[darkmighty]

The image "inversion" effect you get near the black hole is very intriguing ... you get an infinite series of inversions with increasing compression corresponding to the number of revolutions light took around the BH. So a few photons getting to you might be really old (could be almost as old as the BH itself!), it's a series of windows into the past...

[wyager]

Wow, I hadn't thought of that. I wonder what the "compression" factor is for each orbit around the black hole.

Edit: Actually, I don't think you get any photons that do a full 360 degrees around the black hole that subsequently escape the black hole.

[darkmighty]

If you look at the image of geodesics he shows an example of an almost 360 degree trajectory. Simple continuity arguments allow you to conclude you can have an arbitrary number of rotations, I believe.

I would conjecture the contraction is roughly exponential, there's no obvious contradiction with that but it's way over by knowledge to check it ...

[wyager]

By the time a photon has done a complete rotation, it necessarily has to be on a path that takes it into the black hole (instead of outside of it). So yes, you can have an arbitrary number of rotations, but anything that makes a complete rotation or more will never leave the black hole.

[darkmighty]

It turns out that a photon can describe any real rotation angle around a black hole (I've asked a physicist). The continuity argument I gave is valid: take the critical energy E wherein the photon is attached to the photosphere, then with an adequate E+eps, eps > 0, the photon will describe an according monotonically decreasing angle.

[darkmighty]

Hmm I'm not so sure anymore. I'll have to ask a physicist I guess.