Noon Day Project Background Info
Purpose: To recreate the remarkable measurement of the circumference of the earth that was done over 2000 years ago. Using only simple tools such as rulers, protractors, and meter sticks, students will measure shadows cast by a meter stick at different locations on the earth.
Subjects: Mathematics (geometry, ratios, scale drawing, measurement, introduction to trigonometry (optional)), science, social studies, geography & history.
Grade Level: Grades 5-12
Summary: Over 2,000 years ago Eratosthenes made a remarkably accurate measurement of the earth's circumference. This project requires collaboration of students in places at different latitudes of the earth to make some simple measurements, share data, use a spreadsheet to make comparisons, and then replicate and share their results. Here is a summary of the steps involved in making the measurements:
At least two sites must collaborate whose latitudes (north-south distance) are different enough to give a significant difference in measurements.
On the given date [or within a day or two] students will conduct their measurements outdoor at high noon, local time. It is important that each site knows ahead of time that "local noon" is NOT 12:00 Noon; it is the time when the sun is at it's highest altitude in the sky that day. I use NOAA Sunrise-Sunset Calculator to determine my local (sun) noon.
Using a standard meter stick each team of students will:
This length of the shadow at local high noon and the date on which the measurement is taken will be posted on the Web at Daryl Taylor's GHS Website.
This data along with the latitude for each site is enough information to use a simple proportion to make a fairly accurate calculation of the Earth's circumference as determined by each pair of sites.
- Lay out a piece of paper flat on the ground.
- Hold the meter stick perfectly vertical. (It may be taped to a metal book end, set in sand inside a liter plastic bottle, etc.)
- Mark on the paper the end of the shadow at one minute intervals over a ten to twenty minute period.
- Several measurements should be made by several different students or teams of students the more the better.
- Measure the length of the shadow cast by the meter stick to the nearest centimeter and these measurements will then be analyzed by the students.
- Using statistical computations the class should arrive at what they feel is the length of the shadow cast at local noon (which should be the time of the shortest shadow).
Number of participants: Unlimited