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0:18
Good morning. Let me say with a few words of appreciation of the invitation, which was issued by the Bulgarian friends in order to come to the country and to give several talks on the problems, that I'm dealing with. This is a great challenge to teach the topics which I myself have been learning throughout my whole career. Basically, these are attempts to understand the world, where we live goes back millennia, at least more than couple millennia, where even ancient Greeks
1:21
tried to understand our environment. This understanding was very much confined. Mostly, by the near Space around our Planet Earth, which was for millennia considered being the centre of the Universe. Amazingly we just advanced the science only during the last centuries. The most important breakthrough happened last century, when we began to understand not only how vast the Universe is, but also its beauty. Fantastic mechanism and energy sources, operating in the Universe. This
2:27
tremendously broaden up our horizons. I am suddenly unable to tell you the whole stories in detail. It would take many, many hours, possibly even days. I'd try to focus on the most important issues - on the contemporary understanding of our Space environment at large. Not only in vicinity, our Planet Earth, where we live and which belong to the quite confined area in the vast Space - Solar system The Solar system it's just a tiny dot in the boundless, basically boundless Universe. And I try
3:30
to get you acquainted with the most important ideas; our modern understanding of this Space environment. So, the lecture's called "Cosmology: Origin and Fate of the Universe" This is the main outline. I'll try to pose the most important scientific questions and these scientific questions basically they combine not only just natural science, but also philosophical aspects - just our attempt to answer the question how we came to this world and what is our future.
4:20
I'll try to give you the principal ideas about our view of the Universe and also just the progressively growing sizes of different objects in the Universe - Galaxies, Supergalaxies and so on. We'll adress the most possibly intriguing question, a very intimate, I'd say question about the world's origin. We can't answer this question for sure, but we can even right now, because of the great advances of Space tecnology, we already just got, possibly, the crucial transfer from the
5:17
pure speculation to the experimental basis and conformation of our original hypothesis. Some of them were rejected, some became just very much supported by the absolutely fantastic new findings, delivered, returned back by space vehicles. This is rooted in the historical cosmological models. These models completely just enriched and became even, possibly, more enigmatic, because of the discoveries of several so great entities, like dark matter and dark energy. We discuss our
6:26
Micro-world, based on our understanding of the Macro-world, the world of elementary particles. This is an important synergy in order to advance this science Cosmology. This involves several models and I will touch upon some of these basic ideas. This just allow us to come to our contemporary understanding of the modern Cosmology and basically the ultimate fate of the Universe. This includes so absolutely, from the first sight of view fantastic entities, like our new understanding of
7:32
our Universe as a part of Multiverse and even some ideas how to travel and how it's possible theoretically to penetrate from one to the other. Here, in the slide I'm quoting from the great scientist of last century - A. Einstain. He said: "The most incomprehensible fact about nature is that it's comprehensible". Being involved in the field, I many times was so much impressed and amazed that the mankind with their to think could penetrate so deep in the structure of matter and our world. In this
8:42
slide, I'll explain the main scientific goals of Astrophysics: to answer the 3 fundamental questions. First, "Where are we?"- It means structure of the Universe, and our location in Space. As I already said, this is very, very small, just a grain in the vast Space. Second question: "Where did we come from?" This is origin of the Universe and its elements - stars, galaxies and even more complex structures. And the third: "Where are we going?" This is evolution and ultimate fate
9:51
of the Universe as we see it right now. So, let's adress the first of these 3 questions: "Where are we? Structure of the Universe as a remnant of its origin, as we understand it. And our location in Space. " Let's start with some most important understanding about distances in Space. It's completely different from our everyday understanding, our everyday dealing with some kind of distances. We discuss, for example, how far is one seat from other, but that's absolutely negligible in terms of
10:37
the distances in the Universe. In Astrophysics distances are measured in light years (ly). This is enormous distance. It's 10 trillion km. But astrophysicists usually measure in more convenient, by some reason, I don't dig much in this, by the so-called parsec (ps). This is 3.26 ly. To us, more familiar, much lower scale, this is astronomical unit (AU). Astronomical unit is a distance of our Earth from the Sun. This is also very, very great distance - 158 million km. But in terms of
11:35
the AU take light years, parsec, it's only 8 light minutes. In other words, if you just observe a flare on the surface of the Sun, it means, that this happened 8 min. earlier. Neptune, the outer planet of the Solar System is located at 30 AU. Say Mars is only 1.5 AU. Jupiter only 5 AU. But Neptune, the distance to it, is great - it's 4.5 billion km And light takes something like about 4 hours to reach it. Our Solar system in this scale is quite large, but again negligible
12:29
in the scale of the Universe. This is distance usually measured from the Sun to the periphery of the Solar system and this is located at something like 100 000 AU. This is 1.5 ly, 0.5 pc. The nearest live star Alpha Centauri is located at 4.5 ly. Interesting, people'd use just available technology. I mean, liquid or solid fuel engines, we'll take something like 100 years in order to fly from Earth to Alpha Centauri. These scales - ly, pc, are very small in order just to measure
13:22
distances in the Universe. So astronomers usually use kpc, Mpc and even Gpc. Stars are located in several associations of some disk-shape in our galaxy - Milky way. Galaxies are the building blocks of the Universe. Stars are instituted in galaxies, in absolutely not uniform structure. The maximum population of star clustering is at the galaxy center. There are in our galaxy - Milky way, is about 200 billion stars. It's stretched for 100 000 ly or 30 Kpc. The center of our galaxy - this comprises
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at least several billion of the Sun light stars. This is associated with the great, possibly you've heart this, with the Great Black hole. How do we view our galaxy? We are located near the edge of our galaxy and it's impossible to observe it in face. We cannot observe, located in such position, we can observe it only edge-on. This is the view of our galaxy, when observed edge-on in the visible wave lengths. But the great breakthrough in the Astronomy, it's just an opportunity to observe
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stars, galaxies, other structures, not being shrouded by the Earth's atmosphere, when we use optical instruments on the Ground. This gave us absolutely new chances to observe the Universe in the whole wavelengths, in the whole range of the electromagnetic radiation - from the shortest, γ lengths to the radiowaves. This is how we observed it in the Near-Infrared and this is even most possibly attractive and amazing view in the Far-Infrared, thermal radiation. This is our galaxy
16:11
as we observe it. The blue color is dust in the Plane of our galaxy. And it means when you just observe the sight of the dust, you immediately deduce that our Solar system is steered toward or just relative to the Plane of galaxy, of something like 60 degrees. What is our place in the galaxy? This is a very interesting question. I show you this picure and you could immediately adress me back with a question: "You just said that
17:00
it was impossible to observe our galaxy in face and you just showed us such a picture." Well, you're completely right. This is not our Milky way, This is Andromeda galaxy, which is very similiar to our Milky way. So, I displayed it, just for comparison. We're located at about 2/3 distance from the Center. The center of our galaxy, as I said, associated with enormous black hole. This is our location. So, in size our Solar system is only 1/10000 % of the Milky way size.
17:42
Absolutely negligible, even at the scale of only our galaxies. I'll show you in a minute that our galaxy is only a member of absolutely greater scale of the whole Universe. This is Solar Neighborhood within 500 ly. Mostly our field, our environment around our Sun is filled with low-density molecular gases. This belong to one of the spiral arm of our galaxy. I just want to mention that our Sun is moved around the center of the galaxu. This is shown at the direction of its movement.
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We called it Direction toward Apex. Now we're coming to extremely interesting and challenging understanding of our structure, the structure of the galaxy and the whole Universe. Galaxy forms clusters of progressively growing size. These range from pairs to chain clusters. Our local of galaxy clusters, I mean, where Milky way belongs to, contains about 20 galaxies. Some clusters contain more than 1000 galaxies. Clusters are something like 3 Mpc in size. And it means that is 100 times more
19:37
than our Milky way galaxy. 100 times larger. This is just an example of one such cluster - the so-called X-Ray 44 located at about 60 million ly in Leo constellation. This is another very large cluster. We called it Virgo cluster of galaxies. Amazingly, the clusters form even much larger structures, called Superclusters of galaxies. There could be more than 100 clusters in 1 supercluster. We, with our Milky way, are just a member of one such supercluster. Size of superclusters,
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by fact 20 more compared to the size of the cluster of galaxies. It means its size could be something like 300 million ly or about 100 Mpc. This is an example of the size of the cluster, like we observe it in the radio wave lengths. This is one of the Near-by clusters of the galaxies around our Milky way. Here we are with our Solar System and Earth. This is quite familiar clusters and super-clusters around us, just not on the scale. This is 450 mpc.
21:30
For example, constellation cluster Leo is located at something like about 100-150 Mpc. Gemini is a bit closer. Perseus even closer. But even more familiar Ursa Major is located even farther. This is Ursa II, Hercules, Corona Borealis and some others. We got absolutely fantastic chance only during recent decades to penetrate with our optical instruments very deep in the Universe. The most possibly advanced in terms of the technology available, was the launch of the Hubble space telescope.
22:24
It broadened up tremendously our horizons and it allowed us to look at the Universe and the different structures in it basically in close-up. This is an image of the Universe, that's an image, filled up with structures, which look like stars we observe at the night, but these are not stars - these are galaxies and cluster of galaxies. Among the structures, we have so called quasars, or quasi-stars associations. These are the sources of enormous energy release.
23:07
Quasars are associated with quite old galaxies. But which contained absolutely enormous amount of stars within their center. This, just observing of the matter falling down these associations, clusters, just give raise to the enormous energy release. This is one example of that observable Universe; how we view it mostly from space telescopes. This is ... the size of the observable Universe is about 30 times more than distance between superclusters. So, it's very simple arithmetics
23:59
getting in and you just immediately deduce the whole size of all our Universe. It's more than 10 billion ly. or 4 Gpc. I'll give you more accurate figures in few minutes. This is a part of the Universe like we observe it, which contains more than 1 million galaxies. Possibly, one of the most impressive or even more important discoveries during the late decade was the Large-Scale Structure of our Universe. This is structure, which just immediately gives you an idea, that the Galaxies,
24:44
clusters of galaxies and superclusters are distributed within the Universe not in a uniform way or a sort of a chaotic shape. It turned out that they formed quite well organized structure. You could observe it like it's some kind of walls and a sort of empty place between them. This came to understanding of the Larger Structure of our Universe, composed of the so-called walls and voids. In Astronomy these structures are referred to Cosmic Web. It's really quite well
25:44
organized web of superclusters of galaxies. As I'll show you a bit later, they are associated with the remnants of our Universe origin. Very impressive fact. Really amazing.
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