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Old 16th December 2020, 12:22 PM   #961
Mike Helland
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Originally Posted by Mike Helland View Post
Understood.

This GIF is from wikipedia, btw.

Your suggestion was to count the space from the center (the galaxy's starting position) to the left (the galaxy's current location) as traveled by the photon.. when clearly the photon was never in that half of the animation.

The lookback time is generally taken as the photon's travel time, not the comoving distance.

Agreed?
FWIW, if I change the expanding models so the photon does go with Hubble flow:

Code:
    this.photon.x += c + this.photon.x * this.H / 1000
    for (var i = 0; i < this.targets.length; i++) {
        this.targets[i].x += this.targets[i].x * this.H / 1000
    }
This model now produces identical results to my model:

Code:
    this.photon.x += c - this.photon.x * this.H / 1000
But... done this way, the expanding model misses the z targets.
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Old 16th December 2020, 12:29 PM   #962
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I'm enjoying this thread (just sayin').
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Old 16th December 2020, 12:29 PM   #963
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Originally Posted by Mike Helland View Post
Understood.

This GIF is from wikipedia, btw.

Your suggestion was to count the space from the center (the galaxy's starting position) to the left (the galaxy's current location) as traveled by the photon.. when clearly the photon was never in that half of the animation.
Wasn't it? It wasn't on that part of the screen, but the space isn't the screen. The space is animated to move across the screen. But space doesn't actually move, that's just one way to try to visualize it, and it's not the only or even necessarily best way to do so. The photon still had to pass through all the space that exists between the two galaxies, even if that space wasn't all as big at the start as it was at the end. So it's still a matter of how you want to define things.

I think one of the conceptual problems you're having here is the distinction between what's known as extrinsic geometry and intrinsic geometry. I'll try to explain with an example. Consider the surface of a sphere. It's a 2D space, but it's not Euclidean. It's curved. Triangles on the surface of the sphere have angles that add up to more than 180 degrees. We can visualize the curvature of this 2D surface quite easily in terms of how the 2D surface is embedded into our 3D space. Our 3D space is Euclidean, but the embedded 2D space is not. That curvature of 2D space inside the 3D space it's embedded in is extrinsic geometry. We can measure properties of the curvature of this space in terms of things like the radius of the sphere. But the radius of the sphere isn't within the 2D surface, it's outside the surface. That's why this is an "extrinsic" picture.

But now imagine that some entity lives on this 2D surface, and cannot sense or interact with anything outside the 2D surface. This entity could still determine that his space was curved. How? Again, triangle corners don't add up to 180 degrees. By looking at how the angle of triangles varies with the size of the triangle, he can even discover how curved his space is. In fact, everything we know about the curvature of this space by looking at it in 3D, this entity can determine from within the space itself. The math can be harder and less obvious, but everything is still there, embedded within the properties of the space itself without reference to any higher dimensions. This is intrinsic geometry.

I think you're stuck on viewing expanding space as an extrinsic geometry problem. If space is expanding, there must be something it's expanding into, even if it's not ordinary space as we know it. Thus it feels like space itself has some sort of velocity.

But here's the thing: none of our laws of physics make any reference to extrinsic geometry. Everything is only dependent on intrinsic geometry. The higher dimension we might try to visualize in order to understand it simply doesn't exist from any practical viewpoint.

Quote:
The lookback time is generally taken as the photon's travel time, not the comoving distance.

Agreed?
Time is not distance, yes, I agree with that.
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Old 16th December 2020, 12:31 PM   #964
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Originally Posted by Mike Helland View Post
FWIW, if I change the expanding models so the photon does go with Hubble flow:

Code:
    this.photon.x += c + this.photon.x * this.H / 1000
    for (var i = 0; i < this.targets.length; i++) {
        this.targets[i].x += this.targets[i].x * this.H / 1000
    }
This model now produces identical results to my model:

Code:
    this.photon.x += c - this.photon.x * this.H / 1000
But... done this way, the expanding model misses the z targets.
When the photon moves with the Hubble flow, I either get 0 redshifts... or negative redshifts... blue shifts... because the speed of the photon is increasing.
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Old 16th December 2020, 12:38 PM   #965
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Originally Posted by Ziggurat View Post
I think you're stuck on viewing expanding space as an extrinsic geometry problem. If space is expanding, there must be something it's expanding into, even if it's not ordinary space as we know it. Thus it feels like space itself has some sort of velocity.

I used the model of expanding space that I did because it predicted the expected z's, lookback, and comoving distances I got from Wolfram Alpha.

I can adjust the model so the photon is included in the Hubble flow... though I'm not sure that's right, and even though it predicts the same times to targets as my model, it didn't predict the right z's.

If the big bang is right, that's cool, I'm not concerned at all about what space is expanding into, or what happened before the big bang.

I'm just looking at it like.... I think we missed something fundamental down the line. Instead of putting the entire universe in motion away from an observer, a photon could just have a finite range of distance it can travel.
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Old 16th December 2020, 05:16 PM   #966
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Originally Posted by Mike Helland View Post
I used the model of expanding space that I did because it predicted the expected z's, lookback, and comoving distances I got from Wolfram Alpha.

I can adjust the model so the photon is included in the Hubble flow... though I'm not sure that's right, and even though it predicts the same times to targets as my model, it didn't predict the right z's.

If the big bang is right, that's cool, I'm not concerned at all about what space is expanding into, or what happened before the big bang.

I'm just looking at it like.... I think we missed something fundamental down the line. Instead of putting the entire universe in motion away from an observer, a photon could just have a finite range of distance it can travel.
So, I changed the model, this does increase the speed of the photon, as you suggest, and in doing so elongates the wavelength, producing redshifts.

When graphed, this matches the hypothesis I've been testing. Exactly.


Code:
    this.photon.dx = c + this.photon.x * this.H / 1000
    this.photon.x += this.photon.dx
    this.photon.w = (this.photon.dx * 299792460 / this.photon.f_start) 
    this.photon.f = 299792460 / this.photon.w
Which I guess solves something of a mystery I had... I assumed that my expanding models and decelerating models would be analogous.

I was surprised when they weren't. Now they are.

My intuition was basically that if the photon went with the Hubble flow, that would result in a static model. Huh.
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Old 16th December 2020, 08:49 PM   #967
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Originally Posted by Mike Helland View Post
My intuition was basically that if the photon went with the Hubble flow, that would result in a static model. Huh.
Actually, that's almost right.

Here are four models

(0)
v_target = 0
v_light = c

(1)
v_target = H * start
v_light = c

(2)
v_target = H * start
v_light = c + H * x

(3)
v_target = H * proper
v_light = c + H * x

Model 0, blue, is a simple static universe.

Model 1, grey, is what I had been using for an expanding universe, the targets move away at H*D, where D is the starting distance. Each target moves according to its starting distance at all times.

Model 2, purple, is what I feel you had suggested, where the photon moves with the Hubble flow. This shows some expansion, but you can see it's much closer to a static model.

Model 3, light green, the photon is moving with the Hubble flow, and also the targets are getting faster as they get farther away. Their recessional velocity is calculated based on their proper distance, not their starting distance, so it increases.



I added these to the test page for comparison.

https://mikehelland.github.io/hubbles-law/test.htm

My model matches Model 3 in all views. That's pretty unexpected.
What I found is, Model 3 and my decelerating photons hypothesis are perfect matches.
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Old 16th December 2020, 09:26 PM   #968
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Originally Posted by Mike Helland View Post
(2)
v_target = H * start
v_light = c + H * x
...
Model 2, purple, is what I feel you had suggested, where the photon moves with the Hubble flow. This shows some expansion, but you can see it's much closer to a static model.
Model 2 is wrong. When the photon catches up with the target, the relative speed of the light compared to the target is c + H * (x - start), but since x is now > start, the light is moving faster than c as viewed locally by the target. Thatís a no-no, and is not what I suggested.

Quote:
Model 3, light green, the photon is moving with the Hubble flow, and also the targets are getting faster as they get farther away. Their recessional velocity is calculated based on their proper distance, not their starting distance, so it increases.
Assuming proper = x, then this model has the correct relationship between target proper velocity and photon proper velocity, since the target will always see the photons at their location as moving at c relative to them.

If proper means something else, then model 3 is wrong.
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Old 16th December 2020, 09:33 PM   #969
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Originally Posted by Ziggurat View Post
Model 2 is wrong. When the photon catches up with the target, the relative speed of the light compared to the target is c + H * (x - start), but since x is now > start, the light is moving faster than c as viewed locally by the target. Thatís a no-no, and is not what I suggested.



Assuming proper = x, then this model has the correct relationship between target proper velocity and photon proper velocity, since the target will always see the photons at their location as moving at c relative to them.

If proper means something else, then model 3 is wrong.
Interesting, yes, that's what it means.

I can see even in my post above I accidentally copy and pasted a model using "x" rather than "start", so this was some pure dumb luck on my part. A lot of patience and guidance on your part.
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Old 17th December 2020, 07:13 AM   #970
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Originally Posted by Ziggurat View Post
Assuming proper = x, then this model has the correct relationship between target proper velocity and photon proper velocity, since the target will always see the photons at their location as moving at c relative to them.
So, the standard cosmological model, except we're calling cosmological expansion something else to avoid copyright infringement?
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Old 17th December 2020, 08:27 AM   #971
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Originally Posted by Reformed Offlian View Post
So, the standard cosmological model, except we're calling cosmological expansion something else to avoid copyright infringement?
I'm sidestepping the issue of the rate of expansion for the moment, to focus on the question of what light does when space is expanding. So for example, the separation distance could expand linearly over time or exponentially over time (or even something else), but either way light moves through expanding space such that its local velocity is still always c.
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Old 17th December 2020, 08:54 AM   #972
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Originally Posted by Ziggurat View Post
I'm sidestepping the issue of the rate of expansion for the moment, to focus on the question of what light does when space is expanding. So for example, the separation distance could expand linearly over time or exponentially over time (or even something else), but either way light moves through expanding space such that its local velocity is still always c.
Right. I wasn't @'ing you. I was pointing out that Mike seems to be slouching towards the one thesis he professes to despise in this thread: that space is expanding. I hadn't considered ATM models of said expansion.
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Old 17th December 2020, 09:48 AM   #973
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New article: "Astronomers Get Their Wish, and a Cosmic Crisis Gets Worse"

https://www.quantamagazine.org/astro...orse-20201217/
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Old 17th December 2020, 09:50 AM   #974
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Originally Posted by Reformed Offlian View Post
Right. I wasn't @'ing you. I was pointing out that Mike seems to be slouching towards the one thesis he professes to despise in this thread: that space is expanding. I hadn't considered ATM models of said expansion.
I think he just means we were talking about an expanding model with a constant expansion rate (circa 1970's).
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Old 17th December 2020, 10:52 AM   #975
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FWIW, this question would up being quite popular:

https://old.reddit.com/r/askscience/...billion_light/

Thanks for pointing that out (a couple times), Ziggurat.
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Old 2nd January 2021, 05:28 PM   #976
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Originally Posted by Mike Helland View Post
FWIW, this question would up being quite popular:

https://old.reddit.com/r/askscience/...billion_light/

Thanks for pointing that out (a couple times), Ziggurat.
So I made a write up on ways to model an expanding universe. Again, if you want acknowledgement for your help, let me know.

https://mikehelland.github.io/hubble..._expansion.htm

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Old 7th January 2021, 04:55 PM   #977
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Originally Posted by Mike Helland View Post
FWIW, this question would up being quite popular:

https://old.reddit.com/r/askscience/...billion_light/
271 replies. It looks like the top posts on r/askscience get at least three or four times as many replies, and usually up in the thousands. On the really popular subreddits, it'd be in the tens of thousands. I wouldn't call this "quite popular", even by r/askscience standards.

Also, "quite popular on reddit" isn't really an endorsement of anything. There's some very stupid stuff (and some very repugnant stuff) that's "quite popular" on reddit.
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Old 13th January 2021, 04:19 PM   #978
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Originally Posted by Mike Helland View Post
So I made a write up on ways to model an expanding universe. Again, if you want acknowledgement for your help, let me know.

https://mikehelland.github.io/hubble..._expansion.htm
A nice bit of graph producing code.
A pity that the decelerating photon hypothesis is obviously invalid as in your immediate fatal flaws list. You can add E-mc^2 and fusion powering stars. Change c and the physics of stars changes. Change it too much and stars cannot exist. There is the problem that decelerating photons cannot produce Hubble's law. The v in Hubble's law is the speed of galaxies as measured by their redshift, not the speed of the light they emit.
A small error. Tired light is not decelerating photons. It is photons travelling at c and changing energy so that their wavelength changes.

Followed by ATM attempts to explain away the flaws with bad science and the error of false dichotomy (the mainstream being wrong just means that one of many ATM ideas might be correct).
An unsupported "Yet these new observations pose no threat to the decelerating photon model" assertion. How does a model with only decelerating photons explain the Hubble constant tension? The CMB anomalies? "Mature" galaxies in the early universe? The objects that seem to be bigger than mainstream cosmology predicts?
The measured properties of the cosmic microwave background show that it has a cosmological origin.
A "Newton's First Law of Motion" section that ignores the other laws. These decelerating photons will also obey F=ma. But photons have no mass. The decelerating photons model probably predicts that photons will travel at an infinite speed .
A "Special Relativity" section with the obviously invalid act of changing the speed of photons (see above) and no special relativity!
A "Conservation of Energy" section. Your decelerating photons will not lose energy or even redshift.
A "Redshifts indicate an expanding universe" repeating the error that decelerating photons do not redshift.
A "The CMB indicates a hot past" section starting with a chart quote mining Thermal (non-microwave background) temperature predictions. These are not CMB temperatures as the fact that the CMB is microwaves makes obvious.
A "Age of the universe" section starting with a "galaxies must be "young" in the early universe" story. A long list of irrelevant citations.
A "Size of the universe" section about the sizes of objects in the universe basically just listing the largest ones.

A "Tolman Surface Brightness Test" section ignorant about the test and the result. Tolman surface brightness test
Quote:
To date, the best investigation of the relationship between surface brightness and redshift was carried out using the 10 m Keck telescope to measure nearly a thousand galaxies' redshifts and the 2.4 m Hubble Space Telescope to measure those galaxies' surface brightness.[1] The exponent found is not 4 as expected in the simplest expanding model, but 2.6 or 3.4, depending on the frequency band. The authors summarize:
"We show that this is precisely the range expected from the evolutionary models of Bruzual & Charlot. We conclude that the Tolman surface brightness test is consistent with the reality of the expansion."
What is not quoted is the test debunks tired light theories.
The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies
Quote:
We conclude that the Tolman surface brightness test is consistent with the reality of the expansion. We have also used the high-redshift HST data to test the ``tired light'' speculation for a non-expansion model for the redshift. The HST data rule out the ``tired light'' model at a significance level of better than 10 sigma.
The section ends with a "The decelerating photon hypothesis predicts one fewer factor than the expanding universe, matching observations" fantasy. All the section has is an irrelevant animation.

A "Time Dilation in Supernovae Light Curves" section. Time dilation is special relativity not anything to do with the Tolman surface brightness test. Citing a seemingly crank 2004 conference presentation (the only publication by the author who lists no affiliation) is dubious and irrelevant.
A "Comparison to other models" section that emphasizes the imaginary nature of the decelerating photon hypothesis with unsupported assertions.
A "Photons" section starting with it is "not a quantum theory, nor is it a relativistic theory" when the universe and photons are quantum and relativistic ! Over a century of experiments have supported this. A story and irrelevant code follow. A bit of invalid fantasy finishes the section. A photon enters a telescope's eyepiece at a speed less than c. It magically gains energy to become a photon moving at c because he want it to (why not greater than c!).

A "Tests" chapter with "tests" for this invalid hypothesis.
A "Conclusion" section.
Redshift (Hubble's law) just says that the universe is expanding and sets a limit to the age of the universe. Redshift does not
  • give the size of the inverse.
  • say "universe inflated in the first nanosecond"
  • show the universe is "dominated by dark matter and dark energy".
  • show the universe is "currently accelerating".
A "Or we could assume the redshifts are themselves a new feature of the universe" error when this is not his hypothesis.
Ignorance that dark energy has never been observed (or a fantasy we have to have a flask of dark energy in labs). Dark energy exists because we have observed that the expansion of the universe accelerated.

Last edited by Reality Check; 13th January 2021 at 06:17 PM.
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Old 14th January 2021, 06:15 AM   #979
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Hello,

Thanks for looking at the paper:

https://mikehelland.github.io/hubbles-law/

Originally Posted by Reality Check View Post
Change c and the physics of stars changes. Change it too much and stars cannot exist.
It's not c itself that changes (like in VSL) but that a photon loses speed after millions of years of travel.

That wouldn't be true in a star.

Quote:
There is the problem that decelerating photons cannot produce Hubble's law. The v in Hubble's law is the speed of galaxies as measured by their redshift, not the speed of the light they emit.
Well, right. That's the hypothesis.

Standard model:

Code:
v_light = c  
v_galaxies = HD
My hypothesis is:

Code:
v_light = c - HD
v_galaxies = 0
Both models produce the same delays in travel and same z's.

Quote:
A small error. Tired light is not decelerating photons. It is photons travelling at c and changing energy so that their wavelength changes.
Couldn't agree more.

Quote:
How does a model with only decelerating photons explain the Hubble constant tension?
Finally, it is the measurements of the CMB that aren't fitting measurements of Hubble's constant that is at the source of the Hubble tension. Supernovae based measurements report 74 km/s/Mpc[1], parallax measurements report 73.2 [3], and infrared surface brightness fluctuation measurements report 73.3 km/s/Mpc[3], while CMB based measurements report 67.4 km/s/Mpc[2]. If the CMB is not an ancient fireball, there is no tension.

https://mikehelland.github.io/hubbles-law/#sources

Quote:
The CMB anomalies?
In the Milky Way galaxy, our sun is located slightly to the north of the galactic disk.



That means, there are more stars of our own galaxy to the south than there are to the north. And the CMB's southern hemisphere is warmer than the northern hemisphere. The CMB may be the heat of our own galaxy.

That's a better explanation than the big bang theory has available.

Quote:
"Mature" galaxies in the early universe? The objects that seem to be bigger than mainstream cosmology predicts?
If the universe is not expanding, then in the past, it wasn't smaller, and therefore, there was no "beginning" to speak of.

If there was no known beginning there is no known age, therefore, there are no age limits for things or size limits for how big they would have grown.

Our galaxy is supposedly nearly as old as the universe, but 12 billion years in the past, there are galaxies exactly like ours.

Whoops.


Quote:
The measured properties of the cosmic microwave background show that it has a cosmological origin.
Which properties are those?

Quote:
Your decelerating photons will not lose energy or even redshift.
Velocity of wave

v=frequency * wavelength

Energy of a photon

E=hf

A drop in energy, frequency, and speed all work mathematically and produce the same z's as stretched wavelengths.

Quote:
A "Time Dilation in Supernovae Light Curves" section. Time dilation is special relativity
Not in this context.

It's 20 day supernova events appearing to last 20+ days due to the expansion of the universe.
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Old 14th January 2021, 06:52 AM   #980
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Originally Posted by Mike Helland View Post
The CMB may be the heat of our own galaxy.
It is not. Nothing in our galaxy could have such a perfect spectrum, and anything that did would occlude everything behind it such as other galaxies, which the CMB obviously doesn't. We have been over this before.
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Old 14th January 2021, 07:00 AM   #981
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Since originally posting this (only two months!!), two more methods of measuring Hubble's constant have come out. One based on parallax (GAIA) and one based on infrared surface brightness fluctuations.

That brings us to this.


Hubble's constant
74.0 km/s/Mpc[1] Cepheids
73.2 km/s/Mpc[3] Parallax
73.3 km/s/Mpc[4] Infrared SB Fluctuation
67.4 km/s/Mpc[2] CMB

Which of these is not like the other?

1. A. G. Riess et al. "Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics Beyond LambdaCDM" , (2019).
2. N. Aghanim et al., “Planck 2018 results. VI. Cosmological parameters, (2018)
3. A. G. Riess et al., arXiv:2012.08534 [astro-ph.CO] ApJ., 116, 1009 (2020).
4. Blakeslee, J.P. et al,. "The Hubble Constant from Infrared Surface Brightness Fluctuation Distances" arXiv:2101.02221 (2021)

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Old 14th January 2021, 07:03 AM   #982
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Originally Posted by Ziggurat View Post
It is not. Nothing in our galaxy could have such a perfect spectrum...
I'm not saying it's something in our galaxy, am I?

It's the predicted and observed minimum temperature of the galaxy itself.

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anything that did would occlude everything behind it such as other galaxies, which the CMB obviously doesn't. We have been over this before.
Infrared light doesn't occlude optical light though... unless I'm missing something.

We've talked about the CMB before, but I don't recall you mentioning this occlusion bit.
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Old 14th January 2021, 07:10 AM   #983
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Originally Posted by Mike Helland View Post
If the universe is not expanding, then in the past, it wasn't smaller, and therefore, there was no "beginning" to speak of.

If there was no known beginning there is no known age, therefore, there are no age limits for things or size limits for how big they would have grown.
It's quite common for people who don't actually know the science to seize on a small problem, come up with a radical solution to it, and not notice that this radical solution actually creates far bigger problems than it solves.

If the universe had no beginning, then how can something like the sun exist? The sun burns up hydrogen. It's a one-way process that cannot continue forever. Not only are you not conserving energy, you're not even conserving matter.

The big bang theory has a problem in that we don't know what triggered the big bang in the first place. But here's the thing: the conditions of the early universe were sufficiently extreme that we cannot expect our current theories to work under those conditions. That means that there's space there for stuff we don't understand without our current theories being totally wrong.

Your model offers no such possibility. If the universe is as it always was, then conditions were never outside of what our current theories should be able to model accurately, and seem to be able to. But you still require our current theories to break completely. That... doesn't work.

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Our galaxy is supposedly nearly as old as the universe, but 12 billion years in the past, there are galaxies exactly like ours.
Exactly like ours? No. Among other things, we don't have nearly the sensitivity to make any such claim. For example, we cannot measure the average metalicity of stars in a galaxy 12 billion light years away.
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Old 14th January 2021, 07:15 AM   #984
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Originally Posted by Mike Helland View Post
I'm not saying it's something in our galaxy, am I?
It must be close by if it's from our galaxy's heat.

The CMB cannot be in front of distant galaxies, again because of occlusion. If it is not in front of distant galaxies, it cannot be from our galaxy's heat.

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It's the predicted and observed minimum temperature of the galaxy itself.
Only approximately, and as I keep pointing out and you keep ignoring the implications of, not the predicted or observed line shape of anything in our galaxy.

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Infrared light doesn't occlude optical light though... unless I'm missing something.
You think optical light is the only thing we can pick up from distant galaxies? No, we pick up far more than that.

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We've talked about the CMB before, but I don't recall you mentioning this occlusion bit.
Your theories are wrong on so many levels, why are you surprised that we're talking about a new one today?
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Old 14th January 2021, 07:26 AM   #985
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Originally Posted by Ziggurat View Post
The CMB cannot be in front of distant galaxies, again because of occlusion. If it is not in front of distant galaxies, it cannot be from our galaxy's heat.
Ok.... but doesn't that only apply because, according to standard theory, 14 billion years ago the CMB was actually a million degrees?

Say you and I are talking to each other across from a camp fire. If it was a small fire, with flames about a foot high, we could talk. If it was a big fire, flames 6 feet high, we wouldn't really be able to see other through the flames.

The standard model says the CMB was once a 30 foot tall fire, but that was so long ago, the heat reaches us at 2.7 Kelvin.

Anything on the other side of that fire can't be seen because the fire was opaque back then.

If there was no 30 foot tall fire in the past, but a galaxy at 2.7 K, there is no opacity to work against.

In other words, if you put on an alien's advanced infrared night vision goggles, the whole galaxy should have a minimum temperature.

If we sent a probe to the south of the galactic disk in the Milky Way, I think the south would be cooler and the north would be warmer.

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Only approximately, and as I keep pointing out and you keep ignoring the implications of, not the predicted or observed line shape of anything in our galaxy.
Again, I'm not talking about something "in" our galaxy.
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Old 14th January 2021, 07:32 AM   #986
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Originally Posted by Ziggurat View Post
Only approximately
"Only approximately."



 
Hubble's constant
74.0 km/s/Mpc Cepheids
73.2 km/s/Mpc Parallax
73.3 km/s/Mpc Infrared SB Fluctuation
67.4 km/s/Mpc CMB
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Old 14th January 2021, 07:41 AM   #987
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Originally Posted by Mike Helland View Post
"Only approximately."
Yes. When all you have to hang your hat on is the temperature, then the accuracy of the temperature is paramount. And that's all you're able to appeal to. And it's particularly peculiar in your case, since you're simultaneously using a prediction for temperature within our galaxy while claiming the source is outside our galaxy. That doesn't work, for reasons which should be obvious and yet you missed them anyways.

But as I keep reminding you and you keep forgetting, the important part of the big bang prediction for the CMB isn't the temperature, but the line shape. And that isn't just approximately a black body curve. It's a perfect black body curve to within our very good measurement resolution. You can't get around that, so you keep pretending it's not an issue. It is.
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Old 14th January 2021, 07:47 AM   #988
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Originally Posted by Ziggurat View Post
Yes. When all you have to hang your hat on is the temperature, then the accuracy of the temperature is paramount. And that's all you're able to appeal to. And it's particularly peculiar in your case, since you're simultaneously using a prediction for temperature within our galaxy while claiming the source is outside our galaxy. That doesn't work, for reasons which should be obvious and yet you missed them anyways.

But as I keep reminding you and you keep forgetting, the important part of the big bang prediction for the CMB isn't the temperature, but the line shape. And that isn't just approximately a black body curve. It's a perfect black body curve to within our very good measurement resolution. You can't get around that, so you keep pretending it's not an issue. It is.
The black body spectrum indicates that it's in equilibrium with it's environment, right?
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Old 14th January 2021, 07:52 AM   #989
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Originally Posted by Mike Helland View Post
Ok.... but doesn't that only apply because, according to standard theory, 14 billion years ago the CMB was actually a million degrees?
No. If the source of the CMB is very far away (as it must be), then regardless of what it is, it cannot be heated to that temperature by OUR galaxy, because the amount of light from OUR galaxy would not heat such a distant source to even close to 2.7K. It wouldn't even heat such a distant source to 1 millikelvin.

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Say you and I are talking to each other across from a camp fire. If it was a small fire, with flames about a foot high, we could talk. If it was a big fire, flames 6 feet high, we wouldn't really be able to see other through the flames.

The standard model says the CMB was once a 30 foot tall fire, but that was so long ago, the heat reaches us at 2.7 Kelvin.

Anything on the other side of that fire can't be seen because the fire was opaque back then.

If there was no 30 foot tall fire in the past, but a galaxy at 2.7 K, there is no opacity to work against.
No. The CMB light is microwave black body. That means microwaves and radio waves cannot reach us from anything behind the CMB. Doesn't matter if it's close and emitting light that's not red shifted, or far and emitting light that is red shifted. Light which is microwave/radio when it reaches us cannot have been emitted from behind the CMB, because it will have been in the CMB emission range when it passed through the CMB, even if both are different when it reaches us.

We can detect microwaves from other galaxies.

Quote:
In other words, if you put on an alien's advanced infrared night vision goggles, the whole galaxy should have a minimum temperature.

If we sent a probe to the south of the galactic disk in the Milky Way, I think the south would be cooler and the north would be warmer.



Again, I'm not talking about something "in" our galaxy.
You are contradicting yourself here. Can you see why?

Perhaps not.
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Old 14th January 2021, 07:53 AM   #990
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Originally Posted by Mike Helland View Post
The black body spectrum indicates that it's in equilibrium with it's environment, right?
Wrong. The black body spectrum indicates that it's a perfect absorber.
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Old 14th January 2021, 07:59 AM   #991
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Originally Posted by Ziggurat View Post
No. If the source of the CMB is very far away (as it must be), then regardless of what it is, it cannot be heated to that temperature by OUR galaxy, because the amount of light from OUR galaxy would not heat such a distant source to even close to 2.7K. It wouldn't even heat such a distant source to 1 millikelvin.
Uh, yes... ?

Is that what you think I'm talking about?

*Edit* I don't think we're talking about the same thing. The temperature of our galaxy can't heat the CMB if the CMB is the heat of our galaxy.

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You are contradicting yourself here. Can you see why?
Why?

AFACT, we're both saying there is no where in our galaxy you could be with a thermometer and read less than 2.7 K.

Agreed?

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Old 14th January 2021, 08:07 AM   #992
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Originally Posted by Ziggurat View Post
No. The CMB light is microwave black body. That means microwaves and radio waves cannot reach us from anything behind the CMB. Doesn't matter if it's close and emitting light that's not red shifted, or far and emitting light that is red shifted. Light which is microwave/radio when it reaches us cannot have been emitted from behind the CMB, because it will have been in the CMB emission range when it passed through the CMB, even if both are different when it reaches us.

We can detect microwaves from other galaxies.

If my neighbor has a HAM radio, that doesn't block out all my radio stations.
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Old 14th January 2021, 08:12 AM   #993
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Originally Posted by Mike Helland View Post
In other words, if you put on an alien's advanced infrared night vision goggles, the whole galaxy should have a minimum temperature.
This is stupid. Infrared wavelengths are infrared wavelengths. Once you can detect them, you can detect them. There's not some advanced level of detecting the real infrared, out there waiting to be discovered.
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Old 14th January 2021, 08:15 AM   #994
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Originally Posted by theprestige View Post
This is stupid. Infrared wavelengths are infrared wavelengths. Once you can detect them, you can detect them. There's not some advanced level of detecting the real infrared, out there waiting to be discovered.
Do we have wearable goggles that can detect the difference between, say 1.5 K and 2.5 K?
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Old 14th January 2021, 08:16 AM   #995
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Originally Posted by Mike Helland View Post
If my neighbor has a HAM radio, that doesn't block out all my radio stations.
I like analogies.

What if all the neighboring towns and cities put up a wall of black-body radiation in the radio spectrum?
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Old 14th January 2021, 08:22 AM   #996
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Originally Posted by Mike Helland View Post
Do we have wearable goggles that can detect the difference between, say 1.5 K and 2.5 K?
This is stupid. Why does it have to be wearable goggles? Why can't it be pintle-mounted goggles like those coin-operated viewers you see at tourist attractions sometimes? Why can't it be a backyard telescope? Why can't it be an array of telescopes?

Why can't it be any apparatus at all, so long as it detects infrared wavelengths?

Are you seriously positing that the Milky Way must be emitting magical infrared wavelengths that can only be detected by certain miniaturized infrared detectors assembled in a particular package for a particular anatomy? Does it have to be goggles? Can it be doggles?

If it's alien goggles, can we even wear them and see what needs to be seen?
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Old 14th January 2021, 08:22 AM   #997
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Originally Posted by theprestige View Post
I like analogies.

What if all the neighboring towns and cities put up a wall of black-body radiation in the radio spectrum?
By that do you mean broadcast on every frequency?

I suppose that means if they had a powerful enough signal, they could block all your radio stations.
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Old 14th January 2021, 08:25 AM   #998
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Originally Posted by theprestige View Post
This is stupid.
I agree.

It was just a thought experiment.

Let's say you leave the galaxy, and you're in intergalactic space, and you've got Jordi's visor from Star Trek (you didn't bring your desktop equipment).

That's all I was getting at.

Calm down.

Look, space can be expanding.

I'm just skeptical.
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Old 14th January 2021, 08:42 AM   #999
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Originally Posted by Mike Helland View Post
AFACT, we're both saying there is no where in our galaxy you could be with a thermometer and read less than 2.7 K.

Agreed?
That's not the question. Our galaxy is only going to heat stuff to something in that temperature range if it's within our galaxy. But you're saying you aren't arguing that the source is within our galaxy. If it's not within our galaxy, our galaxy wouldn't heat it to within that range.
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Old 14th January 2021, 08:45 AM   #1000
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Originally Posted by Mike Helland View Post
If my neighbor has a HAM radio, that doesn't block out all my radio stations.
As a matter of fact, if you surrounded your house on all sides with a bunch of radio antennas, that WOULD interfere with your reception inside. That's essentially how a Faraday cage works.

You won't notice it from one radio because one antenna has too small a cross section to make much difference, and the reception you perceive after it's decoded into sound doesn't directly correspond to radio signal intensity anyways.
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