• 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.
Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light.
Gravitational waves are not special for GR, they can also be studied using Newton's Law. Starting point is the Force of gravity. For a mass at rest the corresponding field is static. For two rotating masses the field is dynamic i.e. rotating. See next.
The whole issue is how much energy is available in gravitaional radiation. This energy loss is equivalent with mass loss.
Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate at infinite speed—showing one of the ways the methods of classical physics are unable to explain phenomena associated with relativity.
Newton's Law assumes that Gravitational radiation propagates instantaneous.
Using Newton's law starting from a binary star system a third object will wobble synchroneous with the movement of the two first independent of distance.
When gravitational radiation propagates with the speed of light this "wobbling" will be delayed as a function of distance.
The difference with Newton's Law and GR is that the predicted power loss in GR is much larger than with Newton's Law (including finite speed of gravity propagation)
The first indirect evidence for the existence of gravitational waves came from the observed orbital decay of the Hulse–Taylor binary pulsar, which matched the decay predicted by general relativity as energy is lost to gravitational radiation.
It is important to study the Einstein Field equations specif the part which quantifies the amount of energy lost to gravitational radiation.

### 1. Introduction

In certain circumstances, accelerating objects generate changes in this curvature, which propagate outwards at the speed of light in a wave-like manner.
IMO all binary systems should generate gravitational waves. Including all the planets around the Sun.
As a gravitational wave passes an observer, that observer will find spacetime distorted by the effects of strain.
Popular language. In reality gravity waves are produced by rotating objects. An outside observer, also an object, will be influenced by these waves. If this is a long object, different parts will be influenced different forces and can cause strain.
The magnitude of this effect decreases in proportion to the inverse distance from the source
Newton's Law predicts the same.

### 2. Speed of gravity.

The speed of gravitational waves in the general theory of relativity is equal to the speed of light in a vacuum, c.
Physical the speed of gravity (the speed of gravitons) and the speed of light (the speed of photons) are something completely different.
It is an on going discussion in sofar the speed of light is constant and or is influenced by gravity.
Formally, c is a conversion factor for changing the unit of time to the unit of space.
Space in GR is considered mathematical space and not a physical space.
C*dt = c * (t2-t1) defines a distance that light has travelled.
This makes it the only speed which does not depend either on the motion of an observer or a source of light and / or gravity.
The speed of a photon, considering the photon travelling in the universe and considering the universe as one reference frame, has nothing to do with the speed of any observer.

### 3. History

In 1905, Henri Poincaré first proposed gravitational waves (ondes gravifiques), emanating from a body and propagating at the speed of light, as being required by the Lorentz transformations and suggested that, in analogy to an accelerating electrical charge producing electromagnetic waves, accelerated masses in a relativistic field theory of gravity should produce gravitational waves
It is nothing special that a rotating object should produce a rotating field i.e. gravitational waves. The issue is the speed with which the field propagates.

### 6.1 Energy, momentum, and angular momentum

Water waves, sound waves, and electromagnetic waves are able to carry energy, momentum, and angular momentum and by doing so they carry those away from the source.
The whole question is how much mass they can carry away.

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Created: 2 November 2017
Updated: 31 July 2021

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