Do Closed Timelike Curves Exist?

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Discussion Overview

The discussion revolves around the existence of closed timelike curves (CTCs) in the context of general relativity and black hole physics. Participants explore theoretical frameworks, metrics that allow for CTCs, and the implications of such structures on our understanding of spacetime and time travel.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that while CTCs can be derived from certain metrics in general relativity, such as the Godel metric and traversable wormholes, there is no empirical evidence supporting their existence in reality.
  • One participant discusses the Kerr metric, which describes a rotating black hole that theoretically contains regions with CTCs, particularly near the ring singularity, but questions the stability of these regions against perturbations.
  • Concerns are raised about the implications of infalling observers in a Kerr black hole, including the possibility of seeing the entire future history of the universe in a finite time, which raises questions about the stability of such black holes.
  • Another participant mentions the concept of "geodesic completeness," suggesting that regions inside black holes might connect to other black holes or universes, although this remains speculative.
  • There is a discussion about the potential for "timelike wormholes" to act as gateways to different regions of spacetime, but the practicality of such travel is questioned due to issues like infinite blueshift and radiation exposure.
  • Some participants express differing views on the applicability of theoretical calculations regarding CTCs and black hole stability, with one participant remaining optimistic about the physical reasonableness of such journeys despite challenges presented by existing theories.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the existence or stability of CTCs, with multiple competing views and uncertainties remaining throughout the discussion.

Contextual Notes

Limitations include the dependence on idealized models of black holes and the unresolved nature of certain mathematical aspects related to the stability of CTCs and the behavior of spacetime in extreme conditions.

  • #31
But most think quantum gravity will prevent closed timelike loops?
 
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  • #32
JesseM said:
"Shallow interior" here just means the region between the outer horizon and the inner horizon, and "deep interior" just means inside the inner horizon. So whoever wrote this is just saying that the region inside the inner horizon is objectionable because it contains CTCs, and a lot of physicists think that CTCs are a sign that something is going wrong with the theory (though this is just speculation, there is no proof that CTCs cannot exist in the real world).
what is wrong general relativity or the metric it self?
 

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