Diameter of the Earth
In this project you will use the method that Eratosthenes used to measure the Earth.
You will need to accurately measure the length of the shadow cast by two sticks that are several hundred miles north and south of each other on (or about) the same day.
Make the measurements at local noon (when the sun is directly overhead). You can do this by looking in the local paper for the time of sunrise and sunset - local noon is half way between these times.
Be sure that the stick is vertical. Record both the length of the stick and the length of the shadow.
You can measure the angle of the Sun by either making a scale model of the stick and shadow and measuring the angle with a protractor or by using trigonometry.
angle N - angle S = the angular separation of the two points on the Earth.
You can set up the following ratios:
Solving for Earth’s circumference gives:
You can now find the Earth’s diameter by using:
Write up a description of how you carried out this project and include the data that you collected and your calculations.
