Comments about "Compton ***" in Wikipedia

This document contains comments about the article Curved_spacetime in Wikipedia
In the last paragraph I explain my own opinion.

Contents

Reflection

Introduction

The article starts with the following sentence.

1. Introduction

Newton's theories assumed that motion takes place against the backdrop of a rigid Euclidean reference frame that extends throughout all space and all time.
That maybe true, but I doubt this. The most important issue what is Newton world view. See Comment 1 I doubt if Newton assumed that this reference frame exists. It is an abstract concept consisting of a 3D frame with equally length rods and clocks at all cross sections.
Gravity is mediated by a mysterious force, acting instantaneously across a distance, whose actions are independent of the intervening space.
Gravity is mediated between objects by means of a force. This force can be considered as a stream of mass less particles which are invisible.
In contrast, Einstein denied that there is any background Euclidean reference frame that extends throughout space. Nor is there any such thing as a force of gravitation, only the structure of spacetime itself.
When Einstein does not use some form of a reference frame, which is used to capture all observations and the time of these observations, it becomes difficult to compare the results of Newton with these of Einstein.
  In spacetime terms, the path of a satellite orbiting the Earth is not dictated by the distant influences of the Earth, Moon and Sun. Instead, the satellite moves through space only in response to local conditions.
This sentence is not clear, because it consists of many unclear concepts
From a physical point of view any satelillite
The path
Since spacetime is everywhere locally flat when considered on a sufficiently small scale, the satellite is always following a straight line in its local inertial frame.
If one studies the planets around the sun are these planets following a straight line in the local inertial frame of the Sun?
I expect not, that means you have in some way to divide the path of each planet in small sections which are considered straight. How is that done in practice?
We say that the satellite always follows along the path of a geodesic.
Completely empty sentence
No evidence of gravitation can be discovered following alongside the motions of a single particle.
Completely empty sentence.
In any analysis of spacetime, evidence of gravitation requires that one observe the relative accelerations of two bodies or two separated particles.
In order to observe accelerations you need a reference frame, physical at rest.
In Fig. 5-1, two separated particles, free-falling in the gravitational field of the Earth, exhibit tidal accelerations due to local inhomogeneities in the gravitational field such that each particle follows a different path through spacetime.
The definition of local inhomogeneities are objects of mass?
The tidal accelerations that these particles exhibit with respect to each other do not require forces for their explanation.
Strange sentence.
Rather, Einstein described them in terms of the geometry of spacetime, i.e. the curvature of spacetime.
But how do you want these descriptions are correct? You need observations
These tidal accelerations are strictly local.
That needs them even more difficult to prove them as being correct.
It is the cumulative total effect of many local manifestations of curvature that result in the appearance of a gravitational force acting at a long range from Earth.

2. Curvature of time

3. Curvature of space

4. Sources of spacetime curvature

4.1 Energy-momentum

4.2 Pressure and stress

5. Experimental test of the sources of spacetime curvature

5.1 Definitions: Active, passive, and inertial mass

5.2 Pressure as a gravitational source

5.3 Gravitomagnetism

6. See also

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Created: 3 September 2024

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