- #31
Mike Holland
- 114
- 1
Ok, thanks Peter. I am a follower of the frozen star heresy, and thought you might be coming out of the closet!
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The discussion centers on clarifying the concepts of event horizons and Killing horizons, particularly in relation to future null infinity. It highlights that while event horizons and Killing horizons can be locally indistinguishable, they differ globally, with the event horizon being the last Killing horizon that escapes to future null infinity. Future null infinity is defined as the set of events at the end of a null geodesic as the affine parameter approaches infinity, but this does not include events on the photon sphere, which do not extend to future null infinity due to the metric not being Minkowski there. The conversation also touches on the implications for cosmological models, noting that the conformal compactification concept does not apply to realistic cosmologies, suggesting that true event horizons may not exist in our universe. Understanding these distinctions is crucial for grasping the nature of spacetime in general relativity.