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

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

#101

Post by petschge »

alkonaut wrote: post #37

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.

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

#102

Post by beat »

patagonia wrote: post #80
legatus wrote: post #52

Earlier quoted context omitted.

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 c…

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.

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

#103

Post by pflats »

PeanutNore wrote: post #82
huffmsa wrote: post #70

So is a black hole 3 dimensional? Is it a sphere? Or does it only work in certain directions? Does everything "fall" the same direction? I ask because even in a brief history of time, the diagrams are very "single plane of space-time, pulled infinitely deep by the black hole"

A black hole itself (the singularity) is 1 dimensional - a single infinitesimal point. The event horizon around it is roughly a sphere. The diagrams that you are talking about are a visual metaphor that represent 3D space as a 2D plane and the 3rd dimension standing in for the influence of gravity. IRL, spacetime has 3 spatial dimensions, not 2, and gravity is not a dimension but a force. It's hard to visually repres…

I think you've got a typo here: points should be 0-dimensional.

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

#104

Post by simias »

hrdwdmrbl wrote: post #32
piker wrote: post #30

Higher resolution official release seems to be: https://www.nsf.gov/news/special_reports/blackholes/download...

Does that image have a weird pulsing optical illusion for anyone else?

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.

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

#105

Post by rtkwe »

huffmsa wrote: post #70

So is a black hole 3 dimensional? Is it a sphere? Or does it only work in certain directions? Does everything "fall" the same direction? I ask because even in a brief history of time, the diagrams are very "single plane of space-time, pulled infinitely deep by the black hole"

The stretchy sheet of space time illustration is just a simplified visualization space is 3 dimensional so the warping is 3D. The stretchy sheet visual is used a lot because showing a warped 3D grid to be more accurate is a lot harder and a lot less clear and illustrative. Trying to show a 3D grid doesn't even fully capture the situation because it doesn't show how the passage of time gets distorted as well.

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

#106

Post by petschge »

LoSboccacc wrote: post #88
piker wrote: post #30

Higher resolution official release seems to be: https://www.nsf.gov/news/special_reports/blackholes/download...

the original tiff is 7416x4320 it's still too many pixel, it can be a fifth of that while conveying the same amount of information. I'm puzzled by this, if each of those pixel is actually captured by the lenses, why is it all this much uniform? was it smoothed or does this suggest that it's actually a gigantic uniform cloud of gas? haven't seen the whole video of the release, I'll have to catch up later in the evenin…

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.

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

#108

Post by privong »

JoeAltmaier wrote: post #85
privong wrote: post #71

Earlier quoted context omitted.

> We've maxed out the Earth's baseline, so it seems like orbital radio telescopes are the only way to better resolution. Going to higher frequency gives you higher resolution for a given physical baseline length.

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

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

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

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

#109

Post by sametmax »

dreamcompiler wrote: post #93
hrdwdmrbl wrote: post #32

Earlier quoted context omitted.

Does that image have a weird pulsing optical illusion for anyone else?

Interesting that so many people see this but for me it's absolutely static.

If you are focused and calm, or have bad sight, you won't see it naturally. To force it, move your focus from 1cm to the left, then right, again and again, quickly.

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

#110

Post by ncallaway »

nukeop wrote: post #89
posix_me_less wrote: post #63

Earlier quoted context omitted.

How do you explain observed gravitational wave observed by LIGO? It is almost the same as the one calculated for coalescence of two black holes in GR.

It's still no proof of existence of black holes. It's like saying that a lightning storm is proof of Thor, because the legends say he wields the very same lightning. The cause could be something entirely different (spontaneous spacetime ripples, alien generators, whatever really).

> It's still no proof of existence of black holes

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

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

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

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