Observing Kerr Singularity: What Would an Observer See?

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Discussion Overview

The discussion revolves around the observational characteristics of a Kerr singularity, particularly what an observer would perceive when near such a singularity. It touches on theoretical implications, optical effects, and the nature of the singularity itself.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the Kerr singularity, being timelike, would appear as a point to an observer, while others argue it would still be perceived as a ring.
  • One participant notes that the timelike nature of the singularity means it should be observed as a point, questioning why it would be different from other point objects.
  • Another participant clarifies that the Kerr singularity is a cylinder in spacetime and that its spatial topology is a ring, which relates to the existence of closed timelike curves (CTCs) in the vicinity.
  • There is a discussion about the optical effects and what an observer might see, with acknowledgment that detailed simulations are necessary for a comprehensive understanding.
  • Participants share resources, including a website with mathematical insights on Kerr metrics, and express enthusiasm about using simulation programs related to Kerr orbits.

Areas of Agreement / Disagreement

Participants express differing views on how the Kerr singularity would be perceived by an observer, with no consensus reached on whether it appears as a point or a ring. The discussion remains unresolved regarding the optical effects and the implications of the singularity's properties.

Contextual Notes

The discussion highlights the complexity of visualizing phenomena near a Kerr singularity and the limitations of current simulations, which predominantly focus on non-rotating black holes.

tzimie
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I know it is very unlikely such thing exists because QM can prevent CTLs

However, what observer would see near such singularity?
As ring is timelike, for an observer it won't be a ring at all, but a point, correct?
That point should be visible (naked) because there are no horizons between an observer and singularity?
 
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tzimie said:
As ring is timelike, for an observer it won't be a ring at all, but a point, correct?

No, it would be a ring. "Timelike" just means it follows a timelike worldline, like an ordinary object. And yes, it will be visible if you're inside the inner horizon.
 
Any point object creates a timelike worldline in block time. Why Kerr Ring should be different? If it is timelike, it should be observed (by an observer close to the ring) as a point. "Ring" just tells us that an observer is inside closed timeline curve...
 
Last edited:
tzimie said:
If it is timelike, it should be observed (by an observer close to the ring) as a point. "Ring" just tells us that an observer is inside closed timeline curve...

The Kerr singularity is a cylinder in space-time. It is a ring in the Boyer-Lindquist spatial coordinates so Peter is correct i.e. only its "spatial topology" is a ring. This has nothing to do with CTCs as the CTCs exist in a neighborhood of the ring singularity, not on it, and has to do with the fact that in this neighborhood the axial Killing field becomes time-like while retaining its closed orbits.
 
Interesting, thank you
So what we would see - optically, and what we would "see" if we try to compensate pure optical effects?
I understand it is quite difficult to answer this question without a detailed simulation, however, all simulations I've seen cover only non rotating BH
 
Thank you!
Exactly what I was looking for!
 
Wow, just downloaded the program, that is a great find, thanks! Having just finished my own Kerr orbit program, it looks like I will be able to drive animations from this using my data files. Fantastic!
 

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