The basic concept of time is really based upon two very specific
movements of the Earth: its rotation on its axis, and its
revolution, or orbit, around the sun. Astronomers stationed at
the observatory at Greenwich, England, set the world's atomic
clock by the noonday sun. When the sun has reached its zenith --
or, as it is sometimes known, the sun's meridian -- it is
exactly noon. Ancient navigators, however, found it very
difficult to know their exact location once they were out of
sight of land. It was not until 1714 that a clockmaker, John
Harrison, came to realize that exact time away from the home
port could be calculated using the measurement of longitude with
a starting point of the Prime Meridian. From that, ship's
captains could determine their exact location at sea. This
lesson, supported by hands-on activities, video, and Internet
connections will examine our reliance on latitude and longitude,
not only to give us our location on maps, but our connection to
time and time zones. Students will explo