Show HN: Physically accurate black hole you can put in your room

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aaplavin 4 days ago 23 commentsRead Article on blackhole.plav.in

RU version is available. Content is displayed in original English for accuracy.

We have a black hole at home — with actual relativistic physics, live in your browser.

I'm Sasha (Alexander) Plavin, an astrophysicist at Harvard's Black Hole Initiative studying quasars and black hole environments. I work with raytracing/radiative transfer simulations professionally, and wanted to make one anyone can play with — so I built this app.

Put the black hole onto your screen (any browser), or directly into your room with AR or VR (requires WebXR, for example Chrome on Android, or any VR headset). When looking around, pay attention to unintuitive relativistic effects: rays bending around the black hole, and special relativistic "Doppler boosting" changing brightness depending on the viewing angle — zoom out to see the fast jet where the latter effect is especially pronounced. Faint markers show where other viewers are standing right now.

Alternatively, put the black hole in front of your camera and watch it lens your actual surroundings. Light winds around the hole, so you see both what's in front of you and what's behind you at once (when the device and browser allow both camera feeds). The closer to the black hole, the stronger the bending — and the longer the light-travel delay: wave at it and watch the changes propagate inward. (unfortunately, WebXR restrictions make AR passthrough and the camera feed mutually exclusive)

No signup, basic features work on every device, no data uploaded — the camera feed never leaves your device. Source code: https://github.com/aplavin/blackhole.plav.in.

Enjoy having a black hole in your room, or use it for education/outreach — any questions, feedback, or suggestions are welcome!

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Discussion (23 Comments)Read Original on HackerNews

dluan•about 1 hour ago

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.

aplavin•3 minutes ago

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.

BLKNSLVR•6 minutes ago

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.

chamomeal•37 minutes ago

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

aplavin•6 minutes ago

Looks interesting from the first glance! I should probably try that game – having both the artistic and realistic pictures in mind :)

efilife•about 1 hour ago

Same. Especially with circular objects. Placing the black hole in my room using the AR mode was very distressing for me

Waterluvian•about 2 hours ago

It’s fascinating how things that were inverted seem to become corrected when I point this at the pre-existing black hole in my room.

csmoak•about 1 hour ago

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?

ninjahawk1•19 minutes ago

Them: you can’t see what’s on the inside of a black hole

Me: zooms in

aizk•about 2 hours ago

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.

hahahaa•about 2 hours ago

First time I have AR'd. That was cool. How does it keep the hole in the same point in space as I walk about?

dmd•about 2 hours ago

The app doesn't have to do this itself, phones do it for you. ARCore on Android, ARKit on iOS.

hahahaa•about 2 hours ago

Oh yeah I mean how do the phones do that. I guess it uses dead reckoning with visual cues and some machine learning.

aplavin•13 minutes ago

In my experience, on Android, it definitely relies on camera: AR doesn't work in dark room, and barely works in slightly-lit room. So it must be fusing camera + accelerometer + ...

forsalebypwner•about 1 hour ago

on iPhone 12 Pro Max and later (maybe only on Pros, I forget) they have a LiDAR sensor built in, allowing for impressively accurate 3D scans of objects with a free app like Scaniverse. But yeah I think AR was the intention there

dmd•about 1 hour ago

"SLAM" is the term to google.

boothby•about 1 hour ago

Your phone has an accelerometer, which can be integrated twice to result in slightly accurate dead reckoning; just keep accumulating 3-vectors with every time-slice. That's a helluva lot easier than visual cues.

charcircuit•24 minutes ago

Wouldn't physically accurate turn your entire screen black? I would expect it to suck in way way more light than the example shows.

aplavin•9 minutes ago

Black holes don't really "suck in" light :) Whatever falls onto the black hole itself gets deleted, of course – but otherwise, it bends light rays towards its center. That's why the app shows distortion + black circle in the in middle in the camera mode.

api•about 2 hours ago

The singularity is near.