 Blackholes2 Forum Message Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Re: Finite Matter, Infinite Density... Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by nåte on March 3, 1999 10:24:51 UTC

: : : : : According to theory, Black Holes have infinte mass and infinte gravity. : : : : : How then, can there be an event horizon? If the force of gravity from the Black : : : : : Hole is infinite, then it would not dissipate with distance and therefore would be : : : : : the same everywhere, for an infinite distance. If my understanding of infinity is : : : : : correct, then Black Holes must have a finite mass and gravity if there is to be an : : : : : an event horizon.....right?

: : : : actually I think you have the theory off a bit.

: : : : BH have (at their singularities) infinite density, : : : : not infinite mass; for the reason you state in the : : : : latter portion. : )

: : : : this is why there are different sizes of BH as well.

: : : : For instance the gravitational field surrounding a : : : : BH may as well be the mass of 50 of our suns, and : : : : the event horizon be 1500 feet across.

: : : Thanks, the finite mass aspect clears a few things up.

: : : It still doesn't deal with the infinite gravity though. : : : How is it possible to measure the dimensions of a : : : gravitational field under conditions of infinite gravity?

: : A BH does not have infinite gravity whatsoever. : : I'm not sure where you heard this from.

: : Let me give you an example...

: : Take for instance a massive star in its dying phase. : : As the nuclear fusion begins to slow, the equalibrium : : balance of the force of fusion expelling outwards falls : : below the force of gravity collapsing inwards.

: : As the crushing force is creating a denser mass, keep : : in mind the mass does not change, thus the gravitational : : field has not changed.

: : Now, imagine the star has collapsed to the critical size : : called the, "Schwarzchild radius". This is the diameter : : of the star where space has become "potentially" infinitely : : curved. Thus light cannot even escape this boundary. : : IOW, the escape velocity required to escape this event horizon : : becomes infinitely close to the speed of light.

: : Now, lets take a step back and look at this BH. Has : : its gravity increased? No... In fact, imagine this : : particular BH side by side with its earlier form as : : the star. The BH and star have exactly the same mass (accounting : : the BH hasn't drawn anything in) as the star does. (in its early, : : pre-collapse stage) The only thing that has increased : : is the density. If you measured the gravity attraction : : of the BH at a given distance, you would measure the : : same gravity measurement of the same star at the same : : distance...

: : -nåte

: Thanks nate, you obviously know alot more about this than I. : I got the infinity thing from a show on the Discovery Channel. : The guy who was their "expert" described a BH as having infinite : mass and infinite gravity. The logic of that didn't seem to fit, : thus the posting on here. Infinite space, I can almost deal with, : but infinite mass seemed to have much graver implications. :

no prob John, and thank you.

I would even qualify the notion of anything existing as an actual infinity within our cosmos. There are 'potential' infinities, but I believe there are no 'actual' infinities.

For example: A potential infinity would be synonomous to say that there are an infinite number of points between point A and B. But the question that distinguishes between the actual and potential is this... Why is it that one can traverse across a room from point A to point B if it contained an infinite # of irreducible points? This logic befudled an early scientist into believing that because of this phenomena, we must be living in an illusion.

However, this merely distinguishes the case between an actual infinity and a potential one. One can traverse across a potential infinity, but cannot across an actual.

Thus, how could space be infinitely large and exist eternally? This brings about too many paradoxes and flies in the face of Thermodynamics. If space has eternally existed, then due to 2LOTD, the universe should have ceased to exist an eternity ago. Its kinda like trying to jump out of a bottomless pit. Where does it start?

-nåte  