In article ,
Phillip Helbig---undress to reply writes:
The question is whether, within the observational errors, one can show
that 1/z is a better fit than, say, the current standard cosmological
model.

Exactly so. Substantial data sets of supernova distance moduli are
published, so at least a first test shouldn't be hard. The DMs are
luminosity distances, so one has to use some theory to convert to
whatever distance 1/z is supposed to represent.

Measuring angular size is easy.

In principle, at least. Not always so in practice.

The hard part is determining
what physical size it corresponds to. This classical test has, due to
observational (not theoretical) difficulties not produced anything
useful up until now. (In some sense, CMB measurements are an
angular-size test, though.)

Why only "in some sense?" I thought they were exactly an angular
size test. Also baryon acoustic oscillations (BAO). So far, both
are consistent with standard cosmology. Aren't CMB fluctuations one
of the reasons the standard cosmology is standard?

In the standard cosmology, angular size distance _decreases_ as
redshift increases beyond a certain value (around z=1.9 or so). If
1/z is the angular size distance, I wouldn't expect it to come
anywhere close to fitting beyond that even if it fits OK at smaller
redshifts. But there's no substitute for comparison with data.

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