Comments about "Gravitational redshift" in Wikipedia

This document contains comments about the article Gravitational redshift in Wikipedia

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In the last paragraph I explain my own opinion.

Contents

• 1. Prediction by the equivalence principle and general relativity
• 1.1 Uniform gravitational field or acceleration
• 1.2 Spherically symmetric gravitational field
• 1.2.1 Newtonian limit
• 1.2.2 Prediction of the Newtonian limit using the properties of photons
• 2. Experimental verification
• 2.1 Astronomical observations
• 2.2 Terrestrial tests
• 3. Early historical development of the theory
• 4. See also

Reflection

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

Introduction

The article starts with the following sentence.

1. Prediction by the equivalence principle and general relativity

1.1 Uniform gravitational field or acceleration

1.2 Spherically symmetric gravitational field

1.2.1 Newtonian limit

1.2.2 Prediction of the Newtonian limit using the properties of photons

2 Experimental verification

2.1 Astronomical observations

2.2 Terrestrial tests

3. Early historical development of the theory

The gravitational weakening of light from high-gravity stars was predicted by John Michell in 1783 and Pierre-Simon Laplace in 1796, using Isaac Newton's concept of light corpuscles (see: emission theory) and who predicted that some stars would have a gravity so strong that light would not be able to escape.

That means that the force of gravity can influence light i.e. electromagnetic waves.

Once it became accepted that light was an electromagnetic wave, it was clear that the frequency of light should not change from place to place, since waves from a source with a fixed frequency keep the same frequency everywhere.

How is the physical effect that waves keep the same physical frequency everywhere, demonstrated?
This is different from the effect that the speed of light of a flash emanating from a source 'at rest' and a moving source are the same.

One way around this conclusion would be if time itself were altered – if clocks at different points had different rates

The most logical conclusion, if clocks at different points had different rates, is that the clock-time shown on these clocks is different, but that does not mean that the universal or cosmological time is affected.

Since the light would be slowed down by gravitational time dilation (as seen by outside observer), the regions with lower gravitational potential would act like a medium with higher refractive index causing light to deflect.

This is a 'strange' sentence from a physical point of view. How can the speed of light be slowed down by gravitational time dilation i.e. the effect that 'time' is influenced by (the force of) gravitation. My conclusion is that the 'relation' between cause and effect is missing.

5. See also

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

• Relativity of Simultaneity Comments
• One-way speed of light Comments

Reflection 1

Reflection 2

Reflection 3

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