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Chapter 18

Chapter 18: Our Expanding Universe

Study Plan

Just as stars make up the structure of our own galaxy, so too are galaxies the building blocks of the structure of the universe. Observations of the motions of galaxies led to one of the most remarkable discoveries in the history of our species: the universe is expanding! As we investigate this discovery we will learn

  • That the universe contains hundreds of billions of galaxies.
  • That the cosmological principle predicts isotropy and homogeneity of the observed distribution and velocity of galaxies.
  • About the discovery of Hubble's Law, which relates the redshift of a galaxy to its distance.
  • How Hubble's Law is used to map the universe in space and to look back in time.
  • That galaxies are not flying apart through space, but rather "ride along" as space itself expands in accordance with the general theory of relativity.
  • That spacetime itself was born approximately 13.7 billion years ago in an event called the Big Bang.
  • That each of the major predictions of the Big Bang theory, from the glow of the cosmic background radiation to the types of atoms that fill the universe, is confirmed by observation.
  • What observations of the cosmic background tell us about the properties of the young universe.

Organize

  • Read Chapter 18 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.
  • 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.
  • If your instructor has assigned Math Tools, be sure to study Math Tools Box 18.1, Redshift: Calculating the Recession Velocity and Distance of Galaxies, and Math Tools 18.2, Expansion and the Age of the Universe.

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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