A new twist for the great classic science project.
Cartesian divers were first noted by a student of Galileo Galilee! Some people back in those days thought its mysterious dives and ascents in the water smacked of dark magic, as witnessed by the name it was sometimes called: Devil's Diver. The advent of clear plastic bottles made Cartesian divers popular in school science classes, as well they should be. What a cool way to learn about density, buoyancy, compression of gases, etc.
Unfortunately, some diver designs are either too expensive for large groups, or they hide what's going on inside the diver. For example, pen caps and modeling clay are cheap enough for everyone to make, but you can't see the air compressing and the water rushing in. Using clear eye droppers costs at least a dollar each. Not bad if you're just making one at home, but quite a bit of money if you are making them with a large group. I offer a design to fill the void, plus some variations.
In the instructional videos above, (on YouTube: Part 1 , Part 2 ) I've included scenes of groups of kids actually making Cartesian divers as well as an educational diversion: a visit to a scuba diving shop with some under water video footage.
Here you can read more about how Cartesian divers work.
Many thanks to the West Branch School, YMCA after school program and Sunken Treasure diving shop.