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Astrophysics/Black holes


The black hole is a point of extreme density and mass, which is responsible for the stretching in space time in that region. Is this possible, for perhaps a super massive black hole, to attain such high mass that it simply stretched the space to its limit, finally breaking through it, into something outside the universe? If we see at this problem in a parallel universe frame of mind, where we believe the universes to be suspended like bubbles, or infinite sheets, does that provide any logic that at that point the space time of our universe is "ripped" to show a gaping hole, revealing something outside the universe? Will it appear just like a black hole, light simply leaving our universe from that hole into oblivion or something else outside the universe?


I think the problem may be making a direct comparison between the standard (e.g. Kerr type ) black hole and the supermassive variety. When one uses terms like "universes suspended like bubbles" and "infinite sheets" this more or less implies M-brane theory (or M-theory) but there is no real agreement that one can make such extrapolations. Thus, the new M-brane collision theory, say for the origin of the Big Bang,  kind of eliminates most discussions of "singularities" there that are analogous to those for black holes.  

I believe that model also eliminates comparisons to "such high mass" regimes that the result is "stretching space to its limit".  Recall the well known Schwarzschild radius is defined:

R(s) = 2GM/c^2

where G is the Newtonian gravitational constant, c is the speed of light in vacuo, and M is the gravitating mass. Once a stellar remnant collapses within this radius, light cannot escape and the object is no longer visible, hence effectively "air tight". There is also the possibility to engulf added mass, say in a binary star system. It is a characteristic radius associated with a stellar mass collapsed to a black hole.

Here's the problem: the mean density of a supermassive black hole is defined as the mass of the black hole m' divided by the volume V' within its Schwarzschild radius R(s). Thus,

rho (bh) = m' / V'(R(s))

But, in the case of some supermassive black holes the above computation can lead to rho (bh) values less than the density of water (1.4 g/ cm^3 or 1400 kg/ m^3) This is because, if you look at the Schwarzschild equation, the Schwarzschild radius R(s)  ~  M (directly proportional to mass) while rho(bh)  ~ 1/ V'  (i.e. the density is inversely proportional to the black hole volume.)

Now, since the typical supermassive black hole will have a radius of tens of thousands of parsecs (1 pc = 3.26 LY) this implies a super vast volume. Since the volume of a spherical object V ~ r^3 (i.e. is directly proportional to the cube of the radius), the density of a black hole is inversely proportional to the square of the mass, so higher mass black holes have lower average density.

The issue or question of "ripping space" (actually space-time) to its limit, is therefore an issue of density more than mass. Since the supermassive hole doesn't make this cut, given its enormous volume, we don't need to worry about it.

One more thing you might wish to consider in regard to the standard stellar - collapsed black holes is a remark Kip Thorne made in Ch. 5 ('Warping Spacetime')  in his book:  'The Future of Theoretical Physics and Cosmology', Cambridge Univ. Pres, 2003:

"One might suspect it is the singularity's mass (or associated g-force) that warps the black hole's space. Not so, it turns out. The hole's space is warped by the enormous energy of its warpage. Warpage begets warpage in a *non-linear* self-boot strapping manner that is a fundamental feature of Einstein's general relativity laws."

His diagrams (p. 78) are also excellent in explicating this, but alas, copyright laws prohibit reproduction of them to send you. I can only reference them.

Hopefully you will find this information useful!  


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Philip A. Stahl


I specialize in stellar and solar astrophysics. Can answer questions pertaining to these areas, including: stellar structure and evolution, HR diagrams, binary systems, collapsars (black holes, neutron stars) stellar atmospheres and the spectroscopic analysis of stars as well as the magnetohydrodynamics of sunspots and solar flares. Sorry No homework problems done or research projects! I will provide hints on solutions. No nonsense questions accepted, i.e. pertaining to astrology, or 'UFOs' or overly speculative questions: 'traveling through or near black holes, worm holes, time travel etc. Absolutely NO questions based on the twaddle at this Canadian site: purporting to show a "new physics". Do not waste my time or yours by wasting bandwidith with reference to such bunkum.


Have constructed computerized stellar models; MHD research. Gave workshops in astrophysics (stellar spectroscopy, analysis) at Harry Bayley Observatory, Barbados. More than twenty years spent in solar physics research, including discovery of SID flares. Developed first ever consistent magnetic arcade model for solar flares incorporating energy dissipation and accumulation. Developed first ever loop-based solar flare model using double layers and incorporating cavity resonators. (Paper presented at Joint AGU/AAS Meeting in Baltimore, MD, May 1994)

American Astronomical Society (Solar physics and Dynamical astronomy divisions), American Geophysical Union, American Mathematical Society, Intertel.

Papers appearing in Solar Physics, Journal of the Royal Astronomical Society of Canada, Journal of the Barbados Astronomical Society, Meudon Solar Flare Proceedings (Meudon, France). Books: 'Fundamentals of Solar Physics', 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level', 'Astronomy & Astrophysics: Notes, Problems and Solutions', 'Modern Physics: Notes, Problems and Solutions'

B.A. degree in Astronomy; M.Phil. degree in Physics - specializing in solar physics.

Awards and Honors
Postgraduate research award- Barbados government; Studentship Award in Solar Physics - American Astronomical Society. Barbados Astronomical Society award for service (1977-91) as Journal editor.

Past/Present Clients
Caribbean Examinations Council (as advisor, examiner), Barbados Astronomical Society (as Journal Editor 1977-91), Trinidad & Tobago Astronomical Society (as consultant on courses, methods of instruction, and guest speaker).

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