Comments about "Black body" in Wikipedia

This document contains comments about the document "Black body" in Wikipedia
In the last paragraph I explain my own opinion.



The article starts with the following sentence.
A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
A black body in thermal equilibrium emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone.

1. Definition

2. Idealizations

2.1 Cavity with a hole

2.2 Transmission, absorption, and reflection

2.3 Kirchhoff's perfect black bodies

3. Realizations

3.1 Cavity with a hole

3.2 Near-black materials

3.3 Stars and planets

3.4 Black holes

A black hole is a region of spacetime from which nothing escapes.
A black hole is an object in space that emits gravitational radiation. It does not emit electromagnetic radiation.
Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return.
The black hole has a radius called event horizon. The radius is fuzzy, that means the BH has no physical well defined boundary.
It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, making it almost an ideal black body
It should be mentioned that this name is completely based from human perspective and does not say anything of the object involved.
The name is based because the Black Hole emits no electro magnetic radiation. At least that is the assumption
next as part of this sentence we read:
(radiation with a wavelength equal to or larger than the radius of the hole may not be absorbed, so black holes are not perfect black bodies).
gravitational radiation will go through a BH undisturbed.
Physicists believe that to an outside observer, black holes have a non-zero temperature and emit radiation with a nearly perfect black-body spectrum, ultimately evaporating.
The physical behaviour of a black hole has nothing to do with an outside observer.
The physical question to ask is: What is the inside temperature of a BH? Is it absolute zero (= -273.15 C or 0 K)?
IMO there is reason to assume that the inside temperature is 0 K.
What is also possible that certain processes like superconductivity take place inside a BH.
The mechanism for this emission is related to vacuum fluctuations in which a virtual pair of particles is separated by the gravity of the hole, one member being sucked into the hole, and the other being emitted.
To relate evaparation with vacuum fluctuations is not very obvious. The surrounding of a BH is not a vacuum. IMO a BH is much more a boiling pot, like the surface of the sun.
Anyway it is very difficult to assume that BH will evaporate except if other Black Holes are available.
See also: VB BHmerger operation

3.5 Cosmic microwave background radiation

4. Radiative cooling

5. See also

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

Reflection - Black hole

A black hole is not a black body or an object with a black color. A black hole has no color.


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Created: 9 April 2016

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