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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]

#191

Post by etatoby »

vxNsr wrote: post #151
negamax wrote: post #125

Does anyone remember Interstellar. Their black hole simulation was based on hard science. Looks fairly similar

just had my wife watch it and yea, that was the first thing I noticed, they really did a good job on the science of interstellar. When interstellar came out wired did a full magazine spread on the movie, covering its science, how they came up with the story and what the director did to make sure it was believable. idk what it looks like online but I've kept the magazine.

The visualization I liked the best in Interstellar was that of the wormhole, seen from the outside. (The "travel" through it was rubbish.)

The thing would look like a mirror sphere, floating in the middle of space, reflecting the space around you. Except it would be the space on the other side of the wormhole, not that behind you, and the motion of the "mirrored" image would be opposite of that on a real mirror. (The apparent image on the wormhole's spherical surface would appear to move in your same direction, as you're moving around it, not in the opposite direction as it does on a spherical mirror.)

It took me a while to reason about it and figure out that it was indeed what a wormhole would look like, if we could find or create one.

https://youtu.be/f3ptQ0CPMmU

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

#192

Post by ken »

sus_007 wrote: post #141

Here's an animated explanation of the process by the Event Horizon Telescope. https://youtu.be/hMsNd1W_lmE

Misspeak? This video says it's 4 million times as massive as the sun, but today's press release and Wikipedia article about it both say it's 6.5 billion times as massive.

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

#193

Post by wallace_f »

JumpCrisscross wrote: post #27

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. [1] https://www.youtube.com/watch?v=zUyH3XhpLTo

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!

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

#194

Post by SiempreViernes »

r721 wrote: post #137

"This is more realistic of the uncertainties involved in this high-end image reconstruction. Still amazing though! Fig. 4 in https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85 " https://twitter.com/karlglazebrook/status/111598136971105894...

Yeah, apparently radio interferometry is still very manual and so involves many relatively subjective decisions to produce an image.

That's probably why they had several analysers that they then combined into progressively larger teams until they could produce this Consensus-A picture.

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

#195

Post by m87 »

JumpCrisscross wrote: post #27

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. [1] https://www.youtube.com/watch?v=zUyH3XhpLTo

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.

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

#196

Post by pavelrub »

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…

The singularity is likely a mathematical artifact of the fact that GR is insufficient to describe black holes. In reality (quantum gravity) they probably do not exist.

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

#197

Post by petschge »

SiempreViernes wrote: post #194
r721 wrote: post #137

"This is more realistic of the uncertainties involved in this high-end image reconstruction. Still amazing though! Fig. 4 in https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85 " https://twitter.com/karlglazebrook/status/111598136971105894...

Yeah, apparently radio interferometry is still very manual and so involves many relatively subjective decisions to produce an image. That's probably why they had several analysers that they then combined into progressively larger teams until they could produce this Consensus-A picture.

There is non-manual ways to do it (called self-calibrating), but those need many more antennas. (What you really need is good coverage of the (u,v) plane AND many more different baselines between pairs of telescopes than the number of individual antennas.) If you do not have that self-calibration fails and leads to horrible image artifact or does not converge at all. They limited the influence of the manual calibration by observing a Quasar which is basically a point source between subsequent observations of M87* to get an independent amplitude calibration.

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

#198

Post by beat »

sam0x17 wrote: post #166
beat wrote: post #96

Earlier quoted context omitted.

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 tha…

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. :(

We're all idiots, my friend. Remembering that is the hardest and most important work we can do.

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

#199

Post by MR4D »

O_H_E wrote: post #176
KnightOfWords wrote: post #131

Earlier quoted context omitted.

Yes, we're using a telescope the size of the Earth to look at an object the size of our solar system in a galaxy about 55 million light years away. It's an infinitesimally small patch of sky. On the other hand, the jet from the M87 black hole is quite large and we have good images of it. It's even resolvable by amateurs, I hope to take a picture of it over Easter with a small telescope. https://en.wikipedia.org/wiki/…

> 55 million light years didn't he correct himself and said kilometers

He corrected himself to say 500 billion billion kilometers after mistakingly saying light years.

I haven't done the math, but I believe that roughly equates to 55 million light years.

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

#200

Post by forgot-my-pw »

jjeaff wrote: post #119
JumpCrisscross wrote: post #27

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. [1] https://www.youtube.com/watch?v=zUyH3XhpLTo

So amazing that scientists were able to predict what something would look like that we have never seen before.

Einstein predicted the existence of black hole back in early 1915. Pretty amazing.
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