On Mar 21, 4:47 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> In article
> <c42b9285-949a-460e-8be8-ce3f1d068...@p6g2000yqi.googlegroups.com>,
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > 1{g} The cosmological redshift of that emission event depends on the
> > time difference between the emission event and the detection event
> > (del t).
> No; it depends ONLY on the ratio of the scale factor of the universe now
> to that at the time the light was emitted. Check out any introductory
> cosmology textbook.
However, the scale factor ratio itself depends on the time difference,
as does the redshift
undress to reply) wrote:
> In article
> <10e87080-1c1b-466a-a72f-d980b3157...@p13g2000yqd.googlegroups.com>,
> "Anon E. Mouse" <agall...@gmail.com> writes:
> > Earlier I had said that chromatic aberration was not demonstrated for
> > gravitational lensing, but since that time it occurred to me that in
> > the population of stars outside the normal band there are Red Giants
> > and blue dwarfs, but there is no grouping of blue giants. (There are
> > red dwarfs, but the color temperature is different, I believe,
> > indicating they are small and or older.)
> > These two categories of unusual stars may exist only because the
> > chromatic aberration of red light is greater than that of blue light.
> > In other words, these stars may fit the normal band in size but be
> > atypical due to their high gamma's and corresponding divergent
> > aberrations.
> No. It is well known (check out any book on stellar structure and
> evolution, for example the one by Kippenhahn and Weigert) why stars hae
> the colours, sizes and masses they do. It has nothing to do with
> chromatic aberration.
I am aware that these theories of star size and color are independent
of chromatic aeration. Before 1905 gravitational lensing was not in
anyone's playbook. Other than my own contemplations and those of a
very very few others, I find no current evidence of consideration of
chromatic aberration due to gravitational lensing in Cosmology.
Now that experimental evidence clearly indicates gravitational lensing
chromatic aberration from that cause can also be considered, even if
this is novel thinking and not classical thought.
On Mar 21, 4:47 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> In article
> <c42b9285-949a-460e-8be8-ce3f1d068...@p6g2000yqi.googlegroups.com>,
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > 1{g} The cosmological redshift of that emission event depends on the
> > time difference between the emission event and the detection event
> > (del t).
> No; it depends ONLY on the ratio of the scale factor of the universe now
> to that at the time the light was emitted.
I beg to differ. The scale factor ratio is itself dependent on the
time difference (as is the cosmological redshift).
(I am sure you already actually know that, if you care to think about
this a bit more.)
> Check out any introductory
> cosmology textbook.
Hardly the most appropriate place to look for profound answers to deep
natural philosophical questions, I would hazard to suggest :-).
2{g} This time difference is associated with a spatial separation
between emission event and detection event, of d = c(del t)
The combined inference of 1{g} AND 2{g}, is that the scale factor
(hence redshift) actually depends on the radial distance d (from us
now).
However, since you have now called into question the validity of 1{g},
it would be appreciated if you could next confirm or refute that just
stated combined implication/inference.
On Mar 21, 9:48 pm, "Anon E. Mouse" <agall...@gmail.com> wrote:
[Moderator's note: Quoted text snipped. -P.H.]
> Now that experimental evidence clearly indicates gravitational lensing
> chromatic aberration from that cause can also be considered, even if
> this is novel thinking and not classical thought.
> AAG
Einstein said that light cannot bend without a change in velocity.
Rainbow says that velocity change is frequency dependent.
Ergo, you are correct.
However, I don't actually see what this has to do, exactly, with the
discussion here.
> However, I don't actually see what this has to do, exactly, with the
> discussion here.
Ergo I may or may not have a point. It is a reasonable hypothesis, but
not well known, accepted or at all proven. The relevance to this
discussion is;
If stars had well defined emission lines in their spectra then the red
would be bent more than the blue, by comparing degree of aberration a
direct inference of the apparent distance to a single source could be
made from the spectra of that source alone.
Typically, star's spectrographs do not have these sorts of well
defined emission lines as a dominant feature. Perhaps they can be
extracted from the rest of the spectral data. There typically are well
defined absorbtion lines, but these are assumed to be from
interstellar gasses and may not be representative of the source.
On Mar 21, 4:47 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> In article
> <c42b9285-949a-460e-8be8-ce3f1d068...@p6g2000yqi.googlegroups.com>,
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > 1{g} The cosmological redshift of that emission event depends on the
> > time difference between the emission event and the detection event
> > (del t).
> No; it depends ONLY on the ratio of the scale factor of the universe now
> to that at the time the light was emitted. Check out any introductory
> cosmology textbook.
Notwithstanding my earlier reply to this, your above statement does
however bring a more interesting point into sharp focus.
As the cosmological redshift has nothing to do with peculiar velocity
difference, This indicates there IS no significant peculiar velocity
difference between distant participants when considered at the same
time (both when relative to a later observer, and when interpreted in
the context of cosmological time)
I hope I don't have to now explicitly point out to you the logical
contradiction that this implies.
>> [[Mod. note -- Carlip expands on this further in
>> S. Carlip
>> "Aberration and the speed of gravity"
>> Physics Letters A 267 (2000) 81?87
>> http://dx.doi.org/10.1016/S0375-9601(00)00101-8 >> open-access preprint arXiv:gr-qc/9909087
>> -- jt]]
Detection of Galaxy Cluster Motions
with the Kinematic Sunyaev-Zel'dovich E ffect
arXiv:1203.4219v1 [astro-ph.CO] 19 Mar 2012
Such motions are measured in terms of micro Kelvin
indicating their negligible magnitude in terms of redshift.
> "In that case, one finds that the "force" in GR is not quite central?it
> does not point directly towards the source of the gravitational
> field?and that it depends on velocity as well as position.
I wouldn't worry too much about such inaccuracies relative to us, if I
were you Given Carlip's order of magnitude indicated error. Via a
rapid bit of very approximate mental arithmetic, I make this about 1
part in 10^60 for us in orbit around the Sun
Allowing for generous order of magnitude increases for the Sun's orbit
around the galactic nucleus, and the galaxy's orbit around the c of g
of the local cluster, AND extrapolating over the scale of the
universe, I still make this smaller than the expected range of the
strong nuclear force which is, naturally, dominated by quantum
uncertainty.
> No; it depends ONLY on the ratio of the scale factor of the universe now
> to that at the time the light was emitted. Check out any introductory
> cosmology textbook.
You are correct that the red-shift Chalky seems to be is talking about
is not consistent with the cosmological red-shift.
In fact if I follow his d2 > d argument he there would be no red-shift
for separated, co-linear same velocity source and observer. The
gamma's would offset and no red-shift. However, the light path would
be d the separation at emission plus v_0 * d/c the proper motion of
the observer during time of flight. This would create no red-shift but
would (should) reduce apparent luminosity.
If the big bang theory is correct this should be a common case with
pretty large values for d2-d thus it might be an evidence of
cosmological anisotropy. I don't believe this case is covered in
Einstein's (1905) because that substantially predates big bang and as
I say, I don't think red-shift, section 3, or doppler effects, section
4 apply. This seems to be fairly unique to Chalky, assuming I am
correctly following the reasoning behinds his posts.
P.S. Chalky the problem with truncated lines was due to my using a
large font because of my near blindness. If I reduce the font before
send - no more problems - thank you for helping me solve this problem.
Chalky <chalkys...@bleachboys.co.uk> writes: > On Mar 21, 4:47 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
> undress to reply) wrote:
> > In article
> > <c42b9285-949a-460e-8be8-ce3f1d068...@p6g2000yqi.googlegroups.com>,
> > Chalky <chalkys...@bleachboys.co.uk> writes:
> > > 1{g} The cosmological redshift of that emission event depends on the
> > > time difference between the emission event and the detection event
> > > (del t).
> > No; it depends ONLY on the ratio of the scale factor of the universe now
> > to that at the time the light was emitted. Check out any introductory
> > cosmology textbook.
> However, the scale factor ratio itself depends on the time difference,
> as does the redshift
The redshift tells you the ratio of the scale factors at the two times.
It tells you nothing else. From the redshift, you can calculate other things if you know the cosmological parameters. For a given redshift, the time the light was in transit can be any number you like.
> > > 1{g} The cosmological redshift of that emission event depends on the
> > > time difference between the emission event and the detection event
> > > (del t).
> > No; it depends ONLY on the ratio of the scale factor of the universe now
> > to that at the time the light was emitted.
> I beg to differ. The scale factor ratio is itself dependent on the
> time difference (as is the cosmological redshift).
> (I am sure you already actually know that, if you care to think about
> this a bit more.)
> > Check out any introductory
> > cosmology textbook.
> Hardly the most appropriate place to look for profound answers to deep
> natural philosophical questions, I would hazard to suggest :-).
> 2{g} This time difference is associated with a spatial separation
> between emission event and detection event, of d = c(del t)
> The combined inference of 1{g} AND 2{g}, is that the scale factor
> (hence redshift) actually depends on the radial distance d (from us
> now).
> However, since you have now called into question the validity of 1{g},
> it would be appreciated if you could next confirm or refute that just
> stated combined implication/inference.
See my reply to another post in this thread.
As Sagan said, extraordinary claims require extraordinary evidence. If you want to question the validity of basic ideas in cosmology (we are not talking about some perhaps difficult interpretation, but just very basis stuff), you need to have a very, very good reason to do so.
In article
<09cd403d-aa94-41ff-ab5b-4dbf38783...@do4g2000vbb.googlegroups.com>,
Chalky <chalkys...@bleachboys.co.uk> writes: > Einstein said that light cannot bend without a change in velocity.
> Rainbow says that velocity change is frequency dependent.
This does not imply any sort of chromatic effect in gravitational lensing, which is known to be achromatic. (Chromatic effects can be observed if the lensed source has a colour gradient, but the effect itself is achromatic.) In a rainbow, the chromatic effect is indeed due to different colours travelling at different speeds, which causes different amounts of refraction. However, this does not imply that all refraction is frequency dependent. Normal refraction is frequency dependent because the speed of light in a medium depends on the frequency because of the electromagnetic interaction between light in the medium. In gravitational lensing, refraction is not caused by a medium and it is frequency dependent for much the same reason that bodies of different mass fall at the same speed: this is the natural consequence of a geometric effect.
In article
<93244218-8d5e-45e3-9862-3f64f71ec...@em9g2000vbb.googlegroups.com>,
"Anon E. Mouse" <agall...@gmail.com> writes:
> If stars had well defined emission lines
They certainly have well defined absorption lines, which should be just as good.
> in their spectra then the red
> would be bent more than the blue,
Not in the case of anything caused by gravitation.
> There typically are well
> defined absorbtion lines, but these are assumed to be from
> interstellar gasses and may not be representative of the source.
Most absorption lines in stellar spectra come from the atmosphere of the star itself.
In article
<7de9082f-2757-4258-b501-1592baacf...@hs8g2000vbb.googlegroups.com>,
Chalky <chalkys...@bleachboys.co.uk> writes: > > > 1{g} The cosmological redshift of that emission event depends on the
> > > time difference between the emission event and the detection event
> > > (del t).
> > No; it depends ONLY on the ratio of the scale factor of the universe now
> > to that at the time the light was emitted. Check out any introductory
> > cosmology textbook.
> Notwithstanding my earlier reply to this, your above statement does
> however bring a more interesting point into sharp focus.
> As the cosmological redshift has nothing to do with peculiar velocity
> difference,
Right.
> This indicates there IS no significant peculiar velocity
> difference between distant participants when considered at the same
> time (both when relative to a later observer, and when interpreted in
> the context of cosmological time)
I'm not sure this is well defined.
I think that, for almost all purposes, it makes sense to distinguish peculiar velocities and the redshifts they cause from the cosmological redshift. However, this is not strictly necessary if one is willing to use another definition of velocity which is otherwise not used in cosmology (in particular, it is not the change in time of any distance).
See E. F. Bunn & D. W. Hogg, Am. J. Ph., 77, 688, 2009 (also available at http://arxiv.org/abs/0808.1081 ).
On Mar 24, 7:11 pm, "Anon E. Mouse" <agall...@gmail.com> wrote:
> > No; it depends ONLY on the ratio of the scale factor of the universe now
> > to that at the time the light was emitted. Check out any introductory
> > cosmology textbook.
> You are correct that the red-shift Chalky seems to be is talking about
> is not consistent with the cosmological red-shift.
> In fact if I follow his d2 > d argument he there would be no red-shift
> for separated, co-linear same velocity source and observer.
Then, clearly, you did not follow it.
Either I did not explain myself correctly, or you misunderstood my
meaning.
d2 refers to luminosity distance after the cosmological redshift is
removed. (I find it easier to understand the physics without the
artifice of a distance measure which tries to do both things at
once).
That does not mean that the cosmological redshift is expunged from
reality.
It just means that the effect of the cosmological redshift can now be
added to d2 to obtain luminosity distance in a single,
straightforward, and unambiguous step.
> P.S. Chalky the problem with truncated lines was due to my using a
> large font because of my near blindness. If I reduce the font before
> send - no more problems - thank you for helping me solve this problem.
My pleasure
I had a bank manager once who was nearly blind, and his screen
typeface was so huge, I wondered how he ever managed to get anything
done, either on 'puter or t'internet.
During our meeting to discuss a new Barclays account for me, he came
up with the classic. "I may be nearly blind but don't let that fool
you." He then phoned up the Caymen islands for a friend of mine (who
already had a Barclays account), to check out the appropriate accounts
there for tax evasion. (Nothing ever came of that enquiry, afaik)
On Mar 24, 7:11 pm, "Anon E. Mouse" <agall...@gmail.com> wrote:
> > No; it depends ONLY on the ratio of the scale factor of the universe now
> > to that at the time the light was emitted. Check out any introductory
> > cosmology textbook.
> You are correct that the red-shift Chalky seems to be is talking about
> is not consistent with the cosmological red-shift.
> In fact if I follow his d2 > d argument he there would be no red-shift
> for separated, co-linear same velocity source and observer.
Then, clearly, you did not follow it.
Either I did not explain myself correctly, or you misunderstood my
meaning.
d2 refers to luminosity distance after the cosmological redshift is
removed. (I find it easier to understand the physics without the
artifice of a distance measure which tries to do both things at once).
That does not mean that the cosmological redshift is expunged from
reality.
It simply means that the effect of the cosmological redshift must now
be added to d2 to then obtain luminosity distance in a single,
straightforward, and unambiguous step.
> P.S. Chalky the problem with truncated lines was due to my using a
> large font because of my near blindness. If I reduce the font before
> send - no more problems - thank you for helping me solve this problem.
My pleasure
I had a bank manager once who was nearly blind, and his screen
typeface was so huge, I wondered how he ever managed to get anything
done, either on computer or internet.
During our first meeting, with a friend of mine, he came up with the
classic. "I may be nearly blind but don't let that fool you." He then
phoned up his Caymen islands branch at his bank's expense for that
friend, to check out the account arrangements there, which were
suitable for tax evasion. (No actual tax evasion resulted from that
phone call, afaik)
undress to reply) wrote:
> In article
> <09cd403d-aa94-41ff-ab5b-4dbf38783...@do4g2000vbb.googlegroups.com>,
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > Einstein said that light cannot bend without a change in velocity.
> > Rainbow says that velocity change is frequency dependent.
> This does not imply any sort of chromatic effect in gravitational
> lensing, which is known to be achromatic. (Chromatic effects can be
> observed if the lensed source has a colour gradient, but the effect
> itself is achromatic.) In a rainbow, the chromatic effect is indeed du=
e
> to different colours travelling at different speeds, which causes
> different amounts of refraction. However, this does not imply that all
> refraction is frequency dependent. Normal refraction is frequency
> dependent because the speed of light in a medium depends on the
> frequency because of the electromagnetic interaction between light in
> the medium. In gravitational lensing, refraction is not caused by a
> medium and it is frequency dependent for much the same reason that
> bodies of different mass fall at the same speed: this is the natural
> consequence of a geometric effect.
I am aware of the debate within NIST about the frequency independence
of c. I am also aware that the view that velocity is frequency
independent is dominant point of view. I am also aware that if the
laser interferometry protocol for the standard meter has been done
with lasers of a different molecular composition to that of the NIST
standard and that in this case you obtain an ever so slightly
different result. This experimental data is the only experimental
evidence of which I am aware that might be used to resolve the
question of chromatic aberration in gravitational lensing.
I have personally observed stellar spectra in which the red absorption
lines are more shifted and also broader than the blue. I believe the
averaging of this data is the common practice. Seems to me a shame to
discard such potentially useful data.
You state the opinion that gravitational lensing is achromatic as if
that opinion is an established fact. If there is experimental or
observational evidence of which I am unaware that proves the
achromatic case I would be pleased to look at that evidence.
> > This does not imply any sort of chromatic effect in gravitational
> > lensing, which is known to be achromatic. (Chromatic effects can be
> > observed if the lensed source has a colour gradient, but the effect
> > itself is achromatic.) In a rainbow, the chromatic effect is indeed due
> > to different colours travelling at different speeds, which causes
> > different amounts of refraction. However, this does not imply that all
> > refraction is frequency dependent. Normal refraction is frequency
> > dependent because the speed of light in a medium depends on the
> > frequency because of the electromagnetic interaction between light in
> > the medium. In gravitational lensing, refraction is not caused by a
> > medium and it is frequency dependent for much the same reason that
> > bodies of different mass fall at the same speed: this is the natural
> > consequence of a geometric effect.
> I am aware of the debate within NIST about the frequency independence
> of c.
Can you point us to some references to this debate?
> I am also aware that the view that velocity is frequency
> independent is dominant point of view. I am also aware that if the
> laser interferometry protocol for the standard meter has been done
> with lasers of a different molecular composition to that of the NIST
> standard and that in this case you obtain an ever so slightly
> different result.
References?
> This experimental data is the only experimental
> evidence of which I am aware that might be used to resolve the
> question of chromatic aberration in gravitational lensing.
Even if you have evidence for the velocity of light being dependent on frequency in a vacuum---extraordinary claims require extraordinary evidence---then the relation of this to chromaticity or lack thereof in gravitational lensing is not clear.
> I have personally observed stellar spectra in which the red absorption
> lines are more shifted and also broader than the blue. I believe the
> averaging of this data is the common practice. Seems to me a shame to
> discard such potentially useful data.
A stellar spectrum is produced by some physical apparatus which introduces a variety of instrumental effects. In particular, the scale might not be a linear scale. Also, there are well known astrophysical processes which could cause a slightly different redshift for different frequencies for spectral lines, ditto for broadening.
> You state the opinion that gravitational lensing is achromatic as if
> that opinion is an established fact.
It is certainly accepted that this follows from GR.
> If there is experimental or
> observational evidence of which I am unaware that proves the
> achromatic case I would be pleased to look at that evidence.
There are thousands of published observations of gravitational lensing.
Do you think any of them indicate the effect you claim?
> I am aware of the debate within NIST about the frequency independence
> of c.
Really? References please.
There are various limits on this, from a few parts per million to a few parts in 10^21 (!).
> I am also aware that the view that velocity is frequency
> independent is dominant point of view.
I suspect this is an overstatement. Without references I cannot tell. But I know of no definitive reference that measured different speeds IN VACUUM for different frequencies of light. If so, this would be the first refutation of Special Relativity within its domain.
> I am also aware that if the
> laser interferometry protocol for the standard meter has been done
> with lasers of a different molecular composition to that of the NIST
> standard and that in this case you obtain an ever so slightly
> different result.
Again, references please.
> This experimental data is the only experimental
> evidence of which I am aware that might be used to resolve the
> question of chromatic aberration in gravitational lensing.
Well, GR predicts that gravitational lensing is independent of the frequency of the EM radiation used. And, for instance, the Shapiro time delay and the bending of light by the sun have been measured to high precision for both light and radio waves without claiming refutation of GR.
> I have personally observed stellar spectra in which the red absorption
> lines are more shifted and also broader than the blue.
OK. But are there other effects involved? I suspect so.
> You state the opinion that gravitational lensing is achromatic as if
> that opinion is an established fact.
It is certainly predicted to be achromatic by GR. And AFAIK there are no definitive measurements that contradict this. References, Please.
> You state the opinion that gravitational lensing is achromatic as if
> that opinion is an established fact. If there is experimental or
> observational evidence of which I am unaware that proves the
> achromatic case I would be pleased to look at that evidence.
That the speed of light in the vacuum does not depend on its color
can be seen in supernova explosions. We see light of different color
arrive together, not separated.
What is your prediction for light from a supernova of which you see two pictures?
