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

blackhole.plav.in

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

#41

Post by charcircuit »

aplavin wrote: post #24
charcircuit wrote: post #20

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

If this app turns the entire screen black, this probably means WebGL is not supported :) 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.

The event horizon for even the smallest black hole is in the scale of kilometers. If the user is a meter away from the black hole light isn't going to move away from the center of it to your camera.

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

#42

Post by lmpdev »

ViscountPenguin wrote: post #35
BLKNSLVR wrote: post #25

Earlier quoted context omitted.

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…

It's Sea World in Queensland, but confusingly I think the company is unrelated to the American Sea World, iirc they bought a license to the name back when it was probably a lot more positive than it is now. EDIT: Apparently not licensed, just completely unrelated.

Yes they’re not related and are much more humane imho

No Orcas, good rehab program, seal exhibit is good (no true seals), Polar bears are a bit sad though

I did the seal diving experience which was great - mostly disabled California sea lions and NZ Fur seals (which do well in captivity)

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

#43

Post by csmoak »

aplavin wrote: post #38
csmoak wrote: post #36

Earlier quoted context omitted.

Oh nice, I had not zoomed out enough. I don't think I've seen the relativistic jets rendered before. The AR mode looks great on my phone. Yep, I had fun learning a lot about punchcards, Fortran, and the math behind black holes. I suspect I'm doing something similar to you in my Fortran implementation, raymarching along the null geodesic to come up with my final image: https://imgur.com/a/czysDls Also, I have to point…

Actually, the jet was the first part of the app – I wanted to just see and "feel" relativistic beaming in practice, in physical space. And it was fun and instructive indeed! Really puts into perspective how tight is the jet vs line-of-sight alignment for those bright jets we see across the universe. And how beaming is the dominant effect that determines the jet/quasar appearance.

I guess the fact we see any at all given the distance and small angles just emphasizes how many there are out there...

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

#44

Post by aplavin »

charcircuit wrote: post #41
aplavin wrote: post #24

Earlier quoted context omitted.

If this app turns the entire screen black, this probably means WebGL is not supported :) 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.

The event horizon for even the smallest black hole is in the scale of kilometers. If the user is a meter away from the black hole light isn't going to move away from the center of it to your camera.

Now I think I see what you meant. There actually are no upper/lower limits on the black hole size (in classical physics – ignoring quantum effects). Compressing the Earth to ~1 cm in size would give you a black hole, and its event horizon size would be ~1 cm, not kilometers. And even black holes this small are stable, according to our physics knowledge.

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

#45

Post by 20k »

aplavin wrote: post #37
20k wrote: post #34

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…

Some are fair – of course this is a simplified visualization! Observationally, we don't really know how fast a given black hole is rotating, and here I indeed assumed a non-rotating one. It's not an inaccuracy per se, more like a missing feature. The camera mode has a (half-hidden) toggle to enable Kerr metric and set spin, but even there it's not a default. I consider the colormap choice to be completely arbitrary t…

>of course this is a simplified visualization

Its titled a "physically accurate black hole"! Please don't do this, if its intentionally not physically accurate and heavily simplified! The general public on here don't know better, and it takes someone else with years of experience simulating black holes to dig through your code to show what you've simplified. There's like a few hundred people who have the right experience worldwide to know that you've got some of your equations incorrect

The issue is when you're communicating doppler, if you want to correctly show the change in doppler, you can't make the intensity or colour mapping arbitrary

There's two ways to communicate accurately an example linear change in emissive power:

1. Use a perceptual brightness system, so that a linear change in power represents a linear perceptual change in perceived brightness. This accurately communicates to a viewer the underlying shift in power emission, if you want to show off how a radio telescope perceives a black hole for example

2. Use an emitted power sRGB mapping (with tonemapping), so that a linear change in power is perceived as if it were a physical light getting brighter. This is more "what would this look like to a person?"

At the moment the change in your image brightness doesn't correspond to anything, which means that its not really communicating any science, and it doesn't correspond to doppler. Which is fine if its just illustrative and that's clear, but again vanishingly few people will know this is a visualisation not a physically accurate render

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

#46

Post by recursivecaveat »

qwertywert_ wrote: post #40
dluan wrote: post #14

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 nea…

Sorry but a word for fear of black holes is ridiculous. Black holes are scary period. Anyone not feeling a deep sense of fear during that VR experience is missing something.

Definitely one of the most malevolent possible objects. Infinitely black, so powerful it will kill you without noticing your presence, unknowable, impossible to get rid of, you will be well aware you can't escape as you fall in before it turns you into spaghetti Amigara Fault style. My understanding is from the outside you can even see the remains of previous victims being stretched and crushed in slow motion.

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

#47

Post by defrost »

charcircuit wrote: post #41
aplavin wrote: post #24

Earlier quoted context omitted.

If this app turns the entire screen black, this probably means WebGL is not supported :) 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.

The event horizon for even the smallest black hole is in the scale of kilometers. If the user is a meter away from the black hole light isn't going to move away from the center of it to your camera.

This is recent conjecture?

I grew up with micro black holes being a possibility, with conjectures such as primordial black hole evaporating down to Planck dimension stability, etc.

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

#48

Post by somenameforme »

GavinMcG wrote: post #32
dluan wrote: post #14

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 nea…

> 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.

I've also wondered the same thing about healthcare and other fields. All the complex sounding phrases are child-like in simplicity in their "native" tongue, yet completely indecipherable to most people in modern times. Quite a weird and undesirable path we ended up going down through inertia.

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

#50

Post by aplavin »

20k wrote: post #45
aplavin wrote: post #37

Earlier quoted context omitted.

Some are fair – of course this is a simplified visualization! Observationally, we don't really know how fast a given black hole is rotating, and here I indeed assumed a non-rotating one. It's not an inaccuracy per se, more like a missing feature. The camera mode has a (half-hidden) toggle to enable Kerr metric and set spin, but even there it's not a default. I consider the colormap choice to be completely arbitrary t…

>of course this is a simplified visualization Its titled a "physically accurate black hole"! Please don't do this, if its intentionally not physically accurate and heavily simplified! The general public on here don't know better, and it takes someone else with years of experience simulating black holes to dig through your code to show what you've simplified. There's like a few hundred people who have the right experi…

> Its titled a "physically accurate black hole"! Please don't do this, if its intentionally not physically accurate and heavily simplified!

It also doesn't exert the gravity an actually accurate black hole should :) And also, even on a phone with two cameras, they only cover a part of sphere – while a real black hole would bend light coming from all 4pi directions. Some simplification is generally required ("the map is not the territory") and I don't see "simplified" as being opposite to "accurate".

Colormap choice: it can be a useful mode to show proper linear power -> linear perceived brightness mapping – true! But that's only one of many possible choices, and scales like logarithmic are very common in scientific images.

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