 Greetings and welcome to the Introduction to Astronomy. In this video, we are going to continue our study of astronomy of other cultures and will begin our look at the astronomy of the Babylonians and how they developed some very early astronomy and how that ties into what we know today. So let's go ahead and do a quick overview of what we have here. First of all, where is the Babylonia? It's actually part of modern-day Iraq, and you can see it pictured on the map of the Middle East here. The Babylonian region was about in here a little ways across the Arabian Peninsula from Egypt. So we have Egypt over here, which we will talk about in a future set of lectures. So that just gives us kind of a base as to where we're looking at here. Now, what kind of contributions did they give? Well, again, I'll go over some of these in more detail in future lectures. But one thing they have that really ties in today is the sex-adjustable numbering system. Now, this is very different than our base-10 system, and any numbering system is based on whatever base you select. We use a binary system, which is 1s and 0s, and that just has just two states. A sex-adjustable system is based on a base-60. Now, you wonder, where would you use a base-60? We're used to using base-10. Well, we use a type of this within our systems for time in terms of hours and minutes and seconds. Why are there 60 seconds in a minute and 60 minutes in an hour? Well, you can thank the Babylonians for that. It's based on their sex-adjustable system that we still use today. And we use something similar for angle measurements as well. Now, what else did they record? Well, we actually, these are some of the earlier ones where we do actually have records recording. And there are stone tablets that exist that show some of the recordings and measurements of things like eclipses and of other observations of the sky. And interestingly, even at this point, many, several thousand years ago, noted that the motions were periodic and that things would continue over and over again. And we don't mean just things like the day, but even longer time frames for other observations. So they really had a very well-developed astronomy here. They looked at planetary motion and how that worked. And one of the differences they used is that they were not set on uniform circular motion. Well, this hadn't really come up yet because this comes from the time of Aristotle, who suggested that the heavens were perfect and therefore everything in the heavens would move in the perfect shaped being a circle and at a uniform speed. Now, when Aristotle gave us this, it set our definition of how the planets orbited that lasted for over a thousand years. But the Babylonians did not have this. They actually gave us non-uniform motion, which would we would come back to in western astronomy at the time of the Renaissance. There also are some thoughts that maybe there were ideas that the universe was heliocentric. That would mean sun-centered. And one of the astronomers, Seleucus of Seleucia, supported the model of Aristarchus based on writings. Aristarchus, a Greek astronomer who early suggested that the sun, not the earth, was the center of the solar system. So there are some thoughts that they may have supported this. But again, one of the problems is with this is that we have scattered records, but we have nowhere near a complete set of records as to what the Babylonians studied or what they knew. We only have what is left to be able to be studied and to determine what they used. But they did give a great influence to the Greek astronomers later on. But many of their works, as I've said, are lost. So there are many works of the Babylonians that simply no longer exist. So let's go ahead and summarize this introduction here. And we talked about the Babylonians giving us the numbering system that we still use today for things like time and angles. They noted periodic movements of the planets through the sky. And they were not fixed on uniform circular motion, which would make predicting these motions much, much easier. So over the coming two lectures, we will look at a couple more parts of this in a little bit more detail. This just is to serve as an overview of the Babylonian astronomy. So that concludes this introduction to the Babylonian astronomy. We'll be back again next week for another study in the astronomy of other cultures. So until then, have a great day, everyone, and I will see you in class.