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Origins: Earth is Born
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Viewing Ideas
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Origins: How Life Began Viewing Ideas
Origins: Where are the Aliens? Viewing Ideas
Origins: Back to the Beginning Viewing Ideas
Before Watching
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The universe is about 14 billion years old, while Earth is
estimated to be about 4.6 billion years old. Homo sapiens
evolved about 600,000 years ago. Have students calculate the
length of a time line that would show all these events if
500,000 years were represented by one centimeter (About 280
meters). Where would Earth's formation fall on the time line?
(About 92 meters.) The appearance of Homo sapiens? (About 1.2
centimeters.)
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Organize students into three groups. Assign each group to take
notes on one of the following concepts as they watch: Earth's
formation, the moon's formation, and how Earth came to have
water.
After Watching
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Explain what differentiates a fact (an observation that has been
repeatedly confirmed), a hypothesis (a testable statement about
an aspect of the natural world), and a theory (a well-confirmed
explanation of an aspect of the natural world—a theory can
incorporate both facts and tested hypotheses). Discuss these
three concepts considering the notes students took regarding how
Earth and the moon formed and how Earth became a watery planet.
What were facts? What were hypotheses? Theories? Have students
support their reasoning.
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By applying radiometric dating to meteorites, scientists have
estimated Earth's age to be about 4.6 billion years. Have
students research the process of radiometric dating. How many
different isotopes can be used for radiometric dating? Why are
some isotopes used instead of others? Find more information at
pubs.usgs.gov/gip/geotime/radiometric.html
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