- Resource Type
- Engineering Physics
- Scientific Inquiry
- Time for activity
- 30 Minutes
If you press the bottle with your hands, water is pressed into the diver, buoyancy is reduced, the diver sinks to the bottom and vice versa.
Cartesian divers are named after the French philosopher, mathematician and scientist Rene Descartes. In the floating diver, besides water, there is also some air. By pressing on the bottle, the pressure inside the bottle increases. Since water cannot be compressed, this pressure is transmitted through the water to the diver and the air enclosed in him, which is thus compressed. Its volume is reduced and water can penetrate. As a result, the diver’s weight increases and he begins to sink.
If the pressure on the cylinder is reduced, the pressure on the water also decreases, the air in the diver expands again, displaces the water that has previously flowed in again, and the buoyancy is sufficient to allow the diver, who is now lighter again, to rise to the surface. With a little practice, the Cartesian diver can also be kept in suspension. This principle is also used for drift buoys in marine research or smaller science submarines.