Re: Cosmic acceleration rediscovered
From: greywolf42 (mingstb_at_marssim-ss.com)
Date: 12/28/04
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Date: Tue, 28 Dec 2004 01:32:21 GMT
George Dishman <george@briar.demon.co.uk> wrote in message
news:cqgl0m$u9d$1@news.freedom2surf.net...
>
> "greywolf42" <mingstb@marssim-ss.com> wrote in message
> news:s7Iyd.419$Bw5.333@news.flashnewsgroups.com...
> > George Dishman <george@briar.demon.co.uk> wrote in message
> > news:cqabiq$9pu$1@news.freedom2surf.net...
> <snip>
> >> H_0 has the empirical value 71km/s per MPc which
> >> means dE/E is about 0.024% per MPc hence R is
> >> about 4.2GPc.
> >
> > Ah! Now I see where you are going. I think you are approaching this a
> > bit sideways, but we should be able use this approach.
> >
> > However, my objection above to your use of H_0, was because H_0 is a
> > theoretical value of the BB theory, not an empirical relation.
>
> The value isn't theoretical at all, in the sense
> that it could not be predicted from theory alone.
But it isn't observable, either. H_0 contains "velocities". The observable
is redshift.
The empirical version would have units of delta lambda over lambda per MPc.
> > (What is
> > actually measured is *redshift* versus distance -- not speed per
> > distance.)
>
> Exactly. Having made the measurement of redshift
> versus distance, in a model that explains the
> redshift by expansion or motion,
We don't use models to make measurements.
> the measurements
> can most meaningfully be expressed as speed per
> distance while in a tired light interpretation
> the same information makes more sense in the form
> of a characteristic distance, or mu if you like,
> but it is easy to switch between those units.
> That's why I said the values were "related".
The measurements can most meaningfully be expressed as just the way they
were measured.
> > But since you are then working with dE/E, we don't need to worry about
> > the difference, here.
> <snip>
> >> And every photon loses about 63% of its energy
> >> every 4.2GPc, true?
> >
> > The current value of the slope of H_0 includes some specific BB
> > assumptions.
>
> The best current value uses the angular power
> spectrum measured by WMAP and that method I agree
> is likely only to be applicable in a BB model.
> However, the older technique of measurements of
> nearby source for which distances can be found
> from the distance ladder using parallax, Cepeids
> and so on is equally valid for determining the
> constant in tired light models. The difference
> is that the uncertainty will be higher.
The uncertainty in the observation of redshift vs. distance is unchanged.
Regardless of how the WMAP theoreticians tweak their computer models.
> > However, for the purposes of this exercise, I will accept your values
> > are in the ballpark (roughly a factor of 2, if I converted correctly).
>
> That's another test you can apply to a tired light
> model. A factor of 2 is probably about as much as
> the uncertainty would allow but it would be hard
> to say without looking at the detail of the
> determination so I'm happy to accept that for the
> moment.
The point is, that tired light theoreticians usually don't require that
*ALL* the redshift be due to tired light. We try to avoid the trap that
caught the big bangers.
I.O.W., the redshift-distance relation may include contributions from
different effects (at least in theory). Which could shift the onset of the
nonlinear deviation. (For example, a combined Vigier-tired-light and
plasma-"fireworks"-expanding-galaxies model.)
> > Sidenote: LeSagians and tired light types usually use the variable mu;
> > which may be calculated from material/aether properties (EM and
> > gravitational). We typically don't use the resulting characteristic
> > distance, R (which is back-calculated, or ad hoc). R and mu are
> > inversely related.
>
> Your last two sentences appear to be in conflict.
> If mu can be derived from the theory, then just
> tkae the uinverse
Tired light theories do not deal with universes. That's the big bang.
> and you have a theoretical value
> for R. That can then be compared to the observed
> value described above as a test of the theory.
> Neither value is ad hoc.
The ad hoc referred to the use of tired light theory *solely* to explain the
redshift (the way the big bang started). Values -- per se -- are never ad
hoc. It is how they are used that obtains the ad hoc description.
{brought over from parallel thread}
> >> Agreed, and since the value is now being measured
> >> by observation, it clearly meets your criterion.
> >
> > The point is, that neither the shape, nor value was predicted by the BB.
> > It is another ad hoc fit to the BB. The shape of the curve *was*
> > predicted by *all* tired light theories. The value was predicted
> > by some.
>
> Ok, you have been reading the posts between Bjoern and
> me so can you clarify that.
Yes, I've amused myself watching you and Bjoern pat each other on the back.
> You have said the exponential
> form fits the measurements, but in most tired light
> theories the energy is exponential with distance while
> what is observed is redshift versus magnitude or some
> other indirect measure of distance.
You are correct that what is observed is redshift versus some indirect
measure of distance (since we can't do parallax that far). Since energy is
exponential with distance in tired light theories, so is redshift.
> Precisely which
> relationship between _measured_ values is predicted by
> tired light theories?
The relationship between redshift and actual distance will be exponential.
That is, at the low-redshift (low z) distances, you will have an apparently
linear relation that is equal to the first part of the exponential series
expansion. This relation will begin to deviate from linear as higher-order
terms become important at longer distance. The entire curve will be
exponential.
Using your data, above, dE/E is about 0.024% per MPc. And every photon
loses about 63% of its energy every 4.2GPc.
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}
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