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24th June 2023, 11:00 AM  #241 
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Oh, and I’ll just add this, in the absurdly unlikely event that 30 orders of magnitude is insufficient: we observe a CMB dipole. The Gibbons Hawking radiation has no dipole and the same temperature is observed by all freefalling observers.

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24th June 2023, 11:00 AM  #242 
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Caption from and old New Yorker cartoon  Why am I shouting? Because I'm wrong!" 

24th June 2023, 11:04 AM  #243 
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"As long as it is admitted that the law may be diverted from its true purpose  that it may violate property instead of protecting it  then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and allabsorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious."  Bastiat, The Law 

24th June 2023, 11:05 AM  #244 
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Yes, but he’d have to incorporate it in a way that is physically correct, not in any way he sees fit, and I have no idea where he’s going with this. Anyway, we genuinely have no idea how much of the universe lies outside our observable region, but what lies outside the observable universe can have no influence on what observe  by definition.

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24th June 2023, 11:07 AM  #245 
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24th June 2023, 11:17 AM  #246 
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It's about the difference between the radius of a smallish black hole and the radius of the universe.
The 30 orders of magnitude figure seems to be for the "future" horizon in an expanding universe. https://physics.stackexchange.com/qu...sitterhorizon
Quote:

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24th June 2023, 11:18 AM  #247 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

24th June 2023, 11:30 AM  #248 
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24th June 2023, 11:32 AM  #249 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

24th June 2023, 11:41 AM  #250 
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24th June 2023, 11:50 AM  #251 
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That doesn't answer the question.
ETA, FWIW, I don't know for sure. I think that all the mass in the system is put at the origin. But then, I think, you place a test particle in there and compute some geodesics, which would require the particle's initial momentum, so I think the mass is included there? 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

24th June 2023, 01:55 PM  #252 
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FWIW, here's my version of what's developed here:
https://mikehelland.github.io/hubbleslaw/ We're at the bottom part now. The sections are: Observation Conjecture An ad hoc hypothesis Compared to data A geometrical solution Cosmological implications The CMB Other cosmological phenomena 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

24th June 2023, 02:51 PM  #253 
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30 orders of magnitude is the discrepancy between the observed CMB temperature and the temperature of cosmic GibbonsHawking radiation in a de Sitter Universe expanding with H=~2.2e18 s^{1} =~ 70km s^{1}Mpc^{1}.
Quote:

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24th June 2023, 02:55 PM  #254 
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25th June 2023, 02:40 AM  #255 
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Couldn't tell ya.
But reading Einstein and de Sitter's 1917 papers gives the impression that they were not really concerned with a theory of the universe, but how GR acts at the boundary conditions, out at infinity. I thought one of the scenarios considered back then was putting all the mass out at infinity. Though I can't find the reference, so I probably imagined it. 
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25th June 2023, 04:21 AM  #256 
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That figures.
Quote:
Quote:

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25th June 2023, 04:25 AM  #257 
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25th June 2023, 04:30 AM  #258 
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25th June 2023, 09:10 AM  #259 
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The issue seems to be what happens when time approaches infinity or negative infinity.
LCDM/FLRW and its quasiabsolute cosmic time is incompatible with the equivalence principle and not totally relativistic. De Sitter's system B is entirely relative, compatible with EEP, and has time dilation and redshift at a distance from the observer. If my model could be rejected because you thought it was incompatible with relativity, then so should LCDM/FLRW. De Sitter's system B is safe though. 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 10:20 AM  #260 
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I stand corrected.
Confirming hecd2's diagnosis, the author and sole proponent of Helland physics wrote: As has already been explained within just the past couple of days:

25th June 2023, 11:14 AM  #261 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 11:37 AM  #262 
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25th June 2023, 12:14 PM  #263 
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The author and sole proponent of Helland physics continues to supply evidence in support of hecd2's observation that he doesn't have, "by about 30 orders of magnitude, the mathematical chops to understand" any serious discussion of general relativity and cosmology:
As I explained two days ago: So what I wrote is quite true: "FLRW is entirely compatible with general relativity, as is the "cosmic time" coordinate that is customarily used when describing an FLRW model." But Mike Helland "dunno" that. Helland physics is cargo cult pseudoscience. Its author and sole proponent searches the WorldWide Web for anything he can find that can be misinterpreted to support his own misconceptions. He doesn't understand what he reads, but that doesn't stop him from citing and even quoting sources that aren't actually saying what he thinks they're saying. In this instance, the cargo cultist has found someone saying it's a mistake to assume the Friedmann equations continue to hold when the socalled cosmological constant Λ is not actually a constant. That's a technical error, which should have a straightforward technical fix. Today's mainstream cosmology (insofar as I myself understand it) attempts to fix that problem by assuming a piecewise approximation to the evolution of the universe, in which Λ remains constant within each era. That's a plausible way to deal with the problem of retrofitting an inflationary epoch (lasting about 10^{32} seconds) into the preGuth version of ΛCDM theory, but that approach can be and has been questioned. But no one who understands any of the above is questioning the success of ΛCDM or its use as a starting approximation for some more refined theory. In particular, the article Mike Helland is failing to understand goes on to say this:
Originally Posted by Ethan R. Siegal
It seems Mike Helland, as usual, doesn't know what he's talking about. He doesn't understand that the socalled "cosmic time" coordinate is compatible with relativity, and he doesn't understand that it is preferred because any other choice of time coordinate would obscure the homogeneity and isotropy of the model. As I wrote two days ago: 
25th June 2023, 12:28 PM  #264 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 12:32 PM  #265 
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25th June 2023, 12:46 PM  #266 
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I'll bite.
What are you referring to? If you have any question about the data I used, or equations I used, it's all documented in the github repo. eg, https://github.com/mikehelland/hubbl.../other/sse.htm ETA, you can use this bit right here to get a data object with the Pantheon+SH0ES data: Code:
fetch("https://mikehelland.github.io/hubbleslaw/data/Pantheon+SH0ES_z_mu.csv").then(res => res.text()).then(text => { //console.log(text) var lines = text.split("\n") for (var i = 1; i < lines.length; i++) { var line = lines[i].split(",") if (line[0]) { snData.push({"dm": parseFloat(line[2]), "z": parseFloat(line[0]), "derr": parseFloat(line[0])}) } } calculateDistances() drawData() calculateLCDMErrors() }) 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 01:23 PM  #267 
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I can’t see any part of that link that relates to the ‘Problem 8’ you’ve googled above, not W. D. Clingers addressing of the issues discussed there.
So for you to decide you’re going to accept one over the other, you must have solid logic  it’s not an issue of having to ‘take your word over theirs’ 
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25th June 2023, 01:44 PM  #268 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 01:44 PM  #269 
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you knew it would come to this
The author and sole proponent of Helland physics advertises his mathematical chops by denying, on the record, that FLRW models are compatible with general relativity.
ETA: It so happens that the archives of this forum record an unusually detailed mathematical proof that an entire family of FLRW models are compatible with general relativity:To simplify that proof, I assumed flat space, a zero cosmological constant, and positive mass/energy density. Those assumptions already imply space is either expanding or contracting. For generalizations of that proof to FLRW models with nonflat space, nonzero cosmological constant, and/or zero mass/energy density, consult standard textbooks (where the proofs are usually far less detailed). 
25th June 2023, 01:56 PM  #270 
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25th June 2023, 02:05 PM  #271 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 02:59 PM  #272 
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25th June 2023, 03:00 PM  #273 
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Steen  Jack of all trades  master of none! 

25th June 2023, 03:22 PM  #274 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 03:29 PM  #275 
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Helland is in no position to understand anything whatsoever to do with general relativity, and does not have the mathematical knowledge to understand the discussion which is taking place between respected cosmologists. It is the sign of a crackpot to find some idea by a respected physicist that he thinks supports his silly ideas, and to give that view 100% credibility while completely discounting the fact that dozens of other equally respected physicists have a different view. Helland is also notorious for ignoring proofs that his ideas are garbage, either through bias or because he doesn’t understand the proofs. It’s a simple fact that FLRW solutions are exact solutions to the Einstein equations under well understood conditions and are therefore entirely compatible with general relativity. As for accusing WDC of “fabrications”, that’s the height of projection, as it’s Helland who stumbles from one misunderstood and silly idea to the next.

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25th June 2023, 03:41 PM  #276 
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25th June 2023, 04:20 PM  #277 
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I suspect the author and sole proponent of Helland physics is referring to a series that begins with these four articles:
Originally Posted by Adam Frank
The following spoiler gives Mike Helland's cargocult silliness more attention than it really deserves, but it has some genuine historical interest. 
25th June 2023, 04:20 PM  #278 
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I'm not entirely sure what I'm talking about, but based on what little I know, the above seemed like a reasonable thing to say. Thank you in advance for any corrections. 

25th June 2023, 04:40 PM  #279 
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Don’t want to take my word for it? Try a standard textbook, for example Ciufolini and Wheeler Gravitation and inertia. Turn to section 4.2 on pages 193  220. First the metric is formally derived by applying the formalism of the Lie derivative of a tensor field with respect to a vector field. The derivation proceeds to define the homogeneity and isotropy of the manifold in terms of an isometry group of the Killing vector fields. Once the familiar metric is formally and rigorously derived, it can be formally shown that the origin can be translated freely anywhere and the metric has the same form with the new coordinates as it had with the original ones. The expression for the Gaussian curvature is derived and from that the Ricci curvature and the Einstein curvature tensor, to show formally that the curvature is constant over the manifold. Ciufolini and Wheeler then go on to formally derive the distance versus redshift relationship, and then the dynamics of the model  ie how it evolves over time. This is all perfectly compatible with, and indeed derived from the concepts of general relativity.

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25th June 2023, 04:46 PM  #280 
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