On Mon, 15 Sep 2003, greywolf42 wrote:
You are incorrect. There are about a couple of dozen galaxies where
we have the ability to resolve Cepheid variables -- which are our only
reliable distance "standard candles" (pre-supernovae -- which is another
bag of worms). All distances to other galaxies are measured by assuming
the BB and Hubble constant.

-This- -is- -just- -flat- -wrong-.

Measurements to 'all'' other galaxies are -not- made using the Hubble
constant. Several other methods are used. One of the more common types
involves measuring rotation curves for local galaxies with cepheid &
RR-lyre distances, say by measureing the width of the 21cm line and
obtaining a relationship with luminousity (Large galaxies tend to have
more stars - they're brighter + they're heavier so things tend to orbit
faster. And yes, they do pay attention to the type of galaxy.).
This relationship is compared with that of a distant galaxy to get an
estimate of the absolute luniousity which is compared with the appearant
luninousity to get a distane. (See Tully-Fischer, Faber-Jackson,
cosmological distance ladder).
It is sooooooo easy to find out about these other measurements that to
not know about them borders on willfull. I mean, box 14.2 in shu*:

Local distance indicators
Classical Cepheids
Novae
RR Lyae
W Virginis
Intermediate distance indicators
Brightest nonvariable stars of a galaxy
Brightness of globular clusters
Diameters of giant HII complexes
Global distance indicaters
Fischer-Tully relation
Brightness of Sc I galaxies
Supernovae
Three brightest galaxies of a cluseter
Diameters of bright galaxies
Baldwin relation for QSOs

The list is dated but it does seem to indicate that other methods
are used. Support your ideas, ok, but don't shovel up a load of
dingo's kidneys.

3ch

*Frank Shu _The Physical Universe_. A nice intro book & reference.