Black holes with nothing left to ingest.

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Discussion Overview

The discussion centers around the nature of black holes, particularly focusing on the concept of event horizons, their behavior when consuming matter, and the implications of their existence. Participants explore theoretical aspects, gravitational effects, and the limitations of current physics in fully describing black holes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that black holes "suck everything in" due to their gravitational forces, similar to how Earth exerts gravity, but clarify that this is not an active process of sucking.
  • It is noted that black holes have event horizons that exist independently of whether they are actively consuming material.
  • One participant mentions that the event horizon expands as a black hole captures more matter, referencing a formula for its radius.
  • Concerns are raised about the inability to prove certain aspects of black holes, with some arguing that the physics of black holes does not align well with current understanding, especially near the singularity.
  • Another participant asserts that while classical theory predicts a singularity, quantum gravity suggests different possibilities, though the specifics remain uncertain.
  • There is a contention regarding the nature of experiences inside a black hole, with one participant claiming that nothing exceptional happens except that all paths lead to the singularity, while another suggests that the physics behave differently inside the event horizon.
  • Participants discuss the lack of photographic evidence for black holes, emphasizing that they are detected through gravitational interactions rather than direct observation.

Areas of Agreement / Disagreement

Participants express differing views on the nature of black holes, particularly regarding the event horizon and the implications of being inside it. There is no consensus on the extent to which current physics can describe black holes or the validity of certain claims about their behavior.

Contextual Notes

Limitations include the unresolved nature of physics near the singularity and the dependence on theoretical models to describe black holes. The discussion reflects ongoing uncertainties and assumptions about the behavior of black holes and their event horizons.

Nibles
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If a black hole sucks everything into it that is near it, but at the same time has an event horizon, then everything between the event horizon and the black hole will get sucked it, but then there would be nothing else to suck in once it's all gone, unless the event horizon expands. Is this correct, or is it not? Thoughts?
 
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1) All black holes have event horizons.

2) A black hole can certainly "suck everything in" around it. The problem you might be having is in your phrase "suck things in." Black holes don't really do that! Black holes exert gravitational forces on bodies near them, exactly as the Earth does to you, only stronger. You can orbit a black hole in your starship just as you can orbit the Earth in a space shuttle. Black holes act gravitationally just like any other massive body.

3) As a black hole captures matter and grows more massive, its event horizon expands. The radius of the event horizon is given by:

[tex]r_s = \frac{2 G M}{c^2}[/tex]

- Warren
 
Welcome to Physics Forums, Nibles! :smile:

The event horizon is simply the distance around the black hole singularity at which nothing can escape. The black hole singularity and event horizon exist whether or not the black hole is actively consuming nearby material. Some current black holes are active (consuming stuff) others are not...just adrift in space orbiting the galactic center like any other star. Of course, they can become active again if something crosses their path.
 
black holes are weird We can't prove anything about the black holes, because they just don't work with our physics. once u enter a black hole, the speed of light will be different, etc. We can only assume that there is an event horizon, because we have no proof (apart from very distant photos) that the horizon is there or doesn't exist
 
Originally posted by chemical
We can't prove anything about the black holes, because they just don't work with our physics.

The physics work just fine at a good distance from the singularity. The closer to the singularity, the weirder the physics. The singularity itself cannot be accurately described by modern physics.

We can only assume that there is an event horizon, because we have no proof (apart from very distant photos) that the horizon is there or doesn't exist

Based on the math, it should exist. (the EH is not a physical thing...it's merely a distance from the singularity)
 
Originally posted by chemical
We can't prove anything about the black holes, because they just don't work with our physics.
Well, you can't really prove anything in science, so that's not a big deal. Black holes actually work just fine with our physics all the way down to their heart. Classical theory predicts a spacetime singularity, while quantum gravity predicts something quite different (though no one is exactly sure what yet). In any case, the only part of the black hole we don't fully understand is that part within a Planck length (10^-43 m) of its center.
once u enter a black hole, the speed of light will be different, etc.
False. Nothing exceptional happens inside a black hole's event horizon (which is, I asssume, what you mean by being "inside" one), except that all worldlines terminate at the singularity. Once you're inside the event horizon, you can zoom around in your spaceship all you want, and everything will seem normal -- you just can't ever get back out of the event horizon. Once you run out of fuel, though, you're lunch.
We can only assume that there is an event horizon, because we have no proof (apart from very distant photos) that the horizon is there or doesn't exist
We have no photographic evidence of any sort of black holes, since they are not detected photographically. They are detected via their gravitational interaction with nearby luminous objects.

- Warren
 

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