Measuring Time, for 5th and 6th graders, covers the history of measuring time and the evolution of timekeeping. And although we’ve become used to having clocks help us structure our lives, accurate clocks are new inventions, the result of the need for sailors to be able to know where they were at sea. Looking backward in time, the book tells how geologists can tell the age of landforms such as the Grand Canyon and from that can determine the ages of other places as well. Other stories show how nature’s creatures' lives are regulated though internal “clocks." Before the microscope was invented in the 1500s, people were unaware of the tiny world of microorganisms that exists all around us—and inside of us.

(ISBN 1-978-933008-09-7)

• Available for order at http://www.nap.edu/catalog/nsrc/index.html.
• Information about the Measuring Time STC unit
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