Comments about "First observation of gravitational waves" in Wikipedia

This document contains comments about the article First observation of gravitational waves in Wikipedia
In the last paragraph I explain my own opinion.




The article starts with the following sentence.
The waveform, detected by both LIGO observatories, matched the predictions of general relativity for a gravitational wave emanating from the inward spiral and merger of a pair of black holes of around 36 and 29 solar masses and the subsequent "ringdown" of the single resulting black hole
The most important issue is a good description of the physical processes that took place.

1. Gravitational waves

1.1 Observation

1.1.1 Indirect observation

1.1.2 Direct observation

2 The GW150914 event

2.1 Event detection

2.2 Astrophysical origin

The event happened at a luminosity distance of 440(+160-180) megaparsecs (determined by the amplitude of the signal), or 1.4±0.6 billion light years, corresponding to a cosmological redshift of 0.093(+0.030-0.036) (90% credible intervals).
All these require carefull investigation. Apperently only the amplitude distance is measured.
Analysis of the signal along with the inferred redshift suggested that it was produced by the merger of two black holes with masses of 35(+5-3) times and 30(+3-4) times the mass of the Sun (in the source frame), resulting in a post-merger black hole of 62+4-3 solar masses.
All these require carefull investigation. The main line of reasoning starts with what is measured. You need a model.
The mass–energy of the missing 3.0±0.5 solar masses was radiated away in the form of gravitational waves.
During the whole lifetime of the two BH's and after the merger almost a constant amount of energy is radiated away in the form of gravitational energy.
Immediate during the merging process a certain amount of mass is destroyed in the environment surrounding the remaining BH. Part of this mass will be recaptured.

2.3 Location in the sky

2.4 Coincident gamma-ray observation

2.5 Other follow-up observations

2.6 Announcement

2.7 Awards and recognition

3 Implications

3.1 Expectations for detection of future binary merger events

3.2 Lessons for stellar evolution and astrophysics

The fact that the pre-merger black holes were present in a binary star system, as well as the fact that the system was compact enough to merge within the age of the universe, constrains either binary star evolution or dynamical formation scenarios, depending on how the black hole binary was formed.
This allows for options which use a complete different scenario.

3.3 Impact on future cosmological observation

3.4 Tests of general relativity

3.5 Speed of gravitational waves and limit on possible mass of graviton

The speed of gravitational waves (vg) is predicted by general relativity to be the speed of light (c)
In fact this prediction or assumption has nothing to do with general relativity.
The extent of any deviation from this relationship can be parameterized in terms of the mass of the hypothetical graviton. The graviton is the name given to an elementary particle that would act as the force carrier for gravity, in quantum theories about gravity.
The whole question is what does it physical means that a particle is massless?
From a phyisical point of view a graviton and a photon are very different.

4. See also

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

Reflection 1

Reflection 2

Reflection 3


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Created: 8 June 2018

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