Why does A black hole need a massive center

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Discussion Overview

The discussion revolves around the nature of black holes, specifically questioning the necessity of a singularity at their center and exploring the implications of mass distribution and gravitational effects within and around black holes. Participants examine concepts related to general relativity, the event horizon, and the behavior of objects approaching black holes, including potential orbits and gravitational interactions.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question why a singularity is required at the center of a black hole, suggesting that if all mass were contained within the event horizon, it might still exert the same gravitational effects.
  • There is a proposal that the mass of a black hole could behave like a crystal, with each piece of mass pulling together as a whole.
  • Concerns are raised about the behavior of mass approaching the speed of light, including whether it would orbit or experience escape velocity as it nears the center of the black hole.
  • One participant asserts that once inside the event horizon, all paths lead to the singularity, as per general relativity, but acknowledges that the existence of a singularity is still debated.
  • Another participant emphasizes that the geometry of a black hole is fundamentally different from typical spatial concepts, noting that the singularity is not a visible point but rather a future event within the collapsing geometry.
  • There is a discussion about the limits of circular orbits, with the assertion that orbits can only exist outside the event horizon, specifically at a radius of r = 3M.
  • Some participants argue against the idea that gravitational strength weakens as one approaches the center, stating that it actually increases to infinity at the singularity.
  • One participant mentions the photon sphere, where orbits are not possible inside this radius, which lies outside the event horizon.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of singularities, the behavior of mass near black holes, and the implications of general relativity versus quantum theory. The discussion remains unresolved with no consensus on these points.

Contextual Notes

Participants highlight limitations in understanding the interior of black holes, including the inability to observe or gather information once inside the event horizon. The discussion also reflects the ongoing debate between general relativity and quantum mechanics regarding the existence of singularities.

russinnj2000
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Was thinking about this why is it a requirement that the center of a black hole be a singularity? If the event horizon contained all the mass of a black hole would it still not have the same effect on it's surroundings? Why could it not be similar to a a crystal where as each molecular link or in this case each piece of mass was pulling as a whole? Further as the mass accelerated towards the speed of light unless it was directly heading at the exact center of the black whole would it not orbit? Or be constantly approaching an escape velocity? If it was Orbiting at near the speed of light would it not increase the likelihood of other particles orbiting in a similar fashion? also even if it were to per say have a dead center pass on the central point of the black whole would the gravitational field not get weaker not stronger as it approached the absolute center? As all the mass surrounding as it approached the center would be pulling it away from the center equally? (Sort of the Gravitational Bungee Jump)
 
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In the framework of general relativity, once an object is inside the event horizon, there is no world line, no matter how accelerated, that does not end up in the singularity.

Whether a singularity actually exists or not inside a black hole is up for interpretation. We can only view and observe a black hole from the outside of the event horizon. Once we are inside, we can't get information out, so there's no way to make observations. All we can say is that according to the currently generally accepted theory of gravity, once inside the black hole, the eventual future of any object is in a singularity.
 
The main problem with saying there is a singularity at the center of a black hole is that current physics is undecided. General relativity leads to the singularity. Quantum theory says there is no such thing. The question remains unresolved.
 
So my next question would be if you were approaching the event horizon approaching the speed of light would as you approached it and other objects which fell in approached it as well behind you observe your acceleration as an expansion regardless. It may as though appear to you nearing the horizon as if you were in an ever expanding space without explanation as to what was pulling you apart?
 
To my layperson understanding, that would appear to be happening if you were looking directly in front or behind you, but not if you were looking in any other direction! To visually 'see' what you suggest, 'you' would have to be shrinking.

Damo
 
russinnj2000,

The geometry of a black hole is different from what you're imagining. Dramatically different!

russinnj2000 said:
Was thinking about this why is it a requirement that the center of a black hole be a singularity?
A black hole does not have a "center" in the usual sense. As you enter the hole, the singularity is not something you can see in front of you. Inside of the hole, the coordinates we call r and t switch roles - r becomes the time coordinate, while t is one of the space coordinates. So the singularity at r = 0 is nowhere beside you, it is in your future. The geometry inside the hole is collapsing, taking you with it, and eventually (at time r = 0) everything inside reaches the singularity.

If the event horizon contained all the mass of a black hole would it still not have the same effect on it's surroundings? Why could it not be similar to a a crystal where as each molecular link or in this case each piece of mass was pulling as a whole?
Any infalling matter cannot remain at the event horizon. Also, you seem to be imagining the mass is spread out inside, filling the hole. In a Schwarzschild black hole, the interior of the event horizon is vacuum. There is no matter inside. If matter does fall into the hole from outside, the matter that preceded you will not be in front of you, it will be in your past! The matter that falls after you do will be in your future and you cannot be affected by it.

Further as the mass accelerated towards the speed of light unless it was directly heading at the exact center of the black whole would it not orbit? Or be constantly approaching an escape velocity?
There's a limit. The only circular orbits lie outside the hole. The smallest circular orbit is at r = 3M (the horizon is at r = 2M). Matter nearing the speed of light (or light itself) could orbit at this radius, r = 3M, but once inside this limit it would death spiral inward and fall through the horizon.

If it was Orbiting at near the speed of light would it not increase the likelihood of other particles orbiting in a similar fashion?
No.

also even if it were to per say have a dead center pass on the central point of the black whole would the gravitational field not get weaker not stronger as it approached the absolute center?
No. the strength increases all the way to r = 0, where it is infinite.

As all the mass surrounding as it approached the center would be pulling it away from the center equally? (Sort of the Gravitational Bungee Jump)
As I said above, that does not happen.
 
russinnj2000 said:
Was thinking about this why is it a requirement that the center of a black hole be a singularity? If the event horizon contained all the mass of a black hole would it still not have the same effect on it's surroundings? Why could it not be similar to a a crystal where as each molecular link or in this case each piece of mass was pulling as a whole? Further as the mass accelerated towards the speed of light unless it was directly heading at the exact center of the black whole would it not orbit? Or be constantly approaching an escape velocity? If it was Orbiting at near the speed of light would it not increase the likelihood of other particles orbiting in a similar fashion?

The distance at which something must be traveling the speed of light in order to maintain an orbit is is known as the photon sphere. Inside the photon sphere orbits are not possible. The photon sphere actually lies outside] of the event horizon.
 
russinnj2000 said:
Was thinking about this why is it a requirement that the center of a black hole be a singularity? If the event horizon contained all the mass of a black hole would it still not have the same effect on it's surroundings? Why could it not be similar to a a crystal where as each molecular link or in this case each piece of mass was pulling as a whole? Further as the mass accelerated towards the speed of light unless it was directly heading at the exact center of the black whole would it not orbit? Or be constantly approaching an escape velocity? If it was Orbiting at near the speed of light would it not increase the likelihood of other particles orbiting in a similar fashion? also even if it were to per say have a dead center pass on the central point of the black whole would the gravitational field not get weaker not stronger as it approached the absolute center? As all the mass surrounding as it approached the center would be pulling it away from the center equally? (Sort of the Gravitational Bungee Jump)

The following link gives a good description of what happens within the event horizon of a black hole using the Schwarzschild metric-

Spacetime Geometry Inside a Black Hole

Scroll down to the sub headings The Schwarzschild Metric and Inside the Black Hole
 

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