https://iopscience.iop.org/article/10.3847/2041-8213/ac6615
>"Since the interferometric measurements are often incomplete in the Fourier domain, the inverse problem of reconstructing an image from the observed data set is usually underdetermined. Consequently, the image reconstruction requires prior information, assumptions, or constraints to derive a reasonable image from the infinite number of possibilities that can explain the measurements."
They seem to have gone to great lengths to address this issue, however. Multiple imaging approaches, synthetic data tests, etc.
https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85/...
Why would looking at something that isn't a supermassive black hole at the center of a galaxy prove that this approach works or doesn't work? You'd have different constraints to apply. See for example VLBI measurements of quasars, which seem to employ the same kind of imaging approach. Theoretical models of quasars aren't the same as theoretical models of black holes. They seem to be using these theoretical models as constraints on data interpretation. Unless the theory is completely wrong, which seems unlikely, this looks like a valid approach.
If the original commenter has an issue with this, wait 'til they find out about modern CT scans. Or hell even JPEGs.
To quote from a paper[1] on the history of CT scanning:
"Initial images were of inert objects, then specimens from an abattoir, including bullocks brains and pigs bodies"
or
"The prototype was installed at Atkinson Morley’s Hospital in South London where the first patient, a middle aged lady with a suspected frontal lobe tumour, was scanned on 1st October 1971. The surgeon who operated on her shortly afterwards reported that ‘‘it looks exactly like the picture’’"
The default scientific approach to a new imaging algorithm, and especially a new implementation, it to try it on a simple well understood examples first.
[1] Beckmann, E. C. (2006). CT scanning the early days. https://www.birpublications.org/doi/10.1259/bjr/29444122
Rather than attempt to disentangle, large physics collaborations normally have a “You are on all papers we publish while here and X years after you leave”.
It depends very much on the field of research and the paper in question. In some fields, it's very common to list the names of the authors alphabetically, no matter the size of their contribution.
Then it looks like they average a bunch of these images to get a maximum likelihood image. What is your issue with that?
Besides, to calibrate on a known celestial body, they'd have to have another micro-arcsecond resolution radio telescope to use. Do you have one they can borrow?
I think people's priors here are out of whack -- perhaps the truth does lie somewhere in the middle, but if so, it will be much closer to ETH's version than the OP's.
"...We have seen, and taken a picture, of a Black Hole."
Now the you have published the data from 2017, If I publish my own "photo", and I chose blue with spots of white, using the same library you used and the same color maps:
https://github.com/liamedeiros/ehtplot/blob/docs/docs/COLORM...
Why yours will be more a picture than mine in blue? Maybe I will even splint a little bit of red in there...
I also would like to notice you did not explain why my blue "picture" would be less a "picture" than yours.
Taking a real picture of a black hole like with a cellphone camera would likely be just like a bright white star.
Btw we released the 2017 calibrated data today, too.
https://ui.adsabs.harvard.edu/abs/2022arXiv220510267P/abstra...
Aren't they are peer reviewed?
What is your expertise in astrophysics?
As I understand, this image is not from visible light, not a photo, more like plotting radio measurements. "black holes" are the brightest objects in the universe. It's a bit like an alien scientist showing an X-ray picture of a skeleton:"This is a human!" Some quotes from https://en.m.wikipedia.org/wiki/Black_hole :
"Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly."
The same article is full of words like "implies", " inferred", "indirect" etc. It's not directly proven black holes even exist, see Alternatives paragraph. I'm not sure it's physically possible to take a visible light picture of a "naked" event horizon - then black hole images are pure phantasy.
"Visible light" is not a better or truer electromagnetic spectrum than x-ray or radio. It's a human construct only defined by what our human eyes have evolved to capture, based on what is most useful for us here on earth, nothing more.
There is nothing wrong with getting measurement of an object in any random frequency that happens to be the most interesting/practical. Rendering those results as an image in visible light is also simply the best way to visualize the results for us humans. It is certainly more understandable than hundreds of plots.
> It's a bit like an alien scientist showing an X-ray picture of a skeleton
If that alien organism has evolved to see x-rays, as it might be the most useful spectrum for their particular environment, they would find your comment quite puzzling as that would be exactly what they would see should they meet us.
I shall put aside the parent comments concern about the signal analysis techniques. Those may be valid concerns, and I don't know enough to assess them.
> I'm not sure it's physically possible to take a visible light picture of a "naked" event horizon The event horizon telescope isn't purporting the image emission from the event horizon itself. While the theory of those emissions (Hawking radiation) is very persuasive, they would be incredibly weak for a black hole of even stellar mass, and even weaker for a supermassive black hole. What is being imaged here is hot around the black hole, which is heated due fluid dynamic effect (compression or viscosity, I'm not sure which dominates) as it spiral in to the black hole. The 'image' of the event horizon is the 'shadow' where the black hole blocks our view of the hot gas on the far side.
The fact that this shadow is compatible with the expected size given the mass of this black hole is a scientifically interesting result.
I also think it's scientifically interesting and appreciate the work.
But it should be called a model or illustration, because a human could never see this with bare eyes.
Ofcourse each wavelength of light works a bit differently, like with the X-ray example, you need to understand how X-ray works to understand what you are looking at.
A model or illustration is something that would be product of our calculation or imagination, that was given visual form.
I'm maybe grumpy because this relatively featureless image of relatively massaged data is presented by mainstream news as "FANTASTIC new photo of a Black Hole! WOW! It looks just like in Interstellar!"
What is the problem here? Surely skeleton (or other things detectable via X-rays) is an integral part of a human. If you have no way of seeing an alien, but have an x-ray of them, wouldn't you say we have a significantly better understanding of this alien species, than having nothing at all?
How confident are we that our current simulations accurately reproduce the universe?
Given how many unpredicted and supposedly impossible exoplanet and star configurations that keep being found, I'd say the current model is not doing so well on the prediction front.
https://www.science.org/content/article/forbidden-planets-un...
In comparison, general relativity is one of the most well tested theories in physics, having been undergoing rigorous testing for over a century, and regardless, the point stands that the results were close to the model, thus providing evidence for the model's validity.
Newtonian gravity is good enough for that problem, and the problems have nothing to do with not understanding gravity well enough. The problems have to do with things like complex chemistry in stellar accretion disks, how grains in these disks stick to one another to eventually form rocks, and so on.
The fact that some models somewhere have problems has no bearing on whether the image reconstruction for Sgr A* is valid.
CPU performance and aerodynamics are two completely unrelated domains.
I happen to live and work near JPL. The astronomers there have none of the qualms you do about this image, because it turns out the professionals working on this image actually took such things you're complaining about into consideration when refining the data. And if you had read the publication accompanying this image, you would have known that.
Also, they weren't just looking for a glowing circle...That's a shockingly ignorant way to characterize their work.
But I'm sure you're more of an expert than anybody serving in a peer review board.
In the process of doing so, questions and clarifications may better reveal problems with the underlying science itself, which can result in the paper being withdrawn or declined. But peers don’t independently validate results.
At the same time it should be noted that published criticism has to meet the same bar. “You didn’t do the experiment the way I would have” is not really strong criticism. Experiments or observations can always be done better; this is a central ethos of science.
The strongest criticism is usually to conduct one’s own experiment the way one wants, and then show that it produced better results.
Why should I trust you that you know more about astronomy than a team of astronomers and a peer review board?
I've asked you this three times so far and you've not given an answer.
No it doesn't. Most peer review doesn't even attempt to reproduce results, which is the real way to make sure the science is sound.
One constructive approach to criticism here would be to take the documented imaging process and apply it to other data. If it produces results that don’t match existing evidence, that would be evidence it is flawed.
On that point, scientists don’t need you to chastise people for questioning their authority online. I think a lot of them would be offended at the idea that you think that is what they want.
That's because it's a straw man argument. As has been stated elsewhere in this thread, the OP's concerns are addressed in the actual papers, which the OP conveniently ignores.
> appeal to authority is essentially the opposite of modern science.
Well, it's a good thing they're not doing that then. An appeal to authority is when you rely on an expert's prominence in one field to justify their opinions in an unrelated domain, e.g. putting credence in a software developer's pontifications on imaging black holes just because they're good at software. "Appeal to authority" doesn't apply to actual authorities in their domain – otherwise you would never be able to call expert witness at a trial, for example.
Not OP but I disagree, an appeal to authority can be any authority, even those that are experts in the field. Even the most knowledgeable experts make mistakes, so appealing only to authority is not enough, granted I haven't read the paper nor have any stake in this issue, so it's possible that when the op appealed to authority they were actually trying to appeal to the arguments presented in the paper by proxy, which is fine. But a bald appeal to authority is always flawed, and expert witnesses are just a concession the law has to make to get anywhere. In the words of Richard Feynman; "Science is the belief in the ignorance of experts".
I'm not sure why you don't think that applies here? Only a slim fraction of the population is knowledgeable enough to grok the methodology of EHT.
I mean, if an appeal to authority were as you defined it, then engineers would be making an appeal to authority when they invoke Newton's laws (after all, they haven't derived them), biologists would be making an appeal to authority when they write python code (after all, they didn't write the python compiler), and so forth. Trusting that specialists can do their jobs isn't a logical fallacy – it's a type of inductive reasoning and, critically, a type of reasoning essential for the modern world to function.
Then how can you say the criticism seems substantive? He brings nothing to the table to show that his criticism is valid, it's basically "I don't like, therefore wrong". The proper way criticize their paper would be conduct your own experiments using their parameters and methodologies and show that the results you obtain do not match theoretical results or results of other observations through other means.
>On that point, scientists don’t need you to chastise people for questioning their authority online. I think a lot of them would be offended at the idea that you think that is what they want.
We question their authority on this specific subject they seem to be criticizing. If you make a claim without having at least the background to support said claim, what value does it have? It's the same as a person without background in microbiology or virology claiming vaccines don't work when they don't even begin to understand the science behind it and the mountain of evidence that says otherwise.
There was some hype about: FTL events, life based on cyanide not phosphorus…
Careful with “peer review” when the set of peers is invested in the same type of results.
I've looked at their methods for their earlier images and they seem to be hunting for a circle that looks like a black hole in their data. The EHT's full imaging stack has never been calibrated by looking at a known celestial body to compare images to validate their algorithms. They have calibrated their signals from results of other instruments, but their imaging algorithms change to fit their wanted results. This is my biggest problem with their approach. Anyone can modify algorithms of any arbitrary data to get an image of a glowing circle. A better method that shows a more true image would be to calibrate their imaging algorithms against a known celestial body to make sure their techniques produced comparable results from other instruments. Then they should have taken their calibrated imaging algorithms and gave it data from their target.
I'd have more confidence in the EHT if they would not change their imaging algorithms across images and give a side-by-side comparison of a known celestial body that other radio telescopes have imaged to verify their whole imaging stack.
To me this a just a big PR stunt and I'm very skeptical of their image.