Ch 21: The Earth, Sky, and Moon
About This Chapter
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. |
1. Measuring Objects in the Sky: Angular Size & Distance
Objects are measured in the sky using things like angular size and distance. Explore the celestial sphere, angles, degrees, angular distance, and size, and learn a neat trick for measuring objects in the sky.
2. Important Points on the Celestial Sphere
The imaginary celestial sphere surrounding Earth is a reference tool that allows for the locations of objects in the sky to be located. Learn about the important points on the celestial sphere, including the horizon, zenith, nadir, equator, the North and South poles, and the meridian.
3. The Cycle of the Seasons in Astronomy
Explore astronomy's cycle of the seasons to understand Earth's seasons. Examine the ecliptic and celestial equator, the vernal equinox and summer solstice, the autumnal equinox and summer solstice, and perihelion and aphelion.
4. Geography of the Four Seasons
The geography of the four seasons is affected by the earth's rotation. Learn about the differences in seasons as affected by the earth's axis and rotation, and examine the earth's solstice between hemispheres.
5. The Horizon Coordinate System
The horizon system is used to find objects in the sky and determine their positioning. Learn more about the horizon coordinate system, the celestial horizon, altitudes and azimuth, and more on limitations.
6. The Equatorial Coordinate System
The equatorial coordinate system is a method of identifying sections of the sky using declination (angle from equator) and right ascension (angle from vernal equinox). Learn the use of this system compared to longitude and latitude on the earth's surface.
7. What is Precession?
The change in direction of Earth's axis of rotation is known as precession and it can affect the state of the planet. Learn more on recognizing the work of Hipparchus, compare revolution and rotation, and discuss the process and consequences of precession.
8. Lunar Eclipse: Definition & Types
A lunar eclipse occurs when the moon darkens as it moves into the Earth's shadow and the two align with the sun. Explore the definition and types of lunar eclipses, such as partial and total lunar eclipse, and understand the significance of Earth's umbra and penumbra.
9. What Is a Solar Eclipse?
A solar eclipse occurs when the moon is between the Sun and the Earth, blocking the sunlight and casting a shadow on Earth. Learn how a solar eclipse is possible, explore partial and total solar eclipses, and discover the effects of a solar eclipse.
10. Annular Eclipse: The Changing Size of the Moon
The annular eclipse is a type of solar eclipse that involves the visibility of the sun's photosphere as a bright ring around the moon. Explore a comparison of sun and moon size, the changing size of the moon, types of solar eclipses, and why annular eclipses occur.
11. How Can We Predict An Eclipse?
Thanks to consistent lunar and solar cycles, ancient and modern astronomers have been able to predict eclipses. Learn about lunar and solar orbits, explore how we can predict an eclipse, and discover the Saros cycle.
12. Why the Sun Changes Color
The sun changes color based on our perception and the position of the sun at a given time. Explore the changing colors of the sun, wavelengths of light, and how they determine color, prisms, and the setting sun.
13. Magnetosphere: Definition & Facts
The magnetosphere is the furthest outside part of the earth's atmosphere. Explore the definition and facts about the magnetosphere and learn about the Van Allen belts, magnetopause, magnetotail, bow shock, and the aurorae.
14. How Gravity, the Moon & the Sun Influence Tides
Earth is connected through it's gravitational pull and chemical reactions from the moon and sun, which also influences the oceans. Learn more about these elements and how gravity also affects tides.
15. Tidal Friction: Effects on Earth & the Moon
The moon has a major effect on the tides of the seas on Earth because of tidal bulges that create tidal friction. Learn more about tidal friction, how the moon slows down the Earth, and the Earth's effects on lunar tides.
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Other Chapters
Other chapters within the Basics of Astronomy course
- Celestial Navigation & Timekeeping
- Characteristics of Our Solar System's Planets
- Earth's Spheres and Astronomy
- Galaxies: Properties & Characteristics
- How Scientists Think and Work
- Influences on Climate
- Life in the Universe
- Light in Astronomy
- Matter in Astronomy
- Measurement of Star Qualities
- Momentum, Energy, Pressure, Temperature & Gas
- Newton's Laws in Astronomy
- Relativity in Time and Space
- Rotational Motion in Physics
- Small Celestial Bodies & Satellites in Our Solar System
- Star Death and Stellar Remnants
- Star Types and Significance
- Telescopes
- The Atmosphere on Earth and Other Planets
- The Birth and Life of Stars
- The History of Astronomy
- The Milky Way Galaxy
- The Moon: Formation & Phases
- The Orbits of Celestial Bodies
- The Solar System: Layout, Formation & Dating
- The Sun's Structure & Components
- The Universe: Key Concepts & Theories