A great science project from RMIT (via Roland Gesthuizen):
RMIT University is coordinating a national schools project inviting teachers and students from Years 10, 11 and 12 to re-enact Eratosthenes' famous experiment in measuring the angle of the Sun at local noon to determine the radius of the Earth. The students and teachers will make their measurements during National Science Week from 16 to 24 August 2008 ...I was thinking of some preliminary activities, accessible to younger kids, to introduce greek maths / science to start with including some nocturnal activities
Each registering school will be paired with another school which has as close as possible to the same longitude and as large as possible latitude difference. The two schools will share measurements of the angle to the local-noon Sun to determine the radius of the Earth
Eratosthenes Project - Australia
eg. holding a ruler at arms length to measure the diameter of the moon, then using similar triangles to estimate the ratio b/w the moons diameter and distance of the moon from the earth (or using a coin if you have a partner to help)
which also happens to be the same as the ratio b/w the suns diameter and the distance of the sun from the earth (since the sun is exactly covered by the moon during an eclipse)
This could be simulated on the computer. Alan Kay posted a project like this on the squeak list last year but I couldn't find it when I went back to look.
more info here: