 Greetings and welcome to the Introduction to Astronomy. In this week's Astronomy of Other Cultures Lecture, we are going to talk about Egyptian astronomy and give a brief introduction here. And then the next few lectures, we'll look in a little bit more detail about some of these ideas and concepts that we study. So, let's go ahead and look a little bit about Egyptian astronomy. Well, we actually find stone circles in fact some of the very oldest stone circles known in existence. And these date back to the 5th millennium BC, so we're talking 7,000 years ago. And probably were calendar circles to help determine time and had possible astronomical alignments. Now, these are very difficult to find because, of course, things like stone circles don't have any directions left with them as to how they were intended to be used. So we're left to interpret based on what we see today. Of course, prominently known for Egypt are the pyramids. So, let's take a look here. Here's an image of some of those pyramids. And they do show some alignments with various astronomical objects and were likely used to help determine the calendar. So, while they were also burial places for some of the pharaohs, they could also be used for calendars because they were very closely aligned with many astronomical objects. Again, there's no directions here saying what they intended to be aligned with, but we can work backwards based on what is known about things like the pyramids and how they are aligned today. And we can determine what the sky would have looked like back at the time when the pyramids were being built to really be able to find out a little more and understand how these tie in to astronomy. And then finally, the Egyptians had a very well-developed calendar by about the third century BC. So, here we see a little bit of one of the calendar recordings that has been made. They actually did use a 365-day calendar. And it was very important to have the calendar to be able to have things recorded so that you could then determine when certain events were going to occur. One very important one was the flooding of the Nile. Why was this important? Well, when the Nile would overflow its banks, it would bring water to that region of Egypt, making it more fertile. So, they were able to tie in the Nile flooding to the very, very earliest rising of Sirius before the sun in the sky the first time it could be seen. And that allowed them to develop a very prominent calendar using astronomical events like this one. So, let's go ahead and take a look at our summary here. And we talked about ancient Egyptian astronomy and how it dates back to very early and even before to prehistoric times. We looked at the stone calendar circle, some of the earliest of these in existence and, of course, the Great Pyramids. And then, finally, we looked at the well-developed calendar that was made to you that was in use thousands of years ago. So, that concludes this lecture on the astronomy of the early Egyptians. We'll be back again next week for another topic on astronomy of other cultures. So, until then, have a great day, everyone, and I will see you in class.