Comments about "Hubble's law" in Wikipedia

This document contains comments about the article Hubble's law in Wikipedia

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In the last paragraph I explain my own opinion.

Contents

• 1. Observed values
• 2 Discovery
• 2.1 FLRW equations
• 2.2 Lemaitre's Equation
• 2.3 Shape of the universe
• 2.4 Cepheid variable stars outside of the Milky Way
• 2.5 Combining redshifts with distance measurements
• 2.5.1 Hubble Diagram
• 2.6 Cosmological constant abandoned
• 3 Interpretation 3.1 Redshift velocity and recessional velocity
• 3.1.1 Redshift velocity
• 3.1.2 Recessional velocity
• 3.2 Observability of parameters
• 3.3 Expansion velocity vs relative velocity
• 3.4 Exponentiality
• 3.5 Idealized Hubble's Law
• 3.6 Ultimate fate and age of the universe
• 3.7 Olbers' paradox
• 3.8 Dimensionless Hubble parameter
• 4 Determining the Hubble constant 4.1 Earlier measurement and discussion approaches
• 4.2 Acceleration of the expansion
• 5 Derivation of the Hubble parameter
• 5.1 Matter-dominated universe (with a cosmological constant)
• 5.2 Matter- and dark energy-dominated universe
• 6 Units derived from the Hubble constant
• 6.1 Hubble time
• 6.2 Hubble length
• 6.3 Hubble volume
• 7. See also

Reflection

• Reflection 1 -
• Reflection 2 -
• Reflection 3 -

Introduction

The article starts with the following sentence.

1. Observed values

2 Discovery

2.1 FLRW equations

2.2 Lemaitre's Equation

2.3 Shape of the universe

2.4 Cepheid variable stars outside of the Milky Way

2.5 Combining redshifts with distance measurements

2.5.1 Hubble Diagram

2.6 Cosmological constant abandoned

3 Interpretation

3.1 Redshift velocity and recessional velocity

3.1.1 Redshift velocity

3.1.2 Recessional velocity

3.2 Observability of parameters

3.3 Expansion velocity vs relative velocity

3.4 Exponentiality

3.5 Idealized Hubble's Law

3.6 Ultimate fate and age of the universe

3.7 Olbers' paradox

3.8 Dimensionless Hubble parameter

4 Determining the Hubble constant

The value of the Hubble constant is estimated by measuring the redshift of distant galaxies and then determining the distances to the same galaxies (by some other method than Hubble's law).

To measure the redshift of a (distant) galaxy is rather straight forward. To measure the distance of the same galaxy is difficult. The problem is that the measured redshift represents the distance in the past.

4.1 Earlier measurement and discussion approaches

4.2 Acceleration of the expansion

5 Derivation of the Hubble parameter

5.1 Matter-dominated universe (with a cosmological constant)

5.2 Matter- and dark energy-dominated universe

6 Units derived from the Hubble constant

6.1 Hubble time

6.2 Hubble length

6.3 Hubble volume

7. See also

Following is a list with "Comments in Wikipedia" about related subjects

• Age of the universe Comments '
• Chronology of the universe Cosmological time - Comments
• Friedmann equations Comments

Observable Universe Comments

Reflection 1

Reflection 2

Reflection 3

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