red shift: doppler or einstein?

Sam Wormley wrote:
I don't think this answers the question.
This is just 2 equations to describe how a wavelength shift can be related
to two different causes.

Question .. how can we distinguish a red shift due to a moving object from a
red shift due to a gravitational field.

md wrote:
relativity predicts a red-shift for light traveling "up" in a gravity
field. Doppler predicts a red-shift for light emitted from an object
moving away from us.

How can we distinguish the two? When we measure the red-shift of a
distant object, how can we conclude that it moves away from us? It might
also be that it is not moving away, but it is very heavy instead?


Relativistic Redshift
http://scienceworld.wolfram.com/phys...cRedshift.html

Gravitational Redshift
http://scienceworld.wolfram.com/phys...lRedshift.html

Doppler Effect
http://scienceworld.wolfram.com/phys...lerEffect.html

These three sources of redshift can usually be sorted by the context
of other data made in the measurement process.

relativity predicts a red-shift for light traveling "up" in a gravity field.
doppler predicts a red-shift for light emitted from an object moving away from us.

How can we distinguish the two? When we measure the red-shift of a distant object, how can we
conclude that it moves away from us? It might also be that it is not moving away, but it is
very heavy instead?

--
md
10" LX200GPS-SMT
ETX105
www.xs4all.nl/~martlian

md wrote:
relativity predicts a red-shift for light traveling "up" in a gravity field.
Doppler predicts a red-shift for light emitted from an object moving away from us.

How can we distinguish the two? When we measure the red-shift of a distant object, how can we
conclude that it moves away from us? It might also be that it is not moving away, but it is
very heavy instead?


Relativistic Redshift
http://scienceworld.wolfram.com/phys...cRedshift.html

Gravitational Redshift
http://scienceworld.wolfram.com/phys...lRedshift.html

Doppler Effect
http://scienceworld.wolfram.com/phys...lerEffect.html

These three sources of redshift can usually be sorted by the context
of other data made in the measurement process.

"Sam Wormley" wrote in message news:exPPd.66163$EG1.51167@attbi_s53...
md wrote:
relativity predicts a red-shift for light traveling "up" in a gravity field.
Doppler predicts a red-shift for light emitted from an object moving away from us.

How can we distinguish the two? When we measure the red-shift of a distant object, how can
we
conclude that it moves away from us? It might also be that it is not moving away, but it is
very heavy instead?


Relativistic Redshift
http://scienceworld.wolfram.com/phys...cRedshift.html

Gravitational Redshift
http://scienceworld.wolfram.com/phys...lRedshift.html

Doppler Effect
http://scienceworld.wolfram.com/phys...lerEffect.html

thanks for the formulae, but they did not really answer my question.

These three sources of redshift can usually be sorted by the context
of other data made in the measurement process.

how?
--
md
10" LX200GPS-SMT
ETX105
www.xs4all.nl/~martlian

One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.

This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------

"md" not given to avoid spam wrote in message
...

"Sam Wormley" wrote in message
news:exPPd.66163$EG1.51167@attbi_s53...
md wrote:
relativity predicts a red-shift for light traveling "up" in a gravity
field.
Doppler predicts a red-shift for light emitted from an object moving away
from us.

How can we distinguish the two? When we measure the red-shift of a distant
object, how can
we
conclude that it moves away from us? It might also be that it is not moving
away, but it is
very heavy instead?


Relativistic Redshift
http://scienceworld.wolfram.com/phys...cRedshift.html

Gravitational Redshift
http://scienceworld.wolfram.com/phys...lRedshift.html

Doppler Effect
http://scienceworld.wolfram.com/phys...lerEffect.html

thanks for the formulae, but they did not really answer my question.

These three sources of redshift can usually be sorted by the context
of other data made in the measurement process.

how?
--
md
10" LX200GPS-SMT
ETX105
www.xs4all.nl/~martlian

On Mon, 14 Feb 2005 05:08:56 GMT, "David Nakamoto"
wrote:

One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.

This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.
Gravity can be ruled out pretty much because it is a feeble effect.
The sun has pretty good gravity 27G but the gravity redshift z = 635/c
= 0.0000021.
A galaxy with this shift would have Doppler velocity of 635km/second
which is very small cosmologically, well, 0.0000021 of c. The distance
computed using Hubble's constant would be 30,000 LY which is only
about 1 2 millionth of the radius of the universe (13BLY).
Mr. Dual Space

If you have something to say, write an equation.
If you have nothing to say, write an essay

"John C. Polasek" wrote in message
...
On Mon, 14 Feb 2005 05:08:56 GMT, "David Nakamoto"
wrote:

One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.

This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.

Gravity can be ruled out pretty much because it is a feeble effect.

it would solve some dark matter issues :-) perhaps we have it all wrong and are those galaxies
much heavier than we thought ;-)

waz wrote:
Sam Wormley wrote:
I don't think this answers the question.
This is just 2 equations to describe how a wavelength shift can be related
to two different causes.

Question .. how can we distinguish a red shift due to a moving object from a
red shift due to a gravitational field.

In an isolated universe with no other features to observe and only a
point source to look at you can't. But we live in a more interesting
universe - galaxies are not point sources and space isn't quite empty.

The gravitational redshift is so very much weaker than the Doppler or
cosmological expansion components that you would need galaxies to be
incredibly massive objects and all of the object would have to be inside
the deepest part of the potential well - otherwise you would see the
edges of your putative ultra massive galaxy at a different redshift to
the centre. This is not observed.

If galaxies were so immensely massive their gravitational lensing
effects on even more distant objects would not match what is observed.

The final nail in the coffin for gravitational redshift as the main
component is the so called Lyman forest of neutral hydrogen clouds sat
in between us and very remote quasars and galaxies. It would require
very contrived physics to place these clouds in just the right positions
inside a deep gravitational field to mimic what is actually observed and
they would not be stable.

It is altogether simpler and much more reasonable that these objects are
in fact very distant and very luminous. Once Blandford & Znajeck figured
out how to get ~30% of rest mass energy out of matter dropping into a
black hole and coupled with relativistic beaming the energy budget for
these objects is no longer an issue. It was a problem in the 60's when
hydrogen fusion was the most efficient way of releasing energy known and
was isotropic (rather like Kelvin's problem with powering the sun by
burning coal).

We have even seen the relativistic beams in some objects - eg M87,
Cygnus A and a host of other less well known bright objects.

Regards,
Martin Brown


md wrote:

relativity predicts a red-shift for light traveling "up" in a gravity
field. Doppler predicts a red-shift for light emitted from an object
moving away from us.

How can we distinguish the two? When we measure the red-shift of a
distant object, how can we conclude that it moves away from us? It might
also be that it is not moving away, but it is very heavy instead?


Relativistic Redshift
http://scienceworld.wolfram.com/phys...cRedshift.html

Gravitational Redshift
http://scienceworld.wolfram.com/phys...lRedshift.html

Doppler Effect
http://scienceworld.wolfram.com/phys...lerEffect.html

These three sources of redshift can usually be sorted by the context
of other data made in the measurement process.

John C. Polasek wrote:
On Mon, 14 Feb 2005 05:08:56 GMT, "David Nakamoto"
wrote:


One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.

This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.

Gravity can be ruled out pretty much because it is a feeble effect.
The sun has pretty good gravity 27G but the gravity redshift z = 635/c
= 0.0000021.
A galaxy with this shift would have Doppler velocity of 635km/second
which is very small cosmologically, well, 0.0000021 of c. The distance
computed using Hubble's constant would be 30,000 LY which is only
about 1 2 millionth of the radius of the universe (13BLY).

What makes you think that the radius of the universe is 13 BLY?


Bye,
Bjoern

md wrote:
"John C. Polasek" wrote in message
...

On Mon, 14 Feb 2005 05:08:56 GMT, "David Nakamoto"
wrote:


One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.

This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.

Gravity can be ruled out pretty much because it is a feeble effect.


it would solve some dark matter issues :-) perhaps we have it all wrong and are those galaxies
much heavier than we thought ;-)

Err, that would not solve dark matter issues - that would make them
*bigger*. We can measure with methods independent of Hubble's law for
many galaxies how far away they are. Then we can, using the seen
brightness, estimate how much mass is there. And that visible mass is by
far not enough to account for the observed red shift. So, if the red
shift is due to the gravitation of the galaxy, there has to be a *huge*
amount of non-visible, i.e. dark matter in them!


Bye,
Bjoern