So I think it's sort of. So welcome to the Nineteen Kinsey Lecture. I'm delighted that this on this occasion, we have Professor Heino Falkor, who is a professor of radio astronomy and astro particle physics at the University in Nijmegen in the Netherlands. Heino read Physics in Bonn and in Cologne, and got his PhD in 1994 for.
Since then, he held positions at the Max Planck Institute for Radio Astronomy Bonn and also University of Maryland and the University of Arizona, 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. His research contributions are very wide. They span radio transients, cosmic rays, active galaxies, the Galactic Galactic Centre and, of course, black holes.
He was one of the major driving forces behind the Low for International Radio Telescope, which we have a big involvement here, even exploring the idea of putting such an array low-frequency array on the Moon. He's played significant roles in the square kilometre array and the portrays telescope in Argentina, but most relevantly, for today, he's the chairman of the Science Council for the Event Horizon Telescope. He's an enormously distinguished scientist.
Amongst his accolades that he's a member of the Royal Netherlands Academy for Art and Science, this is the one I like best. He's a night of the Dutch order of the Lion. And in 2011, he won the most prestigious prise the scientists from winning the Netherlands, which is the spin. There's a prise. 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,
has been seen by over four billion people. Surely no other hints electorate can claim this. 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. Thank you very much. Can I be understood? OK, good. Yeah, I was here actually already in February and giving a lecture on the same topic, but it wasn't allowed to say anything. So it was very. And so as a punishment, I had to come back.
But I must say I've been treated so well. I think I want to be punished more often and like the. 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. But of course, work you don't do on your own, you do it together with with your students, with international collaborations, with your colleagues, particularly here in Europe.
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. It was given to the three parties here and allowed us to actually do a lot of this work and made a significant contribution to this international collaboration. And I say this is an international collaboration of about, well, the papers have 350 people. So in the collaboration there are two hundred fifty.
And this year, both from our collaboration meeting in Nijmegen in, uh, in November, um, actually exactly a year ago in Nijmegen. And that was the first time we were discussing all the signs, and everybody's smiling because they had already seen the results, right? So we were not allowed to talk about it. But at this time, people were still smiling.
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 February March to actually get the papers written up and everything into a publishable form. So it was a very intense period for all of us, but it's certainly memorable, memorable period for for us. Now it all started. It all started with the centre of the Milky Way, at least for me. And this is this beautiful image made with the Meerkat telescope.
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, and then a part of the physicists came to me and say, Oh, this this nice artist's rendition of the Central America. This is real life. OK, this was real. It's not. It's not. We don't make this up that what happened? 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.
But anyway, so of course, when we started, we didn't have such beautiful images. But if you zoom in, this is the plane of the Milky Way and radio and you here with radio, it can see through the entire Milky Way, it goes through dust. And so the the plane of the Milky Way glows even brighter than on the sky with stars and the centre is somewhere here. 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,
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. The radar technology was used for for astronomy. People would find out what the structure of the Milky Way is. It was a major contribution of radio astronomy in the early days after after the Second World War. Now, if you zoom further in in this very centre, you actually see more structure as this.
Here is what's called Sagittarius A West. And then in the very centre, you see this this radio source Sagittarius called Sagittarius A because this is in the constellation Sagittarius A because it was the brightest radio source. And then this was discovered in the 70s, in fact. 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.
Because in analogy with other galaxies, quasars which were found where people were thinking this could be powered by supermassive black holes and they all had these small, very small radio sources in the very centre. And the idea was, well, if in these quasars, far away, they are these supermassive black holes with radio emission, maybe you should have one in the centre of our Milky Way.
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. And then it was called Sagittarius a Star Y star because star marks an excited state and an atom. And people were before that saying, calling the compact radius source in the galactic centre, and they were tired of it. 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.
It's not a not a fancy name, but you know, we have to live with it. And and what we see here is actually what I said an optical view of the Milky Way. Right. With, of course, a camera. You never have such a beautiful view with your naked eyes. Well, if you go to the southern hemisphere, you get close sometimes, but not quite as detailed and you see all these dust. Howard's here and which actually formed stars, but they block our view of the the centre of the Milky Way.
Well, you can zoom in using Infra-Red technology also. Actually, wartime technology was developed in the 80s 90s to actually see at night, but you can also see through the dust. And then what you find is that the central region here is actually full of stars. 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.
You have you millions of stars. So if you would live in the Central Milky Way, the sky would just be full of stars. There would be a completely different side. There were full of stars. But where is the black hole? It's hard to pick out. Well, you know, from the radio, you would have to guess where to look and you zoom further in and then you would see something remarkable because what you see here is a very high resolution image, actually a movie made over 16 years by this case.
Our colleagues in Garching, Munich, what you see in the stars are moving over 16 years and you see that star here actually making a circle actually ellipse. In fact, that movie repeats. So it's three times the same movie. If you measure this, you see, it actually makes a perfect ellipse around a point around a central focus point.
This is slightly projected ellipse, 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. OK, if something goes wrong with 10000, cannot come out of second round something, you need a lot of force to keep it tight, OK, to keep it on this orbit. Now we know where elliptical orbits come from.
This is what Kepler told us and all this describes, for example, the orbit of of planets around the Sun. They all elliptical orbit, and that goes back to the laws of Newton to that that we can describe then explain these things. And by applying exactly the same maths and using the same laws, we describe our solar system, which we can use, where we can use the planets to weigh the mass of the Sun. We can actually weigh the source in the very centre how much mass you need to keep.
A star was 10000 km per second on this orbit. Well, it's four million times the mass of the Sun. In fact, the measurements are now so precise this using ESO's European Southern Observatory Interferometer. Latest data here you actually would see that star move every day, every hour, actually every night. I should say every night it would move in and you'd have a maths measurement now. Four point one five plus minus 0.02 million solar masses concentrated all in that radius source.
So that, of course, was a very strong indication. OK. The black hole has to be there, but OK, but what is a black hole? Of course. How do you make a black hole in the first place? 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. The star will collapse, and if the mass is, the star is very massive, much more massive than our own sun.
The amount of mass will become more and more concentrated and will actually overwhelm all other forces that we know. So there is no force, no pressure. Nobody is strong enough to keep that collapsing star, that imploding star from further collapsing it. 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.
It will collapse forever. And that's what you see here is actually the remnant of a supernova explosion. Know we see these these things around our Milky Way. We see them in other galaxy. Stars tend to explode every day, somewhere in the universe, somewhere in the universe. Every day star explodes, maybe destroys an entire planetary system. We find it lovely. But, you know, maybe, maybe a terrible thing for people there. For us, it's just astrophysics at this moment, right?
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. But if you go to the centre of the Milky Way, where you have millions of stars, 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. And that black hole will keep it. Creating more mature matter will fall and it will keep growing and growing.
So in the centre of galaxies, you expect this big black hole's very massive one millions and we'll see later. See also billions of solar mass. But you know what? What makes the black hole so special? You know what's what is it doing and where does it come from? And why is it so important in the theory of general relativity and our understanding of science?
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. And as you all know, gravity was invented in England. And so gravity with the idea was by Newton. Actually, that gravity is a force, OK? And it was. The story is that this was, you know, him seeing an apple falling down and wondering, why does the Apple fall?
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. 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. 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.
OK. And that's you can use and describe the motion of planets around the Sun perfectly. Well, OK, that's a wonderful. But then, of course, in the 19th century, there was a bit of a problem. You know, astronomers were measuring again planets, and then the mercury was going around the Sun, but it wasn't doing exactly in the way was predicted by Newton. In fact, it was. It was. It was, you know, the orbit was processing a little bit.
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. So that's how wrong and quote unquote, this was. So some astronomers were obsessed with this little hair found in a cake. 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.
And the theory came with Albert Einstein just describing that as saying that gravity is not a force. It's a property of space and time. It's a property of space. That space itself is not a flat, a flat, flat space, but space itself can be curved. Well, we have a hard time understanding that, you know, how can how can space be curved? So we always picture this in two dimensions.
OK, so you picture a two dimensional surface, which which is represent three dimensional space and you have a mass in it. What we'll do if you put a mass onto a blanket, for example, and will create a little dip in it. Now, if you have a lot of mass, then you create a very deep hole, so to speak. 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. We'll just follow the shortest way towards, well towards the bottom.
Now, if you have a ball rolling on this, you know this this curved space time, you see how people deflect it again. Fall off, follow the the shortest path, so to speak. 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. If it doesn't go fast enough, it will just roll inside, OK, and it has to have a certain speed to do this.
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. It's still fun. OK, good. It's funny. I was avoiding this word for the last two sentences. OK, so it's going down in the funnel and this funnel and your speed has to go faster. OK, it goes faster because it's the the the the curvature is much, much deeper. So it has to go faster to survive, right?
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. And so you know what happens? And it's described as a simple wall that the velocity with which you have to go around in the classical picture is a square word of the gravitation constant times the mass. Divided by the radios with which you rotate, which means that if you go to a smaller and smaller orbit around the star or black hole is this velocity will go up.
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. 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, which you call the event horizon. So it goes here with a speed of light and, well, it's a cloud. Not because it's torn apart because it just forbidden.
OK, sure. Claims that you're not allowed to go faster than the speed of light if you have any mass whatsoever. In fact, this is not something that that on the ancients, that it's just something we measure. That's sort of a speed of light is sort of a constant, which is which is a very fundamental property of our universe. 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.
And what's what's happening there? Well, that's picture now light itself. So I said before was that light is really the only constant we have, so to speak. You know, the speed of light is the only constant. That's what we measure. Really, light always goes with the same speed. Know how fast you move where you are. You always measure speed of light being the same number. OK, now what happens here? Light goes through the curved space time, and it has to follow the shortest path again,
and which means the shortest path is going on a curved trajectory. OK. And of course, it has to travel more space, so to speak with the same speed. So something else needs to change while speed is kilometres per hour or something, he is like miles for something else. And and so if you have more space, same speed time has to change. OK. And that's what you see here. You know, you have like a clock. Bang, bang, bang, bang. And here suddenly time will go slower. OK.
Suddenly. Also, time needs to change, and that's a very crazy conclusion. 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. It's really quite a significant claim. Well, it turns out all of you were making use of this every day, not every day.
But at least, you know, if you if you use a navigation system to come here, if you use a navigation system, you actually compare the arrival time of radio signals from satellites that that are far further away from Earth, so their time goes a little bit faster. In fact, thirty eight microseconds a day. That's how how fast flux, how much clocks go faster than here on Earth, simply because of that effect.
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. So all of you, if you ever use a GPS system, make use of the theory. If Einstein, this crazy result that the astronomers made 100 years ago was with Mercury. So it's, you know, it's become commonplace. You know, you make use of the fact that time runs differently.
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. What happens if you are near a black hole? Well, like then if you have a diamond strike, so to speak, 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. It will go so slow seen from the distance. That time seems to stop here at this point that we call the event horizon.
And the second effect is that if you if you are here as a light, you want to get out again. OK? But what do you have to do? You have to go with the speed of light. Well, that's OK. But you have to go if you are beyond this point, faster than the speed of light. And that's not allowed. OK, now we are on the highways, know we like to go a little bit faster sometimes. Some of you do it. Not everybody, but some of you do OK. We think that's OK.
But your flight, that's absolutely not OK. They will not do this. This means that, you know, everything that goes beyond this point will never be able to come back. Matter will not be able to come back. Light will not be able to come back and everything else. Any information, any form of communication will not be able to come back either, because everything we do is radio waves is just light. Yeah, if you use your text message, sorry, I'm in a black hole.
You know, I do it, we'll use radio waves. They will not get out because it's radio light. OK, so that's what we call this event horizon, because every event, everything that happens beyond this point is not observable fundamentally based on the theory of of of all the attention. One last point is OK. You can just measure how you can calculate from the formula how big this is. This is about, you know, one half kilometres, I guess it's about one mile for a black hole of one solar mass.
OK, typical black holes are sort of 10 solar masses. I'm sorry, about 10 miles radius for a black hole. That's a small, small thing, but they are black holes. 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. And they would be the size of 150 million kilometres. That is the distance from the Earth to the Sun.
OK. Or even the size of the entire solar system could be a black hole just for fun, just for students who can also calculate what is the average density you need to make a black hole. You know, essentially, how much matter do I need? What's the density of matter? I need to fill the the Earth's orbit with it? Just take the maths divided by by its radius. You get you get three mass divided by the volume.
The volume is set by this number. I give you certain density well for still a massive black hole. It's sort of it's huge, right? So it's a 10 to 13 kilograms per cubic centimetre. OK, so this this little thing, you have 10 to 13 kilograms. But if you go to a Solar System sized black hole, well, you only need to fill it with water. So it's one gram per cubic centimetre more or less, so you can fill it with water.
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? You don't turn off your faucet. You, you feel the solar system with water. 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. That's the important point. Of course, you know, the water will collapse. It will collapse into a point, become much more dense. But what will happen to you if you go to a black hole?
OK, so if it's a stellar mass black hole, you know you are happy you face here. You go to a black hole, you're still a happy face because exciting, of course. And then you go to this this phase. Well, what now happened? 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. OK. So are you really being stretched a little bit? You go very close to the black hole.
You're really being spaghetti fight. OK, your turn into a long spaghetti. OK, so not a pleasant experience, or even not not smile anymore at this point. 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? Because why? Because you are tiny. No, you tiny. You know you just one person compared to the size of the Solar System.
You go in there. You know, even this little dot here will not experience much bigger edification. You can go into safely into a black hole and enjoy the rest of your life. Of course, you will never be able to tell anybody what you're going to see. So but that is possible. 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. So this if you picture yourself relative to this, this massive black hole.
OK, so now we understood what a black hole is. And the next question is, how do we see it? Well, of course, if you wanna see something, you need light, so you shine light on a black hole. And that's what you see here. You shine light, shine light at the black hole and light will be deflected and we're going rather peculiar in orbit, right? So light will go here. Actually, here even goes back around the black hole.
Why is this? Well, because in this case, the black hole is even rotating and it rotates. It will actually take space with it. OK, so even space doesn't isn't fixed any more. 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. Even light has to do this. It will disappear in this black hole. You also see the colour will change. It's blue and then it turns red. So why is this?
Well, this is light coming from the edge of the black hole not yet disappeared, so it has to run up the hill right in this curved space that has to run up the hill. And so if you do this, you turn red, as you all know, and at the same, almost the same principle. Here it turns red because it loses energy and cost energy to climb up into this way from this black hole and so light that loses energy becomes redder and redder with this time.
Now this actually go back all back to in fact, papers from 1916. In fact, a lecture from David Hilbert in 1916 who actually described for the first time how light is being bent. I find this quite amazing. 1915 Albert Einstein derived the theory of general relativity. Just a few months later, uh, Schwarzschild derived the metric. How did the curvature of spacetime would look like for something that is as a black hole?
And Hilbert described how light would be bent within a few months or within a year. Everything was settled. It just took another hundred years to understand what it actually meant and to measure it. And he, you know, he described particular this effect you come with light and then actually there is a particular distance from the black hole where light is bent and will actually go into a circle actually will go into a close circle.
That's quite an amazing thing. So if you were supposed to be standing here, 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. You see yourself standing in front of you, as you were like three weeks ago, right? Because it takes now for the big one black hole to take three weeks to go around the black hole and and see you. So that's what you would see.
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. Well, explain in trying to explain the centre of the Milky Way in the in the in the early the late 90s, we realised that radio emission would come from very close to the black hole.
So there is light, you know, in darkness, in the darkness, so that black holes can be very bright because that folds in, it radiates stuff actually even managed to escape before it enters. And that will shine a light at this black hole. And it turns out what you will see is a hole. OK. Not a surprise. But actually, that hole is actually significantly larger than the event horizon.
Because a black hole is a big lens, it will actually magnify itself. It makes itself appear bigger than it actually is. And turns out that that size here is proportional to the mass, 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. And that that shadow side to be called it the shadow of black hole is is almost is there all the time?
Whenever you do, you have a different light in different coming from different models. You always have this, uh, the shadow, and you tend to alter how these rings, right? So it's one of the predictions we made. 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. If you look at a black hole light coming from a black hole, you should be able to see it.
You also said you need to take a technology which was known very long baseline to fragmentary. I'll explain in a moment what that is at a certain frequency. To actually do this, then you would be able to see the event horizon would be able to see that shadow. So that was 19 years ago, and at the time I was actually telling, in fact, the BBC. 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.
But he kept calling me. I told you we are going and getting closer. And he actually called me every year and told the BBC that one of the first ones to report on that result, when it finally came out, it was still the same reporter that cover that one. So it's quite amazing. So anyway, so we do better modelling these days. 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.
These rings are magnetic fields. We like the material matter rotate. The magnetic fields will be stretched and as another form of gratification that will happen, these magnetic fields, which are in this matter, will be turned into a spaghetti bowl. OK, you you'll it further rotate and then magnetic field will pile up and actually will shoot up along the rotation axis. So we see how matter creates how it rotates, and we see the magnetic field inside, we see it shooting out.
And that's in fact a phantom phenomenon that we see throughout the entire universe. It's called the cold jets. Now, the next step you have to do is you have to see how has a gradient. And so what we're doing here is actually this is more this is actually a very accurate simulation, with light bending included to calculate how light is where it's created, where it's absorbed, how it's bend around. And you see sort of you saw that that jet shooting out, you see, it's actually glowing.
Now I have to tell you one thing and I have to, you know, one thing actually, black holes are not red. OK, I show you that. You know, you see at night, it looks like a volcano is very dangerous. 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. OK, so we have to translate it into our eyes. We have to give it a colour. And so it's on this prediction. In 2019, we made it red.
And because before that, the the radar astronomers would use rainbow colours for four for representing radio images. And I thought black holes are not sounds like a happy place, but black hole is not a happy place right now. So you have to use another colour scheme. So we use threat. And so that's that's the only secret, right? 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.
And so you see this simulation, which actually you can do in this virtual reality general relativistic retracing three dimensional general versus magnetic magnetic magnet Magneto hydrodynamics simulation. 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.
And so there is this one source which is now very popular, very well known, called M87 M87, because it's messier catalogue of messier, uh, number eighty seven. So messier in the centre of Paris was, you know, in the centre of Paris, and a 19th century could still do this. It was an optical telescope with charge of the sky and would see this nebula at the time.
We wouldn't even know we would not even know these were galaxies. We're just nebula. OK. 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, short shields and, uh, an Einstein also formulated the basics of black holes and astronomer found a little streak of light there. OK. Didn't know what what it was. Didn't know it was a galaxy.
It, you know, it didn't even know that this streak of light would point right at the black hole. That these other theories that just found. Again, it took another fifty years to connect these things and put them together. That still makes me think that, you know, as astronomer, we sometimes see crazy things. And maybe that's exactly the place where, you know, a theoretical physicist has to look to understand, you know, something fundamental about nature.
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. People were measuring the mass when I did my Ph.D. the maths was two billion solar masses, two billion, you know, two times 10 of the nine that's huge was still too small. OK, well, still too small to be seen with the technology that we have. Then it became three billions, but still too small.
OK, but then it was another measurement. You said six billion and then it was potentially possible. 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? We simulate these jets. Now, this year is looking at the same simulations, but now at one radio frequency, at eighty six gigahertz, three millimetre wavelength, you see this naive plasma going out. It actually look like an hourglass.
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, you know, resembles what we were modelling. And if you would then zoom in and go to the high frequency of 230 gigahertz, all the extender stuff fall away. It's like X-ray. You know, if you're going to choosing the right frequency means you x-raying to the right location.
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. OK. And 2p bend and produce this ring. 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. OK, it doesn't often happen unless you actually do a proper prediction in astronomy. OK, especially if it comes to an image, but this is basic predictions of air.
And so that's what you expect. And some astrophysics that needs to go in there to actually find the right frequency. And so, you know, that was a prediction in 2016. You can calculate how big this is. Well, the size of this is 40 microseconds. OK, what's 40 microseconds? It's about the size of a mustard seed in Philadelphia, as seen from here. OK, so and then you can calculate how big a telescope do I need?
You know, I know the frequency. And so the the resolution of a telescope is given by the wavelength divided by the size. The wavelength is given. It's one millimetre. How big does the size have to be? What has to be the size of the Earth? OK, so you need a telescope the size of the Earth to see that thing.
So we build one. And that was called the Event Horizon telescope that she started already in the 90s, the technology of eye very long baseline interferometry, as I said, was already available, but not at these high frequencies.
The first successful experiments were made here between Spain and France, and then in the US you had three telescopes coming together and then by combining telescope, he actually synthesised in the computer the virtual telescope with the size that is corresponding to the diameter or the separation of these telescopes.
And in 2017, we made our first experiment. After many years of negotiations with which other we actually we were here able to do the first experiment with eight telescopes at six different mountains around the world. Why mountains? We have to go to dry, high site have little water vapour in the atmosphere as possible because these high frequencies millimetre waves absorbed by water vapour.
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. And what you also need is good weather. Right, so you need to have good weather around the world. And so we are budgeting entire week because we're hoping at least one day will hopefully be OK. OK? And in the previous run, it was never, actually ever, always OK.
You know, either telescope had failed or the weather was bad or, you know, nothing had ever worked. And now we had field. It's the biggest experiment, and we were hoping for some. Well, we started the first day. It was perfect weather. OK, second day, perfect weather. The third day. We're all tired. You know, actually, it's for a fourth day. We're tired. So we declare that bad weather and and then continued. And then essentially within within a week, we had all the data we wanted.
We, we, we we recorded four petabytes of raw data and all these telescopes. The data was then shipped to the set to correlate to places where things were combined into a supercomputer to, you know, to to be further processed later. Took a little while to ship the data. I mean, you have to pack it really in hard drives, hard drives, you put it put in boxes, 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.
You have to wait until the next morning so you can ship and take six months until the sun rises again. 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. I just point out some of my students here, but you're young than you did. The calibration work later.
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, she did the again led one of the calibration papers and faked that to simulate the observations, she's quoted the ALMA data processing. And I was having fun here at the expense I the which. And then the South Pole, of course, as that you have to have some dedicated staff will stay there for for a longer time.
This is yeah, this was actually observations here, this was before and this was after it was really tiring, I should say high elevation and then observing all night. 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, which you record with 32 gigabits per second always being asked, Why don't you send it over the internet?
Well, I'll try to send 32 gigabits per second from the South Pole to a central location that's not going to work. So there's no internet. That's a few kilobytes per second, actually. Most of the time. You have atomic clocks at each telescope and some, some electronic equipment. Now for the experts, what we measure is actually a correlation coefficient which are OK just for the rate astronomers.
This is what we really measure the visibility amplitude as a function of baseline. How strong are two telescopes correlated? 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. Why do I show this? Well, that's essentially essentially more or less the raw data and the dashed line is the model of a ring ring in the same representation would look like this.
And so when when the first calibrated data came out, we didn't have an image whatsoever. We just looked at the raw data. We saw this going down, going up and going down again. We thought, Well, it's going to be interesting, OK? We didn't have an image. 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.
Now, how does the imaging work? The parameter? So you have two telescopes, and the work essentially is a set interferometer. Radio waves come in play in parallel waves. You bring them to interference, you measure interference pattern. And depending on where the source comes from, that interference pattern, changes and and so forth.
And so if you have two telescopes, you see these waves and you have more telescope, you actually add up ways and the image will build up from the different perspective. So in this case, actually the image that we reconstruct with such a virtual telescope looks like a teapot. OK. OK, so it turns out Russell's teapot can be seen, after all. Well, you know this. And actually, this is not yet fully processed.
What actually can can be made better. OK, so you buy it by combining all these different perspectives from different telescopes, you can recreate this virtual telescope and get some, some basic image. 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.
But now I assure you the results first, you know, we actually did many years work on this, 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. And I think that just relive this for for a short moment was actually the biggest zoom in astronomy, and we're having a Zoom factor of one billion, OK? We're starting at the old sky looking towards Virgo.
And then, yes, the sun by the music was made by my son, by the way, he was making film music. And OK, so we're zooming into the direction of Vega. 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. 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. And then you zoom into this jet as you get closer and closer to real data, you get closer.
And then you see this this structure, and that's what we got out in the end, you see, you know, you look at the source with many different ways for different telescopes. You always see this jet chitchat and only when you go to this high frequency, you suddenly see that ring. It's on a fundamentally different from everything we've seen before, but it's exactly what we have predicted at this frequency and that was the magic of it.
So we saw that the first time, you know, you see this data, you see the first image and gosh, you see the ring look like you always imagined in your dreams. And that's the beauty of physics. Sometimes it works, and most of the time, you know, in our eyes, it doesn't. And you have to figure out why. 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.
You know, it was really the front page news all over the world, as you said. Of course, social media went went crazy. Certainly, like cats, cats are popular on social media, cats and black holes receive a really, really big prise. Everybody was raving about this. I was, I was, you know, why am I saying? I learnt I was sort of trending online geek when I looked up? What nine degrees? I wondered whether I want to be there, but it's all the bad jokes come from there from this website.
So you don't know what all the everybody below 18 knows it. So. And so briefly, how we made that image in the first place. The first step was that we actually blindly gave the data. It was calibrated on calibrate sources. We first calibrated not on this source, but we calibrated on quasars. Then we calibrated on the source by small group. We gave it to four independent teams and international national teams.
This was a team where we were involved as a thorough again frank, an Asian and American colleagues and independently of each other. They should, you know, use preliminary calibrated data and make images in all of them found again a ring. It wasn't quite as nice as the final product, but independently of each other, we found more or less the same same structure. OK. And then we started all over again. Then we send it.
We submitted, we compared an all all use different methods and we start all over again with actually simulated data. In fact, before that, we had imaging challenges. So people were giving images, which was with simulated data, and they had to reconstruct them. Sometimes there was a snowman, sometimes there was a ring, sometimes they was an OK and they had to show that their methods work.
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. With a ring, there was a ring, a crescent shape, a disk or double source or here simulation. And then, you know, you had this different algorithms that should recover the basic structure. So this should always show some kind of a disk structure and not not a ring. So we did not use algorithms, which would always give you a ring that was important,
you know, if it was a double structure and should give you a double structure. OK. And so then we we picked the ones, the algorithms and parameters that would reconstruct all these models equally well. OK, so we could have, you know, algorithms which work on this, which can perfectly reconstruct image rings, right? We could make nicer ring images, but we didn't want to do that. And so that's what we did.
And then you had, you know, the final results from three different independent algorithms and they all got the ring. It all was brighter in on the bottom. OK. But you see, there are subtle differences between this, this algorithm and this algorithm. 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.
OK, so I saw on the internet, were people actually going to the final result and taking out like the subtleties and image processing? It just doesn't make any sense. And all the data has a certain limit to which it's accurate and reliable. It's certainly reliable to the fact that it's brighter on the bottom, and we can easily explain this by relativistic beaming.
So if the gas goes around with the speed of light and when it goes towards you, it's actually the light gets an extra boost because you go with the speed of light. So it actually shines like a like a flashlight in your in your face when it goes away. Actually, you only see a fainter emission because it shines away from you. And so if it goes around with a speed of close to the speed of light, the stuff that goes towards you is brighter.
The other half of the ring shines away from you is fainter. So that's exactly what we see here. But the details, you know, we don't know and we don't trust. By the way, this method here is 30 years old. The other ones are also pretty, pretty standard. And then we combine them and we looked at we had four different days and four different days, we've got the same results.
OK. And so that really is what what convinced us and different different people, different algorithm, different days, always giving you more or less the same result. 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. You don't see all the details. Maybe you see here is see see stuff going around. You see this almost spiral wave going around, but you see also this ring, which is stable.
And that's exactly the light that goes around a few times around the black hole that always gives you that ring. OK, and that's the stable feature. Sometimes it's much brighter sometimes and not quite as bright. And you see that actually changes the function of time. So the black hole will look different every day. Yeah, every every day. Well, a day in the life of a of a supermassive black hole actually is a few weeks here.
So I for one a week, it should be stable, but over a month it should look slightly different. OK. And then we actually calculated many, many different black hole models changing the astrophysics, changing the maths of the ah sixty thousand images of black holes that we calculated with the accretion with a light bending and everything that's the biggest library of black hole images ever made.
And all of them show this shadow and show the ring so that the basic prediction you know that we made 10 or 20 years ago is also borne out and supported by by these massive simulations now. Now we also took some of the best fitting ones, these are simulations, and then we run them through a simulated view of observation. So these are all everything is simulated here. The computer simulation of a black hole, then a computer simulation of a VLBI telescope.
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. For the for the astrophysicists, this is a counter-rotating, this is non-irritating, this is a maximally rotating black hole. They all give the same result. That's exactly the point I was making. 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.
You can also measure than the ring size, the width and from the width, as I said, 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. And that was sort of another confirmation that we're doing the right thing. And we also looking at how round is that image just unfolded and you see it actually pretty. It's a pretty straight line if you sort of unroll that image.
It's circular to within 10 percent. That's another prediction. Actually, it should be circular to within 10 percent. That tells us that there are not additional parameters, for example, governing the black hole. Uh, yes. And if one other conclusion that we can draw from this. So from that, we we we actually, you know what we concluded, know all the tests we can do is this is real. This is determined by general relativity.
We're looking if we look into this darkness, we're looking really into the darkness of the event horizon, OK? And what we're measuring is this photon related to the fortune of its effect. You also know that black holes were measured with gravitational waves maybe two years ago. You've seen the news here that was done at a different scale 60 solar masses. We measuring it six billion solar masses. But if you can derive the gravitational waves I actually made, that's easy.
The the wobbling of space and time are made in exactly the same scale. They also made at this photon ring where the light, you know, with light goes around. That's also where gravitational waves are made more or less. And so you get a scale of 460 solar mass black holes. You get it for six billion solar masses. And we know that the scale of of this, uh, of black holes goes linear, linear with mass exactly as ancient predicted. So over a factor of 100 million, we just change the mass.
We can explain the basic properties of these things. So it's as if you you have, like again, a human cell, the smallest human cell and Buckingham Palace. And the only thing that changes between them is just changing the mass how heavy they are. 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. What's next? There are some dreams about increasing the Event Horizon telescope, more telescopes.
This is sort of here more telescopes in the Americas that doesn't add too much sort of adds a bit more robustness. 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. There's not a single telescope of that kind in all of Africa. And so that would help us to make more robust images, particularly for the centre of the Milky Way.
We have a telescope actually available, it's actually in Chile right now, it's 50 metre in diameter. It's not being used anymore, so we can actually get it. We actually get it for free and that's all. We actually don't even have to pay for it. So we get it for free or or whatever you want. So they're happy that we take it. We can take that one. We actually replace everything in it.
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. 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. This is the second highest mountain in Namibia, two thousand three hundred metre high. It's just a fantastic table mountain. It's a three kilometre long 800 metres wide.
If you're there, it's a very stay. That's the one of the problems here. We still have to upgrade the road. 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. It's like you can see, right? You, as you see everywhere, is Horizon and the night sky. You know, I can tell you, it's just marvellous. I mean, this is the best place in the world to see.
The night sky is no light pollution, everything. It's just you see the Milky Way. So clearly, it's just it's wonderful. We also couple this with an outreach programme. This is actually what you see. Here is a mobile planetarium that we actually use in the Netherlands. We go to schools in all the Dutch schools, actually get this mobile planetarium and get your show of the universe. And we're teaming up with a local NGO, which goes to local schools in Namibia.
And we've done that and we've, you know, within a week, we, you know, we brought into 1300 1400 school kids. And so we are now starting next Monday, a crowdsourcing campaign to actually fund a planetarium for Namibia, 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. Uh, because we want to do this together with people in Africa and not just, you know, on our own.
This has to be integrated think and astronomy is a great tool because we all share the same sky. Right. So everybody has the same experience when you look up into the sky. And of course, in the long run, we want to go to space. 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. They orbit around the Earth, slightly different, uh, orbits. They will drift apart and then you measure all separations and all orientations.
So you measure all, all aspects of the image. So you can almost make almost perfect images with high, much higher resolution. 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. And if you do this, then again, this is simulated image something that's what you could get. Yeah. This is powered like shapes, right? So, uh, now if you go to space, you can go to higher frequencies.
The 690 gigahertz emission is much more concentrated. And you know what you could get from space is something like this. You see the wisps, the details of everything, and we know other papers we can show. We can measure the spin very detail. We can actually distinguish this, uh, from a non-standard theories of gravity. We can see many more black holes. So I think we're not done by a long shot.
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? We've changed and then I'll read. We can look look the beast into the not the eye into the throat, actually. 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. And so we can actually see it was our well with our own eyes through a telescope and some computers and so forth.
So it's a bit some processing in between. And I think that's it's quite amazing. We're now in a special way anyway. 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. We see the stars, we see the planets we see in a marvellous deep universe. No, no, no, no generation before I had the privilege to do this. And we now, you know, doing the next step could conducting physics at the end of space and time.
We have rotational ways, we have the event horizon telescopes. We're going to have the square kilometre array, which will measure have pulsars studying gravity in great detail. 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 its last still not understood for us in our entire universe because we have wonderful quantum quantum theories of of matter and everywhere.
The only thing that resists our quantisation of. Understanding of quantum theories is gravity doesn't fit our picture, especially at the edge of black holes. Quantum theory and general relativity don't go together. So in our cell phones, we use quantum theory that makes our cell phones run. We use general relativity that makes us navigate in the cell phones. But the edge of black holes, one of these two theories has to be wrong.
We just don't know which one. So that's, I think, an exciting times, and we're finally starting experimental inroads to to to study things and know it takes the world to make such images. You know, you can't do this in your lab. It takes the entire world to do this. OK? A long future, of course, is, you know, with your oxygen, the black hole here. 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.
OK, good. So there are two kind of 12 things to lecture here and then, yeah, OK. So then we'll know for sure what's going on. OK, so that's a thank you for your attention.