## Comments about "Kennelly-Heaviside_layer" in Wikipedia

This document contains comments about the article Kennelly-Heaviside_layer in Wikipedia
• The text in italics is copied from that url
• Immediate followed by some comments
In the last paragraph I explain my own opinion.

### Introduction

The article starts with the following sentence.
The Heaviside layer, sometimes called the Kennelly–Heaviside layer, named after Arthur E. Kennelly and Oliver Heaviside, is a layer of ionised gas occurring roughly between 90km and 150 km (56 and 93 mi) above the ground — one of several layers in the Earth's ionosphere. It is also known as the E region.
Okay
It reflects medium-frequency radio waves.
OKay.

### 1. History

Physicists resisted the idea of the reflecting layer for one very good reason; it would require total internal reflection, which in turn would require that the speed of light in the ionosphere would be greater than in the atmosphere below it.
Why?
Exactly based on which observations is this based?
Since the latter speed is essentially the same as the speed of light in a vacuum ("c"), scientists were unwilling to believe the speed in the ionosphere could be higher.
The most important is: What are the facts.
If the speed in the ionosfeer is actual higher than that is what it is.
Nevertheless, Marconi had received signals in Newfoundland that were broadcast in England, so clearly there must be some mechanism allowing the transmission to reach that far.
That is a fact But that says nothing about speeds involved.
The paradox was resolved by the discovery that there were two velocities of light, the phase velocity and the group velocity.
How were both discovered? One of the most important issues is: What does actual physical move; the phase or the group.
The issue is when you transmit a light pulse: when do you physical receive the photons. To say more specific when do you receive information.
A similar problem exists to study a tsunami. When you receive the wave on a shore a 1000 km away from the source, what you receive is not water from the source, but a part of the energy released from the source. It is this speed which propagates through water that is important.
The phase velocity can in fact be greater than c, but the group velocity, being capable of transmitting information, cannot, by special relativity, be greater than c.
To restructure this sentence it becomes:
The phase velocity of light can in fact be greater than c, but the group velocity of light, being capable of transmitting information, cannot, by special relativity, be greater than c.
What we are discussing is physics i.e experiments and the behaviour of any experiment is not controlled by any law i.e. SR.
The phase velocity for radio waves in the ionosphere is indeed greater than c, and that makes total internal reflection possible, and so the ionosphere can reflect radio waves.
Again how is the phase velocity of the radio waves measured measured?
This seems a very tricky, complex physical explanation of the understanding of the reflection of radio waves in the ionosphere.

### 3. See also

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

### Reflection 1 - Physics from start to finish.

To understand a physical process requires to understand all the parts of the process, and how they physical interact.
This is a recursive process because understanding a part of the process follows this same process. That means at each level of understanding the level of detail increases.
A typical case is the Periodic Table of Dmitri Medeleev and the Standard Model.
An important aspect of our understanding is to describe everything that we want to understand as clearly as possible. First the definitions used. Secondly the experiments involved, which use these definitions. Each experiment has to be described as clearly and as detailed as possible, in order to reproduce the same experiments at different locations.

As described in the above text, concepts like group velocity and phase velocity should be defined and how they are measured by means of experiment.

Generally speaking in order to understand you cannot use existing laws, because the purpose of understanding is to define or improve existing laws. You can only use existing laws if the processes they describe are completely independent of process you are discussing. For example: you cannot use SR if the process under consideration, involves light signals. Instead what you should do is to integrate in your text that part of SR which in volves light signals. The same experiments involved.

### Reflection 2 - Experiment to measure the speeds of the ionosphere and SR.

As part of my study in electrical engineering I was involved in 1964, in an experiment to measure the reflection time of a radio signal against the ionosphere (E layer) over a period of 24 hours.
As part of this project I had to write a report, but that is lost.
The purpose of the experiment was to establish the speed of the reflection layer and to compare this with an expected value.
The setup of the experiment involved a sender, a receiver and a clock. The clock was each hour synchronized by means of an external acurate clock.
Both sender and receiver were visible on an osciloscope. The difference in the time between these two signals, divided by 2 and multiplied by the speed of light in km/hour is an indication of the height of the E layer in km
The strategy of the experiment was to measure this height each hour.
Subtraction both two adjacent values gives you the average speed of the E layer in km/hour.

What I remember that the first hours of observations during midday the distance was constant and the speed zero. Around sunset the speed started to increase reached a maximum value and again became zero around midnight. We continued after sunrise and stopped and 10 o'clock. I don't remember what the results are. Most probably that the speed after sunset decreased.
However that is not so important. The most important result was that the maximum speed was much larger than expected. How come.
IMO until today, the most probably explanation of what you are measuring is not the distance of the E layer but the distance of the physical reflection layer. This layer has a certain density and does not correspond with the average distance of the E layer.
What happens is also descibed in this sentence: See en.wikipedia.org/wiki/Ionosphere#E_layer

At night the E layer weakens because the primary source of ionization is no longer present.
What that means is that the E layer is only available during daytime. During nighttime the layer more or less disappears and the distance between the reflction layer increases, implying a high speed.
 This speed can be very high and in principle even larger than the speed of light. The issue is that this calculation does not represent one object but two. The first object is an ion which reflects the radio wave during 'day time'. The second object is an ion which reflects the radio wave during 'night time'. At that moment the first ion has disappeared. This means the speed calculation reflects two objects and can have any value. What is more important, this is a physical explanation and does not require SR.

### Reflection 3

Book Review: Introducing Einstein's Relativity - Reflection 3 - Shapiro effect

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Created: 12 January 2019

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