Ch 4: The Earth and Sky

About This Chapter

Let us help you review facts about the Earth, sun and moon. Get information on solar and lunar eclipses and how the Earth's history can be divided into eras.

The Earth and Sky - Chapter Summary

This chapter's lessons explore ideas about how and when the Earth was formed and the characteristics of major eras in its history. Our instructors discuss the geography of the seasons and explain what the magnetosphere is. Other lessons look at eclipses and ways to predict them.

You'll refresh your knowledge of the celestial sphere and how we can measure astronomical objects. After watching these videos, you should be familiar with:

  • The history of our planet
  • The horizon and equatorial coordinate systems
  • Angular size and distance as tools of measurement
  • The cycle of the astronomical seasons
  • Solar eclipses
  • Annular eclipses
  • Precession

Our lessons average about five minutes each, and you can watch them from anywhere, on a computer or mobile device. The multiple-choice quizzes that follow each video let you assess your knowledge and gain experience answering questions in this format. Each lesson has video tags that let you return to key points without having to re-watch the entire session.

13 Lessons in Chapter 4: The Earth and Sky
Test your knowledge with a 30-question chapter practice test
Formation of the Earth: Theories

1. Formation of the Earth: Theories

In this lesson, the theory of how the planet Earth formed will be discussed. This includes looking at how it differentiated into three layers, how it formed its atmosphere, water, and land features, and how it continues to evolve today.

The History of Life on Earth: Timeline and Characteristics of Major Eras

2. The History of Life on Earth: Timeline and Characteristics of Major Eras

The Earth is over 4.6 billion years old. Ever wonder what happened during certain time periods in that large amount of time? We will look at the major eons and eras of Earth's history along with important characteristics of each.

Important Points on the Celestial Sphere

3. 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 Horizon Coordinate System

4. 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

5. 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.

Measuring Objects in the Sky: Angular Size & Distance

6. 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.

Geography of the Four Seasons

7. 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 Cycle of the Seasons in Astronomy

8. 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.

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.

What is Precession?

12. 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.

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.

Chapter Practice Exam
Test your knowledge of this chapter with a 30 question practice chapter exam.
Not Taken
Practice Final Exam
Test your knowledge of the entire course with a 50 question practice final exam.
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