Black Hole: Infinite Density, Infinite Buoyancy?

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Discussion Overview

The discussion revolves around the properties of black holes, particularly focusing on the concepts of infinite density and buoyancy within black holes. Participants explore theoretical implications, mathematical formulations, and the nature of singularities in the context of general relativity and quantum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that if a black hole has infinite density, then objects would float inside it due to infinite buoyancy, leading to questions about the cancellation of these forces.
  • Others propose that quantum effects might prevent singularities from reaching infinite parameters.
  • One participant argues that only the singularity at the center of a black hole has infinite density according to general relativity, while the space inside the event horizon is described as empty space and infalling matter.
  • A mathematical expression for the density of a non-rotating black hole singularity is presented, with claims that infinities do not exist in this context.
  • Another participant asserts that there is no "inside" to a black hole singularity, describing it as a point.
  • Some participants discuss the Planck density as a potential limit in the physical universe, suggesting it may be a relevant consideration in the discussion of black hole densities.
  • There are claims regarding the dimensionality of solutions in general relativity, with assertions that solutions with fewer than four dimensions are invalid and lead to infinities.

Areas of Agreement / Disagreement

The discussion features multiple competing views regarding the nature of black hole singularities, the implications of infinite density, and the validity of mathematical models. No consensus is reached on these topics.

Contextual Notes

Participants express uncertainty about the implications of infinite density and buoyancy, and the discussion includes references to classical general relativity and quantum mechanics without resolving the mathematical complexities involved.

Ryan H
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If a black hole has an infinite density, then one would think that anything would float inside of it. And since it's infinitely dense, the object(s) being pulled in would have an infinite buoyancy, causing it to be shot back out of the black hole at a seemingly infinite speed. So why don't these two forces cancle each other out?
 
Astronomy news on Phys.org
quantum effects probably prevent a singularity from reaching zero/infinite parameters
 
Ryan H said:
If a black hole has an infinite density, then one would think that anything would float inside of it. And since it's infinitely dense, the object(s) being pulled in would have an infinite buoyancy, causing it to be shot back out of the black hole at a seemingly infinite speed. So why don't these two forces cancle each other out?
Only the singularity at the center would have infinite density according to general relativity, inside the event horizon is empty space (and infalling matter) just like outside the event horizon.
 

'non-rotating' Classical Universe-Schwarzschild Singularity Density solution for a one-dimesional 'point-like' object:
[tex]\boxed{\rho_u = \frac{M_u}{2} \sqrt{ \frac{c^3}{\hbar G}}}[/tex]
[/color]
BH Singularity Density infinities do NOT exist.

Reference:
https://www.physicsforums.com/showpost.php?p=370142&postcount=24
 
There is no "inside" to a BH singularity (point).
 
Orion1 said:
'non-rotating' Classical Universe-Schwarzschild Singularity Density solution for a one-dimesional 'point-like' object:
[tex]\boxed{\rho_u = \frac{M_u}{2} \sqrt{ \frac{c^3}{\hbar G}}}[/tex]
[/color]
BH Singularity Density infinities do NOT exist.

Reference:
https://www.physicsforums.com/showpost.php?p=370142&postcount=24
Is this equation something you derived yourself based on your own ideas, or did you get it from a textbook or something written by a professional physicist? The derivation you gave on that thread seemed to involve both QM and GR...would you agree that according to classical GR alone, the singularity has infinite density?
 
I would argue the Planck density is the limit in the physical universe.
 
Planck Philosophy...

JesseM said:
Is this equation something you derived yourself based on your own ideas, or did you get it from a textbook or something written by a professional physicist?


[tex]\boxed{\rho_u = \frac{M_u}{2} \sqrt{ \frac{c^3}{\hbar G}}}[/tex]

The solution for this 'non-rotating' classical schwarzschild singularity density for a one dimensional 'point-like' object was derived by me based on research on these physical models.

Note that the Schwarzschild solution is only a solution for Schwarzschild BHs with zero angular momentum , this is a highly improbable state.

Neutron star spin increases with increased density, therefore an object generating in the core of a neutron star or supernova without spin is...impossible. Only BHs with angular momentum can exist in the Universe, a rotating Kerr BH.

JesseM said:
Would you agree that according to classical GR alone, the singularity has infinite density?

The Classical General Relativity model is based upon four total dimensional space-time [tex]n_t = 3 + 1 = 4[/tex] (3 space + 1 time). Solutions for models for that contain dimensions of less than four are not valid solutions in the Universe.

The classical solution stated for 1 dimension is actually 2 dimensions [tex]n_t = 1 + 1 = 2[/tex] (1 space + 1 time), because solutions with with a total dimensional range of less than 4 [tex]n_t < 4[/tex] cannot exist in the Universe, all solutions for total dimensional ranges between 0 and 3 are not real valid solutions because they cannot exist in a four total dimensional General Relativity Universe.

Classical General Relativity models based upon 0 to less than 2 total dimensions are typical of producing solutions with 'infinities', and is only a division by zero in an 'undefined' model.

This solution is based upon 2 dimensional space, the singularity described 'exists' in only 2 space dimensions (and 1 time) [tex]n_t = 2 + 1 = 2[/tex] (2 space + 1 time). [tex]n_t = n_s + n_t[/tex].

Classical Schwarzschild Singularity Dimension Number:
[tex]n_s = 2[/tex] - dimension #
[tex]dV_s = \pi r_p^2[/tex] - volume
[tex]L = 0[/tex] - angular momentum

Solution for 'non-rotating' Classical Schwarzschild Singularity Density for a two dimensional 'point-like' object: (flat disc)
[tex]\rho_s = \frac{dM_s}{dV_s} = \frac{dM_s}{\pi r_p^2} = \frac{M_u c^3}{\pi \hbar G}[/tex]

[tex]\boxed{\rho_u = \frac{M_u c^3}{\pi \hbar G}}[/tex]

[tex] \begin{picture}(100,100)(0,0)<br /> \put(0,0){\circle{3}}<br /> \put(0,0){\line(1,0){100}}<br /> \put(0,0){\line(0,1){100}}<br /> \put(0,33){\circle{3}}<br /> \put(34,55){\circle{3}}<br /> \put(67,77){\textcolor{red}{\circle{3}}}<br /> \put(67,77){\textcolor{blue}{\circle{6}}}<br /> \put(100,100){\circle{3}}<br /> \put(100,5){{n}}<br /> \put(5,100){{ln p}}<br /> \end{picture}[/tex]

Chronos said:
I would argue the Planck density is the limit in the physical universe.
In a four dimensional space-time physical Universe, the average Planck density is a solution and a physical 'limit' in the Universe.

Based upon the current logarithmic slope in the chart, at what density value does the slope cross the y-intercept?
[/color]
Reference:
https://www.physicsforums.com/showpost.php?p=370142&postcount=24
 
Last edited:

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