About Lesson 1

Most of us do not notice the daily and yearly changes in the sky because, frankly, we no longer have to bother! Clocks and watches have been around so long that they hardly seem to be advanced technology. Anyone can look at a calendar to tell you what the date is, and, if we are lost on an unfamiliar road, most phones have GPS functions that can help us find our way home. Even though calendars, clocks, and navigational tools have insulated us from the need to understand the motions of the sky, most of us do appreciate that our system of time and our location on the surface of the Earth can be tied directly to observations of the sky.

In this lesson, we will study the observable changes in the positions of objects in the sky and show how these data allow us to understand the relative positions and motions of the Sun, Moon, Earth, and the stars. My hope is that from this point forward, whenever you look at the sky you'll be aware of what it can tell you about time, date, and your location.

 

What will we learn in Lesson 1?

By the end of Lesson 1, you should be able to:

• identify the objects visible in the night sky to the unaided eye;

• describe the three dimensional geometry of the Earth / Moon / Sun system;

• describe the various motions in the sky that result from Earth’s rotation and orbit;

• explain the reason that the Earth experiences seasons;

• describe the process and appearance of eclipses and the phases of the Moon.