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Chapter 2

Chapter 2: Patterns in the Sky--Motions of Earth

Study Plan

In this chapter we begin our journey in earnest, starting out as our ancestors did when they first gazed at the Sun, Moon, and stars, and tried to understand what they saw. With the benefit of knowledge hard-won over the centuries, we will look at patterns present both in the sky and on Earth, and then look beyond appearances to the underlying motions that cause those patterns. Here we will discover

  • How the stars appear to move through the sky as Earth rotates on its axis, and how those motions differ when seen from different latitudes on Earth.
  • How Earth's motion around the Sun and the tilt of Earth's axis relative to the plane of its orbit combine to determine which stars we see at night and the seasons we feel through the year.
  • The motion of the Moon in its orbit about Earth, and how that motion, together with the motion of Earth and the Moon around the Sun, shapes the phases of the Moon and the spectacle of eclipses.

Organize

  • Read Chapter 2 in your textbook or ebook.
  • Take the Diagnostic Quiz to assess your understanding of the basic concepts and identify gaps in your understanding of the assigned reading.

Learn

  • Access the Animations given for this chapter. These brief lessons enhance your understanding of core concepts.
  • Access the applets for this chapter.  Be sure to try different parameters with the applets to make sure you understand the concepts.
    • Zodiac Simulator - Change the date to view the sky during different months of the year.
    • Sun’s Rays Simulator - Note how the direct rays of the Sun it different parts of the Earth as the year progresses.
    • Path of the Sun Demonstrator - Change the observer’s latitude to near 90oN and near 90oS and compare to latitude settings near the equator.  Note how the Sun’s path in the sky appears in these different cases.…
    • Lunar Phase Simulator - Be sure to note how the angle between the Sun and the Moon change during the Moon’s orbit. 
    • Moon Phases and the Horizon Diagram - Change the position of the moon and the Sun and note which phases of the Moon are visible in the daytime sky or evening sky.
    • Applet: Meridional Altitude Simulator - Change the latitude and note the altitude at which the north or south celestial pole can be viewed.
  • Use the FlashCards to test your memory for new terms.
  • Review the Excursion Box for this chapter:
    • 2.1 Where Are the Constellations?
  • Work the "Thinking about the Concepts" and "Applying the Concepts" questions in the end of chapter review materials.
  • If your instructor has assigned SmartWork online homework, login from the right navigation pane for additional practice and review.
  • If your instructor has assigned Math Tools, be sure to study Math Tools Box 2.1  How to Estimate the Size of Earth

Connect

  • Periodic Connections boxes and the Seeing the Forest through the Trees section at the chapter's end draw your attention to recurring themes and help prepare you for concepts explored more fully in subsequent chapters.
  • Visit Astronomy in the News for breaking news of new discoveries and the opportunity to apply what you've learned in this chapter to real-world (and real Universe) events.
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