Doppler redshift observed using parabolic reflector telescopes is an aberration, light with an angle of incidence produces parabolic caustic curves.

The majority of Light from a star or galaxy is not parallel or 'effectively parallel'.
While it is true that some light from a distance object is parallel, the amount of parallel light collected is the same as the diameter of the reflector. For a 1 meter reflector, only a 1 meter sample of the galaxy is being received as parallel light. It would be extremely difficult so isolate the small proportion of parallel light from the high proportion of incident light.

For similar sized objects:-
Angle of incidence is proportional to distance.
The caustic curve is proportional to angle of incidence.
Length of line produced by the intersection of the caustic curve and x=0 for the parabolic curve (x^2)/4 is directly proportional to the length of the spectrum observed.
The Collimating lens does not produce parallel light when incoming light has an angle of incidence.
All parabolic and spherical reflectors are designed using the (x^2)/4 parabolic curve, the aberration is constant no matter what the diameter of the reflector or the focal length.


The refraction of light to form a spectra, put simply, amplifies the divergent light produced by the caustic curve intersection with x=0.

As the parabolic curve (x^2)/4 is the function for parallel light, a decrease in the angle of incidence shifts all the light towards the ideal focal point of the parabolic curve. That is to say, parallel light will focus light to a point when reflected from the parabolic curve, closer objects focus to a series of points which form a line due to the caustic curve, which when intersected with x=0 produces a line with a length that increases as the distance to the object decreases.
Parallel light reflected from the parabolic curve to a single point, collimated and refracted, produces a spectra directly proportional to the refractive index of the instrument used. An ideal spectra.
Light that is not parallel, light with an angle of incidence, produces divergent light when any attempt is made to collimate it using an instrument designed for parallel light.
Refracted divergent light will produce a longer spectra, or more correctly a spectra longer than the ideal spectra.
The closer the object, the greater the angle of incidence, the greater the divergence, and the longer the spectra will be.
The distance, the angle of incidence, the caustic curve, the length of the intersection of the caustic curve with x=0, the divergent 'collimated' light and the refracted spectra are all proportional to each other.
Since red light is refracted less than blue light any absorption lines towards the blue end of the spectrum will be shifted closer or further from the ideal spectra depending on the angle of incidence.

The notion of an increase in redshift, proportional to an increase in distance, is an inverted logic.
There is an increase in blueshift the closer an object is, which is proportional to the angle of incidence and the resulting parabolic caustic curve.

The length of line produced by the intersection of the caustic curve and x=0 for the parabolic curve (x^2)/4 is extremely small, it is only when it is magnified using refraction that it is noticeable as a scaling of the spectra.

Do you have any citations for anything you've said, or is it just 'logic'.

Your whole argument appears to hinge on the incident light not being effectively parallel. Why in the world would you assume that light from a distant galaxy would be anything other than essentially parallel? For an earth based telescope the atmosphere will cause some minor scattering of the light but that will be revealed as aberations in the image, not a shift in the wavelength. Plus whether the galaxy is 1 million ly away or 10 billion ly away the scatter would be identical. No to mention there will be no scatter in space based telescopes at all.

No citations, it's just word salad :)
It's really just something to think about.

Who mentioned scattering?
I'm taking about angles so small they are difficult to measure, there's no scattering, unless you want to mention the scattering of blue light over distance and the reduction in the range of spectra that can be produced, but that's for another time.
If your just going to ignore the angles then you might as well ignore the redshift.
Next you'll be telling me that the expansion of the universe causes light to become parallel.

I'm taking about angles so small they are difficult to measure, there's no scattering, unless you want to mention the scattering of blue light over distance and the reduction in the range of spectra that can be produced, but that's for another time.
If your just going to ignore the angles then you might as well ignore the redshift.
Next you'll be telling me that the expansion of the universe causes light to become parallel.

You aren't really saying that light from a source 1 billion light years away has a red shift due to the deviation of the light rays from the parallel as measured in a 1 meter parabolic mirror?

If this is what you are saying then please by all means show the math that supports it!

Ok, take a galaxy 1 million light years away, and another 2 million light years away, in your telescope the galaxy further away appears smaller... why?
Your getting less light?
The 'parallel' light somehow magically knows it's suppose to make the galaxy further away appear smaller?
According to you they should be the same size, since after all the light is parallel.
Angle of what?

Your going to use angle of incidence to explain the size difference, yet ignore the fact that angle of incidence produces parabolic caustic curves, something known since before newtons day.

Did Hubble even mention the possibility of the redshift being something to do with the optics?
Is it worth investigating or do we just ignore it?

Is it worth investigating...?

No, because you got it wrong.

At those distances, the only light actually reaching us is parallel.
Any light that wasn't would miss us flat out. That telescope isn't the size of Uranus, you know.

Only one question.
What happens to the ultraviolet radiation? :D

At those distances, the only light actually reaching us is parallel.

LOL - I knew when I posted this that the majority of the replies would be exactly what you wrote. Did you get that answer from the wiki?

Light from a galaxy, 10,000 light years across, radiating light in all directions, is parallel when it reaches us..... and remains parallel billions of light years later, so when does this light magically become parallel, at the source?

Don't worry about it, according to your average physics book your perfectly correct, parabolic caustic curves are a complex subject that are still under investigation using huge supercomputers that have more intellegence than your average physics student. :D

@Emil - at what point?
Same thing applies to radio waves......

when does this light magically become parallel, at the source?


It doesn't. Only the parallel light reaches us.

Light from a galaxy, 10,000 light years across, radiating light in all directions, is parallel when it reaches us

From a source 10,000 light years across, 5 billion light years away, the only light which will actually intersect the mirror of the telescope will be so close to parallel, that the difference will be indistinguishable.

@Emil - at what point?
Same thing applies to radio waves......
In your opinion, how accurate is this: http://upload.wikimedia.org/wikipedia/commons/thumb/e/e4/Redshift_blueshift.svg/220px-Redshift_blueshift.svg.png , for "white light" ?
What is "white light", which is shifted to the red or blue?

From a source 10,000 light years across, 5 billion light years away, the only light which will actually intersect the mirror of the telescope will be so close to parallel, that the difference will be indistinguishable.

So close to parallel, but not actually parallel, optically (to the eye and photographic equipment) the difference is indistinguishable, angular resolution, circles of confusion... the difference in angle of incidence between two objects of similar size at different distances is practically unmeasurable, but it still exists and can't simply be discounted, it has to be accounted for.
What happens when you split up the light from two objects of the same size placed at different distances, the closer one produces a larger spectra, why?

@Emil, yes I understand what doppler shift is, I'm not saying that doppler shift doesn't exist, I for one would like to know whether the current observed redshift is real or a 'phantom of the optics'.
Given the difference in size of the angles, it has been, until relatively recently, all but impossible to even attempt a closer examination, the computational errors would have been too large.
To answer the question, all frequencies (including light) are shifted, it is easier to detect the shift in the blue end of the visible spectrum, assuming the blue end of the spectrum hasn't been scattered by the time it reaches the instrument.

So close to parallel, but not actually parallel, optically (to the eye and photographic equipment) the difference is indistinguishable, angular resolution, circles of confusion... the difference in angle of incidence between two objects of similar size at different distances is practically unmeasurable, but it still exists and can't simply be discounted, it has to be accounted for.
What happens when you split up the light from two objects of the same size placed at different distances, the closer one produces a larger spectra, why?

And... the backpeddling begins...

@kaduseus,


I think you did not understand me.


Composition of white light: http://images.tutorvista.com/content/dispersion/white-light-dispersion.jpeg http://s1.hubimg.com/u/2645108_f260.jpg

So white light is composed of: Red, Orange, Yellov, Green, Blue, Indigo, Violet.

Due to the Doppler effect, all this frequencies are shifted.

Red shifted to Infrared.
Orange shifted to Red.
Yellow shifted to Orange.
Green shifted to Yellov.
Blue shifted to Green.
Indigo shifted to Blue.
Violet shifted to Indigo.
Ultraviolet shifted to Violet.

And finaly we have: Red, Orange, Yellov, Green, Blue, Indigo, Violet.
But this is white light.

So how the red shift occurs?

What we actually see shifted are the spectral absorbtion lines.

@Emil
Oh I diffracted when I should have refracted in the thread start. Ah well, we all have off days.

Anyway, in doppler shift the wavelengths get longer or shorter depending on the direction of travel in relation to the observer.
Light at certain frequencies emitted from a star, produced by chemicals such as hydrogen, emission lines, will have also lengthened in their wavelength.
When the white light, in which all wavelengths have lengthened, from an object traveling away from us is REFRACTED, the signatures of certain emission lines will be seen to have shifted into the red end of the spectrum.
Since ALL light is shifted, and white light, composed of all frequencies, is received, the length of the spectra from any object should be the same length as any other spectra from any other star. Since they aren't, you get blue stars and red stars, you go by the absorption lines.
Now, if the light is not parallel, but divergent, even a tiniest little bit, when refracted, the length of the spectra will be increased, as the distance to the object increases, the length of the spectra gets shorter, this only has to occur over a very very small distance to produce a shift in the absorption lines.
The observations show that there is almost a direct relationship between distance and redshift, there is also a direct relationship to angle of incidence and distance.
The universe is expanding at a really nice constant rate except at the edges of optical resolution..........

Now, if the light is not parallel, but divergent, even a tiniest little bit, when refracted, the length of the spectra will be increased, as the distance to the object increases, the length of the spectra gets shorter, this only has to occur over a very very small distance to produce a shift in the absorption lines.

So you are saying that the smaller the deviation from parallel the larger the redshift?

Could you demonstrate the math that supports this?

Provide me with the solutions to the wave equations for parabolic caustic curves for a subset of large objects at distance and i'll happily supply you with the math that supports it.

Anyway that's not quite what I'm saying, the parallel is an ideal model of the (X^2)/4 curve, to determine the ideal redshift you would need parallel light as a base to calculate the deviation from the ideal, which you cannot do. On top of that, the smallest deviation from 'parallel' would be an object so far away the light would not split into a full spectra, combined with the surface errors of the lens you would get an increasing error in the spectra produced.
The best way I can put it is this, the smaller the deviation from the parallel, the closer to the ideal spectra you get with the spectra produced, the larger the deviation the longer the distance the spectra is spread across, the redshift being the apparent position of a given absorption line between the two spectra.

It would be easier to determine the blue shift, or more specifically the greatest shift from blue towards red, and then see if the shift is within the scope of the instrument, that is to say, does the instrument have a cut off point beyond which the blue-shifted-to-red range is no longer measurable.

Question: is the frequency of light actually measured either side of an absorption line to determine the probable frequency or is the entire spectra a comparison against a known?

So what happens IF the light is more/less divergent than your expecting it to be as it casts across the ccd? (After all you have gone and calibrated the instrument to an ideal model)
And what frequency range does each ccd cell respond to?

Provide me with the solutions to the wave equations for parabolic caustic curves for a subset of large objects at distance and i'll happily supply you with the math that supports it.

No math just hand waving - OK.


Anyway that's not quite what I'm saying, the parallel is an ideal model of the (X^2)/4 curve, to determine the ideal redshift you would need parallel light as a base to calculate the deviation from the ideal

Why? there is no evidence or even a guess as to the wavelength being affected by non parallel light. Besides your conjecture is the less parallel the light rays are the smaller the redshift.:rolleyes:

,
which you cannot do. On top of that, the smallest deviation from 'parallel' would be an object so far away the light would not split into a full spectra, combined with the surface errors of the lens you would get an increasing error in the spectra produced.

Bovine excrement - prove that statement. Besides according to you huge deviations from parallel are suppose to give tiny errors. The smaller the deviation the larger the redshift remember?


The best way I can put it is this, the smaller the deviation from the parallel, the closer to the ideal spectra you get with the spectra produced, the larger the deviation the longer the distance the spectra is spread across, the redshift being the apparent position of a given absorption line between the two spectra.

Hmmm now it seems you are saying the sun should have a larger redshift than a star in the andromeda galaxy.


It would be easier to determine the blue shift, or more specifically the greatest shift from blue towards red, and then see if the shift is within the scope of the instrument, that is to say, does the instrument have a cut off point beyond which the blue-shifted-to-red range is no longer measurable.

You don't have any idea what you are talking about do you?


Question: is the frequency of light actually measured either side of an absorption line to determine the probable frequency or is the entire spectra a comparison against a known?

Correction: You DON'T know what yoyu are talking about!


So what happens IF the light is more/less divergent than your expecting it to be as it casts across the ccd? (After all you have gone and calibrated the instrument to an ideal model)
And what frequency range does each ccd cell respond to?

You should quit while your behind....

Doppler redshift observed using parabolic reflector telescopes is an aberration
Are you saying that the whole wold is wrong because they are using defective equipment?

In the first place, you might want to ask anybody here if they ever had to calibrate an instrument before.

Second, the purpose of a parabolic reflector is to collect a large cross section of incident light to give the collector gain. And this is because the detector has a minimum threshold due to its signal to noise ratio. The parabola has a focus. That is, any ray (within the field of view) that falls incident on any infinitesimal element of the lens will reflect at such an angle that it passes through the focus. So it allows gain to compensate for limited sensitivity.

You seem to be of the opinion that if some rays take longer to arrive at the detector than others, then red shift has occurred.

Here you are simply confusing phase shift (longer path) and frequency shift (red shift due to frame dragging).

So no, there is no frequency shift as you might imagine. Phase shift would be insignificant since the light is not coherent to begin with.

Second, the purpose of a parabolic reflector is to collect a large cross section of incident light to give the collector gain. And this is because the detector has a minimum threshold due to its signal to noise ratio. The parabola has a focus. That is, any ray (within the field of view) that falls incident on any infinitesimal element of the lens will reflect at such an angle that it passes through the focus. So it allows gain to compensate for limited sensitivity.


Again, parallel light focuses to a point, incident light does not, it has a series of points, the light is converging at the reflector. You just said incident light and then tried to explain the parabolic reflector in terms of parallel light.
I'm not talking about longer path although that will occur to some degree.
Optically you will only see the aberration at the limit of the optics, even though you will loose some resolution, it's when you refract the light after it passes through a series of focal points, the light will NOT be parallel, it will be divergent before it gets refracted, you've gone and designed the instrumentation based on an ideal model that only works for spherical chickens in a vacuum....

The world isn't wrong at all,

“the assumption that redshifts are not velocity shifts is more economical and less vulnerable, except for the fact that, at the moment,
no other satisfactory explanation [i.e., apart from the Doppler effect] is known.”
If through experimental observation it is found that the redshift better fits a model based on an aberration, the data collected isn't wrong, I doubt there would be much sleep lost, in fact the improvements to optics and astronomy would outweigh any losses.

It's completely testable, or are you going to not test it because light is parallel?

It's completely testable, or are you going to not test it because light is parallel?

It is not going to be tested for same reason that no one is going to test to see if the redshift is due to the type of metal supporting the telescopes.:rolleyes:


If you think your idle conjecture is worth testing, looks like you are going to have to do it yourself.;)

Which bit is idle conjecture?, light not being parallel?, parabolic caustic curves?, refraction? spectrum broadening?
Or do you not believe the angle of incidence is proportional to distance?
Take any galaxy, from the known data about it, work out the angle of the light cone hitting the reflector, then take one of similar size that is known to be twice the distance and work out the angle of the light cone hitting the reflector, you'll find the angle of the light cone from the one further away to be approximately half that of the closer galaxy.
You can go collect the data and see for yourself or normalize the dimensions and produce a general relationship, angle of incidence is proportional to distance.

Even binary stars show the relationship, the redshift changes over time as they orbit each other, you can directly see the change in angle of incidence as the light cone grows and shrinks, apparently though this is down to some crap about inelastic photon-atom interactions, nothing to do with angle of incidence, funny how it's a perfect sine wave.......

One day some amateur astronomer will go and accidentally put a collimating reflector before the 'point' of focus and end up with a bucket full of blue shift.

You know though, there should be alot of coma in the optical images, as if you looked at a star that was just offset in the mirror and then lathed it around the center, not sure what that would look like, you'd have a decent (but improvable) image in the center with a halo of light around most images, not seen that in any images though, it's all dust reflections or something. You'd probably get a few images with gradient ripples as well under certain circumstances, not seen any of them either.

Again, parallel light focuses to a point, incident light does not, it has a series of points, the light is converging at the reflector. You just said incident light and then tried to explain the parabolic reflector in terms of parallel light.
Well then we can start with some basic definitions. "Incident" light is any light that impinges upon a specified surface. "Field of view" is the extent of the viewable area of the telescope. "Coherent" means that all rays are in phase, that is, the sum of all rays produces a pure sinusoid.

As I understood your complaint, you're saying that any two rays that are phase shifted on account of the parabolic mirror combine to simulate red shift (or blue shift). My statement to you is that this is incorrect, because the star light is not coherent to begin with, and additional phase scattering by the dish will have no meaningful effect on the phase information, since it was random to begin with. Furthermore, phase shift is not equivalent to red or blue shift. Frequency shift (over the spectrum) is. Therefore, you can't simulate red or blue shift simply by introducing a parabolic mirror.



I'm not talking about longer path although that will occur to some degree.
Optically you will only see the aberration at the limit of the optics, even though you will loose some resolution, it's when you refract the light after it passes through a series of focal points, the light will NOT be parallel, it will be divergent before it gets refracted, you've gone and designed the instrumentation based on an ideal model that only works for spherical chickens in a vacuum....

This still makes no sense. All light rays within the field of view of the mirror are pseudo-randomly phase shifted upon arrival at the focus. But each and every ray retains its original frequency content. Since the phase information is random to begin with, this additional phase distortion is not going to alter the spectral content. That is, you need frequency shift, not phase shift, to simulate red or blue shift. And that's the part that is preserved in a parabolic mirror.


The world isn't wrong at all,

If through experimental observation it is found that the redshift better fits a model based on an aberration, the data collected isn't wrong, I doubt there would be much sleep lost, in fact the improvements to optics and astronomy would outweigh any losses.

It's completely testable, or are you going to not test it because light is parallel?
By you analysis, every parabolic dish in the world is inherently defective. That's a huge indictment against a large population of very smart people. It makes no sense. You seem to be assuming that nobody tests or calibrates their precision instruments which is ludicrous. Also note, if this actually occurred as you think, it would be advantageous, because passive devices could be built out of dishes which produce ultrawide band spectral shifting (such as a downconverter). It would improve signal to noise ratios in some cases and open new doors to technology.

Unless we're still speaking a different language, you would have to demonstrate a frequency shift, not a phase shift, that arises out of using a parabolic mirror. But you can't, because it doesn't, hence my remarks.

Yeah, realised you meant incidental when I was falling asleep.

Could you re-read the first post and replace the word diffraction with refraction, silly mistake but it does confuse the issue. I'm not talking about phase shift at all.

Thing is these very smart people who understand optics know that the parabolic dish is inherently defective, they also know light isn't parallel, which is why it's deffective, but it's the best curve there is that can be used over a range of distances.

Is there experimental evidence to discount angle of incidence as the cause for the redshift?
What happens to the redshift when you offset the object in the mirror, give it additional angle of incidence.
Redshift is a valuable tool, what happens when you set the instruments up for galaxies and then measure smaller objects, there will be a huge shift towards the red with the smaller objects, you would assume they were very far away, until you discover one sitting in front of a galaxy, quasars....