Newton's law of universal gravitation is simplicity itself. As we saw in Chapter 3, it helps explain Kepler's laws of planetary motion. Yet when applied to extended rather than pointlike masses or when acting among three or more objects, this simple rule gives rise to a surprising diversity of phenomena. In this chapter we apply Newton's law beyond Kepler's elegant laws of planetary motion and discover

• How symmetry enables us to say a great deal about the gravity of an object without actually calculating anything.
• That the gravity within a spherical object is determined only by the mass within a given radius.
• That tides on Earth resulting from the fact that gravity from the Moon and Sun pull harder on one side of Earth than the other.
• Tidal interactions between planets and moons (including Earth's Moon) that lock a moon's rotation to its orbit.
• Comets that have been shattered by tidal stresses, and tortured moons alive with tide-powered volcanism.
• Orbital resonances that nudge asteroids from their orbits and sweep out gaps in planetary rings.

Organize

• Read Chapter 10 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.
  • Tides and the Moon Section: 10.2, 10.3
• Access the applets for this chapter.  Be sure to try different parameters with the applets to make sure you understand the concepts.
  • Tidal Bulge Simulator - Earth's rotation is included as well as what changes are due to the Sun's gravity.
• Use the FlashCards to test your memory for new terms.
• 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.
• Connections 10.1, Lunar Tides and Life; 10.2, Earth, the Moon, and Conservation of Angular Momentum; and 10.3, Tides on Many Scales; will help connect the principles in this chapter with topics to come later.

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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