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Show HN: Physically accurate black hole simulation using your iPhone camera

(apps.apple.com)
313 points yunyu | 4 comments | 19 Nov 24 17:06 UTC | HN request time: 0.001s | source
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lupsasca ◴[19 Nov 24 17:07 UTC] No.42185680[source]▶
Hello! We are Dr. Roman Berens, Prof. Alex Lupsasca, and Trevor Gravely (PhD Candidate) and we are physicists working at Vanderbilt University. We are excited to share Black Hole Vision: https://apps.apple.com/us/app/black-hole-vision/id6737292448.

Black Hole Vision simulates the gravitational lensing effects of a black hole and applies these effects to the video feeds from an iPhone's cameras. The application implements the lensing equations derived from general relativity (see https://arxiv.org/abs/1910.12881 if you are interested in the details) to create a physically accurate effect.

The app can either put a black hole in front of the main camera to show your environment as lensed by a black hole, or it can be used in "selfie" mode with the black hole in front of the front-facing camera to show you a lensed version of yourself.

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20k ◴[19 Nov 24 22:18 UTC] No.42188712[source]▶
As far as I can tell, the black hole's you're generating don't look especially correct in the preview: they should have a circular shadow like this https://i.imgur.com/zeShgrx.jpeg
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lupsasca ◴[20 Nov 24 00:02 UTC] No.42189422[source]▶
What the black hole looks like depends on how you define your field of view. And if the black hole is spinning, then you don't expect a circular shadow at all. But in our app, if you pick the "Static black hole" (the non-rotating, Schwarzschild case) and select the "Full FOV" option, then you will see the circular shadow that you expect.
replies(1): >>42191344 #
1. 20k ◴[20 Nov 24 06:44 UTC] No.42191344[source]▶
The preview shows that you have a static black hole selected

This shape of the shadow is also wrong for kerr though, this is what kerr looks like:

https://i.imgur.com/3cS1fNI.png

replies(2): >>42191692 #>>42191995 #
2. westurner ◴[20 Nov 24 07:59 UTC] No.42191692[source]▶
"static" is "Shwarzchild without rotation"?

Do black holes have hair?

Where is the Hawking radiation in these models? Does it diffuse through the boundary and the outer system?

What about black hole jets?

What about vortices? With Gross-Pitaevskii and SQR Superfluid Quantum Relativity

https://westurner.github.io/hnlog/ Ctrl-F Fedi , Bernoulli, Gross-Pitaevskii:

> "Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/ :

> FWIU: also rejects a hard singularity boundary, describes curl and vorticity in fluids (with Gross-Pitaevskii,), and rejects antimatter.

Actual observations of black holes;

"This image shows the observed image of M87's black hole (left) the simulation obtained with a General Relativistic Magnetohydrodynamics model, blurred to the resolution of the Event Horizon Telescope [...]" https://www.reddit.com/r/space/comments/bd59mp/this_image_sh...

"Stars orbiting the black hole at the heart of the Milky Way" ESO. https://youtube.com/watch?v=TF8THY5spmo&

"Motion of stars around Sagittarius A*" Keck/UCLA. https://youtube.com/shorts/A2jcVusR54E

/? M87a time lapse

/? Sagittarius A time lapse

/? black hole vortex dynamics

replies(1): >>42197295 #
3. ubercow13 ◴[20 Nov 24 08:57 UTC] No.42191995[source]▶
Yes but the preview has 'realistic FOV' selected not 'full'. And the rotating black hole does have the same shadow as your image if you turn the rotation speed up.
4. westurner ◴[20 Nov 24 19:31 UTC] No.42197295[source]▶
"Cosmic Simulation Reveals How Black Holes Grow and Evolve" (2024) https://www.caltech.edu/about/news/cosmic-simulation-reveals...

"FORGE’d in FIRE: Resolving the End of Star Formation and Structure of AGN Accretion Disks from Cosmological Initial Conditions" (2024) https://astro.theoj.org/article/94757-forge-d-in-fire-resolv...

STARFORGE

GIZMO: http://www.tapir.caltech.edu/~phopkins/Site/GIZMO.html .. MPI+OpenMP .. Src: https://github.com/pfhopkins/gizmo-public :

> This is GIZMO: a flexible, multi-method multi-physics code. The code solves the fluid using Lagrangian mesh-free finite-volume Godunov methods (or SPH, or fixed-grid Eulerian methods), and self-gravity with fast hybrid PM-Tree methods and fully-adaptive resolution. Other physics include: magnetic fields (ideal and non-ideal), radiation-hydrodynamics, anisotropic conduction and viscosity, sub-grid turbulent diffusion, radiative cooling, cosmological integration, sink particles, dust-gas mixtures, cosmic rays, degenerate equations of state, galaxy/star/black hole formation and feedback, self-interacting and scalar-field dark matter, on-the-fly structure finding, and more.