I simply note
> that
> >>the "amount" and 'characteristics' of "dark energy" are backfit to the
> >>observed m-z diagram.

If I read off a number from a scale, is my weight "just" a back-fit?

> >> Equations of state are theoretical constructs.  The observation is
> >> simply that the "Hubble constant," isn't constant.
> >
> > You are displaying extreme lack of knowledge here.  The term "constant"
> > in "Hubble constant" means that, at a given time, it is constant
> > everywhere in the universe.
> 
> The Hubble constant was defined in the 1920's to mean the relation between
> the distance of a galaxy (containing a resolvable Cepheid variable) and the
> redshift of the light from the galaxy.  There is -- and was -- no additional
> theoretical baggage about being constant 'at a given time'.

Wrong.  Even Hubble (who didn't call it the "Hubble constant") noted 
that he might be observing "the de Sitter effect", i.e. something which 
had been predicted theoretically earlier---and of course it was clear 
that this is a linear approximation at low redshifts.  Read papers by 
Sandage from the 40's and 50's where cosmology is described as a "search 
for two numbers", namely H and q.  The deceleration parameter q IS the 
deviation from the linear relation (i.e. the second-order parameter).