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

This is not a simulation of a black hole, but rather an image filter that emulates one particular effect.

Yes, agreed. We thought it would be fair to call it a "simulation" of what your surroundings would look like if a black hole were within your FOV, but as you say we do not take into account all effects (time delays in particular would require a lot of buffering and we decided this would be impractical to implement, and not that illuminating).

This is still nice when there are so many artistic images of black holes that do not take such care to use known physics to create an accurate image. Well done all. Looking forward to seeing what BHEX sees.

Glad to hear you're excited about BHEX---we are too!

If you want to read more about what it's going to do, I wrote a blog post about it on the mission website: https://www.blackholeexplorer.org/bhex-blog/lupsasca-stateme...

You're right that the time delays and redshifting wouldn't add much to a toy app, but some of us are here for the physics.

Honestly it's not so far-fetched (to me) that in a few years someone will have GRRMHD simulations running in real time on a portable device.

Are you familiar with A Slower Speed of Light? It's a game which has some nice special-relativistic effects.

http://gamelab.mit.edu/games/a-slower-speed-of-light/

Yes, such a great game---it's a fantastic visualization of special relativity and also fun to play!

I think we're still a ways off from real time GRMHD sims, but CK Chan from UArizona had a working VR simulation (on the Oculus iirc, but now deprecated) that allowed you to explore a pre-existing GRMHD simulation in real time and in 3D. I think he might be working on a new version of this.

That's awesome. It's extra crucial to have engaging outreach when your research is so far from application. There's so much scope for wowing people with astro and if you can enrich our culture and justify funding at the same time that's a win-win.

(Just for clarity the second R in GRRMHD is for radiation. I know it's typical to just push some photons through the GRMHD results to produce renders, bit since I'm dreaming let's treat the radiation self-consistently.)

Read all of it, only question I have is... napkin math, how much more resolution over EHT alone?

Hahaha, I half-expected a plasma physicist to complain that GRRMHD is not self-consistent and we need to include non-ideal fluid effects :D

About ~5x improvement. Recall that the resolution of an interferometric array is set by the distance between telescopes measured in units of the observation wavelength. BHEX will get a ~3x resolution improvement from the increased distance between the space satellite and our ground telescopes (for the EHT, the max telescope separation is limited by the diameter of the Earth) and another ~50% from the increased frequency of observations (going up from 230 to 320 GHz).

5x is actually a lot: we'll be able to resolve the "photon ring" of orbiting light around M87* and Sgr A* (the two black holes previously imaged by EHT at lower resolution) and likely see the "shadows" of another 6-8 black holes, with the possibility of estimating the mass of another ~20-30 sources.

I've been able to port NR to GPU's which with sufficiently powerful hardware can run simulations at about ~30fps with raytracing, to simulate binary black hole collisions. You need something around a top end consumer gpu at the moment. Phone hardware needs a while to catch up, there's an absolute minimum memory requirement of ~8gb vram, and you need a lot more bandwidth than they currently support

Touché. While we're at it there are almost certainly some non-negligible QED processes. I guess there wouldn't be jobs for physicists if this stuff was straightforward.

That's absolutely awesome, thank you.

Awesome! Is it published anywhere? All the stuff I'm familiar with is aimed at old-school clusters.