How to Understand the Black Hole Image

How to Understand the Black Hole Image 8,908,151 viewsApr 9, 2019 Veritasium 12M subscribers We have just seen the first image of a black hole, the supermassive black hole in the galaxy M87 with a mass 6.5 billion times that of our sun. But what is that image really showing us? This is an awesome paper on the topic by J.P. Luminet: Image of a spherical black hole with thin accretion disk Astronomy and Astrophysics, vol. 75, no. 1-2, May 1979, p. 228-235 https://ve42.co/luminet Using my every day intuition I wondered: will we see the "shadow" of the black hole even if we're looking edge on at the accretion disk? The answer is yes because the black hole warps space-time, so even if we wouldn't normally be able to see the back of the accretion disk, we can in this case because its light is bent up and over the black hole. Similarly we can see light from the bottom of the back of the accretion disk because it's bent under the bottom of the black hole. Plus there are additional images from light that does a half turn around the black hole leading to the inner rings. What about the black hole "shadow" itself? Well initially I thought it can't be an image of the event horizon because it's so much bigger (2.6 times bigger). But if you trace back the rays, you find that for every point in the shadow, there is a corresponding ray that traces back to the event horizon. So in fact from our one observing location, we see all sides of the event horizon simultaneously! In fact infinitely many of these images, accounting for the virtually infinite number of times a photon can orbit the black hole before falling in. The edge of the shadow is due to the photon sphere - the radius at which light goes around in closed orbits. If a light ray coming in at an oblique angle just skims the photon sphere and then travels on to our telescopes, that is the closest 'impact parameter' possible, and it occurs at sqrt(27)/2*r_s Huge thanks to: Prof. Geraint Lewis University of Sydney https://ve42.co/gfl Like him, I'm hoping (predicting?) we'll see some moving images of black holes tomorrow Prof. Rana Adhikari Caltech https://ve42.co/Rana Riccardo Antonelli - for excellent images of black holes, simulations and ray-tracing code, check out: https://ve42.co/rantonels The Event Horizon Telescope Collaboration Check out their resources and get your local link for the livestream here: https://ve42.co/EHT Special thanks to Patreon supporters: Donal Botkin, Michael Krugman, Ron Neal, Stan Presolski, Terrance Shepherd, Penward Rhyme Filming by Raquel Nuno Animation by Maria Raykova 17,817 Comments rongmaw lin Add a comment... Tobblesmash Tobblesmash 1 year ago The fact that the prediction was so close just goes to show how accurate theoritical physics is, we might not have seen the universe, but the physics we know helps us predict everything with a crazy amount of certainty. 3.3K Ritesh Kr. Panda Ritesh Kr. Panda 1 year ago (edited) This is why I am too excited to study Physics and not excited at all at the same time.. it's too complicated yet too fascinating 1.1K Alexander Roque Alexander Roque 1 year ago I can only imagine the joy and satisfaction these scientists get when all of their theories and calculations were confirmed. It's crazy just how much we can learn and understand about our universe with just a bit of observations and equations. Newton had to create an entirely new kind of math just to be able to explain his theories, at the age of freakin' 23! 433 Man in The Moon Man in The Moon 8 months ago This is the clearest, the most easily understood explanation of a BH that I've come across so far. Thank you. 86 mrbomplastik mrbomplastik 1 year ago Fun Fact: The Schwarzschild radius is named after a guy called Schwarzschild, whose name translates to black shield, which makes a lot of sense. 1.3K ramanandasai chilukuri ramanandasai chilukuri 9 months ago My mind was blown at 7:30 looking at the things you could arrive from pure mathematics and physics. Loved it. 40 SingaporeSkater SingaporeSkater 3 years ago Walter Lewin, legendary physics lecturer, just cited this video of yours as the best explanation of the image, in case you didn't know. 13K Veritasium Syed Mazhar Hasan Syed Mazhar Hasan 1 year ago At 7:16, my mouth just dropped to the floor. I can see and understand Gargantua from Intersteller. Thank you so so much. You are a hero. 568 soupbonep soupbonep 1 year ago This is an excellent explanation of this phenomena. The two dimensional side view of the parallel light waves curving around the event horizon was a great visual aid and so was the paper accretion disc. Although I can't imagine how we can measure the Schwarzschild radius with any accuracy. Maybe with the James Webb telescope we will be able to do this? Anyway, great video! 13 Mahir Khan Mahir Khan 8 hours ago (edited) Many thanks for the explanation, clearly a great physics lecturer’s deal. Question: what do you think gave the objects in accretion disc tangential velocity intense enough to start orbiting instead of falling inside the BH due to its massive massive gravitational pull? Katy Veep Katy Veep 1 year ago I cannot thank you enough for this!! I’ve been obsessed with black holes since someone first explained them to me as a kid and your walk thru explanations make me feel like I have a much better grasp of a concept and feel even more excited than I was before!!! THANK YOU!!! 38 David Kowalsky David Kowalsky 5 months ago (edited) Outstanding visualization. I've tried wrapping my head around all the simultaneous gravitational lensing and light bending for some time now and this is by far the best description I've seen or heard. I feel I have a much better understanding of what's happening near a black hole now. Thank you. 4 ElectroBOOM ElectroBOOM 3 years ago Very well explained as usual. One question: when around the end you explained about the Doppler effect, shouldn't it change the frequency of light (change color) rather than its brightness? Thanks! 110 Remus Remus 1 year ago "If you're disappointed by this image.... I think that misses the GRAVITY of this situation" ....I see what you did there :) 720 Kris tian Kris tian 1 year ago What an impressive presentation, even managing to have it be a seamless physical presentation of a black hole. Nicely done! 9 Carn Soaks Carn Soaks 9 months ago Back after three years. This video deserves some sort of award D. It's what I've recommended to everyone I've talked b.h.'s with since you made it. Super clear, ultra concise, uber understandable, and hyper relateable. Congrats to Team Veratasium. 8 Veritasium Kokocipher Kokocipher 10 months ago So awesome! Thanks so much for putting the effort to explain such a complicated concept so we can appreciate just how amazing everything around us really is. 4 Dean Lawson Dean Lawson 5 months ago Such a fascinating video explanation of the "look" and some of the very high level physics of the Black Hole. Thanks for this excellent video! After a good period of time from the release of the actual black hole image, your explanation of it is pretty much spot-on what it looks like!! Thanks again for this - Nicely done! 2 WarpRulez WarpRulez 1 year ago Fun fact: When they were making that movie, Interstellar, they tried to simulate mathematically accurately what the black hole would look like from far away more or less just as an experiment, expecting it to look so boring that they would have to embellish it in order to make it more interesting for the movie, but when they saw the end result it was so spectacular-looking that they decided to go with the mathematically accurate visuals. 2.3K Ricardo Umana Ricardo Umana 1 year ago What an amazing job you just did in a simple and effective manner to help one visualize and understand black holes. Thanks! 3 ElectroBOOM ElectroBOOM 3 years ago It's funny, the black hole image they got is exactly the same as you drew on your black board. Why did they spend so much when they could just ask you to draw it?! Good job! 7.3K Bauke van Bloemenhuis Bauke van Bloemenhuis 8 months ago Wow, absolutely fascinating. That is some explanation. I'm actually surprised I could follow your whole story. I did have to play it twice though :) I've been trying to understand that shape ever since I saw it. I've read and seen a lot of explanations, but most of it was too difficult. None of it made as much sense as your video. It's hard to get your head around, but it landed finally. Thank you 1