181–190 of 204 posts
For a split-second thought they meant a Kugelblitz (black hole that in theory can be made from concentrating photons from lasers) https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)
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…
I clicked on this because I worked on the infra that simulated the famous blackhole sim in interstella. I thought "oooh this is interesting I wonder how they are going to do physically accurate on an end device" Recalling how the original particle sim was something like 100TB, took 2 weeks to generate and seemed to write in a way that killed disks. but that was >10 years ago, so what clever stuff has been done to mod…
Sorry for confusion! Points + lines are just other users looking at the black hole right now, their camera locations and lines of sight. Nothing more! In the first hours of HN frontpage, there were a lot – and I can see how one can understand them as parts of actual scene :)
I decided not to change their style, not to make them more subtle – half a day later, there are already way fewer users online, and these points/lines don't look as crowded as they did.
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What exactly is physically accurate here though? Because its not: 1. The relative brightness of different parts of the image 2. The colouring 3. The general relativistic effects of a black hole, other than the most basic disk warping effect 4. The relative colouring or brightness change from doppler When you make a post about a physically accurate rendering, people usually expect it to be a decent representation of t…
> What exactly is physically accurate here though? I'll assume this is a good faith question, hope it was intended like one. I view strong light bending as the key distinguishing property of a black hole, and something we are fairly certain about. This is reproduced accurately in all modes, up to the fundamental technical constraints of the browser environment. Gravitational redshift is another one, and it's also ref…
>As for colormapping: I follow the by-far-dominant approach in scientific literature, where color mapping choice is completely unrelated to physical accuracy of the plotted observations or simulations. Having a preference for different color schemes is a matter of taste; suggesting a linear intensity->pixel mapping is a reasonable feature request, but far from a bug or inaccuracy.
It is not true at all that this is the dominant approach in the literature, the event horizon telescope does not use this approach in their papers. I linked a comment from them elsewhere about this in a github PR
Specifically:
https://github.com/achael/eht-imaging/issues/85
>Unfortunately, vanilla afmhot does remain the current default in the eht-imaging library for historical reasons, but this could change soon. *Rest assured we thought of this issue and the paper images are indeed perceptually uniform!*
I would welcome an attempt for you to create a scale, that maps the output pixel brightness to the underlying physical luminance, which I think would show why the mapping is such a problem here from an accuracy perspective, but you're absolutely not correct that you're following the literature here. People are much more careful about presenting accurate data, and your approach would result in a correction being put out
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 why was the picture taken of black hole have accretion disk yellow?
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> What exactly is physically accurate here though? I'll assume this is a good faith question, hope it was intended like one. I view strong light bending as the key distinguishing property of a black hole, and something we are fairly certain about. This is reproduced accurately in all modes, up to the fundamental technical constraints of the browser environment. Gravitational redshift is another one, and it's also ref…
So in your opinion, the primary thing that makes this a physically accurate simulation is that you've calculated the bending of light rays, and the structure, colouration and brightness of the accretion disk doesn't matter at all? >As for colormapping: I follow the by-far-dominant approach in scientific literature, where color mapping choice is completely unrelated to physical accuracy of the plotted observations or…
> It is not true at all that this is the dominant approach in the literature
Just to clarify: you are saying that there are not a lot of images in literature rendered with a non-perceptually-uniform colormap (eg, any matplotlib colormap aside from the 5 uniform ones)? Or that there is only one correct way to choose colormap for a given image?
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> 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". Is it accurate to model a cow as a sphere?
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So in your opinion, the primary thing that makes this a physically accurate simulation is that you've calculated the bending of light rays, and the structure, colouration and brightness of the accretion disk doesn't matter at all? >As for colormapping: I follow the by-far-dominant approach in scientific literature, where color mapping choice is completely unrelated to physical accuracy of the plotted observations or…
>> I follow the by-far-dominant approach in scientific literature, where color mapping choice is completely unrelated to physical accuracy of the plotted observations or simulations. > It is not true at all that this is the dominant approach in the literature Just to clarify: you are saying that there are not a lot of images in literature rendered with a non-perceptually-uniform colormap (eg, any matplotlib colormap…
There is more than one choice as explained previously, it depends on what information you intend to communicate, whereas here the plot doesn't represent anything. I don't want to be rude, but this is plots 101, where the intensity does absolutely matter in your figures at minimum for renderings
I'd very highly recommend trying to create a scale for your work here to observe the problems with the approach in colouring and brightness, to check how it would work if you were to try and take one of these images and publish it in a paper, and compare it against other published intensity plots of black holes. People do make mistakes here, but its usually unintentional and a mixup due to not understanding gamma correction, which does indeed sometimes result in corrections
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Well, I think the tide of LLM flotsam inundating the submissions makes HN a worse place. So I'll keep on complaining, and you can downvote me about it.
> Well, I think the tide of LLM flotsam inundating the submissions makes HN a worse place. writing the 1000th "llm garbage is bad" comment of the day is your solution? im not sure i understand the logic, despite agreeing with the premise.
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When this topic comes up, I'm always happy to share this incredible lecture from many many years ago about sensor fusion and dead reckoning and how you _cannot_ integrate acceleration twice: https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s (the whole video is incredible, but this timestamp is the magical bit)
So you tend to need additional data or assumptions to constrain the double integral?
1) An absolute positioning system like GPS.
2) A visual positioning system like fiducial markers or SLAM.
3) Something that can measure linear speed and then you integrate the speed only once. Easy to do on vehicles, but even the most accurate system will quickly drift.
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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…
Or when you do a space walk, just kinda pop feet first out of your little ship. Scares the bejeesus outta me