> 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
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.
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.
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.
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!
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. :(
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.
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.
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.
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
(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.
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.
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.
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
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.
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):
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.
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
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.
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.
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.
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?
> "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.
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.
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.
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.
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...
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.
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.
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.
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.
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?
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.
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.
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.
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.
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?
"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). "
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?
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.
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.
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.
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.)
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.
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.
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. "
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.
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.
"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?
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.
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.
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?
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.
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.
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).
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.
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.
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
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.
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)
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’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.
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.
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?
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.
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?
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.
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.
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.
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.
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.
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.
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...
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.
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.
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.
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?)
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.
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.
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
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.
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).
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...
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.
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?
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).
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.
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.
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.
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.
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.
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!
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.
> 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.
>> 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.
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 :(
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.
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)?
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.
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.
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).
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[ 3.5 ms ] story [ 312 ms ] threadEdit: Better posted above: https://pbs.twimg.com/media/D3y037OW0AQmpAf.jpg
https://www.youtube.com/watch?v=Dr20f19czeE
https://pbs.twimg.com/media/D3y037OW0AQmpAf.jpg
http://webcache.googleusercontent.com/search?q=cache:https:/...
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
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.
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.
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.
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.
https://www.youtube.com/watch?v=zUyH3XhpLTo
> 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.
> 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.
[0] - https://www.youtube.com/watch?v=zUyH3XhpLTo&feature=youtu.be
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.
[1] https://www.youtube.com/watch?v=zUyH3XhpLTo
Been able to make testable predictions and then confirming them or disproving them is the entire (awesome) point.
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.
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 fig...
(As an aside, I have found a whole extra level to nominative determinism since starting to learn German — Schwarzschild = Black shield)
https://en.m.wikipedia.org/wiki/Aptronym
> 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.
https://en.wikipedia.org/wiki/Black_hole#History
Of course they "invented" Newtonian black holes, not relativistic black holes.
Even so - well ahead of the rest.
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 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
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!
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!
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.
I think you're being very silly.
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.
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.
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.
Unless I'm misunderstanding your intentions and you just meant that as a condescending insult?
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.
>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.
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 doesn't need to give a reason. The reasons why it would look like a "fuzzy coffee mug stain" are well known since Hawkings...
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.
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.
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.
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.
There is some groupthink going on here affecting people like you and others. The above is obviously plain.
Perhaps you should post exactly what image you're talking about and what you think is different.
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.
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.
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?
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.
https://arxiv.org/abs/1309.3519
It matches quite good, I'd say. Page 4.
"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). "
On the other hand, "almost exactly from the top" is not the same as "exactly from the top".
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.)
You mean: was eating something big 55 million years ago ;)
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.
[1] https://en.wikipedia.org/wiki/Sagittarius_A*#/media/File:Clo...
[2] https://en.wikipedia.org/wiki/Sagittarius_A*#/media/File:X-R...
[1] https://www.youtube.com/watch?v=VnsZj9RvhFU
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.
He said we would see a picture of Sagittarius A*, but we actually got the black hole at the center of M87.
"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."
Resolving power is proportional to the (virtual) aperture size, not the total sensor area (that gives more signal strength).
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.
https://www.youtube.com/watch?v=S1tFT4smd6E&feature=youtu.be...
[1] https://youtu.be/iphcyNWFD10
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.
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.
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
[1]: https://youtu.be/Iuv6hY6zsd0
Part I: https://www.youtube.com/watch?v=VnJYo6LKzgA
Part II: https://www.youtube.com/watch?v=Nlry6LqWwJ0
Peace
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.
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].
[1]:https://youtu.be/Mm_ks1ce3C4
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.
https://www.amazon.com/Superunknown-Soundgarden/dp/B00IXLQJ8...
I'm not sure if this image is real color or just lightness value and they used a color scheme for drama.
One of my favorite talks ever is on this subject: https://www.youtube.com/watch?v=xAoljeRJ3lU
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.
As for the black hole, looking it at full screen I see it pulsating a little.
https://en.wikipedia.org/wiki/Bicubic_interpolation
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.
There is some more info in the wikipedia article for the Event Horizon Telescope (EHT): https://en.wikipedia.org/wiki/Event_Horizon_Telescope
https://en.wikipedia.org/wiki/Event_Horizon_Telescope#/media...
Astronomy and high energy physics are pretty much the only science I know where this is an applicable unit of measurement
So basically nothing in the grand scheme of anything.
This specific project is more European or even a world project than just US, if I understood correctly.
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?)
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.
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...
https://www.youtube.com/watch?v=zUyH3XhpLTo
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/
[0] https://www.youtube.com/watch?v=LKnqECcg6Gw
https://imgur.com/a/dhN9Pf9
https://www.newscientist.com/article/dn26966-interstellars-t...
http://blogs.nature.com/aviewfromthebridge/2017/03/28/imagin...
Pity, really. Then again, there were other things that made no sense in the movie...
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...
https://www.amazon.com/Science-Interstellar-Kip-Thorne/dp/03...
[0] - https://blogs.futura-sciences.com/e-luminet/2015/02/18/black...
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?
As an aside: that image is basically black and white. The intensity is just mapped to black -> orange -> white instead of black -> gray -> white.
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).
We seem to need a big radiotelescope on the moon then? That should give simultaneous measurement on a much larger baseline?
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.
Furthermore, adding more telescopes will help better image the fainter features in the image (due to larger total collecting surface).
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.
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.
Also I'd be interested to read how they got around scintallation of the Interstellar Medium.
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!
[0] - https://www.jpl.nasa.gov/missions/space-very-long-baseline-i...
[1] - https://asd.gsfc.nasa.gov/blueshift/index.php/2016/07/25/thi...
[2] - https://en.wikipedia.org/wiki/Angular_resolution
Going to higher frequency gives you higher resolution for a given physical baseline length.
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.
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.
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.
[0] http://www.asc.rssi.ru/radioastron/
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.
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.
Telling that it's a US organization that hosts the actual picture.
esa.int and eso.org seem to be down actually.
The speakers are referencing images and diagrams that are not visible on screen.
The accomplishment speaks for itself. The delivery can be improved.
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 :(
EU: https://www.youtube.com/watch?v=Dr20f19czeE
US: https://www.youtube.com/watch?v=re_o0uckG-M