Well-Timed Lessons

From Ice Age inhabitants who scratched lines to keep track of moon phases to devices set to the millisecond today, humans have always tried to answer the question, "What time is it?" The Web offers great ways to explore the history, variations, and concepts of measuring time. Your class can take a "walk through time" to learn how the Sumerians devised their calendar 5,000 years ago or look at drawings of early water clocks. When the ancient Mayans calculated the days of their calendar, they used the planet Venus as well as the sun and the moon. Today, your students can use the Web to find out the corresponding Mayan calendar date for any dates between 1902 and 1999.

A more modern invention is the concept of time zones. You can explain to your students about different time zones around the world, and then show them The World Clock, which displays up-to-the-minute time in 100 cities worldwide. If you want to find the definitive answer to the question, "What time is it?" consult the U.S. Naval Observatory's Time Service Department, the official source of time used in the United States, and a fantastic resource about time measurement. Just as the ancients looked at the sun and the moon to gauge the passing of time, your students can also. They can compute the sun and moonrise in your area on various days, courtesy of the U.S. Naval Observatory's calculator.

A Walk Through Time
http://physics.nist.gov
/GenInt/Time/time.html

Welcome to Rabbit in the Moon
http://www.halfmoon.org/

The World Clock
http://www.timeanddate.com
/worldclock/

Time Service Dept., U.S. Naval Observatory
http://tycho.usno.navy.mil/