1 00:00:00,550 --> 00:00:22,630 So I think it's sort of. So welcome to the Nineteen Kinsey Lecture. 2 00:00:22,630 --> 00:00:27,940 I'm delighted that this on this occasion, we have Professor Heino Falkor, 3 00:00:27,940 --> 00:00:36,160 who is a professor of radio astronomy and astro particle physics at the University in Nijmegen in the Netherlands. 4 00:00:36,160 --> 00:00:42,820 Heino read Physics in Bonn and in Cologne, and got his PhD in 1994 for. 5 00:00:42,820 --> 00:00:50,710 Since then, he held positions at the Max Planck Institute for Radio Astronomy Bonn and also University of Maryland and the University of Arizona, 6 00:00:50,710 --> 00:01:02,650 before he returned to Nijmegen in two in 2003, where he became the focal point for the expansion of a new group in astrophysics in the Netherlands. 7 00:01:02,650 --> 00:01:05,470 His research contributions are very wide. 8 00:01:05,470 --> 00:01:12,880 They span radio transients, cosmic rays, active galaxies, the Galactic Galactic Centre and, of course, black holes. 9 00:01:12,880 --> 00:01:19,600 He was one of the major driving forces behind the Low for International Radio Telescope, 10 00:01:19,600 --> 00:01:27,220 which we have a big involvement here, even exploring the idea of putting such an array low-frequency array on the Moon. 11 00:01:27,220 --> 00:01:34,960 He's played significant roles in the square kilometre array and the portrays telescope in Argentina, 12 00:01:34,960 --> 00:01:42,100 but most relevantly, for today, he's the chairman of the Science Council for the Event Horizon Telescope. 13 00:01:42,100 --> 00:01:44,770 He's an enormously distinguished scientist. 14 00:01:44,770 --> 00:01:52,130 Amongst his accolades that he's a member of the Royal Netherlands Academy for Art and Science, this is the one I like best. 15 00:01:52,130 --> 00:01:55,480 He's a night of the Dutch order of the Lion. 16 00:01:55,480 --> 00:02:00,790 And in 2011, he won the most prestigious prise the scientists from winning the Netherlands, which is the spin. 17 00:02:00,790 --> 00:02:02,800 There's a prise. 18 00:02:02,800 --> 00:02:13,780 I'm reliably informed that this picture in the top left here of the first image of a black hole which appeared in the media in April this year, 19 00:02:13,780 --> 00:02:20,620 has been seen by over four billion people. Surely no other hints electorate can claim this. 20 00:02:20,620 --> 00:02:37,870 So it's my great pleasure to introduce to you, Professor Heino Falko, to deliver the 19th symmetric the first image of a black hole. 21 00:02:37,870 --> 00:02:41,740 Thank you very much. Can I be understood? OK, good. 22 00:02:41,740 --> 00:02:47,860 Yeah, I was here actually already in February and giving a lecture on the same topic, but it wasn't allowed to say anything. 23 00:02:47,860 --> 00:02:52,420 So it was very. And so as a punishment, I had to come back. 24 00:02:52,420 --> 00:02:57,230 But I must say I've been treated so well. I think I want to be punished more often and like the. 25 00:02:57,230 --> 00:03:08,500 It's very nice to be here. Indeed, this is work with actually almost spends time since my Ph.D. until it came to fruition in the end. 26 00:03:08,500 --> 00:03:12,400 But of course, work you don't do on your own, you do it together with with your students, 27 00:03:12,400 --> 00:03:16,870 with international collaborations, with your colleagues, particularly here in Europe. 28 00:03:16,870 --> 00:03:25,360 And one of the thing I've benefited a lot from personally was his grandfather's European Research Council synergy grant of 14 million euros. 29 00:03:25,360 --> 00:03:31,510 It was given to the three parties here and allowed us to actually do a lot of this 30 00:03:31,510 --> 00:03:36,790 work and made a significant contribution to this international collaboration. 31 00:03:36,790 --> 00:03:42,640 And I say this is an international collaboration of about, well, the papers have 350 people. 32 00:03:42,640 --> 00:03:46,330 So in the collaboration there are two hundred fifty. 33 00:03:46,330 --> 00:03:56,890 And this year, both from our collaboration meeting in Nijmegen in, uh, in November, um, actually exactly a year ago in Nijmegen. 34 00:03:56,890 --> 00:04:03,420 And that was the first time we were discussing all the signs, and everybody's smiling because they had already seen the results, right? 35 00:04:03,420 --> 00:04:07,060 So we were not allowed to talk about it. But at this time, people were still smiling. 36 00:04:07,060 --> 00:04:13,810 And of course, we had to write the papers. And then the smile disappeared because we were really working day and night until March or 37 00:04:13,810 --> 00:04:18,520 February March to actually get the papers written up and everything into a publishable form. 38 00:04:18,520 --> 00:04:27,760 So it was a very intense period for all of us, but it's certainly memorable, memorable period for for us. 39 00:04:27,760 --> 00:04:32,350 Now it all started. It all started with the centre of the Milky Way, at least for me. 40 00:04:32,350 --> 00:04:36,880 And this is this beautiful image made with the Meerkat telescope. 41 00:04:36,880 --> 00:04:46,030 In fact, as I understood, it was actually made here in Oxford. And this is, you know, I gave this presentation a few weeks ago in CERN, 42 00:04:46,030 --> 00:04:51,640 and then a part of the physicists came to me and say, Oh, this this nice artist's rendition of the Central America. 43 00:04:51,640 --> 00:04:56,440 This is real life. OK, this was real. It's not. It's not. We don't make this up that what happened? 44 00:04:56,440 --> 00:05:01,750 This is a pathfinder to the ESC. So it's it's a sign of what's still to come with so much detail in here. 45 00:05:01,750 --> 00:05:06,070 But anyway, so of course, when we started, we didn't have such beautiful images. 46 00:05:06,070 --> 00:05:10,030 But if you zoom in, this is the plane of the Milky Way and radio and you here with radio, 47 00:05:10,030 --> 00:05:13,150 it can see through the entire Milky Way, it goes through dust. 48 00:05:13,150 --> 00:05:23,350 And so the the plane of the Milky Way glows even brighter than on the sky with stars and the centre is somewhere here. 49 00:05:23,350 --> 00:05:29,920 In fact, it was only found in the fifties using radio astronomy where the actual centre of our Milky Way is because in the optical, 50 00:05:29,920 --> 00:05:38,830 there's most dust clouds and so forth. And in the Milky Way, we were actually off by 20 degrees, so only once after the war. 51 00:05:38,830 --> 00:05:45,050 The radar technology was used for for astronomy. People would find out what the structure of the Milky Way is. 52 00:05:45,050 --> 00:05:50,530 It was a major contribution of radio astronomy in the early days after after the Second World War. 53 00:05:50,530 --> 00:05:54,700 Now, if you zoom further in in this very centre, you actually see more structure as this. 54 00:05:54,700 --> 00:05:59,410 Here is what's called Sagittarius A West. And then in the very centre, 55 00:05:59,410 --> 00:06:04,540 you see this this radio source Sagittarius called Sagittarius A because this is 56 00:06:04,540 --> 00:06:10,720 in the constellation Sagittarius A because it was the brightest radio source. 57 00:06:10,720 --> 00:06:14,050 And then this was discovered in the 70s, in fact. 58 00:06:14,050 --> 00:06:21,010 So Martin reason was one of the people actually predicting that there should be such a radio source in the centre of our Milky Way. 59 00:06:21,010 --> 00:06:23,650 Because in analogy with other galaxies, 60 00:06:23,650 --> 00:06:30,970 quasars which were found where people were thinking this could be powered by supermassive black holes and they all had these small, 61 00:06:30,970 --> 00:06:33,550 very small radio sources in the very centre. 62 00:06:33,550 --> 00:06:39,880 And the idea was, well, if in these quasars, far away, they are these supermassive black holes with radio emission, 63 00:06:39,880 --> 00:06:42,610 maybe you should have one in the centre of our Milky Way. 64 00:06:42,610 --> 00:06:53,440 And lo and behold, in 1974, this thought was found actually first in us and then confirmed in a actually in the Netherlands with the Westerbork array. 65 00:06:53,440 --> 00:07:01,130 And then it was called Sagittarius a Star Y star because star marks an excited state and an atom. 66 00:07:01,130 --> 00:07:06,670 And people were before that saying, calling the compact radius source in the galactic centre, and they were tired of it. 67 00:07:06,670 --> 00:07:12,100 And they said So that's called Sagittarius a just star. That's, you know, that's, you know, and that stuck with us today. 68 00:07:12,100 --> 00:07:17,470 It's not a not a fancy name, but you know, we have to live with it. 69 00:07:17,470 --> 00:07:22,810 And and what we see here is actually what I said an optical view of the Milky Way. 70 00:07:22,810 --> 00:07:28,480 Right. With, of course, a camera. You never have such a beautiful view with your naked eyes. 71 00:07:28,480 --> 00:07:36,600 Well, if you go to the southern hemisphere, you get close sometimes, but not quite as detailed and you see all these dust. 72 00:07:36,600 --> 00:07:42,150 Howard's here and which actually formed stars, but they block our view of the the centre of the Milky Way. 73 00:07:42,150 --> 00:07:45,300 Well, you can zoom in using Infra-Red technology also. 74 00:07:45,300 --> 00:07:54,510 Actually, wartime technology was developed in the 80s 90s to actually see at night, but you can also see through the dust. 75 00:07:54,510 --> 00:07:58,650 And then what you find is that the central region here is actually full of stars. 76 00:07:58,650 --> 00:08:04,980 If you go to a region which is about the size of a light year of a few light years, that's the size from us to the nearest star. 77 00:08:04,980 --> 00:08:10,530 You have you millions of stars. So if you would live in the Central Milky Way, the sky would just be full of stars. 78 00:08:10,530 --> 00:08:15,060 There would be a completely different side. There were full of stars. 79 00:08:15,060 --> 00:08:19,110 But where is the black hole? It's hard to pick out. Well, you know, from the radio, 80 00:08:19,110 --> 00:08:23,220 you would have to guess where to look and you zoom further in and then you would see 81 00:08:23,220 --> 00:08:26,790 something remarkable because what you see here is a very high resolution image, 82 00:08:26,790 --> 00:08:31,680 actually a movie made over 16 years by this case. 83 00:08:31,680 --> 00:08:34,530 Our colleagues in Garching, Munich, 84 00:08:34,530 --> 00:08:41,790 what you see in the stars are moving over 16 years and you see that star here actually making a circle actually ellipse. 85 00:08:41,790 --> 00:08:46,050 In fact, that movie repeats. So it's three times the same movie. 86 00:08:46,050 --> 00:08:53,940 If you measure this, you see, it actually makes a perfect ellipse around a point around a central focus point. 87 00:08:53,940 --> 00:08:55,720 This is slightly projected ellipse, 88 00:08:55,720 --> 00:09:04,060 so the focus is not exactly where you would expect it if you see it face on and it goes around here was 10000 kilometres per second. 89 00:09:04,060 --> 00:09:08,610 OK, if something goes wrong with 10000, cannot come out of second round something, 90 00:09:08,610 --> 00:09:13,920 you need a lot of force to keep it tight, OK, to keep it on this orbit. 91 00:09:13,920 --> 00:09:16,770 Now we know where elliptical orbits come from. 92 00:09:16,770 --> 00:09:24,340 This is what Kepler told us and all this describes, for example, the orbit of of planets around the Sun. 93 00:09:24,340 --> 00:09:32,190 They all elliptical orbit, and that goes back to the laws of Newton to that that we can describe then explain these things. 94 00:09:32,190 --> 00:09:40,200 And by applying exactly the same maths and using the same laws, we describe our solar system, 95 00:09:40,200 --> 00:09:44,520 which we can use, where we can use the planets to weigh the mass of the Sun. 96 00:09:44,520 --> 00:09:49,710 We can actually weigh the source in the very centre how much mass you need to keep. 97 00:09:49,710 --> 00:09:53,640 A star was 10000 km per second on this orbit. 98 00:09:53,640 --> 00:09:56,520 Well, it's four million times the mass of the Sun. 99 00:09:56,520 --> 00:10:02,430 In fact, the measurements are now so precise this using ESO's European Southern Observatory Interferometer. 100 00:10:02,430 --> 00:10:08,280 Latest data here you actually would see that star move every day, every hour, actually every night. 101 00:10:08,280 --> 00:10:13,740 I should say every night it would move in and you'd have a maths measurement now. 102 00:10:13,740 --> 00:10:21,750 Four point one five plus minus 0.02 million solar masses concentrated all in that radius source. 103 00:10:21,750 --> 00:10:25,500 So that, of course, was a very strong indication. OK. 104 00:10:25,500 --> 00:10:30,390 The black hole has to be there, but OK, but what is a black hole? 105 00:10:30,390 --> 00:10:33,000 Of course. How do you make a black hole in the first place? 106 00:10:33,000 --> 00:10:41,730 Well, we know one mechanism that makes black holes and that the explosion of stars if a star comes to the end of its lifetime, all the fuel is up. 107 00:10:41,730 --> 00:10:48,990 The star will collapse, and if the mass is, the star is very massive, much more massive than our own sun. 108 00:10:48,990 --> 00:10:56,130 The amount of mass will become more and more concentrated and will actually overwhelm all other forces that we know. 109 00:10:56,130 --> 00:11:05,250 So there is no force, no pressure. Nobody is strong enough to keep that collapsing star, that imploding star from further collapsing it. 110 00:11:05,250 --> 00:11:11,730 Just gravity will pull it together and will actually collapse to almost the point actually will collapse to a point because nothing will stop it. 111 00:11:11,730 --> 00:11:18,850 It will collapse forever. And that's what you see here is actually the remnant of a supernova explosion. 112 00:11:18,850 --> 00:11:23,110 Know we see these these things around our Milky Way. We see them in other galaxy. 113 00:11:23,110 --> 00:11:26,980 Stars tend to explode every day, somewhere in the universe, somewhere in the universe. 114 00:11:26,980 --> 00:11:31,570 Every day star explodes, maybe destroys an entire planetary system. 115 00:11:31,570 --> 00:11:36,310 We find it lovely. But, you know, maybe, maybe a terrible thing for people there. 116 00:11:36,310 --> 00:11:40,240 For us, it's just astrophysics at this moment, right? 117 00:11:40,240 --> 00:11:49,330 And so that's how you make a stellar mass black holes in our Milky Way, or about 10 to 100 million of these stellar mass black holes. 118 00:11:49,330 --> 00:11:52,540 But if you go to the centre of the Milky Way, where you have millions of stars, 119 00:11:52,540 --> 00:12:00,700 you also make a lot of of of little black holes and they will tend to sink to the centre of they emerge together, make a bigger black hole. 120 00:12:00,700 --> 00:12:05,290 And that black hole will keep it. Creating more mature matter will fall and it will keep growing and growing. 121 00:12:05,290 --> 00:12:10,870 So in the centre of galaxies, you expect this big black hole's very massive one millions and we'll see later. 122 00:12:10,870 --> 00:12:15,790 See also billions of solar mass. But you know what? 123 00:12:15,790 --> 00:12:19,750 What makes the black hole so special? You know what's what is it doing and where does it come from? 124 00:12:19,750 --> 00:12:24,910 And why is it so important in the theory of general relativity and our understanding of science? 125 00:12:24,910 --> 00:12:32,320 Well, so let me walk you through and apologies to all of my physics colleagues here, but let's go through the understanding of what gravity is. 126 00:12:32,320 --> 00:12:42,520 And as you all know, gravity was invented in England. And so gravity with the idea was by Newton. 127 00:12:42,520 --> 00:12:45,400 Actually, that gravity is a force, OK? And it was. 128 00:12:45,400 --> 00:12:50,500 The story is that this was, you know, him seeing an apple falling down and wondering, why does the Apple fall? 129 00:12:50,500 --> 00:12:56,410 Historians say, Oh, we don't know where this story is true, and I was trying to look it up and find out why they don't like it. 130 00:12:56,410 --> 00:13:05,410 It turns out they don't like it because it sounds too nice. OK, so I think there's not much that I assume is actually probably not totally wrong. 131 00:13:05,410 --> 00:13:11,420 So I thought he thought Apple falling down. He thought there has to be a force that makes apples fall down all the time on a straight line. 132 00:13:11,420 --> 00:13:17,230 OK. And that's you can use and describe the motion of planets around the Sun perfectly. 133 00:13:17,230 --> 00:13:23,190 Well, OK, that's a wonderful. But then, of course, in the 19th century, there was a bit of a problem. 134 00:13:23,190 --> 00:13:28,390 You know, astronomers were measuring again planets, and then the mercury was going around the Sun, 135 00:13:28,390 --> 00:13:32,620 but it wasn't doing exactly in the way was predicted by Newton. 136 00:13:32,620 --> 00:13:36,160 In fact, it was. It was. It was, you know, the orbit was processing a little bit. 137 00:13:36,160 --> 00:13:46,210 So how little is this? Well, if you have a cake, right, you cut it up in pieces and the the thing that it was cut wrong was by the size of a hair. 138 00:13:46,210 --> 00:13:49,480 So that's how wrong and quote unquote, this was. 139 00:13:49,480 --> 00:13:53,230 So some astronomers were obsessed with this little hair found in a cake. 140 00:13:53,230 --> 00:14:02,110 OK, but turns out that was the path towards a deeper inside, which which meant there needs to be a new theory to explain this better. 141 00:14:02,110 --> 00:14:07,570 And the theory came with Albert Einstein just describing that as saying that gravity is not a force. 142 00:14:07,570 --> 00:14:12,490 It's a property of space and time. It's a property of space. 143 00:14:12,490 --> 00:14:21,010 That space itself is not a flat, a flat, flat space, but space itself can be curved. 144 00:14:21,010 --> 00:14:24,910 Well, we have a hard time understanding that, you know, how can how can space be curved? 145 00:14:24,910 --> 00:14:27,730 So we always picture this in two dimensions. 146 00:14:27,730 --> 00:14:35,410 OK, so you picture a two dimensional surface, which which is represent three dimensional space and you have a mass in it. 147 00:14:35,410 --> 00:14:42,510 What we'll do if you put a mass onto a blanket, for example, and will create a little dip in it. 148 00:14:42,510 --> 00:14:48,430 Now, if you have a lot of mass, then you create a very deep hole, so to speak. 149 00:14:48,430 --> 00:14:57,400 And so in this case, if you have something like a black hole or a mass, the Apple will just follow the curved space time. 150 00:14:57,400 --> 00:15:02,530 We'll just follow the shortest way towards, well towards the bottom. 151 00:15:02,530 --> 00:15:10,600 Now, if you have a ball rolling on this, you know this this curved space time, you see how people deflect it again. 152 00:15:10,600 --> 00:15:14,560 Fall off, follow the the shortest path, so to speak. 153 00:15:14,560 --> 00:15:21,010 In order to not fall into this hole, it has to go into this orbit, OK, and it has to go with a certain speed. 154 00:15:21,010 --> 00:15:27,280 If it doesn't go fast enough, it will just roll inside, OK, and it has to have a certain speed to do this. 155 00:15:27,280 --> 00:15:36,280 And the deeper it is in this eye, looking for the English word for it, for 3-D in German is stricter than that of the funnel. 156 00:15:36,280 --> 00:15:41,290 It's still fun. OK, good. It's funny. I was avoiding this word for the last two sentences. 157 00:15:41,290 --> 00:15:45,160 OK, so it's going down in the funnel and this funnel and your speed has to go faster. 158 00:15:45,160 --> 00:15:50,620 OK, it goes faster because it's the the the the curvature is much, much deeper. 159 00:15:50,620 --> 00:15:52,280 So it has to go faster to survive, right? 160 00:15:52,280 --> 00:16:00,820 It's like these these motorbikes, which go on and on the wall ride, you have to go very fast to actually not fall off of the wall. 161 00:16:00,820 --> 00:16:07,570 And so you know what happens? And it's described as a simple wall that the velocity with which you have to go around 162 00:16:07,570 --> 00:16:13,580 in the classical picture is a square word of the gravitation constant times the mass. 163 00:16:13,580 --> 00:16:17,380 Divided by the radios with which you rotate, 164 00:16:17,380 --> 00:16:25,840 which means that if you go to a smaller and smaller orbit around the star or black hole is this velocity will go up. 165 00:16:25,840 --> 00:16:33,460 The smaller the distances, the faster is the speed, and you can picture that at some point you have to go with the speed of light. 166 00:16:33,460 --> 00:16:40,660 OK, so this is here a certain distance where you go with the speed of light and that's happening here in this picture there, 167 00:16:40,660 --> 00:16:47,470 which you call the event horizon. So it goes here with a speed of light and, well, it's a cloud. 168 00:16:47,470 --> 00:16:51,760 Not because it's torn apart because it just forbidden. 169 00:16:51,760 --> 00:16:57,640 OK, sure. Claims that you're not allowed to go faster than the speed of light if you have any mass whatsoever. 170 00:16:57,640 --> 00:17:02,560 In fact, this is not something that that on the ancients, that it's just something we measure. 171 00:17:02,560 --> 00:17:15,920 That's sort of a speed of light is sort of a constant, which is which is a very fundamental property of our universe. 172 00:17:15,920 --> 00:17:23,750 Now, and so something's got to happen here, because, you know, if you're what was the speed of light, you know, some something got to go wrong. 173 00:17:23,750 --> 00:17:27,450 And what's what's happening there? Well, that's picture now light itself. 174 00:17:27,450 --> 00:17:31,580 So I said before was that light is really the only constant we have, so to speak. 175 00:17:31,580 --> 00:17:39,140 You know, the speed of light is the only constant. That's what we measure. Really, light always goes with the same speed. 176 00:17:39,140 --> 00:17:45,530 Know how fast you move where you are. You always measure speed of light being the same number. 177 00:17:45,530 --> 00:17:53,360 OK, now what happens here? Light goes through the curved space time, and it has to follow the shortest path again, 178 00:17:53,360 --> 00:17:58,050 and which means the shortest path is going on a curved trajectory. OK. 179 00:17:58,050 --> 00:18:03,550 And of course, it has to travel more space, so to speak with the same speed. 180 00:18:03,550 --> 00:18:11,050 So something else needs to change while speed is kilometres per hour or something, he is like miles for something else. 181 00:18:11,050 --> 00:18:18,070 And and so if you have more space, same speed time has to change. 182 00:18:18,070 --> 00:18:22,090 OK. And that's what you see here. You know, you have like a clock. Bang, bang, bang, bang. 183 00:18:22,090 --> 00:18:26,890 And here suddenly time will go slower. OK. 184 00:18:26,890 --> 00:18:31,420 Suddenly. Also, time needs to change, and that's a very crazy conclusion. 185 00:18:31,420 --> 00:18:40,570 I think, you know, this Einstein guy was really crazy, right to go out there and say that time would go slower if you are near a massive body. 186 00:18:40,570 --> 00:18:46,720 It's really quite a significant claim. Well, it turns out all of you were making use of this every day, not every day. 187 00:18:46,720 --> 00:18:52,090 But at least, you know, if you if you use a navigation system to come here, if you use a navigation system, 188 00:18:52,090 --> 00:18:59,080 you actually compare the arrival time of radio signals from satellites that that are far further away from Earth, 189 00:18:59,080 --> 00:19:05,600 so their time goes a little bit faster. In fact, thirty eight microseconds a day. 190 00:19:05,600 --> 00:19:12,550 That's how how fast flux, how much clocks go faster than here on Earth, simply because of that effect. 191 00:19:12,550 --> 00:19:20,440 And if you don't correct the GPS system for this time off set, you'd be off by 10 kilometres after just one day. 192 00:19:20,440 --> 00:19:23,680 So all of you, if you ever use a GPS system, make use of the theory. 193 00:19:23,680 --> 00:19:29,860 If Einstein, this crazy result that the astronomers made 100 years ago was with Mercury. 194 00:19:29,860 --> 00:19:35,380 So it's, you know, it's become commonplace. You know, you make use of the fact that time runs differently. 195 00:19:35,380 --> 00:19:42,010 But of course, this is only happening in the vicinity of Earth. You know that you have this little change of time, a very tiny change. 196 00:19:42,010 --> 00:19:47,380 What happens if you are near a black hole? Well, like then if you have a diamond strike, so to speak, 197 00:19:47,380 --> 00:19:55,180 goes down here and you see the time of go slower and slower and turns out actually here, it looks like time will come to a standstill. 198 00:19:55,180 --> 00:20:03,040 It will go so slow seen from the distance. That time seems to stop here at this point that we call the event horizon. 199 00:20:03,040 --> 00:20:09,160 And the second effect is that if you if you are here as a light, you want to get out again. 200 00:20:09,160 --> 00:20:13,810 OK? But what do you have to do? You have to go with the speed of light. 201 00:20:13,810 --> 00:20:18,940 Well, that's OK. But you have to go if you are beyond this point, faster than the speed of light. 202 00:20:18,940 --> 00:20:23,800 And that's not allowed. OK, now we are on the highways, know we like to go a little bit faster sometimes. 203 00:20:23,800 --> 00:20:27,850 Some of you do it. Not everybody, but some of you do OK. We think that's OK. 204 00:20:27,850 --> 00:20:31,180 But your flight, that's absolutely not OK. They will not do this. 205 00:20:31,180 --> 00:20:36,250 This means that, you know, everything that goes beyond this point will never be able to come back. 206 00:20:36,250 --> 00:20:41,830 Matter will not be able to come back. Light will not be able to come back and everything else. 207 00:20:41,830 --> 00:20:48,960 Any information, any form of communication will not be able to come back either, because everything we do is radio waves is just light. 208 00:20:48,960 --> 00:20:52,680 Yeah, if you use your text message, sorry, I'm in a black hole. 209 00:20:52,680 --> 00:20:58,320 You know, I do it, we'll use radio waves. They will not get out because it's radio light. 210 00:20:58,320 --> 00:21:02,280 OK, so that's what we call this event horizon, because every event, 211 00:21:02,280 --> 00:21:09,670 everything that happens beyond this point is not observable fundamentally based on the theory of of of all the attention. 212 00:21:09,670 --> 00:21:15,010 One last point is OK. You can just measure how you can calculate from the formula how big this is. 213 00:21:15,010 --> 00:21:21,280 This is about, you know, one half kilometres, I guess it's about one mile for a black hole of one solar mass. 214 00:21:21,280 --> 00:21:28,510 OK, typical black holes are sort of 10 solar masses. I'm sorry, about 10 miles radius for a black hole. 215 00:21:28,510 --> 00:21:31,330 That's a small, small thing, but they are black holes. 216 00:21:31,330 --> 00:21:38,800 As I said at the centre of Milky Way, which are sometimes millions and millions of billion times of the the mass of the Sun. 217 00:21:38,800 --> 00:21:46,820 And they would be the size of 150 million kilometres. That is the distance from the Earth to the Sun. 218 00:21:46,820 --> 00:21:51,980 OK. Or even the size of the entire solar system could be a black hole just for fun, 219 00:21:51,980 --> 00:21:56,580 just for students who can also calculate what is the average density you need to make a black hole. 220 00:21:56,580 --> 00:21:59,930 You know, essentially, how much matter do I need? What's the density of matter? 221 00:21:59,930 --> 00:22:03,350 I need to fill the the Earth's orbit with it? 222 00:22:03,350 --> 00:22:09,650 Just take the maths divided by by its radius. You get you get three mass divided by the volume. 223 00:22:09,650 --> 00:22:14,090 The volume is set by this number. I give you certain density well for still a massive black hole. 224 00:22:14,090 --> 00:22:19,370 It's sort of it's huge, right? So it's a 10 to 13 kilograms per cubic centimetre. 225 00:22:19,370 --> 00:22:24,230 OK, so this this little thing, you have 10 to 13 kilograms. 226 00:22:24,230 --> 00:22:29,750 But if you go to a Solar System sized black hole, well, you only need to fill it with water. 227 00:22:29,750 --> 00:22:33,470 So it's one gram per cubic centimetre more or less, so you can fill it with water. 228 00:22:33,470 --> 00:22:39,710 So it doesn't have to be exotic. You know, if you if you if you if you if you're not careful, do you go on vacation? 229 00:22:39,710 --> 00:22:43,580 You don't turn off your faucet. You, you feel the solar system with water. 230 00:22:43,580 --> 00:22:50,110 You turn into a black hole. So please be careful next time. But you know, that's so it doesn't have to be exotic. 231 00:22:50,110 --> 00:22:55,040 That's the important point. Of course, you know, the water will collapse. It will collapse into a point, become much more dense. 232 00:22:55,040 --> 00:22:58,760 But what will happen to you if you go to a black hole? 233 00:22:58,760 --> 00:23:02,870 OK, so if it's a stellar mass black hole, you know you are happy you face here. 234 00:23:02,870 --> 00:23:08,450 You go to a black hole, you're still a happy face because exciting, of course. And then you go to this this phase. 235 00:23:08,450 --> 00:23:09,230 Well, what now happened? 236 00:23:09,230 --> 00:23:17,750 You go into this curved space time and that's a significant curvature along your body, which means your feet are attracted a bit more than your head. 237 00:23:17,750 --> 00:23:21,800 OK. So are you really being stretched a little bit? You go very close to the black hole. 238 00:23:21,800 --> 00:23:25,160 You're really being spaghetti fight. OK, your turn into a long spaghetti. 239 00:23:25,160 --> 00:23:29,620 OK, so not a pleasant experience, or even not not smile anymore at this point. 240 00:23:29,620 --> 00:23:36,700 Unless you go to a supermassive black hole, so if you ever think about going to a black hole, OK, so my advice go to a supermassive black hole, OK? 241 00:23:36,700 --> 00:23:42,280 Because why? Because you are tiny. No, you tiny. You know you just one person compared to the size of the Solar System. 242 00:23:42,280 --> 00:23:46,820 You go in there. You know, even this little dot here will not experience much bigger edification. 243 00:23:46,820 --> 00:23:50,320 You can go into safely into a black hole and enjoy the rest of your life. 244 00:23:50,320 --> 00:23:56,710 Of course, you will never be able to tell anybody what you're going to see. So but that is possible. 245 00:23:56,710 --> 00:24:05,320 I mean, the size of a human, you know, compared to this, this this massive black hole is like the size of a human cell compared to the entire Earth. 246 00:24:05,320 --> 00:24:10,090 So this if you picture yourself relative to this, this massive black hole. 247 00:24:10,090 --> 00:24:14,020 OK, so now we understood what a black hole is. And the next question is, how do we see it? 248 00:24:14,020 --> 00:24:18,190 Well, of course, if you wanna see something, you need light, so you shine light on a black hole. 249 00:24:18,190 --> 00:24:19,030 And that's what you see here. 250 00:24:19,030 --> 00:24:27,040 You shine light, shine light at the black hole and light will be deflected and we're going rather peculiar in orbit, right? 251 00:24:27,040 --> 00:24:30,880 So light will go here. Actually, here even goes back around the black hole. 252 00:24:30,880 --> 00:24:35,570 Why is this? Well, because in this case, the black hole is even rotating and it rotates. 253 00:24:35,570 --> 00:24:40,030 It will actually take space with it. OK, so even space doesn't isn't fixed any more. 254 00:24:40,030 --> 00:24:49,150 Space starts to rotate, so it's like having an eddy in in water, right propeller and water, and you go the left side and then you turn back. 255 00:24:49,150 --> 00:24:53,020 Even light has to do this. It will disappear in this black hole. 256 00:24:53,020 --> 00:24:57,490 You also see the colour will change. It's blue and then it turns red. So why is this? 257 00:24:57,490 --> 00:25:00,850 Well, this is light coming from the edge of the black hole not yet disappeared, 258 00:25:00,850 --> 00:25:04,330 so it has to run up the hill right in this curved space that has to run up the hill. 259 00:25:04,330 --> 00:25:09,400 And so if you do this, you turn red, as you all know, and at the same, almost the same principle. 260 00:25:09,400 --> 00:25:15,790 Here it turns red because it loses energy and cost energy to climb up into this way from 261 00:25:15,790 --> 00:25:22,000 this black hole and so light that loses energy becomes redder and redder with this time. 262 00:25:22,000 --> 00:25:26,800 Now this actually go back all back to in fact, papers from 1916. 263 00:25:26,800 --> 00:25:32,350 In fact, a lecture from David Hilbert in 1916 who actually described for the first time how light is being bent. 264 00:25:32,350 --> 00:25:39,910 I find this quite amazing. 1915 Albert Einstein derived the theory of general relativity. 265 00:25:39,910 --> 00:25:46,120 Just a few months later, uh, Schwarzschild derived the metric. 266 00:25:46,120 --> 00:25:49,990 How did the curvature of spacetime would look like for something that is as a black hole? 267 00:25:49,990 --> 00:25:54,250 And Hilbert described how light would be bent within a few months or within a year. 268 00:25:54,250 --> 00:26:01,600 Everything was settled. It just took another hundred years to understand what it actually meant and to measure it. 269 00:26:01,600 --> 00:26:07,120 And he, you know, he described particular this effect you come with light and then actually there is a particular distance from 270 00:26:07,120 --> 00:26:12,370 the black hole where light is bent and will actually go into a circle actually will go into a close circle. 271 00:26:12,370 --> 00:26:15,460 That's quite an amazing thing. So if you were supposed to be standing here, 272 00:26:15,460 --> 00:26:23,080 this is a the event horizon and you managed to survive outside of a black hole and you're standing here looking in that direction. 273 00:26:23,080 --> 00:26:28,330 You see yourself standing in front of you, as you were like three weeks ago, right? 274 00:26:28,330 --> 00:26:34,360 Because it takes now for the big one black hole to take three weeks to go around the black hole and and see you. 275 00:26:34,360 --> 00:26:37,150 So that's what you would see. 276 00:26:37,150 --> 00:26:45,580 Which also means that all light coming from a certain set from a certain distance will actually go around or actually disappear in the very centre. 277 00:26:45,580 --> 00:26:51,820 Well, explain in trying to explain the centre of the Milky Way in the in the in the early the late 90s, 278 00:26:51,820 --> 00:26:55,660 we realised that radio emission would come from very close to the black hole. 279 00:26:55,660 --> 00:27:02,560 So there is light, you know, in darkness, in the darkness, so that black holes can be very bright because that folds in, 280 00:27:02,560 --> 00:27:08,290 it radiates stuff actually even managed to escape before it enters. 281 00:27:08,290 --> 00:27:13,450 And that will shine a light at this black hole. And it turns out what you will see is a hole. 282 00:27:13,450 --> 00:27:18,820 OK. Not a surprise. But actually, that hole is actually significantly larger than the event horizon. 283 00:27:18,820 --> 00:27:25,840 Because a black hole is a big lens, it will actually magnify itself. It makes itself appear bigger than it actually is. 284 00:27:25,840 --> 00:27:29,590 And turns out that that size here is proportional to the mass, 285 00:27:29,590 --> 00:27:37,270 and it's actually the diameter is 10 times actually the event horizon six or five times, depending on whether it's rotating or not. 286 00:27:37,270 --> 00:27:45,550 And that that shadow side to be called it the shadow of black hole is is almost is there all the time? 287 00:27:45,550 --> 00:27:51,730 Whenever you do, you have a different light in different coming from different models. 288 00:27:51,730 --> 00:27:56,530 You always have this, uh, the shadow, and you tend to alter how these rings, right? 289 00:27:56,530 --> 00:27:57,850 So it's one of the predictions we made. 290 00:27:57,850 --> 00:28:06,160 You see tend to see a ring like a half a ring because the light bend around with a certain diameter and with a clear prediction. 291 00:28:06,160 --> 00:28:11,980 If you look at a black hole light coming from a black hole, you should be able to see it. 292 00:28:11,980 --> 00:28:17,080 You also said you need to take a technology which was known very long baseline to fragmentary. 293 00:28:17,080 --> 00:28:19,960 I'll explain in a moment what that is at a certain frequency. 294 00:28:19,960 --> 00:28:24,460 To actually do this, then you would be able to see the event horizon would be able to see that shadow. 295 00:28:24,460 --> 00:28:29,170 So that was 19 years ago, and at the time I was actually telling, in fact, the BBC. 296 00:28:29,170 --> 00:28:36,750 And other almost 10 years, we'll be able to see that black hole, if you're that guy, called me up after 10 years and we haven't done that yet. 297 00:28:36,750 --> 00:28:39,540 But he kept calling me. I told you we are going and getting closer. 298 00:28:39,540 --> 00:28:44,590 And he actually called me every year and told the BBC that one of the first ones to report on that result, 299 00:28:44,590 --> 00:28:48,250 when it finally came out, it was still the same reporter that cover that one. 300 00:28:48,250 --> 00:28:54,360 So it's quite amazing. So anyway, so we do better modelling these days. 301 00:28:54,360 --> 00:29:02,070 And what you see here is the former supercomputer simulation. So we start now where we have matter around a black hole we seeded with magnetic field. 302 00:29:02,070 --> 00:29:06,480 These rings are magnetic fields. We like the material matter rotate. 303 00:29:06,480 --> 00:29:11,910 The magnetic fields will be stretched and as another form of gratification that will happen, 304 00:29:11,910 --> 00:29:16,200 these magnetic fields, which are in this matter, will be turned into a spaghetti bowl. 305 00:29:16,200 --> 00:29:24,000 OK, you you'll it further rotate and then magnetic field will pile up and actually will shoot up along the rotation axis. 306 00:29:24,000 --> 00:29:30,420 So we see how matter creates how it rotates, and we see the magnetic field inside, we see it shooting out. 307 00:29:30,420 --> 00:29:35,730 And that's in fact a phantom phenomenon that we see throughout the entire universe. 308 00:29:35,730 --> 00:29:42,840 It's called the cold jets. Now, the next step you have to do is you have to see how has a gradient. 309 00:29:42,840 --> 00:29:47,760 And so what we're doing here is actually this is more this is actually a very accurate simulation, 310 00:29:47,760 --> 00:29:54,960 with light bending included to calculate how light is where it's created, where it's absorbed, how it's bend around. 311 00:29:54,960 --> 00:29:59,340 And you see sort of you saw that that jet shooting out, you see, it's actually glowing. 312 00:29:59,340 --> 00:30:04,290 Now I have to tell you one thing and I have to, you know, one thing actually, black holes are not red. 313 00:30:04,290 --> 00:30:09,370 OK, I show you that. You know, you see at night, it looks like a volcano is very dangerous. 314 00:30:09,370 --> 00:30:18,090 OK, but what we're looking here is, is many radio frequencies. OK, so radio, as I said, is light, but you cannot see it with your naked eyes. 315 00:30:18,090 --> 00:30:22,890 OK, so we have to translate it into our eyes. We have to give it a colour. 316 00:30:22,890 --> 00:30:26,250 And so it's on this prediction. In 2019, we made it red. 317 00:30:26,250 --> 00:30:34,290 And because before that, the the radar astronomers would use rainbow colours for four for representing radio images. 318 00:30:34,290 --> 00:30:40,320 And I thought black holes are not sounds like a happy place, but black hole is not a happy place right now. 319 00:30:40,320 --> 00:30:45,240 So you have to use another colour scheme. So we use threat. And so that's that's the only secret, right? 320 00:30:45,240 --> 00:30:53,490 So we know it's not a deep physical reason. It's just, you know, some artistic choice that you make, but it's stuck. 321 00:30:53,490 --> 00:31:01,740 And so you see this simulation, which actually you can do in this virtual reality general relativistic retracing three 322 00:31:01,740 --> 00:31:06,470 dimensional general versus magnetic magnetic magnet Magneto hydrodynamics simulation. 323 00:31:06,470 --> 00:31:15,090 So it's a lot of physics in this one simulation. And I was talking about these, these checks, and in fact, as I said, they are seen in nature. 324 00:31:15,090 --> 00:31:19,230 And so there is this one source which is now very popular, very well known, 325 00:31:19,230 --> 00:31:25,980 called M87 M87, because it's messier catalogue of messier, uh, number eighty seven. 326 00:31:25,980 --> 00:31:30,710 So messier in the centre of Paris was, you know, in the centre of Paris, and a 19th century could still do this. 327 00:31:30,710 --> 00:31:35,730 It was an optical telescope with charge of the sky and would see this nebula at the time. 328 00:31:35,730 --> 00:31:40,230 We wouldn't even know we would not even know these were galaxies. We're just nebula. OK. 329 00:31:40,230 --> 00:31:49,530 And then Heber Curtis in 1980 in the US found a little streak of light in the very centre again year to two years after, you know, uh, 330 00:31:49,530 --> 00:31:58,350 short shields and, uh, an Einstein also formulated the basics of black holes and astronomer found a little streak of light there. 331 00:31:58,350 --> 00:32:01,770 OK. Didn't know what what it was. Didn't know it was a galaxy. 332 00:32:01,770 --> 00:32:05,490 It, you know, it didn't even know that this streak of light would point right at the black hole. 333 00:32:05,490 --> 00:32:11,460 That these other theories that just found. Again, it took another fifty years to connect these things and put them together. 334 00:32:11,460 --> 00:32:15,300 That still makes me think that, you know, as astronomer, we sometimes see crazy things. 335 00:32:15,300 --> 00:32:23,330 And maybe that's exactly the place where, you know, a theoretical physicist has to look to understand, you know, something fundamental about nature. 336 00:32:23,330 --> 00:32:31,130 The good thing about this source is so it has these jets, so there's something happening and actually it's suspected to be a supermassive black hole. 337 00:32:31,130 --> 00:32:35,870 People were measuring the mass when I did my Ph.D. the maths was two billion solar masses, 338 00:32:35,870 --> 00:32:41,960 two billion, you know, two times 10 of the nine that's huge was still too small. 339 00:32:41,960 --> 00:32:48,120 OK, well, still too small to be seen with the technology that we have. Then it became three billions, but still too small. 340 00:32:48,120 --> 00:32:53,900 OK, but then it was another measurement. You said six billion and then it was potentially possible. 341 00:32:53,900 --> 00:33:01,010 OK. And so we looked at this source as well, and that was a big shot in the dark, so to speak, was, you know, it was these measurements, right? 342 00:33:01,010 --> 00:33:08,570 We simulate these jets. Now, this year is looking at the same simulations, but now at one radio frequency, 343 00:33:08,570 --> 00:33:13,640 at eighty six gigahertz, three millimetre wavelength, you see this naive plasma going out. 344 00:33:13,640 --> 00:33:15,650 It actually look like an hourglass. 345 00:33:15,650 --> 00:33:22,340 And if you if you look at astronomical images that were made a similar frequency as you would see actually how its edge brightened and, 346 00:33:22,340 --> 00:33:25,850 you know, resembles what we were modelling. 347 00:33:25,850 --> 00:33:30,980 And if you would then zoom in and go to the high frequency of 230 gigahertz, all the extender stuff fall away. 348 00:33:30,980 --> 00:33:36,500 It's like X-ray. You know, if you're going to choosing the right frequency means you x-raying to the right location. 349 00:33:36,500 --> 00:33:43,760 And if you go to this high frequency of two 30 gigahertz, you would actually X-ray to the region where light comes right from the event horizon. 350 00:33:43,760 --> 00:33:46,340 OK. And 2p bend and produce this ring. 351 00:33:46,340 --> 00:33:53,820 And so this is what we and I'm quite proud of this one as well, because we published this in 2016, a year before the observations were made. 352 00:33:53,820 --> 00:33:58,520 OK, it doesn't often happen unless you actually do a proper prediction in astronomy. 353 00:33:58,520 --> 00:34:03,590 OK, especially if it comes to an image, but this is basic predictions of air. 354 00:34:03,590 --> 00:34:09,770 And so that's what you expect. And some astrophysics that needs to go in there to actually find the right frequency. 355 00:34:09,770 --> 00:34:14,660 And so, you know, that was a prediction in 2016. You can calculate how big this is. 356 00:34:14,660 --> 00:34:19,790 Well, the size of this is 40 microseconds. OK, what's 40 microseconds? 357 00:34:19,790 --> 00:34:23,750 It's about the size of a mustard seed in Philadelphia, as seen from here. 358 00:34:23,750 --> 00:34:27,950 OK, so and then you can calculate how big a telescope do I need? 359 00:34:27,950 --> 00:34:35,150 You know, I know the frequency. And so the the resolution of a telescope is given by the wavelength divided by the size. 360 00:34:35,150 --> 00:34:39,410 The wavelength is given. It's one millimetre. How big does the size have to be? 361 00:34:39,410 --> 00:34:45,440 What has to be the size of the Earth? OK, so you need a telescope the size of the Earth to see that thing. 362 00:34:45,440 --> 00:34:52,330 So we build one. And that was called the Event Horizon telescope that she started already in the 90s, 363 00:34:52,330 --> 00:34:58,210 the technology of eye very long baseline interferometry, as I said, was already available, but not at these high frequencies. 364 00:34:58,210 --> 00:35:03,640 The first successful experiments were made here between Spain and France, 365 00:35:03,640 --> 00:35:09,890 and then in the US you had three telescopes coming together and then by combining telescope, 366 00:35:09,890 --> 00:35:15,250 he actually synthesised in the computer the virtual telescope with the size 367 00:35:15,250 --> 00:35:20,480 that is corresponding to the diameter or the separation of these telescopes. 368 00:35:20,480 --> 00:35:30,710 And in 2017, we made our first experiment. After many years of negotiations with which other we actually we were here able to do 369 00:35:30,710 --> 00:35:35,660 the first experiment with eight telescopes at six different mountains around the world. 370 00:35:35,660 --> 00:35:39,290 Why mountains? We have to go to dry, 371 00:35:39,290 --> 00:35:47,540 high site have little water vapour in the atmosphere as possible because these high frequencies millimetre waves absorbed by water vapour. 372 00:35:47,540 --> 00:35:58,760 So you have to go to dry places in Spain and Arizona, Hawaii, Mexico, to Chile, to telescopes here and the South Pole, even in the South Pole. 373 00:35:58,760 --> 00:36:05,120 And what you also need is good weather. Right, so you need to have good weather around the world. 374 00:36:05,120 --> 00:36:09,830 And so we are budgeting entire week because we're hoping at least one day will hopefully be OK. 375 00:36:09,830 --> 00:36:14,330 OK? And in the previous run, it was never, actually ever, always OK. 376 00:36:14,330 --> 00:36:19,100 You know, either telescope had failed or the weather was bad or, you know, nothing had ever worked. 377 00:36:19,100 --> 00:36:24,480 And now we had field. It's the biggest experiment, and we were hoping for some. Well, we started the first day. 378 00:36:24,480 --> 00:36:29,540 It was perfect weather. OK, second day, perfect weather. The third day. 379 00:36:29,540 --> 00:36:33,260 We're all tired. You know, actually, it's for a fourth day. 380 00:36:33,260 --> 00:36:41,090 We're tired. So we declare that bad weather and and then continued. 381 00:36:41,090 --> 00:36:44,780 And then essentially within within a week, we had all the data we wanted. 382 00:36:44,780 --> 00:36:49,130 We, we, we we recorded four petabytes of raw data and all these telescopes. 383 00:36:49,130 --> 00:36:56,480 The data was then shipped to the set to correlate to places where things were combined into a supercomputer to, 384 00:36:56,480 --> 00:37:01,500 you know, to to be further processed later. Took a little while to ship the data. 385 00:37:01,500 --> 00:37:05,370 I mean, you have to pack it really in hard drives, hard drives, you put it put in boxes, 386 00:37:05,370 --> 00:37:12,420 you put it on on mules and now actually on trucks or whatever, and you send it to a two central place course near the South Pole. 387 00:37:12,420 --> 00:37:18,090 You have to wait until the next morning so you can ship and take six months until the sun rises again. 388 00:37:18,090 --> 00:37:27,210 So I took a little while to get all the data together. These are here the telescopes in Mexico, Hawaii, Arizona, Spain, the South Pole in Chile. 389 00:37:27,210 --> 00:37:32,080 I just point out some of my students here, but you're young than you did. The calibration work later. 390 00:37:32,080 --> 00:37:39,510 They moved to L.A., who actually was the project manager of Ph.D. Sara is our own Frank Woolhouse, who actually she she, you know, 391 00:37:39,510 --> 00:37:49,440 she did the again led one of the calibration papers and faked that to simulate the observations, she's quoted the ALMA data processing. 392 00:37:49,440 --> 00:37:52,980 And I was having fun here at the expense I the which. 393 00:37:52,980 --> 00:37:59,490 And then the South Pole, of course, as that you have to have some dedicated staff will stay there for for a longer time. 394 00:37:59,490 --> 00:38:05,080 This is yeah, this was actually observations here, this was before and this was after it was really tiring, 395 00:38:05,080 --> 00:38:10,350 I should say high elevation and then observing all night. 396 00:38:10,350 --> 00:38:19,320 This is the equipment here. You see, actually these boxes, I have hard drives in them eight eight hard drives with six or eight terabytes each, 397 00:38:19,320 --> 00:38:24,120 which you record with 32 gigabits per second always being asked, Why don't you send it over the internet? 398 00:38:24,120 --> 00:38:29,400 Well, I'll try to send 32 gigabits per second from the South Pole to a central location that's not going to work. 399 00:38:29,400 --> 00:38:35,140 So there's no internet. That's a few kilobytes per second, actually. Most of the time. 400 00:38:35,140 --> 00:38:42,820 You have atomic clocks at each telescope and some, some electronic equipment. 401 00:38:42,820 --> 00:38:52,510 Now for the experts, what we measure is actually a correlation coefficient which are OK just for the rate astronomers. 402 00:38:52,510 --> 00:38:59,650 This is what we really measure the visibility amplitude as a function of baseline. How strong are two telescopes correlated? 403 00:38:59,650 --> 00:39:06,220 And what you measure is the Fourier transform of the image in one dimension. And what you see here goes to zero and goes to zero here. 404 00:39:06,220 --> 00:39:11,770 Why do I show this? Well, that's essentially essentially more or less the raw data and the dashed line 405 00:39:11,770 --> 00:39:16,790 is the model of a ring ring in the same representation would look like this. 406 00:39:16,790 --> 00:39:20,510 And so when when the first calibrated data came out, we didn't have an image whatsoever. 407 00:39:20,510 --> 00:39:24,520 We just looked at the raw data. We saw this going down, going up and going down again. 408 00:39:24,520 --> 00:39:27,940 We thought, Well, it's going to be interesting, OK? We didn't have an image. 409 00:39:27,940 --> 00:39:39,260 We just did sort of a 40 transform. That's a mathematical transformation in our head and we're tantalised and then we start imaging. 410 00:39:39,260 --> 00:39:46,060 Now, how does the imaging work? The parameter? So you have two telescopes, and the work essentially is a set interferometer. 411 00:39:46,060 --> 00:39:51,520 Radio waves come in play in parallel waves. You bring them to interference, you measure interference pattern. 412 00:39:51,520 --> 00:39:57,220 And depending on where the source comes from, that interference pattern, changes and and so forth. 413 00:39:57,220 --> 00:40:01,330 And so if you have two telescopes, you see these waves and you have more telescope, 414 00:40:01,330 --> 00:40:06,340 you actually add up ways and the image will build up from the different perspective. 415 00:40:06,340 --> 00:40:12,280 So in this case, actually the image that we reconstruct with such a virtual telescope looks like a teapot. 416 00:40:12,280 --> 00:40:18,440 OK. OK, so it turns out Russell's teapot can be seen, after all. 417 00:40:18,440 --> 00:40:22,700 Well, you know this. And actually, this is not yet fully processed. 418 00:40:22,700 --> 00:40:27,910 What actually can can be made better. OK, so you buy it by combining all these different perspectives from different telescopes, 419 00:40:27,910 --> 00:40:32,320 you can recreate this virtual telescope and get some, some basic image. 420 00:40:32,320 --> 00:40:38,050 And that's what we did for the real data, of course. And I'll I'll have a few moments that explain you how we did this. 421 00:40:38,050 --> 00:40:44,210 But now I assure you the results first, you know, we actually did many years work on this, 422 00:40:44,210 --> 00:40:51,620 and then we have this press conference in Washington and in Brussels where we presented this and we showed this, this zoom actually into M87. 423 00:40:51,620 --> 00:40:57,280 And I think that just relive this for for a short moment was actually the biggest zoom in astronomy, 424 00:40:57,280 --> 00:41:05,190 and we're having a Zoom factor of one billion, OK? We're starting at the old sky looking towards Virgo. 425 00:41:05,190 --> 00:41:13,210 And then, yes, the sun by the music was made by my son, by the way, he was making film music. 426 00:41:13,210 --> 00:41:16,830 And OK, so we're zooming into the direction of Vega. 427 00:41:16,830 --> 00:41:25,380 And what you first see is the the radio image at lower frequencies is made with a low telescope, which actually is all over Europe. 428 00:41:25,380 --> 00:41:34,530 This one, actually, as I said, you know, England is involved in this and this, this gas is put out by this, this jet here. 429 00:41:34,530 --> 00:41:45,040 And then you zoom into this jet as you get closer and closer to real data, you get closer. 430 00:41:45,040 --> 00:41:48,900 And then you see this this structure, and that's what we got out in the end, you see, 431 00:41:48,900 --> 00:41:52,570 you know, you look at the source with many different ways for different telescopes. 432 00:41:52,570 --> 00:41:58,990 You always see this jet chitchat and only when you go to this high frequency, you suddenly see that ring. 433 00:41:58,990 --> 00:42:01,570 It's on a fundamentally different from everything we've seen before, 434 00:42:01,570 --> 00:42:06,080 but it's exactly what we have predicted at this frequency and that was the magic of it. 435 00:42:06,080 --> 00:42:11,350 So we saw that the first time, you know, you see this data, you see the first image and gosh, 436 00:42:11,350 --> 00:42:16,390 you see the ring look like you always imagined in your dreams. 437 00:42:16,390 --> 00:42:24,070 And that's the beauty of physics. Sometimes it works, and most of the time, you know, in our eyes, it doesn't. 438 00:42:24,070 --> 00:42:25,330 And you have to figure out why. 439 00:42:25,330 --> 00:42:31,420 And as you said, it was actually it made the news and we were really stunned by how much it resonated with the general public. 440 00:42:31,420 --> 00:42:36,520 You know, it was really the front page news all over the world, as you said. 441 00:42:36,520 --> 00:42:42,760 Of course, social media went went crazy. 442 00:42:42,760 --> 00:42:49,390 Certainly, like cats, cats are popular on social media, cats and black holes receive a really, really big prise. 443 00:42:49,390 --> 00:42:54,640 Everybody was raving about this. I was, I was, you know, why am I saying? 444 00:42:54,640 --> 00:42:58,340 I learnt I was sort of trending online geek when I looked up? What nine degrees? 445 00:42:58,340 --> 00:43:04,210 I wondered whether I want to be there, but it's all the bad jokes come from there from this website. 446 00:43:04,210 --> 00:43:10,450 So you don't know what all the everybody below 18 knows it. So. 447 00:43:10,450 --> 00:43:16,210 And so briefly, how we made that image in the first place. The first step was that we actually blindly gave the data. 448 00:43:16,210 --> 00:43:22,870 It was calibrated on calibrate sources. We first calibrated not on this source, but we calibrated on quasars. 449 00:43:22,870 --> 00:43:29,050 Then we calibrated on the source by small group. We gave it to four independent teams and international national teams. 450 00:43:29,050 --> 00:43:36,400 This was a team where we were involved as a thorough again frank, an Asian and American colleagues and independently of each other. 451 00:43:36,400 --> 00:43:42,400 They should, you know, use preliminary calibrated data and make images in all of them found again a ring. 452 00:43:42,400 --> 00:43:49,660 It wasn't quite as nice as the final product, but independently of each other, we found more or less the same same structure. 453 00:43:49,660 --> 00:43:52,780 OK. And then we started all over again. Then we send it. 454 00:43:52,780 --> 00:44:00,670 We submitted, we compared an all all use different methods and we start all over again with actually simulated data. 455 00:44:00,670 --> 00:44:07,870 In fact, before that, we had imaging challenges. So people were giving images, which was with simulated data, and they had to reconstruct them. 456 00:44:07,870 --> 00:44:14,290 Sometimes there was a snowman, sometimes there was a ring, sometimes they was an OK and they had to show that their methods work. 457 00:44:14,290 --> 00:44:22,240 And then we used sort of we pick three methods. We started with something that had basic properties of our data, but was not all. 458 00:44:22,240 --> 00:44:28,510 With a ring, there was a ring, a crescent shape, a disk or double source or here simulation. 459 00:44:28,510 --> 00:44:32,860 And then, you know, you had this different algorithms that should recover the basic structure. 460 00:44:32,860 --> 00:44:36,880 So this should always show some kind of a disk structure and not not a ring. 461 00:44:36,880 --> 00:44:40,570 So we did not use algorithms, which would always give you a ring that was important, 462 00:44:40,570 --> 00:44:44,290 you know, if it was a double structure and should give you a double structure. OK. 463 00:44:44,290 --> 00:44:52,620 And so then we we picked the ones, the algorithms and parameters that would reconstruct all these models equally well. 464 00:44:52,620 --> 00:44:59,370 OK, so we could have, you know, algorithms which work on this, which can perfectly reconstruct image rings, right? 465 00:44:59,370 --> 00:45:05,280 We could make nicer ring images, but we didn't want to do that. And so that's what we did. 466 00:45:05,280 --> 00:45:10,740 And then you had, you know, the final results from three different independent algorithms and they all got the ring. 467 00:45:10,740 --> 00:45:18,540 It all was brighter in on the bottom. OK. But you see, there are subtle differences between this, this algorithm and this algorithm. 468 00:45:18,540 --> 00:45:28,560 OK. It's bright here. It's not as bright there. So there's a certain uncertainty in this reconstruction, which which is just a limitation of our data. 469 00:45:28,560 --> 00:45:35,790 OK, so I saw on the internet, were people actually going to the final result and taking out like the subtleties and image processing? 470 00:45:35,790 --> 00:45:41,130 It just doesn't make any sense. And all the data has a certain limit to which it's accurate and reliable. 471 00:45:41,130 --> 00:45:47,430 It's certainly reliable to the fact that it's brighter on the bottom, and we can easily explain this by relativistic beaming. 472 00:45:47,430 --> 00:45:52,740 So if the gas goes around with the speed of light and when it goes towards you, 473 00:45:52,740 --> 00:45:56,340 it's actually the light gets an extra boost because you go with the speed of light. 474 00:45:56,340 --> 00:46:01,510 So it actually shines like a like a flashlight in your in your face when it goes away. 475 00:46:01,510 --> 00:46:05,880 Actually, you only see a fainter emission because it shines away from you. 476 00:46:05,880 --> 00:46:10,680 And so if it goes around with a speed of close to the speed of light, the stuff that goes towards you is brighter. 477 00:46:10,680 --> 00:46:16,680 The other half of the ring shines away from you is fainter. So that's exactly what we see here. 478 00:46:16,680 --> 00:46:22,440 But the details, you know, we don't know and we don't trust. By the way, this method here is 30 years old. 479 00:46:22,440 --> 00:46:25,970 The other ones are also pretty, pretty standard. 480 00:46:25,970 --> 00:46:32,270 And then we combine them and we looked at we had four different days and four different days, we've got the same results. 481 00:46:32,270 --> 00:46:36,680 OK. And so that really is what what convinced us and different different people, 482 00:46:36,680 --> 00:46:42,240 different algorithm, different days, always giving you more or less the same result. 483 00:46:42,240 --> 00:46:54,030 And that's what took us so, so long. In addition, we did more simulations, and so we did more super computer simulation, this is one here. 484 00:46:54,030 --> 00:46:57,700 You don't see all the details. Maybe you see here is see see stuff going around. 485 00:46:57,700 --> 00:47:02,470 You see this almost spiral wave going around, but you see also this ring, which is stable. 486 00:47:02,470 --> 00:47:07,990 And that's exactly the light that goes around a few times around the black hole that always gives you that ring. 487 00:47:07,990 --> 00:47:13,300 OK, and that's the stable feature. Sometimes it's much brighter sometimes and not quite as bright. 488 00:47:13,300 --> 00:47:17,820 And you see that actually changes the function of time. So the black hole will look different every day. 489 00:47:17,820 --> 00:47:23,650 Yeah, every every day. Well, a day in the life of a of a supermassive black hole actually is a few weeks here. 490 00:47:23,650 --> 00:47:30,110 So I for one a week, it should be stable, but over a month it should look slightly different. 491 00:47:30,110 --> 00:47:35,540 OK. And then we actually calculated many, many different black hole models changing the astrophysics, 492 00:47:35,540 --> 00:47:40,970 changing the maths of the ah sixty thousand images of black holes that we calculated with the accretion 493 00:47:40,970 --> 00:47:47,180 with a light bending and everything that's the biggest library of black hole images ever made. 494 00:47:47,180 --> 00:47:51,710 And all of them show this shadow and show the ring so that the basic prediction you know that we 495 00:47:51,710 --> 00:47:59,610 made 10 or 20 years ago is also borne out and supported by by these massive simulations now. 496 00:47:59,610 --> 00:48:07,980 Now we also took some of the best fitting ones, these are simulations, and then we run them through a simulated view of observation. 497 00:48:07,980 --> 00:48:16,470 So these are all everything is simulated here. The computer simulation of a black hole, then a computer simulation of a VLBI telescope. 498 00:48:16,470 --> 00:48:23,200 And they pretty much look exactly like what we find in reality. So that convinces us that we more or less do the right thing. 499 00:48:23,200 --> 00:48:29,860 For the for the astrophysicists, this is a counter-rotating, this is non-irritating, this is a maximally rotating black hole. 500 00:48:29,860 --> 00:48:33,940 They all give the same result. That's exactly the point I was making. 501 00:48:33,940 --> 00:48:41,050 The beginning right spin doesn't matter that much. It's the secondary effect. That's why we actually could make such a good prediction. 502 00:48:41,050 --> 00:48:45,190 You can also measure than the ring size, the width and from the width, as I said, 503 00:48:45,190 --> 00:48:52,120 we can derive the maths and the maths turned out to be six and a half billion solar masses exactly what had been predicted before. 504 00:48:52,120 --> 00:48:56,050 And that was sort of another confirmation that we're doing the right thing. 505 00:48:56,050 --> 00:49:01,510 And we also looking at how round is that image just unfolded and you see it actually pretty. 506 00:49:01,510 --> 00:49:05,440 It's a pretty straight line if you sort of unroll that image. 507 00:49:05,440 --> 00:49:11,140 It's circular to within 10 percent. That's another prediction. Actually, it should be circular to within 10 percent. 508 00:49:11,140 --> 00:49:20,200 That tells us that there are not additional parameters, for example, governing the black hole. 509 00:49:20,200 --> 00:49:23,530 Uh, yes. And if one other conclusion that we can draw from this. 510 00:49:23,530 --> 00:49:29,170 So from that, we we we actually, you know what we concluded, know all the tests we can do is this is real. 511 00:49:29,170 --> 00:49:31,270 This is determined by general relativity. 512 00:49:31,270 --> 00:49:36,820 We're looking if we look into this darkness, we're looking really into the darkness of the event horizon, OK? 513 00:49:36,820 --> 00:49:43,200 And what we're measuring is this photon related to the fortune of its effect. 514 00:49:43,200 --> 00:49:47,710 You also know that black holes were measured with gravitational waves maybe two years ago. 515 00:49:47,710 --> 00:49:52,950 You've seen the news here that was done at a different scale 60 solar masses. 516 00:49:52,950 --> 00:49:59,750 We measuring it six billion solar masses. But if you can derive the gravitational waves I actually made, that's easy. 517 00:49:59,750 --> 00:50:03,660 The the wobbling of space and time are made in exactly the same scale. 518 00:50:03,660 --> 00:50:07,090 They also made at this photon ring where the light, you know, with light goes around. 519 00:50:07,090 --> 00:50:13,410 That's also where gravitational waves are made more or less. And so you get a scale of 460 solar mass black holes. 520 00:50:13,410 --> 00:50:14,910 You get it for six billion solar masses. 521 00:50:14,910 --> 00:50:22,920 And we know that the scale of of this, uh, of black holes goes linear, linear with mass exactly as ancient predicted. 522 00:50:22,920 --> 00:50:27,030 So over a factor of 100 million, we just change the mass. 523 00:50:27,030 --> 00:50:29,790 We can explain the basic properties of these things. 524 00:50:29,790 --> 00:50:35,130 So it's as if you you have, like again, a human cell, the smallest human cell and Buckingham Palace. 525 00:50:35,130 --> 00:50:39,490 And the only thing that changes between them is just changing the mass how heavy they are. 526 00:50:39,490 --> 00:50:47,490 OK, it's all these, these, these, these size scales. And that's that's a very important, I think, confirmation of predictions of of jihad. 527 00:50:47,490 --> 00:50:53,100 What's next? There are some dreams about increasing the Event Horizon telescope, more telescopes. 528 00:50:53,100 --> 00:51:00,450 This is sort of here more telescopes in the Americas that doesn't add too much sort of adds a bit more robustness. 529 00:51:00,450 --> 00:51:09,900 We are thinking of putting a telescope here in Africa because if you look at this distribution of telescope there, Africa is the missing place. 530 00:51:09,900 --> 00:51:13,050 There's not a single telescope of that kind in all of Africa. 531 00:51:13,050 --> 00:51:19,170 And so that would help us to make more robust images, particularly for the centre of the Milky Way. 532 00:51:19,170 --> 00:51:23,670 We have a telescope actually available, it's actually in Chile right now, it's 50 metre in diameter. 533 00:51:23,670 --> 00:51:28,080 It's not being used anymore, so we can actually get it. We actually get it for free and that's all. 534 00:51:28,080 --> 00:51:32,610 We actually don't even have to pay for it. So we get it for free or or whatever you want. 535 00:51:32,610 --> 00:51:38,250 So they're happy that we take it. We can take that one. We actually replace everything in it. 536 00:51:38,250 --> 00:51:47,430 Well, actually, the half of the electronics in its capital will be completely new telescope once you move it and put it here to Namibia. 537 00:51:47,430 --> 00:51:54,870 The southwest of Africa, it's close to the telescopes in Chile, the same time zone, more or less with with Europe, with the other telescopes are. 538 00:51:54,870 --> 00:51:59,520 This is the second highest mountain in Namibia, two thousand three hundred metre high. 539 00:51:59,520 --> 00:52:05,550 It's just a fantastic table mountain. It's a three kilometre long 800 metres wide. 540 00:52:05,550 --> 00:52:09,120 If you're there, it's a very stay. That's the one of the problems here. 541 00:52:09,120 --> 00:52:14,550 We still have to upgrade the road. 542 00:52:14,550 --> 00:52:21,900 Well, we got up there this year, the drone flight and you see this enormous table table mountain and you look into its horizon everywhere. 543 00:52:21,900 --> 00:52:26,670 It's like you can see, right? You, as you see everywhere, is Horizon and the night sky. 544 00:52:26,670 --> 00:52:31,500 You know, I can tell you, it's just marvellous. I mean, this is the best place in the world to see. 545 00:52:31,500 --> 00:52:35,310 The night sky is no light pollution, everything. It's just you see the Milky Way. 546 00:52:35,310 --> 00:52:41,430 So clearly, it's just it's wonderful. We also couple this with an outreach programme. 547 00:52:41,430 --> 00:52:46,350 This is actually what you see. Here is a mobile planetarium that we actually use in the Netherlands. 548 00:52:46,350 --> 00:52:53,130 We go to schools in all the Dutch schools, actually get this mobile planetarium and get your show of the universe. 549 00:52:53,130 --> 00:52:57,960 And we're teaming up with a local NGO, which goes to local schools in Namibia. 550 00:52:57,960 --> 00:53:07,020 And we've done that and we've, you know, within a week, we, you know, we brought into 1300 1400 school kids. 551 00:53:07,020 --> 00:53:14,460 And so we are now starting next Monday, a crowdsourcing campaign to actually fund a planetarium for Namibia, 552 00:53:14,460 --> 00:53:23,160 which will go to all the schools in Namibia to get the school kids there excited about astronomy and tells them a little bit about the science. 553 00:53:23,160 --> 00:53:28,470 Uh, because we want to do this together with people in Africa and not just, you know, on our own. 554 00:53:28,470 --> 00:53:32,990 This has to be integrated think and astronomy is a great tool because we all share the same sky. 555 00:53:32,990 --> 00:53:38,010 Right. So everybody has the same experience when you look up into the sky. 556 00:53:38,010 --> 00:53:42,900 And of course, in the long run, we want to go to space. 557 00:53:42,900 --> 00:53:51,510 And this is a concept we submitted to ESA in a white paper where we have three three dishes in space on slightly different orbits. 558 00:53:51,510 --> 00:53:56,430 They orbit around the Earth, slightly different, uh, orbits. 559 00:53:56,430 --> 00:54:02,340 They will drift apart and then you measure all separations and all orientations. 560 00:54:02,340 --> 00:54:10,530 So you measure all, all aspects of the image. So you can almost make almost perfect images with high, much higher resolution. 561 00:54:10,530 --> 00:54:17,310 So this is a model at two two three gigahertz. What we observe now of the centre of the Milky Way, it's actually blurred due to the scattering effect. 562 00:54:17,310 --> 00:54:23,040 And if you do this, then again, this is simulated image something that's what you could get. 563 00:54:23,040 --> 00:54:30,180 Yeah. This is powered like shapes, right? So, uh, now if you go to space, you can go to higher frequencies. 564 00:54:30,180 --> 00:54:36,060 The 690 gigahertz emission is much more concentrated. And you know what you could get from space is something like this. 565 00:54:36,060 --> 00:54:40,380 You see the wisps, the details of everything, and we know other papers we can show. 566 00:54:40,380 --> 00:54:46,920 We can measure the spin very detail. We can actually distinguish this, uh, from a non-standard theories of gravity. 567 00:54:46,920 --> 00:54:53,070 We can see many more black holes. So I think we're not done by a long shot. 568 00:54:53,070 --> 00:55:00,330 Uh, so much more to be to be done. So let me conclude, think we've changed our picture of black holes, at least a colour? 569 00:55:00,330 --> 00:55:07,380 We've changed and then I'll read. We can look look the beast into the not the eye into the throat, actually. 570 00:55:07,380 --> 00:55:14,820 And supermassive black holes are no fantasy anymore. So we, we we, you know, this is they do everything a black hole should be doing right. 571 00:55:14,820 --> 00:55:20,190 And so we can actually see it was our well with our own eyes through a telescope and some computers and so forth. 572 00:55:20,190 --> 00:55:24,060 So it's a bit some processing in between. And I think that's it's quite amazing. 573 00:55:24,060 --> 00:55:26,400 We're now in a special way anyway. 574 00:55:26,400 --> 00:55:33,000 Living in the special generation, right, we are seeing images of the of the universe that no generation ever had been able to see before. 575 00:55:33,000 --> 00:55:37,530 We see the stars, we see the planets we see in a marvellous deep universe. 576 00:55:37,530 --> 00:55:42,480 No, no, no, no generation before I had the privilege to do this. 577 00:55:42,480 --> 00:55:47,560 And we now, you know, doing the next step could conducting physics at the end of space and time. 578 00:55:47,560 --> 00:55:50,940 We have rotational ways, we have the event horizon telescopes. 579 00:55:50,940 --> 00:55:56,970 We're going to have the square kilometre array, which will measure have pulsars studying gravity in great detail. 580 00:55:56,970 --> 00:56:04,270 And so we're really zooming in onto trying to understand gravity better because one thing I didn't have time to talk about really gravity is 581 00:56:04,270 --> 00:56:14,970 its last still not understood for us in our entire universe because we have wonderful quantum quantum theories of of matter and everywhere. 582 00:56:14,970 --> 00:56:18,300 The only thing that resists our quantisation of. 583 00:56:18,300 --> 00:56:24,360 Understanding of quantum theories is gravity doesn't fit our picture, especially at the edge of black holes. 584 00:56:24,360 --> 00:56:32,550 Quantum theory and general relativity don't go together. So in our cell phones, we use quantum theory that makes our cell phones run. 585 00:56:32,550 --> 00:56:36,210 We use general relativity that makes us navigate in the cell phones. 586 00:56:36,210 --> 00:56:39,780 But the edge of black holes, one of these two theories has to be wrong. 587 00:56:39,780 --> 00:56:45,360 We just don't know which one. So that's, I think, an exciting times, 588 00:56:45,360 --> 00:56:52,230 and we're finally starting experimental inroads to to to study things and know it takes the world to make such images. 589 00:56:52,230 --> 00:56:57,180 You know, you can't do this in your lab. It takes the entire world to do this. OK? 590 00:56:57,180 --> 00:57:05,400 A long future, of course, is, you know, with your oxygen, the black hole here. 591 00:57:05,400 --> 00:57:11,520 You know what won the round will take a little while. If the galaxy, there's a non-zero chance we'll end up here. 592 00:57:11,520 --> 00:57:17,670 OK, good. So there are two kind of 12 things to lecture here and then, yeah, OK. 593 00:57:17,670 --> 00:57:31,623 So then we'll know for sure what's going on. OK, so that's a thank you for your attention.