Time Dilation & Visual Observation of Black Holes

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Discussion Overview

The discussion revolves around the effects of time dilation and visual observation of objects, particularly stars, in the vicinity of black holes. Participants explore the implications of gravitational time dilation on the perceived motion of stars orbiting supermassive black holes, as well as the relevance of time dilation in calculations related to stars at varying distances from such black holes.

Discussion Character

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

Main Points Raised

  • One participant suggests that when observing a star orbiting a supermassive black hole, it might appear to slow down due to time dilation effects as it approaches the event horizon.
  • Another participant notes that there are no stable orbits within a certain radius of the black hole and argues that gravitational time dilation cannot counteract the increasing orbital speed at those distances.
  • A participant questions whether time dilation should be considered in calculations for stars orbiting the black hole at the center of the Milky Way, implying uncertainty about the significance of distance in this context.
  • Another participant responds that time dilation is not a significant factor for stars at the distances observed in the Milky Way, suggesting that they are far enough away.

Areas of Agreement / Disagreement

Participants express differing views on the effects of time dilation on the perception of stars near black holes, particularly regarding whether it leads to an apparent slowing down of motion. There is also disagreement about the relevance of time dilation for stars orbiting the Milky Way's central black hole, with some asserting it can be ignored while others question this assumption.

Contextual Notes

Participants reference specific radii related to stable and unstable orbits around black holes, indicating a dependence on these definitions. The discussion also highlights the complexity of gravitational effects and observational perspectives, which may not be fully resolved.

EskWIRED
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I'm under the impression that one sees clocks slow down when watching distant objects approaching strong sources of gravity, such black holes. And that objects in an elliptical orbit travel faster when they are near their attractor.

I can't quite figure out how these two phenomenon work together when an such an object travels close to a black hole.

If one were to watch a star orbiting a supermassive black hole, might it appear to slow down, rather than speed up at its closes approach, given sufficient time dilation close to the event horizon?
 
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EskWIRED said:
If one were to watch a star orbiting a supermassive black hole, might it appear to slow down, rather than speed up at its closes approach, given sufficient time dilation close to the event horizon?

There are no stable orbits inside a radius of three times the horizon radius, and no free-fall orbits at all, even unstable ones, inside one and a half times the horizon radius. Even the latter radius is not close enough to the horizon for gravitational time dilation to counteract increasing orbital speed.
 
Thanks.

Does time dilation need to be taken into account when observing or making calculations concerning stars orbiting the black hole at the center of the Milky Way? Or are they far enough away at all times that time dilation can be ignored?
 
EskWIRED said:
Does time dilation need to be taken into account when observing or making calculations concerning stars orbiting the black hole at the center of the Milky Way?

AFAIK, no. None of them are close enough for it to be a significant factor.
 

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