I have written previously about determining the shape of the earth… for instance, here is a post on seeing the shape of the earth using eclipses. (A somewhat similar effect could be seen in my photo of the moon during a lunar eclipse). On the web, I found another way of computing the shape of the earth through studying the turbulent wake of a ship. And then there was the post about reconciling the shape of the earth with the maps or projections we typically use (such as the mercator projection).
I was thus glad to find the following video: Top 10 reasons why we know the Earth is round