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- Hacker News
- Very neat! Love seeing immediately grok'able simulations like this that you can just browse to.
There are a few neat black hole shaders[1][2] on Shadertoy as well.
by picafrost - Them: you can’t see what’s on the inside of a black hole
Me: zooms in
by ninjahawk1 - From a certain angle it looks like an eyeball https://imgur.com/a/Dam3XT0by nomilk
- Very cool, and very mind bending. Very faithful to the Event Horizon Telescope rendering. A decade ago I got really into black holes for like a few months, and I read Kip Thorne's book called "The Science of Interstellar", talking all about black hole simulations. Have you read it? I wonder how the simulation tech has evolved, as 10 years is a lot. I do wonder if you do like, size estimates of a black hole in my room. Suppose I have a black hole in my room, I'd be curious to know what the mass of that is, like a fun fact, tidbit somewhere.by aizk
- > I do wonder if you do like, size estimates of a black hole in my room. Suppose I have a black hole in my room, I'd be curious to know what the mass of that is, like a fun fact, tidbit somewhere.
Forgot to answer this first!
Basically, ~1 cm radius black hole has the mass of the Earth – really, Earth would need to get this small to become a black hole. I've made a very simple demo for a kids lecture I gave recently, https://plav.in/outreach_demos/squeeze-earth-v2.html. Also see https://xkcd.com/1680/ of course :)
by aplavin - The technology has come a long way indeed! The first simulations of how a black hole would look like are from 1979, by Jean-Pierre Luminet – take some time to find and look at them, it's super impressive what they achieved using that era tech! Now, we can get much higher-resolution ones in real time on any smartphone.
I work in the Event Horizon Telescope, studying jets accelerated by black holes, and immediate black hole surroundings as well. I do ray tracing / radiative transfer simulations, and this app is an adaptation of those simulations – with the primary focus on being physically accurate under reasonable assumptions.
And totally, I enjoyed listening to Kip Thorne's lectures and talking to him, he gives them in a very approachable style while remaining honest!
by aplavin - This is lovely, great to see science like this! Many thanks to you and your colleagues!by toddm
- The distortion effects dont work for me on pixel 8 when using AR mode
I just get a flat floating image of a black hole. Am i holding it wrong?
by arianvanp - Same on pixel 10by viciousvoxel
- Yes, as said in the text, unfortunately this is a limitation of browser APIs. You either get AR and no access to the camera feed (this is the AR mode here, black hole floating in your room, simply overlaid on top of the camera feed) or get access to the camera feeds but no AR (this is the camera mode). I didn't find a way around it...by aplavin
- > unfortunately, WebXR restrictions make AR passthrough and the camera feed mutually exclusive
It looks like Chromium-based browsers might be doable?[1][2]
Meta: About a decade ago, I rolled my own WebXR-like stack with passthrough, and played with an XR Powers of Ten zoomer. Here we are years later, and it's apparently still not something which might be deployed. In some sense, we are progressing so sloooowly.
[1] https://caniuse.com/wf-webxr-camera [2] https://immersive-web.github.io/raw-camera-access/
by mncharity - Hmm, interesting! I saw that it's a draft, and didn't investigate further. Maybe it does work indeed on some browsers.
Generally, the compatibility story turned out more fragmented than I expected. Eg, on my phone, Chrome can do AR – but cannot do two camera feeds at once; while Firefox is the exact opposite – no AR but can do both cameras at once, so that you see both front and rear lensed around the black hole properly (in the camera mode).
by aplavin - Please correct me if I'm wrong, but it feels like the leading edge of the accretion disk (coming towards the viewer) should be significantly brighter than it is shown here, and the trailing edge (going away from) should be significantly dimmer?
Or could the brightness shown be a result of it being Kerr vs Schwarzschild?
by csmoak - One side of the accretion disk is indeed brighter than the other – in the default view in the app, the bottom part is brighter. The effect appears quite clearly visible to me, although the exact contrast depends on the colorscale mapping. Here, I tried to find a colorscale that works well for both the disk and the jet, which naturally means the leading/trailing edge contrast can be less than in the linear mapping. Hope it explains the visual effect!
Kerr vs Schwarzschild (static vs rotating black holes) is a much smaller effect visually – that's why it is so hard for us to measure black hole spins (= how fast they are rotating) observationally, even with the Event Horizon Telescope.
by aplavin - Yeah the doppler in this picture is all wrong unfortunately, the underlying equation used isn't right here (they mixed up spectral radiance and radiant flux). The rendering is also done without taking into account sRGB, and its run through a function that messes with the brightness - so the brightness is really incorrect. Plus all the colours are wrong (it uses an amhot colouring function, they aren't based on anything), and the extinction and emissivity isn't correct either, and the camera basis is also set up wrong so it also has the wrong perspective too. Other than that its all goodby 20k
- I remember like 10 years ago when Occulus first came out there was that space simulation demo where you could go around the solar system in VR. You could also "fast travel" by zooming in towards a planet, moon, blackhole.
Yeah, that was the day I learned I have a deep, crippling phobia of large objects. And Melanoheliophobia, which is fear of black holes. The only other time I've felt that way was snorkeling once near a giant 3 story tall bait ball of swirling fish, which was so disorienting and panic inducing that I vomited.
by dluan - Thanks for sharing – as someone who studies black hole environments daily, I didn't even think of such a phobia existing!
I wonder if some tricks, adjustments are feasible, to minimize the effects of these phobias? I see these visualizations as a pathway to make understanding such a complicated, unintuitive object more accessible – and would be great to make it even more accessible, if it makes sense... Happy to chat more, brainstorm some solutions.
by aplavin - For anyone that experiences the same, how do you feel about this picture? https://antichamber.fandom.com/wiki/Eye_Wall?file=Eye.png
It has always scared me and I believe it's for the exact same reason. It's possible it invokes no feelings on you if you haven't seen it in context (in the game it's from) so I'd like to test this
by efilife - > Melanoheliophobia, which is fear of black holes
Thank you for mentioning this. I am an avid space nerd. One day I decided to try Space Engine, and one of the first thing I did was get warped to a black hole. Seeing a literal hole in space time appear in front of my screen was one of the most terrifying things I've experienced. I Alt-F4'd, and never opened that application again.
It's like every single atom, nay, every single subatomic carrier of information in my body was telling me to stay the hell away from that.
by sph - https://en.wiktionary.org/wiki/melanoheliophobia
Okay, so this appears to be a neologism that may not be found outside of science fiction dialogue. But I can appreciate the humorous derivation here.
Wiktionary defines this as an "irrational fear" which is in-line with other irrational fears known as phobia. So, is it possible to have a rational or healthy fear of black holes? Is it rational to be unafraid of them?
I am unafraid of personally meeting the Flying Spaghetti Monster whilst not wearing a colander on my head, and I am not irrationally afraid that Azeroth will be invaded by Kardashians. I am not afraid that a dragon will bite my head off.
It seems rationally to be respectfully "fearful" of the capabilities and awesome astrophysical properties of black holes, but it would be irrational to be afraid that I could fall into one, or be personally harmed in any way by one. If someone begins "seeing" black holes at the end of their suburban cul-de-sac, then probably get some professional help.
- > Melanoheliophobia
Tangential, but this being a nearly word-for-word translation of “black hole fear” made me realize how odd it is that we insist on latinizing these things.
by GavinMcG - To be fair, is there anyone alive who wouldn't be afraid of a black hole? It's a celestial body so gargantuan its gravity bends the light passing around it like a lens. Anyone who gets too close to one will literally never be seen again, ever.
- If somebody feels no fear while zooming towards a black hole, their brain has some strange wires crossed.
Strongly recommend Outer Wilds. Falling into the black hole the first time was one of my most scared moments in gaming. I was totally panicking lol
by chamomeal - I did a 'swim with sharks' thing at Sea World (or whatever the Queensland equivalent is) with a few human-safe species of sharks, a few rays, and a selection of other fish. One of the other fish was, as far as I recall, some kind of giant grouper which, as far as my memory tells me, was huge, unmoving, and had it's mouth open the whole time, and it's mouth hole would have been big enough to put my entire head inside (this is according to my memory anyway).
I was nervous beforehand, but once I was in (and had accepted the inevitability of my own death) it was surprisingly calm / calming floating around and having these frickin' aquatic alien species just going about their dailies around me. I went close to the massive grouper just to get the scale right (not that I can really remember, it was 26 years ago). I even looked through the perspex so I could see the non-human-safe sharks in the tank next door.
After the (awesome) experience, I went and looked at the grouper from the outside (one of those underground big perspex viewing rooms) and I was back to being awed / scared by its size, and somewhat refusing to believe that I'd been in there with it. The memory of it is scarier to me than what I remember feeling when actually doing it. It's weird.
by BLKNSLVR - I tried following the instructions and use it for education/outreach, and somehow I got educated by the past while receiving outreach from the future.by hmokiguess
- If anyone's interested in the accuracy, this is very 'visualisation grade' software. Its a bit of a pet peeve of mine that people present these sims as being very physically accurate, when they contain major inaccuracies, some of which are very obvious and/or deliberate. This one has some serious physical limitations
I wouldn't mind at all if it didn't say that this was a *physically accurate* black hole specifically, but this now falls under misleading science communication in a way that often gets hand waved away as if it doesn't matter, so we've got to clear some things up!
1. The accretion disk shouldn't be red, people just expect it because it looks cool. Black hole accretion disks are near universally hot enough to be blue. Interstellar did this too, and tried to handwave it away very unconvincingly
2. This is a non/low (?) spin black hole, which isn't super duper realistic
3. It ignores the position of the camera (which affects the lorentz shifting)
4. The doppler shifting isn't terribly accurate
5. It doesn't model the accretion disk temperature distribution or colour with any kind of accuracy. Usually you model accretion disks as a blackbody radiator, shift it by the doppler, and to display this convolve this against the human eye response (LMS), go to XYZ, then RGB, do a physical tonemapping step, before an sRGB conversion. This instead does none of that - no step of this is done with any physical accuracy. Its not even illustratively correct as we'll get into
6. The actual radiative transfer is very simplified compared to what you'd use for realsies, and isn't based on any real numbers, with very simplified equations. The opacity and emissivity of the disk is arbitrary, as is the size, and it does not correctly incorporate brightness or extinction, eg here https://github.com/aplavin/blackhole.plav.in/blob/2f004bfeca... is super simplified
7. The wrong equation is used for the doppler calculation. They use the I^3 variant, whereas the data you get out of a disk sample is *radiant flux* which is actually F_obs = F_emit / (z+1)^4. This is a very common mistake in image processing, which means that the doppler shift and observer brightness isn't correct. Surface brightness over here https://github.com/aplavin/blackhole.plav.in/blob/2f004bfeca... is *not* a spectral radiance but instead a radiant flux
Stuff like the brightness -> colouring conversion is particularly inaccurate. Eg if you check out the source:
https://github.com/aplavin/blackhole.plav.in/blob/2f004bfeca...
It maps the pseudo brightness completely arbitrarily to colour. The resulting colour/brightness here then doesn't correspond to anything remotely physical. It also performs a *linear* mapping of a linear quantity (brightness) to sRGB (which is a nonlinear process!!), which means that it doesn't even retain any of the underlying physical characteristics of the brightness simulation, which itself is quite inaccurate. Its vibes all the way down
This is all fine if you're doing visualisation, but this isn't an accurate simulation. I wish this was just called a visualisation of a black hole, but its being communicated as if this is super hard science with credentials and all
by 20k - but why was the picture taken of black hole have accretion disk yellow?by KinetiNode
- I agree. I was able to position the camera so that the entire black hole effect was negated and we were back to having a star. All I needed to do was turn the camera just right.by reactordev
- You know, I am interested in the accuracy.
I like what OP has created, but out of curiosity, where might I find the most physically-accurate, browser-based black hole simulation?
by wanda - https://www.youtube.com/watch?v=eQZ3LAexNxE
Love, Death & Robots: Black hole used red for the disc, too.
by imp0cat