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I recently watched a Kurzgesagt video about destroying black holes. In the video, they mentioned that you can (theoretically) "overspin" a black hole to remove its event horizon, thereby creating a naked singularity. Now the way I think this works is that in an overspun black hole, the ergosphere makes you move so fast you always miss the event horizon. This would effectively allow light to "reflect" off the now-nonexistent event horizon. Wouldn't that mean that the black hole either becomes a white color or a perfect mirror? If it does, then we can't see the singularity and the cosmic censorship hypothesis holds. I admit this is based on my own understanding, so there's probably a flaw in my reasoning somewhere here.

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It has been proven (by Sorce and Wald) that overspinning a black hole is actually impossible. So the question what happens if you overspin a black hole is asking for a counterfactual.

It is not actually clear what the end state of an overspun black hole would be. The obvious candidate would be the Kerr solution with $a>GM/c^2$. This is a vacuum solution to the Einstein equation describing a naked ring singularity, and also features closed timelike curves. However, unlike the black hole case there are no theorems that this has to be the stationary end state.

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  • $\begingroup$ Can't you just drop spinning matter exactly at the poles to overspin it? $\endgroup$
    – Seggan
    Sep 15, 2023 at 18:08
  • $\begingroup$ @Seggan Nope, spin- spin interactions will prevent that. $\endgroup$
    – TimRias
    Sep 15, 2023 at 20:37

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