Chapter 21: The Origin of Structure

Study Plan

The universe that emerged from the Big Bang was incredibly uniform, wholly unlike today's universe of galaxies, stars, and planets. As our journey comes to its end, we tackle face-on the question that has been with us all along: Where does structure in the universe come from? Here we find that complex structure is a natural, unavoidable consequence of the action of physical law in an evolving universe:

  • Matter and the fundamental forces of nature "froze out" of the uniformity of the expanding and cooling universe moments after the Big Bang.
  • Galaxies formed as slight ripples in the dark matter emerging from the Big Bang, which then collapsed under the force of gravity, pulling in normal matter as well.
  • Galaxies were drawn together by gravity to form the large groupings of galaxies we see today.
  • Much lies ahead for Earth and for the universe.
  • Like planets, stars, and galaxies, life is another form of structure that evolved through the action of the physical processes that shape the universe —the universe may teem with life.
  • Evolution of structure through the action of physical law is the lynchpin that ties all of modern science together and brings sense to what we see.

Organize

  1. Read Chapter 21 in your textbook or ebook.
  2. Take the Diagnostic Quiz to assess your understanding of the basic concepts and identify gaps in your understanding of the assigned reading.

Learn

  1. Use the FlashCards to test your memory for new terms.
  2. Review Excursions Box 21.1: Forever in a Day.
  3. Work the "Thinking about the Concepts" and "Applying the Concepts" questions in the end of chapter review materials.
  4. If your instructor has assigned SmartWork online homework, login from the right navigation pane for additional practice and review.

Connect

  1. 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.
  2. 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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