Hubble constant

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Catastrophe

"There never was a good war, or a bad peace."
Georges Lemaître - Wikipedia
https://en.wikipedia.org › wiki › Georges_Lemaître




Georges Henri Joseph Édouard Lemaître was a Belgian Catholic priest, theoretical physicist, mathematician, astronomer, and professor of physics at the ...
Religion: Christianity
Known for: Theory of the expansion of the univ...
Ordained: 22 September 1923; by Désiré-Jose...
Other academic advisors: Arthur Eddington ...‎
Career · ‎Work · ‎Bibliography · ‎References

Imgur: The magic of the Internet
 
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What's missing in the Wiki article is any mention of Slipher. Ug.

I've read that in 1925, Lemaitre came to Harvard and, at some point, he met Slipher (likely in Lemaitre's travels). [I would like to find some details on this trip to the US.] Regardless, he learned about Slipher's redshifts. [In 1917, Slipher published 21 redshifts (25 but 4 were blueshifts).]

[It was these redshifts that Hubble used in his velocity-distance paper (1929) that made Hubble famous. So the y-axis data were Slipher's, and the x-axis were his. Hubble got permission from Slipher to use the data, but never mentioned Slipher in that famous publication. :rolleyes: Hubble later gave credit to Slipher in 1931, but to little avail.]

Lemaitre's visit to Harvard, where he learned of the redshifts first hand, no doubt, had a profound effect on Lemaitre who, two years later, completed his PhD in physics from MIT (1927). His thesis was entitled,
The gravitational field in a fluid sphere of uniform invariant density according to the theory of relativity.
 
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Catastrophe

"There never was a good war, or a bad peace."
Helio, I wondered whether Eddington might mention Slipher, as he often mentions personalities in his many books. I have checked "Space Time and Gravitation", which is the only "Art" book I own, without success.

Obviously, you will have seen https://www.roe.ac.uk/~jap/slipher/

There is quite a lot in the referenced paper, starting:
"By 1917, V.M. Slipher had singlehandedly established a general tendency for ‘spiral nebulae’ to be redshifted (21 out of 25 cases). From a modern perspective, it could seem surprising that the discovery of the expansion of the universe was not announced at this point. Examination of the data and arguments contained in Slipher’s papers shows that he reached a more subtle conclusion: the identification of cosmological peculiar velocities, including the bulk motion of the Milky Way, leading to a beautiful argument in favour of spiral nebulae as distant stellar systems. Nevertheless, Slipher’s data actually contain evidence at >8σ for a positive mean velocity, even after subtracting the best-fitting dipole pattern owing to motion of the observer. In 1929, Hubble provided distance estimates for a sample of no greater depth, using redshifts due almost entirely to Slipher."


Cat :)

P.S. Sorry my edit crossed with your reply. :)
 
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Helio, I wondered whether Eddington might mention Slipher, as he often mentions personalities in his many books. I have checked "Space Time and Gravitation", which is the only "Art" book I own, without success.

Obviously, you will have seen https://www.roe.ac.uk/~jap/slipher/
That's an interesting account of some of Slipher's history. It notes that Slipher was able to detect rotation for the Sombrero galaxy (NGC4594) in 1914, long before others argued for rotation. [It was Vera Rubin, much later, that used redshifts on Andromeda to reveal dark matter, as Zwicky had coined it years earlier regarding his study of clusters.]

Also of interest from your link, Slipher recognized the likelihood that these high redshift nebulae are what many call "island universes". Perhaps this, and the recessional rates by other cosmologists, is what triggered the need for the "Great Debate" (1920).
 
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Also, thanks for Eddington's statement.

I suspect that Slipher felt he was only guessing the value of the distances he had, thus he would have not held an 8 sigma fit. [How did you insert the symbol for sigma? Is that the code insert?]

But it seems his distances were not that far off, after all, thus perhaps missing the opportunity to announce expansion. What stands out about Slipher is his humility, in contrast to Hubble. Lemaitre also seems to have been very humble.
 

Catastrophe

"There never was a good war, or a bad peace."
Ooooops - I can't even find the sigma!
I did nothing, so it must have been a c & p.

I do keep a Word doc with all the Greek and Russian alphabets, so I can just do a quick c & p. Only trouble is, it is probably buried so deep (not good English?) that I can rarely find it quickly.

кремль. стадион. театр. университет. больница. посольство. посол. терапист. атташе. актер. футболст. спортсмен. педиатр. президент.

I do keep an open Word doc at the bottom. It's useful for composing long messages, in fact, a whole Agreed Terms might be transferred directly from Word. There can be some problems, though.

Cat :)
 
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Ok, that doesn't surprise me.

Does this website show where we can go to get the codes? If we click on Insert in the header it shows a choice for </> for code. But I don't see how that works.
 
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Catastrophe

"There never was a good war, or a bad peace."
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Or you can just Google Greek Alphabet:

Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ/ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω.

Cat :) ΣΣΣΣΣ ;)


P.S. Is this what you want? I've never used them.

Alt Codes for Greek Letters
CharacterDisplayedAlt Code
AlphaαAlt 224
BetaβAlt 225
GammaΓAlt 226
DeltaδAlt 235
10 more rows

4 May 2019
Writing Greek Letters on the Computer - ThoughtCo
So how are you able to actually display those symbols?

Also, I know the code numbers, but how the heck do you implement the code? :)
 
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Press and hold down the Alt key with one hand, with the other hand type in the three digit code. The character will appear.
I use Alt - 2-4-8 to get the degree sign °.
 

Catastrophe

"There never was a good war, or a bad peace."
Helio, you just select (copy) and paste. Like I just copied Π from the list above. Simple as that. As I said, I just keep a Word file (containing the characters) at the bottom, so I can open it immediately and copy any desired character(s) to import here. I also use the Word doc to compose long messages, so I never lose any.

Cat :)
 

Catastrophe

"There never was a good war, or a bad peace."
billslugg, that does not work for me.

Also, o o o the middle o here, I used the superscript key, but, as you see, it does not work here. o o o. This is o o o Ctrl Shift + in Word, and the middle o is superscripted, but does not translate here. However, I can c&p your ° here. Thank you for that. I have copied it with my Greek letters, so I am able to use it in future.

Are you both using Apple? It seems we are on different systems.
"Format text as superscript or subscript in Word - Microsoft ...
https://support.microsoft.com › en-gb › office › format...


For superscript, press Ctrl, Shift, and the Plus sign (+) at the same time. For subscript, press Ctrl and the Equal sign (=) at the same time. (Do not press ..."

This latter works for me in Word, but not here.

Cat :) :) :)
 
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Press and hold down the Alt key with one hand, with the other hand type in the three digit code. The character will appear.
I use Alt - 2-4-8 to get the degree sign °.
Your Alt seems to be far better than my Alt. :) I get nothing, neither in the post box or trying it in the Code pull down.

The copy and paste Cat suggests will do fine, apparently....

Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ/ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω.
 
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Nov 19, 2021
328
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I am using windows. The shortcut for degree sign that works across all windows applications is
Alt + 0176

For Mac users the degree sign shortcut is Option + shift + 8

Just google "alt codes for mac" or "alt codes for windows"
 

Catastrophe

"There never was a good war, or a bad peace."
° ☺♥♦♣♠••◘○◙♂♀
billslugg, Thank you for that information.

There is another site: Symbol Codes | ALT Codes for Windows (psu.edu)

which, to enable easier access, gives an index, thus:
"Letters with Accents – (e.g.ó, ò, ñ)

Other Foreign Characters – (e.g. ç, ¿, ß)

Currency Symbols – (e.g. ¢, £, ¥)

Math Symbols – (e.g. ±, °, ÷)

Other Punctuation – (e.g. &, ©, §)

Using the Codes

Other Accents and Symbols: Character Map Other Page

Non-Numeric Accent Codes: Activate International Keyboard Other Page

Links to Other References"

Cat :)
 

Catastrophe

"There never was a good war, or a bad peace."
I, also, had to use a different keyboard as I could not get num lock, despite loving Kimmy or someone, as there is no num lock light on my HP laptop.

Cat :)
 

Catastrophe

"There never was a good war, or a bad peace."
My use would be for foreign characters, mathematical symbols including half and three quarter (other keyboard not attached), and the like.

As I said, I cannot get HP laptop num lock working.

Cat :)

P.S. OK - connected - ó, ò, ñ, ç, ¿, ß ¢, £, ¥ ± ° ÷ .&, ©, §
 
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For some reason, I am able to cut and paste the same extended ASCII character in 2 different visual forms here. For instance ASCII character 190 can be ¾ or ╛ . See https://www.meridianoutpost.com/resources/articles/ASCII-Extended-Code-reference-chart.php and just highlight and copy whatever character you need. Trying to get it out of a keyboard, as in holding the left <alt> key and typing 190 on the numeric pad, only gives me ╛.

So, if you need Greek letters, try googling Greek alphabet and copying the letters you need, thus:
Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ/ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω
from https://en.wikipedia.org/wiki/Greek_alphabet .
I expect you can do the same with math symbols, Japanese characters, emojis, etc.

There seems to be an expanding universe of characters we can search for and copy.

Now, getting back to the Hubble constant . . .


 

Catastrophe

"There never was a good war, or a bad peace."
Let's get back to the Hubble constant . . . . . .

View: https://imgur.com/a/1Oj1W1O


The Hubble "constant" is the slope of the graph. I maintain that the "constant" is not applicable all the way to the assumed zero (which demands that velocity of recession is zero when physical separation is zero). The graph actually shows negative recession values - these are found in galaxies approaching one another, which we see, for example in the Andromeda Galaxy.'''

View: https://imgur.com/a/cSliFNF


This does not affect the slope of the line representing the Hubble "constant" at higher values. The problem here is that there are at least two ways of measuring the data involved, and these give different "constants". Furthermore, there is tremendous scatter in the values shown, which suggests that the relationships are not sufficiently conforming to give a clean straight line.

"One possibility is that one or more of the methods to calculate the Hubble constant is flawed. However, the measurements of stars, galaxies, and the cosmic microwave background are incredibly detailed—which means the differences are most likely the result of something much more fundamental than imprecision."

What is the Hubble constant? | University of Chicago News (uchicago.edu)

That summarises my position on the Hubble "constant".


Cat :)
 
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The conceptual image I have of space is that it is expanding, and dragging matter along with it, somehow, even when it is expanding such that two points are receding from each other at more than the speed of light. In addition (or subtraction), pieces of matter are moving through space at no more (and usually much less) than the speed of light.

So, a graph of the differential velocity between us and everything else as a function of distance would have the superposition of both phenomena, with the expansion of space dominating at larger distances and the motions of galaxies through space dominating at close distances.

However, I see no reason that the rate of recession due to the expansion of space must be a constant with respect to distance from us. That thought just came from Hubble not seeing it as anything other than a straight line with the data he had at the time. Now, we not only have better data, which substantially changed the value of his "constant", but we also have some data that suggests that it is not a straight line for as far as we can see, now.

Maybe we will soon need to change the name to the "Hubble Parameter".:screamcat:
 
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Catastrophe

"There never was a good war, or a bad peace."
Unclear Engineer,
"we also have some data that suggests that it is not a straight line for as far as we can see, now."

I could say (tongue in cheek) that you could draw any shape you like in it.

Seriously, I am very interested. Do you have references?

Cat :)

P.S. I am well aware that you have different forces operating near the origin. This is due to gravitational attraction being dominant in this area. It explains the negative recessional velocities (=approaching). Vide "with the expansion of space dominating at larger distances and the motions of galaxies through space dominating at close distances." - the latter due to dominance of gravitational attraction.
 
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Cat, I was referring to the discrepancy between the rates of expansion calculated with the luminosity yard sticks and with the CBR, which seems to say that expansion is faster nearby, and slower at the farthest distance we can see.

I just read something about the Hubble Telescope recently providing an improved catalog of (distance, speed) points for redoing the closer to mid-distance rate calculations (but I can't find it right now).

Hopefully, Webb will give us even better data.

And, maybe Webb will repeat the discovery we got from Hubble that things look remarkably similar at greater distances than we predicted, so that stars and galaxies must have formed earlier (and thus faster?) than then-current predictions based on then-current theory. Or, maybe we will actually be able to see what we can now only predict, and verify something instead of needing "new science". It is exciting that we are literally close to seeing what we now think is the evolution of the visible universe. (Where is that crossed-fingers emoji?)
🤞🏻
[There it is, found and copied from https://yaytext.com/emoji/crossed-fingers/ .]
 
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