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 Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Re: Do You Think They Can Go Nova Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by nåte on March 5, 1999 01:52:12 UTC

: : : Do black holes ever cease to exist?

: : It is believed so.

: : Stephen Hawking promotes this theory called, : : "Hawking radiation",that eventually extinguishes : : the black hole.

: : His reasoning is this:

: : Take a empty can for example, imagine you have a : : many particles with each having X amount of : : energy. Imagine that in order for one of those : : particles to 'escape' the opening of the can it : : is needed to have 2X of energy. How does a particle : : escape?

: : Well the analogy has been given as imagining a bunch : : of frogs in a bucket, not one frog is capable of : : jumping over the edge, but perhaps it is possible : : if one frog is sitting on another and the instant : : the one frog jumps (on bottom) the other frog jumps : : as well at the crest of the first frogs jump. Well, : : in theory the frog on top will escape. Thus extinguishing : : the BH in a finite amount of time.

: : This theory goes for the particles that are 'beyond' : : the event horizon of the BH. (if that is even imaginable)

: : I personally have problems with some of the intracacies : : within the theory, but can see it in operation outside : : of the EH, not beyond it.

: : -nåte

: do you think that there is a critca mass were the black hole could no longer hold its infinate density and would rapidly expand and blow up?

No, and for this reason. If there were an unstable state at any point in the existence of a BH, the star would have rapidly expanded and blew up before it ever could contract to its critical schwarzchild radii. Therefore, for a BH to be initially called a BH, it would possess properties that would not allow itself in ceasing to exist as a BH in the first place. IOW, I've never read or heard of a BH going 'supernova'.

: do you think it would cause a strobing affect Language Removed star shot off extra mass it coulnt hold and reformed into a black hole?

This goes back to my point above. If a "BH" ever 'shot off extra mass' it was never a BH in the first place.

The phenomena that accompanies a BH in increasing its mass is that of the event horizon becoming ever larger in diameter. For example, say the earth was compressed by some external means to the critical mass per volume (density) that would impose an event horizon. If we measured the distance across the field we would measure, say... 20 feet across. Now, take for instance our sun. If it was also compressed by an external force the EH would be say, 500 feet across. What I'm trying to suggest is that no matter how much initial mass was present at the collapse, once it has collapsed, it will remain so because of its infinite density. It may acquire more mass, but this only makes the diameter of the EH expand.

-nåte