Unveiling the first-ever image of a black hole [video] • Hacker News Board

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

#491

Post by imtringued » Thu, Apr 11, 2019, 1:21 PM UTC

acqq wrote: post #384

fabricexpert wrote: post #296

Earlier quoted context omitted.

$40m So basically nothing in the grand scheme of anything.

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…

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?)

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

#492

Post by Pharmakon » Thu, Apr 11, 2019, 2:04 PM UTC

AnimalMuppet wrote: post #429

Pharmakon wrote: post #416

Earlier quoted context omitted.

It’s not that interesting unfortunately, although I liked your approach. A graviton would be just another boson like a photon, and like a photon would be unable to escape. All of the worldlines of a graviton within the event horizon would lead to a collision with th singularity. It’s just another aspect of “No Hair” on the hole. Remember that this applies everything where r≤1. As far as “flat” worldlines I think you…

But there pretty clearly is a gravitational field at r > 1. If that field is made up of gravitons, and a graviton can't escape from the mass to outside r = 1, then what is the source of the gravitons that compose the field at r > 1? If they don't originate at the mass, then... what?

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

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

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

#493

Post by hannasanarion » Thu, Apr 11, 2019, 2:42 PM UTC

juliansimioni wrote: post #414

hannasanarion wrote: post #400

Earlier quoted context omitted.

It probably wasn't coordinated, because he got the black hole that was being imaged wrong. He said we would see a picture of Sagittarius A*, but we actually got the black hole at the center of M87.

I thought we got both, which is the best possible outcome: no one is wrong and there are more black hole photos.

We didn't get both, we only got M87. Sgr A is dimmer, so it needs more number crunching to get a good image

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

#494

Post by AnimalMuppet » Thu, Apr 11, 2019, 3:28 PM UTC

Pharmakon wrote: post #492

AnimalMuppet wrote: post #429

Earlier quoted context omitted.

But there pretty clearly is a gravitational field at r > 1. If that field is made up of gravitons, and a graviton can't escape from the mass to outside r = 1, then what is the source of the gravitons that compose the field at r > 1? If they don't originate at the mass, then... what?

The manifold is well-behaved and continuous at r=1, and mass is one of the few characteristics a black hole has other than spin and charge. Gravitons from within the event horizon won’t escape, but the event horizon itself can be thought of as the entire black hole (for everything outside of the black hole). This discussion might help where my ability to answer your excellent question is failing: https://physics.stac…

Thank you for that link - it was very helpful. Summarizing:

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

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

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

#495

Post by acqq » Thu, Apr 11, 2019, 3:43 PM UTC

imtringued wrote: post #491

acqq wrote: post #384

Earlier quoted context omitted.

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…

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 ins…

It’s the opposite: most of the military money goes to the stuff which, if actually used, ends the human civilisation as we know it.

The same goals that US has could be achieved with orders of magnitude less military spending, while also reducing the risks for the whole humanity.

So every alternative to the current practices is infinitely better.

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

#496

Post by wool_gather » Thu, Apr 11, 2019, 3:58 PM UTC

Cthulhu_ wrote: post #485

exelius wrote: post #468

Earlier quoted context omitted.

So put some telescopes in orbit around the Moon and Mars.

A guy on Reddit actually asked this in the AMA. While that would increase the resolution, it would also be extremely difficult. The algorithms used to combine the data from the dishes relies on the exact position of the dish being known at the time of measuring, to a precision of fractions of millimeters. It's already hard to do on the earth's surface, but imagine doing it with a sattelite zipping around the earth at…

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.

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

#497

Post by aurailious » Thu, Apr 11, 2019, 4:12 PM UTC

bashinator wrote: post #382

aurailious wrote: post #358

Earlier quoted context omitted.

Constructing a telescope on Mars would be a valuable investment when a permanent presence is based there.

Mars is smaller than Earth, so planet-wide radio interferometry would be a smaller "aperture" than possible on Earth. If you're talking about extending the telescope to include both Earth and Mars, I imagine that doing the interferometry over changing speeds and distances would be challenging to say the least.

The speeds and distances of the planets are well known at this point and easily predicted. By the time of establishing a permanent presence on Mars the requirements of communications would already put in place the information needed if the DSN isn't already capable of it now. The compute needed would be greater, but so would the availability of it in the future too.

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

#498

Post by wallace_f » Thu, Apr 11, 2019, 4:30 PM UTC

Pharmakon wrote: post #492

AnimalMuppet wrote: post #429

Earlier quoted context omitted.

But there pretty clearly is a gravitational field at r > 1. If that field is made up of gravitons, and a graviton can't escape from the mass to outside r = 1, then what is the source of the gravitons that compose the field at r > 1? If they don't originate at the mass, then... what?

The manifold is well-behaved and continuous at r=1, and mass is one of the few characteristics a black hole has other than spin and charge. Gravitons from within the event horizon won’t escape, but the event horizon itself can be thought of as the entire black hole (for everything outside of the black hole). This discussion might help where my ability to answer your excellent question is failing: https://physics.stac…

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

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

#499

Post by bdamm » Thu, Apr 11, 2019, 5:57 PM UTC

wallace_f wrote: post #465

bdamm wrote: post #364

Earlier quoted context omitted.

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 consum…

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…

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.

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

#500

Post by manigandham » Thu, Apr 11, 2019, 8:09 PM UTC

wallace_f wrote: post #490

manigandham wrote: post #419

Earlier quoted context omitted.

Did you see the movie Interstellar? He included it in his video. That's what the black hole looks like, except with the relativistic beaming make one side brighter than the other. Here's the image from the movie: https://www.wired.com/wp-content/uploads/2014/10/ut_interste... Now imagine that image being taken far away by several ground-based telescopes put together at the edge of their capabilities and using math to…

Ah, sure. Also, if you go to the EHT's own website, they have a gallery of predicted, simulated images. Here is another prediction: https://www.sciencemag.org/news/2019/04/here-s-what-scientis... I just wanted to know why he went with that one because his prediction was really accurate. And I thought him saying 'just trust me' was bad form. He did talk some about this, but he didn't really say anything about why he t…

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.