Does Singularity Really exist?

Question

I want to know if the singularity really exists. Because if we consider the mathematical singularity and Hawking radiation, doesn’t the radiation prevent the black hole from actually forming a singularity? Like, doesn’t it take infinite time to collapse into a singularity, but the lifespan of a black hole is very long—not infinite? So to collapse into a singularity, it would need infinite time, right? Can someone argue against this?

Answer 1

Somewhat disappointing answer: We don't know. Even Roy Kerr, famous for his groundbreaking research about black holes, argues that they don't. But that is all just mathematics. We cannot even in principle measure what is behind the event horizon, so we can't know for sure if there is a singularity present. And I'm not even getting into quantum gravity now, which is expected to play a major role in resolving at least part of the question.

Answer 2

It should be noted that there exist plenty of models of black holes which, aside from identical to any spherically-symmetric static metric on the outside, contain no singularities on the insides. For example, the gravastar model (see this paper) and Oppenheimer-Snyder models (old paper, can't find a digital copy at this moment) have nontrivial interiors which contain no pathologies as the Schwarzschild metric does.

Regardless, it is not possible in any way, shape, or form to extract information from behind an event horizon, since this would in some sense constitute time travel. So whether or not they exist is not really a meaningful question, as it turns out. I'm sure something quantum-gravitational happens at the center of a black hole.

Answer 3

We don't know and actually we can't know because GR and quantum mechanics are not compatible with each other. So even if we could solve a set of non-linear differential equations to obtain an answer, we can't renormalize infinite number of attributes.