Falling into a black hole
Why Physics Stack Exchange recommends it
Physics Stack Exchange answerers link it as a realistic, physically computed visualization when someone asks what an infalling observer would see or how such images are generated.
Recommended by 2 people across 3 different months, 2018 to 2021.
What it is
A short, roughly five-minute simulation of what an observer sees while free-falling into a non-rotating (Schwarzschild) black hole, shown as a fish-eye panorama of the stars with Orion and Sirius in view. It was made by physicist Ben Crowell using his own open-source ray-tracing code, with brief explanatory text and music.
What people said
Recommends user4552 · 2018-08 · Physics Stack Exchange · on “What will the universe look like for anyone falling into a black hole?”
There is a nice paper on this topic by Riazuelo, [LINK] . The following are three simulated images I produced using some open-source software [LINK] I wrote. I also produced a video [this video] showing the motion, with a little bit of didactic text and some spooky space music. My images seem to match up pretty well with Riazuelo's simulations. All of these are the simulated views of an observer who free-falls into a Schwarzschild black hole, starting from rest at infinity. In these simulated wide-angle panoramas, the black hole is to the left, and to the right you can see the constellation Orion. The bluish star Rigel (Orion's "foot") is directly above us, but we can still see it in the same fra
Recommends user4552 · 2019-03 · Physics Stack Exchange · on “Can anyone tell me how can draw shadow of black hole like in presented in Intersteller movie? Is there any code for it in Mathematica or in Python?”
I wrote some open-source Python code for that purpose: [LINK] . I believe the code used in the actual movie is not open source. There is a very complete discussion of the techniques by Riazuelo: [LINK] . I don't think Riazuelo's source code is available. Mine only currently handles Schwarzschild black holes, i.e., not rotating ones like in the movie. My video simulation of falling into a black hole: [this video] This lecture [LINK] by Riazuelo (in French) has some nice videos. A related question, with an answer from me that includes some still images and discussion of the physics: What will the universe look like for anyone falling into a black hole? [LINK] I hadn't known until seeing Void's comm
Recommends user286570 · 2021-01 · Physics Stack Exchange · on “Does someone falling into a black hole see the outside universe moving faster?”
It depends on what angle they're looking at, their state of motion, and the type of black hole. No, this is not controversial among people who have actually studied the problem carefully and understand relativity. The effect you're talking about is identical to the Doppler shift. If you see light red-shifted from a certain direction in the sky, you are seeing signals from that direction slowed down. Blue shifts mean you're seeing signals sped up. Here is a realistic simulation I did of an observer free-falling into a non-rotating black hole: [this video] This observer is falling from rest, starting from far away. What you'll see is that the stars observed in the outward(=backward) direction are r
Cites user4552 · 2019-03 · Physics Stack Exchange · on “Location of event horizon in moving black hole”
The event horizon is by definition a set of points in spacetime that is independent of the observer. Therefore its location is independent of the state of motion of the black hole and the observer relative to each other. We could ask whether the moving observer thinks the event horizon is spherical. This is not a question that is meaningful in general relativity, unless you specify what kind of observations are involved. When we define spherical symmetry in GR, we take pains to do it in a way that is independent of coordinates or observers. You might think that you could take the intersection of the event horizon with a surface of simultaneity for a particular observer, but GR doesn't define
Cites user282122 · 2020-12 · Physics Stack Exchange · on “Computing in Kruskal coordinates”
There are simple closed-form solutions for a particle that falls into a Schwarzschild black hole, starting from rest at a large distance. See [LINK] , below the text "When $E = m c^2$ and $h = 0$ , we can solve for $t$ and $τ$ explicitly." The proper time $\tau$ is what you want here. The Schwarzschild time coordinate $t$ is not a particularly meaningful thing to refer to inside the horizon (it isn't timelike). For the proper time, the result (omitting a constant of integration) is $\tau=-(2/3)(R/c)(r/R)^{3/2}$ , where $R$ is the Schwarzschild radius. So for example, the time it takes to go from $5R$ to $R/4$ on such a trajectory (already in motion at $5R$ ) is $7.4R/c$ . Here's a simulation