# Hubble constant

#### Greenlight

What if

H=v/d
where v = delta d/ delta t
where delta d = delta L
where delta L = L - L'
where L = L * sqr(1-(v/c)^2) // (Lorentz contraction )
and L' = L' * sqr(1-(v'/c)^2)
where v = velocity relative to the CMB ~600km/s
where v' = v + a*delta t
where a = acceleration rate relative to the CMB due to ~250km/s rotation around milky way

#### Catastrophe

##### "There never was a good war, or a bad peace."
I still believe that it is real science to include on the graph, those items where the velocity is negative, that is where objects are approaching one another, by gravitational attraction. This is an area near the origin where 'Hubbles law' is not applicable. By all means add a note to explain why the Hubble 'constant' is not working - surely this is the scientific way - not hiding them away.

View: https://imgur.com/a/zdbFJY6

Cat

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#### Greenlight

Lorentz contraction does not apply to objects in the same reference frame.

#### billslugg

The relative motion of a galaxy to us is a function of many things, including the Hubble constant. That a local galaxy is moving towards us does not mean the "Hubble constant is not working". It is there, it is just dwarfed by other motions.

Applied to the Earth - Sun relationship, the expansion of spacetime causes the Earth and Sun to move apart at about 10 meters per year. This is not measurable with current technology

Hubble constant 60 kilometers per megaparsec.
1 megaparsec is 3.26 million light years.
1 light year is 9.5e15 meters.
1 megaparsec is thus 3.1e22 meters.
Sun is 150 million kilometers from Earth.
Sun is 1.5e11 meters from Earth.
Earth is thus 4.8e-12 megaparsecs from the Sun.
Multiply 60 km/MPc times 1000 meters per kilometer times 4.8e-12 MPc
and we get 2.9e-7 meters per second.
Multiply times 31.6 million seconds per year and we get 9.1 meters per year.

#### Catastrophe

##### "There never was a good war, or a bad peace."
billlugg:
"The relative motion of a galaxy to us is a function of many things, including the Hubble constant. That a local galaxy is moving towards us does not mean the "Hubble constant is not working". It is there, it is just dwarfed by other motions."

How can you say that the Hubble constant is working in regions where distances are so close that gravitational effects take over? Please look at the graph where recession are negative. Clearly the Hubble constant is not appropriate here.

I am moderately happy (with some reservations) about the so-called 'Hubble constant' (are there still 2 flavours depending on method?) above areas on the graph close to the origin, but I think that the scientific method demands plotting of those points where gravitational attraction is dominant. I am quite OK with (what I believe is the correct procedure) the 'Hubble line' stopping at a certain point with the honest explanation that other factors become dominant. From that point to the origin, another line is appropriate. IMHO it is scientifically dishonest to pretend that the backward extension of the line on the graph goes through the origin. You can actually see on the graph (which I did not produce or add to or alter in any way) that that the plots shows 3/3 negative velocities shown. The graph changes course because known factors take over = gravitational effects. This does not affect the course of the line higher up.

Cat

P.S. I think that the very least one can do, is to have a dotted line through to some non-zero intersection - together with points at negative velocities - and to have a note that gravitational effects take over at close proximities. How does that sound to you?

P.P.S. Just take the graph, exactly as it is, and make the lower part of the line dotted. Dotted, that is, in the part of the line where there are now (in the graph) no points, and lower.

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#### billslugg

My first comment is that you should get rid of the original Hubble drawing and go with a more modern version. His estimates were off by a factor of ten due to his inability to accurately gauge distances due to the limits of science back then, Note the scale on the left puts the expansion rate at 1 Mpc to be 600 km/sec. The currently accepted value is 68 km/s/Mpc.

Since the expansion of space is measurable only over vast distances we must make an assumption that is also applies at closer distances. Given that all our data so far shows the universe to be homogeneous, this is a good assumption.

#### Catastrophe

##### "There never was a good war, or a bad peace."
Are you saying that there are not many graphs in science that have discontinuities or changes of direction due to changing conditions? Phase diagrams for starters.

Cat

#### billslugg

You are using a graph that is nearly 100 years old and off by a factor of ten. No conclusions should be drawn from it when we have much better data to look at.

I am saying there are many sources of relative motion and all need to be considered. Near to us, the expansion of spacetime is dwarfed by other more mundane considerations. We have no reason to believe it does not happen everywhere.

#### Catastrophe

##### "There never was a good war, or a bad peace."
I am simply concerned with putting the same data on the same graph and allowing for the fact that circumstances change at lower separations and are accounted for by making the line dotted.

What is the problem with that . . . . . . . . ?

Cat

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#### billslugg

Right, there are negative recessional velocities where galaxies are being drawn towards a gravitational mass between us and the galaxy. There are recessional velocities above the line due to galaxies being drawn to a more distant gravitational mass.

#### Catastrophe

##### "There never was a good war, or a bad peace."
And what does that do the the graph?

Cat

#### billslugg

It simply explains why there are points above and below Hubble's line.

#### Catastrophe

##### "There never was a good war, or a bad peace."
Just think what 0,0 means. Zero separation. Zero recessional velocity. . . . . . . . . . Is that what you really want to bend the graph line to the origin?

Cat

#### rod

"Hubble constant"

My note. This is always a fun constant in nature to watch the reporting values found.

Ref - Observations of type 1a supernovae are consistent with a static universe, https://arxiv.org/abs/0901.4172, 2009. "Analysis of type 1a supernovae observations out to a redshift of z=1.6 shows that there is good agreement between the light-curve widths and (1+z) which is usually interpreted as a strong support for time dilation due to an expanding universe...provides a Hubble constant of 63.1±2.5 kms^−1 Mpc^−1."

My note. This result is very interesting in view of the measurement obtained using the Moon. Ref - Worry No More, The Hubble Tension is Relieved: A Truly Direct Measurement of the Hubble Constant from Mooniversal Expansion, https://arxiv.org/abs/2203.16551, March 2022. "Using sedimentary and eclipse-based measurements of the lunar recession velocity, we derive a new local-Universe measurement of the Hubble constant (H0) from the recession rate of Earth's Moon. Taking into account the effects of tides, we find a value of H0 = 63.01 ± 1.79 km s^−1 Mpc^−1,.."

My note. So in 2009 using Type 1a SN with redshifts out to z=1.6, H0=63.1 km/s/Mpc. Using the March 2022 report for the Moon, H0 = 63.01 km/s/Mpc. Perhaps this is just a fluke

Ref - Cosmological Results from the RAISIN Survey: Using Type Ia Supernovae in the Near Infrared as a Novel Path to Measure the Dark Energy Equation of State, https://arxiv.org/abs/2201.07801, "The largest systematic errors are the redshift-dependent SN selection biases and the properties of the NIR mass step. We also use these data to measure H0=75.4±2.4 km s^−1 Mpc^−1 from stars with geometric distance calibration in the hosts of 8 SNe Ia observed in the NIR versus H0=65.9±3.4 km s^−1 Mpc^−1 using an inverse distance ladder approach tied to Planck."

My note. H0 = 75.4 km/s/Mpc now compared to Planck H0 = 65.9 km/s/Mpc using the CMBR. My thinking, using the CMBR is biased because the postulated redshift, z ~ 1100 is not spectroscopically determined.

Ref - Measurements of the Hubble Constant with a Two Rung Distance Ladder: Two Out of Three Ain't Bad, https://arxiv.org/abs/2204.10866, April 2022. "Modeling these assumptions yields central values ranging from H0 = 71.8 to 77.0 km/s/Mpc. Combining the four best fitting selection models yields H0 = 73.1 (+2.6/-2.3) km/s/Mpc as a fiducial result, at 2.6σ tension with Planck."

My note. Just in these small samples cited I find H0 values ranging 63 to 77 km/s/Mpc. Early reports in the 1920s-1930s showed H0 = 500 km/s/Mpc. Plugging in different values for H0 into the cosmology calculators will show some surprising age differences for the Universe

Ref - Study of the Virgo Cluster Using the B-Band Tully-Fisher Relation, https://ui.adsabs.harvard.edu/abs/1997ApJS..108..417Y/abstract, Feb-1997. "The distances to spiral galaxies of the Virgo cluster are estimated using the B-band Tully-Fisher (TF) relation, and the three-dimensional structure of the cluster is studied. The analysis is made for a complete spiral sample taken from the Virgo Cluster catalog of Binggeli, Sandage, & Tammann. The sample contains virtually all spiral galaxies down to MBT=-15 mag at 40 Mpc…Finally, we infer the Hubble constant to be 82 +/- 10 km s^-1 Mpc^-1."

My note. Now I see another value, H0 = 82 km/s/Mpc

#### Catastrophe

##### "There never was a good war, or a bad peace."
Straight lines, however derived, are very confidence building, but where do they intersect - why must it be the origin? Look at that inflation graph above (needs clicking on).

Real life isn't always perfect fitting straight lines through the origin.

Cat

#### billslugg

The reason the straight line does not go through the origin is the overwhelming forces due to local gravity confounding the tiny amount of recession due to the Hubble constant and the large amount of error in Hubble's measurements.
There was a proposal to measure the Hubble constant here in the Solar System with the next probe due to leave the solar system. A small retroreflector would be jettisoned and allowed to trail the main satellite by a few thousand miles or so. A beam of light would closely track the distance between them to see if it was increasing due to Hubble expansion.
Meanwhile, until the results of that experiment come in, you are free to dot the line near the origin.

Catastrophe

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billslugg

#### Helio

When the the first estimate was made for the Hubble constant(1927) , Lemaitre used Hubble’s early use of Cepheids for galactic distances. He combined these with Slipher’s redshifts. But, unknown at the time, Cepheids come in more than one flavor, and luck for use of the right one was not favorable for Hubble. It wasn’t long before Hubble/Humason resolved these.

There seems to be clear understanding what are local redshifts (ie Doppler) and what is cosmological redshift, though there is no small amount of scrutiny on this.

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#### Helio

Another ptroblem in these early estimates was that they demonstrated a universe younger than stars.

billslugg

#### Catastrophe

##### "There never was a good war, or a bad peace."

How a Dispute over a Single Number Became a Cosmological Crisis - Scientific American
March 1 2020.

"Gross cautioned that such distinctions are “arbitrary.” Then he said, “But yeah, I think you could call it a problem.” Twenty minutes later, at the close of the Q and A, he amended his assessment. In particle physics, he said, “we wouldn’t call it a tension or a problem but rather a crisis.”

Cat

#### Catastrophe

##### "There never was a good war, or a bad peace."
Currently, there are three main ways to measure the Hubble constant: by using astronomical measurements to look at objects nearby and see how fast they are moving; by using gravitational waves from collisions of black holes or neutron stars; or by measuring the light left over from the Big Bang, known as the cosmic ...

The Hubble constant, explained - University of Chicago News

Cat

Helio

#### Helio

Currently, there are three main ways to measure the Hubble constant: by using astronomical measurements to look at objects nearby and see how fast they are moving; by using gravitational waves from collisions of black holes or neutron stars; or by measuring the light left over from the Big Bang, known as the cosmic ...
The Hubble constant, explained - University of Chicago News
It’s still surprising to me how Slipher and Lemaitre rarely get credit.

Catastrophe