How to Understand What Black Holes Look Like
Why Hacker News recommends it
Recommended for correctly predicting the features of the real black hole image and clearly explaining the lensing physics behind it.
What it is
Veritasium explains what a black hole should look like, using J.P. Luminet's 1979 work and a cardboard 3D model to show how light bends around it. It was made just as the first black hole image was released.
Recommended by 8 HN commenters across 4 different months, 2019 to 2021.
What Hacker News said
Strong rec turshija · 2019-04 · on “Unveiling the first-ever image of a black hole [video]”
Related video, made by Veritasium yesterday, is one of my favorite videos in a long time. He explained how the prediction of this image was made (before the image got released) and the video is great and fun to watch. [this video]
Recommends JumpCrisscross · 2019-04 · on “Unveiling the first-ever image of a black hole [video]”
Good video that correctly predicted the image and describes why it looks the way it does [1]. TL; DR The dark area is the entire surface of the event horizon, including the side facing away from us, plus some more due to photons missing the event horizon "directly" being drawn in. One side is brighter due to its being Doppler boosted. [1] [this video]
Recommends delecti · 2019-04 · on “Unveiling the first-ever image of a black hole [video]”
If you mean the brightness asymmetry, it's because the accretion disc is spinning. This video predicts pretty well all of the features we expected to find, and it lines up with the actual image. [this video]
Recommends tempestn · 2019-04 · on “Unveiling the first-ever image of a black hole [video]”
The black hole itself is spherical, but the light we're seeing around it isn't projected by the event horizon; rather, it's light from behind/around the black hole that isn't blocked. This video explains in much more detail: [this video]
Recommends kaslai · 2019-07 · on “A Ring of Controversy Around a Black Hole Photo”
Derek explains the physics in a reasonably understandable manner in this video on his Youtube channel: [this video]
Recommends sudhirj · 2019-09 · on “Simulation of what a massive black hole would look like”
There's a clearer explanation of why the disk looks that way and how the gravitational warp makes those light paths [this video]
Recommends sova · 2019-09 · on “Simulation of what a massive black hole would look like”
Veritasium made an excellent youtube video explaining how this effect works (before the image was released!) [this video]
Recommends gus_massa · 2021-08 · on “First image of a black hole: a CNRS researcher had simulated it as early as 1979”
If the black hole is not spinning, it should look the same from every angle. A spinning black hole is deformed (like the spinning Earth.) 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 [this video]