[guscost]

This is a very good answer, thanks for taking the time to write it. I will say that "pretty good" evidence is not consistent with the language we usually see in the media[1] but that's really another issue.

Can't SR only model photons at c because some term disappears with zero mass which prevents infinite energies? Isn't it a whole different question whether GR is still reliable in the analogous case with massive objects?

[1] http://www.phdcomics.com/comics/archive.php?comicid=1174

[lutusp]

> I will say that "pretty good" evidence is not consistent with the language we usually see in the media[1] but that's really another issue.

That's the difference between science and journalism. In journalism, some things are proven true, while others are cast into doubt. In science, some things are proven false, while others are less doubtful than they once were, but never become true. The tl;dr: in science, things can only ever be proven false, never true.

As philosopher David Hume famously put it, "No amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion."

> Can't photons only travel at c because some term disappears with zero mass which prevents infinite energies?

I'm not sure I've successfully decoded your question, but only massless particles can travel at c. This is why, when it was established that solar neutrinos were changing their identities while traveling from the sun to our detectors, that meant they were experiencing time, which meant they had mass. All confirmed in later experiments.

> Isn't it a whole different question whether GR is still reliable at c when massive objects are involved?

From a mathematical standpoint GR is perfectly reliable from v = 0 to v = c, including places where large masses are present. Any velocity past c (or a sufficiently large amount of spacetime curvature) and GR is no longer able to provide reliable predictions. The reason is that the mathematical results include imaginary terms. As has been said by many, the relationship between mathematics and reality is much closer than we once imagined.

[guscost]

So the region within the event horizon is where we see the sufficiently large/infinite curvatures and the imaginary terms and GR can be said to break down? I've heard that from a frame of reference outside the event horizon the time dilates and light would seemingly never get there, hence the whole idea of a black hole.

Mind-boggling stuff, thanks again for writing out these explanations.

[lutusp]

> So the region within the event horizon is where we see the sufficiently large/infinite curvatures and the imaginary terms and GR can be said to break down?

Yes. At the event horizon, general relativity still predicts the outcome. Below it, no more conventional physics.

> I've heard that from a frame of reference outside the event horizon the time dilates and light would seemingly never get there, hence the whole idea of a black hole.

I've read that too, but in fact, because of the energies of accretion disks that are vacuuming up light and matter from the neighborhood, and the fact that some of the photons tend to orbit the horizon endlessly, it's actually a very hot place in most cases.

> ... thanks again for writing out these explanations.

You're most welcome.