Starship Asterisk*

johnnydeep wrote: ↑Wed Apr 10, 2024 1:42 pm And since I've been following this - ahem - debate - I finally clicked on both the links posted in support of Roman's view, and he's either the sole author or the co-author. I have no opinion on the merits of the papers since I haven't tried to read them (though I am slightly curious - lack of requisite mathematical skill notwithstanding).

Chris Peterson wrote: ↑Wed Apr 10, 2024 1:58 pm

johnnydeep wrote: ↑Wed Apr 10, 2024 1:42 pm

Chris Peterson wrote: ↑Wed Apr 10, 2024 12:55 am
Consensus is one of the most important parts of the scientific method. It means nearly all cosmologists agree on the general origin of the CMB. Which means nearly everyone else should agree, as well. Because experts are experts, and most others are not. If you're not an expert, you're not qualified to have a fringe "opinion" on the subject.

There's nothing wrong with either special or general relativity. Both are robustly supported by many independent lines of evidence.

You are in danger here of being assessed a crank and banned from the forum.

And since I've been following this - ahem - debate - I finally clicked on both the links posted in support of Roman's view, and he's either the sole author or the co-author. I have no opinion on the merits of the papers since I haven't tried to read them (though I am slightly curious - lack of requisite mathematical skill notwithstanding).

But, yes, the scientific consensus of current experts in their fields is the best source of knowledge we have. That is, until some genius iconoclast comes along and proves all those experts wrong.

But you know what else those "genius iconoclasts" are? They're experts in the field already. Genius alone isn't going to come up with something new. What's needed is genius and actual knowledge of the subject. Some plumber with a 200 IQ isn't going to develop a new theory of cosmology if they aren't already well versed in current theory and the state of evidence.

johnnydeep wrote: ↑Wed Apr 10, 2024 1:42 pm

Chris Peterson wrote: ↑Wed Apr 10, 2024 12:55 am

Roman_Szostek wrote: ↑Wed Apr 10, 2024 12:44 am

What does "scientific consensus" mean?

The universe was thought to be 13 billion years old based on the dubious quality of the General Theory of Relativity equations. Ignoring that this is a far-reaching extrapolation of equations that have a questionable relationship to reality, in a situation where we know almost nothing about the laws of physics.

And the same "experts" came up with a fairy tale that microwave background radiation was created once at the beginning of the universe, almost exactly 13 billion years ago.
These "experts" tell you when the universe was created, but they have trouble understanding simple experiments like the Michelson-Morley experiment and formulas such as the Lorentz transformation:
Formal proof that the mathematics on which the Special Theory of Relativity is based is misinterpreted

This is not science, it is religion, or if you prefer, these are fairy tales.

Consensus is one of the most important parts of the scientific method. It means nearly all cosmologists agree on the general origin of the CMB. Which means nearly everyone else should agree, as well. Because experts are experts, and most others are not. If you're not an expert, you're not qualified to have a fringe "opinion" on the subject.

There's nothing wrong with either special or general relativity. Both are robustly supported by many independent lines of evidence.

You are in danger here of being assessed a crank and banned from the forum.

And since I've been following this - ahem - debate - I finally clicked on both the links posted in support of Roman's view, and he's either the sole author or the co-author. I have no opinion on the merits of the papers since I haven't tried to read them (though I am slightly curious - lack of requisite mathematical skill notwithstanding).

But, yes, the scientific consensus of current experts in their fields is the best source of knowledge we have. That is, until some genius iconoclast comes along and proves all those experts wrong.

Chris Peterson wrote: ↑Wed Apr 10, 2024 12:55 am

Roman_Szostek wrote: ↑Wed Apr 10, 2024 12:44 am

Chris Peterson wrote: ↑Tue Apr 09, 2024 6:38 pm It is hardly a guess. It is scientific consensus, and therefore what most people should consider the likely answer.

What does "scientific consensus" mean?

The universe was thought to be 13 billion years old based on the dubious quality of the General Theory of Relativity equations. Ignoring that this is a far-reaching extrapolation of equations that have a questionable relationship to reality, in a situation where we know almost nothing about the laws of physics.

And the same "experts" came up with a fairy tale that microwave background radiation was created once at the beginning of the universe, almost exactly 13 billion years ago.
These "experts" tell you when the universe was created, but they have trouble understanding simple experiments like the Michelson-Morley experiment and formulas such as the Lorentz transformation:
Formal proof that the mathematics on which the Special Theory of Relativity is based is misinterpreted

This is not science, it is religion, or if you prefer, these are fairy tales.

Consensus is one of the most important parts of the scientific method. It means nearly all cosmologists agree on the general origin of the CMB. Which means nearly everyone else should agree, as well. Because experts are experts, and most others are not. If you're not an expert, you're not qualified to have a fringe "opinion" on the subject.

There's nothing wrong with either special or general relativity. Both are robustly supported by many independent lines of evidence.

You are in danger here of being assessed a crank and banned from the forum.

Roman_Szostek wrote: ↑Wed Apr 10, 2024 12:44 am

Chris Peterson wrote: ↑Tue Apr 09, 2024 6:38 pm It is hardly a guess. It is scientific consensus, and therefore what most people should consider the likely answer.

What does "scientific consensus" mean?

The universe was thought to be 13 billion years old based on the dubious quality of the General Theory of Relativity equations. Ignoring that this is a far-reaching extrapolation of equations that have a questionable relationship to reality, in a situation where we know almost nothing about the laws of physics.

And the same "experts" came up with a fairy tale that microwave background radiation was created once at the beginning of the universe, almost exactly 13 billion years ago.
These "experts" tell you when the universe was created, but they have trouble understanding simple experiments like the Michelson-Morley experiment and formulas such as the Lorentz transformation:
Formal proof that the mathematics on which the Special Theory of Relativity is based is misinterpreted

This is not science, it is religion, or if you prefer, these are fairy tales.

Chris Peterson wrote: ↑Tue Apr 09, 2024 6:38 pm It is hardly a guess. It is scientific consensus, and therefore what most people should consider the likely answer.

Roman_Szostek wrote: ↑Tue Apr 09, 2024 4:00 pm

Chris Peterson wrote: ↑Sun Apr 03, 2022 1:53 pm The CMB is the edge of the observable universe, not the the entire universe.

I doubt this is the case. There is no evidence that microwave background radiation was produced 13 billion years ago, when the universe was allegedly forming. These are guesses.

In my opinion, microwave background radiation is produced all the time.

In this article
The existence of a universal frame of reference, in which it propagates light, is still an unresolved problem of physics
https://journals.yu.edu.jo/jjp/JJPIssue ... 022/3.html
we formulated the hypothesis that the microwave background radiation is thermal ether radiation.

This is consistent with the fact that the microwave background radiation has a thermal radiation distribution.

Chris Peterson wrote: ↑Sun Apr 03, 2022 1:53 pm The CMB is the edge of the observable universe, not the the entire universe.

alter-ego wrote: ↑Sat Apr 16, 2022 2:40 am

Chris Peterson wrote: ↑Fri Apr 15, 2022 10:57 pm

MarkBour wrote: ↑Fri Apr 15, 2022 8:26 pm Thanks again, alter ego and chris.

I'm still expecting that with the benefit of the JWST having a larger mirror and one better suited to infrared than anything we've been able to look through (from space) before, that it will detect serious galaxies, whose spectra indicate a larger redshift than ever before. What would be the highest z values it might detect?

As to the rest of my musings, I'll just go back to keeping them to myself for the time being, or perhaps find some other forum where I can get this same kind of feedback and discuss any ideas, but where my wonderings are more appropriate to the forum. Thanks for your responses, though.

Back to today's APOD, it is pretty cool, noting this apparent motion of the Earth relative to the CMB. And clearly, the CMB as we see it from here, is:

The highest redshift it's possible to detect would be that of the CMB: z = 1100. Anything closer would be moving away from us slower and have a lower redshift.

I wouldn't be surprised if the first stars to formed between 100 Myr and 200 Myr after the BB (z = 20 to 30).

Chris Peterson wrote: ↑Fri Apr 15, 2022 10:57 pm

MarkBour wrote: ↑Fri Apr 15, 2022 8:26 pm Thanks again, alter ego and chris.

I'm still expecting that with the benefit of the JWST having a larger mirror and one better suited to infrared than anything we've been able to look through (from space) before, that it will detect serious galaxies, whose spectra indicate a larger redshift than ever before. What would be the highest z values it might detect?

As to the rest of my musings, I'll just go back to keeping them to myself for the time being, or perhaps find some other forum where I can get this same kind of feedback and discuss any ideas, but where my wonderings are more appropriate to the forum. Thanks for your responses, though.

Back to today's APOD, it is pretty cool, noting this apparent motion of the Earth relative to the CMB. And clearly, the CMB as we see it from here, is:

The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K. The spectral radiance dEν/dν peaks at 160.23 GHz, in the microwave range of frequencies, corresponding to a photon energy of about 6.626 ⋅ 10−4 eV. Alternatively, if spectral radiance is defined as dEλ/dλ, then the peak wavelength is 1.063 mm (282 GHz, 1.168 ⋅ 10−3 eV photons).

The highest redshift it's possible to detect would be that of the CMB: z = 1100. Anything closer would be moving away from us slower and have a lower redshift.

MarkBour wrote: ↑Fri Apr 15, 2022 8:26 pm Thanks again, alter ego and chris.

I'm still expecting that with the benefit of the JWST having a larger mirror and one better suited to infrared than anything we've been able to look through (from space) before, that it will detect serious galaxies, whose spectra indicate a larger redshift than ever before. What would be the highest z values it might detect?

As to the rest of my musings, I'll just go back to keeping them to myself for the time being, or perhaps find some other forum where I can get this same kind of feedback and discuss any ideas, but where my wonderings are more appropriate to the forum. Thanks for your responses, though.

Back to today's APOD, it is pretty cool, noting this apparent motion of the Earth relative to the CMB. And clearly, the CMB as we see it from here, is:

The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K. The spectral radiance dEν/dν peaks at 160.23 GHz, in the microwave range of frequencies, corresponding to a photon energy of about 6.626 ⋅ 10−4 eV. Alternatively, if spectral radiance is defined as dEλ/dλ, then the peak wavelength is 1.063 mm (282 GHz, 1.168 ⋅ 10−3 eV photons).

The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K. The spectral radiance dEν/dν peaks at 160.23 GHz, in the microwave range of frequencies, corresponding to a photon energy of about 6.626 ⋅ 10−4 eV. Alternatively, if spectral radiance is defined as dEλ/dλ, then the peak wavelength is 1.063 mm (282 GHz, 1.168 ⋅ 10−3 eV photons).

MarkBour wrote: ↑Sun Apr 10, 2022 10:29 pm First, let me say that I appreciate these answers, from Chris and alter-ego. Also, the further comments that Ann and johnnydeep have added.

An easy response to my post would have been something like: "No, you just need to take one or more courses that cover this, then you'd get it. Until then, just keep your uneducated views to yourself." I'm grateful that this is not what I got, but that you took the time to read it, consider, and respond.

Chris Peterson wrote: ↑Fri Apr 08, 2022 9:06 pm

MarkBour wrote: ↑Fri Apr 08, 2022 4:39 pm I think I'm questioning how rational the current interpretation of high-redshift data is.

Very rational. It hangs on all of the underlying theory of the lambda-CDM model, which is itself very well supported by multiple independent lines of evidence.
. . .

Great. I'd love nothing better than to learn more about the ΛCDM model and how, from the sequence of observations and thought, this model came to be the dominant accepted theory. Watching YouTube videos by physics popularizers hasn't gotten me anywhere in this regard. I've also read a few books, aimed at the layman, that got into these topics, and have just found myself repeating over and over again: "Why do you think that?"

More helpfully, I just read the Wikipedia article on ΛCDM. A lot of it is very concise and large chunks of it are just beyond my ability to understand without further study. It does give an opening summary of the main points as to why the ΛCDM is the currently most-accepted model, so those are topics I probably should try to follow further. The article does seem to be very balanced, though. There are quite a number of objections and difficulties mentioned throughout. And, as if to support my skepticism, there is this one small section nearly at the end, that summarizes my gut-level concern about it:

Excerpt from: https://en.wikipedia.org/wiki/Lambda-CDM_model
Unfalsifiability
It has been argued that the ΛCDM model is built upon a foundation of conventionalist stratagems, rendering it unfalsifiable in the sense defined by Karl Popper.[77]

----------------------------------

Ann wrote: ↑Sat Apr 09, 2022 4:21 am

alter-ego wrote: ↑Sat Apr 09, 2022 2:48 am
Yes, I can answer that. You've picked an interesting redshift example. Viewing z = 7 (now) won't change much over 7 Gyr. The cosmic acceleration causes redshift minima to occur at different times, i.e. minima times are dependent on z. Several years ago, I had a sudden interest in redshift evolution over time for a fixed observer (e.g. the milky way). It culminated in the plot below. I find it very interesting as it reveals characteristics I wasn't expecting. I won't elaborate any further now, and although I can calculate your specific example, I interpolated between the closest two curves for this post.

Assuming you're adding 7 Gyr to present time, the answer is still close to 7. Note, dz/dt depends on when the first observation is made.
The two vertical lines mark now (13.72 Gyr) and +7Gyr (20.72 Gyr). The big arrows point to the two redshifts.
These calculations assume a flat spacetime. Also note, the evolution of the CMB redshift is plotted. It is the first electromagnetic radiation to fill the Universe. It was emitted roughly 380,000 years after the Big Bang, and therefore it's redshift (z ≈1100) cannot be exceeded by any visible object.
I'm expecting Webb to make discoveries pertinent to the onset and duration of the Dark Ages. I think the current thought is the first stars formed around 100 Myr after the BB (z~30)
 
(image not replotted)

...
Alter-ego, I wish you could sit down with me and give me the sort of information about your chart that a math idiot's brain can process.
...
Ann

Right on, Ann! Please let me attend that session, too ...

As I look at that diagram, if I understand it at all, I find two things that are amazing.

1. One is your statement, alter-ego, indicated by the arrows:
   An object we can observe today, with z=7, we would still be able to see 7 billion years from now, if it didn't stop emitting, and it would still have z=7. (!)
2. If we found an object right now showing at z=600, that object's z-shift is predicted to be diminishing rapidly at this time, and will bottom out way, way down at about z=8, before rising again. (!)
   *** Not correct. An object seen at z = 600 today will drop to z = 50 in another 16 Gyr ***

Hubble's Law wrote: Hubble tension
Multiple methods have been used to determine the Hubble constant. "Late universe" measurements using calibrated distance ladder techniques have converged on a value of approximately 73 km/s/Mpc. Since 2000, "early universe" techniques based on measurements of the cosmic microwave background have become available, and these agree on a value near 67.7 km/s/Mpc. (This is accounting for the change in the expansion rate since the early universe, so is comparable to the first number.) As techniques have improved, the estimated measurement uncertainties have shrunk, but the range of measured values has not, to the point that the disagreement is now highly statistically significant. This discrepancy is called the Hubble tension.

In December 2021, National Geographic reported that the cause of the Hubble tension discrepancy is not known. However, if the cosmological principle fails (see the section Violations of the cosmological principle in the Lambda-CDM model), then the existing interpretations of the Hubble constant and the Hubble tension have to be revised, which might resolve the Hubble tension.

One possibility is that the Hubble tension is caused by the KBC void, as measuring galactic supernovae inside a void is predicted by some authors to yield a larger local value for the Hubble constant than cosmological measures of the Hubble constant. However, other work has found no evidence for this in observations, finding the scale of the claimed underdensity to be incompatible with observations which extend beyond its radius. Important deficiencies were subsequently pointed out in this analysis, leaving open the possibility that the Hubble tension is indeed caused by outflow from the KBC void.

Another possibility is that the Hubble tension calls for new physics beyond the ΛCDM model. Moritz Haslbauer and collaborators have proposed Modified Newtonian Dynamics as a possible solution to the Hubble tension, while Marc Kamionkowski and collaborators have proposed an early dark energy model as a possible solution to the Hubble tension.

johnnydeep wrote: ↑Sun Apr 10, 2022 2:44 pm

Ann wrote: ↑Sun Apr 10, 2022 9:28 am Maybe I get a little bit of what you are saying, alter-ego.

If I get you correctly, the reason why the redshift increases so enormously the closer we get to the Big Bang is that the Universe underwent this incredible exponential growth spurt called inflation, and when that epoch was over the Universe was "braking hard". Instead of increasing exponentially in size "indefinitely" (wonder what that would have led to?) the Universe settled down, expanding very moderately.

During the epoch of inflation (and, in fact, during the epoch of "braking hard" after the inflation), the redshift changed dramatically, simply because of how much the actual growth of the Universe changed in a short time.

We are now in an epoch of acceleration. However, the acceleration has not "picked up speed" yet, and it has not yet affected the size of the Universe very much. Therefore, we are located in a "redshift valley", where the redshift stays relatively constant over billions of light-years.

Is that correct?

Ann

I'm still trying to digest alter-ego's posts - which are giving me heartburn - but inflation happened long before the universe became transparent to radiation (at about 380000 years). From Wikipedia:

https://en.wikipedia.org/wiki/Big_Bang#Inflation_and_baryogenesis wrote:Inflation stopped at around the 10⁻³³ to 10⁻³² seconds mark, with the universe's volume having increased by a factor of at least 10⁷⁸.

And a little later:

As the universe cooled, the rest energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years, the electrons and nuclei combined into atoms (mostly hydrogen), which were able to emit radiation. This relic radiation, which continued through space largely unimpeded, is known as the cosmic microwave background.[36]

I would think that T=0 for all redshift calculations starts at the "recombination" mark at 379000 years. Or I supposed it would actually be at the "decoupling" mark "shortly afterward". Again from Wikipedia:

https://en.wikipedia.org/wiki/Cosmic_microwave_background wrote:Cosmologists refer to the time period when neutral atoms first formed as the recombination epoch, and the event shortly afterwards when photons started to travel freely through space is referred to as photon decoupling. The photons that existed at the time of photon decoupling have been propagating ever since, though growing less energetic, since the expansion of space causes their wavelength to increase over time (and wavelength is inversely proportional to energy according to Planck's relation). This is the source of the alternative term relic radiation. The surface of last scattering refers to the set of points in space at the right distance from us so that we are now receiving photons originally emitted from those points at the time of photon decoupling.

Chris Peterson wrote: ↑Fri Apr 08, 2022 9:06 pm

MarkBour wrote: ↑Fri Apr 08, 2022 4:39 pm I think I'm questioning how rational the current interpretation of high-redshift data is.

Very rational. It hangs on all of the underlying theory of the lambda-CDM model, which is itself very well supported by multiple independent lines of evidence.
. . .

Excerpt from: https://en.wikipedia.org/wiki/Lambda-CDM_model
Unfalsifiability
It has been argued that the ΛCDM model is built upon a foundation of conventionalist stratagems, rendering it unfalsifiable in the sense defined by Karl Popper.[77]

Ann wrote: ↑Sat Apr 09, 2022 4:21 am

alter-ego wrote: ↑Sat Apr 09, 2022 2:48 am

MarkBour wrote: ↑Fri Apr 08, 2022 4:39 pm ...
The question I would like to ask, is:

Okay, we just saw a photon from a galaxy that astronomers say travelled for 13 billion years and landed in our telescope. A little ways away from it, another photon from the same source happened to miss our telescope. Let that photon continue to fly through space for another 7 billion years. What will be its redshift then? Can anyone answer this?

Yes, I can answer that. You've picked an interesting redshift example. Viewing z = 7 (now) won't change much over 7 Gyr. The cosmic acceleration causes redshift minima to occur at different times, i.e. minima times are dependent on z. Several years ago, I had a sudden interest in redshift evolution over time for a fixed observer (e.g. the milky way). It culminated in the plot below. I find it very interesting as it reveals characteristics I wasn't expecting. I won't elaborate any further now, and although I can calculate your specific example, I interpolated between the closest two curves for this post.

Assuming you're adding 7 Gyr to present time, the answer is still close to 7. Note, dz/dt depends on when the first observation is made.
The two vertical lines mark now (13.72 Gyr) and +7Gyr (20.72 Gyr). The big arrows point to the two redshifts.
These calculations assume a flat spacetime. Also note, the evolution of the CMB redshift is plotted. It is the first electromagnetic radiation to fill the Universe. It was emitted roughly 380,000 years after the Big Bang, and therefore it's redshift (z ≈1100) cannot be exceeded by any visible object.
I'm expecting Webb to make discoveries pertinent to the onset and duration of the Dark Ages. I think the current thought is the first stars formed around 100 Myr after the BB (z~30)
 
(image not replotted)

...
Alter-ego, I wish you could sit down with me and give me the sort of information about your chart that a math idiot's brain can process.
...
Ann

1. One is your statement, alter-ego, indicated by the arrows:
   An object we can observe today, with z=7, we would still be able to see 7 billion years from now, if it didn't stop emitting, and it would still have z=7. (!)
2. If we found an object right now showing at z=600, that object's z-shift is predicted to be diminishing rapidly at this time, and will bottom out way, way down at about z=8, before rising again. (!)

Ann wrote: ↑Sun Apr 10, 2022 9:28 am Maybe I get a little bit of what you are saying, alter-ego.


Evolution of the Universe Shutterstock.png

If I get you correctly, the reason why the redshift increases so enormously the closer we get to the Big Bang is that the Universe underwent this incredible exponential growth spurt called inflation, and when that epoch was over the Universe was "braking hard". Instead of increasing exponentially in size "indefinitely" (wonder what that would have led to?) the Universe settled down, expanding very moderately.

During the epoch of inflation (and, in fact, during the epoch of "braking hard" after the inflation), the redshift changed dramatically, simply because of how much the actual growth of the Universe changed in a short time.

We are now in an epoch of acceleration. However, the acceleration has not "picked up speed" yet, and it has not yet affected the size of the Universe very much. Therefore, we are located in a "redshift valley", where the redshift stays relatively constant over billions of light-years.

Is that correct?

Ann

https://en.wikipedia.org/wiki/Big_Bang#Inflation_and_baryogenesis wrote:Inflation stopped at around the 10⁻³³ to 10⁻³² seconds mark, with the universe's volume having increased by a factor of at least 10⁷⁸.

As the universe cooled, the rest energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years, the electrons and nuclei combined into atoms (mostly hydrogen), which were able to emit radiation. This relic radiation, which continued through space largely unimpeded, is known as the cosmic microwave background.[36]

https://en.wikipedia.org/wiki/Cosmic_microwave_background wrote:Cosmologists refer to the time period when neutral atoms first formed as the recombination epoch, and the event shortly afterwards when photons started to travel freely through space is referred to as photon decoupling. The photons that existed at the time of photon decoupling have been propagating ever since, though growing less energetic, since the expansion of space causes their wavelength to increase over time (and wavelength is inversely proportional to energy according to Planck's relation). This is the source of the alternative term relic radiation. The surface of last scattering refers to the set of points in space at the right distance from us so that we are now receiving photons originally emitted from those points at the time of photon decoupling.

johnnydeep wrote: ↑Sat Apr 09, 2022 7:17 pm Ann wrote above:

I think I "understand" - well, "expect" is a better word - the fact that the redshift will be much the same 7 billion years from now as it is today, because the redshift really increases "almost exponentially" the closer we get to the Big Bang, but from then it just keeps slowing down.

Isn't it the exact opposite? That is, since the expansion rate of the universe is increasing everywhere, so will the values of redshift over time. Or, stated another way: we have to wait less now for the wavelength of traveling light to increase by the same factor it did before.

But maybe I'm totally missing what the redshift value is measuring (despite reading and not entirely understanding) alter-ego's post above).

I think I "understand" - well, "expect" is a better word - the fact that the redshift will be much the same 7 billion years from now as it is today, because the redshift really increases "almost exponentially" the closer we get to the Big Bang, but from then it just keeps slowing down.

alter-ego wrote: ↑Sat Apr 09, 2022 2:48 am

MarkBour wrote: ↑Fri Apr 08, 2022 4:39 pm

Chris Peterson wrote: ↑Tue Apr 05, 2022 7:32 pm

How could they have been in flight for greater than the age of the Universe? If the redshift led to that conclusion, we'd revise the age of the Universe.

I think I'm questioning how rational the current interpretation of high-redshift data is.
If I look at this article: https://en.wikipedia.org/wiki/List_of_t ... al_objects
I see the following table:

Code: Select all

                                        Light travel 
       Name              Redshift (z)  distance (Gly)        Type                   Notes
----------------------  -------------  --------------   ---------------  --------------------------------
HD1                       z = 13.27        13.5         Galaxy           Formulative understanding
GN-z11                    z = 11.09        13.39        Galaxy           Confirmed galaxy
MACS1149-JD1              z = 9.11         13.26        Galaxy           Confirmed galaxy
EGSY8p7                   z = 8.68         13.23        Galaxy           Confirmed galaxy
A2744 YD4                 z = 8.38         13.20        Galaxy           Confirmed galaxy
MACS0416 Y1               z = 8.31         13.20        Galaxy           Confirmed galaxy
GRB 090423                z = 8.2          13.18        Gamma-ray burst
EGS-zs8-1                 z = 7.73         13.13        Galaxy           Confirmed galaxy
z7 GSD 3811               z = 7.66         13.11        Galaxy           Galaxy
J0313-1806                z = 7.64                      Quasar            
z8 GND 5296               z = 7.51         13.10        Galaxy           Confirmed galaxy
A1689-zD1                 z = 7.5          13.10        Galaxy           Galaxy
GS2_1406                  z = 7.452        13.095       Galaxy           Galaxy
SXDF-NB1006-2             z = 7.215        13.07        Galaxy           Galaxy
GN-108036                 z = 7.213        13.07        Galaxy           Galaxy
BDF-3299                  z = 7.109        13.05        Galaxy            
ULAS J1120+0641           z = 7.085        13.05        Quasar            
A1703 zD6                 z = 7.045        13.04        Galaxy            
BDF-521                   z = 7.008        13.04        Galaxy            
G2-1408                   z = 6.972        13.03        Galaxy            
IOK-1                     z = 6.964        13.03        Galaxy           Lyman-alpha emitter
LAE J095950.99+021219.1   z = 6.944        13.03        Galaxy           Lyman-alpha emitter — Faint galaxy

Starting at the bottom, a z of around 7 is interpreted as light from 13 billion years ago.
Moving to the top, it is quite non-linear, and we're up to the latest discoveries with z=11 and z=13 that are interpreted as light traveling just a "little" longer, 13.2 and 13.5 billion years.

~~~~~~~~~~
...

The question I would like to ask, is:

Okay, we just saw a photon from a galaxy that astronomers say travelled for 13 billion years and landed in our telescope. A little ways away from it, another photon from the same source happened to miss our telescope. Let that photon continue to fly through space for another 7 billion years. What will be its redshift then? Can anyone answer this?

Yes, I can answer that. You've picked an interesting redshift example. Viewing z = 7 (now) won't change much over 7 Gyr. The cosmic acceleration causes redshift minima to occur at different times, i.e. minima times are dependent on z. Several years ago, I had a sudden interest in redshift evolution over time for a fixed observer (e.g. the milky way). It culminated in the plot below. I find it very interesting as it reveals characteristics I wasn't expecting. I won't elaborate any further now, and although I can calculate your specific example, I interpolated between the closest two curves for this post.

Assuming you're adding 7 Gyr to present time, the answer is still close to 7. Note, dz/dt depends on when the first observation is made.
The two vertical lines mark now (13.72 Gyr) and +7Gyr (20.72 Gyr). The big arrows point to the two redshifts.
These calculations assume a flat spacetime. Also note, the evolution of the CMB redshift is plotted. It is the first electromagnetic radiation to fill the Universe. It was emitted roughly 380,000 years after the Big Bang, and therefore it's redshift (z ≈1100) cannot be exceeded by any visible object.
I'm expecting Webb to make discoveries pertinent to the onset and duration of the Dark Ages. I think the current thought is the first stars formed around 100 Myr after the BB (z~30)
 

Click to view full size image

MarkBour wrote: ↑Fri Apr 08, 2022 4:39 pm

Chris Peterson wrote: ↑Tue Apr 05, 2022 7:32 pm

MarkBour wrote: ↑Tue Apr 05, 2022 7:19 pm

How would those photons be different if they had been in flight for 20 billion years?

How could they have been in flight for greater than the age of the Universe? If the redshift led to that conclusion, we'd revise the age of the Universe.

I think I'm questioning how rational the current interpretation of high-redshift data is.
If I look at this article: https://en.wikipedia.org/wiki/List_of_t ... al_objects
I see the following table:

Code: Select all

                                        Light travel 
       Name              Redshift (z)  distance (Gly)        Type                   Notes
----------------------  -------------  --------------   ---------------  --------------------------------
HD1                       z = 13.27        13.5         Galaxy           Formulative understanding
GN-z11                    z = 11.09        13.39        Galaxy           Confirmed galaxy
MACS1149-JD1              z = 9.11         13.26        Galaxy           Confirmed galaxy
EGSY8p7                   z = 8.68         13.23        Galaxy           Confirmed galaxy
A2744 YD4                 z = 8.38         13.20        Galaxy           Confirmed galaxy
MACS0416 Y1               z = 8.31         13.20        Galaxy           Confirmed galaxy
GRB 090423                z = 8.2          13.18        Gamma-ray burst
EGS-zs8-1                 z = 7.73         13.13        Galaxy           Confirmed galaxy
z7 GSD 3811               z = 7.66         13.11        Galaxy           Galaxy
J0313-1806                z = 7.64                      Quasar            
z8 GND 5296               z = 7.51         13.10        Galaxy           Confirmed galaxy
A1689-zD1                 z = 7.5          13.10        Galaxy           Galaxy
GS2_1406                  z = 7.452        13.095       Galaxy           Galaxy
SXDF-NB1006-2             z = 7.215        13.07        Galaxy           Galaxy
GN-108036                 z = 7.213        13.07        Galaxy           Galaxy
BDF-3299                  z = 7.109        13.05        Galaxy            
ULAS J1120+0641           z = 7.085        13.05        Quasar            
A1703 zD6                 z = 7.045        13.04        Galaxy            
BDF-521                   z = 7.008        13.04        Galaxy            
G2-1408                   z = 6.972        13.03        Galaxy            
IOK-1                     z = 6.964        13.03        Galaxy           Lyman-alpha emitter
LAE J095950.99+021219.1   z = 6.944        13.03        Galaxy           Lyman-alpha emitter — Faint galaxy

Starting at the bottom, a z of around 7 is interpreted as light from 13 billion years ago.
Moving to the top, it is quite non-linear, and we're up to the latest discoveries with z=11 and z=13 that are interpreted as light traveling just a "little" longer, 13.2 and 13.5 billion years.

~~~~~~~~~~
...

The question I would like to ask, is:

Okay, we just saw a photon from a galaxy that astronomers say travelled for 13 billion years and landed in our telescope. A little ways away from it, another photon from the same source happened to miss our telescope. Let that photon continue to fly through space for another 7 billion years. What will be its redshift then? Can anyone answer this?

MarkBour wrote: ↑Fri Apr 08, 2022 4:39 pm I think I'm questioning how rational the current interpretation of high-redshift data is.

The question I would like to ask, is:

Okay, we just saw a photon from a galaxy that astronomers say travelled for 13 billion years and landed in our telescope. A little ways away from it, another photon from the same source happened to miss our telescope. Let that photon continue to fly through space for another 7 billion years. What will be its redshift then? Can anyone answer this?

Of course at this point I'm way out on a limb and the likelihood that I'm right in these assertions is very low.

Chris Peterson wrote: ↑Tue Apr 05, 2022 7:32 pm

MarkBour wrote: ↑Tue Apr 05, 2022 7:19 pm

Chris Peterson wrote: ↑Mon Apr 04, 2022 4:28 pm The CMB is defined by photons that have been in flight for 13.6 billion years. We see their origin in a shell around us.

How would those photons be different if they had been in flight for 20 billion years?

How could they have been in flight for greater than the age of the Universe? If the redshift led to that conclusion, we'd revise the age of the Universe.

                                        Light travel 
       Name              Redshift (z)  distance (Gly)        Type                   Notes
----------------------  -------------  --------------   ---------------  --------------------------------
HD1                       z = 13.27        13.5         Galaxy           Formulative understanding
GN-z11                    z = 11.09        13.39        Galaxy           Confirmed galaxy
MACS1149-JD1              z = 9.11         13.26        Galaxy           Confirmed galaxy
EGSY8p7                   z = 8.68         13.23        Galaxy           Confirmed galaxy
A2744 YD4                 z = 8.38         13.20        Galaxy           Confirmed galaxy
MACS0416 Y1               z = 8.31         13.20        Galaxy           Confirmed galaxy
GRB 090423                z = 8.2          13.18        Gamma-ray burst
EGS-zs8-1                 z = 7.73         13.13        Galaxy           Confirmed galaxy
z7 GSD 3811               z = 7.66         13.11        Galaxy           Galaxy
J0313-1806                z = 7.64                      Quasar            
z8 GND 5296               z = 7.51         13.10        Galaxy           Confirmed galaxy
A1689-zD1                 z = 7.5          13.10        Galaxy           Galaxy
GS2_1406                  z = 7.452        13.095       Galaxy           Galaxy
SXDF-NB1006-2             z = 7.215        13.07        Galaxy           Galaxy
GN-108036                 z = 7.213        13.07        Galaxy           Galaxy
BDF-3299                  z = 7.109        13.05        Galaxy            
ULAS J1120+0641           z = 7.085        13.05        Quasar            
A1703 zD6                 z = 7.045        13.04        Galaxy            
BDF-521                   z = 7.008        13.04        Galaxy            
G2-1408                   z = 6.972        13.03        Galaxy            
IOK-1                     z = 6.964        13.03        Galaxy           Lyman-alpha emitter
LAE J095950.99+021219.1   z = 6.944        13.03        Galaxy           Lyman-alpha emitter — Faint galaxy

Oh, z=<r>? That's just a little older than z=13. We'll calculate it at about 13.6 billion years.
Ummm . . . But we're surprised to find an apparently complex galaxy at such an early date after the big bang. We'll have to revise some of our numbers about the big bang a little. Or maybe we'll have to change our description of the cosmic inflation epoch to handle this.

• How old, and from what distance, is the radiation of the CMB, really?
• What opportunity does the JWST present for astronomy and cosmology? Will it continue to fill in a picture of cosmology that is already hard to change, or will it cause a revolution in our understanding?

MarkBour wrote: ↑Tue Apr 05, 2022 7:19 pm

Chris Peterson wrote: ↑Mon Apr 04, 2022 4:28 pm The CMB is defined by photons that have been in flight for 13.6 billion years. We see their origin in a shell around us.

How would those photons be different if they had been in flight for 20 billion years?