Latitude and longitude are the two grid coordinates by which you can locate any point on Earth. Latitude is measured in terms of degrees north and south from the Equator. (Any point on the Equator has a latitude of 0°). A student can roughly compute his/her latitude by pointing one arm at the North Star and the other at the horizon. The number of degrees between the two arms is the latitude (in Maine around 45°). The distance between two degrees of latitudes is about 60 nautical miles.

Lines of longitude run north to south along the surface of the Earth, dividing the globe into 360 equal slices. Most countries count longitude in degrees east and west of an imaginary line running through Greenwich, England, at 0° longitude. (Portland, Maine is about 70° west longitude.) The space between the lines of longitude (meridians) is greatest at the Equator-- about 69 miles. As you approach the poles, the distance between meridians decreases. Lines of longitude converge at the North and South Poles.

X Marks the Spot

  1. Divide the class into pairs. If there is an odd number of students, pair one with the teacher.
  2. Assuming that the stems of the orange are the North and South Poles, have the students draw a line representing the Equator (line of latitude) around the middle of the orange.
  3. Ask the students to draw a line of longitude around the orange through both the North and South Poles.
  4. On one side of the orange, label the intersection of the Equator and the longitude line as "0."
  5. Ask one student from each pair to mark an X on his/her orange, but not to let his partner see where the X is.
  6. Have the student describe to his/her partner where the X is located on the orange without showing it to him/her.
  7. The partner must attempt to mark his/her own orange in the same spot as his partner's X.
  8. How accurate were their guesses? Students had only the Equator, one line of longitude, and the poles for reference points.
    What would be required to increase accuracy? (more lines of longitude and latitude).
  9. Let students enjoy their snacks!

Materials

  • one orange per student
  • marker (preferably fine point)