Ch 21: The Earth, Sky, and Moon

1. Measuring Objects in the Sky: Angular Size & Distance

This lesson will teach you about the celestial sphere, angular distance, angular size and diameter, arc minutes, and arc seconds. You'll also learn some neat tricks on how to use your own hands to measure these.

2. Important Points on the Celestial Sphere

This lesson will discuss some important points and lines located on the celestial sphere, including the zenith, nadir, celestial equator, meridian, and north and south celestial poles.

3. The Cycle of the Seasons in Astronomy

This lesson will explain to you why the Earth has different seasons, what the equinoxes and solstices are, their names, and if the distance the Earth is from the Sun influences the seasons.

4. Geography of the Four Seasons

This lesson will explain how the earth's axis and rotation affect seasons. In doing this, it will also highlight the concept of the summer and winter solstices, as well as how seasons vary around the globe.

5. The Horizon Coordinate System

This lesson will describe a celestial coordinate system known as the horizon system or altazimuth system, as well as important terms such as altitude, azimuth, zenith, and angular distance.

6. The Equatorial Coordinate System

This lesson will teach you about the fundamentals of the equatorial system, including declination, right ascension, the vernal equinox, angular diameter, and celestial equator.

7. What is Precession?

You've probably heard of the term precession. But what is this really? And what significance does it have to our night sky? This lesson will explain what it is and what it causes.

8. Lunar Eclipse: Definition & Types

This lesson will teach you about the lunar eclipse. You'll learn the difference between a penumbral, partial, and total lunar eclipse, and see what totality means with respect to a total lunar eclipse.

9. What Is a Solar Eclipse?

This lesson will describe what a solar eclipse is, why it's possible, when a partial or a total one will occur, and what cool effects occur during one.

10. Annular Eclipse: The Changing Size of the Moon

This lesson will explain what an annular eclipse is and why it occurs with respect to the sizes of the Moon, the Sun, and the position of the Moon during its orbit.

11. How Can We Predict An Eclipse?

This lesson will tell you when lunar and solar eclipses are possible, what nodes have to do with it, how long eclipse seasons last, and what the Saros cycle is.

12. Why the Sun Changes Color

The Sun does not change its true color. However, the way we observe the Sun on Earth makes it appear that the sun changes color. Why this is so is outlined in this lesson.

13. Magnetosphere: Definition & Facts

In this lesson, you'll learn about how the northern lights are formed thanks to the magnetosphere and solar wind. Of course, you'll learn a lot more, including what the Van Allen belts, magnetopause, and magnetotail are.

14. How Gravity, the Moon & the Sun Influence Tides

This lesson will define tides, the tidal force, neap tide, and spring tide. It will also talk about how the sun, moon, and Earth interact to produce tidal bulges.

15. Tidal Friction: Effects on Earth & the Moon

This lesson will go over the concept of tidal friction, why it occurs, and how all of that has affected Earth's spin and day length, as well as the moon's rotation and distance from Earth.