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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

#51

Post by watutalkinbout »

BLKNSLVR wrote: post #25
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…

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…

Dived with them in the Red Sea. They can get pretty massive, and it can be slightly unsettling close up. They are odd creatures.

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

#53

Post by aplavin »

rgovostes wrote: post #49

See also: Black Hole Vision for iOS from Vanderbilt University. https://apps.apple.com/us/app/black-hole-vision/id6737292448

Yes, linked in the readme! They simulate light bending, but ignore time delay effects.

I think the earliest of these black-hole-camera renderings is https://dominic-chang.com/bhi-filter/ though (also linked in readme) – a direct inspiration for the camera mode in my app!

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

#54

Post by khedoros1 »

chamomeal wrote: post #18
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…

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

Outer Wilds is exactly what came to mind for me, too. Made a jump...missed. Thrown into a decaying orbit around the black hole. Absolutely terrifying, and panicking didn't help in the least!

And getting close to the upper atmosphere of Giant's Deep for the first time, staring, thinking about the atmospheres of real-world gas giants, knowing that I need to take the plunge.

That game exposed some phobias that I'd only been vaguely aware of before.

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

#55

Post by 20k »

aplavin wrote: post #50
20k wrote: post #45

Earlier quoted context omitted.

>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…

>I don't see "simplified" as being opposite to "accurate".

Are black hole accretion disks generally red in real astrophysical cases?

They're most accurately represented as being blue. Red is fine for visualisations because it looks cool (which is fine!), but blue is the physically accurate colour. Visualisations claiming to be accurate like this presenting red black holes is becoming an increasingly large science communication problem

The way that the colour and brightness are mapped together is also not correlated correctly, and some of the equations just aren't right. The doppler isn't correct at all here, partly because its simulated incorrectly (with the camera problems), and partly because the mapping done at the end doesn't correlate to any reasonable brightness

Stuff like this: Its not accurate at all. It isn't simplified, its just wrong - which is totally fine for a visualisation, if that's the intent. But:

>scales like logarithmic are very common in scientific images.

Sure. What scale are you using for the doppler brightness here? Because as far as I can tell, its a piecewise mapping of the form ~pow(x, 2.2), after being run through a non smooth function `afmhot` - a function which doesn't have a linear brightness response. So the brightness in this image doesn't really correspond to anything related to doppler or brightness, and the colour also doesn't correspond to anything involving colour (or the doppler). The entire image's look is basically accidental

Here's a specific comment from the event horizon telescope talking about exactly this problem with specifically the afmhot transform being used, because its important for visualisation:

https://github.com/achael/eht-imaging/issues/85

Which shows some of the problems here

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

#56

Post by cwnyth »

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.

Helio- is actually "sun", not "hole", and it's Greek, not Latin, but I 100% agree with you: it's pointless technical vocabulary that only serves to obfuscate. I think in this particular case, it's just some internet neologism (which is a good word, since coinage can mean a couple different things), made based on analogies with older phobias. For those of us who know Latin and Greek, though, all we can really do is shrug at the eagerness to make the clumsiest words possible.

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

#57

Post by matheusmoreira »

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…

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.

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

#59

Post by brador »

cwnyth wrote: post #56
GavinMcG wrote: post #32

Earlier quoted context omitted.

> 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.

Helio- is actually "sun", not "hole", and it's Greek, not Latin, but I 100% agree with you: it's pointless technical vocabulary that only serves to obfuscate. I think in this particular case, it's just some internet neologism (which is a good word, since coinage can mean a couple different things), made based on analogies with older phobias. For those of us who know Latin and Greek, though, all we can really do is sh…

What would be the correct latin/greek word for it?
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