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

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

#61

Post by 20k »

csmoak wrote: post #15

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?

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 good

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

#62

Post by ButlerianJihad »

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…

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.

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

#63

Post by kortilla »

brador wrote: post #59
cwnyth wrote: post #56

Earlier quoted context omitted.

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?

Hypochondriac

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

#64

Post by antonvs »

matheusmoreira wrote: post #57
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.

They don’t have to be gargantuan (except in terms of mass) - the low end of stellar mass black holes can have radii as small as 6 km.

Many black holes have a bright accretion disk outside their event horizon, so visibility for those is not an issue.

But it’s certainly possible to have maximally scary black holes that have no accretion disk and are small enough so as not to cause significant lensing. You could fly your spaceship straight into one of those without even realizing, until you start turning to spaghetti.

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

#65

Post by antonvs »

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…

The translation of the name appears to be intended as “black star fear”.

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

#66

Post by matheusmoreira »

antonvs wrote: post #64
matheusmoreira wrote: post #57

Earlier quoted context omitted.

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.

They don’t have to be gargantuan (except in terms of mass) - the low end of stellar mass black holes can have radii as small as 6 km. Many black holes have a bright accretion disk outside their event horizon, so visibility for those is not an issue. But it’s certainly possible to have maximally scary black holes that have no accretion disk and are small enough so as not to cause significant lensing. You could fly you…

Yeah I remembered the accretion disks immediately after posting and edited the comment.

> it’s certainly possible to have maximally scary black holes that have no accretion disk and are small enough so as not to cause significant lensing

Now that's a proper cosmic horror.

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

#68

Post by antonvs »

somenameforme wrote: post #48
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.

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.

It’s arguable whether it’s weird or undesirable. There are benefits to using unusual words when they have precise scientific or other technical meaning. It helps identify them as terms of art, so that they’re not confused with their native tongue equivalent, which invariably has much looser meanings.

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

#69

Post by LeoPanthera »

matheusmoreira wrote: post #57
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.

Someone correct me if I'm wrong, and maybe it depends on the type of the black hole, but if you were to fall directly into one, or even enter an orbit too close, you would still be seen - and seen for an extremely long time.

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

#70

Post by EugeneOZ »

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…

“Physically accurate” indeed raises the bar significantly.

You’ve already done great work here. That said, the feedback seems to come from someone who spent considerable time analyzing your work. Even if only a few of the suggestions are ultimately valuable, that’s still a meaningful contribution and worth considering.

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