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Sagittarius A*

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aetherist:
Here is a copy of a comment made on the Thunderbolts forum, re the EHT, re papers explaining how the EHT paint pretty pictures of blackholes, or u might call it the assembling of a pretty puzzle, or the processing of pretty patchworks.

https://www.digitaltrends.com/news/black-holes-scale/
Black holes all look like donuts, regardless of their size……..………. The black hole, called Sagittarius A*, is a type called a supermassive black hole, which is found at the center of almost all galaxies. Ours is on the smaller end for such giants: At 4.3 million times the mass of the sun, it’s much smaller than other monsters like the one is Messier 87 which was imaged in 2019 and which is 6.5 billion times the mass of the sun ………….……….. However, images of these two black holes look notably similar, both showing a distinctive donut shape. And that agrees precisely with physicists’ predictions, which said that black holes would appear the same no matter what size they are …………..

https://www.csail.mit.edu/news/method-image-black-holes
……………. A method to image black holes ……………. Researchers from MIT’s Computer Science and Artificial Intelligence Laboratory and Harvard University have developed a new algorithm that could help astronomers produce the first image of a black hole ……………………. Even with atmospheric noise filtered out, the measurements from just a handful of telescopes scattered around the globe are pretty sparse; any number of possible images could fit the data equally well. So the next step is to assemble an image that both fits the data and meets certain expectations about what images look like…………….


https://arxiv.org/pdf/1512.01413.pdf
…………….. Reconstructing an image using bispectrum measurements is an ill-posed problem, and as such there are an infinite number of possible images that explain the data. The challenge is to find an explanation that respects our prior assumptions about the “visual” universe while still satisfying the observed data …………. We generate data using a collection of black hole, celestial, and natural images ……………… Flexibility of the patch prior framework allows us to easily incorporate a variety of different “visual” assumptions in our reconstructed image. For instance, in the case of the EHT, simulations of a black hole for different inclinations and spins can be used to train a patch model that can be subsequently used for reconstruction ……..


https://educationalblogspotforyou.wordpress.com/2019/04/13/https-theamazingscienceofhumanbrain-blogspot-com-2019-04-how-to-take-picture-of-black-hole-html/
……………. Algorithms developed to take the picture of the black hole………….. Since there are number of infinite images that perfectly explain our telescope measurements, we have to chose between them in some way. We do this by ranking the images based upon how likely they are to be the black hole image, and then choosing the one that’s most likely……………. But when it comes to the images from black hole, we’re posed with a real conundrum; we’ve not seen any black hole images before…………….. In that case what is likely a black hole image, and what should we assume about the structure of black hole? ………………. If all images produce a very similar – looking image, then we can start to become more confident…………….. One way we can try to impose different image features is by using pieces of existing images. So, we take a large collection of images, and we break them down into their little patches. We then can treat each image like a puzzle pieces. And we used the commonly seen puzzle pieces to piece together in an image that also fits our telescopic measurements. Different types of pieces has distinctive set of puzzle pieces……….

PlainName:

--- Quote ---So the next step is to assemble an image that both fits the data and meets certain expectations about what images look like
--- End quote ---

You seem to be thinking that the image is being used as proof that black  holes exist. It isn't - without the image the things would still exist according to the appropriate theories. So it follows that something that fits the data and looks like what it is expected to look like serves the purpose (that is, of being able to 'see' a black hole, just like you could see that single-pixel image of a doughnut on the moon).

TimFox:
The authors of this paper show lots of calculations to see what possible models fit the observed data, and the reconstructed image is just a side-show.  Of course, the media showed it because it's a cute picture.

dietert1:
Evaluation of models and comparing their predictions with measured data is the standard procedure in experimental physics. The models chosen to be tested are not based on personal preference, nor on religious imagination nor on computer game fantasy, but on mathematics. One criterion is a model to test be "simple" or "minimal". In the case of Sagittarius A* they have a conclusion on the mass, but not yet on the spin. They need more measurements to do that.

The idea of aether as a substance to carry electromagnetic fields and propagate light waves was proven superfluous long ago and isn't part of physics anymore (since about 150 years). It fell victim to scientific progress, similar to "phlogiston".

Regards, Dieter

TimFox:
By the way, my original intent in citing the paper was to show a good example of a well-done peer-reviewed scientific paper, with references, on a very complex topic that is available to the general public (not behind a paywall), thanks to the openness of IOP, the publisher of Astrophysical Journal and Astrophysical Journal Letters.
(Although I'm not surprised by some of the replies.)

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