 OK, good evening. I'd like to welcome you again on behalf of the Faculty of Science and the Albert Einstein Center for Fundamental Physics at Bern University. And I would say this is by far the best attended Einstein lectures that we ever had. It was a tense round. And there's no surprise why this is the case, because Barry gave two wonderful lectures the last two days. And so we are looking forward to your last lecture, Barry. Thank you very much. So I've spent the last two hours with you, giving you the history and the perspective of how we developed to where we were able to detect gravitational waves or when it came to that, and then some insight into what it took experimentally in the last lecture and a little bit about how we can extract the information from the data that we take in the last one. Everything in the last two lectures was pretty much on firm grounds. Today I'll be a little more speculative, and you shouldn't take quite as literally everything I'll say. It's really our plans and maybe aspirations and projections and projections aren't always right or come out the way you think they will of how this is going to evolve in the future. So I'm going to review a little bit for everybody where we ended up to where we ended the last lecture. And then I'm going to talk about the future in as kind of free away as possible and just don't take it. I think the future is as bright as all for this field as bright as I'll paint it, but probably as happens in science won't develop in exactly the way that I projected. So I use an example here which I'll talk about just a little bit more today of the last thing that we detected, not what I won the Nobel Prize for. We did that for the black holes. And this to me is an illustration that we're beginning a new field of science. This picture here is an artist's view, not a scientific picture of all the radiation coming out in different forms from a collision not of two black holes but of two neutron stars. And neutron stars are nuclear matter instead of black holes by being nuclear matter when they interact and come together many, many things happen, much of which we haven't detected yet. And I'll even talk about that a little bit. But anyway, so I use that purposely as my illustration the last one because I talked technically was a picture of some vacuum systems. And the first one I think was Einstein. So that's kind of my plan and so forth. If I talk about the gravitational waves that we were aiming for and are aiming for in the experiments that you heard about so far, which means earth-based experiments, experiments here on earth. There's a whole variety of possible sources that we know about that should yield gravitational waves. It'll take different sensitivities, possibly different equipment to do some of them. But I've listed them here. I'm going to kind of walk through it so you can see from the standpoint of the science what we might uncover in the coming decade or decades from earth-based experiments. I'll go on to talk about experiments that aren't even earth-based later. So so far, what we've done is completely confined to this top picture that is compact binary systems to binary objects that are like the earth and the moon going around each other, captured gravitationally. As they go around each other, because of Einstein's theory of general relativity, there's accelerations involved. They radiate away some energy and slowly in spiral toward each other. And as they get very close to each other, they're going faster and faster. And that's because we're here on earth and look at very high frequencies, the part of the problem that we see. So we see the final merger, the cycles around each other and merger of two objects that are very dense, so compact objects like black holes or like neutron stars that aren't as compact as a black hole, but much, much more compact than the earth or the sun. And we have search techniques for that. We haven't finished that problem by any means. So I'll talk about it a little bit more. But first, let me review quickly what we've done. So in a general way, I draw a picture here, which I did many years ago by hand of what we anticipated, we see, of the three phases of what happens when two compact objects come together. First, these objects, just like the earth and the moon, when they're going around each other, are spinning themselves. So I draw them as spinning. But you'll note, when I talked about the events that we've seen, we haven't even considered the spinning part yet. It's one thing that we will in the future, but we need better data to do that. I wrote down some formulas. Those formulas can help us extract the spin, but we're not good enough yet to do that, except for the final object. We can tell the spin of the final object if it came together, but knowing the spins of the two individual ones, we can't do yet. If we could, we would have a much stronger handle on what created these black holes that come together. So it's a future thing that we'll do as we get better data. Anyway, that creates this so-called chirp signal. This is my hand-drawn picture of what I showed you in the data, a few cycles or many cycles, depending on the frequency. If we look on the right-hand side, what I show is two small objects compared to two objects have more cycles. They have more cycles, meaning not that they really went around each other more, but they have more cycles in the frequency band that we can detect. That is, we can go down to where our ears go down to tens of hertz and up to thousands of hertz. And so to get up beyond 10 hertz to higher frequency, lighter objects will go to higher and higher frequency. So our first picture is I quickly know whether I have a very heavy binary system coming together, like this one, or a light one, by more or less how many cycles I see. And that's the kind of analysis that we do. So so far, I've drawn here the two ones that we've seen, neutron stars scattering off neutron stars. I'll talk about that slightly more in a few minutes. And initially, two black holes colliding. And that one required some advances in our ability to do general relativity, because in order to look at all the possible forms that these black holes might have coming together, we needed to be able to do it on a computer. That's called numerical relativity. And it only developed theoretically and computationally in the same time scale that we developed the equipment. So it wasn't something that could have been done 20 years ago. There's one left out of here. And that is black holes, a black hole and a neutron star, a heavy object and a light object, like the Earth and the moon. And there, we expect to see that. It'll be very interesting, because the black hole, we understand very well, then we can take the nuclear object and try to understand how the tidal waves pull it and so forth. It's difficult for us now, because the difference is theoretically, not just experimentally. It's difficult, because when the masses of the two objects are so different from each other, we don't yet know how to do the calculations very well. If we don't know how to do the calculations, we don't know how to look very well. But so far, we haven't seen them, but it's one of our big goals for the future. So the general picture of a binary system coming together looks like I've drawn here. This is actually the fit from our data for the very first event that we saw, where we saw about eight or nine cycles, and it came together. So this is the in-spiral phase. It can be calculated from Newtonian calculations at the beginning, and then what we call post-Newtonian, which is using general relativity. And finally, when they get strong in here, we have to do this calculations of general relativity on a computer. This final business, where it comes together, tells us how far away the system was by how much energy is there. And finally, all the features of it have to ring down somehow. And that's this picture here. And we look at that as well. So that's basically what's there. We have, as I said, created an instrument to do that. The instrument itself, just I'm reviewing somewhat first, is dependent on watching the fact that space will be changed a little bit, stretched and compressed by the passage of a gravitational wave. The picture that I use for that, I repeat here, is shown here. And what you should visualize is those four little dots on there are free masses. That is, they're free to move. And if a gravitational wave comes through, it'll first elongate it so that it's taller and thinner, and then a half a wavelength later this direction. And this amount, delta L, is proportional to the length that this has across it times how strong the gravitational wave effect is. And it's a small number, which I pointed out before, 10 to the minus 21. Because it's 10 to the minus 21, we try to make it a bigger number by making a very big apparatus. And that's why I show you a large apparatus. And the apparatus is kilometers. So the challenge that we have is to measure something that's 10 to the minus 18 meters. And let me emphasize how small that is. A small number, sometimes you just know that it's small. But we all know how big a meter stick is. And that's so big, kind of. And we also know how big a human hair is. We all can look at it with our own eyes and resolve a human hair. It's 10,000 times smaller than a meter or 100 microns. We also are familiar with the fact that this laser beam is a light and light has a wavelength. The wavelength of the light in the laser beam is about 100 times smaller than the human hair or one micron in size. And we no longer can see by eye the wavelength itself, although we can see the hair and we can see the meter stick. So now we need instruments to see things that are smaller. And all of us know the next big scale is the atomic diameter. And it's actually 10,000 times smaller than the wavelength of light. So that's getting pretty small, or 10 to the minus 10 meters. And of course, there's a lot of atomic physics and a lot we've done with atoms. The size smaller than that is what we use when we go to the CERN accelerator or a great big particle physics places. It's the size of a proton. And a proton is 10 to the minus 15 meters or 100,000 times smaller than an atomic diameter. That huge jump is why we need these huge particle accelerators to study the effects of protons or other elementary particles precisely. And we need a lot of energy to study them at this kind of distance. And what we're challenged to do for gravitational waves is another factor of 1,000 smaller than the size of a proton. Of course, that's impossible in a single measurement. We do it by having lots and lots of photons. And it's by doing lots of measurements of the same thing, and basically you're able to by the process of, in our case, interferometry to do the measurement. So the magic that allows you to go to something much smaller than the proton is having lots of photons making the same measurement. We built detectors to do this, which are called interferometers, one in Livingston, Louisiana and one in Hanford, Washington. Livingston, Louisiana is in the middle of a commercial pine forest, pine trees that are used to make paper and wood. And in Hanford, Washington, it's on government property, a large laboratory that was used to do separation originally on reactors for making nuclear bombs years ago. And now it's a great big defense laboratory. We have nothing to do with that, but they have a lot of land. And we live off in a corner of that facility. This is a picture of the two laboratories, just so everybody, if you weren't at the other lectures, can see it. And this is the signal we observed in September of 2015, which signaled the fact that we saw gravitational waves. So what you're seeing here is the real data that looks something like the picture that I drew earlier with the wiggles that get bigger, get narrower, and come together with some ring down. The fact that it's more jagged is because we're not yet able to measure them really precisely. We're just getting good enough to measure these kind of things. But this still looks very much like the picture that I drew. And more impressively, what's seen in the two laboratories is essentially identical, if I put them on top of each other. So if I take that data and I ask how it looks compared to Einstein's general relativity, the picture that fits the data is shown here. And that's these cycles here getting narrower, as I showed, taller. And when they merge together, starting when they're far apart, coming together, finally merging, and then giving this little ring down. And I emphasize on this that this picture here is two incredibly compact objects, and they're not very far apart, I'll show you. Going around each other at this velocity by Einstein's equations. By the time they come together, they're going at more than half the speed of light. And when we start detecting them, they're already going about a third the speed of light. The other curve on the bottom, which is going down, is how close together they are. The units on the right are called the Schwarzschild radii, but to translate them, they start out about 150 kilometers apart and merge together to no distance, of course, by the time they come together. Just to emphasize all this, I draw a map. So there's a map where Bern is somewhere here, Geneva here. And what we've seen when we interpreted by Einstein's equations, I put on top of the map of Bern and Geneva, and it's about that distance apart. Each of these is roughly 30 times, one of them 36 times, the other one 29 times, the mass of our sun concentrated in this small area, not bigger than, say, the size of the city of Geneva. That each one of those is 36 or 30 times the mass of our sun. To translate that, that's 10 million times the mass of the earth. So each of those, you have to imagine 10 million times the mass of the earth concentrated in each of these balls. And they're going around each other at half the speed of light. So that's what's happening. And it happened 1.3 billion light years away, merging into each other, and then we detected it on the date that I showed you. This is a picture of the reported, as of a few months ago, the reported events that we've seen and published in the literature of black holes coming together. They're different from each other, as I show you. Because of the picture I do earlier, where if the masses are less, they're going to show more oscillations. So this picture here is lighter than this one here. We saw this four or five months later, and it's got many, many oscillations, as you see, but smaller. And it turns out, by having many, many oscillations, when we look at these, we see how well we can test general relativity. And of these on the picture here, the one that tests it the best is the one actually in the middle with a small signal. So that's more or less where we are with black holes. To go on, we saw a year ago, August, a signal from a different object. This is neutron stars. And by this time, we had three detectors, one in Italy, as well as ours in the states. And you start to see this as frequency. This is time. This is the signal. You're hearing the gravitational wave signal. When it gets to your zero, you'll hear the final place where it increases the frequency very quickly, and you'll hear a chirp. Maybe put slightly. And that's just raw data. So that's what we hear just saying. This is, characteristically, really different from what we saw before, even though it's the same picture. It went for almost a minute, 30 seconds or so of the part I showed you, as it was actually almost a minute in our detector compared to two tenths of a second in the discovery event that I showed you. We saw it in three detectors. With three, we could triangulate and see where it came from. And that's shown in this picture here. We saw the event in our detectors right here with this signal that is the so-called chirp signal. Using three different detectors, two in the US and one in Italy, even though they have different sensitivities, we were able to tell where it was in the sky. If we use only our two detectors in LIGO, which I've talked about in these lectures so far, we can tell that it was a picture of the Earth, that it came from either here or here. We couldn't resolve which. Once we added the Italian detector to it, we could tell that it came here. We were very fortunate that two seconds later, a satellite that is an experiment looking for high-energy gamma rays coming from what's called gamma ray bursts saw a signal and it came from the same part of the sky, shown here. The combination of those two gave us confidence to alert the whole astronomical community and of the roughly 4,000 instruments of all sizes all over the world, 2,000 or so actually pointed at this and took data. So that meant that we saw it in gravitational waves that was seen in gamma rays as well and then looked at, and on this picture here, this is the data, this is time this way and this is gravitational waves, gamma rays, x-rays, ultraviolet, optical, infrared, even radio waves and people have looked at that place in the sky where we even determined quite quickly what galaxy the signal had come from and the phenomenology had been done to see the phenomenon of two neutron stars coming together which matched a particular phenomenological theory which the author labeled a kilonova like we have a supernova for the collapse of a star. This to me is an illustration of the beginning of, I mean it's nice in itself but it's the beginning of a way that science will be done with gravitational waves and with neutrinos in the future and that is what we call multi-messenger astronomy. I point out that astronomy itself, if you attributed what made the biggest, technically what has caused the most advances in the last say 50 years, it's the fact that in astronomy we now have instruments that look in the visible, in the infrared, the ultraviolet and so forth and the same phenomenon or have been looked at in all the different wavelengths and it's enabled us to do the astrophysics and understand what the different sources are that are studied astronomically. Now we have the ability to not only look at all the instruments that do astronomy which uses one form or another of electromagnetic radiation but also look at gravitational waves from those sources if we're sensitive enough and maybe also even neutrinos which come from a very different kind of interactions within them. So this is one direction in the future that guides us to want to make sure that as we develop our instruments in the future, which I'll talk about in a little while, that we make sure that we have good earth coverage in order to be able to point so that we can do multi-messenger astronomy in the future. Another result, a kind of interesting result that came out of this first merger of two neutron stars I show here and everybody is aware and learned somewhere in school the periodic table which I'm showing here. And you probably recall in your lifetimes that you've read in the newspaper that a new element has been found and the periodic table's gotten a little longer and they name it something on the very end. So this has been kind of an active field but there's been a puzzle for physicists for a long time and that is where do the heavy elements come from? Where when the earth was formed and how did we get heavy elements buried in the earth? Most of the like gold or platinum or whatever that we go mine down and try to find. So how did that happen when the earth was formed? That's been a puzzle because the universe is almost completely made out of hydrogen and helium so that's not heavy elements. The way we make heavy elements or know about the universe making heavy elements there aren't very many in the universe comes from when a star burns up all its fuel and has what's called a supernova or collapses and when it collapses it makes heavy elements but how heavy? The process by which a star burns is the fusion process and fusion starts by the light elements making fusion just like fusion bombs or fusion energy and as the star burns up some of the light elements it moves up to heavier ones and heavier ones and eventually what causes a star to collapse or have a supernova is that you burn up the elements up to where the nuclear process can't go anymore and gravity which is trying to pull it in then is the inward force, the fusion is the outward force gravity wins and it collapses and makes a neutron star or a black hole or something like that. So we understand very well then that stars have died in the past and so that makes elements up to iron but the elements go well beyond iron gold is beyond iron. So how do we make the elements beyond iron? Physicists are very good at inventing some schemes so nuclear physicists invented a process called the R process and the R process is a way that kind of is an invention that isn't very satisfying but was physically an explanation for how in the collapse of a star you could make some heavier elements. Anyway, I'll keep talking while you hopefully get that back. So anyway, we can make heavier particles heavier elements through the R process but it's kind of a concocted process, thank you. It's a concocted process that was never very satisfying theoretically it was invented to do it experimentally. If you ask how we know all these heavy elements are there we know how to make them in the lab is the point and in the lab we do it by bombarding a lot of neutrons on some reasonably heavy element and then it makes a heavier one and so that's the usual process by which heavy elements were made. That's exactly what's happening in neutron stars when they come together. You have a star that has now nuclear matter mostly neutrons, they come together and so it's much more like what we do in the lab. We've only seen one example so you can't determine that much about how often something happens or what all the science is from one example that stands for the future but using the one example this is one analysis of how much of the heavy elements in the earth came from neutron star mergers in the past obviously not ours but in the past and the yellow parts in here are basically what came from the neutron stars versus other ways and you'll notice your favorite heavy metal like gold or platinum like on your ring finger probably came from neutron stars merging together in the distant past so that's an interesting observation that came from this first observation. Okay, let me project a little bit toward the future. We measure how sensitive our instrument is by more or less how far out we can look so I told you we measure sensitivity in terms of a distance but what matters for science is how far out you can look. We in order to get a parameter to measure that against we do a calculation of what if we have two neutron stars merging together, how far away could we see them if they're an orientation? This perpendicular to us and in the first time we ran this instrument and made the discovery we were here and this is the distance in astronomical units 60 to 80 megaparsecs I just think 60 to 80 times 1.5 is the number of million light years away and as we've developed over the last year or two we more or less doubled that distance and we're just about in 2019 to start again. We've been improving the apparatus and probably in the next year or so we'll be running with the unit more than twice as good as we were two years ago and that'll continue so that'll continue through the next without doing anything radical this is just changing our apparatus by improving the laser by improving the isolation from the ground by improving the materials and the optics and so forth. Near the end, the middle of the next decade somewhere in here we'll start to make some more sizable changes for example maybe cooling the detector and so I don't know exactly what that'll give us yet but we're working on all those things so the message that I wanna give you is that these detectors are gonna get stepwise which have to be a little bit patient they're gonna get better and better in terms of sensitivity and each factor of two that we improve the sensitivity we improve our ability to see more galaxies or more of the universe by the cube of that because it's the distance out we look and we increase the volume so if we make an improvement of a factor of two in the sensitivity of the instrument we get a factor of eight in total event rate of what we're able to see so that's the straightforward thing that's gonna happen over the next decade. The second is that we will have more than we barely have three detectors now but we'll have the third detector in Italy will catch up with us in sensitivity we hope and there's two more detectors that'll be added by the next five to seven years one in Japan and one in India the one in Japan is interesting because they are actually trying to in some sense leapfrog us in some ways by for example going to cooling the detector which makes it less noisy right from the beginning and so they if they succeed technically that'll be very nice the one in India is being built by the LIGO collaboration along with an Indian collaboration that's doing the facility itself so we'll have five of them that'll make the multi-messenger astronomy that I talked about much more precise so what I showed you so far was here the event that I showed you where we pointed very well was lucky because depending on where something happens now we happen to have three detectors in the Northern Hemisphere one in Italy, two in the US and we therefore have regions where if we see events these little circles are elongated banana-like shapes are how accurately we know where the event came from to tell astronomers to look at them what we want to do is get to something like this and that's where we'll be by about 2024, 2025 when we have the Indian and the Japanese detectors on and at that point anything that we see in gravitational waves coming from any direction we should be able to accurately tell the astronomical community where to look and how to look and so that should really help this idea of being able to look at gravitational waves and astronomical phenomenon together over the next decade or so and so I anticipate that that's gonna be a big thing I've shown you how the detector sensitivity is and it follows a line on this side that's limited by the shaking of the earth it's limited on this side generally by how much light you have and somewhere in between by the fact that we work at room temperature these are lines that I'm not gonna go through in detail of the improvements that we can make if I just take and by brute force which is not everything that we'll do improve the detector by just doing realistically what we could do if we want to and have the money and the time to just make it better without doing anything that's innovative make the test masses which are presently 40 kilograms, 100 kilograms use a better material for the mirrors right now we've used few silica pure silicon crystal would be a much better material if we lower the temperature then we reduce the noise in the instrument if we improve the coatings that make it a mirror we can do better and right now we don't use a coating that matches very well the temperature coefficients of the mirrors themselves and we could do much better and are working on that and we can increase the power of the laser itself and have more photons that's just examples of the improvements we can do and probably will over the next decade without being super innovative what that will do which is clear to us scientifically is that everything we've seen so far that's just down here everything we've done so far is really not very far away and not very early in times or a long time ago it's what we would refer to as not being cosmological if we go see further out and where there's what we call a redshift then we start seeing cosmology with gravitational waves which I think is a next big step for us and just doing this will enable us to move into the cosmological region the second improvement is that if we improve the detector a factor of 10 and we saw an event that looked like our first one they obviously exist the first event we had had a signal to noise you saw it over the noise of 24 to 1 by the way we measure it if we improve the apparatus which I'm showing you here to go from here to here by a factor of 10 the same event would have 240 to 1 signal of noise by having that the formulas that I showed last time of how we extract the information will enable us to extract information for example on the spins of the incoming to black holes as they come together and that is we think the key to understanding our A key to understanding what the origin was of these black holes themselves so the improved signal to noise is a big step in terms of our ability to analyze even a single event and lastly the event rate itself compared to what you've heard instead of being once every couple months as we move forward it's gonna be probably we're gonna be registering a gravitational wave event every week or so so that's more or less just improving the detectors that we already have and I'd say it's bound to happen I don't know that the time scale will work all in the time scale that I gave you but there was nothing very difficult there we will do more difficult work on these detectors if it's work that we think will apply to a future generation detector we're just now starting to work in detail on how we would build a next generation gravitational wave detectors here on earth it'll go beyond even the improved versions of what we've built so far most of the really good work on this has been done in Europe and so I'm gonna show the European plan which may or may not be what will end up being the plan we were basically forbidden to think very hard about next generation detectors by the National Science Foundation until we saw gravitational waves so we only could do it on the slide while in Europe there was a study program that went on for quite a while so their ideas I'm talking about I don't take any ownership we are actually thinking a little bit differently about it but the idea here is to make first detector that instead of being on the surface is deep underground like particle accelerators are how does that help you? That actually helps especially the seismic background which goes away the shaking of the earth goes away very quickly as you go underground and especially at the low frequencies so the first big step in going underground is that it'll improve the detectors at low frequencies low frequencies is where we detect all the black holes so the ability to go to yet lower frequencies and do very well at low frequencies would be enabled a lot by going underground clearly there's a penalty going underground it's more expensive to build something underground than on the earth's surface but we do it for and this is simpler because the long arms are just vacuum in many ways than a particle accelerator underground a topology that looks attractive is to build it as a triangle instead of as an L-shaped and the idea there is that the beams can go around both ways like they do in particle accelerators and that you can doubly measure things because you measure basically you have six interferometers if you have the beams going both ways around and have three vertices so there's a lot of redundancy and a lot of details and the size can be realistically the size of a large accelerator underground 10 kilometers or so per arm so those are the obvious ones the next one is to make it cryogenic that is to cool it down not just maybe a little bit but to cool it down to an optimum temperature that requires some R and D but it's certainly doable the question is you have to be able to cool it down without shaking it at all and you have to have some knowledge which we have to do R and D on to understand what is the right temperature to go to and what are the right materials and materials to coat the mirrors to use if you go to go underground also if you use a configuration like this it's possible to tune the detector right now the first detector we have basically covers as well as we can 10 hertz to 10,000 hertz the audio band what you can do if you build the right kind of detector is make a trade-off make it be able to run much better than it might at high frequencies at the penalty of not doing low frequencies and vice versa so they have in the design of this Einstein telescope which is what the Europeans named their study the ability to have a configuration optically that emphasizes the low frequency a different configuration optically that the equipment's the same that emphasizes the high frequency and all that is a big step beyond what we are presently doing in LIGO so the take home message I would give here it may not evolve just like this the cost of this is doable it's still less than a very large accelerator because the arms don't have instrumentation all along them just in the corners so despite the fact that that instrumentation is very sophisticated it's still much less than a very large accelerator so it's probably affordable if large accelerators are affordable and it's a path that one can foresee in the next 20 years or so so what I anticipate happening on the ground for us technically is that we'll keep improving in steps as we have for the last couple years over the next decade the present detectors and add one in Japan and one in India and in the 2030s maybe 15 years from now move to a next generation detector which may look very different than this one that I showed you or may look a lot like it we just don't know yet we're starting to do worldwide studies together to see what the best configurations are for a future detector so that by the time we're ready to ask governments for support we know what we want to do but that's probably five years or more away so that's to set the stage for what's possible now I want to go back to the science so I've concentrated so far on the binary systems the next possible set of gravitational wave signals that we might see is birth six something that gives birth so what gives birth we actually saw that in a sense in this neutron star business but that was still a binary system but imagine a supernova the collapse of a star so when a star collapses after the burns up the nuclear fuel and it collapses if when it collapses there's some sort of quadrupole moment you'll remember there has to be a quadrupole moment to give a gravitational wave signal then you'll get a burst signal very different from what I've shown so far what do we expect in terms of whether or not there'll be a significant quadrupole moment in the collapse of a star we're pretty sure there will be because when stars collapse the final product like a neutron star typically goes away moves afterwards by a few hundred kilometers a second so that's known that would only happen if the collapse was completely spherical the final object would stand still so the fact that it on the average moves means it isn't completely symmetrical however it's again one of these things we can't calculate very well physicists worked very hard to try to understand independent gravitational waves to try to understand how a star collapses and there's huge computer programs that in places like Livermore lab which I'm familiar with because I'm near there to try to do the dynamics of the collapse and they can't consistently simulate yet on a computer the collapse of a star and when they're doing it in order to make a star collapse after they simulate the burning of the fuel they assume spherical symmetry so we don't really get any information on the gravitational waves so we don't yet have the phenomenology to know how strong those signals might be but we expect from just observations that they're gonna be there so where will a star collapse? If a star collapse inside of our own galaxy the last time that happened was the time of Galileo it's certain that both neutrinos and gravitational waves can be detected I mean we can calculate enough different ways to make sure that that signal is possible but if we want to be able in a finite time to see that a star collapse they don't happen very often we have to be able to see a gravitational wave signal from a gravitational collapse about as far as the Virgo cluster if we were sensitive to any gravitational wave collapse of some star out to the Virgo cluster there's basically about one a year that happens and so we would see those signals we don't know yet where the real sensitivity is but I think one of the big targets that we have to do in the future and could happen very soon or might take decades before we see one is to see the collapse of a star the gravitational waves that comes from that and that we're looking forward to I might comment that people who build big neutrino detectors also look for that as a major signal because of that we basically have ourselves alert all the time we never turn off all gravitational wave detectors at the same time when we want to improve one we make sure that one somewhere is on in case there's a collapse of a star close enough that we should have been able to detect it it would be awfully embarrassing if we were just turned off so that's the second type signal I can't guess when we'll detect it but it could be anywhere from the next 10 years to the next 50 years I think but it's almost certain that there is such a signal and it'll give us incredibly more information about what happens when a star collapses when a star collapses we first have the force of the fusion process holding it out and holding gravity apart it's the gravitational collapse itself when gravity wins after the fusion process ends that's the collapse that's the first thing that happens when everything comes together there's all kinds of nuclear physics and that emits neutrinos which neutrino detectors can see and finally there's a shockwave that when it hits it makes light and is seen in telescopes so basically this is an example of something that'll be seen when it happens by all the instruments but we haven't had one really close to us like our own galaxy since Galileo's time the next kind of source I'll come to in a minute I'll talk a little bit more about this one what I'm showing here is the scheme which I think I'm gonna skip except for a few words for how we look technically for a collapse of a star how we have an alert system looks for it we basically have a picture where we graph time in one direction frequency in the other direction and look for a clustering of a signal and we have that alert system on at all times so we're able to in an unmodeled way which is always hard in science to try to measure something that you wanna find but you don't wanna bias yourself what it might look like and so we've worked very hard to build a way to search for collapse of stars not biasing ourselves about what the form of the signal might look like and this is what this part is about the next kind of source is pulsars in our own galaxy the final product of many stars that collapse is to make a neutron star and the neutron stars look like this basically a neutron star is not gonna be the product of the collapse of our own sun but most stars that aren't heavy enough to make a black hole the nuclear physics, the gravity collapses it to a small size we call a neutron star because it's very neutron rich they typically are about one and a half times the mass of our sun in the final product but they're only about 12 miles or 20 kilometers across you can think of them as we think this is all phenomenological not from data they have a crust that's maybe a 10th of the size of a thick and then inside liquid of heavy elements that are made mostly neutrons inside and they're most likely spinning if they're spinning and we know they do the ones that we see the products of stars that have collapsed in the past make what we call radio pulsars and those were discovered tens of years ago and they happen because of kind of a lighthouse effect so if the star is spinning and it's made out of, it has electrons and other nuclear matter in it it has charges that go around which make currents and the currents make fields that maybe radiate away radiation along the axis and that's what's shown in this picture here and the observer only sees the signal when it points it to so it's kind of a lighthouse effect a neutron star is spinning somewhere in our galaxy and as it goes around it's radiating along its axis the radiation in terms of radio signals and that radio signal points at us and we see it so what we know about radio pulsars usually are what their frequency is and how stable they are and so forth and so on and we've looked a lot for radio pulse signals for gravitational waves for these pulsars and so far haven't seen any they would come about for the same reason if you have a spinning system and that system isn't totally spherical then if it has little mountains on it for example then it would give a quadrupole moment and we would see the signal it's one of the active areas that we look for and we have looked at the many of the known pulsars and haven't seen any signals yet let's see we know that the most likely source of gravitational waves for pulsars are pulsars that are let's say young are newly born from a supernova that happened and then the pulsar is made but it's wobbly and so forth and then as it gets very old it's very spherical and then it gives a uniform signal for radio waves and then they're discovered by radio telescopes the ones that radio telescopes have and we've searched for all those there's several hundred in our own galaxy are the worst ones to give gravitational wave signals because they're so old that they're spinning very uniformly they give a uniform signal for the radio waves but that's just what we don't want we want the ones that are still wobbling around and so forth therefore we have to look in the sky not having the aid we've looked at all those so far we don't see them well instead the better way to look is to look everywhere in the sky ourselves for signals from periodic sources the problem there is that when we do that the frequency of the signal is modulated by the moving of the Earth's own motion relative to where this pulsar is and the orientation compared to our apparatus itself changes the amplitude when you look at all that and take the whole sky and you want to map the whole sky where we don't know where we're looking for them because we don't have radio telescopes the problem turns out to be well beyond orders of magnitude beyond what we can do with our computers so we can't, so we're in this bind if we look at the ones that are easy to look for we can look very carefully but we don't see any but we don't expect them very much if we want to look for the other ones we're totally limited by computing I'll come back to that in a second to give the gravitational wave signal something about it is going to be not totally spherical examples are ones that are creating some matter or ones that are bumpy in nature or ones that are wobbly those aren't the ones that have been detected by radio telescopes but the younger ones have all those features before they settle down so this is the search we've done we looked at 200 known with the same data that discovered gravitational waves we've searched for them there's 200 dots along here we basically have set limits on the size of the signal for those known pulsars that give the same little H that I talked about before where we look at 10 to the minus 21 but because it's a continuous source we keep looking at it over and over again we get down to an incredibly small number 10 to the minus 26 but we don't see anything we can set a limit on how elliptical it is compared to being totally spherical and that's something like 10 to the minus 8 a very small amount it's less elliptical than that that translates to saying that any of these things don't have a little mountain on them more than say a millimeter so physically but as I said they're not the ones that really matter to us the most in terms of making it a discovery we want to look at the ones that aren't being seen by radio telescopes but we're limited by our computers so what we've done is create a system called Einstein at home when you go home you can look it up and if you're feeling generous you can give us your background cycles on your computer we borrow them or use them and give you credit if something's found and we're using that to help us have enough computing power to actually scan through the whole sky we send each piece of the sky to three different computers and we do all the work after that but it's a system so if you're so inclined look for Einstein at home on your computer we have about somewhere between I don't know what the number is now something like 20 times as much computing power by using background cycles and people's computer than we do in the computers that are captive in LIGO so if you're generous come back the next source that I haven't talked about yet is probably in the long term the most important and most interesting one and that is the stochastic background or the signals that would come from the early universe and in this case this is the real pot of gold at the end of the at the end of the storm if you want that is in my mind the most important and interesting source that we know about I always think the most interesting source is the one we don't know anything about that we'll find but the cosmological signal from the early universe is particularly interesting because gravitational waves uniquely will go back to the very first instance of the Big Bang if we look now at what we know about the early instance of the universe that almost all comes from photons electromagnetic radiation from these maps using the cosmic microwave background signals but because they're photons and because there's so much density at the early times time goes this way the photons are absorbed anytime earlier than I've been generous here it's about 300,000 years after the Big Bang so despite the fact that we have incredibly sophisticated instruments that have been trying to study the early universe they're limited to 300,000 years after the Big Bang in principle you can go back to go back earlier you need a probe that doesn't interact didn't interact when everything was so dense neutrinos are a possibility it could go back to the first seconds or so of the Big Bang but unfortunately and I used to do neutrino physics the problem is that in all the process that neutrinos had to get from here to get out they've what we call thermalized they've lost their energy, interacted a lot and lost a lot of energy if a neutrino is very very low energy it turns out it's almost undetectable because the cross section depends on the energy so I think but I don't know if everybody agrees that's doing this that neutrinos aren't very realistic besides they only go back to the first second if you want to go back to the very beginning then what you want is gravitational waves because they basically can go back to 10 to the minus 43 seconds after the Big Bang and you can then see and map everything that happened of course if we could do that I'd be telling you about it we don't know how to do it yet but that I think is the ultimate goal of this science probably from the earth but maybe from space and not in the detectors that I've shown you yet because we're not good enough I'll show you that so the signals from the early universe are usually written down in a formula that I give here that has to do with the energy density that you need to what we call close the universe and I'm not going to explain that but the detectors are what you do is cross-correlate signals from two detectors look for correlations compared to just pure noise that limits you and the detectors if you see correlations then that could come from the early universe of course it takes work to do that it takes not having backgrounds to do that so we do that we look at signals I can do it on my laptop I don't need a fancy computer from our Hanford laboratory and from Louisiana we cross-correlate it just the noise signals and see if there's any correlation and there isn't any so far but you need to do that much more accurately we've done that and set some limit on basically what we have to close the universe but what I show here is the history the early universe is back here this is frequency so 10 to the minus 20 seconds hertz we're out here if you remember this is the audio band so where LIGO is is not the ideal place to be looking for signals from the early universe you want to be back this direction some it might be that moving in this direction we can do it in space I'll talk about that in a minute but the problem technically becomes harder so it's hard to do that and the models that we have of the early universe which may or may not be right when extrapolated to very high energies I show one that's popular called slow roll inflation here our orders of magnitude lower than we are now we've been improving and we publish a paper saying we don't see anything but I expect that in the distant future that one way or the other we'll be able to get to where we see signals from the early universe in gravitational wave detectors not in our detector now but in gravitational wave detectors and it's the ultimate goal in my mind of this science so what I've shown so far then covering frequency we've talked about mostly because that's what I've done LIGO working in the audio band where for example the neutron star coalescence came here our first sensitivity was maybe here and we're down in the region where we're better than that so we can see anything above these lines this is advanced LIGO when we can go in space I'll talk about that in a minute we look at a different frequency band that's here and there you could see the same black holes that we see earlier or some other kinds of unresolved galactic binaries in a different way and so this experiment to go in space is called LESA I'll talk about it in just a minute and let me go on a third one at lower frequency yet is a scheme that I'll also talk about in a minute I'm just previewing it which gets you to even lower frequency and that's a pulsar timing array and it's looking at known pulsars which work like clocks and if a gravitational wave comes through it distorts the time enough so that you see a signal by having a whole array looking at different pulsar signals that hasn't been done yet and this hasn't been done yet but both of them are being worked on and in the next 10 to 20 years I'm pretty confident that both will be done let's talk for a second about the space one so the LESA what's called LESA which is by the way a European space mission involving a whole set of European countries but the elite countries are Germany and Italy and this started as a joint LESA NASA project but because of financial problems in NASA NASA's either gonna be a minor partner or not a partner at all that's not resolved yet so this is a European program that I'm talking about it consists of three satellites separated by more than a million kilometers something like 2.5 million kilometers and they go around each other as I show here go around the sun so here's the sun they're put in an orbit where they go around like this and that gives a sensitivity curve that looks a little bit like ours but from 0.1 to 10 to the minus four hertz instead of 10 to 1,000 hertz and 10 to 10,000 hertz and this shows for example a binary system that they could detect that's lower frequency than we detect when we're out here so this is rich in possible sources that they can detect the technology has been challenged a lot and the reason we were able to detect gravitational waves before a space mission went it was questions about the technology before a mission went into space the same year 2015 when we detected gravitational waves they finally were able to put up a test mission called the Pathfinder for Lisa and it was a brilliant success they had to convince the authorities to give the money for the real Lisa that they could make basically a free mass that can move and do interferometry in space at a certain level and this was what they were supposed to do in this Pathfinder this is the requirements of Lisa itself and the Pathfinder itself essentially reached what the real mission is supposed to reach the experiment involves then two satellites, three satellites but between any two of them a system on the satellite that's free to move and a system then that's married a million kilometers apart to one and another satellite and basically you're looking for the movement of this in a closed triangle and that mission is one of the big missions approved by the European Space Agency unfortunately it takes a long time to do things in space and its present launch time is 2034 so I think this time scale usually doesn't short the my colleagues that work on this think they're going to make it faster because we discovered gravitational waves but space missions usually take longer I think that we'll have a space mission a very good one on about the same time scale as the next generation of surface of detectors on the Earth's surface so we'll be improving over the next decade the ones that we have and in the 2030s this science will move to having a very sophisticated instrument in space and a next generation instruments on the Earth's surface the third technique that I talked about was pulsar timing arrays so here we have instruments they're trying to do this now but so far haven't a good enough array and that is that you have sensors looking at a whole set of pulsars at the same time if low frequency, much lower frequency gravitational waves than we're detecting go through space around them it'll change the path length effectively or the timing, the frequency of a set of pulsars if you have a whole set where they all change systematically in some way you can reconstruct what the gravitational wave was that caused that and that is being done already but not good enough so the kind of incrementally they're improving the ability to have an array a pulsar timing array and it wouldn't surprise me to see them start to detect signals within the next decade so I think that will happen or maybe not but I think they have a good chance to do it within the next decade so as I said before the early universe is maybe the ultimate goal we don't know how to do it yet with gravitational waves directly but there is a way indirectly and that is that the way we have studied the early universe with a cosmic microwave background signals is shown in this map here, the different colors and if it's possible there's a small signal that could be left there as an imprint of what gravitational waves saw at earlier times and people have looked for that unfortunately haven't thought they saw something but didn't but again it may be possible to see before we ever can do it directly the imprint of gravitational waves on the cosmic microwave background signals which will give us insight into it's a way for them to be able to break through the 300,000 years after the big bang that they're capable now of studying so if I put this all together it looks a lot like astronomy in that we do astronomy at all different wavelengths now so I've summarized in this picture that at the highest frequencies where we started we're working on phenomenon that kind of go from seconds to milliseconds that's the speed of what we looked at two tenths of a second to see the merger and that's pulsars and supernova and mergers and so forth we soon in the next decade or two we'll go into space and something like Lisa and there's other space proposals for example in China and Japan that might come about and that compliments this by looking at the lower frequencies that's 10 to the minus one to 10 to the minus four Hertz our phenomenon that takes seconds or hours to happen they're not as dramatic as what we see and that's then some examples of that are mergers with extreme mass ratios or seeing the black holes that we saw but at earlier times before they come together finally the pulsar timing arrays go to yet lower frequency and I just talked about them briefly just now and they could be operational as early as the next within the next 10 years or it might take a little longer I don't know what issues they may find I'm not close enough to it then we could go to yet earlier times by seeing these patterns on the cosmic microwave background signals and that is a question whether and when that can be done as the cosmic microwave background detectors become better is a background question and we don't really understand the backgrounds well enough now so we don't know whether or how this can be done if I take this whole picture and the start that we have that we've seen nothing almost we've seen the merger of a few black holes and one neutron star binary system come together I'll make the presumptuous analogy to astronomy so astronomy started in 1608 when Galileo used lenses that originally were being developed at that time for eyeglasses and made a telescope that not the first telescope but the first telescope that was used in this way and looked at Jupiter and he looked at Jupiter so it's the first time without the naked eye that somebody did astronomy he looked at Jupiter and he saw that Jupiter had four moons so that was a discovery that's a little bit like us seeing gravitational waves for the first time that was very important by the way because it was important in understanding that celestial bodies giving evidence that celestial bodies go around the sun and not some other solution so it had some historical significance but it's not my point my point is that this is where astronomy started it's been 400 years in 400 years astronomy has evolved incredibly to modern incredible instruments looking at different wavelengths and doing a lot of physics a lot of astrophysics and we know a tremendous amount about the universe from all the electromagnetic radiation that's been done for the first time we've now seen within instrument a different source of signals from the universe and that's gravitational waves from for black hole mergers and one example of the neutron stars with a lot of things that we know about that we should be able to see in the coming decades and so it's my belief a little bit of optimism maybe that if you invite me back in 400 years I can give you a talk like we would now about astronomy but about gravitational wave astronomy so anyway this is my end I wanna thank the organizers for having me I've had a great time in addition to coming here we managed to go see the Paul Clay Museum today which is a fantastic place architecturally designed by Mies van der Rohe and half of Paul Clay's art is in this museum here locally because he was Swiss I also visited the Einstein house with our host who gave us a great view of Einstein's history and his history here in Bern and I think this picture actually was during the period of his Bern years and lastly then thank you and all the thanks go to you back to you and you gave us a great impression on the future what astronomy will be in the next three 400 years and before we live through that let's see whether there are questions you were speaking about the virtue of these two neutral stars then you said that between you detection of gravitational waves and the detection of a Fermi satellite I don't know was it X-rays or was a lapse of two seconds what happened in these two seconds okay so the idea of a neutron star merger is there's different science going on we're looking at these two objects coming together the signal that comes out afterwards is when the nuclear physics is happening so once they merge together then you have nuclear physics happening under very compact conditions and so that's sometime later nobody can estimate exactly how much but we're measuring the collapse itself they're measuring the nuclear physics that comes afterwards so the delay of a couple seconds is expected there's even a signal that we look for but we're not good enough yet later yet and that is once they merge together then we would like to understand the nuclear physics not of just the collapse itself but of a neutron star itself what is the what we call the equation of state of a neutron star and there's various calculations probably not very good but enough for us to see that we possibly could in the future to detect signals from the actual nuclear physics that happens when this object is under extreme compact conditions so you're just seeing the first element of that which is as they come together you're seeing where they're close enough and to give some nuclear physics and emit high energy gamma rays which is what was seen in the Fermi satellite thanks for that question thank you two questions if I may first you showed the map the areas that Fermi detected the signal and Lyko detected the signal there were two areas in Lyko one contiguous area, why? okay let me explain so if you triangulate and try to tell where something comes from if you're sailing or doing anything with two detectors all you can tell is a ring on the sky so if we just look with two detectors and no other information what we see is a ring what you're seeing is a piece of a ring on this two pieces of a ring on the sky so why do we have two pieces and not the entire ring which is what you would get with two detectors without the Italian detector it's because Lyko itself has an antenna pattern that's not spherical it's a little bit like a peanut if you're perpendicular to it it's the biggest signal if you're parallel to it and actually go down the axis of one of them it has a little indention so as we go look at the two detectors they're 16 degrees apart around the earth so we're using the two antennas a little bit differently and by comparing the strength of the signal in one compared to the other and not just the time in one compared to the time in the other we can resolve part of this ring and so you're seeing the leftover two parts which are the we couldn't resolve and adding the third detector resolves that ambiguity and also gives a much better element the third one being the Italian detector okay and the second question in like three to six years from now looking to the future is there an area of research in physics or several areas of research in physics that would be more important than other areas to be working on gravitational waves well I can tell you what our obstacles are that are important for somebody to work on both theoretically and experimentally but often what's most important to look at is what you don't know which is what we're gonna discover next and so let me give you three examples one being I don't know what the answer is so the first one is what do we really have to work on that takes innovation, creativity, a lot of hard work some money and so forth that will improve the detectors and that's really the materials that we use for the mirrors and the coatings in the mirrors and trying to understand that that's a science that material science is not kind of a first principle science and so you do it all by trial and error it's quite unsatisfying but we are limited by the materials we're limited by the material themselves and then finding a matching material for the reflecting coating that we put on the front that can't have different coefficients of expansion and stuff like that so that's the experimental biggest kind of hurdle that we should be able to make progress on and it's a lot of hard work and it's impossible to just do it theoretically or phenomenologically because it just isn't the way material science does so that's a direct one that way something more theoretical we are not able yet to calculate using numerical relativity very well the details of the spin of the two objects coming together so the spin of the two matters and it affects things or if we have two binary systems coming together and they're very different in mass a very light one and a very heavy one say a neutron star in a black hole a numerical relativity doesn't work very well so we have to develop our ability to calculate it on a computer the waveforms for very different masses the waveform says they're affected by spin or procession and we need that if we want to really understand more than we saw black holes and they're black holes but if we want to understand what the source was of the black holes then we have to distinguish the different ideas and so if the black holes were primordial the spins will be random with respect to each other while if they were made somehow in a system later they're likely to be correlated we can't do that yet because we just really aren't able to measure this do the calculations or measure the spins the last one which I say which in my mind is the most interesting of to answer your question three ways is that I've always felt the most exciting thing to come out of this is gonna be what we don't expect and that is that so far everything we look at I tell you some history from electromagnetism when we look for it and but now we're looking at the sky in a completely different way only 4% of the sky gives luminous is luminous matter there's bound to be sources of gravitation gravitational waves that are unexpected in some sense the very first black holes were unexpected in the fact that they were so heavy so how do we look with this instrument at the sky for gravitational waves from something where I don't bias myself too much what the science is and there's different approaches we try to do it and we're amateurs at it I think because we don't know quite how to do it you want to not model it so we do it one and a half ways so far and I think the second half is gonna be better but the first way we do it is to try to look for a signal that has a shape that we haven't biased by the signals very much and we've done that by using mathematical technique of wavelets which is kind of a mathematical technique instead of physics so we make a form but even doing that there's some you're making some assumptions about what happens is a function of frequency and so forth so that's the scheme we use now to make what we call an unbiased search and I consider it unsatisfactory really maybe we'll find something but it's not truly unbiased a better way I believe is the fact that we're collecting a huge amount of data and there's new techniques that aren't used for this kind of business in machine learning so using AI and machine learning to look at the data that we have and isolate and find things that are surprising or different or don't match anything else is a potential way to do it it's difficult because machine learning is great for what people use machine learning for but it's difficult for most physics problems because it's difficult to incorporate statistics and machine learning together so for example at CERN when they look at the Higgs boson they could get better signal if you use machine learning but you can't tell how many sigma it is and we have the same problem kind of if we're looking for some signal in the sky but we have no way to kind of include statistics how significant it is it becomes hard so but I think the tool is a form of machine learning but for physics problems I think we have to learn how to attach some significance to what you see and not just the machine learning itself which is the way it's generally used for most applications so a long-winded answer to your question there's gone a lot of research about how to improve these talk a little louder yes sorry so a lot of research has gone into building projects in order to improve the detectors do you know of any projects that have or are planning on researching more about the characteristics of gravitational waves? do I say the last sentence again do I know any projects do you know about any projects or planning of any projects that have gone into researching more about the characteristics of the gravitational waves themselves? I think what's being asked is that we're trying kind of blindly to make things more sensitive not being guided by what the characteristics are I maybe did that by the way I presented things what we're doing to look at a next generation detector involves now a worldwide group of pretty high-level, mostly theorists that are trying to look at the potentially attainable science goals and analyze what basically that what it takes to do those so that we can prioritize what matters for example I can build a detector that's much better at high frequency or I can build a detector go underground and build a detector that's much better at low frequency what we need is strong priorities and the scientific guidance if you want or scientific guessing at which to do we can't just try to make everything better it is too expensive and too dumb to do it so we do have a very active and strong worldwide group that are working together to try to establish what we call the science priorities for the next generation detector which I think is along the lines that you're talking about and then we want to use those to set the requirements for what a detector should look like rather than just looking at a detector and telling you which is what I did today that I know how to make this better or that better or this better that's very unsatisfying so what's the point in detecting gravitational waves and what could they be used for in the future? I hate these questions so I'll give you a lecture instead I'm gonna talk around it a little bit because I think the right answer is not to ask try to gravitationally, I have no idea that it can be used for anything some of the technologies that we've developed for example how to make a very stable table with this active feedback can be very useful because we know how to make a table much more stable than the ones who make microelectronics but I hate those arguments for doing basic science so I think the reason we do fundamental science like this is curiosity, it's what humans are good at and what makes us special and we want to understand nature, we want to understand why we're here, we want to understand how things work and so forth and so on. When we do that, we're lucky compared to say artists or musicians who make great music but then it's hard for it to be useful we have the sin and the benefit that sometimes when we make breakthroughs fundamentally they do have applications but you can't ask it for every project that's being done I'd say on the average they easily pay for themselves so I'll give you two examples that were close to me one was while I was in Berkeley as a student an experiment proved a concept that was a concept of Einstein's called stimulated emission that won a Nobel Prize and nobody knew it had any use at all about 10 years, at least 10 years later people discovered that stimulated emission was the key to making focused light beams and it's now a $20 billion industry which is lasers no, he wouldn't have ever answered you when they discovered stimulated emission that it would be useful for a huge industry like lasers a second example, these are just the ones that have been close to me in my own experience the second example I worked for a while at doing research at Cornell on the Cornell Synchrotron but in one of the labs at Cornell there was a physicist who developed who did for the first time proved a concept in nuclear physics much like the concept of stimulated emission of Einstein's called nuclear magnetic resonance and he won a Nobel Prize and nobody knew that had any value at all and it's the best imaging device we have now they've erased the name nuclear because nobody wants that if they're getting medically treated but it's the magnetic resonance imaging MRI so I think fundamental science I hate to sell it that way that's why I don't like to answer the question but I think on the average instead of project by project fundamental science has direct applications like the two that I gave you they just happen to be two that I saw with my own eyes and the advances in technology but if you ask every time we're looking for advances in science to also give us advances that'll affect humans in other ways, it's asking too much so that's my answer well there is actually a third example when Faraday was asked what his electrical induction was good for he said what's a new baby good for thank you for your fantastic here I'm here little out on I want to thank you for your fantastic journey through space and physics and whatever stories you've told I, my biological father was Hans Kaiser and he spoke a lot with Paul Clay together about harmonic proportions and it goes back to Kepler and the Egyptians and the Greeks did you ever encounter something like harmonic proportions in your research, in your phenomena? I haven't actually sorry but I haven't I have a question about the interferometer in space how does it cope with flying of objects flying by or even hitting it or first of all does this even happen? Yeah, they measure, of course anything that hits it and destroys it is a problem but satellites get hit by all kinds of things and but those are transient phenomena what they're measuring in space compared to what we do which is over seconds is effects that take times as I said in minutes and hours and most of the effects that you're talking about are going to be short compared to that and as long as they don't destroy things they're not really the background they have that affects them it would be for us because we look at very short transient signals but in space they're looking for things that develop over a longer period of time Okay, if there's no longer any questions we come to a One more, please One more somewhere Like this? Where? Can you hear me? Yeah, okay, thank you I'd like to thank you very much for your lecture it's an honor to have you here and I'm sorry for my silly question but I'm very curious is there a point to point a detector to the center of our galaxy and just our spiral type of galaxies Okay, I think if I understood the question could we try to look for something from the center of our galaxy Obviously the center of our galaxy is of interest because the center of many galaxies we don't know if all but many galaxies now have huge black holes I've been talking about black holes We don't point we do see the center of the galaxy naturally we basically cover space so we're fortunate in that way Most of the phenomena that we anticipate from the center of the galaxy however, because it's if there's a black hole at the center or whatever happens happens on slower time scales than what we look at so it may be a more important question for the space experiments than it is for our experiment We're again in this funny regime where we're looking for things that really happen very, very quickly and that makes it possible for us to do things but also makes us blind to a lot of other things that take a long time to happen Okay, thank you Professor Wiese wants to say a few words Yes, I would like to thank several people first and foremost you so it was really great to hear your lectures it was very informative but I think also very inspiring for the young people I guess in particular I think we all can be impressed that it's possible to set high goals and if you have good ideas and work hard for a long time don't give up you can be tremendously successful and so I think you have conveyed that extremely well Thank you Thank you very much for that You told us that you were at the Paul Clees Centre you have visited the Einstein House so here's a small gift it has something more about these two people and so I think we can all give you a great hand for this for the moment Thank you Then there's a few other people I would like to thank and the first person I'd like to thank is Louis Tunstall who was a member of our institute one and a half years ago he is no longer at our institute but still in Berlin in the audience today actually one and a half years ago he told me that he heard a talk by Barry Barisch in the States and that's how I got the idea to invite you Then there are people from our institute for Theoretical Physics Joao Barros, Stefan Kasper, Esther Vierchter and Manus Hornung have helped a lot to make all this happen in our communications department there are Lea Mundwiler and Ivo Schmucki who have done tremendous work to make all this possible Then there is the house deans, Daniel Treuler and his team also the people who take the videos which will then be made available as podcasts Kuno Sorge and Patrick Pellegrini have done a great job and last but not least I would like to thank my fellow interdisciplinary committee members Christiane Treta, Markus Steppanyans and Hans Rudolf Ott also those should deserve some applause I think and then finally I give the microphone to Hans Rudolf Ott to say a few last words Thank you very much Yes this brings us to the end of this year's series of Einstein lectures I must say I'm a bit disappointed that it's already over One could listen to you for quite a while but what is certain is that you are marching into a bright future as you showed us today and although many things are uncertain the certainty is if you have something to come it's already on the way to us you just have to see it and that's somehow comforting idea that whatever happens their things are coming and we just have to be clever enough to see them So thanks again and all of you come back in a year we have yet another series in next year which is then devoted to mathematics and to close it now again one big hand for Barry Barish