48. WHERE ON THE WORLD ARE WE

SUBJECT: Science
GRADE: 7,8,9
GROUP SIZE: Large
TIME: 50 minutes
TYPE OF ACTIVITY: Construction Skill Development
TEACHING STRATEGY: Expository Guided Discovery
CONCEPTS: Latitude Pointer Stars Inclination
SKILLS: Construction Following Directions Recording Data
Objectives: To learn a method of determining the latitude of your location on the Earth; to learn a method of locating the North Star.

latitude measurement setup illustration

Materials: For each student or group of students: 1 drinking straw; protractor; piece of thread; washer or other weight; cellophane tape; magnetic compass.
Procedure:

  1. Tape the straw to the base of the protractor as shown in the drawing.
  2. Attach the thread to the center of the base of the protractor and attach the washer to the other end.
  3. Teach the students the following technique to locate the North Star. First, locate the Big Dipper (use a compass to locate the general direction of north if needed). Next, follow an imaginary line from the two stars which form the front of the Dipper (see illustration). The first star you come to in line with the “pointer” stars is the North Star.
  4. Point the straw/protractor sighting device at the North Star.
  5. Let the thread hang loose until it stops moving.
  6. Hold the thread tight against the protractor and read the degrees.
  7. Repeat the observation at least three times and record the readings. (Use the conversion table shown or subtract the readings on the protractor from 90 to arrive at the proper latitude angle.)
  8. Have the students take their devices home and take readings which they will bring back to class the next day.
  9. Average the readings from the class. This should be a close approximation of the actual latitude of your area.

Extension: Use the angle of latitude to construct a sundial. The angle is the same as the angle of the gnoman on a sundial for your area.
CONVERSION TABLE

Reading from
Protractor
Degrees of
Latitude
105 15
110 20
115 25
120 30
125 35
130 40
135 45
140 50
145 55
150 60
155 65
160 70
165 75

Each degree of angle on the protractor is one degree of latitude.

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