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> But saying that it's a robust prediction if particular conditions are satisfied But that's not what they said. They said (or implied) it's a robust predictio

> But saying that it's a robust prediction if particular conditions are satisfied But that's not what they said. They said (or implied) it's a robust prediction of GR for our actual universe. > But we can still use it if we don't have any better model to replace it with, since even if it breaks down near the singularity, that still leaves the whole rest of the model with plenty of usefulness. But I never questioned the usefulness of the whole rest of GR? GR is a beautiful and much more satisfying, consistent and mathematically rigorous theory than e.g. QFT, so only because we know its predictions might not hold near singularities I wouldn't dare throwing out the baby with the bathwater. I merely said we don't really know what's happening with the matter once it's inside the black hole / close to the singularity. And it looks like we agree here.

pdonis 4y ago
> They said (or implied) it's a robust prediction of GR for our actual universe. Who is "they"? The people who published the singularity theorems didn't say that. They only said the theorems are mathematically valid given the assumptions, and they proved that by proving the theorems. They didn't say the assumptions had to be satisfied in our actual universe. In fact, most physicists say the opposite: that the mathematical validity of the singularity theorems shows that at least one of the assumptions they are based on must be violated in our actual universe, since it would be physically unreasonable for there to be singularities in our actual universe. > I merely said we don't really know what's happening with the matter once it's inside the black hole / close to the singularity. In the sense that most physicists believe a singularity is physically unreasonable, yes, I agree. But in the absence of a better model, that doesn't help very much. The nice thing about the hypothesis under discussion here is that it holds out the prospect of a better model, if it can be made to work.

pdonis 4y ago

> They said (or implied) it's a robust prediction of GR for our actual universe. Who is "they"? The people who published the singularity theorems didn't say that. They only said the theorems are mathematically valid given the assumptions, and they proved that by proving the theorems. They didn't say the assumptions had to be satisfied in our actual universe. In fact, most physicists say the opposite: that the mathematical validity of the singularity theorems shows that at least one of the assumptions they are based on must be violated in our actual universe, since it would be physically unreasonable for there to be singularities in our actual universe. > I merely said we don't really know what's happening with the matter once it's inside the black hole / close to the singularity. In the sense that most physicists believe a singularity is physically unreasonable, yes, I agree. But in the absence of a better model, that doesn't help very much. The nice thing about the hypothesis under discussion here is that it holds out the prospect of a better model, if it can be made to work.