Ahhh yes. Good old "Black Holes and Time warps" has provided an informative tid bit of information fo you to swallow.

Simplified version: Black holes grow right? We've got our couple solar mass one here and a million solar mass one there. Why? Ahhhh here is the interesting part. Part of this was a revelation of stephan Hawking called the black hole area therom.

Black holes are cosmic vaccum cleaners. And as my little title suggest "black holes are fricken wierd".

Iam not going to write 5 pages. I will try to shorten it up as much as possible.

See basically black holes are a warpage of spacetime. So how can a black hole increase in size?

See it was proven previously that black holes have no "hair". Meaning they have no magnetic field lines, ect. of their own. And just the same, it was proven that ANYTHING that entered a black holes horizon could not exit. Thus a black hole could not evaporate.

So how does it increase in size? See this Black hole area therom was almost identical to the second law of thermo dynamics. If one only changed the words "horizon areas" by "entropy", it was practically the second law.

So this graduate student named Jacob Bekenstein relized what this meant. If Black holes grow, and the area therom is the same as the second law of thermo dynamics, than the holes area in some deep sense is its Entropy:

Entropy is the logarithm of the number of ways that all the atoms and molecules iin out chosen region can be distributed, without changing that region's macroscopic appearence.

But see here is where the problem arised. Hawking disaggreed and said that a black hole doesn't have entropy. But here is a problem. This violates the second law of thermo dynamics that states that entropy is always increasing.

So, Bekenstein theorized that the explanation is that the holes surface area grows to accomadate the increasing entropy that it consumes.

So if the holes horizon is the holes entropy, then the surface gravity would have to be the holes temperature in disguise and that the temp would not be zero. BUT!!! and thing that has a nonzero temperature must emit radiation, at least a little. This completely clashes with the thought that black holes consume and dont let out anything at all! Wow!

These are some of the steps that led to the discovery that blackholes do radiate and will eventually explode.

Hopefully more to come if I have time!

Later
T


Sorry, its alittle Patchy! I have to study for a chemistry test!

Black holes are cosmic vaccum cleaners.

A common misconception.

So how can a black hole increase in size?

In-falling matter adds to the mass.

See it was proven previously that black holes have no "hair". Meaning they have no magnetic field lines, ect. of their own.

A black holes parameters are it's mass, vector field charges and angular momentum - no hair theorem.

So how does it increase in size? See this Black hole area therom was almost identical to the second law of thermo dynamics.

A change in a black holes mass is related to a change in the area of the horizon and actually resembles the First Law of Thermodynamics that relates the change in energy with the change in entropy.

Hawking disaggreed and said that a black hole doesn't have entropy.

Hawking proposed the Area Theorem which resembled the Second Law of Thermodynamics which states that entropy will always increase. Later on he came up with the theory we now understand as Hawking Radiation.

These are some of the steps that led to the discovery that blackholes do radiate and will eventually explode.

Don't you mean, eventually "evaporate."

How can you describe them then? In lamens terms, they suck up stuff, eventually "evaporate" and thats about it. So how could you better describe it for the lay person

Isn't the common conception that a black hole is an infinte space time warpage?

Yes its mass, agular momentum and charge are the only three things that you need to know to calculate everything else. There isn't a "no hair therom". Its an analogy. And just as I described: Meaning they have no magnetic field lines, ect. of their own. Am I wrong?


Exactly what I described except I said the 2nd law? Doesnt the 2nd law describe entropy?

And yes I did mean "evaporate"?

Are you a astronomer, ect Q? Just curious. Your very knowledgeable


Later
T

Tristan

So how could you better describe it for the lay person

How about this instead - a black hole is a region of space containing so much concentrated mass that anything which comes near it cannot escape its gravitational pull.

Isn't the common conception that a black hole is an infinte space time warpage?

Certainly any massive object such as a black hole will distort or warp the space and time near it to the extreme. According to general relativity, gravity is a manifestation of the curvature of spacetime so, at the singularity of a black hole (r=0) the curvature is infinite.

There isn't a "no hair therom". Its an analogy.

The no hair theorem simply states that mass, charge and angular momentum are the only properties a black hole possesses. No analogy necessary.

And just as I described: Meaning they have no magnetic field lines, ect. of their own. Am I wrong?

Yes, rotating black holes can generate magnetic fields.

Doesnt the 2nd law describe entropy?

Yes, and to keep it straight, just remember that energy is the subject of the first law and entropy is the subject of the second law.

Sounds a bit like the "Black Star" idea that was originally concieved to explain the phenomena. Simply stated, a star that is so dense that its escape velocity is the speed of light (or higher? Icant remember).

Isn't that what a black hole is!? A warpage of spacetime. You keep on describing it as a "black Star"! As I described above.


There is no such thing as "The No-Hair Theorem" am i wrong? "No-Hair" is a term/analogy to describe a black hole that cant have magnetic field lines, ect.

IF it has an accretion disk, no?

Later
T

Black hole = black star.
Wrong. The no-hair theorem says that the black hole itself only has three physically observable characteristics: charge, angular momentum, and mass. These are the only quantities you can measure of the black hole itself (the "stuff" inside the event horizon). Outside the black hole's event horizon, there can certainly exist magnetic fields.

- Warren

Now I know that is wrong. So your telling me that If I went into a black hole (provided I could survive) I would them plummet into a star that is going through the fusion process?

There can't be magnectic field lines THREADED THROUGH a black hole unless it has an accretion disk, no?

Later
T

it is theorised that the 2nd law of thermodynamics is kept alive by the black hole, either by spontanious generation of particles very near the event horizon, or shift of entropy balance in other dimensions than that we can directly obseve.

When did I say anything about fusion?

Any object with gravity strong enough to prevent the escape of light is not going to be like any normal star. There is no known physical mechanism that can explain how such an object would not succumb to gravity and collapse to a singularity.

Point of fact, we are disallowed from ever knowing what happens inside the event horizon -- so no one can ever tell you for sure what happens there.
Certainly, why not?

- Warren