Just spent 90 minutes not doing what I should have been doing because I had some very interested schoolkids visiting the lab. Loved it!

christoph: sympathize strongly! once had a project with schoolkids (~12 y) and we wanted to find proof that our earth is not flat but spherical. A suggestion: tie your boat to the harbor pier with a long thin line and set off. If the line stays above water, the earth is flat. otherwise it's not.