 Sì, è impressionante la quantità di sogni, di visioni, di capacità d'immaginazione, di creatività e poi di concretezza che sia lei che Taka che ci hanno dimostrato stasera. È davvero un grande regalo averli qui oggi perché ci mostrano che è possibile, ok, qualsiasi sogno è possibile, ha fatto di lavorare, di riuscire a mettere insieme dei gruppi di ricerca di alto di velo, di cooperare straordinario, per me è veramente straordinario. Io devo dire, l'ultimo ospite è Werner Hoffmann, Werner Hoffmann è direttore del Max Planck Institute di Heidelberg ed è portavoce di CTA, c'era in Cove Telescope al Reiki, ha organizzato questo symposio, ha avuto anche questa splendida idea di un incontro con tutti voi, con tutti voi questa sera. Noi tutti siamo abituati a pensare a la velocità della luce nel vuoto come un limite che non si può superare e questo è certamente vero se appunto si considera la velocità della luce nel vuoto. Però quando la luce si muove attraverso un mezzo tipo l'acqua oppure l'aria, l'atmosfera può capitare che in certe circostanze alcune particelle la superino in velocità. Quando questo accade queste particelle mettono una luce. Bene è proprio da questa idea che si è partiti per pensare al Cerecove Telescope al Reiki. Questa luce è messa da particelle che si muovono a velocità superiore della luce, si chiama appunto luce effetto Cerecove, è messa per effetto Cerecove. Bene parlerà appunto Werner Hoffmann. Well, the reason we are all here is because of the CTA symposium and so maybe it's not a bad idea to tell you what the Cerecove Telescope Re is. Now what we've heard so far, we've heard about cosmic messengers, neutrinos, we've heard about gravitation waves which send ripples through space and time. But still most of what we know from the universe, we know through electromagnetic waves, through light, all the wonderful pictures which modern telescopes like the Hubble Telescope give us, pictures of distant galaxies amazingly resolved, also pictures of Nebula in our own galaxy of star forming regions, all these wonderful pictures you probably have seen somewhere in journals or in talks. And there's for example this sparkling cloud of stars towards the galactic center. However you're probably aware that these pictures of the sky which you see with your eyes in the visible light, this light encompasses a certain range of wavelengths of frequency, it goes from red on one end to blue on the other end of the spectrum, the red end has the light with the long wavelengths, the low frequency, the low energy per quantum of light, the blue end has the short wavelengths, the high frequency, the high energy. However this range in wavelengths is just a factor of two so it covers it can be compared to one octave on a piano. The light or the electromagnetic radiation we receive from space however is much more radiation from space encompasses about 70 octaves and 70 octaves that corrispondent to the sounds of a 15 meter long piano. So on this 15 meter long cosmic piano you have on the on the low pitch side the radio waves, then comes the infrared, the visible light, the ultraviolet, the x-rays and the very high pitched sounds on the right end of this cosmic piano are the gamma rays. Much of modern astrophysics has been exploring the other 69 octaves of the spectrum outside the visible and making this accessible to observation. And to illustrate to you why it's so important to be able to listen to this whole spectrum of cosmic sounds, what I've taken is I've taken a familiar piece of music and I've cut out one octave of the spectrum. One octave corresponds to the visible light which we see with our eyes. Now listen to this familiar piece of music in one octave of the spectrum. Let's hope this works. Very strange. You probably don't figure out what it is. You certainly don't enjoy it. So that's the problem because you're listening in just one octave. Now let's try to take the pin piece of music and listen to it on the only 10 octaves of the acoustic spectrum, not to mention the 70 octaves of the cosmic spectrum. And if I play you the music with the whole spectrum, you will certainly recognize what it is and you certainly enjoy it. So this just serves to illustrate how important it is to listen to the whole spectrum of cosmic sounds from the very low pitch radio waves to the very high pitched gamma rays. And gamma rays is what CTA is about and what we'll be talking about for the rest of the day. Gamma rays are the most extreme radiation. They have wavelengths, which is a small fraction of the size of an atomic nucleus. They have energies per light quantum, which is a million, million times higher that of visible light. They're incredibly energetic radiation. But gamma rays in the end, they are a form of light. They're electromagnetic radiation. But it turns out they are somewhat different. And if you wish, the reason they are different is basically all Einstein's fault. Now let me explain what I mean by this. Let's take an atom, which is sort of the elementary nucleus of matter, the elementary building block of matter. It's made of an electron which circles around a nucleus. The energy with which the system, this electron is bound, well, you take Einstein, energy is mc squared, mass times square of velocity of light. So the energy at which the system is bound is something like the mass of the electron times the velocity of light squared times some numerical factor, which I don't care about right now. But that's the relevant scale and it's just Einstein E equals mc squared. Now the important difference now comes because for all the left hand side of the spectrum, the energy of the quantum is much smaller than mc squared, the binding energy of an atom. On the right side for the gamma rays, the energy of the quantum is much, much larger typically than the binding energy of an atom. That has very important consequences. On the left hand side of a most of the spectrum, radiation is emitted by hot bodies. It's like iron glowing red at 800 degrees and yellow at 1200 degrees. It's thermal radiation, it's just hot stuff producing the light that we see. That works well except for gamma rays. Why? Well, a gamma ray has an energy which is much larger compared to the binding energy of an atom. How can an atom emit something which is much larger than its own binding energy? It would immediately blow up. So you cannot make gamma rays by thermal radiation and the only way people have come up to make gamma rays of these energies is by cosmic particle accelerators. Imagine things like our earthly particle accelerator somewhere in space, of course they will look different. They accelerate nuclei to enormous energies. This nuclei bump into something interstellar gas. They perform secondary particles and among these are these high energy gamma rays. These are particle reactions like the one which we see in our colliders here in the bubble chamber and some of these things coming out are gamma rays. So that's sort of the idea. Gamma rays show you a different universe. They don't show you the thermal universe of hot bodies. They show you a universe of odd things like cosmic particle accelerators. Now this boundary, this gap has another important consequence and the consequence is that it's hard to detect gamma rays in a sense. Why? Well, in all this range you can build lenses and mirrors that focus light. Of course Galileo's first telescope with a few lenses imaging light. Radio telescope which focus radio waves on a receiver here. Infra x-rays you can build lenses. They look a bit odd in fact in telling company is one of the pioneers of these technique. But just believe me this thing focuses x-rays and makes an image. Now gamma rays, the energy of a quantum is much larger than any energy in matter. So if that hits matter just blows up the matter. There's no way to build a mirror or a lens for gamma rays. The other thing you can do is you put a block of matter into the path of the gamma ray and having energy which is much larger than MC squared it will just make new particles. It generates a cascade of secondary particles running over typically sort of a meter of say a concrete block until all the energy is used up in secondary particles and the thing is slowly stopped. So the only way to detect gamma rays you put something in its way and makes this cascade and you're somewhat ready to detect the cascade. Ok, now these are some of the instruments, some of the telescopes which we currently detect gamma rays. You see here the band of the Milky Way. This is a time lapse movie of course. Things move much faster than they do in reality. But now you should ask yourself, what is this guy telling us? First I tell you he cannot build telescopes for gamma rays and then I show you instruments which detect gamma rays. What's happening there? Well, these things work a bit differently and let me tell you how they work. They're so-called Cherankov telescopes and what we do is we simply use the Earth's atmosphere as a block of matter. A gamma ray comes in, it generates a cascade of secondary particles and now we somehow need to detect this gamma ray track, this cascade of particles and fortunately when particles rush through the air at the speed of light they emit something called Cherankov light. It's a blue light and it's beamed forward like the headlights of a car. So you get this beam of blue light which on the Earth illuminates a circle of maybe 200, 300 meter diameter and if you place a telescope in this or if a telescope happens to sit in this light pool as we call it you can take a picture of this particle cascade. This picture may look like this and then you track this cascade back to the sky where the gamma ray came from. So you can think about it, it's like a meteor track. A gamma ray makes in the atmosphere what's a meteor track and you take a picture of that meteor track except it's very faint, you can't see it with your eyes and it's very short-lived a few billions of a second. And what one typically does since one is looking at track in the atmosphere one wants to point it back in space one needs not just one view but multiple telescopes looking at this track from different sides so that like with the human stereoscopic viewing you can reconstruct it in space. There are a number of such instruments which do that so these are big telescopes collecting the faint Cherankov light. This is our head system in Namibia the magic system on the Canary Islands and the Veritas system in the United States. Let me just highlight the magic system here a little bit because that has a very strong participation by Italian scientists and has some very spectacular results recently. Now there's one important thing you need to understand about this technique. These telescopes don't take pictures of the sky they take pictures of tracks in the atmosphere which point back to the sky. So one of these pictures of a particle cascade in the atmosphere gives us one point in the sky where this gamma ray came from. It's not yet a sky image in gamma rays to get a sky image we need to collect many of such pictures and superimposed and slowly some structure in the sky will emerge and that can actually take days or even weeks of exposure until slowly a picture of the gamma rays' sky builds up. Now this picture which you see building up is of course nothing in the real sky. This is CTA written into the sky as the future of gamma ray astronomy but that's sort of how CTA a gamma ray source would look in the sky. Now how does the real sky look like? Well it took over a decade of observations of the Milky Way to see how the Milky Way looks in gamma rays and this is of course now an extreme time lapse and you see that the entire Milky Way is lined with sources of gamma rays meaning all these are cosmic particle accelerators in our Milky Way. It's not a rare phenomenon it seems to happen everywhere this strange non-thermal universe. Now what are these things? I can tell you all the details but one type is something which you already heard of which is a supernova explosion. A supernova an exploding star sends a shock wave into space at speeds of many thousands of kilometers per second and this shock wave can accelerate particles and one wave imagining how it does that it's a little bit like an atomic nucleus being caught in this blast wave and like a surfer riding on a wave this atomic nucleus is riding the blast wave and it's gaining energy and what we see in the end of course is not the accelerated particle but the gamma ray which is made into this accelerated particle bumps into something so we don't see the surfer we see the cry the surfer lets go and it's a log or something So that's now you can ask well if cosmic explosion may gamma rays all of you of course have heard about the giant black hole discovered in ABM87 a black hole is a very violent cosmic event shouldn't that make gamma rays? Of course it does it's in fact a joint measurement of all these three instruments e il problema è che il flasco di gamma rays in questo evento sta andando a scale di giorni che è sorpresso che questo black hole ha una scale di giorni quindi come questa cosa può tornare e fare gamma rays in un giorno è uno dei grandi misteri ok quindi uno dei miei colleghi astrofisici ha detto compare questo chiaro di low energies o questo non thermal universe per la universe gamma è come comparare una piccola con una piccola star di twinkling questo è il nostro universo thermal per una piccola della scala di Vincent van Gogh che è chiusa qui è un turbulento, è una scala dinamica vedete la scala di luci dove ci sono molti metalli dove c'è la concentrazione di energia e il mio collo ha chiesto che i gamma rays mostrano l'universo ora c'è un po' di problema che è che i nostri instrumenti currenti non sono abbastanza sensativi per rivelire questa scala di van Gogh dinamica vedete le fascinate glimpsi ma non vedete la scala di luci quindi questo è il motivo che un team di scientistiche che vedete qui solo una piccola fractura hanno preso iniziato un instrumento di generazione che ci fa una piccola di questa dinamica e questa piccola sarà fatta con la scala di luci questo gruppo di scientistiche è un compasso di più di 1.400 scientistiche e d'ingegneri da 200 instituti in 31 paure la questione è come buildete un instrumento più potente per detectare i gamma rays e guardare l'universo extreme beh, vediamo questa è uno dei nostri instrumenti currenti c'è quattro telescopi simbolizzati con questi circolari e ora cosa che sta passando è che un gamma ray vada e fa un cascato in l'atmosfera illuminata un circolo di circa 200 metri sull'interno questi 4 telescopi prendono le immagini di questo gamma ray possiamo riconstruire il track in spazio e tutto è fine ora avranno il prossimo gamma ray e ovviamente avranno in qualche paura vabbè, vediamo questo è il prossimo missiato no, non una piccola piccola questo è andato questo è un telescopio singolo bisogna fare due occhi per riconstruire il track in spazio ah, questo è una bella questo è 2 telescopi non perfetto ma di solito usefulo questo è, ovviamente, messo quindi, adesso il fianco deve essere l'opera come puoi creare un bel telescopio un bel strumento semplicemente portare un po' più telescopi e ora si prende il mismo gamma ray un cattivo qui, perfetto un cattivo qui, perfetto un cattivo qui abbiamo visto un cattivo qui, fine un cattivo qui, tutto è perfetto ora c'è un piccolo problema che è, i telescopi costano dinheiro e molti telescopi costano molto money quindi bisogna economizzare un po' e il modo in cui economizziamo è per non building un tipo di telescopio ma building different types of telescopes building a few large telescopes che cover the very low energy dim gamma rays and building many small rather cheap telescopes to cover the large area and cover the high energies where gamma rays are rare and we need to detect them over large area so this is sort of an artist's view of the telescope array and let me just get this movie going you see it is in this case 100 telescopes close to 100 telescopes spread over the side you see the different telescope types which different mirror areas and you just in a second see an aerial view of the system showing at the core the low energy part then medium sized telescopes and very small telescopes at the outer edge covering a large area so thereby economizing the construction cost and still covering the full spectrum of gamma rays with a required sensitivity so and then these telescopes observe the light flashes from space symbolized here in this animation so we already have we are at the verge of starting the construction of CTA there are prototypes of all these telescopes this is a prototype of a small size telescope inaugurated on Sicily and you notice small is relative sizeable telescope there are three different designs of the prototypes on the test in France and Poland so we will build 70 of these then this is a medium sized telescope we will build 40 or plan to build 40 of these and you see this is a quite sizeable instrument and the large telescope which has a 23 meter mirror diameter of which there will be 4 on each of the sites that one was inaugurated on La Palma and Taccati was participating in this event this is the first actual CTA telescope on the northern side now what do you mean by northern side well one essential feature of CTA is we want to see the full sky because there are many phenomena which are in the south or in the north to be really sensitive if you want to cover the full sky so there will be two sites of telescope arrays one on the Canary island of La Palma in Spain one in Chile on the Aesolands in the southern hemisphere and here you see artists views of these two arrays on the north construction has started with the first telescope in the south right now there's just an empty desert and it really calls for being filled with telescopes and we'll do that over the next years so you've already heard the CTA headquarters from which the whole project is steered are here in Villania that's why we're having this symposium Federico Ferrini is the director of the observatory of the company which will build the observatory and so we're really looking very much forward to in about five years so having CTA operational and then together with neutrino observatories together with gravitational wave observatories together with new radio observatories give us new visions of the sky allowing us to look beyond borders a to explore the unknown universe and I must say I'm very curious I'm very much looking forward to all the surprises and to all the great discoveries and to the news about the universe in which we live which these instruments jointly will bring us Thanks a lot Thanks a lot