Thought Exp: Light Trapped in Gravity Well of Black Hole

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Discussion Overview

The discussion centers around a thought experiment regarding the behavior of light in the gravitational field of a black hole, specifically whether light can become trapped in a stable orbit similar to that of a moon around a planet. Participants explore the feasibility of such an orbit and the factors that might influence its stability.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant questions the possibility of light being trapped in an orbit around a black hole, suggesting that it could be entrapped until changes in the black hole's mass disrupt the orbit.
  • Another participant asserts that such an orbit is not possible.
  • A different viewpoint suggests that even if light could enter such an orbit, it would be extremely unstable due to perturbations from nearby light rays, particles, and gravitational influences from other celestial bodies.
  • One participant hints at considering the scenario from a different perspective, although the specifics of this suggestion are not elaborated upon.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of light being trapped in an orbit around a black hole, with some asserting it is not possible and others discussing the instability of such an orbit if it were to exist. The discussion remains unresolved regarding the feasibility of light orbits.

Contextual Notes

Participants do not delve into the specific conditions or assumptions required for light to enter a stable orbit, nor do they clarify the definitions of stability in this context. The influence of external gravitational forces is mentioned but not quantitatively addressed.

ccrook
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I am not a physicist but I was curious if there was any information on the following thought experiment. Say a beam of light emitted from a far away star passed a black hole at just the right direction that it became entrapped in a sort of orbit like the moon around the earth. Is this possible and would it then be entrapped until the black hole either became more or less massive changing its pull and disrupting uniform circular motion? Or are there other effects that prevent this? Thanks in advance!
 
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ccrook said:
Is this possible
No.
 
I believe that such an orbit, if the light could even get into it, is extremely unstable. The slightest perturbation would disrupt it and since there are always other light rays and particles passing nearby, not to mention the gravitational influences from uncountable stars and galaxies, it wouldn't last.
 
ccrook said:
Say a beam of light emitted from a far away ... would it then be entrapped
Think of the reverse direction
 

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