In ancient times many natural phenomena were explained by weaving myths about what was observed. As time passed, more practical applications were based on observations, such as using stars as points of reference when traveling. The Greeks were noted for applications of geometric measurement that were amazingly accurate in describing the size and motion of the Earth and other planets. In this project, you will calculate the circumference and radius of a circle using the geometric method Eratosthenes used to determine the circumference and radius of the Earth. You will learn how to calculate the angle of a shadow. Following Eratosthenes' example of using the difference in the angle of shadows cast in different cities at the same hour, you will determine the circumference of the Earth for yourself. You will learn how a lunar eclipse was used to verify the shape of the Earth.
You Will Need :
- Roll of masking tape
- Scissors
- Sheet of typing paper
- Pen
- Metric ruler
- Protractor
Process :
Lay the roll of tape flat in the center of the paper and trace around it with the pen. Find the center of the circle drawn on the paper by folding the circle in half twice: first fold the circle from top to bottom, then fold again from side to side. Unfold the paper and mark a point in the center where the fold lines cross. Label this point A. Lay the ruler across the circle with its bottom edge on the horizontal fold line. Mark two points on the circumference of the circle where the top and bottom edges of the ruler touch the one side of the circle. Label the points B and C, as shown in Figure 8.1. Use the ruler to draw a line from point A to each of the points B and C. Extend the lines 5 cm or more outside the perimeter of the circle to points D and F (see Figure 8.1). From points B and D, draw lines perpendicular to the circle and parallel to line FC. Mark point E as shown. Use the protractor to measure the angles between angle CAB and EBD (see Figure 8.1).
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