First image of a black hole: a CNRS researcher had simulated it as early as 1979
cnrs.fr
cnrs.fr
From Luminets personal recollections on black hole imaging: https://arxiv.org/pdf/1902.11196.pdf
"The first step was to integrate the equations of light ray trajectories in Schwarzschild space-time and draw the isoradial curves (i.e. at constant radial distance from the black hole) of a thin disk around the black hole, as they would be seen by an observer above the disk's plane" ....
"The final black and white "photographic" image was obtained from this pattern. Lacking of an appropriate drawing software, I had to create it by hand. Using numerical data from the computer, I drew directly on negative paper with pen and Indian ink,placing dots more densely where the simulation showed more light (a few thousands dots for the full plate). Next, I took the negative of my negative to get the positive, the black points becoming white and the white background becoming black. The result converged into the pleasantly organic, asymmetrical form reproduced in Figure 8, both visually engaging and scientifically revealing."
I am feeling grateful to have started by scientific/engineering computing career one year later than the authors paper in 1980, and as it happens the first year without punched cards at my Univ.
https://www.wired.com/2014/10/astrophysics-interstellar-blac...
One EHT speaker I asked said an important advance was scaling up the VBLI procedure a thousand times from hundreds of megahertz to hundreds of gigahertz to achieve resolutions needed to image the three largest super massive black holes. This involves huge improvements across the entire system from the antenna receiver, clock resolution and petabyte data handling.
I know if you're too close, everything gets distorted, but I would have thought they look the same from any direction or angle, never managed to grasp the concept.
Maybe there is some 3d sim to explain this?
Anyway, we are not seeing the black hole (because it looks just like a black circle in front of a black background). The interesting part of the image is a disk of material spinning around it. There is a nice 3d cardboard simulation and clear explanation in a video by Veritasium https://www.youtube.com/watch?v=zUyH3XhpLTo
If the black hole is spinning, it has poles. We expect all black holes to be spinning. This is a subtle change in the shadow itself, but...
And if the accretion disk and black hole have misaligned poles, there should be a huge warp in the disk close to the black hole as the black hole frame-drags the accretion disk.
What happens at the singularity in a rotating black hole depends on your quantum theory of gravity. Some theories have the singularity as a "ring" instead of a point. I believe loop quantum gravity has a "planck star" in the center of a black hole.
Macroscopically, rotating black holes can be thought of as rotating the space around the event horizon. So the spacetime curvature doesn't just pull you directly to the center, there's an angular aspect as well.