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Spring Equinox 2013: Measuring the size of the Earth

At noon on spring equinox day 2013 (20 March, 13.00 local time) the Sun is directly over the Earth's equator.
So, we put Eratosthenes' ideas into action!

Firstly we looked for an even area in our schoolyard. Then, we measured the length of a metal rod.

measuring the size of the earth_1


measuring the size of the earth_2

Afterwards the rod was placed vertical to the ground and the length of its shadow was measured.
The day was cloudy and it was difficult to discern the shadows cast by objects,
but after some debate the issue was settled and the measurement was made.

measuring the size of the earth_3


measuring the size of the earth_4

The data were plugged into Eratosthenes' geometrical model and immediately the geographical latitude of our school was estimated.
The accuracy of the result was astonishing (0.01% error)!

Using software like Google Earth we obtained the distance from our schoolyard to the Earth's equator estimated the Earth's perimeter and radius,
as described in the students' report. Again, the result was very accurate (error 0.5%)!

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