# HN Theater

The best talks and videos of Hacker News.

### Hacker News Comments onBreakthrough discovery in astronomy: first ever image of a black hole

HN Theater has aggregated all Hacker News stories and comments that mention European Commission's video "Breakthrough discovery in astronomy: first ever image of a black hole".
On 10 April 2019 at 15:00 CEST (Brussels time) the European Commission presented a ground-breaking discovery by Event Horizon Telescope - an international scientific collaboration aiming to capture the first image of a black hole by creating a virtual Earth-sized telescope. EU-funded researchers play a key role in the project.

Black holes are extremely compressed cosmic objects, containing incredible amounts of mass within a tiny region. Their presence affects their surroundings in extreme ways, by warping spacetime and super-heating any material falling into it. The captured image reveals the black hole at the centre of Messier 87, a massive galaxy in the constellation of Virgo. This black hole is located 55 million light-years from Earth and has a mass 6.5-billion times larger than our sun.

Six press conferences around the world took place simultaneously. In Europe, Commissioner Moedas and lead scientists funded by the European Research Council held a press conference in Brussels to unveil the discovery.

Panelists:
- Carlos Moedas, European Commissioner for Research, Science and Innovation
- Prof. Anton Zensus, Director at Max-Planck-Institut für Radioastronomie, Bonn, Germany (Chair of the EHT Collaboration Board)
- Prof. Heino Falcke, Radboud University, Nijmegen, The Netherlands (Chair of the EHT Science Council)
- Dr Monika Mościbrodzka, Radboud University, Nijmegen, The Netherlands (EHT Working Group Coordinator)
- Prof. Luciano Rezzolla, Goethe Universität, Frankfurt, Germany (EHT Board Member)
- Prof. Eduardo Ros, Max-Planck-Institut für Radioastronomie, Bonn, Germany, (EHT Board Secretary)

EC press release: https://europa.eu/!nr97rr

Scientific press release by EHT: https://blackholecam.org/erc_bhc_pr-2/

More insights by Jonathan O’Callaghan's article: https://europa.eu/!mb77wB

Behind the scene with the black hole scientists: https://europa.eu/!xx46nf

#EHTBlackHole #BlackHoleDay #RealBlackHole #BlackHoles
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#### Hacker News Stories and Comments

All the comments and stories posted to Hacker News that reference this video.
Apr 10, 2019 · 2164 points, 488 comments · submitted by doktorn
And a really great explanation of why it looks the way it does:
editing that image reveals all kinds of details: https://imgur.com/a/TvQsgbA (and I don't even know what I'm doing)
Those 'details' aren't real. The image is the result of a complex interpolation algorithm that takes very noisy and incomplete data as its input. The resolution is quite limited.
I do (I think...) the bands are atifacts:
Mind you, that's a JPG you are editing, so in the 8 bit sRGB color space. That means manipulations can lead to errors and illusions due to the color space being non-linear and clipped[0].

The original data was likely linear and at a much higher precision. If the source was a 16 bit linear grayscale PNG for example you could be much more assured you're not seeing the effects of JPG compression and things that were actually measured.

EDIT: Found better sources:

16-bit sRGB PNG: https://eventhorizontelescope.org/files/eht/files/20190410-7...

180 MiB original TIFF: https://www.eso.org/public/images/eso1907a/

Thanks a lot for the explanation and the better sources, the TIFF image should probably be a torrent because it's not downloading very fast, the PNG image does give much nicer renders: https://i.imgur.com/zZcD5Na.jpg
The article linking to that image: https://nsf.gov/news/news_summ.jsp?cntn_id=298276
The additional pixel density probably doesn't add any details though. The original image looks like a smoothed-out version of a low-res image anyway...
Is this link down for anyone else?
Probably because of HN effect again. Yes it is down.
Slashdot effect
Can someone stick it on IFPS?
apo
It really needs a scale marker. How many light years across?
nprz
whoever took this picture should be fired, it's way out of focus!
"High res"
So how much this picture cost ?
Whenever this type of question comes up, how much science cost, think about the following:

It costs more to do a sciency Hollywood movie about than it costs to actually do the science. Sending an actual probe to the orbit of Mars is in general cheaper than making a sci-fi movie.

So...

$40m So basically nothing in the grand scheme of anything. acqq That's half the cost of a single F-35 fighter plane. Just US alone will pay for around 2500 of them (2010 estimate), and plans to pay around 4 times more than that to maintain them. So just F-35 total costs for US are equivalent to 25000 scientific projects like this one. To compare, it would be one new project like this every day for 70 years! This specific project is more European or even a world project than just US, if I understood correctly. It makes sense to compare the costs to a single plane but to the whole fleet is just stupid. You can't defend a country with scientific projects. The thing is every time someone proposes the idea to slash the military budget to fund something else there are at least a hundred other people with a different idea on what to use the funds on. If the funds were spread over so many different projects you end up with an insignificant sum in each of them. Spending the money on military might be actually be advantageous because of large investments in new military technology end up benefiting the civilian sector. (Isn't that the point of the F-35?) acqq It’s the opposite: most of the military money goes to the stuff which, if actually used, ends the human civilisation as we know it. The same goals that US has could be achieved with orders of magnitude less military spending, while also reducing the risks for the whole humanity. So every alternative to the current practices is infinitely better. I've taken to measuring moderately large amounts of money in "juiceros". Forty million dollars is one third of a juicero. the original tiff is 7416x4320 it's still too many pixel, it can be a fifth of that while conveying the same amount of information. I'm puzzled by this, if each of those pixel is actually captured by the lenses, why is it all this much uniform? was it smoothed or does this suggest that it's actually a gigantic uniform cloud of gas? haven't seen the whole video of the release, I'll have to catch up later in the evening, but this really seems to have captured way too much compared to the actual lens resolution and I wonder what would be the "confidence interval" or astrophysical equivalent on each of those pixels. The picture is not captured by lenses, or an optical telescope at all. It is created by inverting the data received at eight radio telescopes (or eighty individual dishes) around the world. And the smoothing is just due to the inherent limit in the resolving power of the telescope array. The impressive bit is that we see more than a single bright dot. From the press conference, they said that the raw captured data took up 6 cubic meters of hard drives > cubic meters of hard drives Astronomy and high energy physics are pretty much the only science I know where this is an applicable unit of measurement There is no lens. This was done using eight radio telescopes (or arrays) around the globe to create a "virtual" radio telescope which is effectively the size of the earth. After that the data of the individual telescopes was processed to produce an image. There is some more info in the wikipedia article for the Event Horizon Telescope (EHT): https://en.wikipedia.org/wiki/Event_Horizon_Telescope Thanks for the link. More reading reveals the amount of data produced goes into Petabytes. You can't just upload it to drop box or push it via FTP; hence correct icon of an airplane because those drives with data are indeed delivered by regular means of transportation. Does that image have a weird pulsing optical illusion for anyone else? I think my eye is trying to bring it into focus. It is like when the camera on your phone can't quite figure out what it is looking it and keeps adjusting. I suspect this is because it's extremely blurry, if you watch it on a large screen it might trick your eye into trying to refocus, obviously without success. Interesting that so many people see this but for me it's absolutely static. If you are focused and calm, or have bad sight, you won't see it naturally. To force it, move your focus from 1cm to the left, then right, again and again, quickly. Yes, reminds me of the Eye of Sauron. The supreme astronomical example of the Eye of Sauron is this Hubble shot of the star Fomalhaut and its debris disk: https://en.wikipedia.org/wiki/Fomalhaut#/media/File:Fomalhau... Reminds me of Indian food - Vada - https://en.wikipedia.org/wiki/Vada_(food) :) Funnily, it reminds me of Soundgarden's album, Superunknown, which had the famous song 'Black Hole Sun.' chki Yes, fascinating! If you shift the focus of your eyes from the outside to the inside of the hole, it seems to "pulsate" looks like the image data was cleaned up with bicubic interpolation, or something of the like. Tor3 I don't even have to move my eyes, I stare at it and it's constantly moving away from me. I had to check that it's not actually a movie. Strangest thing. Yes, and I also see a spot in the shape of it after looking away, though that may just mean my monitor is too bright Some time ago I've seen a picture over the Internet where the description said the more you see it "moving" the more likely you're stressed. As for the black hole, looking it at full screen I see it pulsating a little. Yes if you dance your focus around the image, it appears to pulsate. Probably your pupils constricting and dilating due to the high contrast in the image. It does look like it pulsates to me! That's an interesting illusion :) neom Stare at it till there are two, then have fun snapping them in and out. Relieved it isn't just me I get it if I move a bit when on an angle, I assume it's just my crappy monitor's viewing angles causing it. moving the picture on my screen caused some eye bug You mean to tell me this is not a gif?! I literally did double-check the file extension It's the color scheme. I think in matplotlib it's called "hot". I do a lot of 2D kernel density plots that by having a black zero level and dozens of contour levels produce a smooth look with aesthetics similarities to this. I used to use that scheme because "heatmaps" but stopped because of the pulsing illusion. I'm not sure if this image is real color or just lightness value and they used a color scheme for drama. It's the latter. This is an image in radio-frequency brightness of the object, so not visible frequencies of light. But yeah, it also looks like the 'hot' colormap to me. 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. Based on my analysis the published image is too processed to be able to invert the colormap to get to the brightness temperature data. I had better luck with Paper IV Fig. 15. See: https://physics.stackexchange.com/questions/472641/what-woul... You can easily remap it between different colour maps if you assume that is is a standard hot map. 'Inferno' would be nice for this, also perceptually uniform, and has the benefit that space is still black. Related video, made by Veritasium yesterday, is one of my favorite videos in a long time. He explained how the prediction of this image was made (before the image got released) and the video is great and fun to watch. Note that the prediction of the light being brighter on one side did come out. What are you basing that on? (Edit:) From one of the papers released today: > The ring is brighter in the south than the north. This can be explained by a combination of motion in the source and Doppler beaming. As a simple example we consider a luminous, optically thin ring... Then the approaching side of the ring is Doppler boosted, and the receding side is Doppler dimmed...This sense of rotation is consistent with the sense of rotation in ionized gas at arcsecond scales ..Notice that the asymmetry of the ring is consistent with the asymmetry inferred from 43 GHz observations of the brightness ratio between the north and south sides of the jet and counter-jet https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43 (Edit 2:) Ahh, I see your comment now says "did come out". I initially read it as "did not come out", which was either a misreading on my part (likely) or an earlier edit by you. Are north and south in astronomy defined relative to Earth’s poles? What about “lateral” directions, since east and west are relative (no poles, ie. no east of earth)? I don't know for sure how that's defined (I ctrl-f'd and it's not explained in the paper), but this says the "North" is to the right of the image, and from context it sounds like it's the north pole of the accretion disk, i.e., the direction of the rotation axis with the right-hand rule. > The approaching side of the large-scale jet in M87 is oriented west–northwest (position angle$\mathrm{PA}\approx 288^\circ ;$in Paper VI this is called${\mathrm{PA}}_{\mathrm{FJ}}\$), or to the right and slightly up in the image.

In paper I, Figure 3, it says North is to the top of the image and East is to the left.
Whoop. You're right. I misread again.
Using the right-hand rule: knowing the direction of spinning, if you point your thumb up and wrap the other four fingers in the direction of rotation, the thumb will be pointing North. Oposite of that is South. East can then be defined along the direction of spinning (eastward or counterclockwise looked from North, the way Earth is spinning) and West - opposite to that, clockwise looked from North, opposite the direction of rotation.
It's confirmed in the press conference by the scientists. They said its the Doppler beam effect
You mean the asymmetry was confirmed, contra ragebol's comment? (See the added quotes in my comment.)
a_d
Previous work on this was done for the movie Interstellar. The resolution of the rendering software was so high that team members were able to examine the black hole very closely - Because Gargantua was spinning at almost the speed of light, the rendering showed that spacetime warped into shapes never seen before. This led to the publication of —> https://arxiv.org/abs/1502.03808

Kip Thorne describes his work not this in a book called the science of interstellar.

Kip’s description of black holes here is also fascinating: https://youtu.be/oj1AfkPQa6M — first time I learnt what “warped” space-time means :)

> Kip’s description of black holes here is also fascinating: https://youtu.be/oj1AfkPQa6M — first time I learnt what “warped” space-time means :)

In this video he makes a comment which I struggle to fully understand:

He says that ALL of the matter which belonged to the cooled-off star is DESTROYED in the process of creating a black hole.

That concept of complete destruction eludes me. I assume what he means is, the matter was converted entirely to energy. Right?

But if that's true - where is all of that energy? Is it stored (somehow?) in the Black Hole? Is it dispersed throughout the galaxy? What HAPPENED to the mass (energy)?

It's all squished into the black hole and from the perspective of everyone outside, converted into... more mass of the black hole. The mass of the black hole comes from the mass that created it. As you feed it more stuff, it gets more massive.

As to what physically happens to the stuff once it's inside, I don't know if we know for certain. It gets dragged towards the center. From the point of view of the rest of the universe, it might never actually reach the singularity: GR would make it look like it's going slower and slower and slower.

Speculation about what is actually inside the event horizon is at most mathematical extrapolation, since we can't actually crack one open and look.

Sean Caroll has a great podcast, mindscape [0]. One of the recent episode featured Kip Thorne as a guest and had some great discussions about Gravitational Waves, Time Travel, and Interstellar [1]. It's a very informative and entertaining podcast, I recommend it.
Wow, that brings me back. I studied GR under Robert Brandenberger, and we used Caroll's book. What a wonderful text.

Definitely going to listen to his podcast!

a_d
Agree with the recommendation.

Kip has studied black holes all his life — this podcast goes into the work on LIGO that finally got Kip (and collaborators) the Nobel Prize. I found it amusing that there is some “Nobel guilt” for scientists that comes with the prize, because the size of them teams that usually collaborate and make a large project like LIGO happen (over 20 years) is incredibly large.

I also find it inspiring that Kip speaks with so much... love ... about warped space time :)

There is a video that I cannot find where Christopher Nolan describes the process of rendering the black hole for his movie - they used Kip’s equations to render Gargantua and when the first images were seen, he realized that Kip has never actually seen a black hole before - even though he has spent his entire life studying it.

International collaboration on scientific projects (International space station, CERN) always fills me with hope and optimism for humanity.

It's a nice contrast to opening the papers and reading the regular news, dominated by politics, with all the pessimism that creates.

Hooray for science.

So true, I was also recently thinking I should read more science/engineering news because that's actually positive stuff happening.
If I understand it, this class of “telescope” is made up of arrays of telescopes spread as widely over the hemisphere as possible. We can only get data like this by collaborating with as many different sites as possible. It literally can’t exist without broad support from many countries.

As one of the scientists said in the interview, the next step is a telescope bigger than the earth. Hopefully we can collaborate on those too but if that involves a lot of satellites in a heliocentric orbit that may limit contributions considerably.

aaco
I know this comment will sound a bit unrelated to the main topic but reading this made this thought pop up in my mind and I thought it would make sense to share it. This comment is, however, related to the sub topic of the quoted sentence:

> It literally can’t exist without broad support from many countries.

This is the same constraint for the, let's call it, "peace on Earth" problem, or just "peace".

If only more of us could realize this is what it takes to solve that problem... which itself is part of the puzzle, i.e. how to increase awareness about the need to solve this.

While there are a number of people and organizations trying to do this, I see that there seems to be more possible fronts that could be used to tackle this and accelerating the reach for stability and sustainability of the state of peace.

One example of a possible front (and I honestly don't know if those already exist) is: through marketing it would be possible to influence people enough to be interested in the outcome of "peace on Earth" and pay some money for that, in a way that it doesn't feel like a donation, and more like an investment or maybe acquiring a service that would be hopefully realized in the coming years (hence the importance of the marketing capacity of that entity, as this mindset needs to be set in the consumers in order to make them buy the good).

Of course, the reporting to the consumers on the use of the invested money toward that effort has to be as transparent and honest as possible, as those approaches are arguably required for a sustainable state of peace. And hopefully it would make enough sense for an entity to operate in the way of the outcome it is seeking. Even though we are moving from a state of no-peace, which is hopefully unsustainable. In other words the effort could be be defined as "safely and confidently accelerating the maximum point of unsustainability of the no-peace state such that it inevitably transitions to a sustainable state of peace".

That's then possibly a private endeavor (not that it could not be a public one as well, but you need to raise enough money to pay for the possibly expensive marketing and then pay all of its employees), because there is now an identifiable market willing to pay some amount in exchange for obtaining the "product" of peace, which in other words just mean the modulation of humanity and its mindset in order for it to operate in such a way that it is always aligned to its own common good, or maximum known state of well-being, sustainably.

We already know that groups and individuals are not great at doing that, on average. So if an individual is not always able to operate towards its own good, or maybe some are but don't have access to the resources that would allow them to do so, how could then a group of individuals be able to do so? Unlikely.

And yes, exploring the universe and finding more about its mysteries and teaching humanity about them is a valid and great approach and a subset of all the possible approaches.

It is a subset because in order for an individual to be interested in knowing more about the mysteries of the universe, or consciousness and other topics, they have to have this mindset, well, set in the mind.

Therefore there are many more fronts that could be, and to many extents currently are, covered. So all I'm arguing here is we are not doing enough to reach the tipping point before possible big catastrophes happen, therefore we should do a lot more than what we're currently doing. There are many entity/company/organization models to explore that could benefit us in a spectrum of possibilities ranging from private to public.

Constructing a telescope on Mars would be a valuable investment when a permanent presence is based there.
I hope one day we'll construct a telescope that uses the Sun for gravitational lensing. I've seen this paper once that claimed you could use it to image surface of exoplanets directly with pretty high (for our current astronomy standards) resolution. I think it talked about this: https://en.wikipedia.org/wiki/FOCAL_(spacecraft).
Mars is smaller than Earth, so planet-wide radio interferometry would be a smaller "aperture" than possible on Earth. If you're talking about extending the telescope to include both Earth and Mars, I imagine that doing the interferometry over changing speeds and distances would be challenging to say the least.
The speeds and distances of the planets are well known at this point and easily predicted. By the time of establishing a permanent presence on Mars the requirements of communications would already put in place the information needed if the DSN isn't already capable of it now. The compute needed would be greater, but so would the availability of it in the future too.
The papers with the scientific details are here (open access):

https://iopscience.iop.org/journal/2041-8205/page/Focus_on_E...

Article in physics world with comparisons to simulations:

https://physicsworld.com/a/first-images-of-a-black-hole-unve...

Article in physicsworld with comparison to simulations:
From reddit:

>"Hi, regarding the image itself: What I don't understand is why does it look like a donut and not a bright sphere? Assuming the black hole is actually spherical and not disc shaped, I would expect the Halo to be spherical and surrounding the black hole? so all we would see would be the ball of bright gas, even though there is a black hole in the middle?"

This is also what I would have expected.

The same reason planetary rings, solar systems, and (spiral) galaxies are flat: friction and conservation of angular momentum. Internal drag forces will eventually cancel out velocity components perpendicular to the plane of rotation, turning a cloud into a flat plane.
Things don't simply form a halo around a black hole. Instead you get a relatively flat accretion disk of things that orbit around the black hole.
This was a great explanation:
Material can come in towards the black hole from any angle. However, because matter can't just pass through other matter, matter travelling in the wrong directions will collide more frequently than matter travelling in the right direction. Because of the conservation of angular momentum, the "right" direction will depend on the average angular momentum of everything in the cloud that is collapsing into the disk.

You might be interested to know that this is the same reason all the planets in our solar system orbit in the same disk: all the matter that is now in our solar system was originally a very thin cloud of gas with a small amount of overall angular momentum. As gravity drew it together it flattended out into a disk and eventually the clumps became planets (and the sun in the middle.)

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 feed images of what we "think" a black hole should look like and use algorithms to compare the captured data with those images.

She then goes into explaining the measure they take to keep the resulting image from being biased by passing environmental images and images of other astronomical anomaly to make sure that those images return similar results.

But I can't for the life of me figure out how passing non-stellar imagery could return something similar. And if it does, why do we need to feed it an example of what we think it should look like at all?

Yes, at ~6:53 in the video she shows how they are selecting images to include that look like a black hole. If you plug in enough noisy images you will eventually get a few that look like a bright donut.
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.
(I haven't watched the video, but I do have professional expertise on this topic.)

With interferometry, you're getting an incomplete sampling of the Fourier transform of the sky image, and if you just invert the samples, you get what we call a "dirty" image.

But you know your sampling of the Fourier plane exactly, since that's just a function of the projected baselines between every pair of telescopes during the observation, so you can create a "dirty beam" - now all you have to do is remove the effects of the dirty beam from the dirty image. Of course, that's a deconvolution problem, and given that you don't have all the information - you sampled it - it can never be exact.

But it can be very good! There are very sophisticated radio synthesis image deconvolution algorithms, including CLEAN and Maximum Entropy. For Maximum Entropy methods, you can apply a Bayesian prior on your images - most of the time, the prior we apply is a blank sky (seriously!) but if we have other constraints that we can use (e.g., the approximate size of the region with extended emission), Bayes tells us that we would be remiss not to use it.

If you look at this image [1] from Paper IV [2], we show the image results from different techniques on different observing days. Those are the inputs to what is the "consensus image" - you can check how close they all are to each other.

Does that make sense...?

This 9 min video [0] does an excellent job explaining what we are looking at.
The US unveiling is WAY better than the EU unveiling that is linked to above. They have images, animations and graphs that's easily understandable by the layperson, and it's scientists instead of politicians speaking.

They talk about how the image was produced, and how they made such a small image out of the 5 PetaByte of data they gathered from stations all over the world.

I really really liked this press conference, I highly recommend it, well worth the watch. It's fairly short (~30m for the main part) and they explain the process step by step: how it was captured -> how it was processed -> what it means.

It's very well communicated in a way most can understand, it's concise and it has great accompanying graphics.

Thanks. Commissioners aren't even proper politicians : they get to power without election, without ever needing to convince the public, most often without even being known from the public. Nevertheless the decisions they make must be implemented in national laws by elected MPs. Hence you can imagine how despised and hated they are.
Yeah, no kidding. The presentation in the American conference is much more insightful and gives a stronger perspective. And the EU conference didn't even show the image until 8 minutes in.
One of the cool things about this was that the data was too large to ship over the internet (in a reasonable amount of time). They actually shipped physical disks full of data.

Even today, never underestimate the bandwidth of a station wagon full of disks...

r721
"This is more realistic of the uncertainties involved in this high-end image reconstruction. Still amazing though! Fig. 4 in https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85 "
Yeah, apparently radio interferometry is still very manual and so involves many relatively subjective decisions to produce an image.

That's probably why they had several analysers that they then combined into progressively larger teams until they could produce this Consensus-A picture.

There is non-manual ways to do it (called self-calibrating), but those need many more antennas. (What you really need is good coverage of the (u,v) plane AND many more different baselines between pairs of telescopes than the number of individual antennas.) If you do not have that self-calibration fails and leads to horrible image artifact or does not converge at all. They limited the influence of the manual calibration by observing a Quasar which is basically a point source between subsequent observations of M87* to get an independent amplitude calibration.
Some quasar other than M87 I suppose :P

(It is a quasar, simbad says so and that's good enough for this setting!)

Yes. They used 3C 279 which is more than 100 times further away than M87.
For those wondering how the image was constructed: https://www.youtube.com/watch?v=hMsNd1W_lmE

Basically, the image has been constructed by calculations on massive measurement data-sets from multiple synchronized telescopes around the world.

So this isn't a "photo" in the normal sense. It's a reconstruction of many, many radio waves.

It doesn't sound like they just snapped a picture. The one guy says they used "supercomputers" for 6 months to get the image.

Sunspots look black relative to the rest of the sun but are actually very bright. Could this be the same thing? How did they set the black level? Is there a description of the procedure somewhere?

EDIT:

Found the paper describing the data processing: https://iopscience.iop.org/article/10.3847/2041-8213/ab0c57

Indeed, from what I gather from this thread and external links this “image” seems to be more of a plot than an image. In fact, are we looking at a matplotlib plot of the data with a “hot” colormap? The iopscience paper even references matplotlib. I’m just making some educated guesses here, but it’s still fun to think about. BTW: Python for the win! iopscience paper makes several references to Python tools (e.g., numpy, Jupyter etc.)
Another interesting thing about that iopscience paper is that you can turn MathJax on/off with a link at the top. Mathjax is off by default, but when you turn it on, you get a nicely rendered equation instead of a gif image.
Every image is a plot... This one just has had a bit more processing gone into it than your average demosaiced and noise reduced vacation photo.
Summary of their summary:

“arising from the rapid atmospheric phase fluctuations, wide recording bandwidth, and highly heterogeneous array”

As far as I know K. Bouman [0] was the scientist leading the charge on the image processing/reconstruction. A few of her later papers probably have hints [1, 2] about how this is done, but I haven't seen the official release.
The project's director was Shep Doeleman
Thanks, I think I added the link to the paper while you were writing this. From skimming it I can't tell the answer to my question though.

How do they know what appears "black" in the image is really black vs. relatively black?

If you observe a very wide band of light (e.g., EM radiation) and there is nothing received from those spots, then, for all intents and purposes, the region of that image is black.

Now, if you're asking if, perhaps, the region isn't really black, but rather it's emitting some sort of small radiation relative to the bright region, it would be essentially impossible to know without much higher resolving powers (since it might even be indistinguishable from the background noise generated by the surrounding region). There is no way to really know if it's "perfectly black" vs. "orders of magnitude darker than the surrounding regions."

Makes sense. So I guess they could probably tell us an upper bound on how bright it is.
Indeed! That’s for sure: it’s probably not hard to extract a bound on the magnitude of a part of the spectrum from this analysis.
Any idea how bright it might be? Eg, could it be as bright as the sun? The moon?
I don't get the whole "oh it's too blurry and nothing is visible" comments. It's a black hole, what did you expect to see? Interstellar CGI?
It is a letdown. Although I wasn't expecting Jupiter level detail this pic doesn't blow me away because it's just a blurry ring. Jupiter level detail will blow me away.
Consider yourself lucky that a black hole isn't Jupiter level distance from us.
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At a jupiter level distance we'd be well within the event horizon. At that distance I expect to see four dimensional book cases and my daughter.
Jupiter level quality would mean that we are so close that we would be instantly torn apart.
Jupiter level quality is what I want. Not jupiter level distance.
The significance of the image is not in its quality, but in its mere existence.

It's enough to confirm various predictions, and should give a new baseline for truth about black holes.

Yes, we're using a telescope the size of the Earth to look at an object the size of our solar system in a galaxy about 55 million light years away. It's an infinitesimally small patch of sky.

On the other hand, the jet from the M87 black hole is quite large and we have good images of it. It's even resolvable by amateurs, I hope to take a picture of it over Easter with a small telescope.

> 55 million light years

didn't he correct himself and said kilometers

MR4D
He corrected himself to say 500 billion billion kilometers after mistakingly saying light years.

I haven't done the math, but I believe that roughly equates to 55 million light years.

55 million light years is about correct. Wikipedia still has 53.5 ± 1.63 Mly from older observations, but appendix I in paper https://iopscience.iop.org/article/10.3847/2041-8213/ab1141 has a bit more on the distance measurements they used. They arrive at 16.76 ± 0.75 Mpc, which translates into 54.7 ± 2.4 Mly.
It's just a stupid collection of small pixels but somehow it feels very overwhelming looking at it for the first time.

What a time to be alive

I mean, in the end, everything that you're looking at is just a collection of cones and rods in your retina. It's the information that it conveys that really matters.
Because that collection of pixels is really out there
Excellent example of successful international collaboration, with distributed team. Great results and promising future work: they say Sagitarius-A* is their next target!
Todays' Veritasium video had a shot of SgtA. Didn't know they did that.

Did some more digging and cant find the image in that video anywhere, lol. The M87 shot looks better, but still.

The telescope's announcement is up, too: https://eventhorizontelescope.org/
The EU is finally learning from the US when it comes making a lot of fanfare for discoveries and other inventions.
Why is the European Commission doing this? When I recognized Carlos Moedas I immediately skipped to what mattered. The reason why he was ever appointed as Commissioner for Research, Science and Innovation is, to me, more remote than the black hole about which he knows absolutely nothing.
because it's one Commissioner per member state, and apparently nationality is the most important criteria for appointing ministers
Well this was mostly a US-run effort. It's headed by Harvard University and the key South Pole Telescope is North American.
Too bad they don't present it well. I just see self congratulating politicians and officials on some youtube stream.

Telling that it's a US organization that hosts the actual picture.

esa.int and eso.org seem to be down actually.

Both ESO and the NFS hosts the images, don't know what gave you any other impression.

And while the EC stream was pretty bad, at least they let you skip back in the stream and left it up after the presentation ended. The NFS stream wouldn't allow you to go back (useful if you joined late) while it was up.

Personally I liked the ALMA stream best, but it's down now :(

https://eventhorizontelescope.org/ is hosted in the US and the linked image links to a Harvard.edu web server.
The European broadcast presentation is not great.

The speakers are referencing images and diagrams that are not visible on screen.

The accomplishment speaks for itself. The delivery can be improved.

So is a black hole 3 dimensional? Is it a sphere? Or does it only work in certain directions? Does everything "fall" the same direction?

I ask because even in a brief history of time, the diagrams are very "single plane of space-time, pulled infinitely deep by the black hole"

1. Yes, but it's also up for debate, since it's also known that the information content of a black hole is proportional to its surface area, so 2D.

2. The event horizon is spherical. Mathematically we treat it as a point. Nobody knows.

3. It's a gravity well, so everything falls towards it like it does towards the earth. Since it's the center of a galaxy, and galaxies form a 2D spin plane, most matter will be circling it, like our solar system circling the sun, so most matter will come from that planar distribution.

We will never see anything fall into a black hole, as in our space-time, this would happen at infinite time. As things get closer, they red shift from our frame of reference due to time dilation, until the light frequencies are so low that we can no longer detect them

Hmm, interesting. I'm curious why this is getting down voted.
beat
Is an image of a sphere printed on paper three dimensional? Think about that for a moment, and you'll see the problem.

I am not a physicist, but from my lay understanding, a black hole (and all other forms of matter) exists in a four-dimensional space-time form that we can experience directly, plus a number of higher dimensions that we can only extrapolate, and observe indirectly via experiment (kind of how a picture of a sphere is not a sphere due to a missing dimension, but you can still tell it's a sphere based on other characteristics). The exact number of higher dimensions is the realm of string theory, and could be 10, 11, 26, or something else.

The singularity of the black hole is one-dimensional, I think (I could be wrong, I'm often wrong). The event horizon is... funny. The outside of the event horizon is in four-dimensional space-time and is more or less "spherical". The inside is a land of theory and debate, because by definition we can't directly observe it from our space-time. Do space and time even exist inside the event horizon? I dunno, ask someone who knows what they're talking about. The best I can do is an analogy. Imagine it's the surface of the ocean. Above the surface, you're in air. Below the surface, you're in water.

The stretchy sheet of space time illustration is just a simplified visualization space is 3 dimensional so the warping is 3D. The stretchy sheet visual is used a lot because showing a warped 3D grid to be more accurate is a lot harder and a lot less clear and illustrative. Trying to show a 3D grid doesn't even fully capture the situation because it doesn't show how the passage of time gets distorted as well.
Let's start a movement similar to flat Earth, but instead it's Spherical Black Hole. I refuse to believe that a black hole is anything but a sphere no matter what evidence I'm shown.
> is a black hole 3 dimensional? Is it a sphere?

The event horizon is, to our understanding, roughly spherical when viewed from the outside. We don't know what happens inside.

1. Yes 2. Basically 3. No 4. No
A black hole itself (the singularity) is 1 dimensional - a single infinitesimal point. The event horizon around it is roughly a sphere. The diagrams that you are talking about are a visual metaphor that represent 3D space as a 2D plane and the 3rd dimension standing in for the influence of gravity. IRL, spacetime has 3 spatial dimensions, not 2, and gravity is not a dimension but a force. It's hard to visually represent gravitational distortion of 3 dimensional space without a 4th spatial dimension to do it with, so textbook diagrams use a 2D plane.
I think you've got a typo here: points should be 0-dimensional.
Are you sure it's a typo?

https://physics.stackexchange.com/a/194947

(I'm not a physicist.)

Not sure why you're getting downvoted, this is a legitimate question. However, in this particular case, I think the final sentence of the accepted answer on Physics.SE, namely that

> In this diagram the singularity is a line in spacetime i.e. a one dimensional object in spacetime.

is wrong or at least very misleading – the answer does (correctly) say that asking for the "dimensionality of a singularity […] is a meaningless question because the spacetime geometry is undefined at a singularity".

I believe the previous poster is referring to a typo following from this:

>A black hole itself (the singularity) is 1 dimensional - a single infinitesimal point.

In Euclidean geometry,

A cube is 3 dimensions.

A plane is 2 dimensions.

A line is 1 dimension.

A point is ...

A point is 0-dimensional, but in a space-time diagram the time dimension is added, which makes it 1-dimensional. Penrose diagrams for black holes assume spherical symmetry, so all of space is represented by a single radial coordinate, which makes it possible to display such diagrams in 1+1=2 dimensions.
A singularity doesn't have a dimension. It is a portion of spacetime that is missing, not a point or set of points. We can't define its dimensionality, either.(×) What we can say is that the singularity in Schwarzschild black holes is spacelike.

×) Counterexample: Consider the manifold M := R³\B, where B is the closed unit ball, equipped with the standard Euclidean metric. This manifold is certainly not Cauchy-complete and we can reach the singularity at r=1 in finite time. Now, if we had to define the dimension of the singularity, what dimension n should it have? n=2 (a sphere)? Maybe. At least we could extend M by the unit sphere to make it complete. But could the singularity also be a point (i.e. n=1)? Yes, certainly. By diffeomorphism invariance, we could simply find new coordinates and map R³\B to R³\{0}, so the singularity would suddenly become a point. So, as you can see, interpreting the singularity as a point or set of points that have a topological dimension doesn't work.

> A black hole itself (the singularity) is 1 dimensional - a single infinitesimal point.

A point is 0-dimensional. A line is 1-dimensional.

The singularity is 1-dimensional (more precisely, a ring) if the black hole is rotating. [1]

The singularity is likely a mathematical artifact of the fact that GR is insufficient to describe black holes. In reality (quantum gravity) they probably do not exist.
I would not be so sure. Its presence might simply indicate, that black hole's inner volume is infinite.
Could you elaborate on your definition of volume here (are you talking about spatial volume or spacetime volume?) and how the curvature going to infinity at the singularity should imply its infiniteness?

My thought process here is the following: The inside of an (eternal) black hole carries four (Schwarzschild) coordinates t, r, theta, phi – r now being timelike and confined to the interval (0, 2M) and t now being spacelike and being any real number. That is, depending on when (at what time t) you cross the event horizon, you end up at a different point in space. The singularity at r=0 is then a point in your future which, like your own death, you cannot actually see but which you will nevertheless hit in finite proper time.

So in this sense I'd say the volume is very finite (if we disregard the (trivially unbounded) spacelike coordinate t which, as mentioned before, simply corresponds to the time of entering the BH).

1. In the interior of the BH, the determinant of the metric is bounded since the Schwarzschild factors in the metric cancel out. So the volume measure doesn't do anything crazy as one gets closer to the singularity and boundedness of coordinates implies boundedness of the volume. Again, I'm disregarding the spacelike t coordinate because to me the relevant fact is that all matter reaches the singularity in finite proper time, so while we could theoretically stack lots of (actually, an infinite amount of) (massless) cubes inside a black hole, they would soon all get crushed.

2. Of course the situation is slightly different if we're talking about a growing black hole whose mass (and, therefore, radius) increases as we throw matter into it.

Unfortunately, I am not strong on mathematical part of GR, so feel free to disregard the rest of this idea, if math's the sole thing you are looking for.

A thought experiment: imagine we have a clock, falling into Schwarzschild black hole. Obviously, any real clock would have some non-zero size in all space dimensions. Here we will be concerned with just two: r and any orthogonal one. So for simplicity let the clock be a simple rubber-like oscillating ring with a fixed k and infinite resistance to tearing. (You could also take infinite k, but I'd argue that would not be physically meaningful in this setup)

As the ring is closing to the r = 0, its oscillations will slow down and come to a halt due to physical stretching along the r dimension. What I am trying to say is that maybe these oscillations make more sense as the measure of time for the ring people, than what a numerical value of proper time tells us. In a similar way the time singularity at the horizon is nothing special for a freely falling observer.

I am unsure how to interpret the fact, that the number of oscillations per proper time unit is going down though. Seems to be quite the opposite of my original note about the volume, yet something is ringing.

Unfortunately can't reply to the original question anymore. But here's another hypothesis I just read elsewhere (RU: https://don-beaver.livejournal.com/212422.html): the matter-energy falling towards "center" inevitably has some non-zero momentum, orthogonal to the direction along r. That means its fall is going to be (sort of) spiral, causing it to produce gravitational waves. The argument here is that the whole mass will be converted into gravitational waves before reaching the central point. Now what happens to those waves is a question still.
So much higher res than I thought (I was expecting a 3x3px black and white).

Does anyone know if this is aggregated over a long time so it's unlikely to improve with more observation? And what is limiting the resolution at this point?

One thing missing from @petschge's reply: adding more telescopes! This will not improve the imaging the smallest possible features, but will make features larger (disk and / or jet components) more prominent. The more telescope pairs with different distance between them are added, the more complete the picture will get - up to a limit of having a single antenna roughly the size of Earth.

Furthermore, adding more telescopes will help better image the fainter features in the image (due to larger total collecting surface).

Very good point. I was too much focused on resolution. Adding more telescopes would indeed give a better picture of large structures (most are cropped out of the current view because they are not well imaged and you would mostly see artifacts from the image reconstruction) and improve dynamic range, i.e. allow to see things much fainter than the brightest spot in the image.
The limit in some sense is the size of the Earth. This picture is from an interferometer observing at very high radio frequencies (wavelength of 1.3 mm) using telescope around the Earth. To improve resolution you would either have to go to even higher frequencies (we have a very hard time doing interferometry there) or find baselines larger than what fits on Earth. And you don't just need a long baseline, but need to keep the baseline constant to within a fraction of the wavelength. So if you want to use satellites to get longer baselines you would have to know their orbit to within a tenth of a millimeter.

As an aside: that image is basically black and white. The intensity is just mapped to black -> orange -> white instead of black -> gray -> white.

I wonder how important time is in collecting these data? Because if 6 months isn’t an issue, then the array size could be expanded in one axis to the diameter of Earth’s orbit around the sun, no?
The collecting time is important, but mainly to 1) sample the rotation of the Earth in the Fourier space for better angular resolution and 2) for raising your overall signal-to-noise ratio is the image (but the one released is already pretty good, so not much improvement can be done there unless you're trying to go for the faint features in the image).

Unfortunately, you can only do interferometry with simultaneous measurements (we need information about the difference in the phase of light hitting the receiving antennas), so the motion of Earth around the Sun is largely irrelevant, unless you can park another antenna at a trailing orbit (see space VLBI for that).

What you're thinking of is probably parallax measurements of distance - that's how missions like Gaia can pinpoint distances to stars in Milky Way (and some in its satellites as well).

Thanks.

We seem to need a big radiotelescope on the moon then? That should give simultaneous measurement on a much larger baseline?

I doesn't even need to be that big. A 60 meter dish would do nicely.

Problem is, you would want to have several Gigahertz of (radio) bandwidth. You are not going to down link that raw, but rather as a number of channels, integrated over a number of microseconds and digitized at something between 4 and 64 samples per bit, but we are still talking a down link data rate of gigabits per second.

Is this what we would see with the naked eye if we were close enough to the black hole? Or would we see nothing, because at this distance we would be dead (or the universe ended all around us)?
This image is a representation of radio observations. What we would see in the visible part of the spectrum would be different but the structure would likely be similar.
You'd probably be dead from the radiation (that light peaks in the x-ray wavelengths) long before any of the spatial distortion effects got to you.
regular orbits around black holes are possible. Depending on activity if it's far enough away the radiation should be survivable, it just depends on how much matter it's eating up and whether the orbit is planar enough to its spin (otherwise its jets can be deadly).
These obs are in radio. We could replace your eyes with radio eyes... ..but it's friction heating so it ought to be broadly blackbody, so I would say yes.
e0m
"This is like viewing a mustard seed in Washington DC from Brussels"
Pedantic/fun comment: I will assume that one of the presenters said that (I will watch the full video later tonight). One would imagine that that person knows that you cannot see a mustard seed from Brussels because the planet's crust is blocking your line of sight ;) unless the scientist who said that is a flat-earth-believer!

A statement like "it is like viewing a mustard seed X kilometres/miles away would be more appropriate.

And in all seriousness, I have started watching again everything-Star-Trek again (for the 5th time in my life), and news like that make me look up to the sky and think that as a species we do have a chance to move out of here and to a better future.

for what it's worth, with an active sensor (not a camera) you can see over the horizon.
Such a photon-centric perspective. Why don't you use your neutrino perceptors to look at the seed?
Why did they choose this very distant galaxy? why not something that's close to us like the andromeda galaxy or even the center of our own galaxy?
They did. M87* was the widely publicised "first" photo, but they also got images of Sagittarius A* (the supermassive black hole at the center of our galaxy).

The difficulties with Sgr A* are twofold:

- The black hole moves too much during an observation (because it's much closer, and parallax is a thing)

- Sgr A* is much smaller than M87* by mass, so even though it's much closer, the angular diameter is almost the same, and the accretion disk is dimmer.

As I understand it, by being more massive this black hole has roughly the same angular size in the sky as Sag A* at the center of our galaxy, but none of the dusty foreground in the way so we get a clearer vantage point.
Does anyone remember Interstellar. Their black hole simulation was based on hard science. Looks fairly similar
Interstellar is one of my favorite movies in recent memory. If anybody else is interested in reading more, the book "The Science of Interstellar" is fascinating and very easily digestible even if you're not big on physics.
just had my wife watch it and yea, that was the first thing I noticed, they really did a good job on the science of interstellar.

When interstellar came out wired did a full magazine spread on the movie, covering its science, how they came up with the story and what the director did to make sure it was believable. idk what it looks like online but I've kept the magazine.

this presentation by kip thorne is very detailed about the science behind the movie. it's one of the best presentations i have seen, and i have watched it multiple times.
The visualization I liked the best in Interstellar was that of the wormhole, seen from the outside. (The "travel" through it was rubbish.)

The thing would look like a mirror sphere, floating in the middle of space, reflecting the space around you. Except it would be the space on the other side of the wormhole, not that behind you, and the motion of the "mirrored" image would be opposite of that on a real mirror. (The apparent image on the wormhole's spherical surface would appear to move in your same direction, as you're moving around it, not in the opposite direction as it does on a spherical mirror.)

It took me a while to reason about it and figure out that it was indeed what a wormhole would look like, if we could find or create one.

Relevant paper: https://aapt.scitation.org/doi/pdf/10.1119/1.4916949?class=p...
It doesn't look anything like Gargantua in Interstellar, but it's not really supposed to, except for the most prominent features. Interstellar showed what a black hole might look like in visible light while in orbit around it. This is a radio telescope image from a far away galaxy.
Interstellar also turned off the doppler effect, maybe to get a boring symmetric ring instead of an awesome asymmetric one as nature intended it to be!
IIRC, the black hole in Interstellar was also rapidly rotating, which I think was significant to how it looked:

https://www.wired.com/2014/10/astrophysics-interstellar-blac...

> Nolan's story relied on time dilation: time passing at different rates for different characters. To make this scientifically plausible, Thorne told him, he'd need a massive black hole—in the movie it's called Gargantua—spinning at nearly the speed of light.

> ...

> Von Tunzelmann tried a tricky demo. She generated a flat, multicolored ring—a stand-in for the accretion disk—and positioned it around their spinning black hole. Something very, very weird happened. “We found that warping space around the black hole also warps the accretion disk,” Franklin says. “So rather than looking like Saturn's rings around a black sphere, the light creates this extraordinary halo.”

Sure, the BH spin affects the photon orbits somewhat. But the effect of the rotation of the accretion disk itself is completely neglected despite being one of the mayor effects.
I'm still wondering why the accretion disk from the released images isn't warped in a way we saw in interstellar. Are we looking at it top-down rather than from its orbital disk? would a differently oriented black hole look more like interstellar? Veritasium also has an explanation and I don't think it has anything to do with its spin.
Intersterllar chose to view the disk edge on, when the distortions got the most funky at all.
I think the rotation from M87 is 15 degrees off from our perspective, so yes we are looking mostly "down" at it.
just for people's reference, here is the more realistic picture: https://cdn.iopscience.com/images/0264-9381/32/6/065001/Full...

i really feel they should have keep the more realistic one and dialed it up a bit. the more whispy distortions are much more awe-inspiring than the symmetrical, oversaturated version.

the source paper: https://iopscience.iop.org/article/10.1088/0264-9381/32/6/06...

Is black hole a 3D object like a sun? If so, I assume the light in the event horizon cover the whole object, i mean 3D shaped as well. How the picture taken from the telescope shown the dark area where the black hole is located? I mean, shouldn’t the whole black hole covered by the light thus we can’t see the black hole?
I think the 'glow' around the black hole you are thinking about is a light that was bent by gravity but hasn't gotten to event horizon.
It almost looks like a sun eclipse.
The black hole itself is spherical, but the light we're seeing around it isn't projected by the event horizon; rather, it's light from behind/around the black hole that isn't blocked. This video explains in much more detail: https://www.youtube.com/watch?v=zUyH3XhpLTo
But if it's spherical, should not the light be all around it?
The light is emitted from an accretion disk, which does not envelope the entire sphere.
Actually, this particular black hole is (probably) not exactly spherically symmetric but only axisymmetric since it is rotating (i.e. it is a so-called Kerr black hole). But disregard the lack of spherical symmetry for a moment (it can still be approximated quite well by a sphere for our purposes, see below), the crucial points are the following:

1. Along with its rotation comes the fact that the black hole drags the surrounding spacetime along with it (whatever this means), including matter. So matter near such a Kerr black hole will start orbiting it automatically. Closely related(×) to this is the fact that, in the close vicinity of a black hole, you typically find a so-called accretion disk of matter that is orbiting the black hole and slowly being eaten by it, while also emitting light because the infalling matter is heating up in the process. Now, the important point is that the disk is really a disk, though(!), meaning that it doesn't completely surround the black hole in all directions, so there are (lots of) angles from which you could actually "look at" the black hole and your view would not be (entirely) blocked by the matter (and the light it emits). I hope this answers your question as to whether the light "should not […] be all around it".

2. In the case of M87 it seems like the axis of rotation is pretty much parallel to our line of sight, meaning that we're actually looking at the black hole "from above" and that our line of sight is pretty much perpendicular to the accretion disk surrounding the hole. In particular, this means we get to see the accretion disk and the black hole's "bald head" in their full glory. Moreover, since we're looking at the black hole "from above", its slight deviation from spherical symmetry doesn't matter and it still looks like a disk to us due to its rotational symmetry in the direction in which it rotates. (Think of how a cylinder looks like a disk/sphere from above.)

(×) To be precise, infalling matter often carries angular momentum (as measured with respect to the black hole's location), i.e. it doesn't fall into the black hole exactly radially but rather sideways, possibly after having orbited the black hole multiple times. This means that when it finally gets absorbed by the black hole, the latter will absorb the matter's angular momentum, too, and start spinning.(××) So the rotation of the black hole, on the one hand, and of the matter outside, on the other hand, are tightly coupled phenomena and disentangling what came first is a "chicken or egg" kind of problem.

(××) Side note: Infalling matter transferring angular momentum to a black hole is the reason why we expect most, if not all black holes in nature to carry angular momentum, i.e. to be of the (axisymmetric) Kerr type instead of the simpler (non-rotating and perfectly spherically symmetric) Schwarzschild type.

If it were emitting the light, yes, but it's not. It's more complicated than this, but imagine holding a black sphere in front of a light bulb. You'll see a ring of light around the sphere.

Somewhat separately, there's the accretion disk, which again is a disk not a sphere, much like other orbiting systems like solar systems or galaxies−the gravity between bodies orbiting the same central gravity source causes them to arrange roughly into a plane, rather than all having their own unrelated orbits. We're not seeing the accretion disk directly though, but rather the light from it, and from other sources, that is able to pass around the black hole. (ie the black sphere in front of the light bulb.)

Watch that video; it explains it in a very approachable way.

How big a VLBI baseline would they need to see much more detail? Are there any plans for a space based VLBI; not easy when you consider the utterly huge amounts of information they have to transfer, a radio telescope in a L5 would be a start.

Also I'd be interested to read how they got around scintallation of the Interstellar Medium.

Space VLBI is a thing already! Seems to have been around for a while [0][1]. I imagine that the challenge with during EHT-style VLBI in space is downlink bandwidth... there's just no way to get the petabytes of data they talk about down from a satellite. It's already so much data that it's easier to fly hard drives around the world than to send it over the internet, so the transfer would probably take ages over a microwave link. Maybe with laser communication in the near future but even then... it's a lot of data.

Resolution-wise, the angular resolution is inversely proportional to the farthest baseline, as given by the Rayleigh criterion. [2] To get twice the resolution, you "just" need to double the size of your baseline (and do that in both dimensions, otherwise the angular resolution will be different in x & y). We've maxed out the Earth's baseline, so it seems like orbital radio telescopes are the only way to better resolution. Pretty exciting!

> We've maxed out the Earth's baseline, so it seems like orbital radio telescopes are the only way to better resolution.

Going to higher frequency gives you higher resolution for a given physical baseline length.

For some observations, they've used the earth's moving position in space to create a synthetic-radar style image. That gives an 'aperture' of 180M miles.
> For some observations, they've used the earth's moving position in space to create a synthetic-radar style image. That gives an 'aperture' of 180M miles.

That may not work for imaging the immediate surroundings of black holes – one can only combine the data for that SAR-style imaging if the source you're observing doesn't vary significantly (e.g., in brightness or flux distribution) between observations.

> I imagine that the challenge with during EHT-style VLBI in space is downlink bandwidth... there's just no way to get the petabytes of data they talk about down from a satellite.

Why do you say that? The latest High Throughput commercial satellites do 500Gpbs downlink throughput, so shouldn't the transfer time for a petabyte of data be reasonable?

Of course those satellites are configured to transmit data all over the earth, so the technology would have to be used differently for this application.

>> Also I'd be interested to read how they got around scintallation of the Interstellar Medium.

One of the reasons they've imaged M87* rather than a black hole in our own galaxy was to avoid dealing with ISM scattering - we don't have to look through our edge-on disk, so it's easier to image another galaxy's center somehow. But the Sgr A* image might be in the works already, it was mentioned in both the press-conference and one of the paper's future work section.

How does one even deal with ISM scattering?

The optical equivalent can be dealt with by active optics, or picking frames with best seeing, but for ISM I imagine it is a fair bit different.

pps
> Are there any plans for a space based VLBI; not easy when you consider the utterly huge amounts of information they have to transfer, a radio telescope in a L5 would be a start.

There is space-based VLBI at lower radio frequencies, with the "Radio Astron" project[0]. That effort works at frequencies which are roughly a factor of ~10 lower than that of the EHT. I'm not aware of any plans for millimeter Space VLBI, but the higher frequency would require higher data rates.

Katie Bouman herself did a fascinating Ted Talk behind the effort involved for creating the first image of a black hole:
So we got an image of one in a far away galaxy before the one in the center of our own galaxy!
Is this due to occlusion?
A lot of the problems with imaging the black hole at the center of the milkway is that we would have to look along the midplane of the galaxy towards the center. That is where a lot of gas and dust is to be found and the radio waves interact with that stuff. They did take data and are working on it, but the image of M87* was easier to reconstruct and went out first.
Event horizon telescope has been taking data of the Sag A* black hole but the data is still being processed and yet to be released.
Breakthrough discovery in astronomy: press conference
And the image itself:
Is this image lossy compressed by Twitter? Is there an official release?
Not really, that's just the level of detail available.
https://www.nsf.gov/news/special_reports/blackholes/formedia...
I always thought we have photographed black holes. Any idea/link to article where it explains why this took so long and why it was difficult?
Well, we have in the same sense that you take a picture of bacteria every time you take a selfie: there certainly are lots of pictures which contain black holes that are too small to be seen in them.

In line with that analogy, the basic difficulty is simply that they are tremendously small compared to the sizes of galaxies.

Here's an NY Times article about the project:

https://www.nytimes.com/2018/10/04/magazine/how-do-you-take-...

The author, Seth Fletcher, also wrote a book about it, "Einstein's Shadow: A Black Hole, a Band of Astronomers, and the Quest to See the Unseeable", if you want more details.

There have been plenty of indirect observations such as their jets, stars in very tight orbits around Sagittarius A*, xray binaries etc.

This is a direct observation of the immediate environment of a black hole, i.e. its accretion disk and other light bent around it.

yk
This is as far as I understand the first picture of a black hole shadow, that is the dark disc that indicates that there is actually light missing. Before that, there were astrophysical observations that strongly indicated that there is a black hole, for example QSOs, that is a bright combination of accretion disc and jet, that is powered by a black hole, or one paper I really liked tried to argue that there has to be a black hole in Cygni X1 because otherwise we would see the missing matter crashing into something. (Cygni X1 is a binary of a star and something very bright and the star is loosing mass.)
Because they're very small, very dark, and very distant, compared to visible objects like planets in our solar system, stars in our galaxy, and other galaxies.
Their website talks about some of the challenges of getting a picture of a black hole: https://eventhorizontelescope.org/home

All of the data used to generate the image was gathered by around a dozen different telescopes around the world. The black hole itself also needs to be in a specific configuration in order for us to be able to see it. It needs to have an accretion disk that's generating light. It needs to be sufficiently large or close. And it can't be obfuscated by other astronomical objects like stars or nebulae. This black hole itself is hugeeeeee and far. It's about the size of our solar system, but it's ~52 million light years away.

Does anybody noticed that there are two brighter areas (not just one) in bottom part of the image.

One at approx 8PM and one at approx 5-6PM (if seen as clock)

The image of the black hole is not sharp. Isn't it possible, that the optics at that distance may make "optical mistakes" and this is not a black hole after all but maybe just some circular lightning or some darker, but not black object before some star - like in solar eclipse?
The thought struck me that the interferometry technique used must have gathered data from a much wider field of view than of just the black hole.

Burried in that 5 petabytes of data is likely a scan of a much larger field of view at a similar resolution.

Yes. But since you have a bright spot in the center of the larger image and you only have a limited number of baseline between pairs of telescopes there will be all kinds of artefacts in the outer portion of that large image. So it get's cropped away. (Most of it is actually never even computed).
I still think it would be worth pursuing. I hope the raw data will be made available at some point... Not that I have 5 petabytes free space available right now...
Here it is: https://image.futurezone.at/images/cfs_932w/3398269/bild-ist...
Here's the image via a URL:

https://pbs.twimg.com/media/D3yzi3dX4AEnoEp.png

> Scientists have obtained the first image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun

So how come it's a ring of plasma that forms and not a sphere? Like we can see the hole unobstructed? Is it because gravity tends to clump things together? I guess Saturn's rings are the same?
Conservation of Angular momentum collapses shapely sort of things into a disk
Saturns ring, the flattening of the accretion disk, the fact that planet systems will have most planets more or less in one plane and that spiral galaxies are flat (much thinner than they are wide at least) all have the same reason, yes. Basically most orbits align due to initial orbital momentum and the stuff that orbits in other directions sooner or later experiences enough friction to be forced into the common orbital plane.
Here's an animated explanation of the process by the Event Horizon Telescope. https://youtu.be/hMsNd1W_lmE
ken
Misspeak? This video says it's 4 million times as massive as the sun, but today's press release and Wikipedia article about it both say it's 6.5 billion times as massive.
The black hole at the center of the milky way is 4 million times the mass of our sun, the one in the photograph is much more massive. Im guessing that is what they were referring to.
Let's say I were to jump into this black hole for fun. What happens to me? What are the chances I go somewhere cool, like another universe, versus getting turned into a spaghetti noodle?
Don't it's no fun you'll get space sickness trust me.
I understand this was done by coordinating multiple telescopes to create a virtual earth size scope. Why is this not done more? It seems like cloud services would make this relatively easy to share bits technically. Are the issues mostly political or are there tech issues making this harder to do more often? Tangential question: if we can do this with an earth-size virtual scope, what could we do with a larger one? Scopes on earth/moon/Lagrange points synced together.
It's been done since the 1970s.

https://en.wikipedia.org/wiki/Astronomical_interferometer

There are some proposals to do it in space.

So how can we make a planet sized synthetic aperture optical telescope?

I'm wondering if there is a way to do it with holograms (since they preserve phase information): take holograms of the object from opposite sides of the earth and then combine them offline. There are some papers in this direction:

https://hal.archives-ouvertes.fr/hal-00654840/document

(spy satellites probably already do it...)

Can we see nearest stars and planets using this method? Or is it only for radio sources?

One day we may even connect millions of smartphones to observe various interesting space phenomena.

On a tangent, interesting closing remarks from the commissioner on the importance of courage, dreams and science. Targeted towards the present anti-science climate.
Any word if Einstein's predictions are correct or refuted? There was word that if the shadow looked a certain way it could mean that relativity is incomplete.
USA Today is live streaming a presentation about this from the National Science Foundation and they seem to be taking the point of view that Einstein's theory of general relativity has held up SO FAR. There is still quite a bit of research to do on the image / data which means the theory could be further proven or disproven.
General relativity predicted the event horizon, but it breaks down when trying to predict what is going on in the center, as all equations go to infinity, which is likely to be more a problem with our current understanding than what is actually happening.
I wonder if this is a call for another level of math. Are we just not able to take the derivative of something in respect to space time rather than just time?
Pretty much exactly what was predicted as to the livestream :-)
A Bloomberg journalist at the press conference asked this question and the researchers didn't really commit to an answer.
In the discussions they said that it appeared entirely consistent with GR. Presumably more specific analysis is in papers coming afterwards.
Are there any papers already out which focus on the technical aspect of reconstructing the image? I heard that they analyzed 3.5 Petabytes of data for this.
5 PB. The American unveiling focus on just what you talk about: https://www.youtube.com/watch?v=2DxjuE7WDlk
Have a look at the papers listed at the bottom of https://iopscience.iop.org/journal/2041-8205/page/Focus_on_E... .

Keep in mind that a lot of the details will NOT be in those papers as they have used CASA and AIPS, two standard software tools that have been developed over more than a decade. Details are consequently scattered over many papers. Radio interferometry is not new and there is entire textbooks on the subject. The exiting bit here is not that we go a first image from interferometry but that we have a first image of the region just around a black hole.

Here's an article (and image) from the guardian: https://www.theguardian.com/science/2019/apr/10/black-hole-p...
Why there are two live events right now? One is from Europe, another from US:
There are 6. It's an international accomplishment.
If there's a God, He must be so incredibly proud of us. What we have accomplished as a species is just mind-blowing.
I wonder how it compares to the one from Interstellar?
This blog post describes the stuff Interstellar mostly gets right, and the big thing it's lacking (a brightness asymmetry from the rotation of the accretion disk).
Side note - there's a really neat write-up by someone who realistically rendered a rotating black hole in 1979, partly by computer and partly by hand [0]. He goes through all the important visual effects, like GR ray tracing, disk brightness, and Doppler shift. The final image is pretty cool.
If I recall this correctly, the movie intentionally simplified the rendering of the black hole (by eliminating the Doppler shift) to make it more visually appealing.

Pity, really. Then again, there were other things that made no sense in the movie...

NASA hq launching a rocket from the next door room, was my warning.

Danny Boyle was confident he had “done SciFi” with Sunshine, perhaps Christopher Nolan just wanted to tick that box too.

Where Kubrick led others followed; Ridley Scott was doing great to Bladerunner...

Since we're on it, there's actually a book about the science of interstellar.
The author (Thorne) was actually a producer for the movie, as well as a being a physics professor.
Google Cache because site got stomped with traffic
Even that page is not opening for me ...
I have a real problem with this..

they have not taken a picture of a black hole because that is not possible..

they have at best constructed an image of some effects of a black hole.

This is where top scientists do damage to science for ordinary people when they make fundamental errors in public statements.

Anyone else getting sick of the media calling this the first "PHOTOGRAPH" of a black hole? It's a spectrograph at best and more realistically a rendering. Don't get me wrong it's really cool but it's not a photo.
You are wrong, this is definitely a photo, shot by multiple telescopes global-wise.
Multiple radio telescopes right? Then the data was compiled and rendered into an image, you really think it's that bright? How about orange? I wonder why it's not symmetrical? I suppose you can take multiple images combine them into one, run it through a bunch of filters and call it a photo but I still think it's more of a rendering than a photo.
>an array of relatively large sensors with very high exposure looking at information from something very far away, and combining that data with a 'brightness' scale, instead of a 'colour' scale I like the sound of that far more than photograph, but I will relent, not worth getting into a slap fight over what constitutes a photograph...face palm
> Then the data was compiled and rendered into an image

A digital camera is just an array of tiny sensors that detect how much light hit them and a computer takes those values and renders an image from them.

> you really think it's that bright?

If you take a photo in a dark room with increased exposure then the resulting image is brighter than what you see with your own eyes. This was taken over a long period of time, effectively a long exposure. If you were close enough to see it at the scale you are seeing it on your computer screen it would probably be far brighter.

As mentioned in another comment on this thread, it's just the colour scheme used in the output to show the brightness differences. The accretion disk is not necessarily orange, this photo is essentially greyscale mapped to a black -> orange -> white scale.

This is just an array of relatively large sensors with very high exposure gathering information from something very far away and combining that data in greyscale.

> I wonder why it's not symmetrical?

See Veritasium's video [1] on why it looks like it does, in short, the effects of the black hole and our angle to the accretion disk.

Also relevant: How to take a picture of a black hole | Katie Bouman | TEDxBeaconStreet https://www.youtube.com/watch?v=P7n2rYt9wfU
it
If you want to jump directly to the image, here it is: https://www.youtube.com/watch?v=Dr20f19czeE&t=8m28s
Can the equipment used from several places on earth for this be deployed in space (may be to a geostationary orbit)? Not thinking about cost for a moment is this a far-fetched thought or such a thing is technically possible.
Yeah. There were a few NASA projects attempting to do this that got cancelled circa 2010 (programs called TPF-I and SIM).

Something that has been done for a while is using a single telescope in space in conjunction with some on Earth. Russia has a radio telescope in orbit called Spektr-R. I think it died recently, but Spektr-R did interferometry with other telescopes on Earth. When it was operational, I believe it was the widest VLBI array— its orbit was higher than GEO (and even intersected the moon's!), so it got pretty good distance from the ground.

Katie Bouman's 2017 TED video explaining how the image was taken https://www.youtube.com/watch?v=BIvezCVcsYs
Reminds me of this project (building a realistic blackhole raytracer) http://rantonels.github.io/starless
This is fantastic. But why did it take so long to prove the existence of blackholes ? are there any scientific breakthroughs that made it possible or it's more a technological achievement ?
To be clear, they detected the black hole because it looked like the way we expect a supermassive black hole to be? Or were there other hints that led to it being discovered where it was?
The Eye was rimmed with fire, but was itself glazed, yellow as a cat’s, watchful and intent, and the black slit of its pupil opened on a pit, a window into nothing.
There are people that can't believe the Earth is round... I can't imagine what "alternative explanation" will be made to explain a black hole...
From whatever videos I have watched I don't believe so called "flat earthers" really believe that the earth is flat. At most they seem to be trolls and just like to oppose whatever scientists say. So IMO nobody should waste time explaining anything to them.
781
? As you can obviously see in the image, the black hole is also flat.
That its a black circle?
Photoshop!
There is still zero evidence that there exists such a thing as a black hole with all its fantastic properties. We have a picture of a red-yellow accretion disk and that's it. Black holes remain a mathematical artifact of general relativity and there is as much evidence of their existence as of crystal healing and astral travel. There is at best some evidence of very massive objects at certain points.
How do you explain observed gravitational wave observed by LIGO? It is almost the same as the one calculated for coalescence of two black holes in GR.
It's still no proof of existence of black holes. It's like saying that a lightning storm is proof of Thor, because the legends say he wields the very same lightning. The cause could be something entirely different (spontaneous spacetime ripples, alien generators, whatever really).
General Relativity is based on familiar observations, not mythical beings. It's not nearly that complex. Crystal healing and astral travel likewise don't even have a mathematical basis that is compatible with observations about reality, so there's no comparison to draw.
> It's still no proof of existence of black holes

You've shifted the goal posts in this sentence. Previously, you said there was no evidence of black holes. Now you're upped the scale to demanding proof.

The previous commenter wasn't claiming that LIGO detections were proof of black holes. They said that they were evidence of black holes.

The LIGO detections, by all reasonable metrics, would certainly qualify as evidence of black holes. Of course, I agree with your assertion that taken alone, LIGO detections are not proof of the existence of black holes. Taken with the significant body of other evidence we have, though, I would say the sum total of evidence that we have is a strong indicator that black holes exist.

The fact that scientists were able to accurately predict what this black whole should look like using the math at our disposal is about as good a piece of evidence as one can get.
I think it's on par with the LIGO detections (which I think also qualify as really strong evidence) given the specificity of the predictions and how closely they aligned with the observed data.

Taken as a whole, the body of evidence is really strong and it's amazing how much stronger it's become in just the last few years!

This is truly an amazing image.

I think you're right, that they probably are a mathematical artifact of GR. Regardless, what they are in the real world will share quite a few properties with black holes.
This is what convinced me: https://www.youtube.com/watch?v=B0QRpid5_QU
beat
Likewise, we have zero evidence that there exists such a thing as atoms... if you only use direct evidence of the unaided sense, rather than indirect evidence.

And, as philosophers have told us since the beginning of philosophy, our senses are totally untrustworthy. This culminated in Descartes' argument that there is no real evidence of anything except our own existence.

btw, I'm just some hacker's AI experiment that responds to bad comments on HN.

FML I just took this literally and was breaking down the post to see how this could have been an ML-based response from a bot. Then I looked at the poster's other comments and realized I'm an idiot. :(
beat
We're all idiots, my friend. Remembering that is the hardest and most important work we can do.
Potentially none. They can just deny its existence and pretend this is a fabrication.
Pardon my naïveté, I never took advance physics, but if light can't escape from a blackhole, then how can we "take a picture" of one?
Same way we can take a picture of a shadow - by taking a picture of the stuff surrounding it. This black hole is surrounded by a bright accretion disk.
It's a photo of the absence of light (in the middle) and light/particles swirling around the black hole that haven't passed the event horizon (yet).
How come it so happens we are looking at the black part while the sides are bright? Does it look like a O from any angle of the sphere?
How jaded have I become that when I see four old men and one young person I automatically assume the younger one did all the work?
Now I'm really curious if Quantum Entanglement will work if you send one of the entangled particles into a black hole.
Is this a 2D slice of the actual spherical black hole?

Because if a black hole is a sphere, then shouldn't the whole thing be golden?

The black hole is warping spacetime around it in a severe fashion. The innermost (unstable) orbit is called the photon sphere, and light can make several orbits around the hole before either falling in, or going off to infinity. The result is that (depending on the hole’s rotation relative to your point of view) you’re going to see roughly the same image we have today. You’re actually going to see multiple images of the entire hole, stretched around the outer edge, and those images multiplied and distorted again. If you could somehow “stand” by the photon spehere you’d see the back of your own head many many times.

The other factor is that while the event horizon itself is a spheroid, the accretion disk of bright infalling material is not. The horizon is totally black, so it will always look roughly like seeing a disk face-on no matter where you look at it. The accretion disk is a “hoop” that’s stretched and the image is multiplied and distorted by the strong warping of spacetime in the region. As a result you get smeared and repeated views of the entire disk including portion behind the hole in a kind of bent band. Plus the whole thing is subject to strong Doppler beaming hence the bright and dark regions.

It's really amazing that human mind can predict and tell the things without even seeing it.

How come we even know and predicted the radius and things far away in galaxy without even seeing it. It's just amazing. Wow it just amazes you that scientist even have predicted the radius of thing and how it work etc.[1]

Numbers about measures and dimensions are mind blowing. You can find articles with more details.
This is so phenomenal. What an amazing and tremendous effort from that team!
The reveal happens at -27:06
This is one of the most beautiful photos I've ever seen. Fascinating.
Does this confirm or disapprove Steven Hawking Black-hole radiation?
The Hawking radiation for a black hole with this mass would be really small. It actually decreases with added mass. So, this observation does not say anything about Hawking radiation.
ajuc
Shouldn't it increase, just with square of the radius, so it's dwarfed by all the effects that scale with cube of the radius?
Here is an answer from SE https://physics.stackexchange.com/a/318734
The temperature is actually inversely proportional to black hole mass and the power that is radiated away even falls like the square of the mass. (A rough but illustrative derivation can be found in https://en.wikipedia.org/wiki/Hawking_radiation#A_crude_anal... )
Neither. Hawking radiation - if it exists – is far too weak to be detected this way.
100 billion kilometres wide, is that correct?
one time he also said 100 billion billion kilometers.
Can someone explain in layman terms: If graviton particles or gravity waves travel at light speed, how does this information escape the event horizon?
It doesn't. It escapes from outside the event horizon. The event horizon is the dark area in the middle.
A rephrasing: How does the gravity-information about what's inside the event horizon get out?
That's a really interesting question. (And you did say "graviton particles or gravity waves" in your first post, and I missed that.)

At first glance, I think that the gravity information can't escape from inside the event horizon, just like light can't. That means that the event horizon describes a frozen version of the mass inside it, not a current "live" version.

And that seems to work, if you think about gravity waves. There aren't any changes to the gravitational field coming out from inside the event horizon. But it doesn't work so well if you think about gravitons. "There aren't any gravitons coming out" should be equivalent to "flat worldlines", which is very much not true just outside the event horizon.

It also doesn't seem to work for a situation like a black hole merger. The spacetime outside the event horizon is this frozen snapshot, but it can still do this spiral around this other black hole? That doesn't seem to make a ton of sense.

So I'm not sure my answer is very good. But it's a fascinating question. If anyone has a real answer, I'd love to hear it.

It’s not that interesting unfortunately, although I liked your approach. A graviton would be just another boson like a photon, and like a photon would be unable to escape. All of the worldlines of a graviton within the event horizon would lead to a collision with th singularity. It’s just another aspect of “No Hair” on the hole.

Remember that this applies everything where r≤1. As far as “flat” worldlines I think you might be thinking of a geodesic approaching r=1 in terms of a null geodesic, which isn’t necessarily true unless we’re dealing with a photon or graviton. Regions I,II of the Classic Kruskal-Szekeres extension illustrates this pretty clearly.

https://en.m.wikipedia.org/wiki/Kruskal–Szekeres_coordinates...

The total mass of the black hole (and all other information possible about it) can be described in terms of the boundary at r=1, so there’s no problem with mergers or accretion. To answer Wallace’s original question, we see no information escaping the black hole. What we’re seeing is sort of like shining a light on an absence of information, and observing the shadow cast. That’s not quite right, but it’s close.

But there pretty clearly is a gravitational field at r > 1. If that field is made up of gravitons, and a graviton can't escape from the mass to outside r = 1, then what is the source of the gravitons that compose the field at r > 1? If they don't originate at the mass, then... what?
I think the downvote brigaiding on this thread is coming from a particular set of users.

I noticed my karma is jumping down in waves. Unrelated comments are all being downvoted at the same time, suggesting unlikely coincidence or that some users are clicking on my profile and going through downvoting all the comments.

The manifold is well-behaved and continuous at r=1, and mass is one of the few characteristics a black hole has other than spin and charge. Gravitons from within the event horizon won’t escape, but the event horizon itself can be thought of as the entire black hole (for everything outside of the black hole).

This discussion might help where my ability to answer your excellent question is failing: https://physics.stackexchange.com/questions/937/how-does-gra...

I also saw that stackx discussion when I asked the question and Google'd it. But I was surprised by the fact that while I'd seen in social media, QA, etc this question had been asked before, I was looking for something of a longer or more authoritative source that was accessible to people outside of academic study.

The same problem would exist for the electric field from a charged black hole. However, static fields don't need propagating photons to establish them, so you don't have to get photons from inside the black hole in order for the electric field to be established outside.

The same would be true of gravitons. But one respondent indicated that general relativity can't do a second quantization like electromagnetism, and therefore gravitons are... suspect? Impossible? Not proven? It wasn't clear to me how strongly to take that statement.

What do you reckon is in the black hole?
sbhn
Why are they all wearing suits?
Is this as real as the computer edited NASA images (eg of earth) or is the actually real?
Here's today's xkcd comparing it to the size of our solar system: https://xkcd.com/2135/
What a time to be alive! I wish Hawking got to see it.
Lol, why would someone downvote this?
black ties and revelations...
-27:06
why is it oblong???
If you mean the brightness asymmetry, it's because the accretion disc is spinning. This video predicts pretty well all of the features we expected to find, and it lines up with the actual image.
Thanks! Over 150,000 viewers right now.

What would that look like? Knowing all particles between us and your target, and then popping a mass into existence in such a way you get a measurement?

https://coincircle.com/l/sfX5us6vcQ
At what time do they show the black hole? i hate links to videos that aren't at the time that the title is about...
Will it be possible to use this data to study black hole radiation or pair production?
https://i.redd.it/p55wgfxsrfr21.jpg
even the black hole photo is sucking up it's own press conference! :-)
Same here
Screenshot from press conference: https://imgur.com/UBsPgzw

Edit: Better posted above: https://pbs.twimg.com/media/D3y037OW0AQmpAf.jpg

more masturbation to the fanfare than the actual research picture
thanks, i didn't watch it.

  INT. EUROPEAN COMMISSION – PHONE RINGS

SAMARA
Seven days...
Why does the ESA always couch their discoveries in these stupid press conference panels? Every time I try to watch something of theirs it's a bunch of old people blabbing. Show the pictures and stop talking!
This isn't ESA, it's unrelated EU-funded research.
My God, it's full of stars!
ape4
A small thing. It could have been nice if the scientists didn't have commercial bottled water on stage. As an example to the world. Reusable personal containers would have been nice.
Most scientist I know have a reusable water bottle on their desk. And a coffee cup. But it will likely have a cat or a joke of the "astronomers do it in the dark" flavour on it. Not something you typically want to show on TV. Also they traveled from their home institutes to the location of the press conference and got handed that plastic bottle by some well-meaning PR person.
ape4
For this event they could have purchased multiple use containers for each person. Wasteful but a better image. So not really their personal containers.
One difference between a Tesla or Apple style event vs a staid, scientific one such as this. Starting in the evening vs 9am...
Isn't that related to the fact that it has been announced across the world at the same time? In europe it was announced at 3 pm for example. I'm sorry, I don't understand your point
That showmanship counts. I don’t believe HN would argue with me if I said “a strong sales group can make or break a company”. Why is it unfashionable to suggest that, in the marketplace of ideas, with an announcement of this magnitude, this exciting, this “sexy”, the presentation of the announcement would benefit from being delivered in a likewise suitable atmosphere. At night, as an event, in a cool warehouse with cool music. I’m not trying to take anything away from the inherent excitement and importance of the news. Just suggesting that the cause could be furthered even more if there was a little hype, a little showmanship. Rather than a well lit lecture hall populated by scruffy reporters, early in the morning, morning as defined in the locale the event is being held.
I would argue that "hype", or as you say "showmanship", is actually damaging when it comes to science. Maybe it's just me, but I try to stay away from pop-science news sites because of all the hype they're filled with. As others have said, I like scientific conferences to provide the evidence, that is enough for me. As for the "early in the morning", as I already said, is a consequence of trying to make it possible for as many people as possible to follow the conference, I don't think anyone would be against another conference in the evening for american viewers. There were 5 "locales": Brussels, Santiago, Taipei, Tokyo, Washington. Unless I missed something, I still disagree with you.
Apple always have their unveilings in the morning pacific time.
Ha. My bad. Thanks for correcting. I always streamed after the fact. Prob because they were early.
beat
Appropriate types and degrees of showmanship/salesmanship depend on the target customer. And scientists, by and large, don't seem to be concerned with impressing the general public - or at least, that is far secondary to the importance of impressing other scientists.

One could argue that making an impression on other scientists is the basis of the scientific method. And we impress with the quality of our evidence and the repeatability of our experiments.

> And scientists, by and large, don’t seem to be concerned with impressing the public...

Some quotes from European Research Commissioner Moedas, answering the first question.

“...which is that this is linking between the citizens and science, how important is that?...”

“Because we want European citizens to feel connected.”

“I’ve never seen this room so full.”

“It’s so refreshing to come here, to see so many people, to see people clap. I mean it’s very rare in a press room to have people clapping.”

During his introductory comments also, he is clearly excited and wants to engage people, and not simply through the scientific method. He talks about watching sci-fi movies as a kid and books on science.

People. It’s ok to throw Science a party.

MASSSIVELY UNDERWHELMING

As a person who has no interest in these intergalactic shenanigans, it looks just like another ball on fire. I wanted to be excited, I really was, but this is just another picture.

A giant leap for mankind, and i fully recognize that, but the awe... nada. It's just another picture really. There is nothing fascinating about it.

Hats off to the people who brought this to us though. I know gravity of the matter and how daunting a task it was. Keep on!

If it fails to pique your interest, oh well, but the more you read about black holes and what is observable about them, the stranger it feels to be looking at it face to face.
ttul
Perhaps consider this: "VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a sidewalk café in Paris [6]."

What's surprising about this image is how utterly microscopic the thing is that was observed - from our location. The width of the event horizon is 40 billion kilometers. That's only 267x the diameter of our orbit around the Sun. But the M87 black hole is 26,000 light years away. 26,000 light years is 2.45979e+17 km, or 639,903,746,098 times farther away than the moon.

53 million light years. 26 thousand would still be in our own galaxy.
ttul
Quite right. Thank you for the correction.
I am fully aware of the theory and excitement over all this. I just expected something... different. I thought i'd be wowed by something new. It literally looks just like a regular photo.

Is there a lot of context behind it? Sure. Is it a HUGE leap in our advancement? Definitely. Is it an eye-turning picture? NO. That is all.

Black holes are fascinating, their picture simply isn't, for me at least.

Good video that correctly predicted the image and describes why it looks the way it does [1].

TL; DR The dark area is the entire surface of the event horizon, including the side facing away from us, plus some more due to photons missing the event horizon "directly" being drawn in. One side is brighter due to its being Doppler boosted.

Wow, the video you posted is even more informative and clear than the actual press conference, and it was created by someone who hadn't even seen the image yet based purely on the mathematical predictions of what we would see.

Kind of sad that after all the amazing effort and resources that have gone into the creating the image that the international team couldn't have featured an explanation as clear as this in their actual press conference.

teej
Different target audiences for a science YouTube channel and a scientific findings press conference.
It'd be extremely shocking if he hadn't been able to. The math has been known for a very long time the largest differences would be based on the orientation of disk relative to us but that has been mostly known since the original Hubble picture. If he'd been significantly wrong that'd mean our understanding of the physics was wrong or something unknown was happening at a pretty large scale.
Everyone knew what the image was going to look like, so it's not any harder to prepare in advance.
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.
Why doesn't he work with the actual astronomers, then?
Just by sharing the news he is working with them helping the global effort.
Because he’s busy making physics more approachable through videos.
Perhaps I should have phrased it as "why don't astronomers work with _him_?"
You don't have to watch his channel for very long to learn that he often does (see his video about the recent gravitational wave detection [1], plus a bunch more).
So amazing that scientists were able to predict what something would look like that we have never seen before.
Einstein predicted the existence of black hole back in early 1915. Pretty amazing.
I thought (relativistic) black holes were first predicted by Schwarzschild in 1916?

(As an aside, I have found a whole extra level to nominative determinism since starting to learn German — Schwarzschild = Black shield)

dmix
It's a little of both, but yes Schwarzschild technically first predicted them.

> In 1915, Albert Einstein developed his theory of general relativity, having earlier shown that gravity does influence light's motion. Only a few months later, Karl Schwarzschild found a solution to the Einstein field equations, which describes the gravitational field of a point mass and a spherical mass.

Or was it the Revd. John Michell? https://en.wikipedia.org/wiki/John_Michell
Michell. And maybe Laplace.

Of course they "invented" Newtonian black holes, not relativistic black holes.

Even so - well ahead of the rest.

This is also called an aptronym.
Einstein first developed the theory and the equations that allowed for them to be discovered.

You can imagine that space-time equations have many solutions and properties that can't be contemplated all at once even having them right in front of you.

Schwarzschild took the equations and obsessed over them for countless hours and eventually discovered that one solution to them implied this phenomenon and therefore he discovered black holes by discovering a specific solution to Einstein's equations.

Of course no one knew at the time if the mathematical solution represented real physical objects that exist in the universe, because it doesn't always happen that way. Occasionally some obscure corner of the math predicts something that's a dead end or anomaly that doesn't have any meaning of value as far as it is known.

They had no way to know one possibility from the other.

It's good science.

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

ad Good science, I just randomly bumped into this video today that very nicely explains the differences between good science and bad science. https://www.youtube.com/watch?v=umo6pMCkcXs (safely skip the first 3 minutes)
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 on a very basic overview: https://www.youtube.com/watch?v=P7n2rYt9wfU
Not sure why you're getting downvoted because (as a physicist) I'd say that especially in the face of a high-level discovery like today's, a healthy amount of scepticism is a good thing.

That being said, it seems your concerns are being addressed in the TED talk you linked to from 8:45 onward?

Moreover, in the NSF press conference today it was said that they had four different teams in four different locations across the globe last year, working on interpolating the data and generating the images and they basically asked the teams to lock themselves in, i.e. to not communicate with each other at all, and use (more or less) whatever interpolation algorithm they thought would fit the data best. And at the end, when the four teams met up last year, they had supposedly arrived at very similar-looking images.

I briefly(!) looked at the papers that were published today ("First M87 Event Horizon Telescope Results" I-VI) and while I'm anything but an expert when it comes to radioastronomy and imaging technology (I'm more a theoretical physics/mathematical general relativity kind of guy), I came across the following statements which, to me, all suggest that they've at least evaluated the data with due diligence (emphases all mine):

"IV. Imaging the Central Supermassive Black Hole" (https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85):

Section 5.2 confirms the statements from the press conference today:

> The imaging teams worked on the data independently, without communication, for seven weeks, after which teams submitted images to the image comparison website using LCP data (because the JCMT recorded LCP on April 11). After ensuring image consistency through a variety of blind metrics (including normalized cross-correlation, Equation (15)), we compared the independently reconstructed images from the four teams.

> Figure 4 shows these first four images of M87. All four images show an asymmetric ring structure. For both RML teams and both CLEAN teams, the ring has a diameter of approximately 40 μas, with brighter emission in the south. In contrast, the ring azimuthual profile, thickness, and brightness varies substantially among the images. Some of these differences are attributable to different assumptions about the total compact flux density and systematic uncertainties (see Table 2).

Section 6, in turn, confirms the statements from the TED talk:

From the introduction to section 6:

> To explore the dependence of the reconstructed images on imaging assumptions and impartially determine a combination of fiducial imaging parameters, we introduced a second stage of image production and analysis: performing scripted parameter surveys for three imaging pipelines. To objectively evaluate the fidelity of the images reconstructed by our surveys—i.e., to select imaging parameters that were independent of expert judgment—we performed these surveys on synthetic data from a suite of model images as well as on the M87 data. The synthetic data sets were designed to have properties that are similar to the EHT M87 visibility amplitudes (e.g., prominent amplitude nulls). This suite of synthetic data allowed us to test the scripted reconstructions with knowledge of the corresponding ground truth images and, thereby, select fiducial imaging parameters for each method. These fiducial parameters were selected to perform well across a variety of source structures, including sources without the prominent ring observed in our images of M87.

From section 6.2:

> We then reconstructed images from all M87 and synthetic data sets using all possible parameter combinations on a coarse grid in the space of these parameters. We chose large ranges for each parameter, deliberately including values that we expected to produce poor reconstructions.

Finally, in the caption of figure 4 of "I. The Shadow of the Supermassive Black Hole" (https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7) they write:

> Note that although the fit to the observations is equally good in the three cases, they refer to radically different physical scenarios; this highlights that a single good fit does not imply that a model is preferred over others

…which, assuming that I'm understanding this correctly, means that the bias in the fits towards one model over another is low.

--

Again, I cannot stress enough that I've only skimmed the papers but from what I did read, I see no good reason not to trust their results.

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
Indeed. Whenever you go looking for something you think is already exists, as opposed to stumbling across an object, there is a danger that the parameters of your search will favor your preconceived notions. One will also tend to describe observed objects in terms that tends to fit your theory. I'm not saying that happened here just that it is a danger.

Astronomy/cosmology is one of those strange disciplines where rather than discover new objects in situ, one discovers their possibility in the mathematics and then goes out to find them. So I and many others were hoping that this image was radically different than the math, potentially opening the door to some new theories. Confirmation just isn't as much fun as raw discovery of the unknown. Example: the recent "cannonball star" observations. We are going to need some new science to explain how that is a thing.

The Event Horizon Telescope site has had predicted images up for ages https://eventhorizontelescope.org/science
z3t4
Side observation: This video, and the video you linked to got two million views in just a few hours. I didn't know black holes where this popular. (market opportunity here)
It's a very well made pop-sci video, which probably substantially increases the likelihood of it being reshared.
eu
If one needs an intro, this video should be watched before watching the press release..
In the video he talks about the Schwarzchild radius but doesn't go into details. It is the distance from the center of the black hole to the event horizon.

Anything which is not in that radius or not already in a path towards it should be safe from not getting sucked by the black hole.

E.g. If our sun becomes a black hole, Schwarzchild radius would be 2.954Km i.e. anything outside ~3Km would be safe.

This was explained in the scishow video on that topic[1].

That “not already on a path towards it” is very misleading. A random object passing anywhere near the Schwarzchild radius is will be eaten by the black hole. The only way for something to escape ‘at 3km’ is for an object falling into a back hole to emit light which just happens to be pointing in the opposite direction from the black hole.

Even light can’t orbit at that distance.

That’s an oversimplification. The Schwarzschild radius is where to find an uncharged & non-rotating black hole’s event horizon, and the event horizon is the surface at which newly generated photos (and all causal influences) can no longer escape.

The innermost stable circular orbit is further out than the event horizon, 3 times the Schwarzschild radius IIRC. Anything closer to that has an unstable orbit.

If the general theory of relatively was tested again and it proved to provide the next result, what does it say about actually is an black hole?

Thus far, from all the experiment and result observed, the theory has been proven to be correct.

Hence, it can be said with 99% certainty whatever it predicts must be correct. I hope it does mention about possibility of creating a worm hole.

No, that is not how science works. We can say with 100% certainty that the theory has not been falsified by any test to date.
A very good (technical) talk about the EHT project and the physics they try to do here: https://www.youtube.com/watch?v=JiS1OJNBrvk

It is a bit old (2012), but comprehensive and with both good audio and readable* slides.

*: In the sense that you can see the letters on them

Another link describing what a black hole is:

Peace

I just stumbled upon Veritasium a week ago while learning about the double slit experiment in quantum theory and trying to see some actual evidence [1] of the experiment.
Pigo
Not sure if I missed it, but can we tell which way the accretion disk is from our view of it?
apparently from the top. i hope we get to find another one sideways because they look cool ;)
perpendicular - we see it almost exactly from the top. Mentioned during the Q&A (41:33 to be exact)
The video JumpCrisscross shared above says this is the black hole at the center of our galaxy, so why isn't its accretion disk oriented the same as the rest of the galaxy? Isn't that weird?
It's actually in a galaxy called Messier 87 which is 55 million lightyears away.
The observed both supermassive black holes at the center of M87 and our Milky Way galaxy Sagittarius A
And FWIW, we don't orbit in the galactic plane. Per Wikipedia, "the galactic plane is inclined by about 60° to the ecliptic (the plane of Earth's orbit)." https://en.wikipedia.org/wiki/Milky_Way And "the Sun is currently 5–30 parsecs (16–98 ly) from the central plane of the Galactic disk." Id.
Not according to Veritasium's comment on his own video as well as the RelAstro group who produced the material[1]: "As there seems to be some general confusion, please note that the image shown here is a simulated one and not an actual image. So far we only have an image of M87. Kind regards, the RelAstro group. "
Ah you're right. Looks like they all should've skipped Sagittarius A instead of adding confusion.
Oh, interesting! Wouldn't it be easier to photograph our own? :-)
jug
During the press conference, they said photographing the M87 black hole was like shooting a hibernating bear, and photographing the Sag A* black hole of our galaxy like photographing a quickly moving toddler. Something about the speed making it much harder. It is also much smaller, but that's less of a problem because it's much closer. All in all apparently making it about the same angular size. But it sounds like they'll get to it, it's just harder.
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.
M87's black hole is currently eating something big, which makes it brighter. The black hole at the center of the milky way doesn't seem to have eaten anything lately, so it's accretion disk may be small or nonexistent.
> is currently eating something big

You mean: was eating something big 55 million years ago ;)

Nope, for the same reason we had photos of the Moon before we had photos of Earth.
Can you expand on this?
What they're saying is that we had to send a camera away from the Earth (in a rocket) in order to photograph it properly, and similarly you'd need to send a camera away from our galaxy (in a biiiig rocket) in order to be able to photograph it properly.
Our solar system orbits at a 60 degree inclination from the galactic plane. See https://web.archive.org/web/20160809194418im_/http://sob.nao...

There's a great general description here: https://medium.com/starts-with-a-bang/ask-ethan-37-the-earth...

I'm not an astronomer nor is geometry my strong suit, so I don't quite know how to interpret and convey the descriptions of our relative motion. But AFAIU while quite low we're nonetheless currently outside the galactic plane. How well positioned we are to see our black hole free of obstruction would, I imagine, depend on the average inclination of everything else. But it seems like our inclination is relatively extreme and for the next 50 million years or so our view should become increasingly more clear.

Nope. The view of our own galaxy's supermassive black hole is completely obstructed by matter within our own galaxy. You can't see to the core of our galaxy; it's too dense. You'd have to send a rocket quite some distance outside of the galactic plane to get a good view of it.
The images are made with radio telescopes, which cuts through the dust quite easily. We have many other radio observations of Sagittarius A* [1], albeit at much lower resolutions. There are also numerous observations of Sagittarius A* in X-ray wavelengths, which is also fine because they are so energetic they simply punch through. All the dust and gas in the galaxy is transparent at most wavelengths except the visible one.

The Event Horizon Telescope is interesting because it is, in essence, a radio telescope that uses a "sensor" that is the size of the entire Earth. As such, it is able to make much higher resolution observations.

Actually not. M87 is a 1000 times farther away than Sgr A* but also a 1000 heavier and thus a 1000 times bigger in diameter. (Diameter/radius scale proportionally with the black hole's mass.) Therefore, the actual angular size on our night sky is the same for both black holes and, from this point of view, both would be equally difficult to observe.

However, as they mention in the press conference, Sgr A* moves a lot faster relative to us than M87, so it's much harder to take a still image. (In the press conference they used the example of trying to take a photo of a toddler with an exposure time of 8 hours.)

If we see it almost exactly from the top, then why is one half of the ring so much brighter than the other?
Relativistic beaming! https://youtu.be/zUyH3XhpLTo?t=490
Already watched the video, thanks. However in his example the disk is not perpendicular to the viewer so the beaming makes more sense there I think.

On the other hand, "almost exactly from the top" is not the same as "exactly from the top".

So that would mean that the right side is tipped slightly away from us, right? Because the matter in the accretion disk starts approaching us at about halfway down the ring on the right side?
Yes, from paper 1:

"Third, adopting an inclination of 17° between the approaching jet and the line of sight (Walker et al. 2018), the west orientation of the jet, and a corotating disk model, matter in the bottom part of the image is moving toward the observer (clockwise rotation as seen from Earth). "

He appeared to have released a new video that incorporates the actual image: https://m.youtube.com/watch?v=S_GVbuddri8
meko
That was a great video, never grasped why interstellar and such showed black holes with the rings on top and bottom.
None
None
So is that hazy diagonal line in the image the accretion disc, viewed edge-on from the Earth?
Great video but he really doesn't do himself any favors by flapping his arms like a rabid goose. Distracting as heck.
m87
It doesn't seem to be that accurate, as expectation was for it to have smoother photo sphere, but it has irregular bulges (5 of them). I think they discussed it briefly in the press conference as well. It would be interesting to see if this would change understanding of general relativity and may be give a hint for a theory of quantum gravity.
acqq
Look at the expectation examples in the scientific paper from 2013 that is, from ca. 6 years ago:

https://arxiv.org/abs/1309.3519

It matches quite good, I'd say. Page 4.

What bothered me more about the video is that of you watch the whole thing, he ends up talking about some theory which leads to another type of image prediction. He never actually explains why he chose to go with the former prediction rather than the latter.
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 video he says "just trust me."

This is a perfectly reasonable criticism, I don't care how many downvotes or personal attacks I get.

It has nothing to do with anyone "being patient." That thread was 90% bullying, which you are taking part of.

Can you link to the comment of yours that I replied to? I can't see it for some reason.
I'm not sure how much we can truly draw from small irregularities in the image. This isn't actually a low resolution image. It is an algorithmically interpolated image created by comparing possible interpretations of the spotty and noisy data gathered from multiple points at different times processed against images of what we think a black hole should look like.
> Good video that correctly predicted the image and describes why it looks the way it does

This is of course a bummer, since this means that the acquired image does not give us any new clues of where our understanding of physics is wrong.

jug
It's probably a bit too early to say because e.g the magnetic field data that was also collected hasn't even been scrutinized yet. This will also almost for sure lend a better understanding of the relativistic jets, in order to hopefully one day tell why they are this way or another depending on the particular black hole rather than just "they are somehow often there".

It's still very early and like the detection of gravitational waves, I think it feels like more of a symbolic step into a new era of space science. It's easy to forget that yesterday, black holes were a result of mathematics and only indirectly shown that they "ought to exist".

So first, I think we need to cut them some slack! Second, I think that if we at all WANT to shatter the Standard Model, I think we first need to be able to do science at the extremes of it! The LHC is one way, probing into the details of black hole mechanics might end up being another

We've furthered our understanding of the truth of the universe. That's not a bummer.
I expect that at the resolution that this picture is taken it would be surprising if new radically physics was found, since it would require our current models to be very different from reality to see significantly different results
I think this is unhelpful parroting of comments on actual cutting edge physics experiments like the LHC. The degree matters substantially - there, we have good guesses of what we might see, but there's uncertainty and new data is immensely valuable for narrowing hypotheses. It's the research frontier.

Reasoning about an image of a black hole is very much within the realm of standard science. Veritasium was able to explain the prediction using essentially ideas that are so basic they're at the high school level. If our basic understanding of physics down to the high school level was wrong (e.g., very far from the research frontier), there would be very very serious issues.

Ok, wait a second. I liked a lot of this video, but there are some aspects which are kind of ridiculous. He says his reason for his confidence in this prediction is "I think it's going to look like a fuzzy coffee mug stain." He doesn't give an actual reason.

He does talk a lot about theory, a lot of it interesting and novel to me, but by the end of the video, most of this theory suggests a different-looking image!

The entire video is his description of the reasons for why it'll look like a fuzzy coffee mug stain. It's "fuzzy" because of the low resolution, not because the black hole itself is fuzzy. Undoubtedly there will be work to improve the best quality photograph of a black hole, now that we have one at all.
That's not correct. Around 25% of the video is discussion around the concept of the radius of photon sphere to the event horizon, and what constitutes the light surrounding the photon sphere (one explanation he gives is that there are infinite reflections). Then he spends the last 30% of the video talking about reflections of the acretion disk. This is the theory that he never included in his original prediction, but doesn't explain why he made that call.
Uh.. It's the reason that the "shadow" is larger than the Schwarzschild radius. He's describing the ratio of the "rim" to the "hole". So while the picture may be fuzzy, there's information in it anyway about what the pictures means relative to how large/spin we think the black hole is. In fact I wish he'd said more about the Doppler effect.
Ok I mean, now what you're writing, that's not even wrong. The black part of the image being larger than the actual radius of the blackhole is a discussion about the relative size of the black area you see in the image, to the actual black hole itself. I think that should make sense to you? It's not an argument about why he predicts it will look like a "fuzzy coffee stain," as opposed to other simulated images. Are you able to see the difference between those two ideas?

I think you have some other discussion you were having confused with this one. To remind you about your earlier comment, you stated disagreement with me, saying this video was him only talking about why he predicted the image to look like a "fuzzy coffee stain" as opposed to some other simulated and theorized predicgions. I think the above paragraph and reply should obviously show you why this is actually not true. Are you still with me?

I do think most of the video is interesting, but he never states an argument about why he chose that prediction. That was what I thought was ridiculous. Science is about reason and evidence, not just saying "believe me."

Maybe you watched a different video? You should watch this video, the last 30% talks about simulations done in which the acretion disk reflects around the black hole, he uses example images which look a bit different!

The reason for the fuzziness should be obvious. It's really far away and it's really hard to see. Expecting a jump from "never seen before" to "seen in amazing visual clarity" is unrealistic.
That's also not even wrong. You can't see why?

Let's say we're imagining what Uranus would look like. I draw a picture, and say it should look like a "fuzzy Jupter." But you ask, why should it look that way? Do you have a reason? And I say you should be confident, but don't provide an argument. By the end, I start talking about how it might look like Saturn.

Then I come along and say, "it should be obvious the fuzziness is because it is far away."

That final statement is not even wrong. It misses the point.

Are you upset that the Veritasium video didn't explicitly spell out for you that this black hole is very far away, so the first image of it ever is basically certain to be fuzzier than IMAX fidelity computer simulations used in a Hollywood movie?

I think you're being very silly.

What? You obviously didn't read what I wrote.
> "What? You obviously didn't read what I wrote. Are you ok?"

You're ranting about Saturn and Jupiter for some reason. Why don't you calm down and look at page eight of the paper that Veritasium video was based on: https://ve42.co/luminet "Image of a spherical black hole with thin accretion disk Astronomy and Astrophysics, vol. 75, no. 1-2, May 1979, p. 228-235"

Look at that last image, and squint at it until it gets fuzzy. Lo and behold, a fuzzy coffee mug stain!

Perhaps it was a mistake for him to make the focus of the video on the physics of black holes, rather than the limitations of state of the art radio interferometry... but I don't think so.

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 now.

I think it might help you if you tried to first understand that I am not complaining about the image being fuzzy. I have no idea why you keep going back to that. I spelled out an analogy to explain this to you and you got angry and insulting.

Are you really sure you are ok? You clearly have something going on.

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?"
Everyone present can clearly see which person in this conversation is getting their jimmies rustled.
You truly believe that all of the downvotes on all of your comments are the work of one account?
Really awesome link, thanks for that! It's always interesting to see theory that is decades out in front of experimental confirmation, and then proves to be dead right.
Yeah, I did a double-take when I saw that was published in 1979. I think that's really cool.
He isn't explaining why the blackhole would look like a fuzzy coffee mug stain. He's explaining why the _picture_ of the blackhole will look like a fuzzy coffee mug stain.

To your point, it's like taking a picture of Uranus with film and waiting for it to develop. People familiar with the matter can guess what the _image_ will look like not what Uranus actually looks like.

This is all very clear in the first 25 seconds of the video if you actually listen to what he's saying.

The first 25 seconds of this video actually does not have sound. The 25 seconds after he begins talking is him talking about Einstein and history.

Unless I'm misunderstanding your intentions and you just meant that as a condescending insult?

I think what you're hoping for is a more exhaustive survey of what black holes are theorized to look like, with different possibilities. Is that right?

The problem here is your expectation does not match the product. It's like you went to a car dealer and are upset they didn't sell you an airplane.

It isn't surprising to me that Derek focuses on one form, since Veritassium is providing content for the armchair consumer, that he chooses what he believes to be the best model and presents that. This isn't a PhD defense, after all, it's just a timely video so that folks can appreciate the image that the EHT group has released (is going to release, at the time of Veritassium's video.)

Did you have some other models in mind?

Interesting to me is that Veritassium's presented model doesn't explain the corona-like features, nor any attempt at explaining the "blobs" although he does say that blobs would be exiting to see. And there they are! What fun.

Yea sort of. I mean I said I liked the episode, I just think this part is bad form (I'm paraphrasing):

>why can you expect it to look like this? well because it's just going to look like this.

Now, I'm not trying to say his prediction was unwise. I just think it's first of all bad form to say something like "the reason is just trust me," in scientific discussions (even if you are correct)... but second I actually do want to know at least some explanation to that question. Granted, I'm not saying the video does not explain anything about the image. I wanted to know: why can we be sure it will look like this, and not other simulated images?

That's all.

You can see on the EHT's own website a gallery of other simulated models of what could be expected from a radio image.

And the second part of my criticism, was that by the end of the video, he was using images inspired by other models, and particularly of one where the accretion disk dominated the image.

I dont care how many downvotes I get, I know the difference between right and wrong and this is a perfectly reasonable criticism.

Anyways, since my posts lost 60 karma in 1 hour somehow (almost uniformly coming from posts in other threads, wtf?) some other opportunistic types see it as a chance for bullying. Even writing stuff like 'you've obviously got your jimmies rustled mate!' or other extremely bad faith assumptions like 'if you cant understand why it's fuzzy, it's far away!' The best is the troll bait comment, 'do you really think one person is downvoting you?' Groupthink, bullying, and authority define right and wrong for some people--they can't even write something that even addresses an actual comment or argument. People are crazy. Eventually they just start addressing the negativity itself, abandoning any substantive argument, and focusing on the negativity itself. The next step is using the negativity as its own justification (you deserve negativity because otherwise you wouldnt be receiving negativity kind of assumptions implicig in the above troll bait comment).

But still all that I dont think explains why comments in unrelated posts (even ones that were being complimented) got the same time-unform mass-downvotes?? I think I haven't experienced anything like this before on this site until recently. I lost 60 karma in the a few hours.

Well, for the record, it wasn't me. I did however read through your comments just now, and it seems there is a pattern of not really engaging in dialogue but just blasting your opinion over and over. Looking at your comments on Julian Assange, for example, it seems clear that you do not think there is any difference between what a NYTimes reporter does and what Assange did. I can't speak to everyone else but to me the difference is quite obvious, and probably that has something to do with why you're being downvoted. You're repeatedly stating that they're the same, without describing why you believe this, and then kind of insulting other people for their belief that in fact they are different. So anyway, I've spent way, way too much time responding to you. Good luck to you sir.
Hmm there is some groupthink, lack of reason, or bullying going on here.

Look at this image for yourself. The article is titled: "Here is what scientists think a black hole. Looks like:" https://www.sciencemag.org/news/2019/04/here-s-what-scientis...

There are not massive differences in the images, but the Vetiasium prediction was (and this is very plain) much more accurate.

This isn't controversial at all.

I also thought the particular statement, "why is it like this, because it is just going to look like this" was bad form.

This is very plainly reasonable.

I think the fact that you and a few other users turned this into an opportunity to go through the effort of writing belittling comments and even put downs and troll bait over something as plain and ordinary as this is indicative of some bad qualities of humanity expressing themselves here.

Of course, your only response will be further negativity as bad people dont possess the ability to admit when they were wrong.

And the statement about Assange is very widely expressed. See here(1). There are articles all over the media, just like that one, echoing the same exact view. They are literally everywhere.

Finally, I noticed over the last 30 minutes all my recent comments went down by -1 each. That really makes it look like I'm engaging with some quite petty and insecure people.

Edit: see, right after I wrote this comment, all my recent comments each, in perfect synchronization, down by -1 again haha.

>He says his reason for his confidence in this prediction is "I think it's going to look like a fuzzy coffee mug stain." He doesn't give an actual reason.

He doesn't need to give a reason. The reasons why it would look like a "fuzzy coffee mug stain" are well known since Hawkings...

Did you see the movie Interstellar? He included it in his video. That's what the black hole looks like, except with the relativistic beaming make one side brighter than the other.

Here's the image from the movie: https://www.wired.com/wp-content/uploads/2014/10/ut_interste...

Now imagine that image being taken far away by several ground-based telescopes put together at the edge of their capabilities and using math to error correct and stitch together the final result. What you get is what we saw.

Ah, sure. Also, if you go to the EHT's own website, they have a gallery of predicted, simulated images.

Here is another prediction: https://www.sciencemag.org/news/2019/04/here-s-what-scientis...

I just wanted to know why he went with that one because his prediction was really accurate. And I thought him saying 'just trust me' was bad form.

He did talk some about this, but he didn't really say anything about why he thought his illustration would be so accurate compared to a lot of other stuff seen in the press.

I dont care (or have any idea why) how many downvotes or insults I get. It is a perfectly reasonable question and criticism.

I don't see the difference, the predictions are the same.

The only changes in the image depend on what angle the black hole is being viewed at which would influence whether we see a band across the middle and the slimmer inner ring.

Lol the image I linked is obviously very different.

There is some groupthink going on here affecting people like you and others. The above is obviously plain.

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 am just stating plain facts about what is in these images.

At the time I saw this video when he said "you can be confident, because... (no reason given)" was really the thing that I thought was annoying.

I think you can see the differences in the images. They're not huge but the smooth gradiants vs irregularities/coffee stain/blobbiness is plain to see I think.

Edit: from the horses mouth himself, one of the lead researchers says he didn't expect the image to look like it did: https://youtu.be/ZrDhHDBHkQY

Some of the people here in other parts of this thread have been really offensive for this. It's honestly pretty ridiculous.

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.

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?

acqq
How about forgetting that video for a moment and trying to consider the following picture:

https://static.projects.iq.harvard.edu/files/styles/os_files...

Taken from here: https://eventhorizontelescope.org/science (the official site of the project).

On the left is how it would look like if we weren't so far -- we are 55 million light years far from that. You know the distance from us to our Sun, which you see on the sky but can cover with your own thumb? That object is 3,500,000,000,000 times farther than the Sun is far from us.

On the right is what we can reconstruct from the signals measured because we are so far and we have "only" the telescope the size of the Earth. More details would be visible (the picture would look more like the one on the left) either if we had even much bigger telescope than the Earth, or if the black hole of the same size were much closer to us, which it is not.

Smart move by Veritasium, making a video commenting the news just before the news actually happens. Time works in weird ways around black holes.

Anyways, it is a good one. So is that channel in general.

It is also a good video if you just watched Interstellar, because it also explains why the black hole looks the way it does in the movie. Note that the movie black hole rendering is slightly incorrect for artistic reasons, the video shows the more scientifically accurate version.

It's too bad we cannot see the accretion disk edge-on as in the video. That would have made it a perfect prediction. Maybe it's so thin that it's overwhelmed by the projections of the top and bottom of the back side of the disk.
May be we can see higher resolution if we build an additional telescope.
More distant (longer baseline), not merely additional sensors.

Resolving power is proportional to the (virtual) aperture size, not the total sensor area (that gives more signal strength).

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 20K km/s, or the moon at >1 km/s around the earth, or Mars at 24K km/s around the sun.
I predict we'll do it, though.
Not to mention getting the data back down here. For the analysis of M87, there were multiple petabytes generated: they had to use good old sneakernet and ship hard drives.
Given the observation period has been multiple years, does that virtual size include the orbit of the Earth? Or is there something that limits it to still being Earth-sized?
As far as I know, Veritasium and others occasionally join efforts and coordinate around soon to be published scientific discoveries in a goal to increase exposure. Don’t know if this was the case with the black hole image.
It probably wasn't coordinated, because he got the black hole that was being imaged wrong.

He said we would see a picture of Sagittarius A*, but we actually got the black hole at the center of M87.

I thought we got both, which is the best possible outcome: no one is wrong and there are more black hole photos.
We didn't get both, we only got M87. Sgr A is dimmer, so it needs more number crunching to get a good image
They observed both, watch the follow-up: https://www.youtube.com/watch?v=S_GVbuddri8

"The Event Horizon Telescope Collaboration observed the supermassive black holes at the center of M87 and our Milky Way galaxy (SgrA*) finding the dark central shadow in accordance with General Relativity, further demonstrating the power of this 100 year-old theory."

But in the press conference they specifically said they weren’t releasing SgrA* yes because they hadn’t completed their analysis. They released pictures after that?
You're right, it looks like they are still observing Sagittarius A but what they released was only a simulation for that one.
Apr 10, 2019 · 29 points, 6 comments · submitted by matco11
First picture of a black hole from the EHT. No decent picture released yet. Just what's on the projection screen at the press conference.
https://www.nytimes.com/interactive/2019/04/10/science/event...

Scroll down to see the released image.

I thought last year they were working on getting the picture of Sagittarius A. Not sure why they changed the plan.
Duplicate of the post from yesterday: https://news.ycombinator.com/item?id=19624226
It wasn't Einstein who first conceived the idea of a black hole, one of the earliest records of someone speculating what would happen if a star got so massive that it's gravity would pull back light was John Michell, who termed them 'dark stars'. If that name doesn't ring a bell, think of the Cavendish experiment to weigh the Earth. That apparatus was conceived by the same man.
lelf