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7
PENNSVALLEY
Lesson 3:
Earth’s Time Zones and
the International Date Line
Part A –Time Zones
Now thatweknowwhere theEasternHemisphere is,wecanexploreother issues inamore “timely”
manner. Time can be a very confusing concept, so we will try to take up as little of your time as
possible.Have youever had “timeon your hands?”Wehavebeenaskedby youngsterswhywe cannot
have the same time all over the earth?We suppose you could, but it surewouldmake the daily tasks
of life harder to complete.
ACTIVITY 1:
If wewould have the same time all over the earth, what problemswould you havemanaging your life?
Write and describe the problems.
1.
2.
3.
The fact is we do not have the same time all over the earth. Besides helping us locate places on
earth, lines of longitude, or meridians, serve the purpose of setting up time zones. Lines of longitude
provide us with our time zones. Let’s review this idea by the numbers.
1.There are 360° in a sphere.
2. Each time zone is divided into 15°.
3. It takes the sun’s rays about one hour to cross 15° of the rotating earth.
4.Divide 15 into 360, or 360 .The answer is
hours.
15
5. Your answer equals the number of time zones we have on earth.Your answer also represents
the number of hours in one earth day.
ACTIVITY 2:
The earth rotates on its axis fromwest to east.Thismovement means that during daylight hours, the
sun’s rays travel across the earth from east towest.You can easily demonstrate this by using aCD or
DVD disc.
A.Move the disc (represents the earth) fromwest to east ( ). Hold a small light source above
the disc.You can see the light raysmove from east towest (
) as thediscmoveswest toeast.
B.Draw a labeled diagram of this activity below:
Geography Skills
