Understanding Light from Black Holes

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Discussion Overview

The discussion revolves around the phenomenon of light around black holes, specifically addressing the visual representation of light circles seen in simulations and images of black holes. Participants explore concepts related to gravitational lensing, accretion discs, and the complexities of observing light in such extreme gravitational fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how light can be seen in circular paths around a black hole, questioning the necessity of being on the edge of the circle to observe it.
  • Another participant requests specific references to the simulations and images mentioned, indicating a need for clarity on the sources being discussed.
  • A participant explains that the light observed comes from an accretion disc, where matter spirals into the black hole and emits light that is bent by the black hole's gravity, allowing it to be seen from various angles.
  • Gravitational lensing is suggested as a key concept to understand how light is perceived around black holes.
  • There is a repeated request for specific references to simulations and images of black holes, highlighting a potential lack of consensus on what is being referred to in the discussion.
  • One participant notes that there is only one widely recognized image of a real black hole, while others mention multiple versions available online.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific simulations and images being referenced, leading to multiple competing views regarding the sources of information. The discussion remains unresolved regarding the clarity of these references and the understanding of light behavior around black holes.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the visibility of light around black holes and the complexity of the phenomena involved, which are not fully explored or defined by participants.

kelly0303
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Hello! I am a bit confused about the circles of light around a black hole, that were present both in simulations and in that image of a real black hole. I understand that the gravitational field is so strong around the black hole that the light is forced to move in a circular path around (from our point of view) around the black hole. But i am not sure how can we see that. If the light moves in a circle, doesn't it mean that you must be on the edge of the circle to see it? What I mean is, if I stay at a distance from the circle, in order to see it, the light should come towards me, but that would mean that it doesn't move in a circle anymore. So what do we exactly see there? Thank you!
 
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kelly0303 said:
I am a bit confused about the circles of light around a black hole, that were present both in simulations and in that image of a real black hole.

What simulations and what image? Please give specific references.
 
Light that is passing by the black hole farther out than the "light that circles around a black hole" is what you see.
Gravitational lensing is what you need to research.
 
The light is coming from an accretion disc, matter spiralling down into the black hole and heating itself by friction. We're looking at it at an angle, though, and the gravity of the black hole is strong enough so that light coming from the far side of the accretion disc gets bent around the black hole and reaches us. So you see a ring around the hole because you see light that's gone "over" the hole - loosely speaking, a bit like a ball thrown over a wall.

The exact structure of what you see is rather complex and requires computer number crunching, but that's the gist of it.
 
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PeterDonis said:
What simulations and what image? Please give specific references.
Any simulation of a black hole and I am pretty sure there is only one image made of a real black hole.
 
256bits said:
Light that is passing by the black hole farther out than the "light that circles around a black hole" is what you see.
Gravitational lensing is what you need to research.
Thank you so much!
 
kelly0303 said:
Any simulation of a black hole

Have you actually looked at any? If so, please give links.

kelly0303 said:
I am pretty sure there is only one image made of a real black hole.

There is one that made the news recently, yes. But there are lots of versions of the image online. Which particular one did you look at? Please give a link.
 

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