"Roland PJ" wrote in message
ups.com...
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


Certain types of star are known to have a certain brightness....

http://hubblesite.org/newscenter/arc.../49/astrofile/
"Two well-defined primary distance indicators, or "standard candles," are
the Cepheids and fainter RR Lyrae stars. They have a regular variation in
brightness, and the period of this pulsation is closely linked to the star's
intrinsic brightness. So, if the pulsation period of a star is known, its
true brightness can be deduced. The distance to the star can then be
calculated by comparing its true brightness with its apparent brightness."

"Roland PJ" wrote in message
oups.com...
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?


Focus is not only on recession speed..

http://hubblesite.org/newscenter/arc.../49/astrofile/

"Two well-defined primary distance indicators, or "standard candles," are
the Cepheids and fainter RR Lyrae stars. They have a regular variation in
brightness, and the period of this pulsation is closely linked to the star's
intrinsic brightness. So, if the pulsation period of a star is known, its
true brightness can be deduced. The distance to the star can then be
calculated by comparing its true brightness with its apparent brightness."

On Jun 24, 1:20 pm, "CWatters"
wrote:
"Roland PJ" wrote in message

ups.com...



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

Certain types of star are known to have a certain brightness....

http://hubblesite.org/newscenter/arc.../49/astrofile/
"Two well-defined primary distance indicators, or "standard candles," are
the Cepheids and fainter RR Lyrae stars. They have a regular variation in
brightness, and the period of this pulsation is closely linked to the star's
intrinsic brightness. So, if the pulsation period of a star is known, its
true brightness can be deduced. The distance to the star can then be
calculated by comparing its true brightness with its apparent brightness."

That may be true for observers at the same GR time-dilation as the
Cepheid stars, but if a Cepheid is close to a large and/or dense mass,
then we, on earth, will observe the period to be longer, and the
brightness to be less, both to tue GR time-dilation.

Unfortunately for this 'standard candle', these errors don't cancel
out, but rather compound each other. A Cepheid with a longer observed
period is deemed to be intrinsically brighter, and when we observe it
to be dimmer than it is (due to GR time-dilation), we will interpret
the longer period and lower brightness as indicating the star is
significantly further than it really is.

In the limit case of a Cepheid orbiting a near-black-hole, this error
compounds essentially towards infinity. Of course, we don't observer
the near-black-hole cos it's red-shifted and dimmed off the scale. We
only see the Cepheid.

Thoughts?
Roland

On Jun 24, 2:51 pm, Roland PJ wrote:
On Jun 24, 1:20 pm, "CWatters"



wrote:
"Roland PJ" wrote in message

oups.com...

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

Certain types of star are known to have a certain brightness....

http://hubblesite.org/newscenter/arc.../49/astrofile/
"Two well-defined primary distance indicators, or "standard candles," are
the Cepheids and fainter RR Lyrae stars. They have a regular variation in
brightness, and the period of this pulsation is closely linked to the star's
intrinsic brightness. So, if the pulsation period of a star is known, its
true brightness can be deduced. The distance to the star can then be
calculated by comparing its true brightness with its apparent brightness."

That may be true for observers at the same GR time-dilation as the
Cepheid stars, but if a Cepheid is close to a large and/or dense mass,
then we, on earth, will observe the period to be longer, and the
brightness to be less, both to tue GR time-dilation.

Unfortunately for this 'standard candle', these errors don't cancel
out, but rather compound each other. A Cepheid with a longer observed
period is deemed to be intrinsically brighter, and when we observe it
to be dimmer than it is (due to GR time-dilation), we will interpret
the longer period and lower brightness as indicating the star is
significantly further than it really is.

In the limit case of a Cepheid orbiting a near-black-hole, this error
compounds essentially towards infinity. Of course, we don't observer
the near-black-hole cos it's red-shifted and dimmed off the scale. We
only see the Cepheid.

Thoughts?
Roland


Interesting.

The question is observational.. what are the distributions of cepheids
and other standard candles such as supernovae that have been measured
with parallax? How good is the luminosity - period relationship
really?

On Jun 24, 3:01 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?

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

So you're suggesting that objects in the universe become more massive
the further away from us they are located? And, since our view of the
universe isn't considered to be very special, how would you reconcile
that with the notion that the mass distribution of the universe must
be observer independent?

Dear Roland PJ:

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

1. Recession speed away from the earth, a special
relativistic effect.

.... also just classical Doppler.

2. Time dilation due to proximity to a concentration
of mass, a general relativistic effect.

No. We can measure gravitational time dialtion in the spectrum
of the sources. Distant sources are more redshifted...
regardless of their mass, only their distance.

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).

Absolutely incorrect. SR is limited to evaluating jets of
ejected material. It is GR that is used to describe expansion,
and the Hubble shift.

Why has GR time dilation been eliminated as a cause?

It hasn't, in fact it is key. Just not time dilation from
individual masses. What you picture will require special physics
as a function of distance, to red shift more distant stars more
than gravitation red shift shifts the same size and type of star
locally.

So, why should most objects exhibit a red-shift, rather
than a neutral average shift?

Because there is increased space(time) between you and the source
between instants. Imagine space(time) as sal****er taffy
stretched between your two hands, with your hands as two distant
stars. As time goes on (weather permitting) the taffy stretches,
and the distance between the two "stars" (measured along the
taffy) increases and signals between them take longer (red
shift). From this poor analogy, better ones are the balloon
analogy and the raisin bread analogy.

My best answer is that we, on earth, are at the edge
of our galaxy (the milky way),

Not quite... we are about halfway out.

and hence quite far from the concentration
of mass near the centre of our galaxy.

Doesn't matter. The spectra locally (inclusive of even the
Andromeda galaxy) are unsurprising. And we have all sorts of
candidates visible locally.

....
Just some ideas.
Flame away

If you are interested in more than your own ideas, you can start
he
http://www.astro.ucla.edu/~wright/cosmolog.htm
http://www.astro.ucla.edu/~wright/cosmo_01.htm
.... and if you have questions, you can either ask here or on
sci.astro.

David A. Smith

On Jun 24, 7:53 pm, Igor wrote:
On Jun 24, 3:01 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?



So you're suggesting that objects in the universe become more massive
the further away from us they are located? And, since our view of the
universe isn't considered to be very special, how would you reconcile
that with the notion that the mass distribution of the universe must
be observer independent?


No, I'm suggesting that we might have _both_ their distance and
recession speed wrong.

At the moment we interpret faint objects as being distant, and red-
shifted objects as being receding.

And we find there's a correlation between distance and recession
speed.

However, a faint and red-shifted object could simply be a nearby,
stationary object under the influence of nearby mass (perhaps
invisible to us), as a result of GR time dilation.

Roland

On Jun 24, 2:02 pm, Roland PJ wrote:
On Jun 24, 7:53 pm, Igor wrote:





On Jun 24, 3:01 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?

So you're suggesting that objects in the universe become more massive
the further away from us they are located? And, since our view of the
universe isn't considered to be very special, how would you reconcile
that with the notion that the mass distribution of the universe must
be observer independent?

No, I'm suggesting that we might have _both_ their distance and
recession speed wrong.

At the moment we interpret faint objects as being distant, and red-
shifted objects as being receding.

And we find there's a correlation between distance and recession
speed.

However, a faint and red-shifted object could simply be a nearby,
stationary object under the influence of nearby mass (perhaps
invisible to us), as a result of GR time dilation.

Roland

Maybe so, but the GR time dilation effect cannot be the dominate one
for the reasons I previously stated.

On Jun 24, 8:02 pm, "N:dlzc D:aol T:com \(dlzc\)"
wrote:
Dear Roland PJ:

"Roland PJ" wrote in message

oups.com...

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

1. Recession speed away from the earth, a special
relativistic effect.

... also just classical Doppler.

Except it needs finite light speed doesn't it, which was one of the
foundations of SR? I'd better check

2. Time dilation due to proximity to a concentration
of mass, a general relativistic effect.

No. We can measure gravitational time dialtion in the spectrum
of the sources. Distant sources are more redshifted...
regardless of their mass, only their distance.

Um, how can spectral analysis discriminate between time-dilation and
recession (or expansion, if you like)? The spectra are shifted in both
case, not so? Can you explain some more?

What you picture will require special physics
as a function of distance, to red shift more distant stars more
than gravitation red shift shifts the same size and type of star
locally.

OK, I have no idea what you mean by this.

So, why should most objects exhibit a red-shift, rather
than a neutral average shift?

Because there is increased space(time) between you and the source
between instants. Imagine space(time) as sal****er taffy
stretched between your two hands, with your hands as two distant
stars. As time goes on (weather permitting) the taffy stretches,
and the distance between the two "stars" (measured along the
taffy) increases and signals between them take longer (red
shift). From this poor analogy, better ones are the balloon
analogy and the raisin bread analogy.

Note that I was trying to answer this question according to my theory,
not pose it . Yes, I can see that expansion theories explain the
Hubble red-shift phenomenon. I was simply trying to propose a simpler
solution, namely plain old GR in a non-expanding universe. Occam's
razor and all.

My best answer is that we, on earth, are at the edge
of our galaxy (the milky way),

Not quite... we are about halfway out.

2/3 if you want to nit-pick

and hence quite far from the concentration
of mass near the centre of our galaxy.

Doesn't matter. The spectra locally (inclusive of even the
Andromeda galaxy) are unsurprising. And we have all sorts of
candidates visible locally.

Yes it does matter. GR time dilation is directly related to your
matter/energy environment. The fact that we are at the edge of our
galaxy means that matter near the denser core is red-shifted relative
to us. As Eric has pointed out, this difference might be too small to
matter, but you can't just wave it away with a magic wand without
doing the sums (which I intend to do... see questions below). Or
perhaps we are missing each other here - I'm not sure how your
'spectra' comment relates. Or are you saying that the spectra from
stars all over the milky way display no shift at all? In which case
time dilation clearly can't be a factor within our own galaxy.


If you are interested in more than your own ideas, you can start
hehttp://www.astro.ucla.edu/~wright/co...t/cosmo_01.htm
... and if you have questions, you can either ask here or on
sci.astro.

Thanks for the links. Will follow them up.

Now, what I really need to see whether my idea has any legs is an
accurate map of the Milky Way. Specifically, the density of matter
along the radial arms, and the shape of, and density of matter, within
the 'core'. What's crucial is the density gradient of stars within the
core. I can't find this anywhere at the moment. It seems pretty
obvious that the core is not entirely homogeneous, but rather gets
increasingly densely populated with stars towards the middle. But
what's the density curve here?

Thanks again for the response
Roland

On Jun 24, 8:16 pm, Igor wrote:
On Jun 24, 2:02 pm, Roland PJ wrote:



However, a faint and red-shifted object could simply be a nearby,
stationary object under the influence of nearby mass (perhaps
invisible to us), as a result of GR time dilation.

Roland

Maybe so, but the GR time dilation effect cannot be the dominate one
for the reasons I previously stated.


I think I missed that. Would you mind repeating?

Thanks
Roland