Welcome to this, our first lesson, where we're going to explore what is arguably the biggest question of them all. How did we get here? How did the universe get started? Why is the universe here at all? Yes, questions don't get much bigger than that one. We're going to start off in this very first lesson, talking about the evidence that shows that space is expanding, getting bigger, which sounds pretty ridiculous. However, that's not an unsolved mystery. We're actually pretty sure that space is expanding. That's not quite 100% sure, but certainly 95% sure. But then the real mystery will come on to the lesson afterwards, which is, okay, so let's say space is expanding. Where is it expanding from? Was there some sort of big bang at the beginning? Had if so, where did the big bang come from? You who pressed the big red button lock do not press. So I want us to step back to 1915, to the beginnings of what we call cosmology, the study of the universe. In 1915, when astronomers looked with their telescopes up to the sky, they saw stars everywhere, and they knew these stars were like our sun. But they didn't understand is why the stars shown. What was the energy source that powered our sun? That was a mystery. But it wasn't the only mystery. One of the mysteries were these things known as nebulae, little fuzzy blobs that were scattered across the sky. Some were red, some were blue, some were very big, some were very small, complete mystery. And the person who tackled this mystery was someone everyone should know, Vesto Melvin Slyther. I'm particularly fond of Mr. Slyther because his family gave me a scholarship to study at the University of Arizona. And I'm sad to say I had no idea who he was when I received the scholarship. He is one of the founders or the founder of observational cosmology, the thing that I do. And what Slyther did is instead of looking at the canals of Mars, which was really what his job was, he observed these nebulae for the first time. Now to understand his observations, we're going to need to know two things. One is how we measure distances in astronomy, and the other is the concept of spectra. So I guess we have to explain those two things before we get going. So Brian, why don't you take the next couple of videos to explain how you measure distances of things in space, after all it's what you spend most of your life doing? Okay, that sounds good to me, and I guess that leaves spectra to you, Paul. Which I guess is what I spend a lot of my life doing. Okay, so the next few videos will explain spectra and how we measure distances, and then we'll come back to the story of Vesto Slyther and the origins of the universe. Thanks.