Thread: Halve the Hubble constant! (still apears to be 72km/s/Mpc)

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Halve the Hubble constant! (still apears to be 72km/s/Mpc)

Hello Physicists,

If anyone is interested in a radical solution to the dark energy problem, here is quite a simple one.

It's by a change to the usual scalefactor-redshift relation, which can remove the main arguments for an accelerating universe...radical, but true?

4 page paper + appendix attached

2. john hunter,

While you may make specific references to off-site material, our rules require that you make the substance of your presentation here, in this forum.

3. Yes, in words and/or equations. It would also be good if you identified specifically of what dark energy "problem" you speak.

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Originally Posted by john hunter
Hello Physicists, ...
Physicists know that the Hubble constant is measured to be 72km/s/Mpc from cosmological observations and 69km/s/Mpc from measurements of galaxies. It cannot be half that value.
Physicists know that dark energy is the observation of a derivation from Hubble's law and so changing Hubble's constant has no effect.

So far we have no "dark energy problem" stated and a solution that cannot be a solution.

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From this side it seems that so far we have two statements of what physicists 'know', both of which are incorrect.

Problem: Mainstream cosmologists have had to infer 'dark energy', but it has no explanation, it has had to be invoked simply to support the lambda CDM model. If they want to stick their heads in the sand and pretend there is no problem, that's up to them.

Solution: Dark energy doesn't exist and the acceleration of the universe doesn't exist.

To correct the two statements, or reword them. Physicists know that (assuming v=Hd) the Hubble constant is measured to be 72km/s/Mpc...(but v=2Hd, so H can be half the usual value)
...and for the second. Hubble's law is incorrect.

Detail is in the attached paper, but briefly the usual redshift-scalefactor relation from the 1930s is incorrect: instead of 1+z = a(0)/a(1)..., [where a(0) is the scalefactor of the universe now, a(1) is the scalefactor at the time of emission, z is redshift] ... 1+z = (a(0)/a(1))^2. If Hubbles constant is a(dot)/a, 1+z = (1+Hdt)^2 approx = 1+2Hdt

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Originally Posted by john hunter
From this side it seems that so far we have two statements of what physicists 'know', both of which are incorrect.
We have empirical data that makes your ATM idea wrong, i.e. the value of Hubble's constant.
We have the physical fact that dark energy does not depend ono the value of Hubble's constant.

The first thing that a proposer of an Against the Mainstream idea needs to is to learn about the mainstream. That prevents them from making mistakes and from stating ignorance about the mainstream.
1. Dark energy is the observation that the expansion of the universe is accelerating.
2. Stating that "it has no explanation" is wrong - there are explanations.
3. This is the Lambda-CDM model which includes dark energy because it is an observation about the universe. No one arbitrarily made up dark energy, created the Lambda-CDM model and then went looking for dark energy !
4. Mainstream cosmologists do not stick their heads in the sand" about a problem that does not exist.
5. There is no "assuming v=Hd". Starting from 1927 and famously with Hubble's 1929 paper there have been measurements of galaxy velocities and distances that give a linear relationship between v and d. We call the constant relating v and d Hubble's constant.
6. Physicists know that the Hubble constant is not measured to be 72 km/s/Mpc !
They know that Hubble's constant is measured to have 2 different values of 72 km/s/Mpc from cosmological data and 69 km/s/Mpc from looking at galaxies. However most astronomers think that it is the 72 value that will be confirmed. The distances to galaxies depends on the cosmic distance ladder which is a series of overlapping methods for distance measurements. An early rung is parallax used to measure distances to stars, e.g. leading to the standard candle of Cepheid variable stars used by Hubble. Parallax depends on measuring very small angles accurately.

We do not need to read your PDF to know that it is wrong. Merely asserting that Hubble's constant is half what is measured makes it wrong. Think about an unsupported assertion that every person on Earth is half their weight. That is obviously wrong because we have measurements of weight! Or a more relevant example: If someone were to assert without any evidence that the mass of an electron was half what was measured then they would be wrong since we have measured the mass of electrons.

Asserting that halving Hubble's constant removes the need for dark energy is wrong. Hubble's constant comes from the observation of Hubble's law (v=H0D where the capital D is important). It is deviations from Hubble's law that leads to an accelerating expansion and the need for a mechanism to explain it (dark energy). This is independently confirmed by CMB data.
Last edited by Reality Check; 2017-Jul-10 at 10:09 PM.

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Reality Check,

On 1. and 3. the 'observation that the universe is accelerating' is only an observation that the expansion deviates from the traditional Hubble law. However it is a possibility that the traditional Hubble law is not valid.

On 5. By Hubbles constant in the post, it was meant the expansion rate of the universe H=a(dot)/a This is what most physicists mean by Hubbles constant...Hubbles law from Wikipedia and others (quote)
"the law was first derived from the general relativity equations by Georges Lemaître in a 1927 article where he proposed the expansion of the universe and suggested an estimated value of the rate of expansion, now called the Hubble constant."

The v=Hd equation is equivalent to v=Hcdt, where dt is the time of travel of the photon i.e.v/c =Hdt, so z=Hdt and 1+z = 1+Hdt is being assumed. That is the false assumption that is causing the omega(matter) of 0.25 result from CMB data and apparent deviations from Hubbles law (supernovae data). If the correct 1+z = (1+Hdt)^2 is used both these arguments that have been used to support the accelerating universe model disappear.

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Originally Posted by john hunter
Once again you need to learn the mainstream science that you cite.
Georges Lemaître in a 1927 article derived that an expanding universe would fit a linear relationship and confirmed that with galaxy velocities and distances. He gave an estimate of what we now know as Hubble's constant.
Edwin Hubble in a 1929 paper measured a linear relationship between galaxy velocities and distances. That empirical relationship is Hubble's law as stated in the article you cited
Hubble's law is the name for the observation in physical cosmology that:
1.Objects observed in deep space (extragalactic space, 10 megaparsecs (Mpc) or more) are found to have a Doppler shift interpretable as relative velocity away from Earth;
2.This Doppler-shift-measured velocity, of various galaxies receding from the Earth, is approximately proportional to their distance from the Earth for galaxies up to a few hundred megaparsecs away.[1][2]

Hubble's law is considered the first observational basis for the expansion of the universe and today serves as one of the pieces of evidence most often cited in support of the Big Bang model.[3][4] The motion of astronomical objects due solely to this expansion is known as the Hubble flow.[5]
There is no "traditional Hubble law". Measurements of galaxy velocities and distances did not stop in 1929. They continue today. That is 90 years of confirming Hubble's law (aside from the tiny correction of dark energy).
There is no "v=Hd equation". Hubble's law is v = H0D
where
v is the recessional velocity, typically expressed in km/s.
H0 is Hubble's constant and corresponds to the value of H (often termed the Hubble parameter which is a value that is time dependent and which can be expressed in terms of the scale factor) in the Friedmann equations taken at the time of observation denoted by the subscript 0. This value is the same throughout the Universe for a given comoving time.
D is the proper distance (which can change over time, unlike the comoving distance, which is constant) from the galaxy to the observer, measured in mega parsecs (Mpc), in the 3-space defined by given cosmological time. (Recession velocity is just v = dD/dt).
As I noted before the capital D is important - it is the proper distance to a galaxy. It is not "cdt". Thus the " false assumption" is yours, not cosmologists.

Read about the cosmic distance ladder. Many of the methods are ways of working out how bright an object would be if we were next to it (intrinsic magnitude). The measured brightness then tells us how far away the object is.

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IF01: Please state the actual method of using Type 1a supernova to measure distances to galaxies.
A hint - it has nothing to do with a "flux F due to distant supernovae".
Last edited by Reality Check; 2017-Jul-11 at 12:47 AM.

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No Way

Originally Posted by john hunter
Hello Physicists,

If anyone is interested in a radical solution to the dark energy problem, here is quite a simple one.

It's by a change to the usual scalefactor-redshift relation, which can remove the main arguments for an accelerating universe...radical, but true?

4 page paper + appendix attached
john hunter, with all due respect, there is no way I am going to download that myterious link to my laptop. Could you please present your idea here, as requeted and as required by the rules of ATM, with supporting references and observations.

While you do that, contemplate the signature lines below, particularly the quote from korjik.

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John Mendenhall,

The idea is as follows: Mainstream cosmology has interpreted observations to conclude that the expansion of the universe is accelerating. They are using a relation between redshift and scale-factor of the universe of 1+z = a(0)/a(1).....[a(0)=scale-factor of the universe now, a(1)=scale-factor at the time of emission of the photon]

In the OP Hubbles constant meant the rate of expansion of the universe defined by a(dot)/a

The idea is that the redshift-scalefactor relation is wrong and should be 1+z = [a(0)/a(1)]^2

Since a(0)/a(1) = 1+Hdt, where dt is a change in time, 1+z = (1+Hdt)^2 =1+2Hdt, for observations of closer galaxies etc the (Hdt)^2 term is negligible,
so we still get a linear relation if cosmologists interpret redshift as a velocity v/c=2Hdt, v=2Hd.

So the work on measuring the constant of proportionality from 1930 until present day is not being challenged, just that when it's measured and found to be approx. 72km/s/Mpc, this value is not the expansion rate of the universe...that value is half, i.e. about 36km/s/Mpc

With the new relation there is no need to infer acceleration or 'dark energy', a constant H model works very well. i.e. it matches all observations that have concluded that the matter density parameter is about 1/4 (0.25) e,g, WMAP5 0.258. Planck 0.308
They really measure omega(m)h^2, where omega(m) is the matter density parameter, h =H/100, then deduce omega(m), using a value for Hubbles constant, as defined above which is two times too big. They then also deduce the dark energy parameter to be about 0.75. If a value for h of half is used omega(m) is approx. 1.0 and the dark energy parameter is 0

The same model gives a good match to the supernovae data (Riess etc), again with a constant H, (in 1998, that data provided 'evidence' for an accelerating universe), it's in the attached paper mentioned in post 1. There is a graph on page 4 which shows a really good match again for constant H (no acceleration), with the new redshift-scalefactor relation.

There is no virus! Reality Check has presumably downloaded it and would be warning you all by now, so it's recommended.

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Reality Check,

IOF1: "Type Ia supernovae that have a very well-determined maximum absolute magnitude as a function of the shape of their light curve and are useful in determining extragalactic distances up to a few hundred Mpc" but how can that distinguish between v=Hd with H approx. 72km/s/Mpc and v=2Hd with H approx. 36km/s/Mpc

IOF2: DF Lawden, but same equations are online, it's for a space of constant curvature with H constant

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Originally Posted by john hunter
Reality Check,
Your answer to IF01 seems to be that your PDF ignored how Type 1a supernova are used to determine distances, i.e. you have a completely irrelevant section about distance moduli.
The answer to IF02 would be the literature from which you got the equation(s) which I would then be able to read. FYI that could be a link to the Wikipedia article on the Friedmann equations where H = a(dot)/a. N.B. The H in the Friedmann equations is not the Hubble constant H0. H is the Hubble parameter which is dimensionless. In the same article there is the useful density parameter (also containing the Hubble parameter) used to compare cosmological models.

Maybe try again:
IF01: Please state the actual method of using Type 1a supernova to measure distances to galaxies.
Last edited by Reality Check; 2017-Jul-11 at 09:06 PM.

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Originally Posted by john hunter
In the OP Hubbles constant meant the rate of expansion of the universe defined by a(dot)/a
This is where you seem to go wrong. It is the Hubble parameter that is defined as a(dot)/a. Friedmann equations
H = a(dot)/a is the Hubble parameter.
This is a dimensionless parameter because the scale factor, a(t), is dimensionless. H can vary because a(t) can vary as can its time derivative. If you are confusing H with H0 then your ATM idea is obviously incorrect.

This is Riess A. G et al. Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant. The evidence for a nonzero cosmological density comes from figures 4 and 5
Figure 4: MLCS SNe Ia Hubble diagram. The upper panel shows the Hubble diagram for the low-redshift and high-redshift SNe Ia samples with distances measured from the MLCS method (Riess, Press, & Kirshner 1995, 1996a; Appendix of this paper). Overplotted are three cosmologies: “low” and “high” ΩM with ΩΛ = 0 and the best ﬁt for a ﬂat cosmology, ΩM = 0.24, ΩΛ = 0.76. The bottom panel shows the diﬀerence between data and models with ΩM = 0.20, ΩΛ = 0. The open symbol is SN 1997ck (z = 0.97) which lacks spectroscopic classiﬁcation and a color measurement. The average diﬀerence between the data and the ΩM = 0.20, ΩΛ = 0 prediction is 0.25 mag.
Figure 5: ∆m15(B) SN Ia Hubble diagram. The upper panel shows the Hubble diagram for the low-redshift and high-redshift SNe Ia samples with distances measured from the template ﬁtting method parameterized by ∆m15(B) (Hamuy et al. 1995, 1996d). Overplotted are three cosmologies: “low” and “high” ΩM with ΩΛ = 0 and the best ﬁt for a ﬂat cosmology, ΩM = 0.20, ΩΛ = 0.80. The bottom panel shows the diﬀerence between data and models from the ΩM = 0.20, ΩΛ = 0 prediction. The open symbol is SN 1997ck (z = 0.97) which lacks spectroscopic classiﬁcation and a color measurement. The average diﬀerence between the data and the ΩM = 0.20, ΩΛ = 0 prediction is 0.28 mag.
MLCS and ∆m15(B) are techniques to calculate the distances to galaxies from Type 1a supernova light curves.
Last edited by Reality Check; 2017-Jul-11 at 09:25 PM.

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That fact has been demonstrated by the persistent inability of astronomers to agree on a value for the Hubble constant, which is a measure of the size, age, and rate of expansion of the universe. To derive the Hubble constant, one must measure the breadth of the red shift of galaxies and their distance from the Earth. The former measurement is straightforward, but the latter is horrendously complicated. Astronomers cannot assume that the apparent brightness of a galaxy is proportional to its distance; the galaxy might be nearby, or it might simply be intrinsically bright. The debate over the Hubble constant offers an obvious lesson: even when performing a seemingly straightforward calculation, cosmologists must make various assumptions that can influence their results, they must interpret their data, just as evolutionary biologists and historians do. One should thus take with a large grain of salt any claims based on high precision. (John Horgan)

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Originally Posted by wd40
...(John Horgan)
An irrelevant, uncited quote from some guy called John Horgan (probably the science journalist John Horgan and a quote from his outdated 1996 book). The real world debate today is why 2 sources for measuring the Hubble constant give 2 different but close results.
Last edited by Reality Check; 2017-Jul-11 at 09:46 PM.

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From wd40s comments, and the Wikipedia article on Hubbles law https://en.wikipedia.org/wiki/Hubble%27s_law (where is first has Hubble constant in bold) it's clear that many use the term Hubbles constant for the rate of expansion of the universe. However it is clear that the term Hubble constant in the OP meant a(dot)/a..if you want to use the term Hubble parameter that's OK....it does have dimensions though, of seconds^(-1)

http://supernova.lbl.gov/union/ diagram called 'Binned Hubble diagram' shows how cosmologists use a plot of distance moduli against redshift to test different cosmological models....so the section in the pdf showing how the different redshift-scalefactor relation can match that data with constant H is very relevant.

IFO2 Introduction to Tensor Calculus, Relativity and Cosmology, Dover publications D.F. Lawden (this was answered previously)

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Reality Check P.S. in your post number 8 ..."H0 is Hubble's constant and corresponds to the value of H (often termed the Hubble parameter which is a value that is time dependent and which can be expressed in terms of the scale factor) in the Friedmann equations taken at the time of observation denoted by the subscript 0."

So what is wrong with saying "Halve the Hubble constant!"? i.e. the value of a(dot)/a at time of observation (now) is half what is accepted by the mainstream.

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Originally Posted by john hunter
Which are not his comments. They look like a quote by a journalist from a 1996 book - two years before dark energy was discovered!
The Hubble constant is not a(dot)/a but you can easily show that I am wrong:
IF03: Cite the scientific literature that states that the Hubble constant H0 is defined as a(dot)/a.
This is not simply that we can interchange the words "Hubble constant" and "Hubble parameter". These are two different things with different definitions. The Hubble constant is an empirical measurement. The Hubble parameter is a theoretical parameter.

And support the your next assertion:
IF04: Cite the scientific literature that states that the Hubble parameter H has dimensions of seconds^(-1).

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Originally Posted by john hunter
http://supernova.lbl.gov/union/ diagram called 'Binned Hubble diagram' shows how cosmologists use a plot of distance moduli against redshift to test different cosmological models..
IF05: Show how the diagram you cite is a test of different cosmological models, e.g. list them.
The Introduction to the SCP Union2.1 Compilation page states "All analyses and cuts were developed in a blind manner, i.e. with the cosmology hidden".
The Binned Hubble Diagram with color-coded samples (PDF) graph has one and only one fitted line.

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Originally Posted by john hunter
So what is wrong with saying "Halve the Hubble constant!"?
Simply because the Hubble constant is a measured value so you need to answer:
IF06: List the measurements of the Hubble constant being 36 km/s/Mpc.
Alternately show how all of the calculations of the Hubble constant from galaxies and the CMB are wrong by a factor of 2.

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Originally Posted by john hunter
Reality Check P.S. in your post number 8 ..."H0 is Hubble's constant and corresponds to the value of H (often termed the Hubble parameter which is a value that is time dependent and which can be expressed in terms of the scale factor) in the Friedmann equations taken at the time of observation denoted by the subscript 0."
Look further down the page at the "Dimensionless Hubble parameter" section. Hubble's law is v = H0D
Dimensionless Hubble parameter
Instead of working with Hubble's constant, a common practice is to introduce the dimensionless Hubble parameter, usually denoted by h, and to write the Hubble's parameter H0 as h × 100 km s−1 Mpc−1, all the uncertainty relative of the value of H0 being then relegated to h.[55]
H and H0 are very different. H has no dimensions. H0 has dimensions. H varies with time. H0 is a constant. H is valid in any homogeneous and isotropic model of the universe. H0 only applies to this universe where it is an empirical measurement of 72k m/s/Mpc from cosmological observations and 69 km/s/Mpc from measurements of galaxies.

23. Not in any way my area of knowledge, but as an interested observer of this discussion: would not halving Ho also have the effect of making the universe far older than the oldest observed stars?

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Reality Check,

Putting Hubble constant definition as key words brings up many sites e.g. https://www.merriam-webster.com/dict...ble%20constant which refer to ‘the rate of expansion of the universe’
I.e. the present day value of a(dot)/a. In any case it has been repeated clearly that the original post meant that the present day value for a(dot)/a …(the expansion rate of the universe) should be half of what is currently ‘measured’ and accepted by mainstream cosmologists.

‘Hubbles Law’ from Wikipedia quote “The law is often expressed by the equation v = H0D, with H0 the constant of proportionality (Hubble constant) between the "proper distance" D to a galaxy (which can change over time, unlike the comoving distance) and its velocity v (i.e. the derivative of proper distance with respect to cosmological time”
So if Hubbles law is to relate “proper distance” to “v, the derivative of proper distance” it should be v=2H(0)d instead of v=H(0)d….hence
IF06 All measurements which have concluded a value of approx 69 or 72km/s/Mpc are out by a factor two due to an incorrect version of Hubbles law being used.

AGN, Yes that's a possibility, but there was a debate previously that some stars were older than the age of the universe with H(0) as 72km/s/Mpc...the 'age controversy'...it could well be that the niave 'single bang' (Big Bang) model needs some adjustment and that even though the time between 'Big Bangs' might be doubled, there would be smaller 'bangs' too, and recycling of matter strangely enough via AGNs!. This could account for the foam like structure and the oldest observed stars not being older than mainstream age of universe, but all this is a bit off the main topic which maybe should be returned to...

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For IF05:

https://arxiv.org/abs/astro-ph/9812133 (Perlmutter 1998) top of page 23 shows how different models with varying matter density parameters and dark energy densities fit the supernovae data. This and Riess were taken as evidence in favour of a non zero lambda, i.e. dark energy

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Originally Posted by john hunter
Putting Hubble constant definition as key words brings up many sites e.g. https://www.merriam-webster.com/dict...ble%20constant which refer to ‘the rate of expansion of the universe’
This is not surprising because the Hubble constant is related to the rate of expansion of the universe ! But its units show that it is not the actual rate of expansion of the universe which would be a special change per time. I cited the Hubble's law article to you before and quoted what have just quoted!. This is Hubble's law
Hubble's law is the name for the observation in physical cosmology that:
1.Objects observed in deep space (extragalactic space, 10 megaparsecs (Mpc) or more) are found to have a Doppler shift interpretable as relative velocity away from Earth;
2.This Doppler-shift-measured velocity, of various galaxies receding from the Earth, is approximately proportional to their distance from the Earth for galaxies up to a few hundred megaparsecs away.[1][2]
Hubble's law is an empirical relationship. Hubble's constant is a measurement. What you quote and I will quote again is simply the statement of the empirical law: Hubble's law is v = H0D
where
v is the recessional velocity, typically expressed in km/s.
H0 is Hubble's constant and corresponds to the value of H (often termed the Hubble parameter which is a value that is time dependent and which can be expressed in terms of the scale factor) in the Friedmann equations taken at the time of observation denoted by the subscript 0. This value is the same throughout the Universe for a given comoving time.
D is the proper distance (which can change over time, unlike the comoving distance, which is constant) from the galaxy to the observer, measured in mega parsecs (Mpc), in the 3-space defined by given cosmological time. (Recession velocity is just v = dD/dt).
This is simple science. There is one variable x. There is another variable y. We measure x. We measure y. We plot x versus y and see that the points can be fitted with a straight line. Thus x = ay + b (the equation for a straight line of slope a and intercept b). Hubble measured redshift and thus v. Hubble measured distance and thus D. Hubble plotted v versus D. Hubble saw that the points can be fitted with a straight line intercepting the origin (b = 0) Thus v = aD. We label that measured constant, H0.

Defintely try again:
IF01: Please state the actual method of using Type 1a supernova to measure distances to galaxies.

Not citing literature is not an answer to IF03. Not citing measurements is not a answer to IF06. Ignoring the diagram you cited is not an answer to IF05.
IF03: Cite the scientific literature that states that the Hubble constant H0 is defined as a(dot)/a.
IF04: Cite the scientific literature that states that the Hubble parameter H has dimensions of seconds^(-1).
IF05: Show how the diagram you cite is a test of different cosmological models, e.g. list them.
IF06: List the measurements of the Hubble constant being 36 km/s/Mpc.

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Originally Posted by john hunter
For IF05:
Which is IF05: Show how the diagram you cite is a test of different cosmological models, e.g. list them., not a question about a paper.
To empathize the difference:
IF07: What does the graph on top of page 23 in the Perlmutter et.al. (1998) paper plot?
You will need to read the text of Measurements of Omega and Lambda from 42 High-Redshift Supernovae especially the figure captions. Start with figure 1
FIG. 1.— Hubble diagram for 42 high-redshift Type Ia supernovae from the Supernova Cosmology Project, and 18 low-redshift Type Ia supernovae from the Calán/Tololo Supernova Survey, after correcting both sets for the SN Ia lightcurve width-luminosity relation
The figure you cite is the same data (note the same references) with a small change:
(a) Hubble diagram for 42 high-redshift Type Ia supernovae from the Supernova Cosmology Project, and 18 low-redshift Type Ia supernovae from the Calán/Tololo Supernova Survey, plotted on a linear redshift scale to display details at high redshift"

In Reiss et. al., MLCS and ∆m15(B) are different techniques to change the supernova light curve into a representation of distance so that a Hubble diagram (distance versus redshift) can be plotted. Guess what effective mB is in Perlmutter et.al. ?

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IF01 To find the distance to the galaxy that contains the supernova, scientists just have to compare how bright they know the explosion should be with how bright the explosion appears. Using the inverse square law, they can compute the distance to the supernova and thus to the supernova's home galaxy.

IF02 Introduction to Tensor Calculus, Relativity and Cosmology, Dover publications D.F. Lawden (this was answered previously)

IF03 It has been made clear that the original post meant that the rate of expansion of the universe is half that accepted by the mainstream.

IF04 You are right the Hubble parameter is dimensionless

IF05
https://arxiv.org/abs/astro-ph/9812133 (Perlmutter 1998) top of page 23 shows how different models with varying matter density parameters and dark energy densities fit the supernovae data. This and Riess were taken as evidence in favour of a non zero lambda, i.e. dark energy there are 4 models (omega(m), omega(lambda)) = (0,1) (0.5,0.5) (1,0) (1.5,-0.5) The lamda cdm model thus has a variable parameter which can be used to get a good fit to the data, matter density of about 0.28 is a good fit so omega(lambda) of 0.72 is deduced.

However changing the redshift-scalefactor relation from 1+z=a(0)/a(1) to 1+z=(a(0)/a(1))^2 gives a good match with no variable parameter simply omega(matter)=1 and omega(lambda)=0. This new relation (which is the main point of the OP) leads to a rate of expansion a(dot)/a of half the mainstream accepted value...i.e approx. 36km/s/Mpc . This occurs as the apparent velocity of recession would be related to distance by v=2H(0)d, instead of v=H(0)d

IF06 With the new redshift-scalefactor relation, any local measurement of the Hubble constant which gave a result of approx. 72km/s/Mpc would be reinterpreted as an a(dot)/a value of half i.e. approx. 36km/s/Mpc

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Originally Posted by john hunter
IF01 ...
IF01: Wrong, it is not the brightness of the supernova explosion.
IF02:Cite accessible literature, not a book I will have to buy. For example what I posted and cited on 12 July 2017:
Originally Posted by Reality Check
The answer to IF02 would be the literature from which you got the equation(s) which I would then be able to read. FYI that could be a link to the Wikipedia article on the Friedmann equations where H = a(dot)/a. N.B. The H in the Friedmann equations is not the Hubble constant H0. H is the Hubble parameter which is dimensionless.
IF03: No citation to the scientific literature again !

Originally Posted by john hunter
IF04 You are right the Hubble parameter is dimensionless.
Which means that the Hubble constant (has dimensions) is not the Hubble parameter and thus not a(dot)/a!

IF05: Ignoring the question is not an answer.
IF06: Denying what the Hubble constant is (a measurement) is not an answer.

One question answered out of 6!
IF01: Please state the actual method of using Type 1a supernova to measure distances to galaxies.
IF03: Cite the scientific literature that states that the Hubble constant H0 is defined as a(dot)/a.
IF05: Show how the diagram you cite is a test of different cosmological models, e.g. list them.
IF06: List the measurements of the Hubble constant being 36 km/s/Mpc.

The new question is
IF07: What does the graph on top of page 23 in the Perlmutter et.al. (1998) paper plot?
Last edited by Reality Check; 2017-Jul-13 at 08:57 PM.

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Originally Posted by john hunter
https://arxiv.org/abs/astro-ph/9812133 (Perlmutter 1998) top of page 23 shows how different models with varying matter density parameters and dark energy densities fit the supernovae data. This and Riess were taken as evidence in favour of a non zero lambda, i.e. dark energy there are 4 models (omega(m), omega(lambda)) = (0,1) (0.5,0.5) (1,0) (1.5,-0.5) The lamda cdm model thus has a variable parameter which can be used to get a good fit to the data, matter density of about 0.28 is a good fit so omega(lambda) of 0.72 is deduced.
I read the papers about a decade ago and again as a result of this thread . I know what they contain. You seem not to know what their contents mean.
Hubble's law is an empirical law. Before the papers (1998), we had data out to a relatively low redshift (z < 1) and Hubble's law held. But GR states that a linear relationship between distance and velocity exists only at low z, thus Hubble's law and the data supporting it. That is the "However, the relation between recessional velocity and redshift depends on the cosmological model adopted, and is not established except for small redshifts." statement in the Hubble's law article. Next to that statement is a Possible velocity vs. redshift functions; patterned after Davis & Lineweaver image. See that these functions are all linear for low z but are non-linear for higher z.

Thus Riess 1998 and Perlmutter 1998 ignore Hubble's law because they know it is invalid at high z where their new data resides. The figures you are talking about are Hubble diagrams with supernova data fitted to cosmological models that include that they are non-linear.

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