Footnotes for Unit 1 - Many Planets, One Earth

  1. American Museum of Natural History, "Our Dynamic Planet: Rock Around the Clock," http://www.amnh.org/education/resources/rfl/web/earthmag/peek/pages/clock.htm.
  2. Peter D. Ward and Donald Brownlee, Rare Earth: Why Complex Life Is Uncommon in the Universe (New York: Springer-Verlag, 2000).
  3. U.S. Geological Survey, "Radiometric Time Scale," http://pubs.usgs.gov/gip/geotime/radiometric.html, and "The Age of the Earth," http://geology.wr.usgs.gov/parks/gtime/ageofearth.html.
  4. Paul F. Hoffman and Daniel P. Schrag, "Snowball Earth," Scientific American, January 2000, pp. 68–75.
  5. Andrew Knoll, Life on a Young Planet: The First Three Billion Years of Evolution on Earth (Princeton University Press, 2003), p. 23.
  6. University of California Museum of Paleontology, "Cyanobacteria: Fossil Record," http://www.ucmp.berkeley.edu/bacteria/cyanofr.html.
  7. Knoll, Life on a Young Planet, p. 42.
  8. "Did the Snowball Earth Kick-Start Complex Life?", http://www.snowballearth.org/kick-start.html.
  9. Stephen Jay Gould, Wonderful Life: The Burgess Shale and the Nature of History (New York: Norton, 1990).

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