 Greetings and welcome to the Introduction to Astronomy. In this lecture video we will take a tour of the universe and look at all sorts of scales from the very little to the very large, from the edge of the universe to the inner universe of atoms, and try to look at all of the different things that we can see and that you might study in an astronomy class. So what we'll look at is essentially we'll take a trip and the nice thing about taking a trip like this is that we can go as fast as we want. So there is no limit here, we can travel, we're not limited by the speed of light. So simple things that light only travels at a certain amount of speed and that we can only take, even if we could travel at light speed, it would take us four years to get to the nearest star and two and a half million years to get to the Andromeda galaxy. Now we can travel even greater distances in a much shorter period of time. When we start off, we'll start out on our own Earth, some things that we're actually familiar with. We'll zoom outward to the edge of the universe and then we can come back in and look at the universe of very small objects, things like atoms. So very small objects that we'll also look at in terms of talking about how energy is generated in stars, for example, is through atomic reactions that we'll need to look at. So a number of different things and what we're going to use here is we're going to use a website that kind of does this for us and lets us help zoom through this all. And what we'll do is the website is linked to here and this is by Kerry and Michael Huang and it allows us to scroll through these different sizes. So let's take a look at their website on the scale of the universe and see some of the things that we need to see for an astronomy course. So as we start, we'll see the website like this, so the scale of the universe, and we're going to want to look at this and we'll be able to scroll in and out through things as we begin this tour. So here as we start off with are some things that we are familiar with. So we have the size of a human, a beach ball, a dodo bird and some other things. Now if you're interested in learning about anything, you can actually click on each of the objects and it will pop up a little bit of information on it and give you some details. But what we're going to want to do is scroll towards the bigger objects. So we're going to scroll outward a little bit here towards things that are larger than a human and as we go out further, we see things like some very large animals, giraffes and elephants, large dinosaurs. And you can see that our human figure there is shrinking down and getting smaller and smaller. As we look, we get to the Apollo Lunar Module there, large trees, even larger dinosaurs and again our human figure is very quickly disappearing and becoming minuscule by the time we get to something like a 747 and a giant redwood tree. And if you can still see our human figure fading down to almost a point down there and we've only begun, we've only gotten some of the very smaller objects here on Earth. There we get to a football field, the Saturn V rocket, the Great Pyramids and the Eiffel Tower. We get some large man-made things, things like the Hoover Dam we see over there and we continue out even further and see larger and larger objects. We start to get out to some astronomical objects so you can learn what some of these are. This is actually one of the objects that orbits in about the same orbit as the Earth so it's actually kind of a second moon of the Earth. We see Deimos, one of the moons of Mars, Halley's Comet, very famous comet coming back every 76 years in the approximate size of things like a neutron star smaller than the state of Rhode Island. Now we're getting out to a few more objects that we know. Nixon Hydra are two of the moons of Pluto and again are smaller than many states here in the United States and smaller than for example the length of the Grand Canyon. Now we're getting out to some of the larger states, things like California. We get to start to see the asteroids, the largest asteroid, now one of the dwarf planet series is visible. Pluto and Charon and Eris, some of the objects out in the Kuiper Belt. And as we continue out further now we start to see lots of the moons in the solar system. There's our own moon, Ganymede, Callisto, Io and Europa around Jupiter. And finally we're getting to our Earth where we can see the entire Earth now. And starting to see some stars. In fact our first star appears and that is Sirius B, a white dwarf star. Only about a little bit bigger than the size of the Earth. We see some of the larger planets now, Jupiter and Saturn. And we're starting to get mixed in with the larger planets and the smaller stars are essentially the same size. So as we continue out here and kind of zip through some of this, we'll start to see some larger stars. The Sun and Alpha Centauri, two very similar stars. And then we'll start to see stars that are even bigger. If you watch our Sun slightly to the left there as it shrinks down as we start to see some of these incredibly large stars. Things like Spica and Pollux, which are extremely large stars. And then Arcturus and the Polestar, Polaris coming up there at the top. So very large stars. And you can see that our Sun has essentially disappeared by comparison to some of these very largest stars in the universe. And now let's get out to some of the very largest stars. And we have things like Antares, we're into the red super giants. So some of the very largest stars that we can possibly see. Vy Canus Majoris being the largest star. And you can compare that too up in the upper left, the distance between Neptune and the Sun. That's essentially the size of our solar system. If this star were in our solar system, it would engulf all of the planets out through Uranus. Now there actually is the Kuiper Belt. And we're going to start to see some Nebulae get to some other distances here. How far various things get away. And we come out, we'll see different Nebulae. And again, you can click on any of these. If you run this, go to the website yourself and take a look at it. You can actually look at any of these yourself. There's the Oort Cloud, kind of the outer edges of our solar system. And some various different Nebulae that you can look at and study in an astronomy class. As we continue outward, we see the Eagle Nebula, the North American Nebula, the Rosette Nebula. And a lot of these very large Nebulae, a lot of star-forming regions. Things like the Tarantula Nebula, one of the largest star-forming regions that exist. And now we're starting to get beyond the realm of star-forming regions in Nebulae and actually getting to small galaxies. So the small Magellanic Cloud and the large Magellanic Cloud, two small satellite galaxies of our Milky Way. And as they start to shrink down, we start to get to things the size of our Milky Way. And there it is in the upper left, as well as a number of other galaxies like Andromeda and others. But those are not the biggest galaxies. You see we see some other ones, the NGC 4889, a very, very large galaxy. And some others that are incredibly large galaxies. You see here that would dwarf our own galaxy. On the right is our local group. So our local group of galaxies. And we start to see some other clusters of galaxies as things cluster together as we get further out and go out to these tremendous distances. We get out to the Virgo Supercluster, great voids. We start seeing things like the voids and clusters that we see on very, very large scales. And we're talking about billions of parsecs, billions of light-years as we get out to the edge of the universe here. And we finally end up with what is the observable universe. So everything that we can see there, anything beyond that, simply is invisible. Now if we go back in quickly, now we're going to go in a little bit faster. So we kind of zoom in very fast back into where we started, back through the clusters and the galaxies, and then back into the nebulae and back to, and then into the stars we'll start to see coming in here now. Here are all of those stars coming back into something like our own sun appearing now. And as we get to the smaller stars, we'll start to see planets. And we'll get from planets into the moons and then we'll get from the moon into things actually visible here on Earth. We're down to the states and we're down to some of the larger features here on the Earth, things again like the Eiffel Tower or a Boeing 747. And we see our human figure now coming back to the foreground as we start here. Now we can also zoom inward and I'm going to go in a little bit just to look at some of the universe of the very small. Now what we want to look at are some very, very small things. And we go a lot smaller than some of the little objects that you see here that you might be aware of. Some things that require microscopes to be able to see. There you see now the thickness of paper, the width of a human hair. As we go down deeper and deeper, we get to the wavelengths of infrared light and different cells now visible. And as we continue to zoom in even closer, we'll get to the things that we're looking for. Ultraviolet wavelengths, really short wavelengths of light. And there is the DNA, the double helix DNA. And we're down to X-ray wavelengths, very, very short. We're starting to get to the size of some of the atoms that we'd look at, things like a cesium atom there on the right, carbon atom there on the left, and a water molecule in the center. As we get down further and further, we get down to two of the most important atoms in the universe, the hydrogen atom and the helium atom. They make up the vast majority of all atoms in the universe. Now we can actually go smaller than those. And we can see gamma-ray wavelengths. And then there's kind of a gap in here where we see hardly anything for quite a while. And then we get down to the actual nuclei of the atoms. These are what we see in stars. And it is the protons that fuse together to form helium nuclei that will power things like the Sun. Now as we get smaller and smaller, now we're getting down to things that we really just don't really have a good understanding of. We get down to the range of the quarks, quarks that make up the protons and the neutrons. Neutrinos, we'll get down to even smaller objects, the top quark there. And as we go smaller and smaller, we have a whole section here where there's essentially nothing as we keep going down. Each of these circles is a factor of 10 in size. So every time we go through one of these circles, you know it seems like there's almost nothing there. Until we get down to the very end here, the Planck length, the very smallest length that could be known, and you're getting to the sizes if you've heard of things like string theory or quantum foam, we're getting down to that very, very small level. So now let's zoom back out to where we started. Again there was a lot of empty stuff there. As we start to come back into the particles, the quarks, the nuclei, then we'll come into the atoms. As we see those and come back into bigger things, there's the DNA again. As we come back out towards larger and larger objects again, blood cells, different cells here visible. And getting back to everyday things that we recognize. There's a penny and our little human figure should be coming in here just in a second and there is our human figure back to where we started. So that kind of gives you a chance to zoom through and look at all of these things in the universe. And I do recommend that you go to the website and take a look and play with it yourself because as I said you can click on each of these objects and use that to get some more information on them. So I said I do recommend you go to their website. I've listed it here so you can actually get to that very easily. Go to that website and check out and really learn some more about the different things that we study in astronomy. Now so finally one of the big things that I wanted to get across here and you saw this with some of this but the universe is empty. That means there's essentially nothing in it. We saw the universe of the very small was a lot of empty space. Well so is the universe of the very large. And for example if you were to take the sun and just condense the sun down to the size of a basketball to scale the earth would be a pea and would be about a hundred feet away from the sun. So hardly even noticeable and in between the pea that is our earth and the rest of the objects and the sun would be just empty space with a couple of more peas from Mercury and Venus. To the same scale the nearest star would be a few thousand kilometers away. And what is between those essentially nothing. In those few thousand kilometers there would be essentially nothing else. If we look at what our solar neighborhood would be it would be a dozen or so basketballs that are each a thousand kilometers or more away from each other. In reality space is empty and that implies the solar system being empty being at a mostly empty space. The galaxy is mostly empty space and the space between the galaxies is mostly empty. So there is not a lot of material there in the universe. But what there is is what we would study in an astronomy class. So finally let's just summarize here what we have. Well we've looked at the range of the universe in this from some of the very largest objects to the very smallest. And really what I want you to get one thing I want you to get from this here is that the solar system the galaxy the universe are really empty. There is a lot of empty space there and the pictures that we see when you see pictures of the solar system a lot of the empty space is taken out because a true scale picture of the solar system would be very boring because there'd be nothing there. But when you put all those objects close together you give the impression that things are a lot closer together than they truly are. So that includes this lecture on the tour of the universe. And until next time have a great day everyone and I will see you in class.