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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
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.)
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
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.
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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