Red-shift of distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

It seems that most discussion of red-shift centres around the
assumption that SR recession is the cause (and hence that the universe
is expanding).

Why has GR time dilation been eliminated as a cause?

So, why should most objects exhibit a red-shift, rather than a neutral
average shift? My best answer is that we, on earth, are at the edge of
our galaxy (the milky way), and hence quite far from the concentration
of mass near the centre of our galaxy.

On the other hand, most matter (stars) in the universe are close to
the centre of their galaxies, so, on average, most objects should
exhibit a red-shift to us on earth.

A corollary of this is that stars near the centre of our own galaxy
(the milky way) should also exhibit red-shift to us (even though they
are clearly not moving away from us on average). This should be
testable, although I'm not sure how one would identify a bright object
as a star in the center of our galaxy, rather than a distant object
shining through (brightness?).

Hubble, Edwin, "A Relation between Distance and Radial Velocity among
Extra-Galactic Nebulae" (1929) Proceedings of the National Academy of
Sciences of the United States of America, Volume 15, Issue 3, pp.
168-173

Note that Hubble (and presumably all that follow) use _luminosity_ as
a measure of _distance_. However, luminosity is actually also a
measure of GR time dilation, independent of distance, as described
above.

Just some ideas.
Flame away

Roland

On Jun 24, 4:01 am, Roland PJ wrote:
Red-shift of distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

It seems that most discussion of red-shift centres around the
assumption that SR recession is the cause (and hence that the universe
is expanding).

Why has GR time dilation been eliminated as a cause?

The purpose of this paper is twofold - to demonstrate that
in the gravitational redshift it is the frequency [of] a photon that
is
constant, and to describe the mechanism responsible for the
change of its wavelength.
http://aps.arxiv.org/abs/gr-qc/9810030v14

See also papers by L.B Okun

Sue...



So, why should most objects exhibit a red-shift, rather than a neutral
average shift? My best answer is that we, on earth, are at the edge of
our galaxy (the milky way), and hence quite far from the concentration
of mass near the centre of our galaxy.

On the other hand, most matter (stars) in the universe are close to
the centre of their galaxies, so, on average, most objects should
exhibit a red-shift to us on earth.

A corollary of this is that stars near the centre of our own galaxy
(the milky way) should also exhibit red-shift to us (even though they
are clearly not moving away from us on average). This should be
testable, although I'm not sure how one would identify a bright object
as a star in the center of our galaxy, rather than a distant object
shining through (brightness?).

Hubble, Edwin, "A Relation between Distance and Radial Velocity among
Extra-Galactic Nebulae" (1929) Proceedings of the National Academy of
Sciences of the United States of America, Volume 15, Issue 3, pp.
168-173

Note that Hubble (and presumably all that follow) use _luminosity_ as
a measure of _distance_. However, luminosity is actually also a
measure of GR time dilation, independent of distance, as described
above.

Just some ideas.
Flame away

Roland

On Jun 24, 4:57 am, "Sue..." wrote:

http://aps.arxiv.org/abs/gr-qc/9810030v14

See also papers by L.B Okun
http://arxiv.org/abs/physics/9907017

Sue...

On Jun 24, 12:01 am, Roland PJ wrote:

Red-shift of distant objects could be due to ...
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

How does your theory explains the fact that the red-shift is larger
for galaxies that are farther away? Should you assume that far
galaxies are more massive?


Eugene.

"Roland PJ" wrote in message oups.com...
Red-shift of distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

It seems that most discussion of red-shift centres around the
assumption that SR recession is the cause (and hence that the universe
is expanding).

Why has GR time dilation been eliminated as a cause?

It has not been eliminated it is a contributing factor.
See:

http://en.wikipedia.org/wiki/Gravitational_redshift
http://physics.ucr.edu/~wudka/Physic...ww/node99.html

--
Martin Hogbin

On Jun 24, 5:39 am, "Martin Hogbin"
wrote:
"Roland PJ" wrote in ooglegroups.com...
Red-shift of distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

It seems that most discussion of red-shift centres around the
assumption that SR recession is the cause (and hence that the universe
is expanding).

Why has GR time dilation been eliminated as a cause?

It has not been eliminated it is a contributing factor.
See:

http://en.wikipedia.org/wiki/Gravitational_redshift

As light leaves the vicinity of this object it is shifted
towards the red: for a sufficiently compact and massive
object a blue laser on the surface will be seen as red in outer
space.
http://physics.ucr.edu/~wudka/Physic...ww/node99.html


Quite the opposite of the GPS presets and
violatiing causality in the opposite direction.

That must be an "authoritative text".
On the other hand the phenomenon is alternatively
discussed (even in some authoritative texts) in terms of
an energy loss of a photon as it overcomes the gravitational
attraction of the massive body.
http://arxiv.org/abs/physics/9907017

Sue...



--
Martin Hogbin

On Jun 24, 10:33 am, wrote:
On Jun 24, 12:01 am, Roland PJ wrote:

Red-shiftof distant objects could be due to ...
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

How does your theory explains the fact that thered-shiftis larger
for galaxies that are farther away? Should you assume that far
galaxies are more massive?


It depends what you've used to determine that the galaxies are further
away. Have you used brightness? If so, then you haven't eliminated the
possibility that both the dimness _and_ the red-shift are due to the
galaxy being not necessarily further away, but either denser (more
tightly packed with stars), or more massive.

And note that using brightness seems to be the first rung in the
standard 'distance ladder' of cosmological measurement.

Roland

On Jun 24, 10:39 am, "Martin Hogbin"
wrote:
"Roland PJ" wrote in ooglegroups.com...
Red-shiftof distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

It seems that most discussion ofred-shiftcentres around the
assumption that SR recession is the cause (and hence that the universe
is expanding).

Why has GR time dilation been eliminated as a cause?

It has not been eliminated it is a contributing factor.

Yes, I'm sure it _is_ at least a contributing factor, and thanks for
the links.

What I'm asking is why the history of cosmological distance
measurement (the 'distance ladder') seems to ignore it completely, and
focus only on recession speed.

That can't be right, can it?

Regards
Roland

On Jun 23, 11:01 pm, Roland PJ wrote:
Red-shift of distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.

It seems that most discussion of red-shift centres around the
assumption that SR recession is the cause (and hence that the universe
is expanding).

Actually, it is neither.

The red-shift is modeled best by the FRW class of manifolds. Basically
all points move away from eachother - and the effect is the red-shift.


Why has GR time dilation been eliminated as a cause?

The universe would have long since collapsed.


So, why should most objects exhibit a red-shift, rather than a neutral
average shift? My best answer is that we, on earth, are at the edge of
our galaxy (the milky way), and hence quite far from the concentration
of mass near the centre of our galaxy.

You are not understanding. EVERYTHING not gravitationally bound [ie:
outside the local group] exhibits the redshift in a manner consistent
with the Hubble law.


On the other hand, most matter (stars) in the universe are close to
the centre of their galaxies, so, on average, most objects should
exhibit a red-shift to us on earth.

Now explain why close stuff isn't nearly as red-shifted as stuff
really far away, and try to do that without invoking amounts of mass
that dwarf the entire universe combined.


A corollary of this is that stars near the centre of our own galaxy
(the milky way) should also exhibit red-shift to us (even though they
are clearly not moving away from us on average). This should be
testable, although I'm not sure how one would identify a bright object
as a star in the center of our galaxy, rather than a distant object
shining through (brightness?).

Gravitational redshift _is_ observed, but you are missing the point.
IT IS TOO WEAK. Calculate it!


Hubble, Edwin, "A Relation between Distance and Radial Velocity among
Extra-Galactic Nebulae" (1929) Proceedings of the National Academy of
Sciences of the United States of America, Volume 15, Issue 3, pp.
168-173

Try picking up something published in the last thirty years.


Note that Hubble (and presumably all that follow) use _luminosity_ as
a measure of _distance_. However, luminosity is actually also a
measure of GR time dilation, independent of distance, as described
above.

Luminosity is only a measure of distance because Cephid variables were
discovered. That, combined with the Hubble law, gives a very good
measure of distance for distances too large to be measured with
parallax. Time dilation has NOTHING to do with it - 5 minutes [if
that] of computations will reveal how bad of an idea attributing red-
shift to time dilation is.


Just some ideas.
Flame away

Roland

On Jun 24, 12:12 pm, Eric Gisse wrote:
On Jun 23, 11:01 pm, Roland PJ wrote:

Red-shift of distant objects could be due to two different reasons:

1. Recession speed away from the earth, a special relativistic
effect.
2. Time dilation due to proximity to a concentration of mass, a
general relativistic effect.


Why has GR time dilation been eliminated as a cause?

The universe would have long since collapsed.


So, why should most objects exhibit a red-shift, rather than a neutral
average shift? My best answer is that we, on earth, are at the edge of
our galaxy (the milky way), and hence quite far from the concentration
of mass near the centre of our galaxy.

You are not understanding. EVERYTHING not gravitationally bound [ie:
outside the local group] exhibits the redshift in a manner consistent
with the Hubble law.

I don't understand what you're saying here.

On the other hand, most matter (stars) in the universe are close to
the centre of their galaxies, so, on average, most objects should
exhibit a red-shift to us on earth.

Now explain why close stuff isn't nearly as red-shifted as stuff
really far away, and try to do that without invoking amounts of mass
that dwarf the entire universe combined.

This might be a circular argument. If you've used brightness at any
stage in deciding what's 'close' or 'far', without taking GR time
dilation into account, then you might not have a good idea of what's
far and what's near.


Gravitational redshift _is_ observed, but you are missing the point.
IT IS TOO WEAK. Calculate it!

Yes, this is exactly the kind of answer I was looking for. Given that
I'll almost certainly cock up the calculation on at least the first
three attempts, I'd be gratefull for any pointers.

Note that Hubble (and presumably all that follow) use _luminosity_ as
a measure of _distance_. However, luminosity is actually also a
measure of GR time dilation, independent of distance, as described
above.

Luminosity is only a measure of distance because Cephid variables were
discovered. That, combined with the Hubble law, gives a very good
measure of distance for distances too large to be measured with
parallax. Time dilation has NOTHING to do with it - 5 minutes [if
that] of computations will reveal how bad of an idea attributing red-
shift to time dilation is.

Yes, absolutely, but Cephid variables are the first rung on the
'distance ladder', and I have found no evidence of anyone considering
GR time-dilation effects. This may be simpy because it was eliminated
early on as irrelevantly small, but I have seen no-one mention that.
And all 'modern' discussions (papers, if you like) on cosmological
distance seem to share a direct line back to the Hubble paper.

So, thanks, seems like I'll have to have a crack at some actual
computations . What's the right kind of estimate for 'dark matter'
and 'dark energy'? Or should I simply ignore these frst time round
(and almost certainly get the wrong answer)?

Roland