In article ,
(Eric Flesch) writes:
I've never yet seen calculations done onto evolving spatial curvature.

Doesn't the Friedman equation say how curvature evolves?

Nowadays only static flat is used, particularly since the measurements
. show a
flat universe.

As you say, the observations seem clear, and nobody today thinks our
Universe has much curvature. There were, however, plenty of papers
on that subject in the past, and modern observers still look for
whatever residual curvature there might be.

But if we see a flat universe, there can really only be two
possibilities: (1) it is flat, or (2) it isn't flat but looks like
it is.

You need to relate "looks like" to specific observations. It's not
as though no one has thought of curvature before.

SW Which distance did you have in mind?

For example, at z=1, c would be twice the value.

Redshift z represents the scale factor, not a distance. You need a
cosmological model to translate scale factor to distance and lookback
time, and there are at least three different distances relevant to
cosmology.

Are you suggesting that a local measurement of c at z=1 would return
a value twice as large as measured at z=0? I'm pretty sure that's
ruled out by observations.

SW Isn't [changing c] ruled out by observations?

No because we've observed only here in this local place.

??? There are plenty of redshifts for high-z objects, and optical and
radio redshifts agree with each other. Moreover, CO redshifts agree
with H I redshifts, both measured with radio techniques. That
wouldn't be the case if c were varying because the 21 cm line is a
hyperfine splitting that has a different dependence on c than
ordinary lines.

No, the frequency is invariant but the wavelengths compress with the
slowing light -- so it looks the same as if both here & there were
flat. My model may be wrong but not for that reason.

Optical (grating) spectrographs measure wavelength. If there were a
change, why wouldn't that be measured?

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA