 Greetings and welcome to the Introduction to Astronomy. In today's Misconception in Astronomy we are going to look at the idea that Galileo invented the telescope, and find out that that's not correct and look at who actually did invent the telescope. So let's take a look at this, and the telescope was actually invented not by Galileo, but by Hans Lippery. And it was developed the early telescopes in 1600. He actually tried to patent the idea, although that didn't go through, but he was the one, the first one to have recorded a device like a telescope to be able to magnify objects. Now Galileo, why is Galileo associated with this? Well, Galileo heard of the device, and without ever having seen it, built his own a year later. So Galileo did build a telescope, not the first one, but he did build a telescope and was often given credit for this, and he has given credit not because he invented the telescope, he did make improvements to it, but the big thing was that he was the first person to observe the sky and record and published his observations. So let's take a look at his telescope here, and these are actually reproductions of Galileo's telescopes here. And very small, you can see the size of the lens here is very tiny by comparison to modern telescopes. As we call his biggest telescopes, may have used an lens that was about an inch in size. So they were not extremely large telescopes, but they were a big improvement over the human eye. So again, why does one person get credit when other people may have used it first? Well, Galileo is given the credit because, as I said, he observed the sky, you know what other people may have looked at the sky as well, but the big key is the end here. He recorded, he wrote down what he saw, and he published those observations, and that's why he will end up getting the credit for it over others because there is a record of what he observed. What did Galileo observe? He looked at a number of objects, especially within our solar system, including the planets. And here we see some of his very early sketches of the planet Venus. And he saw that Venus went through a set of phases, that here in October of 1610, it was a very large Venus and a very large thin crescent. And through November to December to January to February, the size of the planet decreased. Now of course we know that the planet is not changing its size, it's getting farther away. And more and more of it was becoming illuminated. So it was going through phases just like our moon. Now this was important because the only way that this could happen is if Venus orbited the sun. At the time it was thought that all objects orbited Earth, and we were looking at the time shortly not that long after Copernicus suggested that perhaps planets orbited the sun, but it was certainly not fully accepted at this time. This was one of the first big pieces of proof that not Earth had to orbit the sun, but that at least some other object had to orbit the sun, which was a big step along the way of going from the idea of an Earth-centered universe into a sun-centered universe. So let's go ahead and finish up here with our summary. Let's look at what we've talked about. First of all we said that the telescope was developed in Holland in 1608, Galileo heard of this, and made his own about a year later. And his key contribution was that observing the sky and publishing his observations, which we still have today. So that concludes this lecture on Galileo and the telescope. We'll be back again next time for another misconception in astronomy. So until then, have a great day everyone, and I will see you in class.