Black Hole Evaporation: Exploring Hawking Radiation and Shrinking Black Holes

[docnet]

I am grateful for anyone for their time to answer this question.

Some theories predict black holes will evaporate and eventually disappear. From my limited understanding, Hawking's theory predicts that quantum effects near the event horizon of a black hole are responsible for blackbody radiation. I think this explains how things that fall into a black hole will evaporate. What about what's inside of the event horizon? How does anything escape from the event horizon? and what about the singularity?

 

[256bits]

Hi @docnet
That's a big peanut you are carrying.

One person who does not receive as much recognition as he should regarding black holes is
https://en.wikipedia.org/wiki/Jacob_Bekenstein
Without his leading research, Hawking might not have made the name recognition and impact he credited with.

In 1972, Bekenstein was the first to suggest that black holes should have a well-defined entropy. He wrote that a black hole's entropy was proportional to the area of its (the black hole's) event horizon. Bekenstein also formulated the generalized second law of thermodynamics, black hole thermodynamics, for systems including black holes

Blackbody radiation and black hole radiation are two different concepts.
It may very well be that black holes produce a thermal black body spectrum when evaporating.

As the black hole emits radiation it looses mass, and the event horizon shrinks in size. The objects that fell into the black hole are not recognizable as the objects anymore as they approach the singularity, but are broken into atomic particles due to the large tidal forces the closer they get. At the singularity, which is a broad general statement, since the laws of physics as we know them, are not calculable, hence the term singularity ( a mathematical concept ), a region ( call it a point ) of infinite density occurs where the atomic particles are themselves not even recognizable anymore. It is suspected that something such as a theory of quantum gravity could help explain.

Have you at least read the wiki, or some other resources on black holes, such as:
https://imagine.gsfc.nasa.gov/science/objects/black_holes1.html
https://en.wikipedia.org/wiki/Gravitational_singularity
What's inside the event horizon? Simply put, the same as what is outside - space.
How does anything escape from the event horizon? From inside, or outside? From inside, nothing.
The singularity? What about it? Our current laws produce a point of infinite density, which is the reason they break down at this point, and why it is called a singularity.

 

[PeterDonis]

I think this explains how things that fall into a black hole will evaporate.

No, that's not what Hawking radiation is. It is not things falling into the black hole evaporating. It is the hole itself evaporating.

What about what's inside of the event horizon? How does anything escape from the event horizon?

Nothing has to escape from the event horizon for Hawking radiation to occur. Hawking radiation comes from just outside the event horizon.

The real question is how Hawking radiation can decrease the mass of the hole, and hence the area of the event horizon, in violation of the area theorem, which Hawking proved, and which says that the area of the event horizon of a black hole can never decrease. The answer is that the area theorem depends on certain energy conditions being satisfied, and the quantum fields responsible for Hawking radiation violate those conditions.

 

[docnet]

thank you for taking the time to reply to my questions. I am grateful for the information

 

[haushofer]

The real question is how Hawking radiation can decrease the mass of the hole, and hence the area of the event horizon, in violation of the area theorem, which Hawking proved, and which says that the area of the event horizon of a black hole can never decrease. The answer is that the area theorem depends on certain energy conditions being satisfied, and the quantum fields responsible for Hawking radiation violate those conditions.

Do you have any references to that? :)

 

[PeterDonis]

Do you have any references to that? :)

It is discussed in Wald's monograph Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics, which is where I first encountered it. I think there are references to it in Wald's GR textbook as well.

 

[haushofer]

It is discussed in Wald's monograph Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics, which is where I first encountered it. I think there are references to it in Wald's GR textbook as well.

Thanks! I just gave away Wald's monograph, but still have its textbook :P

 

[Epsilon Eridani]

The concept of Hawking radiation fascinates me, but I am not sure I understand it very well. My main question would be what kind of particles are being evaporated from the hole? Is it just photons or other particles like atoms? Are there any "exotic" particles being evaporated in the process alongside? And a more outlandish question that I suppose would yield a negative answer - can observing the amount, type, and quantity of the evaporated particles allow for constructing an idea of what those particles were a part of before they fell into the event horizon and got disintegrated?

 

[Nugatory]

My main question would be what kind of particles are being evaporated from the hole? Is it just photons or other particles like atoms?

In principle any particle could come out if the Hawking radiation is energetic enough to produce those particles. In practice, for any black hole formed by any currently known process, the energies involved are small enough that only very low energy long wavelength photons are possible. In fact... a black hole is heated more by incoming cosmic background radiation (only a few degrees above absolute zero) than it can radiate away through Hawking radiation.