# I Some redshift from prism effect of a gravitational lens?

#### Dustin Maki

Summary
What degree of redshift is attributable to chromatic aberration from gravitational lensing? When the universe was more dense, more of the light traveling during that period was being bent. As red is bent the least, wouldn't everything from that period appear more red regardless of Doppler effects? Is this accounted for in current models describing accelerated expansion?
A quick search turned up Simaciu, Ion. (1997). Chromatic aberration of gravitational lens. 10.13140/2.1.1133.6003.
The math is beyond me so I first made a basic assumption that chromatic aberration of gravitational lenses worked somewhat analogous to a prism in that red is bent less than other colors. So, before anything else, can you confirm or disprove that assumption?

That means the red light most approximates the direct path and would be most abundant along that path while other colors are proportionally more scattered. Would that result in redshift of spectral lines? 2nd assumption, yes.

Beyond about 5 billion years ago, was the universe so dense with galaxies, or other refractory objects that the light from that period which would eventually reach us could be bent(on average) one or more times? If so, it stands to reason that on average, the further from us a light source is, the more times it would have been bent, thus the redder it would become. That would be due to both increased universal density and longer specific path. I don't know how to judge sufficient density, so pending confirmation, 3rd assumption, yes.

Given the above, is the amount of redshift attributable to chromatic aberration of gravitational lenses sufficient to alter the estimates of accelerated expansion?
Is it sufficient to alter estimates of basic expansion rates?

Besides looking at the plausibility of this question in the aggregate. We have the visible light from those 1A supernovae. Is there any way to discern redshift due to chromatic aberration of gravitational lenses from redshift due to doppler effects? Chromatic aberration shift is stepwise per each gravitational lens and Doppler is continuously proportional to distance. That may be a clue.

Assuming redshift due to chromatic aberration is a thing, or even if it's not, the light that is bent by gravitational lenses follows a longer path to reach us than the direct path from the source. A tiny bend in the path results in only a tiny percentage change of distance, but over cosmic lengths that tiny percent can be a very large absolute distance change.

Path error from bending grows with distance from source independent from number of bends provided bends >= 1.
Chromatic aberration shift grows with number of bends.
The probability of bends occurring would grow not with distance from source, but with the longer specific zigzag path which in turn grows with distance from source. The effects multiply. I am not sure if Doppler effects would be similarly multiplied.
Doppler and the sum of all chromatic aberration shifts are additive.

To reiterate from the summary, have these factors been accounted for in accelerated expansion models?
If so, the topic of my next question is "how?"

Nonsequitor: When making a statement that contains a question, is the proper punctuation mark a period or a question mark?

#### Drakkith

Staff Emeritus
2018 Award
The math is beyond me so I first made a basic assumption that chromatic aberration of gravitational lenses worked somewhat analogous to a prism in that red is bent less than other colors. So, before anything else, can you confirm or disprove that assumption?
As far as I know there is no such thing as gravitational chromatic aberration. All frequencies are bent equally to my knowledge. This makes sense to me as light isn't passing through a medium with a refractive index that varies with frequency, but through curved spacetime, whose curvature is equal for all frequencies.

#### Ibix

A quick search turned up Simaciu, Ion. (1997). Chromatic aberration of gravitational lens. 10.13140/2.1.1133.6003.
That paper "models the vacuum as an electron-positron plasma", and appears to be only available via ResearchGate (edit: on closer inspection I see it was published in a Bulgarian journal - presumably not in English, as searching on the exact title only turns up the ResearchGate version and the author's CV). I rather suspect that it isn't a mainstream physical theory.

General relativity certainly does not predict any chromatic aberration, although more or less every other aberration will affect a gravitational lens.

#### Mordred

I'm fairly confident such a phenomena would be detectable in all the spectrum analysis performed in cosmology applications. Which is incredibly extensive...

So it's fairly safe to say the article is not mainstream

#### Mordred

Roflmao I can't shake this visualization of some astrophysicist performing a spectrum analysis of some distant star yelling "Where is the Blooming hydrogen???"

#### kimbyd

Gold Member
2018 Award
Summary: What degree of redshift is attributable to chromatic aberration from gravitational lensing? When the universe was more dense, more of the light traveling during that period was being bent. As red is bent the least, wouldn't everything from that period appear more red regardless of Doppler effects? Is this accounted for in current models describing accelerated expansion?

A quick search turned up Simaciu, Ion. (1997). Chromatic aberration of gravitational lens. 10.13140/2.1.1133.6003.
The math is beyond me so I first made a basic assumption that chromatic aberration of gravitational lenses worked somewhat analogous to a prism in that red is bent less than other colors. So, before anything else, can you confirm or disprove that assumption?

That means the red light most approximates the direct path and would be most abundant along that path while other colors are proportionally more scattered. Would that result in redshift of spectral lines? 2nd assumption, yes.

Beyond about 5 billion years ago, was the universe so dense with galaxies, or other refractory objects that the light from that period which would eventually reach us could be bent(on average) one or more times? If so, it stands to reason that on average, the further from us a light source is, the more times it would have been bent, thus the redder it would become. That would be due to both increased universal density and longer specific path. I don't know how to judge sufficient density, so pending confirmation, 3rd assumption, yes.

Given the above, is the amount of redshift attributable to chromatic aberration of gravitational lenses sufficient to alter the estimates of accelerated expansion?
Is it sufficient to alter estimates of basic expansion rates?

Besides looking at the plausibility of this question in the aggregate. We have the visible light from those 1A supernovae. Is there any way to discern redshift due to chromatic aberration of gravitational lenses from redshift due to doppler effects? Chromatic aberration shift is stepwise per each gravitational lens and Doppler is continuously proportional to distance. That may be a clue.

Assuming redshift due to chromatic aberration is a thing, or even if it's not, the light that is bent by gravitational lenses follows a longer path to reach us than the direct path from the source. A tiny bend in the path results in only a tiny percentage change of distance, but over cosmic lengths that tiny percent can be a very large absolute distance change.

Path error from bending grows with distance from source independent from number of bends provided bends >= 1.
Chromatic aberration shift grows with number of bends.
The probability of bends occurring would grow not with distance from source, but with the longer specific zigzag path which in turn grows with distance from source. The effects multiply. I am not sure if Doppler effects would be similarly multiplied.
Doppler and the sum of all chromatic aberration shifts are additive.

To reiterate from the summary, have these factors been accounted for in accelerated expansion models?
If so, the topic of my next question is "how?"

Nonsequitor: When making a statement that contains a question, is the proper punctuation mark a period or a question mark?
This is only of potential concern with strong gravitational lensing. Most lines of sight never encounter strong gravitational lenses, and so never have the chance to encounter any aberration (if it's even possible).

Strong lenses, however, might potentially do this. But certainly not by much (or it'd be readily visible in current images). In particular, the strongest lenses are large galaxy clusters, which contain a very hot gas. This hot gas, being much more dense than the intergalactic medium, might offer some opportunity for increased aberration.

But, like I said, it can't be a large effect or else it'd be really noticeable in current images of strong lenses.

You can find images yourself, but there are a few good ones linked in the Wikipedia article on the matter:
https://en.wikipedia.org/wiki/Strong_gravitational_lensing

#### Mordred

Just a side note using strong lensing is a very versatile tool to extend the Hubble telescopes range. They and other telescopes extensively use this

#### Dustin Maki

It is certainly a very small effect if it exists at all. However it would be a potential source of error in some fairly popular observations. Mr. Simaciu attached his name to this, so I thought that might warrant at least a cursory look at the science in the paper rather than criticism of where it was published. As a layperson I do not have the knowledge to judge fairly so I invite any comments on the content inside the cited paper. I'll post it here if that is allowed. I just wasn't sure because I downloaded it from research gate. It is one of the few places an interested layperson can get more than just abstracts without a subscription. kimbyd, thanks for your insight. Would the difference between strong lensing and weak be a difference in magnitude or a difference in kind?

#### Ibix

I thought that might warrant at least a cursory look at the science in the paper rather than criticism of where it was published.
You'll notice I quoted from the paper. The point about ResearchGate isn't that stuff posted on ResearchGate is bad, but stuff posted only on ResearchGate suggests it wasn't of sufficient quality to be published elsewhere. This does turn out to have been published elsewhere, but only in a conference proceedings edition of a journal that now appears to be defunct - again, this isn't great evidence of quality. On top of that, the predictions it makes contradict what relativity says about gravitational lensing. And, as @Mordred notes, the effect would show up in spectroscopy, which is a major part of routine astronomical work.

So I think it's been given a perfectly fair hearing.

#### PeterDonis

Mentor
It is one of the few places an interested layperson can get more than just abstracts without a subscription.
You can find lots of papers on arxiv.org, which does not require a subscription.

I thought that might warrant at least a cursory look at the science in the paper rather than criticism of where it was published.
Everyone who responded has given good reasons why the scientific claims of the paper should not be trusted, regardless of where it was published.

#### Mordred

One note, consider a miniscule change in two parallel beams. Each beam being a different frequency.

Then extend the length of said beam over a distance of let's say 1 parsec.
Even a 1000 the of a degree change of angle would become highly noticable.
That single parsec isn't the gravity well diameter but simply an observer distance after the change.

Lol however small becomes significant with distance to far away observers

Edit keep in mind without seeing the paper itself I am assuming it's an application involving Snell's law and refractive index. Ie rainbow effect through a prism

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Staff Emeritus
It is certainly a very small effect if it exists at all. However it would be a potential source of error in some fairly popular observations
You can't have it both ways. If it's too small to tell if it exists, it's too small to make a significant change to other measurements.

#### Mordred

Good way to describe that perspective...

I actually considered the ramifications on Planck datasets. A large factor in judging the universe curvature involves searching out distortions. This was a major advancement in getting a determination in deciding that our universe is incredibly close to flat in terms of lightpath/worldliness.
Consider how many strong gravity wells would be encountered on any frequency surveys as far back as the surface of last scattering. Then imagine what this paper proposes...the randomness of distortions would be
immense....

lol don't mind me I am well practiced at shooting down random non mainstream theories. Coincidentally many of them are on researchgate . Part of the reason is many of the authors of various papers tend to visit other forums to advertise their papers. As one that is part of the administration staff on one of those sites that supports Speculative theories ( within tight rules and regulations). I often see a great deal of theories that are seemingly plausible until one considers the ramifications outside those considered within the paper.

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#### kimbyd

Gold Member
2018 Award
It is certainly a very small effect if it exists at all. However it would be a potential source of error in some fairly popular observations. Mr. Simaciu attached his name to this, so I thought that might warrant at least a cursory look at the science in the paper rather than criticism of where it was published. As a layperson I do not have the knowledge to judge fairly so I invite any comments on the content inside the cited paper. I'll post it here if that is allowed. I just wasn't sure because I downloaded it from research gate. It is one of the few places an interested layperson can get more than just abstracts without a subscription. kimbyd, thanks for your insight. Would the difference between strong lensing and weak be a difference in magnitude or a difference in kind?
Magnitude. Strong lensing happens when the line-of-sight comes very close to a dense object, and results in arc-like shapes and Einstein rings. Weak lensing occurs with lines of sight that don't come as close, and generally results in just a small shape distortion.

#### confusedhome

Summary: What degree of redshift is attributable to chromatic aberration from gravitational lensing? When the universe was more dense, more of the light traveling during that period was being bent. As red is bent the least, wouldn't everything from that period appear more red regardless of Doppler effects? Is this accounted for in current models describing accelerated expansion?

A quick search turned up Simaciu, Ion. (1997). Chromatic aberration of gravitational lens. 10.13140/2.1.1133.6003.
The math is beyond me so I first made a basic assumption that chromatic aberration of gravitational lenses worked somewhat analogous to a prism in that red is bent less than other colors. So, before anything else, can you confirm or disprove that assumption?

That means the red light most approximates the direct path and would be most abundant along that path while other colors are proportionally more scattered. Would that result in redshift of spectral lines? 2nd assumption, yes.

Beyond about 5 billion years ago, was the universe so dense with galaxies, or other refractory objects that the light from that period which would eventually reach us could be bent(on average) one or more times? If so, it stands to reason that on average, the further from us a light source is, the more times it would have been bent, thus the redder it would become. That would be due to both increased universal density and longer specific path. I don't know how to judge sufficient density, so pending confirmation, 3rd assumption, yes.

Given the above, is the amount of redshift attributable to chromatic aberration of gravitational lenses sufficient to alter the estimates of accelerated expansion?
Is it sufficient to alter estimates of basic expansion rates?

Besides looking at the plausibility of this question in the aggregate. We have the visible light from those 1A supernovae. Is there any way to discern redshift due to chromatic aberration of gravitational lenses from redshift due to doppler effects? Chromatic aberration shift is stepwise per each gravitational lens and Doppler is continuously proportional to distance. That may be a clue.

Assuming redshift due to chromatic aberration is a thing, or even if it's not, the light that is bent by gravitational lenses follows a longer path to reach us than the direct path from the source. A tiny bend in the path results in only a tiny percentage change of distance, but over cosmic lengths that tiny percent can be a very large absolute distance change.

Path error from bending grows with distance from source independent from number of bends provided bends >= 1.
Chromatic aberration shift grows with number of bends.
The probability of bends occurring would grow not with distance from source, but with the longer specific zigzag path which in turn grows with distance from source. The effects multiply. I am not sure if Doppler effects would be similarly multiplied.
Doppler and the sum of all chromatic aberration shifts are additive.

To reiterate from the summary, have these factors been accounted for in accelerated expansion models?
If so, the topic of my next question is "how?"

Nonsequitor: When making a statement that contains a question, is the proper punctuation mark a period or a question mark?
All these effects are accepted by the scientific community and there is a strong need for a standard to compare these effects to. The ‘Cosmic Microwave Background’ is the most logical starting point to obtain a standard, however much research remains to be done.
Since its confirmation of existence each survey has given more detail than the one before it which indicate just how prevalent these effects are since the beginning.
Once we understand the end points of the ‘thermometer’ the better we will be able to determine the degree of these effects in between.
This research is ongoing now, and as much as we would like it can only be accomplished in a finite amount on time which is dependent on the resources allocated to it. Be patient, it will be done

#### Mordred

Really it's been over 19 years since that paper and it's only available on research gate. Can you supply a fully peer reviewed paper showing such a study.

"Some redshift from prism effect of a gravitational lens?"

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