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Distance and inverse square law in SR
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Chalky
Mar 10, 2012, 10:07:30 AM3/10/12
to
Can anyone here give me a clear and unambiguous answer to the
following very basic question, in the context of special relativity:
Relative to the inertial observer who considers himself at rest, is
the observed intensity of a signal from a distant EM emitter,
inversely proportional to the square of the "instantaneous" ie.
"geometric" distance of the emitter:
(A) At the time of emission
(B) At the time of detection, or
(C) Neither of the above
By "instantaneous" ie. "geometric" distance, I mean the distance of
the emitter at the time of emission, which could, in principle, be
determined by the radar method, if the time of emission is known in
advance.
I am also assuming there is no significant intervening matter to
obscure or distort the signal.
I additionally appreciate that the observed intensity also depends on
the relativistic Doppler shift of the emitter, at the time of emission
Until very recently, I would have said unquestioningly that the
correct answer is (A).
However, I have started to question my own sanity in this respect, for
reasons I would prefer not to go into at present, in order to avoid
any possible clouding the issue.
I have already attempted to get this question answered at
sci.physics.foundations, to no avail, beyond generating a variety of
increasingly complicated responses, none of which appear to answer
this basic question.
following very basic question, in the context of special relativity:
Relative to the inertial observer who considers himself at rest, is
the observed intensity of a signal from a distant EM emitter,
inversely proportional to the square of the "instantaneous" ie.
"geometric" distance of the emitter:
(A) At the time of emission
(B) At the time of detection, or
(C) Neither of the above
By "instantaneous" ie. "geometric" distance, I mean the distance of
the emitter at the time of emission, which could, in principle, be
determined by the radar method, if the time of emission is known in
advance.
I am also assuming there is no significant intervening matter to
obscure or distort the signal.
I additionally appreciate that the observed intensity also depends on
the relativistic Doppler shift of the emitter, at the time of emission
Until very recently, I would have said unquestioningly that the
correct answer is (A).
However, I have started to question my own sanity in this respect, for
reasons I would prefer not to go into at present, in order to avoid
any possible clouding the issue.
I have already attempted to get this question answered at
sci.physics.foundations, to no avail, beyond generating a variety of
increasingly complicated responses, none of which appear to answer
this basic question.
Tom Roberts
Mar 10, 2012, 3:11:17 PM3/10/12
to
On 3/10/12 3/10/12 9:07 AM, Chalky wrote:
> Can anyone here give me a clear and unambiguous answer to the
> following very basic question, in the context of special relativity:
>
> Relative to the inertial observer who considers himself at rest, is
> the observed intensity of a signal from a distant EM emitter,
> inversely proportional to the square of the "instantaneous" ie.
> "geometric" distance of the emitter:
>
> (A) At the time of emission
> (B) At the time of detection, or
> (C) Neither of the above
The situation is more complicated than you think. This is not really related to
> Can anyone here give me a clear and unambiguous answer to the
> following very basic question, in the context of special relativity:
>
> Relative to the inertial observer who considers himself at rest, is
> the observed intensity of a signal from a distant EM emitter,
> inversely proportional to the square of the "instantaneous" ie.
> "geometric" distance of the emitter:
>
> (A) At the time of emission
> (B) At the time of detection, or
> (C) Neither of the above
"distance between emitter and detector", but rather the distance between the
emission EVENT and the corresponding detection EVENT. And the result does not
depend only on that distance (as "inverse square law" implies); in general, the
detected intensity from a moving emitter of constant intensity will be time
dependent.
There are two cases to consider:
1. Both emitter and observer are at rest in a single inertial frame.
Both A and B apply.
2. Any other physical situation.
C applies.
For an observer at rest in an inertial frame, and an emitter moving relative to
that frame, the inverse square law does not apply. The detected intensity
depends not only on some measure of distance between emitter and observer, but
also on the angle between the emitter's velocity and the line-of-sight to the
detector. This is due to two effects:
a) The detector's aperture will intercept different solid angles of the
source's emission, depending on angle.
b) The angle-dependent Doppler shift affects the energy of the radiation,
and thus the measured intensity.
For the case of multiple measurements at constant angle but varying distance,
with the distance measurement being performed in the observer's inertial frame,
then the intensity is inversely proportional to the square of the distance
measured at the time of emission. That is, for this restricted case your (A)
applies.
[Any motion of the source after emitting the light that will be
detected cannot possibly affect the measurement, so (B) cannot
possibly apply except for special case 1 above.]
Remember the context is SR. In GR the situation is considerably more complex,
but the inverse square law still does not apply, and there are more situations
that can affect the detected intensity (e.g. microlensing, multiple images, etc.).
Tom Roberts
Chalky
Mar 11, 2012, 11:40:42 AM3/11/12
to
On Mar 10, 8:11 pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote:
> The situation is more complicated than you think.
Actually, both the situation, and derivation from first principles,
> The situation is more complicated than you think.
that I needed to double check, is more simple than _you_ think. And,
that was the real reason for the query, as I believe I stated at spf,
without going into details.
If you want the relevant detail, the emitting object under
investigation is either receding or approaching (or both at different
times) and there is no tangential velocity to consider.
> This is not really related to
> "distance between emitter and detector", but rather the distance between the
> emission EVENT and the corresponding detection EVENT.
spf, before you entered the discussion there). The question is
actually very simple. What IS that distance at any given time,
relative to said inertial observer. You don't need 4 vectors OR tensor
calculus to answer that question!
> And the result does not
> depend only on that distance (as "inverse square law" implies); in general, the
> detected intensity from a moving emitter of constant intensity will be time
> dependent.
events is time dependent, and because observed light intensity also
depends on the Doppler shift, as we all know.
Even in the application of Newton's inverse square law, everyone is
assumed to have enough intelligence to appreciate that.
> [Any motion of the source after emitting the light that will be
> detected cannot possibly affect the measurement, so (B) cannot
> possibly apply except for special case 1 above.]
So you do agree that option (A) is far more realistic than option (B)?
Anon E. Mouse
Mar 12, 2012, 4:30:32 AM3/12/12
to
The apparent distance given by a received signal is the distance
traveled by that signal. Assuming the receipt is instant, the send
time is in the past for the receiver by D/c and the signal arrives
looking as if it came from the senders past position.
past position =3D present position -v(sender)/c.
Per your question all the relative motion is "assigned" to the sender.
Although it is not typically possible to do this.
Specifically: In the radar method, this is not possible the signal
travels from the sender to the reflector and then back to the sender,
both of whom have moved during the time of signal flight. Compensate
once for reflector motion outbound, compensate again for reflector
motion on the return, compensate receiver once for total time of
flight.
It is called relativity because a basic assumption of the theory is
that the "absolute" motion of either party can not be distinguished
from "absolute" motion of the other. Makes everything relative. At
least in terms of frequency.
Amplitude (intensity) is another matter. Standard candles =3D amplitude.
Amplitude is believed to fall according to 1/Pi*r^2.
Chromatic aberration is another matter and is based on the somewhat
untested assumption that frequency shifts are proportional to the
frequency. This is true for lensing, but not yet proven for
gravitational lensing, or relativity.
regards,
AAG
Chalky
Mar 12, 2012, 7:59:26 AM3/12/12
to
[[Mod. note -- I think the confusion being queried here is probably
due to 8-bit (non-ASCII) characters being mangled by Usenet. On my
computer the offending symbol shows up as "=3D"; I don't know what it
was originally intended to mean.
-- jt]]
What does =3D mean in this posting?
due to 8-bit (non-ASCII) characters being mangled by Usenet. On my
computer the offending symbol shows up as "=3D"; I don't know what it
was originally intended to mean.
-- jt]]
Chalky
Mar 12, 2012, 11:55:16 AM3/12/12
to
On Mar 12, 8:30 am, "Anon E. Mouse" <agall...@gmail.com> wrote:
[[Mod. note -- I think the confusion being queried here is probably
due to 8-bit (non-ASCII) characters being mangled by Usenet. On my
computer the offending symbol shows up as "=3D"; I don't know what it
was originally intended to mean.
-- jt]]
[[Note to mod -- Strangely, my own quote of myself has started to show
[[Mod. note -- I think the confusion being queried here is probably
due to 8-bit (non-ASCII) characters being mangled by Usenet. On my
computer the offending symbol shows up as "=3D"; I don't know what it
was originally intended to mean.
-- jt]]
this error now too.
as at http://groups.google.com/group/sci.physics.research/msg/f6a0632684162263
Hence =3D means =
=A0 would seem to mean nothing]]
unique spacetime event
> Compensate
> once for reflector motion outbound, compensate again for reflector
> motion on the return, compensate receiver once for total time of
> flight.
>
> It is called relativity because a basic assumption of the theory is
> that the "absolute" motion of either party can not be distinguished
> from "absolute" motion of the other. Makes everything relative. At
> least in terms of frequency.
>
> Amplitude (intensity) is another matter. Standard candles =3D amplitude.
Chalky
Mar 13, 2012, 9:24:57 PM3/13/12
to
On Mar 12, 8:30 am, "Anon E. Mouse" <agall...@gmail.com> wrote:
[[Mod. note -- 66 excessively-quoted lines snipped here. -- jt]]
> Amplitude (intensity) is another matter. Standard candles =3D amplitude.
> Amplitude is believed to fall according to 1/Pi*r^2.
>
> Chromatic aberration is another matter and is based on the somewhat
> untested assumption that frequency shifts are proportional to the
> frequency. This is true for lensing, but not yet proven for
> gravitational lensing, or relativity.
>
> regards,
>
> AAG
1) Power of an EM wave is definitely proportional to the SQUARE of the
> Amplitude is believed to fall according to 1/Pi*r^2.
>
> Chromatic aberration is another matter and is based on the somewhat
> untested assumption that frequency shifts are proportional to the
> frequency. This is true for lensing, but not yet proven for
> gravitational lensing, or relativity.
>
> regards,
>
> AAG
amplitude.
I can only make some sense of your posting if you accept we are
talking about power and intensity, not amplitude.
Now to get down to business.
2) If you use the separation of the 2 events relative to the emitter,
you only get the power of the signal relative to the emitter,
which is NOT what we need to know.
Thus the correct distance for detected intensity must be the distance
relative to the detector.
Chalky
Mar 14, 2012, 12:34:39 PM3/14/12
to
On Mar 14, 1:24 am, Chalky <chalkys...@bleachboys.co.uk> wrote:
> Now to get down to business.
>
> 2) If you use the separation of the 2 events relative to the emitter,
> you only get the power of the signal relative to the emitter,
> which is NOT what we need to know.
> Thus the correct distance for detected intensity must be the distance
> relative to the detector.
Equivalently, the "instantaneous" distance the detector actually sees
> Now to get down to business.
>
> 2) If you use the separation of the 2 events relative to the emitter,
> you only get the power of the signal relative to the emitter,
> which is NOT what we need to know.
> Thus the correct distance for detected intensity must be the distance
> relative to the detector.
in flat spacetime, at the point of detection. (This then works for
both SR and GR)
[[Mod. note -- I don't think this works in GR. There are a couple
of problems. First, in GR there may be multiple paths from emitter
to receiver (think "gravitational lensing"). In general you would
need to sum over all the paths. Second, in general there's no good
way to define the global "distance" you want, i.e., there's no good
way to define the "length" of a path.
[The obvious solution, to integrate the proper length
along the path, fails because we're talking about paths
for *light*, so the proper length
(which is the only that that's coordinate-independent)
is zero by definition.
If you want just the spatial length (as you do in SR)
then you run into trouble trying to match up the spatial
coordinates at the different times of emission & reception,
i.e., your results won't be coordinate-independent.]
All in all, for GR I think it may be cleaner to just fall back on
ray-tracing and compare amount-of-solid-angle-subtended-at-emitter
for paths reaching the receiver. For nearly-flat spacetimes this
will approach the inverse-square law as a limiting case.
-- jt]]
Chalky
Mar 16, 2012, 1:00:04 PM3/16/12
to
On Mar 14, 4:34 pm, Chalky <chalkys...@bleachboys.co.uk> wrote:
> On Mar 14, 1:24 am, Chalky <chalkys...@bleachboys.co.uk> wrote:
>
> > Now to get down to business.
>
> > 2) If you use the separation of the 2 events relative to the emitter,
> > you only get the power of the signal relative to the emitter,
> > which is NOT what we need to know.
> > Thus the correct distance for detected intensity must be the distance
> > relative to the detector.
>
> Equivalently, the "instantaneous" distance the detector actually sees
> in flat spacetime, at the point of detection. (This then works for
> both SR and GR)
>
> [[Mod. note -- I don't think this works in GR.
I don't think it even works in SR, if you place a glass lens between
> On Mar 14, 1:24 am, Chalky <chalkys...@bleachboys.co.uk> wrote:
>
> > Now to get down to business.
>
> > 2) If you use the separation of the 2 events relative to the emitter,
> > you only get the power of the signal relative to the emitter,
> > which is NOT what we need to know.
> > Thus the correct distance for detected intensity must be the distance
> > relative to the detector.
>
> Equivalently, the "instantaneous" distance the detector actually sees
> in flat spacetime, at the point of detection. (This then works for
> both SR and GR)
>
> [[Mod. note -- I don't think this works in GR.
emitter and detector.
Perhaps I should have explicitly declared from the outset that I am
looking for independent verification of a maximum simplicity
interpretation of geometrodynamic field theory, on the scale of the
universe. Here maximum simplicity means the simplifying assumptions of
flat space, and homogeneity, as well as isotropy.
My first stab at this (at spf) for GR was to define that distance as
proper distance. This appears to be well defined conceptually, if not
mathematically. However, it is so long since I did SR academically, I
am not even sure what proper distance actually means in that SR
context.
[[Mod. note -- Following Wheeler, "geometrodynamic" is usually taken
as a reference to general relatiity. In general, this means that
space (and spacetime) is neither flat, homogeneous, nor isotropic.
That said... proper distance is well-defined conceptually and
mathematically in both SR and GR as the path integral
$L = \int_{\text{path}} \sqrt{g_{ab} dx^a dx^b} \, d\ell$
This is invariant under coordinate changes.
Unfortunately for present purposes, we're interested in *light*
paths, for which $g_{ab} dx^a dx^b = 0$ by definition, and hence
the proper distance is precisely zero.
If you only care about the spatial part of the metric, then you can
consider the spatial proper distance
$L_x = \int_{\text{path}} \sqrt{g_{ij} dx^i dx^j} \, d\ell$
This is invariant under spatial-coordinate changes, but is *not*
invariant if you change your time coordinate.
-- jt]]
Anon E. Mouse
Mar 16, 2012, 7:32:30 PM3/16/12
to
>
> =A0 =A0 =A0 =A0 [The obvious solution, to integrate the proper length
> =A0 =A0 =A0 =A0 along the path, fails because we're talking about paths
> =A0 =A0 =A0 =A0 for *light*, so the proper length
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (which is the only that that's coordinate=
-independent)
> =A0 =A0 =A0 =A0 is zero by definition.
>
> =A0 =A0 =A0 =A0 If you want just the spatial length (as you do in SR)
> =A0 =A0 =A0 =A0 then you run into trouble trying to match up the spatial
> =A0 =A0 =A0 =A0 coordinates at the different times of emission & receptio=
n,
> =A0 =A0 =A0 =A0 i.e., your results won't be coordinate-independent.]
is very very similar to Newton's original.
As this academic problem seems to be related to a real world problem
connecting the problem with basic theory may be most helpful in terms
of developing a solution.
It is called the inverse square law because the assumption is that the
power of the emitter is uniformly distributed, and therefor, the area
under the curve is a sphere. Well, for practical purposes the 2d area
of the circle given by pi*r*r is good enough for government work." For
a practical problem neglecting pi and just dealing with the r * r
could cause more problems than the timing.
If emission and detection are co-linear and v(emitter) and v(sender)
are very similar, then the gamma's tend to cancel. Making Chalky's
simple solution basically correct.
Technically, measuring frequency shifts are typically much easier than
absolute amplitude measures. If it is assumed the frequency (or
frequency distribution) of the emitter is uniform, then it should be
possible to distinguish which whether the observed change luminosity
is due to distance, or "closing".
Say, there is closing, in that case the observed frequency and
intensity should increase, however, the frequency would change
according to SR and the intensity would change according to the
closing plus the decreased separation. Thus it should be theoretically
possible to compare the values of gamma and lux and solve for an
"absolute" time of flight for the distance from the emitters past
position to the receiver's present.
This would be an extremely subtle measure which may prove impractical
in the real world, meanwhile Chalky's simple solution seems quite
good.
> =A0 =A0 =A0 =A0 [The obvious solution, to integrate the proper length
> =A0 =A0 =A0 =A0 along the path, fails because we're talking about paths
> =A0 =A0 =A0 =A0 for *light*, so the proper length
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (which is the only that that's coordinate=
-independent)
> =A0 =A0 =A0 =A0 is zero by definition.
>
> =A0 =A0 =A0 =A0 If you want just the spatial length (as you do in SR)
> =A0 =A0 =A0 =A0 then you run into trouble trying to match up the spatial
> =A0 =A0 =A0 =A0 coordinates at the different times of emission & receptio=
n,
> =A0 =A0 =A0 =A0 i.e., your results won't be coordinate-independent.]
>
> All in all, for GR I think it may be cleaner to just fall back on
> ray-tracing and compare amount-of-solid-angle-subtended-at-emitter
> for paths reaching the receiver. =A0For nearly-flat spacetimes this
> All in all, for GR I think it may be cleaner to just fall back on
> ray-tracing and compare amount-of-solid-angle-subtended-at-emitter
> will approach the inverse-square law as a limiting case.
> -- jt]]
I agree with the moderators comments here. The geometric argument used
> -- jt]]
is very very similar to Newton's original.
As this academic problem seems to be related to a real world problem
connecting the problem with basic theory may be most helpful in terms
of developing a solution.
It is called the inverse square law because the assumption is that the
power of the emitter is uniformly distributed, and therefor, the area
under the curve is a sphere. Well, for practical purposes the 2d area
of the circle given by pi*r*r is good enough for government work." For
a practical problem neglecting pi and just dealing with the r * r
could cause more problems than the timing.
If emission and detection are co-linear and v(emitter) and v(sender)
are very similar, then the gamma's tend to cancel. Making Chalky's
simple solution basically correct.
Technically, measuring frequency shifts are typically much easier than
absolute amplitude measures. If it is assumed the frequency (or
frequency distribution) of the emitter is uniform, then it should be
possible to distinguish which whether the observed change luminosity
is due to distance, or "closing".
Say, there is closing, in that case the observed frequency and
intensity should increase, however, the frequency would change
according to SR and the intensity would change according to the
closing plus the decreased separation. Thus it should be theoretically
possible to compare the values of gamma and lux and solve for an
"absolute" time of flight for the distance from the emitters past
position to the receiver's present.
This would be an extremely subtle measure which may prove impractical
in the real world, meanwhile Chalky's simple solution seems quite
good.
Chalky
Mar 18, 2012, 7:18:50 AM3/18/12
to
> [[Mod. note -- Following Wheeler, "geometrodynamic" is usually taken
> as a reference to general relatiity. =A0In general, this means that
> space (and spacetime) is neither flat, homogeneous, nor isotropic.
That is why I said:
" a maximum simplicity interpretation"
I am not trying to get a deeper understanding of geometrodynamic field
theory per se.
I am trying to get a deeper understanding of how well that relates to
a more powerfully generalised solution of the relativistic axioms,
based on pregeometric considerations.
Thus far, the answer would seem to be "not very well". By its
insistence on invariance, it rules out the relativity of simultaneity
(as expressed by Einstein), thus invoking the problems you describe
(and several more, as well).
Chalky
Mar 18, 2012, 7:19:49 AM3/18/12
to
On Mar 16, 5:00=A0pm, Chalky <chalkys...@bleachboys.co.uk> wrote:
> On Mar 14, 4:34 pm, Chalky <chalkys...@bleachboys.co.uk> wrote:
>
> > On Mar 14, 1:24 am, Chalky <chalkys...@bleachboys.co.uk> wrote:
>
> > > =A0 Now to get down to business.
> On Mar 14, 4:34 pm, Chalky <chalkys...@bleachboys.co.uk> wrote:
>
> > On Mar 14, 1:24 am, Chalky <chalkys...@bleachboys.co.uk> wrote:
>
>
> > > 2) If you use the separation of the 2 events relative to the emitter,
> > > you only get the power of the signal relative to the =A0 =A0 =A0emitt=
> > > 2) If you use the separation of the 2 events relative to the emitter,
er,
> > > which is NOT what we need to know.
> > > Thus the correct distance for detected intensity must be the distance
> > > relative to the detector.
>
> > Equivalently, the "instantaneous" distance the detector actually sees
> > in flat spacetime, at the point of detection. (This then works for
> > both SR and GR)
>
> > [[Mod. note -- I don't think this works in GR.
>
> I don't think it even works in SR, if you place a glass lens between
> emitter and detector.
>
> Perhaps I should have explicitly declared from the outset that I am
> looking for independent verification of a maximum simplicity
> interpretation of geometrodynamic field theory, on the scale of the
> universe. Here maximum simplicity means the simplifying assumptions of
> flat space, and homogeneity, as well as isotropy.
>
> My first stab at this (at spf) for GR was to define that distance as
> proper distance. This appears to be well defined conceptually, if not
> mathematically. However, it is so long since I did SR academically, I
> am not even sure what proper distance actually means in that SR
> context.
>
> [[Mod. note -- Following Wheeler, "geometrodynamic" is usually taken
> as a reference to general relatiity.
Yes. However, in the present context, I am using it to specifically
> > > which is NOT what we need to know.
> > > Thus the correct distance for detected intensity must be the distance
> > > relative to the detector.
>
> > Equivalently, the "instantaneous" distance the detector actually sees
> > in flat spacetime, at the point of detection. (This then works for
> > both SR and GR)
>
> > [[Mod. note -- I don't think this works in GR.
>
> I don't think it even works in SR, if you place a glass lens between
> emitter and detector.
>
> Perhaps I should have explicitly declared from the outset that I am
> looking for independent verification of a maximum simplicity
> interpretation of geometrodynamic field theory, on the scale of the
> universe. Here maximum simplicity means the simplifying assumptions of
> flat space, and homogeneity, as well as isotropy.
>
> My first stab at this (at spf) for GR was to define that distance as
> proper distance. This appears to be well defined conceptually, if not
> mathematically. However, it is so long since I did SR academically, I
> am not even sure what proper distance actually means in that SR
> context.
>
> [[Mod. note -- Following Wheeler, "geometrodynamic" is usually taken
> as a reference to general relatiity.
mean general relativity as mathematically formulated and interpreted
within the framework of Riemann geometry. This means as opposed to
(and again following Wheeler) the mathematical framework of
pregeometry and logic.
> That said... proper distance is well-defined conceptually and
> mathematically in both SR and GR as the path integral
> This is invariant under coordinate changes.
>
> Unfortunately for present purposes, we're interested in *light*
> paths, for which $g_{ab} dx^a dx^b =3D 0$ by definition, and hence
>
> Unfortunately for present purposes, we're interested in *light*
> the proper distance is precisely zero.
According to e.g.
http://www.physics.fsu.edu/courses/spring98/ast3033/Relativity/GeneralRelat=
ivity.htm
when two events have the same time, that is, when they are
simultaneous, the spatial distance between them is invariant, that is,
measured to be the same by all observers. This distance is called the
proper distance between the two points.
Now, in the situation we are examining, the emission event and the
detection event are simultaneous, relative to the detector.
Consequently, on further reflection, I cannot see your objection to
calling this separation the proper distance between the emission and
detection events.
Chalky
Mar 18, 2012, 9:10:43 AM3/18/12
to
On Mar 18, 11:19=A0am, Chalky <chalkys...@bleachboys.co.uk> wrote:
> According to e.g.http://www.physics.fsu.edu/courses/spring98/ast3033/Rela=
tivity/Genera...
I am thinking about the observed time of the emission event and the
observed time of the detection event. These are simultaneous for the
detector, and for every observer in a straight line behind that
detector, but not for anyone else.
You, on the other hand are quite possibly talking about the geometric
times of these two events, which will be the same for all observers.
However, this then means that the physically observed time difference
between these two events is still different for everybody except for
those covered in the preceding paragraph. The advantage is that
everyone can now agree on something that nobody can actually see.
Have I finally got this right?
> According to e.g.http://www.physics.fsu.edu/courses/spring98/ast3033/Rela=
tivity/Genera...
> ivity.htm
> when two events have the same time, that is, when they are
> simultaneous, the spatial distance between them is invariant, that is,
> measured to be the same by all observers. This distance is called the
> proper distance between the two points.
>
> Now, in the situation we are examining, the emission event and the
> detection event are simultaneous, relative to the detector.
> Consequently, on further reflection, I cannot see your objection to
> calling this separation the proper distance between the emission and
> detection events.
OK I think the penny has probably finally dropped.
> when two events have the same time, that is, when they are
> simultaneous, the spatial distance between them is invariant, that is,
> measured to be the same by all observers. This distance is called the
> proper distance between the two points.
>
> Now, in the situation we are examining, the emission event and the
> detection event are simultaneous, relative to the detector.
> Consequently, on further reflection, I cannot see your objection to
> calling this separation the proper distance between the emission and
> detection events.
I am thinking about the observed time of the emission event and the
observed time of the detection event. These are simultaneous for the
detector, and for every observer in a straight line behind that
detector, but not for anyone else.
You, on the other hand are quite possibly talking about the geometric
times of these two events, which will be the same for all observers.
However, this then means that the physically observed time difference
between these two events is still different for everybody except for
those covered in the preceding paragraph. The advantage is that
everyone can now agree on something that nobody can actually see.
Have I finally got this right?
Chalky
Mar 18, 2012, 5:03:24 PM3/18/12
to
On Mar 16, 11:32 pm, "Anon E. Mouse" <agall...@gmail.com> wrote:
> If emission and detection are co-linear and v(emitter) and v(sender)
> are very similar, then the gamma's tend to cancel. Making Chalky's
> simple solution basically correct.
I don't agree that the velocities of the emitter and detector need to
> If emission and detection are co-linear and v(emitter) and v(sender)
> are very similar, then the gamma's tend to cancel. Making Chalky's
> simple solution basically correct.
be very similar.
> in the real world, meanwhile Chalky's simple solution seems quite
> good.
![Jonathan Thornburg [remove -animal to reply]'s profile photo](https://lh3.googleusercontent.com/a/default-user=s40-c)
Jonathan Thornburg [remove -animal to reply]
Mar 18, 2012, 6:32:35 PM3/18/12
to
Chalky <chalk...@bleachboys.co.uk> wrote:
> According to e.g.
> http://www.physics.fsu.edu/courses/spring98/ast3033/Relativity/GeneralRelat=
> ivity.htm
> when two events have the same time, that is, when they are
> simultaneous, the spatial distance between them is invariant, that is,
> measured to be the same by all observers. This distance is called the
> proper distance between the two points.
The problem is with that phrase "have the same time": in general
> According to e.g.
> http://www.physics.fsu.edu/courses/spring98/ast3033/Relativity/GeneralRelat=
> ivity.htm
> when two events have the same time, that is, when they are
> simultaneous, the spatial distance between them is invariant, that is,
> measured to be the same by all observers. This distance is called the
> proper distance between the two points.
different observers (coordinate systems) disagree about whether or
not two events have the same time.
The "proper distance" you refer to is only invariant under SPATIAL
coordinate transformations, i.e., coordinate transformations which
leave the time coordinate unchanged.
> Now, in the situation we are examining, the emission event and the
> detection event are simultaneous, relative to the detector.
event is on the emission event's future light cone), but not simultaneous
(they do not have the same time coordinate, at least not for the usual
3+1 notion of "time coordinate")
"simultaneous" = have the same time coordinate
"null-separated" = there's a null geodesic (light path) from one event
to the other
--
-- "Jonathan Thornburg [remove -animal to reply]" <jth...@astro.indiana-zebra.edu>
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam
Chalky
Mar 20, 2012, 4:21:32 AM3/20/12
to
On Mar 18, 10:32=A0pm, "Jonathan Thornburg [remove -animal to reply]"
<jth...@astro.indiana-zebra.edu> wrote:
> >http://www.physics.fsu.edu/courses/spring98/ast3033/Relativity/Genera...
redshift in SR & GR" (not yet published here, at time of writing),
I specifically qualify everything relevant by saying "relative to an
inertial observer in a general relativistic universe"
> The "proper distance" you refer to is only invariant under SPATIAL
> coordinate transformations, i.e., coordinate transformations which
> leave the time coordinate unchanged.
Yes this is proper distance =3D comoving radial distance, for the
observer now
> > Now, in the situation we are examining, the emission event and the
> > detection event are simultaneous, relative to the detector.
>
> The emission & detection events are null-separated (the detection
> event is on the emission event's future light cone), but not simultaneous
> (they do not have the same time coordinate, at least not for the usual
> 3+1 notion of "time coordinate")
Yes, I would go along with that.
> "simultaneous" =3D have the same time coordinate
But relative to whom? What I mean is relative to said observer, and
nothing else.
I assume you are referring to cosmological time which I tend to avoid,
because, imo, it introduces a level of rigidity which is not actually
real.
> "null-separated" =3D there's a null geodesic (light path) from one event
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0to the other
Yes, this is more precise, without doubt
<jth...@astro.indiana-zebra.edu> wrote:
> >http://www.physics.fsu.edu/courses/spring98/ast3033/Relativity/Genera...
> > ivity.htm
> > when two events have the same time, that is, when they are
> > simultaneous, the spatial distance between them is invariant, that is,
> > measured to be the same by all observers. This distance is called the
> > proper distance between the two points.
>
> The problem is with that phrase "have the same time": in general
> different observers (coordinate systems) disagree about whether or
> not two events have the same time.
Yes. This is why in my last submission "Luminosity distance and
> > when two events have the same time, that is, when they are
> > simultaneous, the spatial distance between them is invariant, that is,
> > measured to be the same by all observers. This distance is called the
> > proper distance between the two points.
>
> The problem is with that phrase "have the same time": in general
> different observers (coordinate systems) disagree about whether or
> not two events have the same time.
redshift in SR & GR" (not yet published here, at time of writing),
I specifically qualify everything relevant by saying "relative to an
inertial observer in a general relativistic universe"
> The "proper distance" you refer to is only invariant under SPATIAL
> coordinate transformations, i.e., coordinate transformations which
> leave the time coordinate unchanged.
observer now
> > Now, in the situation we are examining, the emission event and the
> > detection event are simultaneous, relative to the detector.
>
> The emission & detection events are null-separated (the detection
> event is on the emission event's future light cone), but not simultaneous
> (they do not have the same time coordinate, at least not for the usual
> 3+1 notion of "time coordinate")
> "simultaneous" =3D have the same time coordinate
But relative to whom? What I mean is relative to said observer, and
nothing else.
I assume you are referring to cosmological time which I tend to avoid,
because, imo, it introduces a level of rigidity which is not actually
real.
> "null-separated" =3D there's a null geodesic (light path) from one event
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0to the other
Yes, this is more precise, without doubt
Anon E. Mouse
Mar 20, 2012, 8:28:42 PM3/20/12
to
apparent increase in luminosity above the appropriate square law for
that distance. Red-shift reduces apparent luminosity.
At least for closing caused by the motion of the receiver. While
frequency can not be used to distinguish between the relative motion
of either party because the gammas are identical potentially
luminosity can distinguish. This is why standard candle calculations
work.
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.
Now that I am satisfied that there is evidence that chromatic
aberration is consistent for both refraction and gravitational
lensing, I am even more certain that this can realistically be used to
determine proper distance from a single stellar source, and not just
on a statistical basis as is presently done.
The total problem has three variables, gamma as determined by red
shift, color temperature as a measure of chromatic aberration, and
luminosity.
These are all readily determinable for many sources, especially the
interesting ones such as binaries. Three equations with three
variables that vary according to different relations in different
orders should yield a convergent solution.
Other issues:
There are known issues with spectral analysis of stars that might make
a direct measure of proper distance from the greater degree of
aberration for red spectra and blue alone. Additionally, I may not be
using color temperature in exactly the same sense an astronomer would.
Still, as I consider the issues I grow more and more certain that a
direct measure of proper distance (and therefor absolute motions)
should be technically possible using existing technology.
The correct resolution of the issue I raise in another discussion
about squared vs cubed must be correctly resolved in order for the
calculations I propose to reach convergence. I have spoken with
astronomers who attempted to do what I am and have been for some time
now proposing and they said, "I tried, and it just didn't work." When
I asked them if they knew why they suggested that if they know what
was wrong, they probably could have fixed it. I had to agree.
I think applying the square law instead of the cube law could be the
reason that there has to date been no solution to what seems on
surface to be a solvable problem.
Sincerely,
AAG
Chalky
Mar 20, 2012, 8:32:06 PM3/20/12
to
Luminosity Distance & Redshift in SR & GR
In the light of constructive criticism of my original posting on this
subject, both at spr and spf, I would like to now redraft that
posting in a way that is, hopefully, more accurate and more
unambiguous, as well as rendering the associated question, itself more
clear. Hence:
Relative to an inertial observer, and within the context of SR:
1{s} The redshift of an emission event depends on the recession
velocity of the emitter at the time of emission, relative to that
inertial detector.
2{s} This is observed after a time delay of del t where del t = d/
c , and d is the spatial proper distance between the emission event
and the observer at the time of observation. ( This distance is also
equal to and equivalent to the distance of the emission event that
the observer actually sees, at the time of detection.)
3{s} The luminosity distance of the emission event is thus observed,
at the time of detection, to be a function of both the Doppler shift
at the time of emission, and the distance of d = c del t.
4{s} Thus the luminosity distance of the emission event is
proportional to the light travel delay between emission and detection.
However, relative to an inertial observer in a general relativistic
universe, then, provided there is no peculiar velocity difference
between the emission event and the detection event:
1{g} The cosmological redshift of that emission event depends on the
time difference between the emission event and the detection event
(del t).
2{g} This time difference is associated with a spatial separation
between emission event and detection event, of d = c(del t)
3{g} The luminosity distance of the emission event is now observed,
at the time of detection, to be a function of both the cosmological
redshift and the spatial proper distance (d2) of the emission event,
at the time of detection.
4{g} Thus the luminosity distance of the emission event is
proportional to the distance d2, which is always greater than d,
unless emission event and detection event are coincident and
simultaneous.
The following fundamental differences thus obtain between the SR and
GR situations.
1) SR Redshift depends on peculiar velocity difference.
Cosmological redshift does not. Instead it depends on time
difference between emission and detection events.
2) SR luminosity distance is proportional to the distance d = c del
t. Cosmological luminosity distance is not. Instead it is
proportional to the spatial proper distance of the emission event , at
the time of detection.
Consequently, does anyone have any constructive criticism to make
about
a) The veracity of the above statements
b) The clarity of the above statements
c) The disambiguation within final statements 1 and 2
[ Speak now, or forever hold your peace. {:-) ]
Thanks also to all, for your patience and comments thus far, and
particularly special thanks to Jonathan Thornburg.
Chalky
N.B. The spatial proper distance (d2) of the emission event, at the
time of detection, is dependent on the general relativistic solution
chosen and, in the case of geometrodynamic field theory and Friedmann
cosmologies, also dependent on retrofit adjustment of its various free
parameters, for optimal fit to observational evidence.
Consequently, for maximum generality, it is preferable to leave the
calculation of d2 unspecified, until after the theory is chosen.
In the light of constructive criticism of my original posting on this
subject, both at spr and spf, I would like to now redraft that
posting in a way that is, hopefully, more accurate and more
unambiguous, as well as rendering the associated question, itself more
clear. Hence:
Relative to an inertial observer, and within the context of SR:
1{s} The redshift of an emission event depends on the recession
velocity of the emitter at the time of emission, relative to that
inertial detector.
2{s} This is observed after a time delay of del t where del t = d/
c , and d is the spatial proper distance between the emission event
and the observer at the time of observation. ( This distance is also
equal to and equivalent to the distance of the emission event that
the observer actually sees, at the time of detection.)
3{s} The luminosity distance of the emission event is thus observed,
at the time of detection, to be a function of both the Doppler shift
at the time of emission, and the distance of d = c del t.
4{s} Thus the luminosity distance of the emission event is
proportional to the light travel delay between emission and detection.
However, relative to an inertial observer in a general relativistic
universe, then, provided there is no peculiar velocity difference
between the emission event and the detection event:
1{g} The cosmological redshift of that emission event depends on the
time difference between the emission event and the detection event
(del t).
2{g} This time difference is associated with a spatial separation
between emission event and detection event, of d = c(del t)
3{g} The luminosity distance of the emission event is now observed,
at the time of detection, to be a function of both the cosmological
redshift and the spatial proper distance (d2) of the emission event,
at the time of detection.
4{g} Thus the luminosity distance of the emission event is
proportional to the distance d2, which is always greater than d,
unless emission event and detection event are coincident and
simultaneous.
The following fundamental differences thus obtain between the SR and
GR situations.
1) SR Redshift depends on peculiar velocity difference.
Cosmological redshift does not. Instead it depends on time
difference between emission and detection events.
2) SR luminosity distance is proportional to the distance d = c del
t. Cosmological luminosity distance is not. Instead it is
proportional to the spatial proper distance of the emission event , at
the time of detection.
Consequently, does anyone have any constructive criticism to make
about
a) The veracity of the above statements
b) The clarity of the above statements
c) The disambiguation within final statements 1 and 2
[ Speak now, or forever hold your peace. {:-) ]
Thanks also to all, for your patience and comments thus far, and
particularly special thanks to Jonathan Thornburg.
Chalky
N.B. The spatial proper distance (d2) of the emission event, at the
time of detection, is dependent on the general relativistic solution
chosen and, in the case of geometrodynamic field theory and Friedmann
cosmologies, also dependent on retrofit adjustment of its various free
parameters, for optimal fit to observational evidence.
Consequently, for maximum generality, it is preferable to leave the
calculation of d2 unspecified, until after the theory is chosen.
Richard D. Saam
Mar 20, 2012, 8:35:12 PM3/20/12
to
On 3/18/12 4:03 PM, Chalky wrote:
> On Mar 16, 11:32 pm, "Anon E. Mouse"<agall...@gmail.com> wrote:
>
>> If emission and detection are co-linear and v(emitter) and v(sender)
>> are very similar, then the gamma's tend to cancel. Making Chalky's
>> simple solution basically correct.
>
> I don't agree that the velocities of the emitter and detector need to
> be very similar.
The following contribution by Steve Carlip may be of interest to this
> On Mar 16, 11:32 pm, "Anon E. Mouse"<agall...@gmail.com> wrote:
>
>> If emission and detection are co-linear and v(emitter) and v(sender)
>> are very similar, then the gamma's tend to cancel. Making Chalky's
>> simple solution basically correct.
>
> I don't agree that the velocities of the emitter and detector need to
> be very similar.
discussion:
http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
"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. The net
result is that the effect of propagation delay is almost exactly
cancelled, and general relativity very nearly reproduces the newtonian
result."
"the cancellation
(for gravitationally and electromagnetically attracted objects)
is nearly exact only for constant velocities"
Richard D. Saam
[[Mod. note -- Carlip expands on this further in
S. Carlip
"Aberration and the speed of gravity"
Physics Letters A 267 (2000) 8187
http://dx.doi.org/10.1016/S0375-9601(00)00101-8
open-access preprint arXiv:gr-qc/9909087
-- jt]]
Phillip Helbig---undress to reply
Mar 20, 2012, 8:35:36 PM3/20/12
to
In article
<8df418ab-46cd-4467...@v2g2000vbx.googlegroups.com>,
it is). The "radar method" explicitly takes into account the time of
propagation of the radar signal, and the change in proper distance
during this time.
<8df418ab-46cd-4467...@v2g2000vbx.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> Can anyone here give me a clear and unambiguous answer to the
> following very basic question, in the context of special relativity:
>
> Relative to the inertial observer who considers himself at rest, is
> the observed intensity of a signal from a distant EM emitter,
> inversely proportional to the square of the "instantaneous" ie.
> "geometric" distance of the emitter:
>
> (A) At the time of emission
> (B) At the time of detection, or
> (C) Neither of the above
>
> By "instantaneous" ie. "geometric" distance, I mean the distance of
> the emitter at the time of emission, which could, in principle, be
> determined by the radar method, if the time of emission is known in
> advance.
I think you mean the proper distance at the time in question (whichever
> Can anyone here give me a clear and unambiguous answer to the
> following very basic question, in the context of special relativity:
>
> Relative to the inertial observer who considers himself at rest, is
> the observed intensity of a signal from a distant EM emitter,
> inversely proportional to the square of the "instantaneous" ie.
> "geometric" distance of the emitter:
>
> (A) At the time of emission
> (B) At the time of detection, or
> (C) Neither of the above
>
> By "instantaneous" ie. "geometric" distance, I mean the distance of
> the emitter at the time of emission, which could, in principle, be
> determined by the radar method, if the time of emission is known in
> advance.
it is). The "radar method" explicitly takes into account the time of
propagation of the radar signal, and the change in proper distance
during this time.
Chalky
Mar 21, 2012, 12:44:39 PM3/21/12
to
On Mar 21, 12:35 am, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> In article
> <8df418ab-46cd-4467-a654-0b0ce035f...@v2g2000vbx.googlegroups.com>,
Yes, which is why I used it. It does not depend on theory.
Also yes in the sense that proper distance = co-moving radial distance
for observers now.
No, or debatable, in the sense that proper distance in the past can be
realistically computed from classical geometrodynamic field theory
(based on what we observe now).
Without going into details of my own derivation, there are reasons for
concluding that classical theory is insufficiently accurate to be
reliably extrapolated backwards in time, to the start of the universe.
Proof? Big bang singularity problem.
undress to reply) wrote:
> In article
> <8df418ab-46cd-4467-a654-0b0ce035f...@v2g2000vbx.googlegroups.com>,
Also yes in the sense that proper distance = co-moving radial distance
for observers now.
No, or debatable, in the sense that proper distance in the past can be
realistically computed from classical geometrodynamic field theory
(based on what we observe now).
Without going into details of my own derivation, there are reasons for
concluding that classical theory is insufficiently accurate to be
reliably extrapolated backwards in time, to the start of the universe.
Proof? Big bang singularity problem.
Chalky
Mar 21, 2012, 12:45:19 PM3/21/12
to
On Mar 21, 12:35 am, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> In article
> <8df418ab-46cd-4467-a654-0b0ce035f...@v2g2000vbx.googlegroups.com>,
>
>
>
>
>
>
>
>
>
undress to reply) wrote:
> In article
> <8df418ab-46cd-4467-a654-0b0ce035f...@v2g2000vbx.googlegroups.com>,
>
>
>
>
>
>
>
>
>
theory independent within the constraints of the relativistic axioms
and their logical consequences.
I also might be getting ahead of myself, if your response is
specifically directed towards SR, and SR only.
However, one respondent at spf was arguing with me about the SR
universe. There is, of course, no such thing.
Phillip Helbig---undress to reply
Mar 21, 2012, 12:46:34 PM3/21/12
to
In article
<10e87080-1c1b-466a...@p13g2000yqd.googlegroups.com>,
evolution, for example the one by Kippenhahn and Weigert) why stars have
the colours, sizes and masses they do. It has nothing to do with
chromatic aberration.
<10e87080-1c1b-466a...@p13g2000yqd.googlegroups.com>,
"Anon E. Mouse" <agal...@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
> 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.
evolution, for example the one by Kippenhahn and Weigert) why stars have
the colours, sizes and masses they do. It has nothing to do with
chromatic aberration.
Phillip Helbig---undress to reply
Mar 21, 2012, 12:47:00 PM3/21/12
to
In article
<c42b9285-949a-460e...@p6g2000yqi.googlegroups.com>,
to that at the time the light was emitted. Check out any introductory
cosmology textbook.
<c42b9285-949a-460e...@p6g2000yqi.googlegroups.com>,
Chalky <chalk...@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
> 1{g} The cosmological redshift of that emission event depends on the
> time difference between the emission event and the detection event
> (del t).
to that at the time the light was emitted. Check out any introductory
cosmology textbook.
Chalky
Mar 21, 2012, 12:48:39 PM3/21/12
to
On Mar 21, 12:35 am, "Richard D. Saam" <rds...@att.net> wrote:
> On 3/18/12 4:03 PM, Chalky wrote:> On Mar 16, 11:32 pm, "Anon E. Mouse"<agall...@gmail.com> wrote:
>
> >> If emission and detection are co-linear and v(emitter) and v(sender)
> >> are very similar, then the gamma's tend to cancel. Making Chalky's
> >> simple solution basically correct.
>
> > I don't agree that the velocities of the emitter and detector need to
> > be very similar.
>
> The following contribution by Steve Carlip may be of interest to this
> discussion:http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
>
> "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?
I am not sure that that question marked lack of accuracy is
> On 3/18/12 4:03 PM, Chalky wrote:> On Mar 16, 11:32 pm, "Anon E. Mouse"<agall...@gmail.com> wrote:
>
> >> If emission and detection are co-linear and v(emitter) and v(sender)
> >> are very similar, then the gamma's tend to cancel. Making Chalky's
> >> simple solution basically correct.
>
> > I don't agree that the velocities of the emitter and detector need to
> > be very similar.
>
> The following contribution by Steve Carlip may be of interest to this
> discussion:http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
>
> "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?
necessarily true. Carlip shows it IS central to v^3/c^3
The first suggestion that it is not true to even higher accuracy is
the v^5 / c^5 dependency for gravitational wave radiation.
> and that it depends on velocity as well as position. The net
> result is that the effect of propagation delay is almost exactly
> cancelled, and general relativity very nearly reproduces the newtonian
> result."
> "the cancellation
> (for gravitationally and electromagnetically attracted objects)
> is nearly exact only for constant velocities"
recent years, and not noticed it, so could you point out which
paragraph?
> [[Mod. note -- Carlip expands on this further in
> S. Carlip
> "Aberration and the speed of gravity"
> http://dx.doi.org/10.1016/S0375-9601(00)00101-8
> open-access preprint arXiv:gr-qc/9909087
> -- jt]]
Quite so.
> open-access preprint arXiv:gr-qc/9909087
> -- jt]]
Chalky
Mar 21, 2012, 5:48:28 PM3/21/12
to
On Mar 21, 4:47 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
as does the redshift
undress to reply) wrote:
> In article
> <c42b9285-949a-460e-8be8-ce3f1d068...@p6g2000yqi.googlegroups.com>,
> In article
>
> 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,
> 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.
as does the redshift
Anon E. Mouse
Mar 21, 2012, 5:48:49 PM3/21/12
to
On Mar 21, 12:46 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
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.
AAG
undress to reply) wrote:
> In article
> <10e87080-1c1b-466a-a72f-d980b3157...@p13g2000yqd.googlegroups.com>,
> In article
> "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
>
> > 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
> 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
> chromatic aberration.
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.
AAG
Chalky
Mar 21, 2012, 5:49:14 PM3/21/12
to
On Mar 21, 4:47 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
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 :-).
From your moderator's comment at
http://groups.google.com/group/sci.physics.research/browse_frm/thread/ca051556c258891c#
that would seem to indicate that you confirm:
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.
undress to reply) wrote:
> In article
> 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
>
> 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.
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.
natural philosophical questions, I would hazard to suggest :-).
From your moderator's comment at
http://groups.google.com/group/sci.physics.research/browse_frm/thread/ca051556c258891c#
that would seem to indicate that you confirm:
2{g} This time difference is associated with a spatial separation
between emission event and detection event, of d = c(del t)
(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.
Chalky
Mar 22, 2012, 5:24:13 PM3/22/12
to
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.
[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
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.
Anon E. Mouse
Mar 23, 2012, 3:38:28 PM3/23/12
to
> Ergo, you are correct.
>
> 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
>
> However, I don't actually see what this has to do, exactly, with the
> discussion here.
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.
AAG
Chalky
Mar 23, 2012, 3:38:50 PM3/23/12
to
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>,
>
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
> > 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 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.
Richard D. Saam
Mar 24, 2012, 11:01:05 AM3/24/12
to
On 3/21/12 11:48 AM, Chalky wrote:
>> "the cancellation
>> (for gravitationally and electromagnetically attracted objects)
>> is nearly exact only for constant velocities"
>
> Where did you read that? I have read this article a few times over
> recent years, and not noticed it, so could you point out which
> paragraph?
Paragraph three
>
>> [[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
>> [[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]]
>
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.
Richard D. Saam
Chalky
Mar 24, 2012, 2:10:49 PM3/24/12
to
> The following contribution by Steve Carlip may be of interest to this
> discussion:http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
>
> "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
> discussion:http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
>
> "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.
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.
> [[Mod. note -- Carlip expands on this further in
> S. Carlip
> "Aberration and the speed of gravity"
> -- jt]]
Chalky
Anon E. Mouse
Mar 24, 2012, 2:11:14 PM3/24/12
to
> 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.
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.
AAG
Phillip Helbig---undress to reply
Mar 24, 2012, 2:11:34 PM3/24/12
to
In article
<6aa098bf-4fe1-48e8...@j14g2000vbc.googlegroups.com>,
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.
<6aa098bf-4fe1-48e8...@j14g2000vbc.googlegroups.com>,
Chalky <chalk...@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>,
> >
> 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.
>
> > > 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.
> as does the redshift
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.
Phillip Helbig---undress to reply
Mar 24, 2012, 2:12:02 PM3/24/12
to
In article
<42dc322b-f5be-4eae...@eb6g2000vbb.googlegroups.com>,
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.
<42dc322b-f5be-4eae...@eb6g2000vbb.googlegroups.com>,
Chalky <chalk...@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.
>
> 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.)
>
> 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.
>
> > cosmology textbook.
>
> Hardly the most appropriate place to look for profound answers to deep
> natural philosophical questions, I would hazard to suggest :-).
>
> From your moderator's comment at
> http://groups.google.com/group/sci.physics.research/browse_frm/thread/ca051556c258891c#
> that would seem to indicate that you confirm:
>
> 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.
> natural philosophical questions, I would hazard to suggest :-).
>
> From your moderator's comment at
> http://groups.google.com/group/sci.physics.research/browse_frm/thread/ca051556c258891c#
> that would seem to indicate that you confirm:
>
> 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.
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.
Phillip Helbig---undress to reply
Mar 24, 2012, 2:15:12 PM3/24/12
to
In article
<09cd403d-aa94-41ff...@do4g2000vbb.googlegroups.com>,
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.
<09cd403d-aa94-41ff...@do4g2000vbb.googlegroups.com>,
Chalky <chalk...@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
> Einstein said that light cannot bend without a change in velocity.
> Rainbow says that velocity change is frequency dependent.
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.
Phillip Helbig---undress to reply
Mar 24, 2012, 2:15:41 PM3/24/12
to
In article
<93244218-8d5e-45e3...@em9g2000vbb.googlegroups.com>,
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.
<93244218-8d5e-45e3...@em9g2000vbb.googlegroups.com>,
> 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,
> There typically are well
> defined absorbtion lines, but these are assumed to be from
> interstellar gasses and may not be representative of the source.
star itself.
Phillip Helbig---undress to reply
Mar 24, 2012, 2:18:10 PM3/24/12
to
In article
<7de9082f-2757-4258...@hs8g2000vbb.googlegroups.com>,
> 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 ).
<7de9082f-2757-4258...@hs8g2000vbb.googlegroups.com>,
Chalky <chalk...@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.
>
> > > 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.
> 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 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 ).
Chalky
Mar 27, 2012, 4:52:48 PM3/27/12
to
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.
> > 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.
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.
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)
Chalky
Mar 28, 2012, 11:18:05 PM3/28/12
to
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.
> > 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
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.
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.
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
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)
Anon E. Mouse
Apr 1, 2012, 6:50:19 AM4/1/12
to
On Mar 24, 2:15 pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
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.
AAG
undress to reply) wrote:
> In article
> <09cd403d-aa94-41ff-ab5b-4dbf38783...@do4g2000vbb.googlegroups.com>,
> In article
>
> 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=
> 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
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
> 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.
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.
AAG
Phillip Helbig---undress to reply
Apr 1, 2012, 11:38:56 AM4/1/12
to
In article
<88bc588a-92f5-46a1...@t16g2000yqt.googlegroups.com>,
> 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?
<88bc588a-92f5-46a1...@t16g2000yqt.googlegroups.com>,
> > 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.
>
> > 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?
> 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.
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.
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.
> 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.
Do you think any of them indicate the effect you claim?
Tom Roberts
Apr 1, 2012, 12:39:13 PM4/1/12
to
On 4/1/12 4/1/12 5:50 AM, Anon E. Mouse wrote:
> I am aware of the debate within NIST about the frequency independence
> of c.
Really? References please.
> I am aware of the debate within NIST about the frequency independence
> of c.
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.
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.
> 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.
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.
> You state the opinion that gravitational lensing is achromatic as if
> that opinion is an established fact.
definitive measurements that contradict this. References, Please.
Tom Roberts
Norbert Dragon
Apr 1, 2012, 5:26:21 PM4/1/12
to
* Anon E. Mouse schreibt:
> 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?
--
Superstition brings bad luck.
www.itp.uni-hannover.de/~dragon
> 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.
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?
--
Superstition brings bad luck.
www.itp.uni-hannover.de/~dragon
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