Ch 21: The Earth, Sky, and Moon

About This Chapter

Watch video lessons to learn more about the Earth, the sky, and the moon. See how interrelated they are, and how that interconnectedness plays a role in observing stars, the moon, the sun, and more.

The Earth, Sky, and Moon - Chapter Summary and Learning Objectives

In this series of video lessons, the close relationship among the Earth, the sky, the sun, and the moon is explored. Gain an understanding of how brightness, motion, and color are observed, described, and measured. See how in some cases, these observed characteristics vary from actual properties. Learn more about key concepts like phases of the moon and eclipses. By the end of this chapter, you should be able to:

  • Discuss how objects in the sky are measured
  • Identify factors that affect observations of objects in the sky
  • Define terms like horizon, zenith, meridian, longitude, and latitude
  • Explain the reasons for seasons on Earth
  • Explain the phases of the moon

Video Objective
The Brightness of Stars Identify and describe the difference between subjective and objective measurements of stars' brightness.
How Stars Are Observed From Earth Explain the difference between how stars are observed from Earth and how they're actually distributed through space.
Features of the Local Sky: Horizon, Zenith & Meridian Define the terms horizon, zenith, and meridian, and discuss how they're used to talk about the observed placement of objects in the sky.
How the Sky Changes With Latitude & Longitude Define latitude and longitude, and discuss how changes in latitude and longitude affect the way stars are observed from Earth.
Measuring Objects in the Sky Explain how these objects are measured; define arcminutes and arcseconds.
Estimating the Size of Astronomical Objects Describe how the size of an object is ascertained. Explain the differences in measuring very small and very large objects.
The Four Seasons on Earth Identify seasons; explain why they exist and how they vary across Earth.
Why the Sun Changes Color Explain the changing color of the sun as it's observed rising, overhead, and setting.
Formation of the Moon: Theories Explain the theories of how the moon came to be.
Lunar Geology Describe the geology of Earth's moon.
The Atmosphere of the Moon Describe the atmosphere of Earth's moon.
What Causes the Phases of the Moon? Explain why the moon looks different over the course of a month and what causes these changes.
How the Moon Rises & Sets Identify the reasons for the moon's 'rising' and 'setting,' and explain how predictions can be made about where the moon will be at a certain time.
The Solar & Lunar Eclipse Describe two kinds of eclipses, and discuss why eclipses are important in astronomy.

15 Lessons in Chapter 21: The Earth, Sky, and Moon
Test your knowledge with a 30-question chapter practice test
Measuring Objects in the Sky: Angular Size & Distance

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.

Important Points on the Celestial Sphere

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.

The Cycle of the Seasons in Astronomy

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.

Geography of the Four 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.

The Horizon Coordinate System

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.

The Equatorial Coordinate System

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.

What is Precession?

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.

Lunar Eclipse: Definition & Types

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.

What Is a Solar 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.

Annular Eclipse: The Changing Size of the Moon

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.

How Can We Predict An Eclipse?

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.

Why the Sun Changes Color

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.

Magnetosphere: Definition & Facts

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.

How Gravity, the Moon & the Sun Influence Tides

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.

Tidal Friction: Effects on Earth & the Moon

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.

Chapter Practice Exam
Test your knowledge of this chapter with a 30 question practice chapter exam.
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Practice Final Exam
Test your knowledge of the entire course with a 50 question practice final exam.
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