Independent Researcher

Question

Asked 16 November 2021

# Are there redshift and luminosity distances for Cepheid Variable stars and RR Lyrae stars?

Do such measurements make sense? Do they exist?

Comparing redshift and luminosity distances, if that is a sensible question, may bear on the 4/3 scaling hypothesis as it relates to dark energy.

## Most recent answer

Cepheid distance is well established. My concern is the measurement of the red shift wavelength for the various Cepheids. Is there a data base with actual wavelength measurements?

## All Answers (4)

Dear Robert,

every measurement makes sense, only their interpretation(s) in the model(s) is up to debate.

The only problem that could occur in my mind is that Cepheids are too "near" us and the redshift measurement is not precise and/or under the resolution of actual made spectrograph, but if the star is far enough and you could make the two measurements (variability period and redshift) the comparison is useful to the famous "ladder problem" in astrophysics (and to make sure you calculate the distance right)

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Pantheory Research Org.

Our galactic stars do not relate to redshifts but luminosity distance does apply.

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University of Hamburg

Hi Robert Shour ,

Cepheid and RR Lyrae variables are well known standard candles, and important tools in the cosmological distance ladder. For example, Cepheid variables, which were discovered by Henrietta Swan Leavitt, have the property that their luminosity can be directly inferred by observing their pulsation period, which then allows one to calculate their luminosity distance, given that the observing instrument (telescope) also measures their flux.

However, although nothing stops you from making redshift measurements of relatively nearby objects, this will induce an error in any cosmological parameters inferred from these measurements (such as the luminosity distance), because the peculiar velocities of these objects would be comparable to their Hubble flow, giving you highly inconsistent results. Luminosity distances calculated by interpreting the measured redshifts as cosmological redshifts, become more reliable at large distances, where the Hubble flow dominates over the peculiar velocities.

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## Similar questions and discussions

What problems might be solvable using the Galileo 4/3 differential scaling explanation of dark energy?

- Robert Shour

What is the arithmetic used to calculate Omega_M?

- Robert Shour

This is a follow up question to: Are there any theories of dark energy that predict the value of omega_M? asked on RG on Oct 21, 2024.

Harri Shore kindly provided a comprehensive answer on RG the same day, explaining that Omega_M Is Typically Derived from Observations.

Scolnic, D. M. / Jones, D. O. / Rest, A. / Pan, Y. C. / others, in The Complete Light-curve Sample of Spectroscopically Confirmed SNe Ia from Pan-STARRS1 and Cosmological Constraints from the Combined Pantheon Sample 2018-06 ApJ , Vol. 859, No. 2 p. 101, estimated Omega_M. NASA (https://lambda.gsfc.nasa.gov/education/graphic_history/matterd.htm) describes Scolnic et al. study as “providing the tightest uncertainty obtained from this method in the plot”. The Pantheon 2018 estimate for Omega_M is 0.298 plus/minus 0.022.

The 4/3 theory predicts Omega_M as the denominator value in 4^3/3^3, which is 0.2967, very close to 0.298. For example, a recent discussion of 4/3 scaling based on Galileo is at:

Are there any articles laying out the math? If so, what are the cites for those articles?

Are there any theories of dark energy that predict the value of omega_M?

- Robert Shour

Astronomical measurements estimate the proportion of (supposed) radiation relative to matter as about 0.70/0.30.

4/3 scaling based on extending Galileo scaling to 4D predicts a ratio of energy densities for 4D space compared to 3D space as 4^3/3^3, which is about 0.7033 / 0.2967, very close to astronomical measurements.

As explained in:

Do any of the theories of dark energy (apart from extending Galileo scaling to 4D) explain or calculate the ratio of energy densities? What are the cites? What are estimates?

What is the source reference for Ole Sands 1965 remarks about knowledge doubling?

- Robert Shour

Wolfgang Dick on October 4, 2024 supplied the answer to the question, Do you know the citation for a 1965 article by Ole Sand that mentions knowledge doubling? (Many thanks.)

A scholar recounts their search for the source of the knowledge doubling idea in a 2021 video:

The Ole Sand article is found in:

Comprehensive Musicianship

Volume 2 of CMP (Series)

Volume 2 of CMP, Contemporary Music Project for Creativity in Music Education

Publisher Contemporary Music Project, Music Educators National Conference, 1965

At page 79 in the book with the article:

“Never before have the dynamic forces of change spun with such incredible speed. In the nearly two thousand years since the birth of Christ, there has been first a very slow and then a rapidly accelerating growth in the accumulation of knowledge. If this accumulation is plotted on a time line, beginning with the birth of Christ, the first doubling of knowledge occurs in 1750,the second in 1900, the third in 1950, and the fourth only ten years later, in 1960!”

What is the original source for these claims?

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