Unveiling the first-ever image of a black hole [video] • Hacker News Board

Re: Unveiling the first-ever image of a black hole [video]

#511

Post by wallace_f » Fri, Apr 12, 2019, 1:47 AM UTC

darkpuma wrote: post #360

wallace_f wrote: post #355

Earlier quoted context omitted.

It's really strange that you are unable to understand such a simple complaint I made, even after going to extra effort to spell it out. You even have even become aggressive insulting. I understand that some people become that way when they get confused, but how is it possible you are confused here? I think you are literally not even reading my comments. Either that, or you are going through some personal issues right…

Mate, you insulted me first, and have just repeated that insult again. I've tried to be charitable with you.

How did you come to the conclusion that I "insulted you first?"

Re: Unveiling the first-ever image of a black hole [video]

#512

Post by code_duck » Fri, Apr 12, 2019, 11:19 AM UTC

rexpop wrote: post #356

arriu wrote: post #260

Earlier quoted context omitted.

The video by Veritasium is by a guy who literally got a PHD on the subject of making physics more approachable through videos. He is exactly the person I would expect to provide a more clear and understandable explanation. https://www.youtube.com/watch?v=S1tFT4smd6E&feature=youtu.be...

Why doesn't he work with the actual astronomers, then?

Because he’s busy making physics more approachable through videos.

Re: Unveiling the first-ever image of a black hole [video]

#513

Post by albedoa » Fri, Apr 12, 2019, 11:36 AM UTC

wallace_f wrote: post #466

albedoa wrote: post #441

Earlier quoted context omitted.

The whole video was him explaining why the image would look the way it ended up looking. darkpuma was overly patient when explaining this to you.

You were a user acting in bad faith that very literally jumped in at the end just to write a troll bait comment in that thread. Your comment had nothing substantive to even do with any discussion, or even any relation to anything I said. There is nothing complex about my original statement there. The EHT website itself has a gallery of simulated images and I'd like to know why he chose that one specifically. In the v…

Can you link to the comment of yours that I replied to? I can't see it for some reason.

Re: Unveiling the first-ever image of a black hole [video]

#514

Post by ataturk » Fri, Apr 12, 2019, 1:54 PM UTC

Cthulhu_ wrote: post #485

exelius wrote: post #468

Earlier quoted context omitted.

So put some telescopes in orbit around the Moon and Mars.

A guy on Reddit actually asked this in the AMA. While that would increase the resolution, it would also be extremely difficult. The algorithms used to combine the data from the dishes relies on the exact position of the dish being known at the time of measuring, to a precision of fractions of millimeters. It's already hard to do on the earth's surface, but imagine doing it with a sattelite zipping around the earth at…

I predict we'll do it, though.

Re: Unveiling the first-ever image of a black hole [video]

#515

Post by SamBam » Fri, Apr 12, 2019, 2:08 PM UTC

salthound wrote: post #487

SamBam wrote: post #461

Earlier quoted context omitted.

That's a... weird analogy.

I think the actual analogy was lost in translation: the point is that, unlike its older brother, Sgr A* is not going to "pose" when you point your camera at it.

Ah, I thought it was about actually shooting bears and toddlers.

Re: Unveiling the first-ever image of a black hole [video]

#516

Post by thanatropism » Fri, Apr 12, 2019, 6:44 PM UTC

kardos wrote: post #335

Mizza wrote: post #233

Earlier quoted context omitted.

Grrr, why aren't scientists all using perceptually uniforms color schemes! This would still look awesome in `plasma`. Is there any where I can get the data and do it myself? One of my favorite talks ever is on this subject: https://www.youtube.com/watch?v=xAoljeRJ3lU

Can you run it through the colormap in reverse to (approximately) recover the data?

Technically yes -- colormaps are 1-dimensional non-self intersecting curves in RGBA space. You just grab them by the... I mean just straighten them.

I don't know if an explicit formula for the colormap is given, but you can always do "xs = np.linspace(0,1,100); ys = { cm.hot(x):x for x in xs}" and recover an approximate inverse. Then apply this function to each pixel of the image.

Re: Unveiling the first-ever image of a black hole [video]

#517

Post by ImaniBlack » Fri, Apr 12, 2019, 7:42 PM UTC

neals wrote: post #398

jjeaff wrote: post #276

I am not trying to throw cold water on this, but I have some questions. This ted talk has a very basic explanation of how they constructed this image. I was curious if anyone with image interpolation experience could weigh in on the method. https://www.youtube.com/watch?v=P7n2rYt9wfU When she first starts explaining their method around 8:00m in, I was initially very skeptical of this result because she said that they…

Was just wondering this myself. How opinionated is this photo?

Probably very opinionated. I can't help but take this with a grain of salt. relevant example .How long did it take for people to evolve our view of dinosaurs as information was reevaluated.

Re: Unveiling the first-ever image of a black hole [video]

#518

Post by manigandham » Fri, Apr 12, 2019, 8:32 PM UTC

wallace_f wrote: post #510

manigandham wrote: post #509

Earlier quoted context omitted.

There are 4 images on that page, 1 of which is the Interstellar movie rendition that I already linked to. They are also all the same model only in better detail as graphics technology has improved. Perhaps you should post exactly what image you're talking about and what you think is different.

In the images I linked to, the black hole images don't have any "blobbiness," and seem to have these perfect gradiants. In the veritasium video the "coffee stain" was not really as blobby as the real image, but it seemed a lot closer than the smooth-gradiant, no blobbiness and no irregularities predictions. I dont just mean the fuzziness from low resolution. This isn't really a big deal, but it's also obvious that I…

The general model of what a black hole looks like is well understood. The highest definition rendering is that in Interstellar, except for one side being brighter than the other due to the relativistic beaming. They kept that part out of the movie to just make it look nicer.

All the models are the same, and the real picture is "blobby" only because of the process in how it was taken. I think you are refusing to accept that but there's nothing else to say about it. It wasn't a direct photo, it was a complex assembly of several different radio telescopes around the world stitching data together. If we were actually next to it, it would very much look like the one from interstellar.

The video you linked isn't about the prediction being wrong, more that he just didn't expect to really see a black hole at all. Even though black holes are generally understood for decades, there's a certain shock and awe to seeing it real for the first time.

Re: Unveiling the first-ever image of a black hole [video]

#519

Post by salty_biscuits » Fri, Apr 12, 2019, 9:18 PM UTC

jjeaff wrote: post #277

noir_lord wrote: post #167

Earlier quoted context omitted.

It's good science. Been able to make testable predictions and then confirming them or disproving them is the entire (awesome) point.

After having said that, I did a bit more research into how the image was made. I am of course reserving judgement as I don't fully understand the underlying technology. But it sounds like they used an interpolation algorithm to come up with the image based on renderings of what we "think" a black hole should look like. This high level overview from a ted talk goes into how they 'unbias' the data. But it is obviously…

This sort of reconstruction problem from VLBI measurements is under-determined so you need to insert priors/regularization to get anything at all. The priors in this case are pretty weak (from a quick read of the CHIRP paper). https://arxiv.org/pdf/1512.01413.pdf

Re: Unveiling the first-ever image of a black hole [video]

#520

Post by wallace_f » Sat, Apr 13, 2019, 12:01 PM UTC

manigandham wrote: post #518

wallace_f wrote: post #510

Earlier quoted context omitted.

In the images I linked to, the black hole images don't have any "blobbiness," and seem to have these perfect gradiants. In the veritasium video the "coffee stain" was not really as blobby as the real image, but it seemed a lot closer than the smooth-gradiant, no blobbiness and no irregularities predictions. I dont just mean the fuzziness from low resolution. This isn't really a big deal, but it's also obvious that I…

The general model of what a black hole looks like is well understood. The highest definition rendering is that in Interstellar, except for one side being brighter than the other due to the relativistic beaming. They kept that part out of the movie to just make it look nicer. All the models are the same, and the real picture is "blobby" only because of the process in how it was taken. I think you are refusing to accep…

Lol ok then we can agree to disagree. Even the YT video I just linked to opens with an intro containintlf a simulation, which once again, has subtle but pretty obvious and appreciable differences.

Also, my complaint was in fact that I didnt know why Veritasium was confident in their prediction. This complaint is for a matter of fact completely consistent with one of the lead researchers outright saying they didn't know what to expect. I never said I was exclusively complaining about there being simulated models which have some differences. You and others criticized me after I said he should have substantiated why he was confident in his prediction. I gave what I believed was my the foremost reasoning for saying that.

I had little idea what the picture would look like...

I have no idea why you're so intent in disagreeing with me. I'm substantiating my ideas with facts. And saying 'just bbelieve me' I think is also bad form.

At this point I feek like your disagreement has to do with psychological or social biases unless you are able to address the factual content of my comment.

But the one thing you said that was interesting was about the blobbiness. I think what you are trying to saya is that it is fully expected by the researchers to be error. Do you have a good interview or other source on this?