Cartesian diver

JW Player goes here

There is an eye dropper in a plastic bottle of water. The eye dropper is weighed in such a way that it is suspended with the opening directed to the bottom. There is some air trapped in the dropper.

If you squeeze the bottle, the pressure inside increases and, consequently the air pressure in the eye dropper also rises. If you examine closely, you will observe that the air bubble in the eye dropper gets smaller when you squeeze the bottle. This means that the diver's buoyancy has decreased as more water got inside. Unfortunately, the diver has drowned.

Modern bathyscaphs are equipped with floats filled with light petrol and not with air. If they were filled with easily compressible air they would behave like the Cartesian diver and hence would be useless. In order to construct your own Cartesian diver you need an old cork, a few small nails and an orangeade bottle. Good luck!