Cartesian diver

A Cartesian diver (also: Cartesian diver Cartesian dance devil, devil bottles, water devil or rotary devil), is a fluid-filled and air- hollow body, which can serve as a toy or as a gauge for the pressure in liquids. The name is derived from René Descartes, Latinized Descartes. He was reportedly developed in 1640 by René Descartes, but actually invented by Raffaello Magiotti and first described in 1648.

Function

The figure has a cavity via an unsealed opening to the outside. This cavity is filled with water so far that the lift is just sufficient that he does not go down, so do just stops at the water surface. So it is set in a possible complete bottle filled with water which is closed, for example, with a flexible Gummihut. By pressing on the cap increases the pressure in the interior of the bottle. This pressure is transmitted through the water on the diver and in it contained volume of air is compressed it. Due to the incompressibility of water, the volume change corresponds to the closure practically completely the change in volume of the air in the diver.

By increasing the pressure of the trapped air is compressed in the body, so its volume decreases, and thus attributable to them buoyancy, while the weight of the enclosed air and the weight of the figure remain the same. Previously, if the amount of lift exceeds the amount of the weight of the combination figured air tight, this is now reversed and the buoyancy is compared with the weight less. This results in a downward force and the figure together with the air content decreases. Conversely, by releasing the closure from the pressure and thus the volume of air can be recycled. It extends with displacement of some water from which the volume and thus the buoyancy larger again - the figure rises again.

With a little practice can be the Cartesian diver keep in abeyance. A submarine corresponds to a Cartesian diver who is in unstable equilibrium.

Toys

Ready to buying Cartesian divers are made of blown glass, with a length of about 3 cm. At the lower end ( usually at the "tail" of the devil ) is a small hole, the diver is placed in a water-filled plastic bottle. You now closes the bottle, the diver swims above. Pressing on the bottle, the diver sinks to the bottom.

A very simple Cartesian diver can be from one to the balls shaped piece of aluminum foil to produce ( so large that it will fit through a bottle neck). You may have to play around a bit and press them together or pull apart until the Alubällchen has the right density the material. When divers are also many other items that contain air and liquid, such as ink cartridges, cooking oil bottles or plastic packets of ketchup or mustard, as well as match heads or pieces of fresh orange peel (as long as it trapped gas bubbles are not yet bubbling ).

Wherein the glass Cartesian diver with spiral water inlet and outlet into the outflow of the compressed water causes a rotational movement about the body axis of the Cartesian diver, the diver rises to the surface of rotation.